The Laurencia complex (Rhodophyta, Rhodomelaceae) in the Mediterranean Sea: an overview

Cryptogamie, Algol., 2001, 22 (4): 331-373 © 2001 Adac/~xlitions scientifiques et m6dicales Elsevier SAS. Tous droits r6serv6s S0181156801010650/FLA

INVITED REVIEW 5

The Laurencia complex (Rhodophyta, Rhodomelaceae) in the Mediterranean Sea: an overview 1

Giovanni FURNARI*, Mario CORMACI & Donatella SERIO

Dipartimento di Botanica dell'Universitfi di Catania, Via A. Longo, 19, 95125 Catania, Italy

(Received 16 July 2000, accepted 12 January 2001)

Persons wishing to contr ibute to the Invi ted review Series should contact the Editor in the first instance. Al l Invi ted Reviews are refereed in the same manne r as other manuscripts .

Previous Review

ROUSSEAU E & REVIERS B. de 1999 - - Circumscription of the order Ectocarpales (Phaeo- phyceae): bibliographical synthesis and molecular evidence. Cryptogamie, Algologie 20 (1): 5-18.

MORCOM N.E & WOELKERLING Wm J., 2000 - - A critical interpretation of coralline-coralline (Corallinales, Rhodophyta) and coralline-other 'plants' interactions. Cryptogamie, Algologie 21 (l): 1-31.

RIOSMENA-RODRIGUEZ R. & WOELKERLING Wm J., 2 0 0 0 - Taxonomic biodiversity of corallinales (Rhodophyta) in the Gulf of California, Mexico: towards an initial assessment. Cryptogamie, Algologie 21 (4): 1-31.

RUSIG A.M., OUICHO A., LE GUYADER H. & DUCREUX G., 2001 - - Ontogenesis in the Fucophyceae: case studies and comparison of fucoid zygotes and Sphacelaria apical cells. Cryptogamie, Algologie 22 (3): 227-248.

This paper is dedicated to Ren6 De16pine on the occasion of his retirement. * Correspondence and reprints: [email protected]

332 G. Furnari, M. Cormaci & D. Serio

Abs t rac t - -Recen t taxonomic studies of the genus Laurencia sensu lato (Ceramiales, Rhodomelaceae) have resulted in the recognition of three genera within the 'Laurencia complex': Laurencia sensu stricto, Chondrophycus and Osmundea. A critical examination of all Mediterranean records of taxa referred to Laurencia has shown that three species of Chondrophycus, six species of Osmundea and nine species of Laurencia are present. These taxa are described and illustrated. Laurencia caduciramulosa and L. intricata are reported for the first time from the Mediterranean Sea and from Italy, respectively. A key to the Mediterranean species of the Laurencia complex is given. © 2001 Adac/Editions scientifiques et mrdicales Elsevier SAS

Ceramiales / Chondrophycus / Laurencia I marine algae / Mediterranean Sea / Osmundea / Rhodomelaceae / Rhodophyta / taxonomy

Rrsum6 - - Les 6tudes taxinomiques rrcentes du genre Laurencia sensu lato (Ceramiales, Rhodo- melaceae) ont permis de reconnaitre trois genres dans le 'complexe Laurencia' : Laurencia sensu stricto, Chondrophycus et Osmundea. Un examen critique de toutes les mentions de taxons rapportrs au genre Laurencia sensu lato en Mrditerranre a permis de montrer que trois esp~ces de Chondrophycus, six esp~ces d'Osmundea et neuf esp~ces de Laurencia sont prrsentes. Ces taxons sont drcrits et illustrrs. La prrsence de Laurencia caduciramulosa est mentionnre pour la premiere fois en Mrditerran6e et celle de L. intricata en Italie. Une clef des esp~ces mrditerranrennes du complexe Laurencia est prrsentre. (Traduit par la Rrdaction) © 2001 Adac/Editions scientifiques et mrdicales Elsevier SAS

algues marines / Ceramiales / Chondrophycus / Laurencia / mer M~diterran~e / Osmundea / Rhodomelaceae / Rhodophyta / taxinomie

I N T R O D U C T I O N

To date, 81 specific and infraspecific taxa referred to the genus Laurencia have been recorded from the Mediterranean Sea. Of these, nine belong to the genus Chondria, 33 are taxa inquirenda (taxa whose taxonomic status is uncertain in absence of the examination of relative type materials), four are nomina nuda and three are taxa excludenda (Tab. 1). Following the numerous taxonomic studies on the genus Laurencia which resulted in the distinction of three genera [Chondrophycus (Tokida et Saito) Garbary et J. Harper, Laurencia J.V. Lamouroux and Osmundea Stackhouse] (see the historical background below), only three species of Chondrophycus, six species of Osmundea and nine species of Laurencia are accepted to occur in the Mediterranean Sea. In this paper, the accepted taxa are briefly described (Chondrophycus spp. by M. Cormaci and G. Furnari; Laurencia spp. by G. Furnari, and Osmundea spp. by D. Serio and G. Furnari) on the basis of both literature data and personal observations carried on Mediterranean specimens (mainly from the Italian coast). Laurencia caduciramulosa and L. intricata, are recorded for the first time from the Mediterranean Sea and from Italy, respectively.

H I S T O R I C A L B A C K G R O U N D

The genus Laurencia was erected by Lamouroux (1813: 42) with the following eight species: L. pinnatifida (Hudson) J.V. Lamouroux (basionym: Fucus pinnatifidus

The Laurencia complex in the Mediterranean Sea 333

Hudson, 1762: 473), L. obtusa (Hudson) J.V. Lamouroux (basionym: Fucus obtusus Hudson, 1778: 586) [type species, designated by Schmitz (1889: 447)], L. gelatinosa J.V. Lamouroux [treated as nom novum since the intended basionym Fucus gelatinosus Desfontaines, 1799:427 is illegitimate being a later homonym of E gelatinosus Hudson, 1762:471 (see Silva et al., 1996: 516)], L. cyanosperma J.V. Lamouroux nomen nudum (Lamouroux didn't describe or illustrate this species, based on the undescribed species Fucus cyanospermus Delile, later published by Delile, 1813:196 pl. 57: 3), L. lutea J.V. Lamouroux nomen nudum (Lamouroux didn't describe or illustrate this species, based on the undescribed species Fucus luteus Boldoni), L. caespitosa J.V. Lamouroux nomen nudum (Lamouroux didn't describe or illustrate this species, based on the undescribed species Fucus caespitosus Weber et Mohr), L. intricata J.V. Lamouroux [the only species illustrated by Lamouroux in his paper (pl. 3, figs 8-9)] and L. versicolor J.V. Lamouroux (treated as nom novum since the intended basionym Fucus versicolor Vahl, 1802:44 is illegitimate being a later homonym of Fucus versicolor S.G. Gmelin, 1768: 159). The generic name was chosen by Lamouroux to honour his friend Mr de la Laurencie, an old navy official and lover of natural sciences. The original description of the genus given by Lamouroux (1813: 42) is very poor, and the only significant character included was the occurence of the 'fructification' (cystocarps) at the ends of both branches and branchlets.

For many years the taxonomy of the genus Laurencia was based on external morphology (Furnari & Serio, 1995). A first subdivision of the genus into sections was proposed by J. Agardh (1876). He recognised four sections (Filiformes, Papillosae, Obtusae, Pinnatifidae) distinguished mainly by external morphology. Falkenberg (1901) and Kylin (1923) provided detailed descriptions of reproductive structures in some species, but most authors have underestimated the importance of these characters in the taxonomy of the genus. Yamada (1931), in his monograph on this genus, emphasised mainly anatomical characters like, such as: the projection or not of epidermal cells near the ends of branchlets; the shape and arrangement of epidermal cells in transverse section; and the presence or absence of lenticular thickenings in the medullary cells. On this basis, he proposed a new infrageneric arrangement, recognising four sections: J. Agardh's section Pinnatifidae (including species with a clearly compressed frond and epidermal cells in transverse section, not palisade-like) and the following three new sections: Palisadae (including cylindrical species with palisade-like epidermal cells and without lenticular thickenings), Forsterianae (including cylindrical or slightly compressed species with epidermal cells not palisade-like and with abundant lenticular thickenings), Cartilagineae (including cylindrical or slightly compressed species with epidermal cells not palisade-like and with no lenticular thickenings).

The taxonomy of the genus has since undergone substantial revision with emphasis placed on characters such as the presence-absence of secondary pit connections between epidermal cells, the parallel or right angle arrangement of tetrasporangia (Saito, 1967); characteristics of spermatangial depressions ('indefinite', with no apical growing point at the base or 'definite', with an apical growing point at the base) (Saito, 1969); and the number of pericentral cells per axial segment (four or two) (Nam, 1990; Nam & Saito, 1990; Nam et al., 1991). Following the enhancement of such characters some infrageneric re-arrangements were proposed (Saito, 1967; Saito & Womersley, 1974; Zhang & Xia, 1985; Furnari & Serio, 1993a).

K.W. Nam & Saito (1994) described the occurrence in L. hybrida (De Candolle) Lenormand ex Duby of two peculiar reproductive characters: 1) the tetrasporangia arising from epidermal ceils with a lateral cut (arising from particular pericentral cells in other species of the genus); and 2) the apical and epidermal origin of spermatangial branches (from trichoblasts arising from axial cells in other species). Nam et al. (1994), found the above two characters in several species of Laurencia, including L. spectabilis Postels et

334 G. Fumari, M. Cormaci & D. Serio

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Ruprecht, L. crispa Hollenberg, L. splendens Hollenberg, L. blinksii Hollenberg et Abbott, L. multibulba Dawson, Neushul et Wildman, L. diegoensis Dawson, L. sinicola Setchell et Gardner, L. pinnatifida (Hudson) J.V. Lamouroux, L. truncata Kiitzing and L. pelagosae (Schiffner) Ercegovit. They concluded that such species occupy a phyloge- neticaUy different position from L. obtusa (the type species of Laurencia), and that therefore they should be ascribed to the resurrected genus Osmundea Stackhouse (1809) [type species Osmundea osmunda (S.G. Gmelin) K.W. Namet Maggs]. According to amendments proposed in that paper for both Laurencia and Osmundea, the two genera differ mainly in: 1) the origin of spermatangial branches [produced from trichoblasts in Laurencia ('trichoblast-type'), arising directly from apical and epidermal cells in Osmundea ('filament-type')]; and 2) the origin of tetrasporangia (produced from particular pericentral cells in Laurencia or from random epidermal cells in Osmundea).

Due to the above generic re-delineation, only two subgenera remained in the genus Laurencia: Laurencia and Chondrophycus Tokida & Saito. They were distinguished by Saito (1967) mainly on the basis of the following two criteria: the occurrence or not of secondary pit connections between epidermal cells, and the type of tetrasporangial arrangement. However, the occurrence of intermediate species between the two subgenera, such as L. botryoides (Turner) Gaillon, L. parvipapiUata Tseng, L. iridescens Wynne et Ballantine, L. similis K.W. Namet Saito, L. crustiformans McDermid and L. kangjaewonii K.W. Nam et Sohn, led K.W. Nam & Saito (1995) to suggest a critical revision of Saito's (1967) classification scheme. In that paper, K.W. Nam & Salto considered additional characters, such as, the number of pericentral cells, the presence- -absence of additional tetrasporangium-bearing pericentral cells, the position of pericentral cells bearing tetrasporangia and the number of pericentral cells of the procarp-bearing segment, and concluded that "a greater emphasis should be placed on vegetative axial features in separating the subgenera of Laurencia".

Garbary & Harper (1998) confirmed the distinction of Laurencia and Osmundea at generic rank, based on a cladistic analysis of a combination of both vegetative and reproductive characters of the Laurencia complex. They also proposed raising the subgenus Chondrophycus to generic rank [as Chondrophycus (Tokida et Saito) Garbary et J. Harper, type species: C. cartilagineus ('cartilaginea') (Yamada) Garbary et J. Harper] for species showing the following characters: two pericentral cells per axial segment; absence of corps en cerise; secondary pit connections between epidermal cells mostly absent; spermatangial branches produced from trichoblasts (of trichoblast-type); tetrasporangia developing from pericentral cells and with fertile branches producing additional fertile pericentral cells; and right angle arrangement of tetrasporangia.

Finally, K.W. Nam (1999) recognised the three genera (Laurencia, Osmundea, Chondrophycus) as distinct, but observed that the combination of characters proposed by Garbary & Harper (1998) did not allow an unequivocal generic placement of species. He proposed that the genera be circumscribed based on the following characters: 1) the number of pericentral cells in vegetative axial filaments; 2) the type of spermatangial development; and 3) the origin of tetrasporangia. On this basis, the genus Osmundea is characterised by the following combination of characters: two pericentral cells in vegetative axial filaments, spermatangial development of filament-type, and tetrasporangia produced from random epidermal cells; the genus Laurencia by: four pericentral cells in vegetative axial filaments, spermatangial development of trichoblast-type, and tetrasporangia produced from particular pericentral cells; and the genus Chondrophycus by: two pericentral cells in vegetative axial filaments, spermatangial development of trichoblast-type, and tetrasporangia produced from particular pericentral cells.

K.W. Nam (1999) also proposed an infrageneric subdivision of the genus Chondrophycus based on combinations of the following characters: 1) presence or


absence of secondary pit connections between epidermal cells, 2) tetrasporangia produced only from additional pericentral cells or produced from both the second and additional pericentral cells or only from the former, 3) right angle or parallel arrangement of tetrasporangia. The following four subgenera were distinguished: Chondrophycus (no secondary pit connections between epidermal cells, tetrasporangia produced only from additional pericentral cells, right angle arrangement of tetrasporangia), Kangjaewonia K.W. Nam (no secondary pit connections between epidermal cells, tetrasporangia produced only from additional pericentral cells, parallel arrangement of tetrasporangia), Palisadi ('Palisada') (Yamada) K.W. Nam (no secondary pit connections between epidermal cells, tetrasporangia produced from both the second and additional pericentral cells or only from the former, right angle arrangement of tetrasporangia), Yuzurua K.W. Nam (with secondary pit connections between epidermal cells, tetrasporangia produced from both the second and additional pericentral cells or only from the former, right angle arrangement of tetrasporangia). Moreover, within the subgenus Palisadi the section Palisadi ('Palisadae') and the section Papillosi ('Papillosae') J. Agardh emend. K.W. Nam, with palisade-like and without palisade-like arrangement of epidermal cells, respectively; and within the subgenus Yuzurua the section Yuzurua and the section Parvipapillati ('ParvipapiUatae') K.W. Nam, with epidermal cells near branchlet apex lacking projecting walls and with projecting walls respectively, were also proposed.

It should be noted that, in Nam's (1999) circumscription of the above three genera, the presence or absence of corps en cerise wasn't considered as a diacritic character at generic level, as made by Garbary & Harper (1998). In fact, such intracellular inclusions occur only in some species of Laurencia and to date, their presence or absence and their number have a valuable taxonomic meaning only at specific level within that genus. But, as stated by McDermid (1988), and later also by Masuda et al. (1997a), their taxonomic usefulness remains limited since they can be detected only in living specimens.

MATERIALS AND METHODS

Sterile thalli of Laurencia caduciramulosa were collected at Lachea Island (Ionian Sea, Sicily) and at Linosa Island (Straits of Sicily) on 23.x.91 and 30.ix.98, respectively, epilithic in the lower intertidal zone. Both female gametophytic and tetrasporangial thalli of L. intricata were collected at Pantelleria Island (the Straits of Sicily) on 27.v.1996 at a depth of 0.5 m; sterile thalli (reported as Laurencia sp. 1 by Cormaci et al., 2000) were collected at the Tremiti Islands (Adriatic Sea) on 3.x. 1998 at a depth of 0.2 m. Observations on all species (Laurencia epiphylla and Osmundea pinnatifida excepted) were made on fluid-preserved material. Herbarium specimens are held at CAT (the Herbarium of the Department of Botany of the University of Catania). Studies were carried out on material preserved in 4 % formaldehyde-seawater. For microscopic observations, some specimens were stained with 1% aqueous aniline blue acidified with dilute HC1, which enhances pit connections.

With 'specimens examined' we refer only to the material studied in the present study to give descriptions and illustrations of species treated. For the list of all other specimens studied by authors in previous studies on species of the Laurencia complex (including type materials) see the following papers: for Chondrophycus paniculatus (C. Agardh) G. Furnari and C. patentirameus ('patentiramea') (Montagne) K.W. Nam, Boisset et al. (2000); for Laurencia chondrioides BCrgesen, Boisset et al. (1998); for Osmundea pelagosae (Schiffner) K.W. Nam, Furnari & Serio (1993a); for O. truncata (Ktitzing) K.W. Nam et Maggs, Fumari & Serio (1993b); for O. verlaquei G. Furnari, Cormaci et al. (1994).


MEDITERRANEAN TAXA OF THE LAURENCIA COMPLEX

Chondrophycus paniculatus (C. Agardh) G. Furnari in Boisset et al. (2000, figs 18-23) (Figs 1-3)

Note added in proof

Chondrophycus thuyoides (Kiitzing) G. Furnari comb. nov.

When Fumari in Boisset et al. (2000: 393) proposed the combination C. paniculatus (C. Agardh) G. Fumari, based on Chondria obtusa vat. paniculata C. Agardh 1822, quoted among synonyms Laurencia thuyoides Ktitzing 1865. That makes such a combination illegitimate, since according to Art. 11.2 of ICBN (Greuter et al., 2000) Chondria obtusa vat. paniculata C. Agradh doesn't have priority outside its rank. Thus the proposal of the following new combination has become necessary : Chondrophycus thuyoides (Ktitzing) G. Furnari comb. nov. Basionym: Laurencia thuyoides Ktitzing 1865 Tabulae Phycologicae 15: 26. Holotype: L-9 995-1 (Rijkshembarium, Leiden). Type locality: New Caledonia. Heterotypic synonyms: Chondria obtusa var. paniculata C. Agardh 1822: 343. Laurencia obtusa vat. paniculata C. Agardh Zanardini 1847: 20. L. paniculatus (C. Agardh) J. Agardh 1852:755 nora illeg. (later homonym of L. paniculatus Ktitzing 1849: 855). Chondrophycus paniculatus (C. Agardh) G. Fumari. Basionym: Chondria obtusa vat. paniculata C. Agardh, 1822: 343. Lectotype: LD 36711 (Herbarium of the Botanical Museum, Lund), designated by Yamada (1931). Type locality: Adriatic Sea. Homotypic synonyms: Laurencia obtusa vat. paniculata (C. Agardh) Zanardini, 1847: 20. L. paniculata (C. Agardh) J. Agardh, 1852:755 nom. illeg. (later homonym of L. paniculata Ktitzing, 1849: 855). (J. Feldmann, 1942: 81; Funk, 1955: 141; Athanasiadis, 1987: 96).

Thalli terete, 4-10cm high, reddish, cartilaginous in texture attached to substrata by a discoid holdfast 1-4 mm in diameter. Main axes 1.5-2.0 mm wide in middle portions, branched up to three orders. First order branches (up to 1 cm long) and second order branches (up to 3 mm long) radially and irregularly arranged. Last branches simple or bearing very short and unilaterally or suboppositely arranged ultimate branchlets. Apical pits with a mamillate margin. Epidermal cells (in surface view) polyhedral in basal to median parts of thalli (15-35 ~ long x 19-38 ~rn wide) and rounded to transversally elongate near apices (10-12 tun long x 12-20 ~un wide), without secondary pit connections. Transverse sections of ultimate branchlets with palisade-like epidermal cells. Medullary cells without lenticular thickenings. Two vegetative pericentral cells per axial cell.

Tetrasporangial initials cut off abaxially from the second pericentral cell. No additional tetrasporangial pericentral cells. Tetrasporangia occur in the apical portions of ultimate and penultimate branches and show a right angle arrangement. Both male and female gametophytes are unknown from the Mediterranean Sea. Remarks: Following Nam's (1999) infrageneric circumscription of the genus Chondro- phycus, this species belongs to the subgenus Palisadi (Yamada) K.W. Nam, Sectio Palisadi.


Habitat: Plants grow on rocks in the sublittoral zone from near the surface to about 16 m of depth. Mediterranean distribution: Southern Italy, Corse (France), Sithonia Peninsula (Greece) (G6mez Garreta et al., 2001).

Other distribution: Atlantic, Indian and Pacific oceans (McDermid, 1988). Due to the complicated taxonomic and nomenclatural history of this species (Boisset et al., 2000), most records should be checked. Specimens examined: CAT 129, Nerano, Naples, Italy, 28.ii.1986, -0 .2 m, sterile; CAT 1635, Gargano, Apulia, Italy, autumn 1997, - 5 m, sterile.

Figs 1-3. Chondrophycus paniculatus (CAT 129). Fig. 1. Habit. Scale = 1 cm (after Boisset et al., 2000). Fig. 2. Transverse section of a branch. Scale = 200 lam. Fig. 3. Transverse section of a branch near the apex showing an axial cell (a) with two pericentral cells (p). Scale = 50 ~m (after Boisset et al., 2000).


Chondrophycus papillosus ('papiUosa') (C. Agardh) Garbary et J. Harper, 1998:195 (Figs 4-6)

Nam & Saito (1991, figs 1-19)

Basionym: Chondria papillosa C. Agardh, 1822: 344. Holotype: Herb. Forsskhl No. 886 (held in C, the Botanical Museum of Copenhagen). Type locality: Mokha (Red Sea). Homotypic synonyms: Fucus papillosus Forsskhl, 1775:190 nom. illeg. (later homonym of E papillosus S.G. Gmelin, 1768: 188). Laurencia papillosa (C. Agardh) Greville, 1830: lii (Schiffner & Vatova, 1937: 143; J. Feldmann, 1942: 81; Funk, 1955: 141; Athanasiadis, 1987: 97). Heterotypic synonyms: Chondria obtusa var. delilei C. Agardh, 1822:342 (Naccari, 1828: 60). Fucus cyanospermus Delile, 1813:196 pl. 57: 3. Fucus tenerrimus Clemente, 1807:315 nom. illeg. (later homonym of E tenerrimus Esper, 1800: 198, pl. CX). Gigartina julacea Bory de Saint-Vincent, 1832:321 pl. 37, 4. Laurencia cyanosperma (Delile) J.V. Lamouroux, 1813:43 (Kiitzing, 1849: 855). Laurencia obtusa var. cyanosperma (Delile) Zanardini, 1847: 200. Laurencia obtusa var. delilei (C. Agardh) Zanardini, 1841: 197. Laurencia tenerrima J. Cremades in Cremades & P6rez-Cirera, 1990: 490. Reference for synonymy: De Toni (1903) and Cremades & P6rez-Cirera (1990) for L. tenerrima.

Plants epilithic, 5-10cm high, terete, cartilaginous in texture attached to substrata by a discoid holdfast with short stolon-like lower branches. Main axes up to 4 mm in diameter, branched up to five orders, with an alternate-spiral branching pattern. Branches densely clothed, except in the lower portions, with truncate, wart-like ultimate branchlets. Epidermal cells 14-40 pan long x 20-50 ~ma wide, without secondary pit connections, not projecting near the apex of branchlets; in longitudinal section very elongated and in transverse section of branches and ultimate branchlets with a palisade- like arrangement (in some ultimate branchlets, however, such an arrangement is not present). Medullary cells with thick walls, but without lenticular thickenings. Two vegetative pericentral cells per axial segment.

• Tetrasporangia with a right angle arrangement, produced by the second and the third (additionally produced) pericentral cells. Spermatangial branches produced by trichoblasts in apical pits. Cystocarps urceolate, 800-1 000 lam high, 800-1 100 ~trn wide, borne laterally on short branches of any order. Remarks: This species (as L. papillosa) was included by Yamada (1931) in the Sectio Palisadae. K.W. Nam & Saito (1991) on the basis of the study of the Holotype stated that epidermal cells of ultimate branchlets in transverse section do not show a palisade-like arrangement. Accordingly, K.W. Nam (1999) ascribed this species to the subgenus Palisadi, Sectio Papillosi J. Agardh, 1876 emend. K.W. Nam 1999 characterised by the absence of palisade-like arrangement of epidermal cells of ultimate branchlets. Con- versely, Masuda et al. (1997a) considered this species as showing epidermal cells of main axes and indeterminate branches in transverse section with a palisade-like arrangement (rarely in ultimate branchlets). Habitat: Plants grow on rocks in the midlittoral zone. Mediterranean distribution: widely distributed throughout the basin (G6mez Garreta et al., 2001). Other distribution: tropical to subtropical regions in the world (Masuda et al., 1997a). Specimens examined: CAT 1698, Brucoli, Syracuse, Italy, 29.v. 1993, -0.5 m, tetrasporophyte.


.... ~ ' ~

Figs 4-6. Chondrophycus papillosus (CAT 1698). Fig. 4. Habit. Scale = 1 cm. Fig. 5a. Detail of a transverse section of an ultimate branchlet showing the non palisade arrangement of epidermal cells. Scale = 25 lam. Fig. 5b. Detail of a transverse section of of an ultimate branchlet showing palisade-like arrangement of epidermal cells. Scale = 25 larn. Fig. 5c. Detail of a transverse section of a branch showing palisade-like arrangement of epidermal cells. Scale = 50 lam. Fig. 6. Transverse section of a branch near the apex showing an axial cell (arrow) with two pericentral cells (p). Scale = 50 lam.


Chondrophycus patentirameus ('patentiramea') (Montagne) K.W. Nam, 1999: 463 tab.1

(Figs 7-10) Boisset et al. (2000, figs 3-16).

Basionym: Chondria obtusa (Hudson) C. Agardh var. patentiramea Montagne, 1836: 322. Lectotype: M A 4256 (held in the Herbarium of the Laboratoire de Cryptogamie, Mus6um National d 'Histoire Naturelle, PC), designated by Boisset et al., 2000. Type locality: M~ze, France. Homotypic synonyms: Laurencia patentiramea (Montagne) Ktitzing, 1849: 854. Laurencia obtusa var. patentiramea (Montagne) Rabenhorst, 1847: 155.

Thalli terete, up to 10 cm high, with main axes 1-2.5 mm wide in middle portions, greenish, cartilaginous in texture attached to substrata by discoid holdfasts, 2 -4 mm in diameter, producing numerous stolon-like branches.

U

Figs 7-10. Chondrophycuspatentirameus (CAT 1594). Fig. 7. Habit. Scale = 2 cm. Fig. 8. Detail of a portion of thallus showing branching pattern. Scale = 1 cm. Fig. 9. Transverse section of a branch. Scale = 200 jarn. Fig. 10. Detail of a transverse section of a branchlet showing epidermal cells not palisade-like. Scale = 50 lain.


Branching, up to four orders, is straggling and divaricate, irregularly alternate, subopposite or subverticillate with first order branches up to 6 cm long and spirally arranged. Thalli sparsely clothed with branchlets up to 4 mm in length, initially simple in apical parts, compound and wart-like on penultimate branches in median and basal parts. Basal parts of the thalli often denuded. In surface view, epidermal cells of middle to lower parts of first- and second-order branches are elongate, 35-100 prn long x 20-60 pin wide, and arranged in longitudinal rows, without secondary pit connections. Lenticular thickenings are absent in medullary cell walls. Epidermal cells in transverse sections without a palisade-like arrangement. In the middle to lower portions of first- to second-order branches 2 or 3 layers of cortical cells are observed. Superficial cortical cells do not project in the upper portion of ultimate branchlets. Inner cortical cells are ovoid to rounded, and 35-90 ~-n long x 15-65 pin wide. Intercellular spaces between medullary cells occur. Two vegetative pericentral cells per axial cell.

Tetrasporangial initials cut off abaxially from the second pericentral cell. No additional tetrasporangial pericentral cells. Tetrasporangia occur in the apical portions of ultimate and penultimate branches and show a right angle arrangement. Spermatangial branches formed in apical pits of ultimate and penultimate branchlets from trichoblasts. Mature cystocarps, 900-1 100 prn high, 800-1 000 larn wide, formed laterally on ultimate branchlets, flask-shaped, without a basal constriction, and with a slightly rostrate carpostome. Remarks: Following Nam's (1999) infrageneric circumscription of the genus Chondro- phycus, this species belongs to the subgenus Palisadi (Yamada) K.W. Nam, Sectio Papillosi. Habitat: the species occurs mainly in littoral bays or lagoons, being probably absent from the open sea. Mediterranean distribution: M~ze (France), Ebro delta (Spain) (Boisset et al., 2000); Adriatic Sea (Hauck, 1883, as L. paniculata f. patentiramea, to be confirmed). Other distribution: no confirmed records out of the Mediterranean Sea Specimens examined: CAT 1594, Delta del Ebro, Spain, 20.viii. 1996, tetrasporophyte.

Laurencia caduciramulosa Masuda et Kawaguchi in Masuda et al., 1997b: 3, figs 1-10. (Figs 11-17)

Holotype: SAP 062086 (Herbarium of the Hokkaido University). Type locality: Hon Tre Island, Vietnam.

Plants epilithic in the lower midlittoral zone. Axes up to 5 cm high, terete, arising from a stoloniferous holdfast, branched up to four orders, with branches and branchlets irregularly alternate and spirally arranged. Epidermal cells, in surface view longitudinally elongate (70-80 pm long x 20-30 pm wide) in basal to median portions of thalli and rounded near apices, with secondary pit connections, slightly projecting near apices. Transverse sections of ultimate branchlets with not palisade-like epidermal cells. Medullary cells with lenticular thickenings. Without living plants, presence of corps en cerise is not known. Four vegetative pericentral cells per axial segment. No reproductive structures were found.

One of the main characteristics of this species is the presence of deciduous branchlets. They form near branch apices and probably function as propagules. At their detachment, such branchlets leave peculiar scars on the branch. Remarks: this is the first record of this species from the Mediterranean Sea. It seems too early, for the moment, to put forward phytogeographic considerations on this apparently disjunct distribution area since a wider distribution of the species cannot be excluded. It


16

Figs 11-17. Laurencia caduciramulosa (CAT 1683). Fig. 11. Habit. Scale = 1 cm. Fig. 12. Epider- mal ceils in surface view showing secondary pit connections. Scale = 50 lam. Fig. 13. Detail of a branch bearing small deciduous branchlets near the apex. Arrows indicate scars of shed branchlets. Scale = 0,5 mm. Fig. 14. Transverse section of a branch showing lenticular thickenings in the walls of medullary cells. Scale = 100 larn. Fig. 15. Apex of a branch showing slightly projecting epidermal cells. Scale = 100 lain. Fig. 16. Longitudinal section showing epidermal cells with secondary pit connections. Scale = 50 jxrn. Fig. 17. Transverse section of a branch near the apex showing an axial cell (arrow) with four pericentral cells (p). Scale = 50 ~trn.


should be noted that, while the species was described on specimens collected in 1993 (Masuda et al., 1997b), some Mediterranean specimens (those from Lachea Island) were collected in 1991. Habitat: plants grow on rocks in the lower midlittoral zone. Mediterranean distribution: Lachea Island (Catania, Sicily); Linosa Island, Pelagean Islands. Other distribution: Vietnam (Masuda et al., 1997b). Specimens examined: CAT 1683, Lachea Island, Catania, Italy, 23.x.1991, collected by Serio at -0 .2 m, sterile; CAT 1872, Linosa Island, Pelagean Islands, 30.ix. 1998, collected by Catra at 0.2 m, sterile.

Laurencia chondrioides BCrgesen, 1918: 252, figs 243-246. (Figs 18-20)

Boisset et al. (1998, figs 2-15).

Lectotype: C 2051 (Herbarium of the Botanical Museum of Copenhagen), designated by R. Nielsen in the Herbarium sheet. Type locality: San Jan, Puerto Rico.

Figs 18-20. Laurencia chondrioides (CAT 1648). Fig. 18. Habit. Scale = 1 cm. Fig. 19. Detail of two branches connected by a secondary discoid holdfast. Scale = 1 mm. Fig. 20. Cystocarpic branchlet. Scale = 1 mm.


Plants rosy-red, up to 8 cm high, soft in texture with axes erect or prostrate, frequently flexuous and entangled, terete or slightly ovoid in transverse section, arising from a discoid holdfast which subsequently becomes stoloniferous. Branching sparse, irregularly alternate, rarely subopposite or subverticillate with up to 3 orders of branching. Branches and branchlets often inserted at a right angle. Branchlets simple, with obtuse apices, slightly narrowed at the apices, much more so at their bases and loosely arranged in alternately or rarely in a subopposite manner. Epidermal cells with secondary pit connections, irregularly polygonal in surface view in median portions (35-80 prn long x 25-50 prn wide). Near the apices outer walls of epidermal cells are projecting. In transverse section epidermal cells are more or less isodiametric, subquad- rate or subrectangular. Lenticular thickenings generally absent (rarely present) in the medullary cells. Four pericentral cells per axial segment. In transverse section the axial filament is readily distinguishable in median portions of the thallus. Without living plants, presence of corps en cerise is not known.

Tetrasporangia, produced by pericentral cells, with a parallel arrangement. Neither the position of tetrasporangium-bearing pericentral cells nor the occurrence or not of additional pericentral cells are known. Spermatangial branches of tfichoblast-type, inserted in cup-shaped apical depressions. Cystocarps sessile (500-700 pm high x 450-800 prn wide), laterally arranged, urceolate to conical with a prominent carpostome. Habitat: a deep water species, epilithic and/or epiphytic. Mediterranean distribution: Balearic Islands (Spain), Sicily (Italy), Adriatic Sea. Other distribution: Caribbean Sea, Canary Islands (Boisset et al., 1998). Specimens examined: CAT 1648, S alina Island, Aeolian Islands, 31.v. 1990, -15 m, female gametophyte; CAT 1647, Lachea Island, Catania, Italy, 28.ix.1994, -30 m, sterile.

Laurencia epiphylla Boisset et Lino, 1998: 215, figs 2-10.

Holotype: VAB-Algae 1434 (Herbarium of the University of Valencia). Type locality: La Granadella, Alicante (Spain).

Thalli up to 20 mm high, pink to light green, soft in texture, consisting of 1 (2-3) axes arising from a discoid holdfast. Main axis often aborted. Up to four orders of ramification. Branches and branchlets radially, alternately or sub-oppositely arranged. Branchlets distally truncate and basally constricted. Epidermal cells irregularly rounded near apices, not projecting, longitudinally elongated in the median portions of axes (50-159 larn long x 15-50 larn wide), with secondary pit connections and not palisade-like in transverse section. Medullary cells with thin walls, with lenticular thickenings, showing numerous intercellular spaces. Four pericentral cells per axial segment.

Tetrasporangia cut off from pericentral ceils, arranged parallel to the central axial filament. Neither the position of tetrasporangium-bearing pericentral cells nor the occurrence or not of additional pericentral cells are known. Male and female gametophytes unknown. Remarks: No information were given by Boisset & Lino (1998) in the diagnosis of the species on corps en cerise which, however, from the illustrations, seem absent. Nevertheless, their presence can not be excluded with certainty since it seems that the authors didn't study living plants. Habitat: plants grow as epiphyte on leaves of Cymodocea nodosa (Ucria) Ascherson Mediterranean distribution: known only from the type locality.


Laurencia glandulifera (Kiitzing) Kiitzing, 1849:855 (Figs 21-23)

Rindi et al. (1996, figs 9-13)

Basionym: Chondria glandulifera Kiitzing, 1845: 329. Homotypic synonym: Laurencia obtusa var. glandulifera (Ktitzing) Rabenhorst, 1847: 155. Holotype: L 94199243 (Rijksherbarium, Leiden). Type locality: Trieste (Italy).

Thalli epilithic, up to 7 cm high, red in colour, attached to the substratum by a primary discoid holdfast and secondary holdfasts formed on descending branches. Axes terete, irregularly ramified, bearing branches with very short branchlets, of which the wartlike ultimate ones are subverticillately arranged. Epidermal cells with usually single corps en cerise, projecting near the apex and provided with secondary pit connections, in surface view are polygonal in median portions measuring 50-100 ~tm long x 40-70 ~trn wide. In transverse section, epidermal cells are rounded to ovoid and do not show a palisade-like arrangement. Lenticular thickenings are lacking in medullary cells. Four pericentral cells per axial segment.

Figs 21-23. Laurencia glandulifera (CAT 1246). Fig. 21. Habit. Scale = 1 cm (after Cecere et al., 1996). Fig. 22. Detail of a tetrasporic branch showing very short branchlets. Scale = I mm (after Cecere et al., 1996). Fig. 23. Epidermal cells in surface view showing secondary pit connections. Scale = 100 ~rn (after Cecere et al., 1996).


Tetrasporangia are produced from the third and the fourth pericentral cells. No additional tetrasporangial pericentral cells are produced. Stichidial branchlets bear tetrasporangia in parallel arrangement. Cystocarps, single or in clusters, urceolate, 800-900 larn high x 500-700 pro wide (Rindi et al., 1996). Spermatangial branches of trichoblast-type, inserted in cup-shaped apical depressions. Habitat: species epilithic, living in the lower midlittoral zone. Mediterranean distribution: Adriatic Sea, Ionian Sea, Tyrrennian Sea (G6mez Garreta et al., 2001). Other distribution: Arabian Gulf (Basson et al., 1989); Korea (Kang, 1966); Japan (Segawa, 1971); Talwan (Lewis & Norris, 1987). According to Salto (1985) records of this species from Japan and adjacent areas should be referred to L. nipponica Yamada. Specimens examined: CAT 1246, Taranto, Italy, 8.v.1991, -3 m, tetrasporophyte; CAT 1573, The Tremiti Islands, Italy, 10.x.1997, -1 m, both male and female gametophytes, tetrasporophyte.

Laurencia intricata J.V. Lamouroux, 1813: 43, pl. 3, figs 8-9 (Figs 24-31)

Masuda et al. (1998, figs 12-24)

Holotype: Lamouroux, 1813: pl. 3, figs 8-9. Type locality: The Antilles. Homotypic synonym: Laurencia obtusa var. intricata (J.V. Lamouroux) J. Agardh, 1842: 114 (the same combination was later and then illegitimately proposed by Yamada, 1931: 225).

Plants forming tufts 3-10 cm in diameter, fleshy, without percurrent axes. Thalli densely entangled with coalesced branches near the base and branched in an irregular spiral manner. Epidermal cells rounded near the apices and longitudinally elongated (40-100 larn long x 30-60 ~rn wide) in lower portions of branches, slightly projecting near the apex and provided with secondary pit connections. In transverse section epidermal cells without a palisade-like arrangement. Two to four corps en cerise present within each epidermal cell. Lenticular thickenings absent. Four pericentral cells per axial segment.

Tetrasporangia produced from the third and the fourth pericentral cells. No additional tetrasporangial pericentral cells. Tetrasporangia parallel arranged. Spermatan- gial branches, of trichoblast-type, inserted in cup-shaped apical depressions (Masuda et al., 1998). Cystocarps lateral on branches and ovoid in shape (560-880~m high x 560-880 ~trn wide). Remarks: This is the first record of this species from Italy. Observations on both female gametophytes and tetrasporophytes were made on specimens collected at Pantelleria Island. Sterile specimens were collected at the Tremiti Islands and published by Cormaci et al. (2000) as Laurencia sp. 1. No fertile male gametophytes were found in the Mediterranean Sea. Since the study on Italian specimens was carried out on not living material, no corps en cerise could be detected. Habitat: species epiphytic, living in the lower midlittoral zone. Mediterranean distribution: Libya (Godeh et al., 1992), Pantelleria Island (the Straits of Sicily) (this paper), the Tremiti Islands (Adriatic Sea) (Cormaci et al., 2000, as Laurencia sp.1). Other distribution: widely distributed in tropical to warm temperate regions in the world (Masuda et al., 1998).


~A

Figs 24-3l . Laurencia intricata (CAT 1899). Fig. 24. Habit. Scale = 1 cm. Fig. 25. Detail of a branch. Scale = 5 mm. Fig. 26. Habit of a female gametophyte. Scale = 5 mm. Fig. 27. Transverse section of a branch. Scale = 100 tma. Fig. 28. Epidermal cells in surface view showing secondary pit connections. Scale = 100 pm. Fig. 29. Longitudinal section showing epidermal cells with secondary pit connections. Scale = 50 jma. Fig. 30. Transverse section of a tetrasporic branch near the apex showing an axial cell (a) with two elongate fertile pericentral cells (fp) and two sterile pericentral cells (p). Scale = 50 ~m. Fig. 31. Longitudinal section of a tetrasporic branch showing a tetrasporangium (t) cut off abaxially from a fertile pericentral cell (fp). One cover cell (cc) is detectable. Scale = 50 ~trn.


Specimens examined: CAT 1899, Pantelleria Island (the Straits of Sicily), 27.v.1996, -0.5 m, female gametophyte, tetrasporophyte; CAT 1687, the Tremiti Islands, (Adriatic Sea), 3.x.1998, -0.2 m, sterile.

Laurencia majuscula (Harvey) Lucas, 1935:223 (Figs 32-36)

Saito & Womersley (1974, figs 1A, 6A-D); Masuda et al. (1998, figs 1-10)

Basionym: Laurencia obtusa vat. majuscula Harvey, 1863: 26. Lectotype: TCD 236a (Harvey Herbarium, held in the Herbarium School of Botany, Trinity College, Dublin, Ireland), designated by Saito & Womersley (1974). Type locality: Rottnest Island, Western Australia.

Thalli 6-8 cm high, orange in colour (reddish in shaded habitats), terete, soft in texture, attached to the substratum by a single primary discoid holdfast becoming stoloniferous by the growth of numerous stolon-like branches. Axes spirally ramified with branches and branchlets spirally ramified giving a pyramidal outline. Epidermal cells markedly projecting in apical to subapical portions of the thallus, with secondary pit connections. In fresh material, one (occasionally two) corps en cerise detectable in both epidermal cells and trichoblasts [rarely, also in medullary cells]. Epidermal cells, in surface view longitudinally elongated in median portions (40-120 pm long x 30-60 larn wide), in transverse section without palisade-like arrangement. Lenticular thickenings absent. Four periaxial cells per axial cell.

Tetrasporangial initials cut off from the third and fourth periaxial cells. No additional tetrasporangial pericentral ceils. Tetrasporangia parallel arranged. Spermatan- gial branches of trichoblast-type, inserted in cup-shaped apical depressions. Mature cystocarps flask-shaped with a prominent ostiole, 900-1 000 larn high x 800-900 larn wide, borne laterally on both branches and branchlets. Remarks: Mediterranean specimens differ from those described from Australia ones in the height of the thalli [6-8 cm in the Mediterranean versus up to 20 cm in the Australian (Saito & Womersley, 1974)] and from the Japanese and Canarian specimens in the number of corps en cerise [one, occasionally two in the Mediterranean versus two to four in both Japanese and Canarian specimens (Masuda et al., 1998]. Habitat: species epilithic, living in the lower midlittoral zone. Mediterranean distribution: Sicily and adjacent islands, Livorno and Capraia Island (Tuscan Archipelago) (Serio et al., 2000). Other distribution: widely distributed in tropical to warm temperate regions (Masuda et al., 1998). Specimens examined: TCD 236a (Lectotype); CAT 1667, Fontane Bianche, Syracuse, Italy, 20.vi.1991, -0.2 m, tetrasporophyte; CAT 1669, Capo Murro di Porco, Syracuse, Italy, 2.x.1991, -0.2 m, male gametophyte and tetrasporophyte; CAT 1476, Capo Murro di Porco, Syracuse, Italy, 27.x.1996, -0.2 m, both male and female gametophytes, tetrasporophyte.

Laurencia microcladia Kfitzing, 1865: 22, tab. 15, pl. 60b, c (Figs 37-39)

Verlaque (1981, figs 1-18)

Holotype: quoted by Yamada (1931), but not found in the Rijksherbarium at Leiden. Type locality: West Indies.


Figs 32-36. Laurencia majuscula. Fig. 32. Habit. Scale = 3 mm. (CAT 1667). Fig. 33. Epidermal cells in surface view showing one corps en cerise per cell. Scale = 50 ~un. (CAT 1669) (after Serio et al., 2000). Fig. 34. Longitudinal section of a branchlet showing epidermal cells projecting and medullary cells with one corps en cerise (CAT 1669). Scale = 200 ~m. Fig. 35. Longitudinal section of a branchlet showing an apical spermatangial depression with fertile trichoblasts. At the bottom of depression is visible the row of axial cells. Scale = 500 jam. (CAT 1476) (after Serio et al., 2000). Fig. 36. Flask-shaped cystocarp with a prominent ostiole. Scale = 500 ~n. (CAT 1476) (after Serio et al., 2000).


38

Figs 37-39. Laurencia microcladia (CAT 1475). Fig. 37. Habit. Scale = 2 cm. Fig. 38. Detail of a portion of thallus. Scale = 0.5 cm. Fig. 39. Transverse section of a branch showing lenticular thickenings in the walls of medullary cells. Scale = 50 }am.

Thalli up to 15 cm high, green to pink in colour, terete, cartilaginous in texture, attached to the substratum by a stoloniferous holdfast. Axes, with up to three branching orders, with branches and branchlets spaced, oppositely to verticillately arranged. Ultimate branchlets short and clavate. Epidermal cells polygonal to elongate (20-50 larn long x 15-30 ~aa wide), projecting near the apices showing secondary pit connections. In fresh material, one (occasionally two or three) corps en cerise detectable in both epidermal cells and trichoblasts. In transverse section, epidermal cells not palisade-like, and medullary cells with lenticular thickenings. Four pericentral cells per axial segment.

Tetrasporangia produced from the third and the fourth pericentral cells, with a parallel arrangement. No additional tetrasporangial pericentral cells. Spermatangial branches of trichoblast-type inserted in apical pits. Mature cystocarps urceolate, 600-750 larn high x 700-750 larn wide, borne laterally on both branches and branchlets. Habitat: epilithic in the upper infralittoral zone. Mediterranean distribution: first recorded by Verlaque (1981) from Corse, subsequently recorded from throughout the basin (G6mez Garreta et al., 2001). Other distribution: tropical Atlantic coast (Verlaque, 1981).


Specimens examined: L (Rijksherbarium, Leiden) 9577, St Maarten, Guanabay, West Indies, 13.v.1958; CAT 1475, Capo San Vito, Trapani, Italy, 19.ix.1993, -1 m, both male and female gametophytes, tetrasporophyte; CAT 1482, Fontane Bianche, Syracuse, Italy, 17.vii. 1991, -3 m, tetrasporophyte.

Laurencia minuta Vandermeulen, Garbary et Guiry subsp, scammaccae G. Furnari et Cormaci 1990, figs 1-9.

(Figs 40-42) Boisset & Aranda (1992, figs 1--4); Rindi et al. (1996, figs 14-18)

Holotype: CAT 520 (Herbarium of the Department of Botany of the University of Catania). Type locality: Capo Passero (Syracuse, Italy).

Thalli 1-3 mm high, terete, attached to the substratum by a discoid holdfast from which one to two erect axes (sometimes with one-three additional axes) arise. Axes

Figs 40-42. Laurencia minuta subsp, scammaccae (CAT 520). Fig. 40. Habit. Scale = 1 mm (after Furnari & Cormaci, 1990). Fig. 41. Epidermal cells in surface view showing secondary pit connections. Scale = 50 pm (after Furnari & Cormaci, 1990). Fig. 42. Transverse section of an axis showing lenticular thickenings in the walls of medullary cells. Scale = 50 pm (after Furnari & Cormaci, 1990).


simple or with a short lateral subapical branch. Epidermal cells polyhedral (30-40 [am long x 20-35 Wn wide), not or slightly projecting near the apex. Lenticular thickenings present. Without living plants, presence of corps en cerise is not known. Four pericentral cells per axial segment.

Tetrasporangia produced from the third and fourth pericentral cells, with a parallel arrangement. No additional tetrasporangial pericentral cells produced. Sperma- tangial branches of trichoblast-type inserted in apical pits. Cystocarps ovoid, 35-40 larn high x 40-45 larn wide, laterally inserted near the apex. Habitat: epiphytic on leaves of the seagrasses Posidonia oceanica (L.) Delile and Cymodocea nodosa (Ucria) Ascherson as well as on macroalgae in the infralittoral zone. Mediterranean distribution: Spain (Boisset & Aranda, 1992), Italy (G6mez Garreta et al., 2001). Specimens examined: CAT 520, Capo Passero, Syracuse, Italy, 1.xi.1984, -25 m, both male and female gametophytes, tetrasporophyte; CAT 855, Saiina Island, Aeolian Islands, 1.v. 1990, -10 m, both male and female gametophytes, tetrasporophyte.

Laurencia obtusa (Hudson) J.V. Lamouroux, 1813:42 (Figs 43--47)

Saito (1982, figs 1-10); Maggs & Hommersand (1993, fig. 125 a-d)

Basionym: Fucus obtusus Hudson, 1778: 586. Holotype: BM-K, unnumbered sheet (Hudson Herbarium held in the Herbarium of the Natural History Museum, London). Type locality: Sussex and Devon (England). Homotypic synonym: Chondria obtusa (Hudson) C. Agardh, 1817: XVIII, 35. Heterotypic synonyms: Laurencia obtusa var. genuina Ktitzing, 1865: 19, pl. 54a, b. (Ardissone, 1883). Laurencia obtusa [var. genuina] f. racemosa (Ktitzing) J. Feldmann, 1942: 81. Laurencia obtusa var. pulvinata J. Feldmann, 1931: 243. Laurencia obtusa var. racemosa Ktitzing, 1865: 20, pl. 55a, b. On the basis of both descriptions and illustrations, the above infraspecific taxa are here considered as heterotypic synonyms of L. obtusa.

Thalli 5-15 cm high, red-purple to bright orange in colour, terete, fairly soft in texture, attached to the substratum by a stoloniferous holdfast. Axes irregularly and radially ramified with branches and branchlets radially ramified giving a pyramidal outline. Epidermal cells elongate-polygonal in surface view, 30-130 ~arn long x 20-55 larn wide, never projecting, with secondary pit connections and one corps en cerise detectable in fresh material. In transverse section, epidermal cells without palisade-like arrangement. Lenticular thickenings absent. Four periaxial cells per axial segment.

Tetrasporangia produced from the third and the fourth pericentral cells. No additional tetrasporangial pericentral cells produced. Stichidial branchlets bear tetrasporangia in parallel arrangement. Spermatangial branches, of trichoblast-type, inserted in cup-shaped apical depressions. Cystocarps, 700-800 larn high x 600-900 larn wide, globu- lar with a prolonged ostiole. Habitat: epiphytic (rarely epilithic), living in the lower midlittoral to the upper infralittoral zones. Mediterranean distribution: widely distributed throughout the basin (G6mez Garreta et al., 2001). Other distribution: considered to be cosmopolitan, but most records should be reconsid- ered under recent taxonomic criteria.


Figs 43-47. Laurencia obtusa (CAT 1893). Fig. 43. Habit. Scale = 1 cm. Fig. 44. Transverse section of a branch. Scale = 100 ~trn. Fig. 45. Transverse section near the apex of a stichidial branchlet showing the cutting off of tetrasporangia from the mother cells (arrows) in the direction of the radius. Scale = 100 prn (after Cormaci et al., 1994). Fig. 46. Transverse section near the apex of a branch showing an axial cell (arrow) with four pericentral cells (p). Scale = 50 ~ma. Fig. 47. Detail of transverse section of a branch showing the non-palisade arrangement of epidermal cells. Scale = 50 pm.


Specimens examined: CAT 1893, Fontane Bianche, Syracuse, Italy, 20.vi.1991, -0.1 m, tetrasporophyte; CAT 1472, the Tremiti Islands, Adriatic Sea, 8.x. 1997, -1 m, tetrasporophyte.

Osmundea maggsiana Serio, Cormaci et G. Furnari, 1999, figs 2-10 (Figs 48-52)

Holotype: CAT 1523 (Herbarium of the Department of Botany of the University of Catania). Type locality: Pantelleria Island (the Straits of Sicily).

Thalli epilithic, light red in colour, terete, rigid in texture, up to 4.5 cm high attached to the substratum by a solid discoid holdfast. Axes up to 3 mm in diameter irregularly ramified, up to three orders of branching with branches irregularly alternate- spirally (seldom suboppositely) arranged. Epidermal cells not protruding at the end of branchlets, without secondary pit connections; in transverse section radially elongate and palisade-like. In surface view, epidermal cells elongate, 21-24 ~m long, 12-14 ~rn wide, in median portions of the thallus. Lenticular thickenings absent. Two pericentral cells per axial cell.

Tetrasporangia, produced from epidermal cells, cut off from the mother cells laterally. Male reproductive structures of filament-type, with spermatangial branches unramified inserted in cup-shaped depressions located at the bifurcation of branchlets. Cystocarps unknown. Habitat: epilithic in the lower midlittoral zone. Mediterranean distribution: known only from the type locality. Specimens examined: CAT 1523, Pantelleria Island, the Straits of Sicily, 9.vi.1994, -0.2 m, male gametophyte, tetrasporophyte.

Osmundea pelagiensis G. Furnari in Cormaci et al., 1994: 375, figs 2-12 (Figs 53-57)

Holotype: CAT 1234 (Herbarium of the Department of Botany of the University of Catania). Type locality: Lampedusa Island (the Straits of Sicily). Invalid name: Laurencia pelagiensis Cormaci, G. Furnari et Serio, 1994:366 nom. invaL according to Art. 34.1(a) of I.C.B.N. (Greuter et al., 2000).

Thalli light red, epilithic, up to 10 cm high, with axes 2-3 mm broad, arising from a thick, spreading basal crust, compressed except near the base. Axes generally simple in the basal portion, branched up to three orders in the upper half with branchlets terete, distichously, unilaterally or irregularly arranged. Epidermal cells in surface view slightly elongated longitudinally near apices (15-25 ~ a long × 10-20 larn wide) much more in median and basal portions of the thallus (20-40 ~ long x 8-15 ~aa wide), not projecting, without secondary pit connections; in transverse section radially elongated and palisade-like. Lenticular thickenings absent. Two pericentral cells per axial segment.

Tetrasporangia produced from epidermal cells, cut off from the mother cells laterally. Male reproductive structures of filament-type with spermatangial branches unramified, inserted in cup-shaped depressions located either at the bifurcation of branchlets or laterally near apices. Cystocarps, ~)0-700 larn high, 700-800 larn wide, sessile and ovoid in shape with a short ostiole and generally disposed in the subapical portions of branchlets.


Figs 48-52. Osmundea maggsiana (CAT 1523). Fig. 48. Habit. Scale = 5 mm. Fig. 49. Detail of tetrasporangial branches. Scale = 2 mm. Fig. 50. Transverse section of a stichidial branchlet near the apex showing a mother cell (arrow) of a tetrasporangium oriented radially and the tetrasporangium cut off laterally and clockwise. Scale = 200 ~na (after Serio et al., 1999). Fig. 51. Detail of a spermatangial depression in longitudinal section showing spermatangial branches of filament- type. Scale = 50 w'n (after Serio et al., 1999). Fig. 52. Transverse section near the apex of a branch showing three axial cells (a) each of them with two pericentral cells (p). Scale = 50 lam.


Figs 53-57. Osmundea pelagiensis (CAT 1234) (after Cormaci et al., 1994). Fig. 53. Habit. Scale = 2 cm. Fig. 54. Epidermal cells in surface view. Scale = 50 larn. Fig. 55. Transverse section of a branchlet showing epidermal cells radially elongated and with a palisade arrangement. Scale = 50 larn. Fig. 56. Transverse section near the apex of a branch showing axial cells (a) with two pericentral cells (p). Scale = 50 ~rn. Fig. 57. Detail of a male plant showing cup-like spermatangial depressions. Scale = 2 mm.


Habitat: Plants grow on rocks in the lower midlittoral zone. Mediterranean distribution: Pelagean Islands, Pantelleria Island (the Straits of Sicily) and Tremiti Islands (Adriatic Sea). Specimens examined: CAT 1234, Lampedusa Island, Pelagean Islands, 23.vi. 1991, -0.2 m, both male and female gametophytes, tetrasporophyte; CAT 1481, the Tremiti Islands, Adriatic Sea, 14.vi. 1997, -0.1 m, both male and female gametophytes, tetrasporophyte.

Osmundea pelagosae (Schiffner) K.W. Nam in Nam et al., 1994:393 tab. 3 (Figs 58-62)

Furnari & Serio (1993a, figs 1-9)

Basionym: Rodriguezella pelagosae Schiffner, 1931: 149. Holotype: B19182 (Botanisches Museum Berlin-Dahlem). Type locality: Pelagosa Island (Adriatic Sea). Homotypic synonym: Laurencia pelagosae (Schiffner) Ercegovir, 1949: 66.

Thalli red, flat, arising from a discoid holdfast, up to 15 cm high with axes 2-3 mm wide irregularly and distichously ramified up to two orders; branchlets short, distichous and opposite, spine-like in the lowest parts of the thallus; epidermal cells polyhedral near the apex (30-50 ~trn long x 20-30 ~n wide), slightly elongated in the median part of the thallus (30-50 ~arn long × 10-15 ~rn wide), not protruding at the end of branchlets, with secondary pit connections; lenticular thickenings present in the walls of the inner medullary cells. Two pericentral cells per axial segment.

Tetrasporangia produced from epidermal cells, cut off from the mother cells laterally. Male reproductive structures of filament-type with spermatangial branches unramified, ending with an elongate apical cell, inserted in pocket-shaped depressions with an ostiole-like opening, generally as wide as deep, 280-520 jam x 230-570 larn, located both at the bifurcation of branches and branchlets and laterally near apices. Cystocarps ovoid in shape 450-550 Jam wide and 400-500 ~trn long, distributed in the middle to subapical part of branches. Habitat: epiphytic in lower infralittoral to circalittoral zones. The species can occur also in shallower water but in shaded habitats. Mediterranean distribution: widely distributed throughout the basin (G6mez Garreta et al., 2001). Specimens examined: CAT 1051, PozziUo, Catania, Italy, 1.xi. 1991, -14 m, both male and female gametophytes, tetrasporophyte; CAT 1162, Vulcano Island, Aeolian Islands, 1.iv.1991, -31 m, sterile.

Osmundea pinnatifida (Hudson) Stackhouse, 1809:79 [figs in Maggs & Hommersand (1993, fig. 127 a-f)]

Basionym: Fucus pinnatifidus Hudson, 1762: 473. Lectotype: BM 405 (Petiver Herbarium held in the Herbarium of the Natural History Museum, London), designated by Irvine & Dixon (1982). Type locality: Harwich, Essex (England). Homotypic synonyms: Chondria pinnatifida (Hudson) C. Agardh, 1817: xviii, 35. Laurencia pinnatifida (Hudson) J.V. Lamouroux, 1813: 42.

Thalli attached to the substratum by a stoloniferous system, fiat, 2-8 cm high, cartilaginous in texture, brownish-purple to black. Main axes to 2.5 mm wide, branched to 4-5 orders, with both branches and branchlets irregularly alternate-distichously


62

Figs 58-62. Osmundeapelagosae (CAT 1051). Fig. 58. Habit. Scale = 5 mm (after Furnari & Serio, 1993a). Fig. 59. Epidermal ceils in surface view showing secondary pit connections. Scale = 50 ~na (after Furnari & Serio, 1993a). Fig. 60. Longitudinal section of a pocket-shaped spermatangial depression with spermatangial branches of filament-type. Scale = 200 ~n. Fig. 61. Cystocarpic branchlets. Scale = 1 mm. Fig. 62. Simple spermatangial branch ending with an elongate apical cell. Scale = 50 larn (after Furnari & Serio, 1993a).


arranged. Epidermal cells in surface view elongate-polygonal, without secondary pit connections. Cortex of two layers, the outer one conspicuously less pigmented and smaller than the inner one. Lenticular thickenings absent. Two vegetative pericentral cells per axial cell.

Tetrasporangia produced from epidermal cells, cut off from the mother cells laterally. Male reproductive structures of filament-type, with spermatangial branches unramified, inserted in pocket-shaped depressions with an ostiole-like opening, 1 000-1 200 ~tm x 720-1 120 ~rn, located laterally on ultimate branchlets in series of 1-3 or singly at the bifurcation of branches and branchlets. Cystocarps ovoid, 840-960 ~arn high x 660-840 ~arn wide, located laterally on ultimate branchlets often fused laterally to surrounding branchlets. Habitat: plants grow on rocks in the midlittoral zone. Mediterranean distribution: The only confirmed record of this species is that from Islas Chafarinas (Alboran Sea) (Boisset et al., 1995) Other distribution: East Atlantic Ocean (Maggs & Hommersand, 1993).

Osmundea truncata (Kiitzing) K.W. Nam et Maggs in Nam et al., 1994:393 tab. 3. (Figs 63-67)

Maggs & Hommersand (1993, fig. 129 a,c and e-g); Furnari & Serio (1993b, figs 1-12)

Basionym: Laurencia truncata Ktitzing, 1865: 19, pl.51c. Holotype: L 941.99.271 (Rijksherbarium, Leiden). Type locality: Croatia (Pirano).

Thalli light red, branched to 4-5 orders, with irregularly alternate distichous branches. Branches irregularly ramified alternately to sub-oppositely. Axes 1-2 mm broad, arising from a discoid holdfast, up to 12 cm high, compressed except near the base which is terete. Ultimate branchlets terete. Epidermal cells in surface view very elongate longitudinally, 80-100 ~trn long × 10-15 ~rn wide, with secondary pit connections. In transverse section epidermal cells are obconic in shape and not palisade-like arranged. Medullary cells with abundant lenticular thickenings. Two vegetative pericentral cells per axial cell.

Tetrasporangia produced from epidermal cells, cut off from the mother cells laterally. Male reproductive structures are of filament-type, with spermatangial branches unramified, inserted in cup-shaped depressions located either at the bifurcation of branches and branchlets or laterally near apices. Cystocarps urceolate with a protruding ostiole. Habitat: epiphytic on several algae and epilithic on rocks in upper infralittoral zone. More abundant in sheltered habitats. Mediterranean distribution: widely distributed throughout the basin [as L. truncata and the misapplied names L. pinnatifida and O. ramosissima (Oeder) Athanasiadis] (G6mez Garreta et al., 2001). Other distribution: Lough Hyne, Ireland, and the Lizard, Cornwall, England (Nam et al., 2OO0). Specimens examined: CAT 1099, Lachea Island, Catania, Italy, 3.vii.1991, -0.2 m, both male and female gametophytes, tetrasporophyte; CAT 1153, Taranto, Italy, 14.x.1987, -0.3 m, both male and female gametophytes, tetrasporophyte; CAT 1183, Ustica Island, Italy, 6.vi.92, -0.2 m, male gametophyte.


Figs 63-67. Osmundea truncata (CAT 1099). Fig. 63. Habit. Scale = 50 ram. Fig. 64. Transverse section of an axis showing medullary cells with lenticular thickenings. Scale = 200 ~m. Fig. 65. Male gametophyte with cup-like spermatangial depressions. Scale = 1 mm (after Furnari & Serio, 1993b). Fig. 66. Epidermal cells in surface view showing secondary pit connections. Scale = 50 ~rn. Fig. 67. Longitudinal section of a branchlet showing a cup-like spermatangial depression located laterally to the apical pit and showing spermatangial branches of filament-type. Scale = 200 Inn (after Furnari & Serio, 1993b).


Osmundea verlaquei G. Furnari, 1994 in Cormaci et al., 1994: 375, figs 13-25 (Figs 68-73)

Holotype: CAT 1370 (Herbarium of the Department of Botany of the University of Catania). Type locality: Sausset (Bouches du Rh6ne, France). Invalid name: Laurencia verlaquei Cormaci, G. Furnari et Serio, 1994:368 nom. inval. according to Art. 34.1(a) of I.C.B.N. (Greuter et al., 2000).

Thalli epilithic, up to 8 cm high, with axes 2-3 mm broad, arising from a thin, spreading basal crust, compressed except near the base, irregularly ramified up to three orders. Branches with branchlets terete, distichous, generally simple and short. In the median portions of the most developed branches, branchlets are ramified. Epidermal cells in surface view slightly elongate longitudinally near the apices (15-30prn long x 10-15 prn wide) much more in median and basal portions of the thallus (35-45 pm long x 10-15 pin wide), not projecting, with secondary pit connections, in transverse section not palisade-like. Lenticular thickenings absent. Two pericentral cells per axial segment.

Tetrasporangia produced from epidermal cells cut off from the mother cells laterally. Male reproductive structures of filament-type, with spermatangial branches simple or irregularly ramified, inserted in cup-like but slightly sunken depressions located either at the bifurcation of branchlets or laterally near apices. Cystocarps urceolate, 1 100-1 300 ~rn high x 1 000-1 050 larn wide, borne laterally on ultimate branchlets. Habitat: epilithic in the lower midlittoral zone. Mediterranean distribution: Sausset (Bouches du Rh6ne); widely distributed on all Italian coast (G6mez Garreta et al., 2001). Specimens examined: MI (Herbarium of Department of Biology, Sect. of Syst. Bot., University of Milano) 124, Cornigliano, Genova, Italy; CAT 1241, Sausset, Marseilles, France, 8.iii.1994, -0.2 m, both male and female gametophytes, tetrasporophyte; CAT 1402, Riposto, Catania, Italy, 19.5.1995, -0.1 m, both male and female gametophytes, tetrasporophyte; CAT 1549, the Tremiti Islands, Adriatic Sea, 24.v.1997, -0.5 m, male gametophyte, tetrasporophyte.

Key to Mediterranean species of Laurencia complex

la. Thalli throughout compressed or with only ultimate branchlets, cylindrical. Charac- ters of the genus Osmundea (two pericentral cells per axial segment, spermatangial branches of filament-type and tetrasporangia produced from epidermal cells) ...... 2

lb. Thalli cylindrical ........................................................................................................ 6 2a. Secondary pit connections between epidermal cells present ................................ 3 2b. Secondary pit connections between epidermal cells absent ................................. 5

3a. Axes arising from a spreading basal crust. Medullary cells without lenticular thickenings. Branches with ultimate branchlets terete, distichous, generally simple, quite short near the apex. Spermatangial depressions cup-like, but slightly sunken. Species living in the midlittoral zone ....................................... Osmundea verlaquei

3b. Axe(s) arising from a discoid holdfast or from a stoloniferous holdfast. Medullary cells with lenticular thickenings ............................................................................... 4

4a. Epidermal cells in surface view very elongated longitudinally. Spermatangial depressions cup-shaped. Cystocarps urceolate. Species living in the lower midlittoral zone to 4-5 m depth ....................................................... Osmundea truncata


Figs 68-73. Osmundea verlaquei (CAT 1241). Fig. 68. Habit. Scale = 1 cm. Fig. 69. Apical portion of an axis. Scale = 1 mm (after Cormaci et al., 1994). Fig. 70. Epidermal ceils in surface view showing secondary pit connections. Scale = 50 lam (after Cormaci et al., 1994). Fig. 71. Longitu- dinal section of a branch showing epidermal cells with secondary pit connections. Scale = 50 tam. Fig. 72. Longitudinal section of a branchlet showing a deep cup-like spermatangial depression located laterally to the apical pit and showing spermatangial branches of filament-type Scale = 250 ~ma (after Cormaci et al., 1994). Fig. 73. Transverse section of a stichidial branchlet near the apex showing mother cells (arrows) of tetrasporangia oriented radially and tetrasporangium cut off laterally and clock- and counterclockwise. Scale = 0.5 rnm (after Cormaci et al., 1994).


4b. Epidermal cells in surface view polyhedral. Spermatangial depressions pocket- shaped. Cystocarps ovoid. Species living in the lower infralittoral to circalittoral zones or if in shallower water in shaded habitats ............... Osmundea pelagosae

5a. Axes arising from a thick spreading crust. Epidermal cells, in transverse section, radially elongated and palisade-like. Medullary cells without lenticular thickenings. Spermatangial depressions cup-shaped. Species living in the midlittoral zone .......... .................................................................................................. Osmundea pelagiensis

5b. Axes arising from a stoloniferous holdfast. Epidermal cells, in transverse section, obconic and not palisade-like. Medullary cells with lenticular thickenings. Sperma- tangial depressions pocket-shaped. Species living in the midlittoral zone ................ ................................................................................................... Osmundea pinnatifida

6a. Secondary pit connections between epidermal cells present. With characters of the genus Laurencia (four pericentral ceils per axial segment, spermatangial branches of trichoblast-type, tetrasporangia produced from pericentral cells). Tetrasporangia with a parallel arrangement ................................................................................... 7

6b. Secondary pit connections between epidermal cells absent ............................... 15 7a. Thalli not taller than 20 mm ...................................................................................... 8 7b. Thalli up to 15 cm high ............................................................................................. 9

8a. One to three (rarely four) erect axes, arising from a discoid holdfast. Axes simple or with one short subapical branchlet. Epidermal cells not or slightly projecting near the apex. Medullary cells with lenticular thickenings. Species epiphytic on both seagrasses leaves and macroalgae .... Laurencia minuta subsp, scammaccae

8b. One (occasionally two or three) erect axes arising from a discoid holdfast. Axes to four orders of ramification. Epidermal cells not projecting near the apex. Species epiphytic only on seagrasses leaves ....................................... Laurencia epiphylla

9a. Epidermal cells never projecting. Axes irregularly and radially ramified, arising from stoloniferous holdfast. Branches and branchlets radially ramified. Medullary cells without lenticular thickenings ......................................................... Laurencia obtusa

9b. Epidermal cells more or less projecting near the apex .......................................... 10 10a. Axes arising from a discoid holdfast (sometimes forming stolon-like branches).

Branches bearing very short branchlets with wart-like ultimate branchlets subverticillately arranged. Medullary cells without lenticular thickenings. Species living in lower midlittoral to upper infralittoral zones ... Laurencia glandulifera

10b. Axes arising from a stoloniferous holdfast ....................................................... 11 l la . Thalli entangled ...................................................................................................... 12 l lb . Thalli not entangled ................................................................................................ 13

12a. Axes, erect or prostrate, frequently flexuous and entangled. In transverse section, the axial cell is readily distinguishable in median portions of the thallus. Branching sparse, irregular with branches and branchlets often inserted nearly at a right angle. Branchlets simple with apices obtuse. Species living in the lower infralittoral to circalittoral zones or if in shallower water in shaded habitats ..... .......................................................................................... Laurencia chondrioides

12b. Thalli densely entangled with coalesced branches at the lower portions. Branch- ing irregularly spiral. In transverse section the axial cell not distinguishable in median portions of the thallus. Species living in the lower midlittoral zone on corallinaceous algae ............................................................... Laurencia intricata

13a. Presence of deciduous branchlets formed abundantly near branches. Epidermal cells in transverse section not palisade-like. Medullary cells with abundant lenticular thickenings. Species living epilithic in the lower midlittoral zone .......................... ......................................................................................... Laurencia caduciramulosa

13b. Absence of deciduous branchlets ........................................................................... 14


14a. Thalli cartilaginous in texture. Axes oppositely and/or verticillately ramified. Branchlets in whorls of 2-3, very short near apices, clavate and restricted at their bases. Medullary cells with lenticular thickenings. Species living in the infralittoral zone ............................................................................ Laurencia microcladia

14b. Thalli soft in texture. Axes radially ramified. Branches and branchlets spirally ramified giving a pyramidal outline to the thallus. Medullary cells without lenticular thickenings. Species living in the lower midlittoral to upper infralittoral zone ...................................................................................... Laurencia majuscula

15a. With the characters of the genus Osmundea. Axes arising from a discoid holdfast. Epidermal cells in transverse section, radially elongated and palisade-like. Medul- lary cells without lenticular thickenings. Spermatangial depressions cup-shaped. Species living in the lower midlittoral zone ......................... Osmundea maggsiana

15b. With the characters of the genus Chondrophycus (two pericentral cells per axial segment, spermatangial branches of trichoblast-type, tetrasporangia produced from pericentral cells) .................................................................................................... 16

16a. Axes arising from a discoid holdfast without stolon-like branches. Epidermal cells of branches and ultimate branchlets in transverse section radially elongated and palisade-like. Axes and branches irregularly and alternately ramified. Apices sunken with mamillate edges. Tetrasporangia with a fight angle arrangement. Species living in infralittoral zone ........................... Chondrophycus paniculatus

16b. Axes arising from a discoid holdfast producing stolon-like branches ............. 17 17a. Epidermal cells of branches and of some ultimate branchlets in transverse section

palisade-like. Thalli cartilaginous and very rigid with branches very densely clothed with numerous truncate, wart-like ultimate branchlets, subverticillately arranged. Tetrasporangia with a fight angle arrangement. Species living in lower midlittoral zone .................................................................................. Chondrophycus papillosus

17b. Epidermal cells of branches and all ultimate branchlets in transverse section obconic and not palisade-like. Branching divaricate with branches arising at open angles to 90 °. Tetrasporangia with a fight angle arrangement. Species living in the midlittoral zone in bays and lagoons ......................................... Chondrophycus patentirameus

Acknowledgements. We thank the Curator of the Rijksherbarium, Dr Per Lassen (Herbarium of Lund), and the Curator of the Herbarium of Department of Biology of Milano for information on type materials held in their herbaria as well as for loan of herbarium specimens. We particularly thank Dr J. Huisman, Dr Wm J. Woelkerling and the anonymous reviewer for precious suggestions to improve the paper. We also thank Dr P.C. Silva for his constructive discussion about nomenclatural problems. This work was supported by a Grant of the University of Catania.

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The Laurencia complex (Rhodophyta, Rhodomelaceae) in the Mediterranean Sea: an overview

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