Shallow-water comatulid crinoids (Echinodermata) from Barbados, West Indies

Museum of Paleontology, University of Michigan, Ann Arbor, MI., U.S.A. 48109 Received January 3, 1979

LIDDELL, W. D. 1979. Shallow-water comatulid crinoids (Echinodermata) from Barbados, West Indies. Can. J. Zool. 57: 2413-2420.

The shallow-water crinoid fauna of the northwest coast of Barbados consists of six species: Analcidometra armata (Pourtales), Nemasterdiscoidea (P. H. Carpenter), Nemaster rubiginosa (Pourtales), Comactinia echinoptera (J. Miiller), Ctenantedon kinziei Meyer, and Tropiometra carinata (Lamarck). Of these, only the first three may be regarded as common. The highest concentrations of crinoids occur along the seaward slope of the bank reef, which parallels the coast. Here the combined densities of crinoids over large areas may reach 1. 15/m2, which is comparable with or higher than densities found elsewhere in the Caribbean. The co-occurring Nemaster discoidea and Nemaster rubiginosa exhibit broadly overlapping bathymetric ranges and habitat utilization patterns. Of the more common species, Analcidometra armata alone shows a restricted bathymetric distribution and a unique substrate type (an exposed position on the gorgonian Pseudopterogorgia sp.).

LIDDELL, W. D. 1979. Shallow-water comatulid crinoids (Echinodermata) from Barbados, West Indies. Can. J. Zool. 57: 2413-2420.

Lafaune crinoide deq eaux peu profondes de la cdte nord-ouest de la Barbade se compose de six espkces: Annlcidomerrd nrm~rfu [Pourtalks). Nem~lstrr discoidea (P, H. Carpenter). Nemasrrr rtrl)iginosr~ (Puurlales), Cnmacrinifl erl~inoptera (1. Miiller). Ctenanr~d<+n kinziei Meyer et Trnpiometra curinura (Lamarck). Seules les trois premieres de ceq ~ s p e c e s sunt asscz com- munes. C'est sur la pente du ricif dirigiie vers Ce large et parallkle b la cbte qu'habire la plus grande concentration de crinoides. A cet enilroit. la densite totate des crinoides sur de grandes surfaces peuL atteindre 1.15/m2, valeur comparable ou ~tipirieure aux densites m e s u r h en d'autres points des Caraibes. Nernnster di.\ cnirlen el Nemnsrer rrrhiginasa. esp+ces qui cohabiten1 . occupent des zone5 bathyrnitriques qui se rccoupent largernent et unt d e ~ habitats semhlables. Drs especes communes. seule AnrrlriJnntetru nrnrnta a une repart~tion bathymktrique restreinte et un type de substrat particulier [position exposee sur la gorgone Ps~rrdoprerc>gorgin sp.).

[Traduit par le journal]

Introduction Comatulid crinoids are conspicuous members of

many Caribbean reef communities. The general zoogeographic and bathymetric distributions of shallow-water crinoids within the Caribbean are documented by Clark (1931, 1947, 1950), Macurda and Meyer (19771, and Meyer et al. (1978). Re- cently, detailed studies of crinoid'distributions and their ecology have been made possible through the use of SCUBA diving and in situ observations. The crinoid faunas of Jamaica and Curacao have been described by Meyer (1973a, 1973b, respectively), that of Colombia by Meyer and Macurda (1976), and that of the Bahamas by Macurda (1973, 1975). The present paper deals with the ecology and dis- tributions of the shallow-water crinoids of the northwest coast of Barbados, West Indies (13'15' N , .59"3Of W).

Methods The crinoid fauna was examined in the vicinity of the Bellairs

Research Institute of McGill University, St. James, Barbados

'Present address: Department of Earth Sciences, University of New Orleans, Lake Front, New Orleans, LA, U.S.A. 70122.

during August, 1977. Observations were made by SCUBA di- ving at several sites, including nearshore beach rock in the vicinity of Six Men's Bay to the north of Bellairs, the Bellairs fringing reef, and the "bank reef ' directly offshore of the Bel- lairs Institute, as well as a sitejust south of the Institute (Figs. l , 2). Investigations were conducted to depths of 36m, which represents the approximate lower limit of reef growth in the study area. Crinoids were counted within 2-m wide strips positioned parallel to depth contours. The location of each crinoid was plotted within the transect strips and data on sub- strate (habitat) type, height of crinoid above reef floor, amount of arm extension from substrate, and orientation of arms were recorded. The latter was determined by measuring the compass direction in which the crinoid's arm array was extended from its habitat.

Results The shallow-water crinoid fauna of Barbados

consists of six species: Analcidometra armata (Pourtales), Comactinia echinoptera (J. Miiller), Ctenantedon kinziei Meyer, Nemaster discoidea (P. H . Carpenter), Nemaster rubiginosa (Pour- tales), and Tropiometra carinata (Lamarck) (Table 1; Figs. 3, 4). Of these, only three, Nemaster dis- coidea, N . rubiginosa, and Analcidometra armata, may be regarded as common and will be examined

0008-4301/79/122413-08$01 .W/O @ 1979 National Research Council of Canada/Conseil national de recherches du Canada

Can

. J. Z

ool.

Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Uta

h St

ate

Uni

vers

ity -

Log

an o

n 02

/15/

13Fo

r pe

rson

al u

se o

nly.

2414 CAN. J . ZOOL. VOL. 57. 1979

S i x Men's Boy S p e i g h t s t o w n

Bel la i rs -

B r i d g e t o w n 2 4

B A R B A D O S FIG. 1 . Map of Barbados showing study area.

1

FIG. 2. Reef profile off the Bellairs Research Institute (Verti- cal scale exaggerated approximately three times).

in detail. With the exception of the closely related N. discoidea and N. rubiginosa, the members of the fauna are readily distinguished on the basis of differences in morphology as well as behavior.

Despite many similarities, Nemaster discoidea and N. rubiginosa are morphologically distinct. One feature which is readily apparent in the field is that the arms of N. discoidea are more slender (1.4mm vs. 1.9mm mean diameters at base) and often shorter (85 mm vs. 115 mm mean lengths) than those of N. rubiginosa. Their skeletons also differ in the position of the second syzygial articu- lations of the free arms (occurring approximately between brachials 8 and 9 in N. discoidea and be- tween brachials 11 and 12 in N. rubiginosa), number of comb-bearing pinnules (two or three in N. discoidea and three or four in N. rubiginosa), and in length of arm rays (equality of all rays in the former, shortening of C and D rays in the latter (Clark 193 1 ; Meyer 1973a)).

At Barbados, the arms of N. discoidea are often a pale yellow-green with a thin black abambulacral stripe and white "beaded" pinnules with black tips. Forms of N. discoidea with entirely black arms are less commonly encountered as well. It should be noted that Clark's (1931, p. 215) key to

the species of Nemaster lists the presence of a black abambulacral (dorsal) stripe as a characteris- tic of N. rubiginosa, not N. discoidea. This feature of the key is in need of revision as the description probably pertains to specimens of N. discoidea more common elsewhere in the Caribbean posses- sing black arms, which could not be expected to show a black abambulacral stripe. Furthermore, upon close examination, arms of such black forms of N. discoidea frequently show a thin black abam- bulacral stripe in the lighter colored, most proximal regions. The specimens of N. discoidea from Bar- bados agree with Clark's description in most other respects.

Nemaster rubiginosa possesses arms that are orange to brown or black with a black abambulacral stripe and orange to brown pinnules (with or with- out orange or yellow tips). The population of N. rubiginosa is dominated by large brown to black forms that comprise approximately 75% of the population. In addition to larger size these varieties show an increase in arm number (average 24) and are similar to Clark's (193 1) N. iowensis (Springer), later synonomized with N. rubiginosa by Meyer (19736). As such, the population of N. rubiginosa shows a close affinity to those of southern Carib- bean sites such as Colombia and Curacao (Meyer 19736; Meyer and Macurda 1976; personal obser- vations) and a lesser affinity to those of Jamaica (Meyer 1973a), the Bahamas (Macurda 1975), and the Cayman and Virgin Islands (D. B. Macurda, Jr., and D. L. Meyer, personal communication). In contrast, the population of N. discoidea consists largely of a variety that is widespread throughout the Caribbean.

Fringing Reef and Nearshore Localities Beach rock extending from the shore to a dis-

tance of approximately 50 m seaward and 5 m depth was examined in the area of Six Men's Bay (Fig. 1). No crinoids were observed although numerous echinoids and other invertebrates were present on or in the beach rock and Porites porites stands. This is in contrast to the numerous specimens of Tropiometra carinata present on the beach rock in 1974 (D. B. Macurda, Jr., and D. L. Meyer, per- sonal communication). Tropiometra is also men- tioned in a description of the site by James et al. (1977). The absence of Tropiometra may be par- tially attributed to collecting; however, the effect of environmental fluctuations in such a shallow and nearshore setting must also be considered.

The Bellairs fringing reef and nearshore areas (Figs. 1, 2) have been described by Lewis (1960), James et al. (1977), and Steam et al. (1977). Back-

Can

. J. Z

ool.

Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Uta

h St

ate

Uni

vers

ity -

Log

an o

n 02

/15/

13Fo

r pe

rson

al u

se o

nly.

LIDDELL 2415

TABLE 1. Shallow-water crinoids of the northwest coast of Barbados and their identifying features

Order Comatulidaa Family Antedonidae

Ctenantedon kinziei Meyer Ten arms, length 10 cm, slender, white to pale green; pinnules long and slender and arranged in two rows; cirri relatively

long (17 mm); cryptic or nocturnal, capable of swimming.

Family Comasteridae Comactinia echinoptera ( J . Miiller)

Ten arms, length 10-18 cm, stout proximally, arms and pinnules red (may have a mottled or spotted appearance); pinnules arranged in two planar rows; nocturnal.

Nemaster discoidea ( P . H . Carpenter) Twenty arms, length 7-15 cm (mean 8.5 cm), more slender than N. rubiginosa (1.4 mm vs. 1.8 mm mean diameter at base),

yellow-green with black abambulacral stripe, occasionally black; pinnules beaded, white with black tips, arranged in four rows (tetrad arrangement); continuously exposed.

Nenzaster rubiginosa (Pourtal&s) Twenty to 30 or more arms (mean 24), length 10-20 cm (mean 11.5 cm); arms and pinnules orange or brown to black with

black abambulacral stripe; pinnules may possess orange or yellow tips, arranged in four rows (tetrad arrangement); continuously exposed.

Family Colobometridae Analcidometra armata (Pourtales)

Ten arms, approximately 4-5 cm in length, grey-green with red bands; short pinnules arranged in two planar rows; inhabits gorgonians, capable of swimming.

Family Tropiometridae Tropiometra carinata carinata (Lamarck)

Ten arms, length 10-15 cm, brown with yellow bands; pinnules arranged in two planar rows; continuously exposed.

.See Clark (1931) for familial characteristics.

reef areas (swash zone) consist of sand bottoms with dead coral. The fringing reef has been divided into several bathymetric-ecological zones by Stearn et al. (1977) that extend seaward from the reef crest at a low slope. Crinoids appear to be absent from the back-reef areas as well as the flat terrace of the fringing reef.

At approximately 300 m from the beach, the reef terrace gives way to the seaward slope of the fring- ing reef, which begins at a depth of approximately 10m and continues to 20 or 30m at a slope of approximately 45". This slope supports a wide vari- ety of scleractinians and sponges. Nemaster dis- coidea, N . rubiginosa, and Tropiometra carinata were observed on this slope although in very low concentrations (< 0. l/m2).

Bank Reef The bank reef off Bellairs, a Holocene mantle on

a drowned Pleistocene barrier reef (Macintyre 1967), is separated from the fringing reef by a sandy trench reaching 20-30 m in depth (Fig. 2). A general description of the structure and associated fauna is provided by Ott (1975). The bank reef rises at ap- proximately 25" from 20 m on its landward side to a nearly level platform at about 13 m. This platform may be up to 100 m wide and descends at a slope of approximately 30" on its seaward side to about 36 m, where a more gently sloping sand plain be-

gins. Coral density (as determined by line tran- sects) is high on the seaward slope of the bank reef, reaching 70% coverage by live and dead coral. Coverage by live or dead coral on the level platform of the bank reef is somewhat less (54%). The greatest numbers of crinoids were encountered on the seaward slope of the bank reef. The landward slope of the bank reef supports lesser numbers of crinoids and the platform still fewer.

Crinoids present on the bank reef include Nemaster discoidea, N . rubiginosa, and Anal- cidometra armata. In addition, four specimens of the rare and normally cryptic (Meyer 1972) Ctenantedon kinziei were also observed with their arms extending from coral substrates (two diur- nally and two nocturnally). Analcidometra, which lives almost exclusively on the gorgonian Pseudo- pterogorgia sp., is found on the platform as well as the seaward slope of the bank reef, where its dis- tribution is apparently linked to the profusion of gorgonians on the platform and upper slope. The distribution of Analcidometra is patchy with cer- tain specimens of Pseudopterogorgia containing no or only 1 or 2 individuals of Analcidornetra, whereas others may contain as many as 20. The most abundant crinoids are the two Nemaster species, of which N. discoidea predominates at most depths (Table 2, Fig. 5). Combined densities of N. discoidea and N. rubiginosa over large areas

Can

. J. Z

ool.

Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Uta

h St

ate

Uni

vers

ity -

Log

an o

n 02

/15/

13Fo

r pe

rson

al u

se o

nly.

2416 CAN. J. ZOOL. VOL. 57. 1979

FIG. 3. Barbados crinoid fauna. (A) Analcidometra armara (Pourtalts) on Pseudopterogorgia sp. x 3. (B) Ctenantedon kinziei Meyer, artificially exposed. x 0.75. (C) Comactinia echinoptera ( J . Miiller) at night; note concealment of disk. ~ 0 . 5 . (D) Tropiometra c,arinata (Lamarck). x 0.25. (E) Comactinia echinoprera, detail of pinnule arrangement and tube feet; note planar pinnule array. x 4. (F) Nemaster discoidea ( P . H . Carpenter), detail of pinnule arrangement and tube feet; note tetrad pinnule arrangement and beaded nature of pinnules. x 4.

Can

. J. Z

ool.

Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Uta

h St

ate

Uni

vers

ity -

Log

an o

n 02

/15/

13Fo

r pe

rson

al u

se o

nly.

FIG. 4. Crinoid habitats. (A) Nemaster rubiginosa (Pourtales) in vertical crevice between heads of Montastrea cauernosa, M. annularis, and Siderastrea siderea. ~ 0 . 5 . (B) Nemaster rubiginosa under Colpophyllia sp. plate. x0.25. (C) Nemaster rubiginosa, detail of arm of brown form with yellow-tipped pinnules; note tetrad pinnule arrangement. x 0.75. (D) Nemaster rubiginosa with arms well extended from habitat at night. x 0.3. (E) Nemasterdiscoidea (P. H . Carpenter) under Agaricia sp. plate. x 0.8. (F) Nemaster discoidea, disk exposed at night. x 4.

Can

. J. Z

ool.

Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Uta

h St

ate

Uni

vers

ity -

Log

an o

n 02

/15/

13Fo

r pe

rson

al u

se o

nly.

2418 CAN. J . ZOOL. VOL. 5 7 , 1979

TABLE 2. Distributions of Nemaster species with depth

N. discoidea N. rubiginosa

Depth, Area, Density, Density, m m2 N m-2 N m-z

15 100 1 0.01 5 0.05 18 47 9 0.19 2 0.04 21-24 80 78 0.98 13 0.16 27 20 21 1.05 2 0.10 30 20 13 0.65 1 0.05 Total 267

on the seaward slope of the bank reef are greatest below 20 m and may reach 1. 15/m2, which is ap- proximately as high or higher than observed elsewhere in the Caribbean. Maximum numbers of crinoids censused by the author over large areas at Jamaica were 1.22/m2 and at Curacao were 0.23/m2. Me yet (1973a, 19736) found similar com- bined crinoid densities at Jamaica and Curacao.

Nemaster discoidea and N. rubiginosa were also abundant on .the seaward slope of the bank reef approximately 1 km south of the Bellairs Institute. Crinoid densities at this site exceeded those of the bank reef immediately off Bellairs in the shallower, 15-20 m, depth range where N. discoidea reached average densities of 0.58/m2 and N. rubiginosa 0.40/m2 for a combined density of 0.98/m2 over approximately 100 m2. The increase may be due, in part, to greater coral cover and thus more abundant crinoid habitats at this site. Also, this locality may suffer less disturbance from researchers and col- lectors as a result of lessened proximity to the Bel- lairs Institute.

Crinoid Microhabitats and Behavior The crinoids present may be divided into two

groups: (1) those with arms continuously extended (Nemaster discoidea, N. rubiginosa, Tropiometra carinata, and Analcidornetra arrnata) and (2) noc- turnal forms (Cornactinia echinoptera and,

D e p t h rn

15

18

21

24

2 7

30

3 3

36

FIG. 5. Bathymetric distributions of Nemaster discoidea and Nemaster rubiginosa in transect area on seaward slope of bank reef immediately off the Bellairs Research Institute. Horizontal lines at 14 and 36m indicate approximate upper and lower limits of bank reef. Dashed boundaries below 30m indicate inferred crinoid distributions as bank reef in transect area was divided into coral fingers at this depth that were not transected.

perhaps, Ctenantedon kinziei). Within the first group, Tropiometra (Fig. 3D) was too uncommon to draw conclusions about its habitat requirements at Barbados. At other Caribbean sites where Tropiometra co-occurs with N. discoidea and N. rubiginosa it appears to inhabit depth ranges and substrate types similar to those of the Nemaster species with the exception that, unlike the others, it may also extend into very shallow water (personal observation).

Analcidometra armata (Fig. 3A), as discussed earlier, chiefly inhabits the gorgonian Pseudo- pterogorgia sp., resulting in an elevation above the sea bottom of 10 to 150cm or more. In addition to inhabiting a rather narrow depth range (approxi- mately 13.5- 18 m), this small, 10-armed crinoid is clearly utilizing a restricted substrate niche, re- moved from that of the other shallow-water com- atulids, and convergent with that of some ophiuroids (e.g. certain Ophiothrix species).

The morphologically similar species of N. dis- coidea and N. rubiginosa (Figs. 3F, 4) show broadly overlapping bathymetric distributions (Fig. 5, Table 2). In addition, these congeneric species appear to overlap considerably in mi- crohabitat utilization (Fig. 6). The principal con- straints on habitat selection appear to be the re- quirements that the fleshy disk of the crinoid be concealed and the crinoid elevated into the water column for feeding purposes. The former is most likely a response to avoid predation by diurnal pre- dators as nocturnal observations indicate that many individuals of both N. discoidea and N. rubiginosa may further extend their arms or even perch upon the outsides of coral heads and expose their disks while feeding at night (Figs. 4D, 4F).

The four most common substrate morphologies utilized by both N. discoidea and N. rubiginosa are (1) vertical crevices between heads of massive dome corals such as Siderastrea siderea, Mon- tastrea cavernosa, M. annularis, and others (Fig. 4A); (2) the curled lower edge of dome corals such as M. cavernosa and M. annularis; (3) the under- sides of coral plates, largely Porites astreoides and M. annularis (Figs. 4B, 4E); and (4) overhangs formed by eroded coral rock (Fig. 6). Microhabitat selection appears to be largely random with the most common coral substrates (as determined by line transects) being selected most frequently, al- though certain substrate morphologies such as overhanging edges of M. cavernosa domes are ob- viously preferable to the open framework of corals such as Acropora cervicornis. No significant differ- ences ( P < 0.05) exist between substrate utilization patterns of the two species (based on contingency tables and the x2 statistic).

Can

. J. Z

ool.

Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Uta

h St

ate

Uni

vers

ity -

Log

an o

n 02

/15/

13Fo

r pe

rson

al u

se o

nly.

LIDDELL 2419

C R I N O I D H A B I T A T S P E R C E N T

4 0 3 0 2 0 1 0 0 1 0 2 0 3 0 '40

C O R R L K N O B S LO

V E R T . C R E V I C E w e

C O R R L F I N G E R S

C O R R L P L A T E S t CI:

C O R A L D O M E E O G E t m

R O O F u 1

n 1 s c .

N . R . N . O .

FIG. 6. Substrate utilization patterns for N. discoidea (N.D.) and N. rubiginosa (N.R.) between 15 and 23 m on the seaward slope of the bank reef immediately off the Bellairs Research Institute. Vert., vertical; Misc., miscellaneous.

For those crinoids living along the outer slope of the bank reef, there is a tendency to position the body such that the long axes of the arm arrays are oriented outward (seaward) from the reef slope (Fig. 7). Of the specimens measured, 70% were oriented parallel to or outward from the reef slope. This orientation probably allows the crinoids to take advantage of currents flowing along the reef slope for feeding.

Because of its larger overall size N. rubiginosa extends, on the average, a greater length of arm into

FIG. 7. Orientation of arm arrays of Nemaster discoidea and Nemaster rubiginosa relative to habitats on outer slope of bank reef (for 3 1 individuals). Trend or strike of reef slope is 150-330".

the water column than does N. discoidea (13.5 cm versus 8.0cm by day). Proportionately, however, the two crinoids extend nearly the same amounts of their arm arrays (approximately 65%). Also, there is some indication that at a given depth N. rubiginosa may occupy a somewhat higher position on coral substrates than N. discoidea does, al- though sample sizes for any one depth are small. The average height for both species is 10-15 cm.

Members of the second behavioral group of crinoids (cryptic or nocturnal species) occur but appear to be rare at Barbados. A few specimens of Comactinia echinoptera (Figs. 3C, 3E) have been reported from the area of Maycock's Bay, located to the North of the Bellairs Institute (Fig. 1) (D. B. Macurda, Jr., and D. L. Meyer, personal com- munication), but it is apparently not present or else is very rare on the reef off Bellairs. At Jamaica Comactinia overlaps in depth with Nemaster dis- coidea and N. rubiginosa on the forereef and oc- cupies much the same general habitats as the Nemaster species. Comactinia, however, appears to prefer sites adjacent to narrow tunnels or crevices in the coral into which it retreats during the day.

Ctenantedon kinziei (Fig. 3B) has been charac- terized as highly cryptic by Meyer (1972). At Bar- bados a total of only four specimens was observed with their arms extending from coral substrates on the seaward slope of the bank reef. It is probable that overall numbers are much higher but most specimens remain hidden and extend their arms and feed solely within caverns in the coral framework.

Discussion At Barbados, as well as elsewhere throughout

the Caribbean, crinoids (with the exception of Tropiometra) rarely occur in depths of less than 8-10 m. The enrichment of crinoids on the seaward slope of the bank reef relative to both the landward slope of the bank reef and the seaward slope of the Bellairs fringing reef may be due to increased water movement at the former site, resulting in more fa- vorable conditions for suspension feeding by the crinoids. Meyer (1973a) cites a similar increase in crinoid numbers at prominent slope breaks at Jamaica and attributes this to increased water movement at these sites. The increase in abun- dance of crinoids with depth on the bank reef (Fig. 5) may reflect increasing abundance of suitable crinoid habitat types with depth. At Jamaica and Curacao, however, transects have similarly shown optimal ranges for crinoids (based upon highest densities) to occur between 20 and 25m despite comparable coral coverage at both lesser and greater depths at these sites.

Can

. J. Z

ool.

Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Uta

h St

ate

Uni

vers

ity -

Log

an o

n 02

/15/

13Fo

r pe

rson

al u

se o

nly.

2420 CAN. J . ZOOL.

In addition to exhibiting considerable overlap in bathymetry and habitat utilization, N. rubiginosa and N. discoidea also show great similarity in food materials captured, based on preliminary studies. Such overlap in resource use by the congeneric Nemaster species, although in seeming contradic- tion with niche theory, may be due to reduced competition as a result of low crinoid densities. Predation is one means by which numbers may be so reduced. Predator control of community struc- ture has been described by Hairston et al. (1960), Slobodkin (1964), Paine (1966), and others. Al- though direct predation by fish upon crinoids has not been well documented (Clark (1921) states that fish appeared not to feed upon crinoids), there is a growing body of evidence (cited in Meyer and Macurda 1977) suggesting that fish predation upon crinoids may indeed take place. The partially con- cealed posture of some crinoids by day (Tropiometra carinata, N. rubiginosa, and N. dis- coidea) and wholly nocturnal or cryptic life mode of others (Comactinia echinoptera and Ctenantedon kinziei) suggests a response to predators.

Acknowledgements I wish to extend my appreciation to D. B.

Macurda, Jr., and D. L. Meyer, who have provided suggestions concerning this manuscript, and to S. L. Ohlhorst for assistance in various stages of the study. I also thank the staff of the Bellairs Re- search Institute of McGill University, St. James, Barbados, for use of the facilities. This study was financed by a University of Michigan (Rackham) predoctoral research grant, a Scott Turner Awards in Earth Science research grant (Department of Geology and Mineralogy, University of Michigan), and a Sigma Xi grant-in-aid of research.

CLARK, A. H. 1921. A monograph of the existing crinoids. U.S. Natl. Mus. Bull. No. 82. Part 2. pp. 1-795.

1931. A monograph of the existing crinoids. U.S. Natl. Mus. Bull. No. 82. Part 3. pp. 1-816.

1947. A monograph of the existing crinoids, U.S. Natl. Mus. Bull. No. 82. Part 4b. pp. 1-473.

1950. A monograph of the existing crinoids, U.S. Natl. Mus. Bull. No. 82. Part 4c. pp. 1-383.

HAIRSTON, N. G., F . E. SMITH, and L. B. SLOBODKIN. 1960. Community structure, population control and competition. Am. Nat. 94: 421-425.

JAMES, N. P., C. W. STEARN, and R. S, HARRISON. 1977. Field guide book to modern and Pleistocene reef carbonates, Bar- bados, W.I. Third International Coral Reef Symposium, Miami. pp. 1-30.

LEWIS, J . B. 1960. The coral reefs and coral communities of Barbados, W.I. Can. J . Zool. 38: 1133-1 145.

MACINTYRE, I. G. 1967. Submerged coral reefs, West Coast of Barbados, West Indies. Can. J . Earth Sci. 4: 461-474.

MACURDA, D. B., JR. 1973. Ecology of comatulid crinoids at Grand Bahama Island. Hydro-lab J. 2: 9-24.

1975. The bathymetry and zoogeography of shallow- water crinoids in the Bahama Islands. Hydro-lab J . 3: 5-24.

MACURDA, D. B., JR.,and D. L. MEYER. 1977. Crinoidsof West Indian coral reefs. Am. Assoc. Petrol. Geol. Stud. Geol. No. 4: 231-237.

MEYER, D. L. 1972. Ctenantedon, a new antedonid crinoid convergent with comasterids. Bull. Mar. Sci. 22: 53-66.

1973a. Distributions and living habits of comatulid crinoids near Discovery Bay, Jamaica. Bull. Mar. Sci. 23: 244-259.

19736. Feeding behavior and ecology of shallow-water unstalked crinoids (Echinodermata) in the Caribbean Sea. Mar. Biol. 22: 105-130.

MEYER, D. L., and D. B. MACURDA, JR. 1976. Distribution of shallow-water crinoids near Santa Marta, Colombia. Mitt. Inst. Colombo-Aleman Invest. Cient. 8: 141-156.

1977. Adaptive radiation of the comatulid crinoids. Paleobiology, 3: 74-82.

MEYER, D. L., C. G. MESSING, and D. B. MACURDA, JR. 1978. Zoogeography and bathymetric distribution of tropical west- e m Atlantic Crinoidea (Echinodermata). Bull. Mar. Sci. 28: 412-441.

OTT, B. 1975. Community patterns on a submerged barrier reef at Barbados, West Indies. Int. Rev. Gesamten Hydrobiol. 60: 719-736.

PAINE, R. T. 1966. Food web complexity and species diversity. Am. Nat. 100: 65-75.

SLOBODKIN, L. B. 1964. Ecological populations of Hydrida. J. Anim. Ecol. 33(Suppl.): 131-148.

STEARN, C. W., T. P. SCOFFIN, and W. MARTINDALE. 1977. Calcium carbonate budget of a fringing reef on the west coast of Barbados. Part I. Zonation and productivity. Bull. Mar. Sci. 27: 479-510.

Can

. J. Z

ool.

Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Uta

h St

ate

Uni

vers

ity -

Log

an o

n 02

/15/

13Fo

r pe

rson

al u

se o

nly.