Phylum: PoriferaPhylum: Porifera

The SpongesThe Sponges

D. Class Calcarea (Calcispongiae)D. Class Calcarea (Calcispongiae)1. These are calcareous sponges with 1. These are calcareous sponges with spicules of calcium carbonate.spicules of calcium carbonate.

2. The spicules are straight or have 2. The spicules are straight or have three or four rays.three or four rays.

E. Class Hexactinellida E. Class Hexactinellida (Hyalospongiae)(Hyalospongiae)

1. These are glass sponges with six-1. These are glass sponges with six-rayed spicules of silica.rayed spicules of silica.

2. Nearly all are deep-sea forms; most 2. Nearly all are deep-sea forms; most are radially symmetrical.are radially symmetrical.

F. Class DemospongiaeF. Class Demospongiae1. This class contains 95% of living 1. This class contains 95% of living sponge species.sponge species.

2. Spicules are siliceous but not six 2. Spicules are siliceous but not six rayed; they may be absent or bound rayed; they may be absent or bound together by spongin.together by spongin.

3. All are leuconoid and all are marine 3. All are leuconoid and all are marine except for Spongillidae, the freshwater except for Spongillidae, the freshwater sponges.sponges.

12.1. Advent of 12.1. Advent of MulticellularityMulticellularity

A. AdvantagesA. Advantages

1. Nature1. Nature’’s experiments with s experiments with larger organisms without larger organisms without cellular differentiation are cellular differentiation are limited.limited.

2. Increasing the size of a cell 2. Increasing the size of a cell causes problems of exchange; causes problems of exchange; multicellularity avoids surface-multicellularity avoids surface-to-mass problemsto-mass problems..

3. Cell assemblages in sponges 3. Cell assemblages in sponges are distinct from other animals; are distinct from other animals; but molecular evidence shows but molecular evidence shows common ancestry.common ancestry.

12.5. Phylum Porifera12.5. Phylum Porifera

A.A. General FeaturesGeneral Features

1. Porifera means "pore-bearing"; their sac-like 1. Porifera means "pore-bearing"; their sac-like bodies are perforated by many pores.bodies are perforated by many pores.

2. They are 2. They are sessilesessile and depend on water and depend on water currents to bring in food and oxygen and currents to bring in food and oxygen and carry away wastes.carry away wastes.

3. Their body is a mass of cells embedded in 3. Their body is a mass of cells embedded in gelatinous matrix and stiffened by spicules of gelatinous matrix and stiffened by spicules of calcium carbonate or silica and collagen.calcium carbonate or silica and collagen.

4. They have 4. They have no organs or tissuesno organs or tissues; cells are ; cells are somewhat independent.somewhat independent.

5. Being sessile, they have no nervous or sense 5. Being sessile, they have no nervous or sense organs and have simplest of contractile organs and have simplest of contractile elements.elements.

6. They are not from the mainstream of animal 6. They are not from the mainstream of animal evolution; thus they are often called Parazoa.evolution; thus they are often called Parazoa.

7. Most of the 5000 species are marine; about 7. Most of the 5000 species are marine; about 150 are freshwater.150 are freshwater.

8. Morphology changes with substrate, calmness 8. Morphology changes with substrate, calmness of water, etc.of water, etc.

9. Sponges are ancient; fossils extend to 9. Sponges are ancient; fossils extend to Cambrian or earlier.Cambrian or earlier.

B. Form and FunctionB. Form and Function

1. Body openings 1. Body openings consist of small consist of small incurrent pores or incurrent pores or ostia ostia and a few excurrent and a few excurrent osculaoscula..

2. Openings are 2. Openings are connected by a system connected by a system of canals; water passes of canals; water passes from ostia to osculum.from ostia to osculum.

3. 3. Choanocytes Choanocytes or or flagellated collar cells flagellated collar cells line some of the canals.line some of the canals.

a. They keep the a. They keep the current flowing by current flowing by beating of flagella.beating of flagella.

b. They trap and b. They trap and phagocytizephagocytize food food particles passing by.particles passing by.

4. The framework of the 4. The framework of the sponge is composed of sponge is composed of needle-like calcareous needle-like calcareous

or or siliceous spicules or siliceous spicules or organic spongin fibers.organic spongin fibers.

5.5. There are three There are three types of canal types of canal systems.systems.a. a. AsconoidsAsconoids: : Flagellated Flagellated SpongocoelsSpongocoels

1) Asconoids are 1) Asconoids are simplest; they simplest; they are small and are small and tube-shaped.tube-shaped.

2) Water enters a 2) Water enters a large cavity, the large cavity, the spongocoel, lined spongocoel, lined with with choanocytes.choanocytes.

3) Choanocyte 3) Choanocyte flagella pull flagella pull water through.water through.

4) All Calcarea are 4) All Calcarea are asconoids: asconoids: Leucosolenia Leucosolenia and and Clathrina Clathrina are are examples.examples.

b. b. SyconoidsSyconoids: Flagellated : Flagellated CanalsCanals

1) They resemble asconoids but 1) They resemble asconoids but are bigger with a thicker body are bigger with a thicker body wall.wall.

2) The wall contains 2) The wall contains choanocyte-lined radial canals choanocyte-lined radial canals that empty into the spongocoel. that empty into the spongocoel. (Fig.12-7)(Fig.12-7)

3) Water entering filters through 3) Water entering filters through tiny openings.tiny openings.

4) Food is digested by 4) Food is digested by choanocytes.choanocytes.

5) Flagella force the water 5) Flagella force the water through internal pores into the through internal pores into the spongocoel and out the spongocoel and out the osculum.osculum.

6) The flagellated canals form 6) The flagellated canals form by evagination of the body wall; by evagination of the body wall; this is developmental evidence this is developmental evidence of being derived from asconoid of being derived from asconoid ancestors.ancestors.

7) Classes Calcarea and 7) Classes Calcarea and Hexactinellida have species that Hexactinellida have species that are syconoid. are syconoid.

c. c. LeuconoidsLeuconoids: : Flagellated Flagellated ChambersChambers

1) These are most 1) These are most complex and are larger complex and are larger with many oscula. (Fig. with many oscula. (Fig. 12-8)12-8)

2) Clusters of 2) Clusters of flagellated chambers flagellated chambers are filled from incurrent are filled from incurrent canals, discharge to canals, discharge to excurrent canals.excurrent canals.

3) Most sponges are 3) Most sponges are leuconoid; it is seen in leuconoid; it is seen in most Calcarea and in all most Calcarea and in all other classes.other classes.

4) 4) This system This system increases flagellated increases flagellated surfaces compared to surfaces compared to volume; more collar volume; more collar cells can meet food cells can meet food demands. Its all demands. Its all about surface-to-about surface-to-volume ratios and volume ratios and energy extraction!!!energy extraction!!!

6. Types of Cells6. Types of Cells

a. Sponge a. Sponge cells are cells are arranged in arranged in a a gelatinous gelatinous matrix matrix called called mesohylmesohyl..

b. b. PinacocytesPinacocytes

1) These cells form 1) These cells form the pinacoderm; the pinacoderm; they are flat they are flat epithelial-like cells.epithelial-like cells.

2) Pinacocytes are 2) Pinacocytes are somewhat somewhat contractile.contractile.

c. c. ChoanocytesChoanocytes

1) These are oval cells 1) These are oval cells with one end with one end embedded in mesohyl.embedded in mesohyl.

2) The exposed end 2) The exposed end has a flagellum has a flagellum surrounded by a collar.surrounded by a collar.

3) A collar is made of a 3) A collar is made of a row of microvilli row of microvilli forming a fine filtering forming a fine filtering device to strain food. device to strain food. (Fig. 12-10)(Fig. 12-10)

4) Particles too large 4) Particles too large to enter the collar to enter the collar are trapped in are trapped in mucous and moved mucous and moved to the choanocyte to the choanocyte where they are where they are phagocytized.phagocytized.

5) Food engulfed by 5) Food engulfed by choanocytes is choanocytes is passed to passed to neighboring neighboring archaeocytes for archaeocytes for digestion.digestion.

3) A collar is made of a row 3) A collar is made of a row of microvilli forming a fine of microvilli forming a fine filtering device to strain filtering device to strain food. (Fig. 12-10)food. (Fig. 12-10)

4) Particles too large to 4) Particles too large to enter the collar are enter the collar are trapped in mucous and trapped in mucous and moved to the choanocyte moved to the choanocyte where they are where they are phagocytized.phagocytized.

5) Food engulfed by 5) Food engulfed by choanocytes is passed to choanocytes is passed to neighboring archaeocytes neighboring archaeocytes for digestion.for digestion.

d. d. Amoebocytes Amoebocytes (Archaeocyte)(Archaeocyte)

1) These cells move 1) These cells move about in the mesohyl.about in the mesohyl.

2) They phagocytize 2) They phagocytize particles in the particles in the pinacoderm.pinacoderm.

3) They can 3) They can differentiate into any differentiate into any other type of cell.other type of cell.

4) Those called 4) Those called sclerocytes secrete sclerocytes secrete spicules.spicules.

5) Spongocytes secrete 5) Spongocytes secrete spongin.spongin.

6) Collencytes secrete 6) Collencytes secrete fibrillar collagen.fibrillar collagen.

7) Lophocytes secrete 7) Lophocytes secrete lots of collagen but lots of collagen but may look like may look like collencytes.collencytes.

e. e. Types of SkeletonsTypes of Skeletons

1) Collagen fibrils are 1) Collagen fibrils are found throughout found throughout intercellular matrix of intercellular matrix of sponges.sponges.

2) Various 2) Various Demospongiae Demospongiae secrete a form of secrete a form of collagen called collagen called sponginspongin..

3) Demospongiae also 3) Demospongiae also secrete some secrete some siliceous spicules.siliceous spicules.

4) Calcareous 4) Calcareous sponges secrete sponges secrete spicules of crystalline spicules of crystalline calcium carbonate.calcium carbonate.

5) Glass sponges 5) Glass sponges have siliceous have siliceous spicules with six rays.spicules with six rays.

6) Spicule patterns 6) Spicule patterns are important are important classification features.classification features.

7. Sponge Physiology7. Sponge Physiology

a. Filtration Ratesa. Filtration Rates

1) 1) LeuconiaLeuconia, a small , a small sponge, has 81,000 sponge, has 81,000 incurrent canals.incurrent canals.

2) It would have more 2) It would have more than than two milliontwo million flagellated chambers.flagellated chambers.

3.)Expulsion is strong 3.)Expulsion is strong enough to disperse enough to disperse wastes.wastes.

4) Some large sponges 4) Some large sponges can filter 1500 liters of can filter 1500 liters of water a day.water a day.

b. Particles are filtered b. Particles are filtered nonselectively; nonselectively; choanocytes phagocytize choanocytes phagocytize 80%.80%.

c. Digestion is completely c. Digestion is completely intracellular, primarily by intracellular, primarily by amoebocytes.amoebocytes.

d. There are no excretory or d. There are no excretory or respiratory organs; respiratory organs; diffusion suffices.diffusion suffices.

e. The only movements are e. The only movements are very slow opening and very slow opening and closing of pores; nerve closing of pores; nerve cells are not present.cells are not present.

C. ReproductionC. Reproduction

1. Asexual Reproduction1. Asexual Reproduction

a. External buds are small individuals that a. External buds are small individuals that break off after attaining a certain size.break off after attaining a certain size.

b. Internal buds or gemmules are formed by b. Internal buds or gemmules are formed by amoebocytes that collect in mesohyl and are amoebocytes that collect in mesohyl and are coated with tough spongin and spicules; they coated with tough spongin and spicules; they survive drought, freezing, etc, and contain survive drought, freezing, etc, and contain amoebocytes.amoebocytes.

2. Sexual Reproduction2. Sexual Reproduction

a. Most are a. Most are monoeciousmonoecious with both male and with both male and female sex cells in one individual.female sex cells in one individual.

b. Sperm arise from transformed choanocytes.b. Sperm arise from transformed choanocytes.

c. In some Demospongiae and Calcarea, c. In some Demospongiae and Calcarea, oocytes develop from oocytes develop from choanocyteschoanocytes; others ; others derive them from derive them from archaeocytesarchaeocytes..

d. Sponges provide nourishment to the zygote d. Sponges provide nourishment to the zygote until it is released as a ciliated larva.until it is released as a ciliated larva.

e. In some species, sperm are released out into e. In some species, sperm are released out into the water where they enter the pores of other the water where they enter the pores of other sponges.sponges.

f. Choanocytes phagocytize the sperm and f. Choanocytes phagocytize the sperm and transfer them to carrier cells that carry sperm transfer them to carrier cells that carry sperm through mesohyl to oocytes.through mesohyl to oocytes.

g. Some release both sperm and oocytes into g. Some release both sperm and oocytes into water.water.