SURVEY OF THE ANIMAL KINGDOM

PHYLUM PORIFERA

• OVERVIEW– Most primitive of the metazoans– Over 7,000 species, approximately 40 species that

occur in local waters– 2% of all sponges are freshwater, none are

terrestrial– Sponges occur in shallow water habitats and vary

widely in size (up to 1 meter high) and shape– All sponges are sessile filter feeders

PHYLUM PORIFERA

• CHARACTERISTICS– Cellular level of organization, without true tissues– Adults exhibit radial symmetry or are

asymmetrical– Possess totipotent cells– Possess unique flagellated cells (choanocytes)

that create water flow through a water current system

PHYLUM PORIFERA

• CHARACTERISTICS– Outer and inner cell layers lack a basement

membrane– Outer and inner cell layers divided by a noncellular

layer (mesohyl) that contains some cells and skeletal material --- collagen

– Body support (“skeleton”) provided by spicules composed of calcium carbonate (CaCO3)or silicon dioxide (SiO2)

PHYLUM PORIFERA

• AMOEBOCYTES– Located in the mesohyl, with different roles• Phagocytic – role in digestion• Archeocytes – totipotent• Sclerocytes – spicule production• Spongocytes – secrete spongin• Collenocytes – collagen of mesohyl

PHYLUM PORIFERA

• REPRODUCTION– Asexual budding– Regeneration from broken pieces– Sexual• Hermaphroditic (some dioecious)• Eggs --- archeocytes or choanocytes• Sperm --- choanocytes• Neighboring sponges are fertilized by sperm entering

through the ostia

PHYLUM PORIFERA

• CLASSIFICATION– Class Calcarea– Class Demospongiae– Class Hexactinellida

PHYLUM PORIFERA

• CLASS CALCAREA– Have spicules made of

calcium carbonate– Mostly small in size (<15

cm), and form irregular masses

– NEVER contain spongin, restricted to shallow water, and strictly marine

PHYLUM PORIFERA

• CLASS DEMOSPONGIAE– Have spicules made of

silicon dioxide or spongin or combination of both

– Most sponges belong to this class (90%)

– Mostly found on the continental shelf

– Spongia spp. (bath sponge)

PHYLUM PORIFERA

• CLASS HEXACTINELLIDA– Spicules are made of silica– Usually found in deep water on soft substrates in the

tropics 200-1,000 meters– Spicules are six pointed and have a lattice-like structure– Cup, vase or urn shape– Euplectella spp. (deep sea glass sponge)