Phylum Porifera The Sponge

Sponges are Simple, multi-cellular animal with pores Asymmetrical, no organs or tissues Central cavity with opening called a osculum Invertebrates without any specialized features Filter-feed on plankton, digestion by amebocytes Reproduction can be sexual or assexual Meroplanktonic larvae, sessile adults

Sponges are usually grouped according to the type of spicules into three classes: Class 1: Calcarea (Calcispongiae) Spicules composed principally of calcium, are monoaxon or three or four branched, Class 2: Hexactinellida (Hyalospongiae) Spicules composed principally of silica, are 6-rayed, Class 3: Demospongiae (Siliceous) Spicules or horny fibers or both are present. If spicules of silica are present in an intertidal form, the sponge probably belongs to this class. Spicules, if present, are never six-rayed.

Sponge Reproduction Sexual Produce gametes from specialized collar cells Most sponges are hermaphrodites. Broadcast spawning is when the sperm is released into the water Eggs are retained in the sponge for fertilization to take place. Larva are released to develop into sponges.

Asexual Budding Fragmentation Gemmule Formation (internal buds – rare in marine)

Gemmules Large mass of archaeocytes Formed during harsh conditions Environmentally resisitant When ready, archaeocytes are released to form new sponges.

Sponge Anatomy

Sponge Cell Wall

Spicules

TYPICAL SPONGE FEEDING Water flowing through sponges provides food and oxygen, as well as a means for waste removal. This flow is actively generated by the beating of flagella. The water movement through some sponges is aided by ambient currents passing over raised excurrent openings. This moving water creates an area of low pressure above the excurrent openings that assists in drawing water out of the sponge. Sponges are capable of regulating the amount of flow through their bodies by the constriction of various openings. The volume of water passing through a sponge can be enormous, up to 20,000 times its volume in a single 24 hour period.

In general, sponges feed by filtering bacteria from the water that passes through them. Some sponges trap roughly 90 percent of all bacteria in the water they filter. Other sponges, in particular hexactinellids, appear to be less efficient at capturing bacteria and may specialize in feeding on smaller bits of organic matter. Still other sponges harbor symbionts such as green algae, dinoflagellates, or cyanobacteria, from which they also derive nutrients.

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