Phylum Porifera Sponges

PHYLUM PORIFERA Sponges oldest of all animals few specialized cells sessile – can’t move

Sponge Body Plan asymmetrical wall of cells around a large, central cavity choanocytes – use flagella to create a water current through the sponge water enters through pores and leaves through the osculum (large hole in the top of the sponge) current provides a way for feeding, respiration, excretion, and circulation very simple skeleton made of spicules (spikes made from calcium carbonate or silica) spicules are made by archaeocytes (mobile cells in the sponge wall)

Spicules

Feeding filter feeders choanocytes trap food particles suspended in water and pass them to archaeocytes for digestion

Respiration, Excretion, Circulation current brings in oxygen dissolved in the water; diffuses into cells carbon dioxide and ammonia diffuse out and are carried away by current

Response no nervous system; can’t respond to stimuli some sponges produce toxins to protect themselves

Reproduction: Sexual sponges can produce both sperm and eggs (usually not at same time) sperm released into water and swim to another sponge sperm enters sponge through pores and archaeocytes carry to egg fertilization is internal larva forms from zygote and swims away to form another sponge

Reproduction: Asexual part of a sponge breaks off and forms a new sponge when it settles on the ocean floor (process called budding) gemmules may be formed when conditions are unfavorable gemmule is an archaeocyte surrounded by spicules gemmule may form a new sponge when conditions are favorable

Sponge Ecology sponges often live with other animals provide a home for many many have a symbiotic relationship with photosynthetic organisms form a fundamental part of coral reefs