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

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