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