PHYLUM PORIFERA
 The name is from the Greek por - "small hole" and fer - "to bear".
 Sponges, as we already have mentioned, lack true tissues or a true plane of body symmetry
 Five types of cells:
1. choanocytes - "collar cells"
2. pinacocytes - form the epithelium
3. porocytes - barrel-shaped cells form the incurrent pores
4. amoebocytes - roving scavenger cells that participate in feeding (can become whatever
the sponge needs)
5. sclerocytes – cells that make spicules the skeletal elements, SPICULES

If you disrupt the cells of a sponge, they can form a new sponge!

Aquiferous System
o incurrent pores (OSTIA) draw water into spongocoel
o water exits via the OSCULUM
The external "skin," composed of pinacocytes
Between these layers of pinacocytes is the gelatinous MESOHYL where amoebocytes roam from
choanocyte to choanocyte, collecting nutrients from them and distributing them to other cells.
Internal space is called the SPONGOCOEL (or sometimes the "atrium")




General anatomy comes in three flavors, each a more complex version of the previous:
o asconoid - sac shaped
o syconoid - folded asconoid – “s” shaped walls
o leuconoid - folded syconoid – maze-like

Most sponges are hermaphroditic, producing both sperm and eggs (sperm derived from
choanocytes and eggs from specialized amoebocytes called archaeocytes)
Larval form is a ciliated ball of cells (a blastula) called a parenchymula (most common, though
there are two other types).
This remains free-living for a while, and then settles on the substrate on one end and develops into
an adult sponge





No evidence of any form of nervous system or sense organs
Sponges can respond to environmental conditions by opening and closing incurrent and excurrent
canals, constricting canal lumen size, reversing water flow, etc.
These responses are mediated at the cellular level, and there is cooperation among cells.













SPONGE REPRODUCTION – Sponges reproduce both sexually and asexually
SEXUAL REPRODUCTION
The choanocyte makes the sperm and releases it into the water flow.
It is hopefully transported by the current to a neighboring sponge and is captured by its
choanocyte.
o If it is the same species  packaged and used for reproduction
o If it is a different species  “eaten”
3. The choanocyte loses its flagellum and carries the sperm to an egg
4. Larva will develop in the mesohyl, grow, and rupture out of the sponge
o Depending on the species, the larva will be mobile for hours or days
o The sponge loses its mobility and becomes a sessile sponge
ASEXUAL REPRODUCTION
Budding
o An adult sponge will experience an outgrowth that will continue to enlarge.
o Eventually, gravity will pull down the growth, detaching it.
o The individual will be genetically identical to the adult
Gemmule
o Typically with freshwater sponges
o During harsh times (drought or cold weather), a sponge will isolate a few amoebocytes and
barricade them with spicules.
o The original sponge may perish, but when better conditions arrive, the “spiky seed” will
emerge and grow
Regeneration
o Also called somatic embryogenesis
o If a sponge is broken into pieces, the majority of the pieces will regrow into new
sponges…all genetically identical to the parent sponge
Recognition Protein
o When a sponge is broken into pieces, this special protein allows the pieces to migrate back
to their original sponge or migrate to the nearest sponge of the same species
ECOLOGICAL IMPORTANCE
o Purify water
o Recycle nutrients
o Serve as an environmental barometer
o Antibacterial and antifungal compounds
How humans use sponges:
o Painting of ancient frescos
o Bathing
o Painting
o Gas mask
o Burned to release iodine to sterilize rooms
o Absorb fluid during surgery
o Reinforce pottery
There are three main types of sponges:
Asconoid
Spongin is a special
protein that gives the
sponge support and
flexibility.
Syconoid
Leucanoid
The sponge body supported by a hard skeleton composed of spicules.