bio1120_phylum_porifera 1/25/06
BIOL 1120 REEDER
PHYLUM PORIFERA (pore-bearing)
I. General Characteristics
A. Ancient group with extensive fossil record; seem to be outside the line of evolution leading from the
protozoa: in other words, a dead end branch
1. Members do have a flagellated larva in their life cycle that resembles colonial protozoa and also
utilizes phagocytic method of nutrition
* B. "Pore-bearing": bodies composed of a myriad of tiny pores and canals comprising a filter feeding
system
C. No specific body plan
D. Aquatic: mostly marine, some freshwater forms; have no real predators so are very successful; 5,000
species
E. Sessile as adult; free swimming, flagellated larva
F. Some radial symmetry; some asymmetrical
* G. No Tissue development: no germ layers, therefore, no true tissues nor organ development
1. Multicellular with some cell specialization: resembles colonial protozoa
a. Epidermis: outer layer of thin flat cells
b. Mesogel: gelatinous layer between cell layers; contains free cells and skeleton of
spicules(endoskeleton)
1) Amoebocytes: Free amoeboid cells in mesogel that migrate within the mesogel
functioning to complete digestion, form reproductive cells, and secrete the spicules
c. gastral epithelium: lines the spongocoel
* d. Choanocytes: inner lining of "collar cells" in the radial canals primarily; flagellated cells that
maintain a water current into the canal network; traps and phagocytizes food, thus beginning
the digestive process; represents primitive intracellular digestive system
H. Structural characteristics
1. Pores (ostia): entrance into the canal system
2. Spongocoel: single, tubular central canal
3. Osculum: exit from osculum to the exterior; a single opening
I. Skeleton: endoskeleton for rigidity found in the mesogel
1. Spongin: fibrous protein fibers
}often combined
2. Spicules: limy (CaC03) or siliceous
J. Nutrition: feed on fine detritus particles, planktonic organisms and bacteria
1. Filter feeders: from ostia into the canal system -----> into the spongocoel -----> out osculum
a. Activity involves choanocytes and amoebocytes: feed on plankton (microscopic protists)
K. Reproduction
1. Asexual
a. Regeneration: sponge parts lost by injury may be replaced; "sponge farms
b. Budding: bud growth either separates from original sponge as growth proceeds or remains
attached to form a colony
c. Gemmules (internal buds): some freshwater forms and others form these groups of cells that
serve to carry the species through adverse conditions (cold, drought, etc.); they contain stored
food surrounded by a resistant cover; when the sponge dies, gemmules drop out to survive
until favorable conditions return for new sponge growth
2. Sexual: monoecious and dioecious forms
a. Ova and sperm produced by same sponge (hermaphroditic) or separate sexes by amoebocytes
b. Ovum must be fertilized by sperm of another sponge (no self fertilization)
c. Developing egg becomes a free swimming, flagellated larva for a few hours, then settles,
attaches and grows into a young sponge