Subtopic: Phylum Porifera

Gen­er­al Char­ac­ter­is­tics:

• Com­mon Name: Sponges
• Habi­tat: Gen­er­al­ly marine (most­ly salt­wa­ter), some fresh­wa­ter species exist.
• Sym­me­try: Most­ly asym­met­ri­cal (no defined body shape).
• Orga­ni­za­tion: Prim­i­tive mul­ti­cel­lu­lar ani­mals with cel­lu­lar lev­el of orga­ni­za­tion (cells per­form spe­cif­ic func­tions, but no true tis­sues or organs).

Water Trans­port Sys­tem (Canal Sys­tem):

• Func­tion: Essen­tial for food gath­er­ing, res­pi­ra­to­ry exchange (oxy­gen and car­bon diox­ide), and waste removal.
• Path­way:
  • Water enters through numer­ous small pores called ostia (in the body wall).
  • Water flows into a cen­tral cav­i­ty called the spon­go­coel.
  • Water exits the spon­go­coel through a larg­er open­ing called the oscu­lum.
• Choanocytes (Col­lar Cells): Spe­cial­ized fla­gel­lat­ed cells that line the spon­go­coel and canals. Their fla­gel­la cre­ate water cur­rents and trap food par­ti­cles.

Oth­er Phys­i­o­log­i­cal Process­es:

• Diges­tion: Intra­cel­lu­lar (occurs with­in indi­vid­ual cells).
• Skele­ton: Pro­vides struc­tur­al sup­port. Com­posed of:
  • Spicules: Small, nee­dle-like or star-shaped struc­tures made of cal­ci­um car­bon­ate or sil­i­ca.
  • Spon­gin Fibers: Tough, flex­i­ble pro­tein fibers.

Repro­duc­tion:

• Sex­es: Not sep­a­rate (her­maph­ro­dite) — both eggs and sperm are pro­duced by the same indi­vid­ual.
• Asex­u­al Repro­duc­tion:
  • Frag­men­ta­tion: A piece of the sponge breaks off and can devel­op into a new indi­vid­ual.
• Sex­u­al Repro­duc­tion:
  • Gametes: Eggs and sperm are pro­duced.
  • Fer­til­iza­tion: Inter­nal (occurs with­in the sponge’s body).
  • Devel­op­ment: Indi­rect, mean­ing there is a lar­val stage that is mor­pho­log­i­cal­ly dis­tinct from the adult sponge. The lar­va is free-swim­ming and even­tu­al­ly set­tles and meta­mor­phoses into an adult.

Exam­ples: Sycon (Scypha), Spongilla (Fresh water sponge) and Euspongia(Bath sponge).