BIO2231 Lecture Notes - Lecture 3: Benthos, Demosponge, Hexactinellid

Phylum Porifera: Sponges

• All aquatic, mostly marine

• No symmetry, cell aggregates, no germ layers, only non eumetazoan animal

• Use choanocyte to create water current (one flagella on each), water moves out through

osculum (also involved in feeding)

• Embedded in protein matrix; mesohyl

• Sessile adults (usually attached to rocks/shells)

• Filter/suspension feeder

• Most abundant sponges are; Demonspongia, members of which are leuconoid

• Body wall composed of – outer layer= Pinaocderm; pinacocytes (can digest food by

phagocytosis), porocytes

- inner flagellated layer= Choanoderm; choanocytes

- connective layer= Mesohyl; archeocytes (can phagocytize

particles), spongocytes, oocytes and spermatocytes (reproductive)

• Asexual reproduction; fragmentation, external buds, gemmules/internal buds

• Sexual reproduction; monoecious (both male and female sex cells in one individual)

• Most are viviparous, rest are oviparous

• Asconoid; simplest organization, sponge draws water through pores by beating flagella on

cross sectional area.

• Adaptations of sponges to a stationary mode of existence include; The absence of an anterior

end, Circulation of water through the body by various bodily processes and Hermaphroditism

Class Calcarea

-spicules of crystalline calcium

carbonate with 1/3/4 rays

-mainly asconoid

-typically solitary tube/groups each

with a terminal osculum

-entirely marine (shallow waters, tidal

Leucosolenia (asconoid)

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