BIOL172 Exam 2: Sponges

Porifera

Sponges

Invertebrates (most are marine species)

Share a putative recent common ancestor with choanoflagellates

No true tissues (no gastrulation: no germ layers)

Specialized cells forming functional tissues

Sponge Larvae

Flagellate

Adult Sponge

Sessile

Diffusion

Gas exchange, circulaton, and excretion

Porifera lack complex... systems (4)

Digestive, respiratory, circulatory, and nervous systems

Digestive Process

Intracellular

- break down food in cells rather than a digestive cavity

Food: bacteria, tiny crustaceans

Reproduction

Sexual and asexual

Sexual:

- gamete formation

- monoecious (both female and male), some hermaphroditic (produce eggs and sperm)

Asexual:

- fragmentation / budding

- gemmules (resistant / dormant structures, only freshwater species)

Gemmules

Specialized, asexual, internal reproductive buds produced by freshwater sponges / Porifera to survive harsh conditions like freezing or drought

Allow sponges to survive in a dormant state and later develop into new adults when environmental conditions improve.

Lophocyte / Collenocyte

Produce a collagen-like protein that supports the mesohyl

Amoebocyte

Delivers nutrients to cells and differentiates into other cell types

Mesohyl

Jelly like substance which contains collagenous fibres

Choanocyte

Generates water current and filters food particles from water

Spermatozoa

Body Cells and Structure

Spongin fibres made by spongocytes

Spicules partially surrounded by spongin (made by sclerocytes)

Choanocytes

Choanocytes

Collar cells that line the body cavity and have flagella that circulate water in sponges

Ascon Sponge

has no folding to its body wall and is simply a hollow tube just a few cells thick with a prominent osculum at the top; generally small

Sycon Sponge

Simple infolding to body walls; increased surface-to-volume ration allows them to be larger

Leucon Sponge

Vast majority of sponges living today are this type; most complex type with body folds that are themselves folded resulting in chambers connected by canals