Porifera Zoology lecture 18 February 2010 Winslow
Hickman, et al. 2008. Integrated Principles of Zoology, 14th ed., McGraw-Hill, NY; Ch. 12 pp 246, 248-256
Phylum Porifera
Multicellularity, cell-tissue level of organization
Mostly marine, some freshwater
Radially symmetrical or asymmetrical
Flagellated larvae (parenchymula) free-swimming, adults sessile
Often grow on coral reefs or other animals
Host invertebrate commensals & parasites
Maintain internal water currents to obtain food
Intracellular digestion by archaeocytes
Excretion & gas exchange by diffusion
No nervous system or sensory organs
Asexual reproduction by buds or gemmules
Sexual reproduction by eggs & sperm (mostly monoecious)
Internal (choanocytes carry sperm to oocytes) or external fertilization
Epidermis of flat pinacocytes--regulate surface area, water flow, protect sponge
Skeleton--spicules (Si or Ca), collagen, spongin
Contractile collencytes secrete collagen
Spongocytes secrete spongin
Schlerocytes secrete spicules
Mesohyl ("mesoglea", "mesenchyme") connective tissue
Class Calcarea
Calcareous spicules
Variable canal system
Asconoid--flagellated spongocoel, porocytes
Syconoid--flagellated canals
Leuconoid--flagellated chambers, multiple oscula, large body size
Class Hexactinellida--glass sponges
Mostly deep ocean species
6-rayed siliceous spicules
Syncytial trabecular reticulum
Syconoid or leuconoid canal system
Flagellated chambers with primary & secondary reticula
Choanoblasts & collar bodies
Class Demospongiae
Most sponge species, marine & freshwater species
Includes commercial bath sponges
Si spicules &/or spongin
Leuconoid canal system