Phylum Porifera

-About 8,000 species, mostly marine

Sponge Features

  • No organ systems (no digestive system, reproductive system, nervous sensory, excretory systems, etc.)
  • Most are asymmetrical
  • Have highly specialized cells
  • Many sponge cells are “totipotent
  • Cells can be dissociated separated, and then they will reaggregate
  • Studies of sponges have shed light on the evolutionary origin of cell-mediated immunity, and even the functioning of the major histocompatability complex of the human immune system

Gemmule- a tough-coated dormant cluster of embryonic cells produced by a freshwater sponge to survive poor living conditions such as cold temperatures

Acsonoid, Syncoid, and Leuconoid are all sponge body shapes

Porifera Diversity

  • Class Calcarea
  • Class Demospongiae
  • Class Hextactinellida
  • (class Homoscleromorpha)

Sponge Reproduction

  • Asexual – buds breaking off or fragmentation, gemmules (for freshwater)
  • Sexual– Internal fertilization, monoecious (sequential hermaphrodites)
    • Sperm is produced by choanocytes, exits via the oscula, captured by another sponges choanocytes, transferred to the mesohyl where eggs are fertilized, embryo develops in the mesohyl, then larvae breaks out into spongocoel, exits through the oscula

-Commensalism relationships with lots of organisms

-Mutualistic associations with algae or cyanobacteria give sponges color and nutrition

Sponges can use physical or chemical defenses

  • Manufacture a broad spectrum of biotoxins (allelochemicals)
  • Use “chemical warfare” ( allelopathy) to compete for space with other benthic organisms
  • Some have been isolated for their potential pharmaceutical use