BIOL 2003: Lesson 2 (Porifera)

Porifera

Porifera

• meaning pore bearing

• sessile filter feeders

• 5000-8000 species of sponges 

  • most are marine 

  • few live in brackish water

Aquiferous system

• system by which the sponge body is able to efficiently filter water

• uses flagellated collar cells (choanocytes) to move water 

Choanocytes

• flagellated collar cells used to move water for currents and feeding 

Archaeocytes

• totipotent amoeboid cells in mesohyl 

• can become cells that 

  • phagocytosize

  • make spicules

  • make spongin

  • make collagen

  • used for reproduction

Totipotent

• stem cells can give rise to any of the 220 cell types found in an embryo

Mesohyl

• the gelatinous, jelly-like matrix that fills the space between the inner and outer cell layers of a sponge

Canal systems

• Asconoid 

• Syconoid

• Leuconoid 

Asconoid

• canal system ONLY in calcarea 

• choanocyte-lined spongocoel (large, central, water-filled cavity within a sponge where water enters, flows over choanocytes, and then exits through a larger opening called the osculum)

Syconoid

• canal system ONLY in calcarea 

• choanocyte-lined canals of folded inner layers 

Leuconoid

• choanocyte lined chambers 

• in all classes 

Sponge skeletons

• collagen fibres in all sponges 

  • some have specific collagen fibres: spongin 

• spicules 

  • act as a taxanomic fingerprint, which allows us to differentiate classes, even down to the species level 

  • allows deter-ration of predators 

Porifera taxonomy

• homoscleromorpha

• calcarea

• demospongiae

• hexactinellida

Porifera feeding

• intracellular digestion via phagocytosis 

• some may be carnivorous 

  • no choanocytes 

    • microscopic hooks snare unsuspecting prey 

  • 137 carnivorous species 

Porifera symbioses

• long-term, physically close relationships between sponges and other organisms (microbial communities to larger animals)

• mutualistic

  • microbes providing nutrients and sponges offering a home

• commensalistic

  • small shrimp living in sponges 

Reproduction

• both asexual and sexual

Porifera sexual reproduction

• sperm from choanocytes released into water and taken in by another sponge 

• oocytes are released from archarocytes

  • oocytes act as an ovary 

Porifera asexual reproduction

• budding 

• dormant gemmules 

Human importance

• first non-food item harvested from the ocean 

• pharmaceutical importance

Porifera tissue

• lack true tissues and organs 

Porifera symmetry

• asymmetrical 

Porifera body cavity

• no body cavity 

Porifera development

Porifera segmentation

• no true segmentation