Classification of Phylum Porifera

• Phylum Porifera

  1.Class Calcarea

  2.Class Hexactinellida

  3.Class Demospongiae

  4.Class Homoscleromorpha
• Class Calcarea

  • with calcium carbonate spicules that often form a fringe around osculum

  • CaCO3 spicules needle-shaped or 3- or 4-rayed

  • all 3 body plans exhibited

  • mostly small in size (<15 cm)

  • form irregular masses

  • never contains spongin

  • restricted to shallow water and strictly marine

  • larvae: coeloblastula, amphiblastula

  
• Class Hexactinellida

  • Hex (six) + aktis (ray)

  • glass sponges

  • six-rayed, siliceous spicules extending at right angles from a central point; often united to form a network

  • cylindrical or funnel shaped body

  • sycon or leuconoid body plan

  • entire sponge is syncytial

  • lacks contractile elements (no pinacoderm)

  • found in deep marine water

  • larvae: parenchymella (non-flagellated)
• Venus’ flower basket

  (Euplectella aspergillum)

  
• Spicules of silica and fused to form a lattice-like skeleton cup or vase-shaped with well-developed spongocoel

  (a) most beautiful example is Euplectella venus flower basket

  (b) chiefly live in 500-1000 meter depth

  (c) are syconoid sponges

  (d) all are marine

  (e) may have commensal relationship with shrimp - where a male and female live inside the sponge; get trapped inside when they out-grow the pores of sponge

  (f) the parenchymella larva of glass sponges is typically non-flagellated—instead, larvae are ciliated; only cells in the larval midsection are flagellated
• Class Demospongiae

  • Desmos (chain, tie or bond) + spongos (sponge)

  • 80% of sponges belong to this class

  • made up of spongin fibers or siliceous spicules.

  • spicules composed of spongin/silica but never calcium carbonate

  • leuconoid

  • all freshwater sponges belong here (contains contractile vacuoles)

  • variously shaped, some are huge

  • larvae: coeloblastula, parenchymella
• Class Homoscleromorpha

  • massive or encrusting in form

  • most species do not have spicules

  • if present, entirely silicious spicules and generally of the same size (not six-rayed but usually tetractines)

  • have little mesohyl

  • all have clear, distinct basal membrane underlying the epithelium•all epithelial cells have cilia

  • larvae: amphiblastula (flagellated)
• Type IV collagen – main component of basement membrane structures have been detected in all multicellular animal species, except sponges; only Class Homoscleromorpha have this type of collagen