Lecture 5 - Porifera

• Many organisms, including crabs, nudibranchs, mites, bryozoans, and fish live as commensals or parasites in sponges.
• The fibrous part comes from collagen fibrils in the intercellular matrix.

  • Spongin
• Rigid skeletons consist of needlelike spicules.

  • Calcareous
  • Siliceous
• Sponges are suspension feeders capturing food particles suspended in the water that passes through their body.
• Water flows in through incurrent pores called dermal ostia.
• It flows past the choanocytes where food particles are collected on the choancyte collar.
• It flows past the choanocytes where food particles are collected on the choanocyte collar.
• Choanocytes take in small particles by phagocytosis. Protein molecules are taken in by pinocytosis.
• Canal System

  Asconoid - the simplest canal system.

  Syconoid – tubular body and singular osculum like asconoids.

  Leuconoids – most complex, permits an increase in sponge size.
• Canal Systems

  Asconoid (Leucosolenia)

  • Choanocytes line the spongocoel.
  • Water enters through the ostia and exit through the large osculum.
• Mesohyl is the gelatinous matrix containing skeletal elements & amoeboid cells.
• Types of Cells

  • Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food.
  • Pinacocytes are thin, flat, epithelial-type cells that cover the exterior and some interior surfaces of the sponge.
• The choanocytes pass food particles to archaeocyte cells for digestion.

  The choanocytes pass food particles toarchaeocyte cells for digestion.
• Internal buds (gemmules) in freshwater sponges can remain dormant in times of

  drought.
• Most sponges are hermaphrodites meaning that each individual functions as both male and female.

  • Monoecious
  • Gametes are derived from choanocytes or sometimes archaeocytes.
• Most sponges are viviparous.

  • After fertilization, the zygote is retained and is nourished by the parent. Ciliated larvae are later released.

  Some are oviparous releasing gametes into the water.
• Calcareous sponges (Class Calcarea) have

  spicules composed of calcium carbonate.

  • Small, usually vase shaped.
  • Asconoid, syconoid, or leuconoid in structure.
• Glass sponges (Class Hexactinellida) are mostly deep sea forms.

  • Spicules are six-rayed and made of silica.
• Trabecular reticulum made of a fusion of archaeocyte pseudopodia - forms the chamber opening to spongocoel.
• Class Demospongiae contains most of the

  sponge species.

  • Spicules are siliceous, but not six-rayed.
  • Spicules may be bound together by spongin, or absent.
  • All leuconoid, mostly marine.
• Sclerospongiae

  Group of sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate.

  • Ceratoporella nicholsoni
  • Stromatospongia vermicola
• Phylum Placozoa

  • Trichoplax adhaerens is the sole species of phylum Placozoa (marine).

  -No symmetry

  -No muscular or nervous organs