Biology,  Zoology

Phylum Porifera

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Kingdom: Animalia

Habitat: Aquatic, mostly marine, few are terrestrial

Habit: They are solitary or colonial.

Grade of organization: cellular grade of body

Shape: Body shape is variable, mostly cylinder shaped

Symmetry: Asymmetrical or radially symmetrical.

Germ layer: Diploblastic animals. The adult body wall contains two layers, outer dermal layer and inner gastral layer. In between these two layers, there is a gelatinous and non-cellular mesoglea containing numerous free amoeboid cells.

Coelom: Absent; acoelomate but spongocoel is present Surface of the body has numerous perforation called ostia (for the entry of water) and a large pore at the apex called osculum (for the exit of water). Water canal system present

Endoskeleton: Either calcareous spicules (calcium carbonate) or siliceous spicules (silica) or sponging fibers (protein).

Nutrition: holozoic

Digestion: Intracellular

Nervous system: absent

Circulatory system: absent

Reproduction:

  • Asexual: by budding or gemmule or regeneration
  • Sexual: gametic fusion

Fertilization: Internal

Classification of Phylum Porifera

Based on the type of skeleton system the phylum Porifera is divided into three classes

Class 1: Calcarea or Calcispongiae

(calcarius: lime / calcium)

  • Habitat: Exclusively marine
  • Habit: Solitary or colonial nature.
  • Endoskeleton: calcareous spicules composed of calcium carbonate
  • Symmetry: Radially symmetry
  • Shape: Cylindrical shape
  • Examples: Sycon, Leucosolenia
sycon
Sycon
Leucosolenia
Leucosolenia

Class 2: Hexactinellida or Hyalospongiae:

(Hex: six, actin: ray, idea: terminal)

  • Habitat: Exclusively marine (deep sea)
  • Habit: Solitary in nature.
  • Endoskeleton: six-rayed siliceous spicules.
  • Symmetry: Radially symmetry
  • Shape: Cylindrical shape.
  • Examples: Euplectella, Hyalonemma
Hylonemma
Hylonemma
Euplectella
Euplectella

Class 3: Demospongiae

(Demos: frame)

  • Habitat: Mostly marine and some are freshwater
  • Endoskeleton: Siliceous spicules or sponging fibres or both or none.
  • The spicules are monaxon or tetraxon but never six-rayed.
  • Symmetry: asymmetrical.
  • Shape: Irregular
  • Canal system complicated.
  • Spongocoeal is totally absent.
  • Examples: Spongilla.
Spongillidae
Spongilla
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