1. Kingdom: Animalia
2. Habitat: Aquatic, mostly marine, few are terrestrial
3. Habit: They are solitary or colonial.
4. Grade of organization: cellular grade of body
5. Shape: Body shape is variable, mostly cylinder shaped
6. Symmetry: Asymmetrical or radially symmetrical.
7. 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.
8. Coelom: Absent; acoelomate but spongocoel is present
9. 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).
10. Water canal system present
11. Endoskeleton: Either calcareous spicules (calcium carbonate) or siliceous spicules (silica) or sponging fibers (protein).
12. Nutrition: holozoic
13. Digestion: Intracellular
14. Nervous system: absent
15. Circulatory system: absent
16. Reproduction: Asexual: by budding or gemmule or regeneration; Sexual: gamatic fusion
17. 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
• Class 2: Hexactinellida or Hyalospongiae.
• Class 3: Demospongiae

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

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

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.

Phylum Porifera: General characteristics and Classification

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