General Characteristics of Phylum Porifera

General Characteristics of Phylum Porifera

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General Characteristics of Phylum Porifera

General Characteristics of Phylum Porifera

Some of the characteristics are:

  1. Porifera are all aquatic, mostly marine except one family Spongillidae which lives in freshwater.
  2. They are sessile and sedentary and grow like plants.
  3. The body shape is vase or cylinder-like, asymmetrical or radially symmetrical.
  4. The body surface is perforated by numerous pores, the Ostia through which water enters the body and one or more large openings, the oscula by which the water exists.
  5. The multicellular organism with the cellular level of body organization. No distinct tissues or organs.
  6. They consist of outer ectoderm and inner endoderm with an intermediate layer of mesenchyme, therefore, diploblastic
  7. The interior space of the body is either hollow or permeated by numerous canals lined with choanocytes. The interior space of the sponge body is called spongocoel.
  8. Characteristic skeleton consisting of either fine flexible spongin fibers, siliceous spicules or calcareous spicules.
  9. Mouth absent, digestion intracellular.
  10. Excretory and respiratory organs are absent.
  11. Contractile vacuoles are present in some freshwater forms.
  12. The nervous and sensory cells are probably not differentiated.
  13. The primitive nervous system of neuron arranged in a definite network of bipolar or multipolar cells in some, but is of doubtful status.
  14. The sponges are monoecious.
  15. Reproduction occurs by both sexual and asexual methods.
  16. Asexual reproduction occurs by buds and gemmules.
  17. The sponge possesses a high power of regeneration.
  18. Sexual reproduction occurs via ova and sperms.
  19. All sponges are hermaphrodite.
  20. Fertilization is internal but cross-fertilization can occur.
  21. Cleavage holoblastic.
  22. Development is indirect through a free-swimming ciliated larva called amphiblastula or parenchymula.
  23. The organization of sponges are grouped into three types which are ascon type, sycon type, and leuconoid type, due to simple and complex forms.
  24. Examples: Clathrina, Sycon, Grantia, Euplectella, Hyalonema, Oscarella, Plakina, Thenea, Cliona, Halichondria, Cladorhiza, Spongilla, Euspondia, etc.

References

  1. Kotpal RL. 2017. Modern Text Book of Zoology- Invertebrates. 11th Edition. Rastogi Publications.
  2. Jordan EL and Verma PS. 2018. Invertebrate Zoology. 14th Edition. S Chand Publishing.

General Characteristics of Phylum Porifera


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