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Animal Kingdom~Sponges
Phylum~Porifera/Parazoa/Sponges
*All sponges are aquatic,mostly marine,fresh water.
*These are primitive multicellular animals and have cellular level of organisation. Sponges have a water transport or canal system. Water enters through minute pores (ostia) in the body wall into a central cavity, spongocoel, from where it goes out through the osculum.
*Sponges are sessile organisms and remain attached to an underwater objects,called Substratum.
*Choanocytes or collar cells line the spongocoel and the canals.
*No distinct tissue or organ.
*Symmetry Radial or no symmetry.
*Body wall with outer pinacoderm(dermal epithelium),inner choanoderm(gastral epithelium) and gelatinous non-cellular mesechyme in between.
*Choanoderm is mainly made of choanocytes.The cells(choanocytes) are characteristics of porifers.
* The body is supported by a skeleton made up of spicules or protein spongin fibres.
*Sponges are the only metazoans having choanocytes.
*Digestion intracellular.No respiratory or excretory organs.Therefore ,respiration and excretion occurs by diffusion through general body surface.
*Excretory matter is mainly Ammonia.
*Primitive nervous system.
*All sponges hermaphrodite but cross-fertilization is the rule.Asexual reproduction by ova and sperm.Cleavage holoblastic.Development indirect through a free-swimming ciliated larva,the Amphiblastula or parenchymula.
* Fertilisation is internal and development is indirect having a larval stage which is morphologically distinct from the adult.
Examples~
Sycon-Scypha
Spongilla-Fresh water sponge
Euspongia-Bath sponge
Hyalonema-the Glassrope sponge.
Cliona-the boring sponge
Chalina-deadman's fingers
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