Classification of invertebrate zoology (phylum porifera)

Phylum Porifera;

The name porifera is originated from Latin word Porus mean pori and Ferro mean to bear’ however the evidence of  their nature was given by Ellis in 1765 who has defined the water current entering and leaving the sponge.

Features/Characters of Porifera;

The most of the sponges are marine however some of them live in freshwater. They are usually attached and sessile invertebrates in adult stage. Their body is vast or cylinder  like  that is asymmentrical and radially symmmentrical. On the surface of their body many pores are present called ostia through which water enter in the body and also have several opening called oscula through which water is passes out. Porifera are multicellular dipoblastic animals which are having an outer dermal and an inner choanocyte layer, but the intermediate mesenchyme layer is absent. The sponges skeleton consist of flexible fibers known as spongin fibers, siliceous and calcareous spicules. In porifera excretion occur through the osculum while their nervous system is not well develop. The Reproduction occur in these animals by two means, the asexual reproduction take place by mean of buds and gemmules and sexual reproduction take place place by mean of ova and sperm. These animals having internally fertilization but cleavage is holoblastic. Furthermore these animals are having great power of regenernation.

Classification of phylum porifera;

The phylum porifera has been differentiated into the four classes;

Class 1. Calcarea;

The calcarea are marine in habit and live in shallow water. As the name indicate their chief features are presence of calcareous spicules. The calcarea are leuconid, syconoid and asconoid in structure. These are dull in colour and their size is less than six inches. This class is subdivided on the base of one type of canal system, their relationship with flagella, position of choanocyte and larval development. They are further divided into the three orders;

 Order 1; Clatherinida ( eg, Clatherina)
 Order 2; Leucosoleniida (eg, Leucosolenia)
 Order 3; Sycettida ( Scypha)

Class2;Hyalosponngea (Hexactinellea)

The glass sponges include in this class, they are deep sea in inhabitants and widely distributed. They have been characterized by the presence of siliceous spicules of triaxon type. Their body is tubular or basket shaped and spicules may form continues skeleton that is resembling spun glass. They are having large spongocoel which served as residence for pair of decayed crustaceans as well spongicola venusta. This class is further divided into the two orders;

 Order 1; Amiphidiscosida ( eg, Hyalonema and Pheronema.)
 Order 2; Dictyonida ( eg, Venus, Euplectella, Aspergillum and flower basket).

Class 3; Demospongia;

These porifera are currently dominated as well these are widespread in nature and numerous in species and in an individuals. Their canal system is completed that is connected with small spherical flagellated chambers. Their skeleton consist of siliceous spicules however these are not triaxon like the hylospongia. Their spicules are straight and needle shaped while other have eight rays ( tetra-axon). They are having parenchymula larval stage and amphiblustula larva while in some larval stages are not observed. This class has differentiated into one of the following orders;

Class 4; Sclerospongia;

Their skeleton is compose of sponging and spicules. Their skeleton also having basal mass of calcium carbonate.these are having cryptic habitats on the coral reefs.