It is dried, beaten and washed and all cells are removed. The presence of contractile cells or myocytes around the ostia Fig. Thechoanocytes organized to form water canal system. The micromeres invaginate and move inward, while the macromeres grow over the micromeres by epiboly. I Spongin fibers: The spongin fibers are made up of.
These are Ostia or inhalant pores or dermal pores leading to the incurrent canals. All members of this phylum are aquatic. Triradiate spicules with equal rays. In many cases dermal pores open into subdermal spaces. Spermatogenesis: A sperm mother cell Spermatogonium , which is an enlarged archaeocyte or a modified choanocyte, gives rise to Spermatocytes that form Spermatozoa male sex cells or sperms. They have a collar like ring of microvilli surrounding a flagellum.
Therefore, deeper layers of the body are provided with supporting spicules. Pinacocytes covering the outer body surf from the dermal epithelium and which cover paragastric cavity and form the gastral epithelium. Classification The higher classification of the Porifera is considerably confused by different experts preferring different schemes. Due to excessive growth of mesenchyme sub-dermal spaces are formed in its body wall. It opens to the exterior though an excurrent opening called osculum which is similar to that of the ascon type of canal system. Food particles at the base of the collar are ingested as food vacuoles.
The ostia open in these spaces which lead into incurrent canals. Budding is the most common type of asexual reproduction. Pieces of their body, when kept in suitable environment, produce masses of cells that develop into young sponges. The spongocoel is the single largest spacious cavity in the body of the sponge. Sponges are generally hermaphroditic, however they are only one gender at a time, being either male or female or neuter, some species such as Halichondria moorei change colour when they change sexes though most do not.
The first step above the asconoid type of canal system is represented by the syconoid type of canal system. Skeleton is made up of calcareous. In sponges, as a result of development of elaborate canal system, massive growth is found. Besides this, it is found in Leucosolenia and some other simple sponges. . It is the distinguishing feature of all the sponges.
When they become active in skeleton formation it is called a scleroblast. In the life history Amphiblastula larva is seen. However some division of labour is present among the cells. It is solid, oval, or flattened, and its entire outer surface bears flagella. Throughout this body run canals through which water flows, there is considerable variation in the complexity of these canals. For Example Spongilla is a fresh water sponge.
These are thin, flat epithelial cells covering the exterior surface and some interior surfaces. Characteristics of Porifera:- 1 No definite symmetry. It is found in lakes and slow streams. The respiration is also intracellular. Chromocytes : These are with lobose pseudopods and contain pigments. Scleroblasts that secrete silicious spicules iii' Spongioblasts.
The water current reaches the spongocoel after passing through the ostia and goes out through the osculum. The sponging skeleton is treated with hydrochloric acid and the spicules dissolve. They are then set free into the surrounding waters. Potocytes :These are tubular cells distributed among the pinacocytes. Their food consists of bacteria, microscopic algae, protists and other suspended organic matter. The radial canals are lined by collar cells opening at the surface and are provided with flagella or whips.