Choanocytes are vase shaped cells with a collar of fine fibrils connected by microvilli. But as the pressure in the incurrent and excurrent canals is the same, there must be a difference of pressure within the chamber itself and the lower pressure must be towards the periphery. Leuconoid sponges tend to live in large groups with each individual sponge having its own osculum, however the borders between individual sponges are often hard to define and the sponge may act more like a large communal organism. These minutes pores are regularly disposed intracellular apertures each of which is a canal like structure situated within a tubular porocyte. Both these canals blindly end into the body wall but are interconnected by minute pores. There are two types of skeleton in sponges: a Spit lest The spicules consist of microscopic needlelike spikes Spic les are formed by amoeboid cells. Now the ameboid cells come out through a tiny opening called the micropyle.
The spongocoel and canals are lined by collar cells choanocytes. They are aquatic and sessile , living permanently attached to submerged objects. The flagellated chambers open to the outside by dermal ostia or Prosopyles and they open into the spongocoel by opening called apopyles. The Best I can do is to offer two different schemes to give you some idea of the problems, either one is satisfactory for secondary schools and beyond that you should consult your teacher or lecturer unless you would become a Sponge taxonomist. The numerous perforations on the body surface of the sponges for ingression and egression of water current are the main constituents of the canal system.
The surrounding sea water enters the canal system through the ostia. Numerous minute pores the ostia are also present in the thin wall of the cylinder. It captures small crustaceans with the help of these spiculces. It also occurs in Olynthus stage of some newly settled calcareous sponges e. Eggs and sperm are also carried out of the sponge on this water current. These pores extend radially into mesenchyme and open directly into the spongocoel.
The outer layer is called ectoderm and the inner layer is known as endoderm. A single leucon with size 1 cm in diameter and 10cm high can fitter 20 liters of water everyday. The complication is due to the out-pushing of the wall into finger-like projections, called the radial canals, at regular intervals. Sponges have no permanent gonads, instead a number of areas of the sponge will during the reproductive period become differentiated changed to produce either sperm or ova eggs. Sperm release can be an individual act as in Verongia archeri or it can be a co-ordinated affair with many sponges in an area releasing their sperm simultaneously as in Neofibularia nolitangere. Phylum Porifera Class Calcarea Order Calcinia Order Calcaronia Class Hexactinellida Order Amphidiscophora Order Hexasterophora Class Demospongiae Order Homoscleromorpha Order Tetractinomorpha Order Ceractinomorpha Phylum Porifera Class Calcarea Order Clathrinida Order Leucosoleniida Order Sycettida Order Leucettida Class Hexactinellida Class Demospongiae Order Haplosclerida Order Poecilosclerida Class Sclerospongiae.
The selected food are digested by choanocytes of the flagellated chambers and serves the purpose of nutrition. One of the more amazing things about sponges is there ability to suffer damage. These spicules are important in the classification of sponges, thus we can say that. Restriction of choanocytes to the evaginated radial canals only. Water enters into incurrent canal through dermal pores. Numerous small pores ostia convey water into an internal canal system lined with flagellated collar cells choanocytes.
Ingressing water dermal ostia incurrent canal Prosopyles Radial canals Apopyles Spongocoel Osculum Outside Sycon canal system takes a more complex form in few species like Grantia, where the incurrent canals are irregular and branching forming large sub-dermal spaces. Mesohyl: Mesohyl is a jelly like layer present below the pinacocytes. These chambers are lined by choanocytes and are spherical in shape. They are primarily marine animals. They undergo and form flagellated sperm.
These canals are usually branched. The water current brings in oxygen and food, and removes waste. Here also incurrent canal brings water into the flagellate chamber. Most modern sponge species are Leuconoid. It opens to the exterior though an excurrent opening called osculum which is similar to that of the ascon type of canal system. The outer layer is called ectoderm and the inner layer is known as endoderm.
Swimming species tend to have a crawling phase immediately before settling down. Symmetry, though some are radially symmetrical. In many cases dermal pores open into subdermal spaces. Ecology All sponges are filter feeders on small to extremely small particles and most are sedentary or immobile as adults, i. Sponges are found at all latitudes, even in polar regions. There are about 10,000 known species and though their basic organisation is pretty simple and remains fairly constant throughout the all species they do manage to show a great variety of forms. Leuconoid type of canal system can be divided into 3 sub-types a Euryphylous type In this case the sponge has a flat broad base having an opening at the apex and looks like a pyramid.