calcareous sponge habitat

The processes in gametogenesis, i.e., production of sperm and ovum, are same as in other metazoans. They are characterized by spicules made out of calcium carbonate in the form of calcite or aragonite. 4. Before sharing your knowledge on this site, please read the following pages: At the dissociated stage, amoeboid cells (archaeocyte and amoebocyte) and flagellate cells (choanocytes) show movement (Fig. The fossil record of unambiguously identified Calcarea is relatively poor and fragmented. 4. When the mesenchyme con­tains few cells—this is called collenchyma. The opening is framed by fine hairs. H. V. Wilson (1907) for the first time demonstrated that a bit of sponge when squeezed through a silken mesh dissociates completely. But the collar cells are also found in certain other groups of invertebrates (e.g., in some corals, in the larval stages of some echinoderms). Amebocyte cells carry the nutrients to the sponge's other cells. On the contrary, there are certain features in sponges which may be considered as unique to them. 3.

While the spicules in most species have three points, in some species they have either two or four points. The flagella sway, drawing water through the cell, and the sticky collar collects particles of nutrients and oxygen. At least, most of them are. Some of the flag­ellated cells loss their flagella pass into the central cavity and become amoeboid. Sexual repro­duction by sperms and ova. 3. (3) Mode of secretion of skeleton within single cell; The sponges exhibit close protozoan affinities but the attempts to in­clude sponges under the Phylum Protozoa failed because of the development of germ layers in developing sponges. The amoebocytes are of several varieties in dif­ferent sponges. 7. The peculiar event in fertilisation that two synergids direct the sperm towards the egg is found to occur in chaetognatha. They lack mouth and digestive cavity. (Brusca and Brusca, 2003) Ecosystem Impact; creates habitat; Economic Importance for Humans: Positive. In a true metazoa, each function should be carried by a group of cells. 2. The tetra-radial symmetry exhibited by the larvae of calcareous sponges is com­parable with that of the larvae of polychaetes, sipunculids and gastropods. The central part of the cell is thickened due to the placement of nucleus. 14. Multicellular organisms having cellu­lar grade of organization without true tissues. Sponges can regenerate their lost parts very rapidly. The spongocoel corresponds to the coelenteron of the coelenterates but pores and network of choanocyte-lined canals are not seen in any metazoan group. Masters won two Pennsylvania Newspaper Association Awards in 2009. The body is composed of loose aggregation of various types of cells (Fig. During unfavourable condition most sponges shrink and form restitution bodies, which grow in favourable condition. 5. Sponges in general may make up a significant portion of the benthic biomass. Existence of wide regenerative power in sponges and in many lower metazoans. 2. R. E. Grant (1825) studied the morphology and physiology of sponges in greater details and named the group Porifera. All are filter feeders. There must be distinct differentiation of somatic and germinal parts of the body. The archeocytes are actually the generalised amoebocytes which play the domi­nant role in regeneration, reproduc­tion and differentiation of other cell- types.

A true metazoa will develop from a unicellular zygote and will pass through stages like blastula and gastrula. The cleavage is holoblastic and may be equal or unequal. Carnivorous sponges can catch live food rather than just eat whatever happens by.Most sponges are detritivores -- they eat organic debris particles and microscopic life forms that they filter out of ocean water. Sponges may be of varied colours and their shape depends upon the sites of their stay. Sponges have been harvested for centuries by many civilizations. Porifera are asymmetrical or superficially radially symmetrical metazoa with cellular grade of organization without tissues, organs, and with a porous body and a canal system lined by choanocytes. The comparative study of re­generation has revealed that the power of regeneration decreases with the progress from lower to higher groups of animals. The outer single layer wall of the central cavity contains elongated monoflagellated cells except the posterior side where a few rounded granular non-flagellated cells, called archaeocytes, are present. 11.14B). The sponge's eating mechanism depends on collar cells. So the claim of the ancestry of sponges from a protistan choanoflagellate is almost refuted by the appearance of collar cells in other groups of metazoans. Such property of sponge has later been seen by several workers in differ­ent marine and freshwater sponges. 4. Spongillidae). Gradually small aggregates meet other cells or other similar aggregates and grow in size. Each cell has a sticky funnel-shaped collar and a flagellum, a thin whiplike structure. Because every surface of the sponge's body is able to carry out this process, the sponge is a highly effective filter feeder.Although not scientifically classified so, sponges exist into two basic groups based on body structure: encrusting and free-standing. 11.15). Fossil sponges were discovered from beds of Europe, Asia and North America, which are more than 600 million years old. Solas proposed to place the sponges under a subkingdom, the Parazoa, as an isolated branch of the Metazoa. 11.17). 9. Two types of flagellated larval forms are seen in sponges-amphiblastula larva and Parenchymula (also called Parenchymella) larva. Asexual reproduction takes place by the fragmentation or through the produc­tion of gemmules or buds. Choanocyte cells are seen in some echinoderms and therefore, are not the only characteristics of sponges. This is followed by the appearance of flagellate cells, forma­tion of spicules and establishment of canals within the aggregate. They can develop in a variety of shapes, like tall tubes and cupped vases. It can reach a length of 9 cm after a life span usually no more than one year.

This phenomenon is called de-differentiation (Fig.