3 write a note on spicules in sponges
On the basis of development, the spicules may be primary which owe their first origin from a single mother cell or scleroblast, or secondary which arise from more than one scleroblast. Ejection of spermatozoa may be a timed and coordinated event, as seen in certain species. The image to the lower left is interesting. Tetraxons have four axes, and polyaxons more description of types to be incorporated from [1]. Note: Sponge spicules and mucus may be harmful to humans, causing abrasions or severe dermatitis. These tetraxons will loose one of their rays and look like triradiate. Obtain a piece of sponge about 5 to 10 millimetres on a side and place it in the container. Medically reviewed and approved by a board-certified member. Development of Monaxon spicule :. After this step the nitric acid solution should be carefully drawn off and discarded and replaced with water. List characteristics of the phylum Cnidaria that distinguish it from the other animal phyla. The majority of sponges are marine, living in seas and oceans. Later on, three rays or spicules unite together forming a triaxon or triradiate spicule. The club shaped monaxons are grouped in the derma cortex. They are often called reef sponges.
These are present in the gastra! It is a scleroprotein containing sulphur and chemically related to collagen. It demonstrates that tissue transplantation has problems even in sponges! Sponges reproduce by sexual, as well as, asexual methods.
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The four rays of the tetraxon spicule may be more or less equal, in which case the spicule is called a calthrops. Polyaxon: These are the spicules with several equal rays radiating from a central point. Sometimes all the rays are equal, when all the rays are equal it is termed as calthrops.
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Copy Link Share Share Share. Research on the Euplectella aspergillum Venus' Flower Basket demonstrated that the spicules of certain deep-sea sponges have similar traits to Optical fibre. This is obtainable at grocery stores. Most sponges reproduce sexually; however, some can reproduce through budding and the regeneration of fragments.
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Second cell is called thickner'. Among the small centred forms are oxyasters with pointed rays, strongylaster with rounded ends and tylasters with knobbed rays. Siliceous sponges almost always have both, and often several types of both. The spicules of sponges, however, are fascinating.
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Large-centred forms include spherasters with definite rays and sterrasters with rays reduced to small projections from the spherical surface. These monaxon spicules are further divided into two kinds, Monactinal- the growth of the spicule takes place only in one direction Diactinal- The growth of the spicule takes place in both the directions. Accordingly, they can be divided into the following forms: Monaxon: These kinds of spicules are formed by the growth along one axis. Accordingly spicules can be of two types: Megascleres: These are larger spicules constituting main skeleton of sponge body. Each ray is then completed in the same manner as a monaxon spicule.
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Meaning of Spicules 2. First, spicules are of two general kinds—megascleres and microscleres.
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3 write a note on spicules in sponges:
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