Aphrodite, commonly called the sea mouse ', is a marine polychaete. It is found crawling or burrowing in mud or sand of sea bottom. Its body is oval, broad, dorso - ventrally flattened, about 12 cm long, and consists of 30-35 segments. Dorsal surface is covered by 15 pairs of differential overlapping scales or elytra, which are supposed to be modified dorsal cirri of certain parapodia.
Elytra are partially covered by a felt of fine, long and hair - like setae that arise from notopodia. In addition, there are brown protective, stiff spine - like setae and lateral iridescent bristles, variously colored in different species. As the animal moves, the body color changes from gold to peacock blue. Head is small and remains hidden beneath the dorsal felt. It consists of a peristomium and a prostomium bearing a pair of eyes, a single median tentacle and a pair of long lateral palps. Proboscis is an eversible buccal tube and leads into a muscular pharynx, provided with two pairs of jaws. Eighteen pairs of lateral caeca open into the intestine along its entire length. Their openings are guarded by epithelial cells, which act as sieves allowing only small particles of food to enter into caeca. Digestion is completed within caeca. Respiration takes place through the dorsal body surface. Water current is produced by the movement of elytra and pumping action of dorsal body wall. The current passes through the channel between body wall and elytra and escapes near the posterior end of body. The common species is Aphrodite the Atlantic and the most aculeata, inhabiting Mediterranean.
No comments:
Post a Comment