Fins Coelacanths example essay topic

The coelacanth is an amazing creature full of mystery and exciting discoveries. It was once thought to be extinct for more than 360 million years ago until one was caught in 1938. Its scientific name is Latimeria ch alumnae. An adult coelacanth can grow at least to 180 cm in length and weigh 98 kg and each fish has a distinctive pattern of pinkish white blotches that enables scientists to separate one individual from another. The coelacanth has several very recognizable anatomical features. The skull is in two parts with an intra cranial joint which lets it go an up and down movement between them.

A strong pair of muscles beneath the skull-base lowers the front half of the skull, giving the coelacanth a powerful bite. The eyes and olfactory organs are in the front part of the skull, and tiny brain and inner ear are in the rear. In the middle of the snout is a large pit filled with a jelly-like sac that opens to the outside through three pores. This sac is called the organ. It may be used to detect weak electric currents and help the coelacanth to find hidden prey.

The fins Coelacanths belong to a group of bony lobe-finned fishes and have 8 fins (2 dorsal's, 2 pectorals, 2 pelvis, 1 anal and 1 caudal). The first dorsal fin of the coelacanth is much like that of other fishes and can be folded down or erected. The other fins have a well-developed, muscular, limb-like basal lobe projecting from the body wall, and a fringe of unbranched rays like a fan attached to the outer end of the base. The fleshy scale -covered lobe can be bent or rotated so that each fin can work like a paddle or sculling oar. The tail has three divisions: a characteristic small projecting middle lobe between the longer upper and lower lobes of the fin.

The skeleton Most of the skeleton is made of cartilage. In place of the vertebral column, a large notochord extends from the skull to the tip of the caudal fin. The notochord is a thick-walled cartilaginous tube filled with oil-like fluid which is under slight pressure; it is tough and elastic and does the job of a backbone, since no complete vertebrae are developed around it. The scales The body is covered with hard scales with small toothy-like growths called denticles on the outer surface which protect the coelacanth from the rocks and predators.

The swimbladderUnlike most fishes which have a gas-filled swim bladder, the coelacanth has a large swim bladder that is filled with fat. Being lighter than the seawater, the fat provides buoyancy. Where the coelacanth lives The coelacanth is to be recorded from the shore of the African mainland. Until recently all other specimens have been taken at Grand Comoro and Anjouan Island in the Comoro Islands.

The East London fish was probably helped on its 2000 km journey by the strong southwesterly currents of the Mozambique Channel. The coelacanth is also likely to be stray from the Comoran population. Feeding habitats Evidence from the prey found in the stomachs of coelacanths indicates that they are predominantly fish-eaters taking lantern fish (Diaphus), cardinal fish (Coranthus) eels (Iiyophis), beard fish (Polym ixia), red breams, skates, sharks and also squid and octopus. The vertical head-down position has been found in other drift-feeding fishes.

When the coelacanth is close enough to the prey, the mouth is quickly opened, the prey grasped very quickly by powerful jaws and then swallowed whole. Some scientist have observed some large sharks in the habitat of the coelacanths and it is likely that large sharks may prey on the coelacanths. Sex and growth rate There is no visible outer difference between male and female coelacanths. Females re more muscular than males and grow to a bigger size. it is likely that the coelacanth could live as long as forty years.

Habitat and population sizeLatimeria ch alumnae is usually seen at depths of 150-700 m, with most sightings and catches between 150 and 253 m. During the day coelacanths retreat to caves where they can rest sheltered from currents and predators (sharks). There is proof that coelacanths may return several times to the same caves and that they have a home range. When in caves they hover in mid water, rarely touching each other. They appear to be social animals, but aggressive behaviour has not been noticed yet Where caves are rare, coelacanths are hardly ever found their population estimated to be about 200. Reproduction The reproduction of Latimeria is of a type called ovoviviparous, which means that it has internal fertilization, and the fetuses are kept are kept inside the mother until they are large enough to look after themselves.

Only one ovary matures (usually the right) and 19-26 large eggs about 9 cm in diameter and 320 g in weight grow inside it. The big yolk of each egg supplies the nutrients necessary for the fetus to grow. The 26 pups found inside the female coelacanth show that the fish may breed faster and produce more young than was previously thought. The Comoros and conservation of the coelacanth It was JLB Smith who warned 25 years ago that the open catching of coelacanths would threaten their survival, and he suggested that an international society should be formed to protect them. After he died the Coelacanth Conservation Council was supported by Prof Mike Bruton and three other ichthyologists, The fish is now on Appendix 1 of the Convention on International Trade in Endangered Species (CITES) which forbids trade on this rare species, and any caught should be released if they are still alive. Now that larger fibre glass outrigger canoes have been presented into the Comoros by the European Economic Community, and fish combining devices are used far from shore, it is hoped that fishermen will concentrate on offshore open water fishing, therefore scale down the pressure on near shore fish populations and likely prey species for the coelacanth.

Let us hope that will won't lose this great creature that may be our only hope for knowing about the past.