Essay About Adult Coelacanth And Rostral Organ

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The coelacanth is an amazing creature full of mystery and exciting discoveries. It was once thought
to be extinct for more than360 milllion years ago until one was caught in1938.Its scientific name is Latimeria
chalumnae .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 rostral 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 dorsals, 2 pectorals, 2 pelvics, 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 tailhas 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 swimbladder
Unlike most fishes which have a gas-filled swimbladder, the coelacanth has a large swimbladder 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 lanternfish (Diaphus), cardinal fish (Coranthus) eels (Iiyophis), beardfish (Polymixia), 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.