Biodiversity

Tuesday, May 09, 2006

MORPHOLOGICAL DIFFERENCES BETWEEN CARTILAGINOUS AND BONY FISH


All fishes are classified as vertebrates organisms. Vertebrates organisms are organisms with the backbone. Fishes breathe in through their gills. Abedon (1997) also says that both cartilaginous and bony fishes belong to the kingdom animalia. Sharks, skates and rays are thought to be the examples of the cartilaginous fishes. They are termed cartilaginous because of the absence of the real bone, but their bodies consist of a cartilage. While on the other side bony fishes are thought to be real fish because they contain bones in their body.

Unlike other types of fishes, cartilaginous fishes have strong jaws. The mouth of the cartilaginous fish is found underside of the head, while the eyes are found on top of the head. Cartilaginous fishes also possess the ''two nostrils which are used for smelling'' (Abedon, 1997). As Shark is one example of the cartilaginous fish, they are unable to see the food while entering their mouth. The skin of the cartilaginous fishes such as the sharks, rays and skates is also compared with the sandpaper, because of its roughness. Five to seven pairs of the external gill openings are also found in the cartilaginous fishes. But ghost sharks have the skin which is smooth and one pair of the external gill openings. Fertilization in cartilaginous fishes is internally.

While on the other side bony fishes are termed true fishes. This is because we are familiar with this type of fish. An example of these fishes includes groper, gurnard and snapper. Unlike cartilaginous fishes, bony fishes have bones and one pair of the external gill openings. Its mouth is also found in the front of the head. Bony fishes also possess a tail fin which is equal in both bottom and top portions.

The brain of the ghost sharks is closely related to that of the birds and mammals (Wikipedia contributors). As compared to that of the bony fish, the brain of the cartilaginous is ten times to that of the bony fish. While the brain size of the bony fish is thought to closely relate to that of the human beings, the reason of having such a big brain is attributed to the much usage of energy.

In conclusion, one can say that both fishes, cartilaginous and bony indicate a huge morphological variety. This is because their structural body is totally different, as one considers that the mouth of the cartilaginous fish is under the head while that of the bony fish is in front of the head the head. Even the cover of their body is different; the cartilaginous fish is covered with a rough skin while on the other side the bony fish is covered with the rough skin but not like the one in the cartilaginous fish.

References:
Abedon, T. S. 1997. Ascent of mammals. [Online]. Available from:
Wikipedia contributors. Chondrichthyes [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 05, 13:15 UTC [cited May 08]. Available from: http://en.wikipedia.org/wiki/Cartilaginous

Wikipedia contributors. Bony Fish [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 06, 13: 23 UTC [cited May 08]. Available from:
http://en.wikipedia.org/wiki/Bone


Peter Muvhali
CSIR PTA
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Tell no 012 8142133
Fax 012 8423676
E-mail smuvhali@csir.co.za
URL: http://www.blogsoccer-peter.blogspot.com/

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