Biodiversity

Wednesday, May 10, 2006

MORPHOLOGICAL DIFFERENCES BETWEEN CARTILAGINOUS AND BONY FISH

Bone fishes also referred to as Osteichthyes-osseous tissue is a hard endoskeletal (internal support structure of an animal) connective tissue. Bones give the body posture structures support and also help in facilitating movement (1). Bony fishes are characterised by a “relatively stable pattern of cranial bones and rooted teeth” (4). The head and pectoral girdles are covered with large dermal bones and the eyeball is surrounded by a sclerotic ring of four small bones. They also have an “operculum, which helps them to breathe without having to swim" (4).

Cartilage is dense connective tissue and “it is composed of cells called chondrocytes. Chondrocytes are “dispersed in a gel-like ground substance called matrix" (2). Cartilage is a vascular (contains no blood vessels) and nutrients which are diffused through the matrix. Cartilage is mostly found “in the joints, the ear, nose, rib cage and in the throat” (2). Cartilages provide a framework for fish which do not have bones and in bony fishes the framework is provided by the bones (2). The cartilaginous fishes are also referred to as Chondrichthyes “which have jaws with paired fins, paired nostrils, scales, two-chambered hearts and a skeleton made of cartilage” (3). Cartilaginous fishes have a tough skin which is covered with dermal teeth also called placoid scales or dermal denticles which protect the fish since it does not have bones (3).

Cartilaginous fishes do not have any bone marrow since bone marrow it is manufacture in the bones so the red blood cells are produced in the spleen and special tissue around the gonads. In the bony fishes the red blood cells are produced in the bone marrow like in humans since they have bones. Cartilaginous fishes have also an “organ where red blood cells are produced called Organ of Leydig. Another unique organ is named epigonal organ, which plays an important role in regulating the immune system" (3).

The brain of cartilaginous fishes is relative to the brain of mammals in weight, and is about ten times the brain of bony fishes. The bony fishes have a relative brain size to be compared with the brain size of humans. One of the explanations why cartilaginous fishes have such large brains is because they are using much less energy and their bodies’ consists mostly of bones. The density of nerve cells in cartilaginous fishes “are much lower than in the brain of bony fishes, making it less energy demanding and allows it to be bigger"(3).

Bony fishes have various types of calcified tissues: dentine, enamel (or enameloids) and bones. Endochondral bone of the bony fishes begins as a cartilage then it later turns to a bone (4). Cartilaginous fish gets calcium from a cartilage called hyaline (3).

Bony fishes get most of their calcium from the bones but the cartilaginous fishes get their calcium from hyaline articular cartilage. Basically bony fishes consist mostly of a cartilage when the fish is still young the bone only develops when the fish starts to grow so even the bony fish use cartilage because cartilage is much more flexible than bones. Cartilaginous fishes are lighter in weight than the bony fishes which are much heavier for example Marlin (5) which weighs up to 820 kg. Bones have a lot of weight than the cartilage so bony fishes will be a little bit lazy since they weigh too much. Cartilaginous fishes are more flexible than bony fishes since their bodies consist mostly of bones and bones are very hard (not even flexible).


References:

1. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 7, 20:02 UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Bone
2. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 3, 21:28 UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Cartilaginous
3. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 5, 20:22 UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Cartilaginous_fish
4. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 7, 12:50 UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Bony_fish
5. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 15, 09:47 UTC [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Marlin

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
Mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

3 Comments:

  • Your assignments still have hyperlinks. To remove just right click on the word and choose "remove hyperlink". Cheers Gud Luck!
    Vincent

    By Anonymous Anonymous, at May 10, 2006 1:23 PM  

  • Hi Vincent
    thanks i have removed them

    By Blogger lethabo, at May 16, 2006 10:01 AM  

  • You still do not understand when to use quotes. The referencing in this essay is better but there is still plagiarism.

    By Blogger Gwen, at May 22, 2006 12:38 PM  

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