Anatomy of finfish and shellfish

UNIT 1 - Anatomy of Fin Fish

1.2. External Anatomy of Fishes
1.2.1. Body forms
Commonly the fish body is Torpedo – shaped (fuci form) and often slightly to strongly avoid in cross section. In a perfectly “stream lined” body form (if head pointed trunk broadened and gradually tapering towards the tail) the greatest cross section is about 36% of the length back from the anterior tip and gently sweep back to the tailed.
However, all fishes do not have this typical body form. The shape of the body is variously modified depending on their habitat and made of living. There changes in shape are Globe shapes (Globiform – pufters of family Tetraodontidae) Serpentine (Snake like Angulli form – eels of family Anguillidae) Thread like in form (filiform – snipe eel Nemichthyidae). Some are strongly flattend from side to life (compressed butterfly fishes, chactodentidae and flounders – pleuronectidae) others flattened but greatly elongated trachipteriform – ribbon fishes, Trachipteridae) and till others flattoned form top to bottom/ depressed the skates and rays (Rajidae).

In spite of the many variations the ground plan of body organization in fishes is bilaterally symmetry. The left and right halves of the body are basically mirror images of one another. The tail is an integral part of the body rather than an appendage only the fins are distinctly peripheral anatomical parts in most fishes.

1.2.2. Body Covering
Fish is generally covered by a tough skin. It is continuous with the lining of all the body of the entire body opening and is transparent as it runs over the surface of the eye. Much of the diverse coloration of fishes is due to its colour cells and the slimy coating is due to its mucus cells.
The skin in many fishes is devoid of scales, but in them it is armored by scales that develop in it. Scales range in size from microscopic to large. In thickness from tissue thin to very thick (in ornamentation from simple to complex in extent of body coverage from portal to complete). In structure from non-bony to bony loosely attached to very firmly attached. The types of scales may characterize the major fish groups. Scale morphology and the number of scales rows along or around the body frequently serve as specific and genetic characters. Living Agnathaus are scale less, shark and their relatives have dentinal placoid scales, Bony fishes have various types of bony scales.