Question

Endoskeleton of fishes are made up of cartilage and bone. Classify the following fishes as cartilagenous or bony:

Torpedo, Sting ray, Dog fish, Rohu, Angler Fish, Exocoetus

Answer 1

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Torpedo — Cartilagenous
Sting ray — Cartilagenous
Dog fish — Cartilagenous
Rohu — Bony
Angler Fish — Cartilagenous
Exocoetus — Bony

$\: \: \: \: \: \: \: \: \: \: \: \bullet \: \:$ ${ \underline\textbf{Cartilaginous Fish}}$

(i) Marine fishes, having cartilaginous endoskeleton.

(ii) Body spindle-shaped or dorso - ventrally flattened and disc-like in shape.

(ii) Mouth is ventral.

(iv) Skin is tough containing minute placoid scales and mucous glands.

(v) Fins median (dorsal, anal and caudal) as well as paired (pectoral and pelvic), used for locomotion.

(vi) Caudal (tail) fin is heterocercal, i.e., divided into two unequal lobes.

(vi) Respiration by 5 to 7 pairs of gills opening outside by means of gill slits which are not covered by operculum (gill cover). Vin Alimentarycanal and urogenital ducts open into a dloaca.

(ix) Heart is two-chambered and cold-blooded.

(x) Ureotelic animals, i.e., excretory waste is urea.

(xi) Sexes are separate.

$\: \: \: \: \: \: \: \: \: \: \: \bullet \: \:$ ${ \underline\textbf{Bony Fish}}$

(i) Freshwater and marine fishes, having mainly bony endoskeleton. Body spindle - shaped.

(ii) Skin with mucous glands and usually embedded ganoid, or cycloid or ctenoid scales. No placoid scales. Some without scales (naked).

(iii) Fins both median as well as paired.

(iv) Tail fin usually homocercal, i.e., single lobe or two equal sized lobes.

(v) Mouth is terminal (anterior).

(vi) Respiration by four pairs of gills, opening outside by separate gill slits. Gill slits are covered by operculum.

(vii) Heart is two-chambered and cold blooded.

(viii) Cloaca is absent. Anus and urinogenital apertures are distinct.

(ix) Excretion is ureotelic.

(x) Sexes are separate.

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Answer 2

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