Friday 12 February 2016

OSTEICHTHYES CLASS, VERTEBRATA

* habitat-both marine and fresh water fishes
* endoskeleton is cartilaginous in the embryonic stage, but in the adult forms it is replaced by bones.
*they are ectothermic( cold blooded)
* there body is streamlined
*the mouth is terminal, digestive tract leads into an anus.
*a swim bladder is usually present,helps in floating
*they have four pair of gills which are covered by an operculum
*the exoskeleton, if present comprises cycloid, ctenoid and ganoid scales.
*the heart is 2- chambered and has sinus venous and anteriosus.
* lung fishes have three chambered heart.
*kidneys are mesonephric.
*there are 10 pairs of cranial nerves.
*fertilization is generally external.
*e.g.- Labeo(rohu), Catla (katla), Muraena(eel)

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