THE FISH Osteichthyes-Bony fish (eg.Tilapia sp.) Most bony fish belong to the group of ray-finned fish called Teleostei. Most food, sport and aquarium fish belong to this group. About 30000 species and sub-species are known. Habitat Bony fish occur in seawater, fresh and estuaries. External characteristics The body is divided into head,trunk,and tail.On the head are a mouth, two large eyes, two external nostrils for smelling and an operculum(a bony plate …showed first 75 words of 673 total…

…showed last 75 words of 673 total…the female into the water and the male discharges its sperms over the eggs. Fertilisation is external. The eggs are supplied with yolk and which is used during the development of the growing fish until it can fend for itself. Fish are oviparous (egg laying). Ovoviviparous (eggs are retained and hatched in mother's body and then give birth to live offspring) types also occur but are not very common (e.g. guppies - Poecilia reticulata).