List three features that characteristise bony fishes.

Explanation

Living jawless fishesThey are ectoparasites on some fishes.(i) Skin is covered by ganoid, cycloid or ctenoid scales. (ii) Respiration is by four pairs of filamentousgills and is covered by an operculum on eitherside. Air bladder is present with or without a connection to the gut. (iii) They have a ventrally placed two chambered heart. (iv) Excretory organs are mesonephric kidneys and are ammonotelic. (v) Presence of well developed lateral line sense organ. Sexes are separate, externalfertilizationis seen and most forms are oviparous.