Differences Between Cartilaginous and Bony Fishes

Fishes are mainly aquatic, jaw bearing vertebrates. They have gills for respiration and paired fins for swimming. Fishes are divided in to evolutionary lines –

1.Cartilaginous fishes or Chondrichthyes – it is also called Elasmobranchs. It includes – sharks, rays, skates, Chimaeras.

2.Bony fishes or Osteichthyes -  it is true bony fishes. It includes – Carp, Perch, Bass, Trout, Catfish and Sucker fish.

There are some differences between these –

Characters	Cartilaginous fishes	Bony fishes
1.Habitat	Mostly marine	Marine & pure water both
2.Size	Generally dorsoventrally flat	Generally bilaterally flat
3.Caudal fin	Hetero-cercal	Homocercal or Diphycercal
4.Pelvic fin	Generally posterior, and forms claspers in male.	Generally anterior, claspers absent.
5.Mouth	Present on the ventral side of head	Present on the anterior part of head
6.Gill pores	Generally 5 pairs and naked, operculum absent.	5pairs of gill pores, and operculum present.
7.Nostrils	Generally transformed by first gill pores, and present in the back of eyes.	Absent
8.Cloaca	Present between pelvic fins	Absent
9.External skeleton	Formed by dermal placoid scales	Formed by dermal cosmoid, ganoid, and cycloid scales.
10.Internal skeleton	Cartilaginous	Bony
11.Jaw suspension	Hyostylic	Hyostylic or autostylic
12.Types of gills	Long, with internal gill valve	With internal gill valve, fibrinous
13.Air bladder	Absent	Present
14.Stomach	J-shaped	Shape irregular
15.Intestine	Small, scroll valve present	Long, scroll valve absent
16.Anus gland	Present	Absent
17.Liver	2 lobed	3 lobed
18.Conus arteriosus	Present	Absent
19.Afferent gill vessels	5 pairs	4 pairs
20.Efferent gill vessels	9 pairs	4 pairs
21.Retina	Cone cells absent	Cone cells present
22.Control of eye	Lens moves forward by muscles	Lens moves backward by muscles
23.Brain	Primitive, exceptionally big olfactory and cerebrum and cerebellum small.	Cerebrum and cerebellum present.
24.Restriform lobe	Present	Absent
25.Ductus endolymphatic	Opens on anterior part of head.	Doesn’t open outside.
26.Male genetic duct	Linked to kidney	Doesn’t linked to kidney.
27.Oviducts	Not linked to ovary.	Linked to ovary.
28.Urinogenital pores	Compound, and opens in cloaca.	Different, and opens outside separately
29.Fertilization	Internal	External
30.Clasper	Present	Absent
31.Eggs	Less in no. and big	Infinite and small
32.Development	External in oviparous and in eggshell	Generally outside and eggshell absent.

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