Study
of gills of fishes:
The presence of the gills is one of the most important characteristics of the fishes. In fishes, gills are respiratory organs.
Through gills intake of dissolved oxygen from water and removal of carbon
dioxide through body along with out going water is taking place. The structure of gill is different in
cartilaginous fish and bony fish.
Filiform
gill: Gills of bony fish : (Ex. Labeo)
1. In
bony fishes there are four pairs of complete gills. They are called as
holobranch.
2. Gills
are located on either side of the pharynx in branchial chamber.
3. In
bony fishes gill is filamentous (Filiform).
4. The
inter-branchial septum is greatly reduced due to that gill filaments hangs
freely in the branchial chamber or gill chamber. Hence such types of gills are
called as filliform gills or pectinate type of gills.
5. The
branchial chamber opens outside by wide opening lies between pectoral fin and
operculum.
6. Each
gill is highly vascular, richly supplied with blood vessel and shows several
transverse primary and secondary gill lamellae.
7. Exchange
of gases is take place through gill.
Lamelliform gill: Gills
of cartilaginous fishes: (Ex. Scoliodon)
1. In
cartilaginous fishes there are five pairs of gills.
2. Gills
are situated in gill pouches on either side of the pharynx.
3. Gills
are separated from each other by well-developed inter-branchial septum.
4. Inter-branchial
septum is supported by cartilaginous gill ray.
5. In
cartilaginous fishes gills are lamelliform.
6. First
pair of gills consist of single gill lamella attached to the posterior side of
hyoid arch and called as half gill or hemibranch or demibranch.
7. Remaining
gills consist of two-gill lamellae and called as complete gill or holobranch.
8. The
gill pouches open outside by narrow transverse gill slits.
9. The
mucus membrane of gill pouch is raised upward into leaf-like folds called as
gill lamellae.
10.
In gill lamella diffusion of O2 and Co2
is occurs.
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