Biology of Finfish and Shellfish

4.6.6. External Carriers

These fishes carry the fertilized eggs till they hatch. There are different types of external carriers depending upon the type or mode of carrying.

a) Transfer brooders: The eggs are carried by various means and they are deposited elsewhere in a suitable area. e.g.: cyprinodontids

In transfer brooders the eggs are attached to the belly of female fish and these female carry their eggs until they found suitable area and plants and these eggs are deposited on the plants and guard them till they hatch out.

b) Forehead brooders: The unborn offspring (embryos) are placed in a depression on the forehead of the males, where they keep the young ones in place by threads attached to an overhanging hook like structure. After spawning, the female transfer the eggs on to the depression or hook like structure on the forehead of males. e.g.: Kurtidae

c) Mouth brooders : These fishes carry their eggs in the mouth till the young ones hatch out. After hatching the young ones move around their parents, if they find any danger, the young ones jumps into the mouth of the mother. e.g.: male marine catfish (Ariidae), cichlids – (Usually female carry the embryos, which she picks up quickly after spawning) and cardinal fishes.

d) Skin brooders: These fertilized eggs are attached on to the skin. The female fishes have a layer of spongy skin on their belly region, once the fertilization is over; the eggs get attached to the spongy skin of the female. This spongy skin also serves as placenta. e.g.: south american cat fish.

e) Pouch brooders : These fishes deposit the eggs in a cutaneous pouch. This is well developed in the case of male sea horse (Hippocampus). The females deposit the fertilized eggs into the pouches of the males. Even after hatching the juveniles are seen in the pouch of the male.