parental care of fishes

Introduction • The nursing of eggs and youngones by parents is called parental care.• It is an instinctive behavior. fishes which produce large number of offspring's shows less parental care.• Fishes which produce limited number of youngones show high degree of parental care.

Types:•Nest Builders• Fishes that attached the eggs on their body•Mouth breeding•Mermaids purse• Viviparity

Nest builders •Bubble nest•Weed nest•Pit nests

Bubble nest•Some fishes makes bubbles of air on the surface of the water and lays the eggs inside the bubbles.•E.g.: Chinese paradise fish, Macropodus (males guarded the nest)

Weed nests• Etroplus suratensis(Pearl spot) built a nest in over hanging weeds, submerged in water. When youngones develop, they put them in small pit and the female guard them. •Amia during breeding season, these fishes move to the area where there is abundance of weeds. It swims round and round among the weed until the eggs hatch.•Gasterosteus ( stikle-back) during breeding season, males develop beautiful coloration in the body. Then the male starts building the nest with aquatic weeds. Then the male attracts the female into the nest. The female lays the eggs which are fertilized by the male the male then drives away the females and brings in another female to the nest to get a treasure of eggs. The male guards the eggs until they hatch.

Pit nests•Slmon digs a small hole in the gravel bottom of the hill streams and lays the eggs• Lepidosiren makes pits under the ground level. The eggs are deposited in “L” shaped nests built underground.•Cyclopterus builds a nest in pits in the rocks and lays eggs. The eggs are usually attached to the rocks. The males guard the eggs and aerate them by creating a flow of water by moving its pectoral fins.

Breeding habit of Rhodeus• It is a small cyprinid found in the rivers of central Europe. It lays the eggs inside the tubular siphon of freshwater mussel. For this purpose the oviduct of the female develops into a tubular ovipositor.•The ovipositor passes the eggs into the siphon and immediately the male sheds the sperm and the fertilization takes place.

Fishes that attached the eggs on their body•Mystus aor( Giant River cat fish): this fish builds nests of circular depression in the bottom and eggs are laid by the females in the nest.• The males attach the eggs to the abdomen by pressing against them and carry them all they get hatched.• The nurse male even feeds the young ones with a milky secretion of the abdominal wall.

•Pholis(butter fish): this fish is in the habit of rolling the eggs into a mass. afterwards, one of the parents guard the eggs by coiling round the eggs. •The egg masses are laced safely on holes made by boring molluscs. •Kurtus: the male is provided with a bony hook projecting from the forehead. The mass of eggs is produced in two bunches connected by a string. This gets attached to the hook in such a manner that one bunch of eggs lies on either side of the male as he swims.

•Hippocampus(sea horse): in sea horses, the male has a brood pouch in the trunk, at the breeding season this pouch becomes thickened and well supplied with blood vessels. The female lays the eggs in the brood pouch of the male. The eggs are incubated there until hatching. The brood pouch is the modified pelvic fin.

• Pipe fishes: in the pipe fishes, the care of the egg is always undertaken by the male fish. • After the eggs are fertilized the oviduct of the female is

thrust into the small opening at the front end of the males brood pouch. The eggs remain in the pouch until hatched. • The egg are carried in a special brood pouch situated on

the underside of the trunk.

Mouth breeders •Many of the cichlids protect their eggs by carrying them in their mouths. Normally this duty is performed by the mother.•Arius: it is a brackish water cat fish of north and South America. It lays only a few eggs which are about 17-18mm in diameter. The eggs are carries in the mouth by the male until they are hatched. The male does not feed while carrying the eggs.• Tilapia: after fertilization the females keep the eggs inside the buccal cavity. Even after hatching the yougones remain near the mother and if there is any disturbance they enter the buccal cavity for shelter.

Mermaids purse•Some of the sharks and rays produce a special type of leathery case called mermaids purse. • It is a protective hard shell secreted by the shell glands present in the oviduct. The shape of the purse varies in different species. Generally, it is rectangular in shape. The corners of the shell are drawn out into four long twisted elastic filaments which serve to attach the purses to sea weeds. The development is completed within this purse.

Viviparity •The highest degree of parental care is found in viviparous fishes where youngones develop within the oviduct of the female.•The youngones gets its nourishment from the yolk sac placenta. Eg. Gambusia, Sword tail, Scoliodon, etc.,