Parental Care In Fishes

Parental Care

Parental care must have been, doubtlessly one of the most significant steps in animal evolution.

Scientists have described it as any type of behavior, after fertilization, which promotes an improvement of the reproductive success of the offspring (Clutton-Brock, 1991).

However, no matter how normal it looks to us mammals, not all of the animals species take care of theirOffspring.

Only few invertebrates, mostly spiders and scorpions give some kind of protections to their descendents.

Among reptiles parental care is more the exception than the rule, leaving birds and mammals, as the only animals that, with few exceptions, raise their offspring until they can live by their own.

However parental care is not so widespread among fishes.

Only twenty percentof the fish species provide some kind of parental care. Most of the times, after being fertilized, eggs are left on their own, floating on the surface of the ocean, adhered to water plants or scattered among the bottom stones, looking for quantity instead of quality as a breeding strategy.Those species count on a huge number of unattended eggs or fry will still manage to produce a sustainablenumber of adults no matter they are left on their own in a world full of hazards and predators.

But, on the other hands, fishes are the animals that show the most different strategies to help the fry to survive their first stages.

Parental care means several changes to fish breeding, starting with clutch size.

A wild carp, for example can lay over 30 000 eggs, hidden among plants near thebottom, but it is unlikely that even the most devoted parents could handle such a school.

Not the fiercest pair of wolf fish (Parachromis dovii) could drive predators away from a cloud of tiny fry that would spread for several square meters.

In terms of biologic efficiency, for parental care species, it could be more productive to protect a limited number of fry that just releasing a huge numberof eggs defenseless among the bottom pebbles.

Of course that different strategies work differently for each specific environment. Temperature, potential hiding spots, water movements, abundance of predators among other factors can play a role in which path is more efficient in a given habitat.

Perhaps one of the most extended strategies are related to substrate spawner fishes, that laytheir eggs on rocks, logs and other though surfaces.

Those species tend to have some sort of territorial display to keep potential predators, or dangerous conspecifics, away from their eggs and larvae.

Among those species, we find many cases of biparental protection, as in the case of many cichlid species.Quite often the male takes care of the territory, patrolling around the borders, and thefemale stays closer to the fry, although parents exchange duties when one of them takes a break to search for food.

But despite the well deserved fame of cichlids for their devotion for family life, there are many other fishes that watch over their offspring.

Badis, for example are small fishes, barely reaching the two inches long, but despite their size, they are brave when it comes to guardtheir breeding .Once the female enters the burrow where the male is, the pair spawns after a brief courtship dance where they swim around each other and lock jaws.The male then guards and defend the eggs but will only look after the fry for a short time until they are able to swim.

Most of the times, only the male is in charge of the spawn, as in the case of the European stickleback, of thegenera Gasterosteum that builds a nest with plants and debris, where several females lay their eggs.

The male guards the nest after fertilization, doing maintenance, helping to keep the structure together with a sticky substance secreted from the kidney and fanning the eggs to drive rich oxygen water on them. The interesting point in this species, is that the glue-like secretion has been found...