General Principles

Most fish kept by aquarists are oviparous (egg-layers), but there are some exceptions - viviparous fish (or livebearers). A varied and rich diet enables fish to accumulate reserves of proteins and lipids, which help them form eggs and spermatozoa. This is the maturing phase. When the female's ovary swells, she is ready to lay eggs. This only needs a stimulus to trigger it off, such as, in the natural setting, rain, sunlight, or moonlight (research is presently in progress on the influence of

Pair of Hemichromis bimaculatus (jewel cichlid) surrounded by their young.

Pair of Hemichromis bimaculatus (jewel cichlid) surrounded by their young.



- Have well-fed and healthy parents.

- Provide them with the best possible environment:

• high-quality water, with characteristics as close as possible to their native setting.

- Anticipate how you are going to feed the fry.

the moon on reproduction). In an aquarium, egg-laying is sometimes sparked off by the early morning sunlight, which beats down on the tank with varying degrees of intensity, or by a partial change of water. The laying of eggs can be preceded by a courting ritual, during which the male seduces the female or, in rare cases, bullies her and violently sees off any rivals. The female then expels her eggs into the water, and these are immediately fertilized by the male.

This is obviously only a general description that leaves room for the huge diversity found in aquarium fish, particularly as regards the future fate of the eggs: they can be abandoned, or even sometimes eaten, by their parents, or they can be guarded and defended in the first days of their life, and a similar variety of parental behavior is found in the treatment of the developing fry.

The incubation of the eggs, which lasts several days, sees the development of the embryo. When this is completely formed, it moves about until it breaks the egg's membrane: this is the hatching. A larva emerges, differing from an adult in its form, size, and the proportion of certain organs. The larva has highly developed eyes, for instance, allowing it to spot its prey. It also has a vitellin vesicle, which provides it with food reserves during the first days following its emergence from the egg (except in live-bearers of the Poeciliid family). The larva gradually evolves, over the course of a few days or weeks, depending on the species, and modifies its behavior to become more and more like an adult. It turns into fry.

4 -juvenile

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