Fish development: eggs

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Transparent are the eggs of bony fish and most round. There is a permeable outer membrane with small pores, called the chorion. This membrane is generally smooth, although in some species it has a hexagonal lattice.

El yolk from egg is in charge of providing the energy and nutrient reserves what the embryo needs during its development until it is able to feed itself, when it is already part of the plankton. In some species de peces, the yolk occupies all the available space and leaves only a marginal area free.

En elasmobranchs, once they have fertilized ovules, they are covered with a corneal capsule that has different measures and sizes depending on the species. In some oviparous sharks, for example, this capsule has a more or less rectangular appearance, and is provided with filaments to fixate on the bottom.

As for the size of the eggs it is highly variable, although they are approximately 1 mm in diameter, and can range between 0,25 and 7 mm in the different species. The optimal egg size It is the one that maximizes the number of eggs and the future survival of larvae and juveniles.

The benthic eggs they are, in general, larger than the planktonic ones, with more yolk and less numerous. The development of the embryo inside the egg is longer, and the larva comes out in a more advanced state, with already pigmented eyes.

In return fecundity in pelagic spawning fish is higher than that of those who lay eggs benthic. There is thus a clear relationship between egg size and larval survival. And the fact is that the largest larvae are capable of eating a wide spectrum of prey and sizes, and are, at the same time, less vulnerable to predators.


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