The developmental stages that fish undergo to reach adulthood are divided into embryonic and postembryonic periods. You can designate them as stages of eggs and fry. These two processes are interconnected, and the structure of the fish larva naturally depends on the structure of the embryo. Thus, it would be logical to start from the moment the egg is fertilized by the sperm, which is where the development of living organisms begins.
Egg is a fry in the future
The stage preceding the development of the larva is the stage of eggs. In fish, most often external fertilization, that is, the female lays (spawns), and the male fertilizes it with milk. However, in some species, for example, carps: platies, guppies, fertilization is internal and the female, upon reaching the development of eggs, sweeps the already formed fry. The first time of development of the larva depends very much on what the egg is. If at the initial stages the fish will exist in a nutrient-poor environment, the eggs will usually increase in size. This gives the fry an advantage in the form of a supply of nutrients in the yolk sac (located on its abdominal part).
It happens that fish spawn in quiet backwaters, away from strong currents and predators, in order tosave future offspring. But in stagnant and warm water bodies, oxygen dissolves worse. In order to avoid oxygen starvation, a pigment (usually of the carotenoid type) develops in the caviar, it allows the larva to conserve and accumulate oxygen. If the caviar does not have breathing problems, it is more often transparent - this way it is less noticeable in the water column. As a protection for offspring, the egg has many solutions. Caviar can be sticky, clinging to plants and natural hiding places. It can be small and imperceptible, or vice versa, large, flooded, easily floating in water streams.
Fry fry are fish larvae. Their structure
From a fertilized fish caviar with the normal development of a living organism, fry comes out. So, what is this fry in anatomical terms, what are its structural features? He is a fish larva. A yolk sac can be seen on its ventral side. The fins are not yet divided into paired and unpaired. The development of the digestive system did not occur in full. Of course, the gonads are not developed. In the juvenile period, a characteristic body covering develops: scales. Subsequently, there is a gradual development of all organs and systems in the image of an adult.
Development Features
This period is characterized by the greatest linear and weight growth of the body. The rate of development even within one species can vary significantly and depends on temperature, light, and nutrition. For example, if light and temperaturethere will be more and enough food, then the achievement of sexual maturity and the development of fish will go much faster due to the acceleration of metabolic processes.
At first, the fry feeds on the material of the yolk sac. Further, it becomes able to eat crustaceans from plankton: daphnia, cyclops, etc. Some time should pass before moving on to the diet characteristic of adult fish.
During development, the larva may change. Malek is a transitional form to an adult. For example, in flounder, it first has bilateral symmetry, and then the body is divided into two sides: upper and lower. The eye moves to the upper side. In the snake-shaped European eel, the larva initially has a shortened body. And then it becomes like an adult organism.
Caring for offspring in fish
The survival strategies of each species are different. There is only one common goal: to leave as many offspring as possible, but you can go to it in different ways. There is a strategy - to lay as many eggs as possible: for example, an Atlantic herring can spawn 100,000 eggs. With a higher probability, at least a few individuals will survive from this number of eggs.
You can set aside a small number of eggs, but court them all. For example, the tilapia carries first the eggs and then the young in its mouth. It has already been said above about viviparous fish, which toss a small number of already formed larvae. Seahorses hide their offspring on their bodies. These are the fry that will survive with moreprobability, it means that the amount of spawned caviar can be reduced.
