Danio rerio is one of the most popular aquarium fish, notable for its original color, mobility and agility. This graceful and elegant creature has a peaceful and accommodating character, does not show aggression towards other inhabitants of the aquarium. When planning to engage in breeding zebrafish, you should first of all learn to distinguish females from males.
general information
Danio-rerio is a variety of ray-finned fish, which is characterized by small sizes. The average body length of adults varies from 2.5 to 4 centimeters. Typical color - iridescent light silver with blue-turquoise longitudinal stripes. The main difficulty in determining the sex of these fish is the strong similarity between females and males.
Another variety of fish that are popular with aquarists is pink zebrafish. The colors of these attractive creatures can change under the influence of various factors. In some cases, the fish look saturated pink, in others - silver-pink with a metallic tint. In young individuals, a bright red strip with bluish edges runs along the trunk, which becomes paler with age and soon disappears. As in the case of conventional zebrafish, it is rather difficult to determine the sex of pink fish due to their almost complete identity.
However, there are a number of specific parameters and differences that can tell the inexperienced aquarist the sex of a particular fish. It should be noted that sex can only be determined in adults, since in young zebrafish, gender characteristics are almost invisible.
Only a professional aquarist can determine the sex of young animals. An individual can be considered an adult 3 months after birth.
Body size and shape
The sex of the zebrafish can be suggested by the size of the individual. Adult females are always slightly larger than males. Their abdomen is more rounded and large, and the line of the abdomen is slightly curved down. This feature is associated with the basic natural function of females, which consists in procreation. In order for the female to be able to bear offspring, her abdomen must be elastic and extensible.
However, it should be borne in mind that in zebrafish males, in certain cases, the abdomen may be slightly enlarged. This phenomenon is observed with diseases of the digestive system and malnutrition. In sick fish, the abdomen is more swollen in the front of the body.
Healthy zebrafish boys have a leaner, sleeker physique. Their body is more elongated in length. The line of the abdomen is more even and taut than that of females.
Coloring
Visually, the zebrafish boys and girls are very similar. However, a detailed examination of each individual reveals insignificant differences in their color. Males have a brighter color with pronounced brilliance. The stripes on their body have a deep turquoise color. Males of pink zebrafish are also noticeably more colorful than females. This feature is due to the fact that the bright color helps males to attract individuals of the opposite sex.
Female zebrafish, in turn, have a paler color. Their stripes on the body are less pronounced and less colored. This feature is explained quite easily: during gestation and subsequent spawning, fish need to disguise themselves from predators.
Given that pregnant individuals are less mobile, they need the ability to hide from sources of danger. In this not the last role, a soft coloring plays, which does not attract the attention of predatory fish.
Behavior
You can distinguish a zebrafish boy from a girl by their behavior. Having carefully watched your pets, it is easy to notice that some of them are more active, more energetic and agile, while others prefer a somewhat measured pace of life.
If the fish behaves very playfully, then with a high degree of probability we can say that it is a male. Danio rerio boys are always more active than girls. They exhibit the greatest mobility during the breeding season. Energy and high speed provide them with leadership in front of competitors fighting for the female’s attention.
Anal fin shape
This method is suitable for experienced aquarists professionally engaged in breeding zebrafish. However, it can be used by very attentive beginners.
The shape of the anal fin in females is more rounded. In size, this part of their body is also slightly larger than that of males.
This fin in male zebrafish is slightly pointed. In addition, in males this part of the body is slightly shorter than in females.
The experimental method for determining sex
It will help to distinguish in practice boys and girls of zebrafish from a rather simple experiment based on creating favorable conditions for reproduction. In the natural habitat, these fish begin to breed during heavy torrential rains. At this time, the temperature in the reservoirs rises and the water level rises, which creates the most suitable conditions for spawning.
At home, you can artificially recreate such conditions, stimulating adults to reproduce. To do this, the water in the aquarium with fish should be increased to 24 ° and maintain it at this level during the mating season. At this time, fish should be given live food: bloodworms, cyclops, tubule, daphnia.
Warm water will prompt the fish to mate, during which it will be easy to find out the sex of a particular individual. So, in just a few days, the males will begin to show noticeable activity, straying in flocks and chasing the females.
During mating games, zebrafish will be easy to distinguish by the increased abdomen in the anal fin. At the same time, the color of the males will change: it will become even more saturated and bright. Such changes indicate that fish of both sexes are ready for breeding and subsequent spawning.
If zebrafish are kept in a common aquarium with its other inhabitants, then for the above experiment they should be deposited in a separate tank. The volume of the container should be 10–20 liters. Fill spawning grounds should only be protected water.
At the bottom of the tank it is necessary to lay a fine mesh so that the fish could not eat their future offspring.
For breeding, only 1 female and 2 males are enough. Usually the courtship process does not exceed several days. At this time, you should carefully monitor the behavior of the fish. As soon as eggs appear at the bottom of the tank, the males and the female should be transplanted back to the general aquarium. Caviar is left in the bank for ripening. Later, fry will appear from the eggs into the light, which they will grow until they acquire the desired size. During this time, young animals are fed with ciliates, rotifers or artemia. When the kids grow up, they are transplanted into a common aquarium.
About sexual differences in zebrafish and preparation for breeding, see below.
