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Schooling zebrafish in your aquarium, how to care for and reproduce? Danio pink (Danio roseus) Species and their photos

The fish is also known by the names "Zebra Fish", "Striped Danio" and others. Over the years, breeders have developed new subspecies that differ in color, which can nevertheless interbreed, which leads to further speciation and blurring of the clear boundaries of one species/subspecies. Most known varieties Danio rerio is “Albino Danio”, “Leopard Danio”, “Golden Danio”, “Blue Danio”. There is also a genetically modified species that has a fluorescent element added to its genome, allowing the fish to glow in the dark. The fish first became commercially available in the United States in 2003.

Requirements and conditions:

  • Aquarium volume - from 40 liters.
  • Temperature - 18–24 °C
  • pH value - 6.0–8.0
  • Water hardness - soft to medium hard (5–19 dH)
  • Substrate type - dark fine gravel or sand
  • Lighting - dim
  • Brackish water - no
  • Water movement - moderate

Fish parameters:

  • Size - up to 7 cm.
  • Food - any food floating on the surface
  • Life expectancy - from 3 to 4 years

Habitat

Danio Rerio received scientific description in 1822 while studying the flora and fauna of the colonial possessions British Empire in the territories modern India and Pakistan. Fish are widely represented in river systems of Asia from Pakistan to India, including South-East Asia in Burma (Myanmar).
The fish lives in the lower reaches of rivers, streams, canals, as well as in ditches near settlements and ponds. The habitat can vary significantly depending on the time of year. During the rainy season, fish rush to flooded fields (in particular rice fields), where spawning occurs in a quiet backwater with dense vegetation. Adult fish return back to the rivers, followed by the emerging juveniles after a few days.

Description

A beautiful slender fish, it has a laterally compressed body, the tips of each lip are crowned with small antennae, characteristic of most cyprinids. The color is pale yellow or silver, with five horizontal dark blue stripes running throughout the body, which also extend along the tail and anal fin.

Nutrition

Fish accept almost any food intended for aquarium fish, the main condition is that they must swim on the surface; Danio will never pick up from the bottom. Specialized dry or freeze-dried food for this type of fish is widely available on sale, taking into account all their needs for vitamins and microelements. You can diversify the food by sometimes adding live food, mainly bloodworms.

Since the fish has lived in an artificial environment for many generations, it is well adapted to various conditions, so there are no problems in keeping it. It is enough to ensure good filtration and aeration of the aquarium; both of these processes also create water movement, which has a beneficial effect on Danio. The fish lives in the upper layers of water and leads an active lifestyle; during its games it can jump out of the aquarium - take care of the protective cover.
Optimal conditions are those that mimic their natural habitat. Large spaces for swimming in upper parts aquarium, dense vegetation on the sides along the walls. A substrate of dark gravel or sand will highlight the color of the fish.

Social behavior

An active, peaceful fish, it has a peaceful temperament and never shows aggression towards other species. Shared keeping is possible with other species of Danio, as well as with some small (no more than 5–6 cm) peaceful species. You should be careful when choosing slow-moving fish; excessive activity of Danio Rerio can negatively affect their well-being.
It is mandatory to keep at least 5 individuals in a flock; when kept alone or in pairs, the fish becomes lethargic and susceptible to various diseases.

Breeding/reproduction

Sexual differences are weakly expressed, females are only slightly larger than males, body coloring is the same in both sexes. Danio Rerio often forms couples that last a lifetime, but that’s where the romanticism ends. Parental instincts are weakly expressed; they can happily eat their eggs and do not participate in raising offspring. A separate tank is required for spawning.
The spawning aquarium can be small, 20–25 liters. The bottom should be strewn with balls with a diameter of 1 cm or gravel of similar size. Arrange plants in dense groups. The composition of the water can be similar to that in a general aquarium.
When it is noticed that two fish constantly stay together, and one of them has a swollen abdomen, it means that the female will soon lay eggs. The female is transplanted into a separate tank first; the male joins only the next day. The stimulus for spawning is a rapid drop in temperature; you can pour a glass of cold water directly into the spawning aquarium - this is an imitation of the rainy season. The female releases the eggs directly into the water, and the male fertilizes them. Sinking to the bottom, they roll into the spaces between the soil particles and become inaccessible to their parents. At the end of spawning, the couple is returned back to the common aquarium, and the fry appear after 7 days.

Diseases

Fish are very hardy; the disease can only be provoked by a significant deterioration in conditions or contact with sick fish. Read more about symptoms and treatment methods in the section “Diseases of aquarium fish”.

Peculiarities

  • School keeping of at least 5 individuals
  • Can jump out of aquariums
  • Requires food floating on the surface

Usually it does not create any problems during the growing process. But, like other inhabitants of the aquarium, she can get sick and therefore you need to know how to cure your pet.

When purchasing Danio, Special attention Pay attention to the integrity of the skin and fins. At the same time, faded color does not always indicate illness; simply moving or replanting during the sale process could cause shock.

But even if the zebrafish looks healthy, it must be kept in a separate aquarium in quarantine for a couple of weeks.

Zebrafish are very disease resistant. And yet, despite the fact that she gets sick very rarely, you need to have aeration in the aquarium.

For proper maintenance and prevention of diseases in zebrafish, the regime is very important. clean water. When feeding her, you must adhere to the rule - it is better to underfeed than to overfeed. Overfeeding is usually the cause of illness.

Also, to prevent diseases, you need to follow simple rules. All items brought into the aquarium must be disinfected: in a solution of manganese, in boiling water or using other disinfectants.

Let's look at the main diseases and methods of how to deal with them in order to meet the problem head on!

Main diseases of zebrafish

Bloating

Danio pink very thick

The first signs of the disease are an increase in the abdomen by 2 times. Some aquarists confuse this with overeating or spawn, but in most cases it is bloat.

Zebrafish are prone to it and very often their owners encounter this problem. Danio lies on the bottom, practically does not swim, does not come into contact with fish, and its belly is much larger.

Treatment is metronidazole (1 tablet per 30 liters of water). In a week the disease should go away. For prevention, you can also “drink” other inhabitants in the aquarium - there is nothing wrong with that.

Pink Danio swims sideways

In some cases, the fish begin to swim in a circle, but remain quite active and react to other participants in the “movement”. As a rule, this behavior occurs during poisoning. Some individuals are very sensitive to the amount of nitrates, so you just need to replace the water with normal composition and periodically (once every 3 days) change 1/3 of the aquarium water.

Growths

There are practically no such growths on zebrafish, but if such a disease occurs, then you just need to increase the salinity of the water and the temperature. Place the fish separately in a jar and add 2 tablespoons of salt. Keep it there for 15 minutes at +28 degrees, then put it back into the general aquarium. The fluffy growths will die and come off in a couple of days.

Bug-eyed

Most often they suffer from bulging eyes. The disease usually affects them at the age of several years during spawning. The body color does not change, but the abdomen noticeably increases, which looks natural during the spawning period. Over the course of two weeks, both eyes protrude more and more out of their sockets, then fall out one by one. The blind fish dies from exhaustion. When opened, a thick white mass is found behind the eyeball, which causes bulging eyes. The reason is poor quality water. Treatment: partial water change every 2 days.

Danio pink turned white

Trichodinosis

The causative agent is the ciliate Trichodina, which has spine-like processes with which it attaches to the fish. Localized on the gill filaments and skin. Enters the aquarium along with plants, soil and food if they have not been properly disinfected.

Signs of the disease: the fish begins to rub against hard objects and plants, and more often than usual swims up to aeration bubbles. As the disease progresses, the color of the fish fades, and a grayish-white coating is visible on the skin, which is separated in flakes. Treatment of trichodinosis: increased aeration, increased water temperature to 31 degrees. Therapeutic baths are made in a separate or common aquarium with table salt or trypaflavin.

Danio pink loses weight

Tuberculosis

How to carry out treatment? It is best to feed fish food with kanamycin or rifampicin.

You can simultaneously add these medications to the water of the aquarium or special aquarium in which the treatment is being carried out.

If the fish no longer eats, but you really want to save it, then you need to remove it and add medicine to the water.

Kanamycin - 3 g per 100 l, rifampicin - 600 mg per 100 l of water.

Antibiotics should only be added to the aquarium if emergency. They kill nitrifying bacteria in the soil and filter, and disruption of the biological balance is inevitable when using them.

Adding antibiotics to the feed will be the best solution to the problem. The easiest way is to soak bloodworms (live ones are better, but high-quality ice cream will do) in a strong solution of kanamycin (0.5-1 g per 50-100 ml of water) for half an hour to an hour, and then feed it to the fish.

One feeding per day should be with this food. Noticeable improvements occur after a week's course.

After two weeks, the fish begin to look quite healthy and treatment can be stopped.

For prevention, it is worth conducting monthly weekly courses. It is difficult to saturate other foods with antibiotics. It will be washed out very quickly, which will negatively affect the beneficial microflora of the aquarium. So bathing bloodworms in medicine is the right thing to do.

Danio pink loses color

Alkalosis

Symptoms:

  • Cough,
  • Excited behavior
  • Jumping out of the water
  • Labored breathing
  • Scratching
  • Bloating
  • Lightening the color
  • Spread fins
  • Excessive mucus production

Acute alkalosis: the fish have dull skin, splayed fins, rapid breathing, mucus is released from the gills, the fish begin to rush around the aquarium, trying to jump out of it.

Chronic alkalosis: Signs are less obvious and include difficulty breathing and "coughing", excessive mucus production and itchy skin as a result of irritation caused by high acidity or alkalinity of the water. Problems with osmoregulation caused by chronic alkalosis can lead to bloating

This condition occurs when the pH aquarium water above the pH range optimal for fish of a given species.

This disease does not necessarily affect all aquarium inhabitants, because fish different types differ from each other in the range of pH values ​​acceptable for them.

The disease may be acute if the change in pH occurs quickly, or chronic if the change occurs gradually over a period of time.

Alkaline water irritates the external surface of the fish's body (including the gills) and can cause adverse physiological changes.

Treatment

A suitable pH level must be set. This can be achieved using a suitable pH buffer (available from a pet store).

To slowly adjust the pH, it is better to use repeated partial water changes, and fresh water should have a pH close to neutral. This is the best way to solve pH problems, since repeated partial water changes will eliminate the main cause - reducing the too high mineral content, which usually leads to chronic alkalosis.

Preparations:

  • pH buffer
  • timely water changes

Prevention:

Prevention. Alkalosis can be prevented by selecting fish species for which the aquarium water has a suitable pH value, or by changing the pH level so that it suits the intended inhabitants of the aquarium, while they themselves must be compatible with each other in relation to pH.

Choose a tank design that does not adversely affect the desired water chemistry. Check the pH value regularly to detect the first signs of leaching due to calcium contained in aquarium decorations.

Acute alkalosis: survival from sudden large changes in pH is unlikely unless the pH is immediately returned to normal level. If the pH is returned to normal gradually, then the fish will be exposed to the harmful effects of an inappropriate pH for too long.

However, acute alkalosis is usually fatal, even if corrected quickly. Therefore, it is very important to determine the cause of the problem and take action. necessary measures to prevent it from happening again.

Chronic alkalosis: The pH needs to be slowly adjusted to bring it within the optimal range for the fish. The rate of pH change should not exceed 0.3 units. per day so that the fish have the opportunity to gradually adapt to the changes.

There is a risk of infection that accompanies or follows alkalosis. This infection is possible as a result of stress-induced suppression of the fish's immune system (especially if the problem is chronic).

Due to inappropriate pH values, gills and skin membranes are damaged, making them vulnerable to secondary infections.

Danios are fish that appeared in my aquarium thanks to my dad. This is after I swapped my gouramis for neons. Out of a dozen zebrafish of two types (striped and pink), there are now 5 left. You should think about purchasing more or just try to breed these funny fish. But that's in the future. I decided to collect on this page the most full information about aquarium zebrafish, along with my photos and not my videos

By the way, zebrafish are quite agile fish and were extremely difficult to photograph. In general, I wouldn’t really like to have such fish darting around the aquarium in my relaxing pond. But my father decided differently.

Danio (lat. Danio) is a genus of small ray-finned fish of the carp family, some species are common in the aquarium hobby. They inhabit bodies of water with standing and running water South-East Asia. The most popular in the aquarium hobby is zebrafish.

Zebrafish is a model organism in developmental biology and is known in English literature as zebrafish. The zebrafish is the first pet to be genetically modified with bioluminescent genes in 2003 (GloFish)

GloFish is a patented commercial brand of GloFish, under which genetically modified fluorescent fish are sold; originally these were zebrafish (lat. Danio rerio) - a species of unpretentious and popular aquarium fish of the carp family. A distinctive feature of GloFish individuals artificially bred by genetic modification from the original form is a red, green or orange fluorescent color, which becomes more noticeable and intense under ultraviolet light. Although the fish were not originally bred as ornamental fish, they became the first publicly available genetically modified pet.

Transgenic zebrafish differ from their original form in body coloration. Their DNA contains DNA fragments from jellyfish (Latin Aequorea Victoria) and red coral (from the genus Discosoma). Zebrafish with a fragment of jellyfish DNA (GFP gene) are green, those with coral DNA (RFP gene) are red, and fish whose genotype contains both fragments are yellow. Thanks to the presence of these foreign proteins, the fish glow brightly under ultraviolet light.

The transgenic form prefers warmer water - about 28 °C. Maintenance, feeding or differences in breeding and development of genetically modified Danio rerio were not noticed: transgenic fish are also unpretentious in maintenance and peaceful.

History of GloFish

The natural zebrafish from which GloFish was grown lives in rivers in India and Bangladesh. It measures about three centimeters in length and has gold and blue stripes along its body. Over the past 50 years, these fish have been sold for over $200 million on the US ornamental fish market, but despite this, no one has reproduced them in the US, primarily because they are tropical fish and cannot exist in conditions of the temperate North American climate.

In 1999, Dr Zhiyuan Gong and his colleagues at the National University of Singapore worked with the green fluorescent protein (GFP) gene, which nature has endowed only with some Pacific jellyfish. This gene is responsible for the synthesis of a phosphor protein, which in the dark emits rays of a pleasant greenish color. They inserted this gene into a zebrafish embryo, creating a genome that gave the fish a bright fluorescent coloration from both natural white light and ultraviolet radiation.

The original goal of genetic engineers was to make it easier to monitor internal organs these translucent fish. But a photograph of a fish glowing with a greenish ghostly light, shown at a scientific conference, was seen by a representative of a company that breeds and sells aquarium fish. At the request of the company, another red glow gene was added to the zebrafish genome, isolated from sea ​​coral. The resulting breed was named “Night Pearl”.

In the United States, glowing zebrafish were originally obtained for the purpose of creating living indicators of pollution: in the presence of certain toxic substances in the water, the fish were supposed to change color. But in 2003, businessmen and scientists entered into a contract under which the first genetically modified fish, GloFish, appeared on the market.

In addition to the red fluorescent zebrafish sold under the brand name Starfire Red, green and orange-yellow fluorescent zebrafish were developed by mid-2006, followed by blue and purple ones in 2011. These fish genetic lines have been branded Electric Green, Sunburst Orange, Cosmic Blue and Galaxy Purple. .Galactic Purple). All of these fish were genetically engineered using recombinant DNA from various sea corals.

In 2012 appears new variety fluorescent aquarium fish under the brand name of the green English variety. “Electric Green” GloFish, which were bred using the same method as the previous ones, but instead of zebrafish, common ternets (lat. Gymnocorymbus ternetzi) were used. In 2015, green glowing Sumatran barbs (Puntius tetrazona) were introduced.

Despite the widespread opinion about the sterility or sterilization of genetically modified fish in order to prevent them from spreading in natural bodies of water, completely healthy and viable offspring can be obtained from GloFish. and the sale of fluorescent GloFish fish is strictly prohibited.

The sale and possession of GloFish remains illegal in California due to regulations restricting the breeding of any genetically modified fish. The regulation came before GloFish sales began, largely due to concerns about the biotechnology of fast-growing salmon. Although the fish commission refused to grant an exemption (on ethical grounds) in December 2003, it subsequently changed course and decided to move forward with the goal of exempting GloFish from regulation.

Canada also prohibits the import and sale of GloFish due to a lack of sufficient information to make a safety decision.

Within European Union The import, sale and storage of these fish is not permitted. However, on November 9, 2006, the Ministry of Housing, Territorial Planning and environment 1,400 fluorescent fish have been found in the Netherlands and are sold in various aquarium stores.

But let's return to zebrafish. Danio rerio is a model organism used to study vertebrate development and vertebrate gene function. Early work by George Streisinger at the University of Oregon showed the potential for Danio rerio to be used as a model organism; the importance of this model has been confirmed by many genetic studies. Danio rerio is one of the few species of fish that has been on the orbiting space station.

As an object of developmental biology, Danio rerio has some advantages over other vertebrates. The embryo develops quickly, going from egg to larva in just three days. The embryos are large, hardy, strong, transparent and develop outside the mother, which makes them easier to manipulate and observe.

Antisense Morpholino technology is often used to turn off genes or change splicing in Danio rerio. Such oligonucleotides are synthetic macromolecules containing DNA or RNA nucleotides that bind to complementary RNA sequences and reduce gene activity. Morpholino oligonucleotides can be introduced into embryonic cells after the 32-cell stage, resulting in an organism in which gene activity is reduced only in those cells that originate from the modified cell. Although the cells of the early embryo (less than 32 cells) are impermeable to large molecules, they allow Morpholino molecules to penetrate between cells.

On January 23, 2013, Spanish scientists conducted an experiment to introduce the hoxd13 gene, borrowed from four-legged mice, into the fish genotype. Fish have a similar gene, but it does not show sufficient activity. As a result of the experiment, fish received the rudiments of limbs suitable for movement on land

Species of zebrafish from kwitri.ru

The most common species in modern aquariums remains zebrafish, or zebra danio. Like other species, the female has a more rounded abdomen. Veil forms are often found. The body length of the fish is up to 7 cm.

And they are very similar in color and size. The main difference is the orange stripe that runs from the middle of the body to the caudal fin of the pearl danio. The body length of the fish is up to 6 cm. This species looks more advantageous with the right lighting. The fish reach sexual maturity at eight months.

Leopard zebrafish received this name for the corresponding coloring - there are many dark-colored spots throughout the body irregular shape. The body size of the fish is up to 5 cm.

Orangefin Danio- got its name because of the color of the fins, their edges are yellow-orange. In sexually mature males the coloring is more pronounced. The body length of the fish is up to 5 cm.

Firefly Danio, or zebrafish chopra - small (up to 3 cm in length), bright fish, painted in orange-yellow tones. The caudal fin appears forked due to the outer rays painted yellow, while the central part remains transparent. A luminous stripe runs along the crest of the back from the head to the dorsal fin, and in females it is yellowish, in males it is reddish. Mature females have a bright orange stripe running along their body.

Danio dangila, or olive – quite major representative family, its body length is up to 10 cm. The body is covered with a peculiar ornament, the distinctive feature is a large dark spot behind the gill cover. It is not advisable to keep this species with fish that have veiled fins, since these zebrafish in a school can tear off these same fins. In general, this species (when kept in a school) is quite aggressive; dangil danios can attack larger fish.

Danio erythromicron, or microrasbora ribbon, emerald - a small fish (2.5 cm) of a very original color. Distinctive feature This zebrafish has no whiskers. Peaceful, shy fish, so it is very desirable to have vegetation in the aquarium in which they can hide.

Danio Burmese, or fagradei - fish with a delicate color: golden spots are scattered across the blue body. There is an orange spot behind the operculum. In males, on the anal and ventral fins There is an orange stripe, in females it is white.

Danio blue, or Kerry, is a fish with a memorable color: two sparkling pink stripes run along its olive-blue body. The male is smaller, slimmer and brighter; the color of the females is dominated by gray tones. The body length of these fish is up to 5 cm. The species is peaceful.

Danio malabar- the largest representative of the genus. The body length of the fish in the aquarium is about 10 cm. The color is very interesting: along the body, slightly retreating from the head, there are 3-4 shiny, longitudinal bluish-turquoise stripes, separated by golden stripes. Immediately behind the gill cover there are several transverse golden strokes and specks of the same color are scattered throughout the body of the fish. In the male, the middle longitudinal blue stripe continues in the middle of the caudal fin, and in the female it passes to the upper lobe. The view is peaceful. These zebrafish reach sexual maturity by one year.

Fluorescent zebrafish, or Danio GloFish - p The fish, according to the conditions of detention, is no different from the original species - zebrafish - unpretentious, schooling and mobile for the upper layers of water in the aquarium.

Danio bengal- a peaceful, unpretentious, schooling fish with a body size of 7-8 cm. At the level of the dorsal fin on the side of the body, 3 blue longitudinal stripes begin, separated by lines yellow color, which on the caudal fin merge into one stripe, passing onto its upper blade. Of all the zebrafish, this species has the longest dorsal fin. Males, like other species, are more graceful and brighter in color.

Danio punctata– the color of the upper part of the body resembles the zebrafish: the same dark stripes on a light background. The lower part of the body and the anal fin are covered not with stripes, but with dark dots. The caudal fin also has dark stripes. The length of the fish is no more than 4 cm. Male smaller than a female, its abdomen is white, the female’s is orange. The view is peaceful. For this species, the water temperature should not be lower than 24 ⁰C.

Danio margaritatus, or microrasbora galaxy, is the brightest representative of zebrafish. These fish begin to acquire their bright colors at the age of two months, and by six months they are completely colored. These fish are very beautiful, but their extreme shyness prevents you from admiring them enough. The aquarium with them must be planted with plants so that the galaxies feel calmer. These fish are kept in large schools of 20 or more individuals. The water temperature for them should be no higher than 26⁰C, preferably 22-24⁰C.

Since, if danger approaches, these fish can jump out of the water straight into the air, so that the pet does not get lost, the aquarium should always be covered. The optimal distance from the water to the lid is approximately 3-4 cm, so that when the fish jumps out, it does not hit a hard surface and is not injured.
Keeping and caring for zebrafish at home is quite simple. Fish mainly swim in the upper layers of water, where there is the most oxygen. In this regard, you will not need to install additional aeration for the aquarium.
Danio rerio live in groups. Therefore, if you decide to purchase them, buy 8-10 individuals at once. Since the size of these fish is small - about 4 - 5 cm, an aquarium with a volume of 6 to 7.5 liters is quite suitable for their comfortable living. The optimal water temperature for zebrafish should be around 24°C. Although these fish will react quite calmly to minor changes.
If you want to breed zebrafish yourself, then you need to prepare another aquarium - a spawning tank. The thickness of the water in it should be no more than 6-8 cm. After spawning, the female and the male are seated in different aquariums, after which 7 days later the female is released again for re-spawning, in order to avoid her infertility.
Feeding zebrafish is also an important process. Suitable dry or live food for this species is suitable for this purpose. It is very important that the food is chopped, otherwise the fish will not be able to swallow large pieces.

Compatibility of zebrafish with other fish

If you have added these beautiful aquatic inhabitants to your home living area, you can rest assured, because zebrafish get along well with most types of aquarium fish. They get along well with catfish, cockroaches, neons, tetras, gouramis, lalius, swordtails, ancistrus, platies, rainbows, rasboras, mollies, bots, guppies, cockerels, angelfish, Corydoras catfishes and labeos. Also, “danichki” get along quite well with snails, shrimp and ampullaria.
Despite the good compatibility of zebrafish with other fish, there are some caveats. If you have a barb or some other type of more aggressive fish in your aquarium, do not put a veiled zebrafish with them, because. nimble residents may damage or bite off their veil and long fins.
Danios should not be kept in the same aquarium with goldfish, eels, cichlids, astrotonus, discus fish and koi carps.

Zebrafish diseases

Unfortunately, despite all the charm and unpretentiousness of these fish, they have one flaw. This is a congenital disease of zebrafish, which appeared from breeders - a curvature of the spine. The main symptoms are raised scales, splayed gills and slightly bulging eyes. Most often they all appear after a fright. After a few days, the central vertebra of the zebrafish begins to bend, and as a result, after some time the fish dies.
A known disease of zebrafish is also dropsy. The fish develop raised scales, their eyes bulge, their belly swells, and eventually death occurs.

How to distinguish zebrafish? Female or male zebrafish?

The website kakprosto.ru has instructions on how to distinguish a female from a male zebrafish. I'll give it here.

Only adult individuals can be distinguished from each other by gender, since young fish are not yet fully formed and are very similar to each other. If gender matters to you, be sure to purchase only adult, fully formed fish, only in this case you will be able to more or less accurately determine which of them is male and which is female. Also make sure that all the fish in the aquarium are the same age, as this significantly affects their size. Young females can easily be mistaken for males when compared with older fish.

The most accurate criterion for determining sex in zebrafish is size. Look at a school of fish and try to compare them with each other. Females are usually larger and have a rounded abdomen. Males, on the other hand, have a slender build and are slightly smaller in size than their female counterparts. This structural feature is associated with the ability to produce eggs and bear fry, which directly depends on the size of the female zebrafish.

Pay attention to the intensity of the color of the fish. The stripes on the body of females are paler and less noticeable, while male zebrafish are usually brightly colored and shimmer very clearly. This coloration is evidence of good camouflage of the fish. Pregnant females are more clumsy and slow, so they should not stand out in sea thickets or against the background of the bottom.

Zebrafish Reproduction

The website aquavitro.org describes zebrafish reproduction in great detail. I'll quote the article here.

Majority research work on the topic of zebrafish reproduction have focused on maximizing egg production (Laale, 1977), and until now virtually nothing was known about the reproductive ecology of wild specimens. In the early stages of development, the ovaries act as gonads in zebrafish, and only at 5-7 weeks, with a length of 10-15 mm, male individuals begin to differentiate. However, the final intersex period and complete formation of testes in males ends approximately in the third month of postembryonic development (Devlin & Nagahama, 2002; Maak & Segner, 2003). The genetic mechanisms of sexual determination are unknown. However, there is evidence that the rate of differentiation is influenced by food availability and growth rate. In this case, fast growing and large individuals become females, and small ones become males (Lawrence, Ebersole & Kesseli, 2007). Based on samples collected from a population in the Brahmaputra River, the natural sex composition was found to be 1:1 (Spence et al., 2007a). Domestic zebrafish breed in the laboratory all year round , while natural ones are seasonal. However, large females caught in January (that is, long before the start of the spawning period) had mature eggs, which indicates that the availability of food rather than the season influences reproduction (Spence et al., 2006a). In addition, the onset of puberty is related to size rather than age; wild and laboratory zebrafish matured being similar in size, regardless of their growth rate. Eaton and Farley (1974a) showed that at 25.5°C, domestic zebrafish rarely become sexually mature before 75 days, when females reach 24.9 mm in length and males 23.1 mm. In laboratory conditions, the first generation of zebrafish is also ready to spawn at approximately 23 mm in length. Pairs of zebrafish remain together and reproduce continuously, but spawning cycles are irregular (Eaton & Farley, 1974b). During spawning, one female produces small packets containing several hundred eggs. The intervals between egg laying vary from 1 to 6 days and average 1.5 days. At the same time, batches of 1-700 eggs are laid (average value 185) (Spence & Smith, 2006). The size of the packs correlates with the size of the female, as well as the interval between spawnings. It was reported that this interval increases as the female matures, from 1.9 days for a one-year-old individual to 2.7 days for an individual 15 months old. In addition, clutch size also increases, from 158 to 195, respectively (Eaton & Farley, 1974b). Ovulation depends on the extent to which females are exposed to the male's gonodal pheromones. Males release into the water a homogenate of the testes and a fraction of the gonads containing steroid glucuronides, which cause ovulation. Interestingly, no reactions to pheromones were observed in anosmic females in which the olfactory epithelium was cauterized (van den Hurk & Lambert, 1983; van den Hurk et al., 1987). Eaton & Farley (1974b). The presence of males for 7 hours in the evening is sufficient to initiate female spawning the next morning (Eaton & Farley, 1974b). In isolated females who have been in contact with a male for a period of at least 5 days, spawning is never observed twice. This indicates that all mature eggs are released in one spawning cycle (Hisaoka & Firlitt, 1962; Eaton & Farley, 1974b). The presence of a male is necessary for the maturation of eggs in females. In isolated or old females, the eggs begin to stick together into aggregates, which often leads to their death. Examination of sick individuals revealed the presence of rotting eggs stuck to the oviduct and preventing successful mating. Regular contact with the male and spawning eliminates the development of necrotic foci. It is interesting that, despite the cyclical and variable nature of spawning, females in contact with the male several days before spawning demonstrate better fertility and egg quality compared to individuals isolated for several days (Gerlach, 2006). This effect is associated with the concentration of the pheromones presented. Both sexes have been shown to secrete pheromones that act as attractants before and during reproduction (Bloom & Perlmutter, 1977). Moreover, sensitivity to their action is higher during spawning. Zebrafish eggs do not have an adhesive shell and are dimersal (bottom-based). Their diameter is 0.7 mm. Spawning takes place directly over the substrate, which is not prepared in advance. Producers do not take care of their offspring. Both fertilized and unfertilized eggs are activated upon contact with water and undergo a series of programmed developmental stages. Unfertilized eggs develop into the vitelline space, but the process stops long before the first divisions (Lee, Webb & Miller, 1999). The incubation period at 28.5°C varies from 48 to 72 hours, depending on the thickness of the chorion and the activity of the embryonic musculature (Kimmel et al., 1995).

Immediately after hatching, the 3 mm long larvae are attached to the substrate using small secretory cells located on the head (Laale, 1977). Attachment at a higher level allows the surface to be accessed for swim bladder inflation (Goolish & Okutake 1999). This process is observed by 72 hours after fertilization, after which the juveniles begin active swimming, feeding, and develop avoidance behavior (Kimmel et al., 1995). Direct reproduction of zebrafish As is known, the spawning of domestic zebrafish depends on photoperiod (Breder & Rosen, 1966). Individuals exhibit a diurnal pattern of activity synchronized with day/night and feeding cycles. The first peak of activity is observed immediately after the start of illumination, and the next two peaks are observed at the beginning of the evening and in the last hour daylight hours(Baganz et al., 2005; Plaut, 2000). Spawning is associated with an early peak, usually starting within the first minute of light after dark and lasting for about an hour (Darrow & Harris, 2004). Field observations have shown that zebrafish reproduction in nature is also largely limited to short periods of time at dawn (Spence, Ashton & Smith, 2007). However, compared to domestic animals, wild individuals have a greater tendency to breed at times other than dawn. Lengthening daylight hours may be a factor triggering reproduction in the natural habitat. Adding cold water to the aquarium also promotes spawning in aquarium conditions (Breder & Rosen, 1966). Thus, a decrease in water temperature or an increase in its level serves as an additional signal for zebrafish. In nature, these fish spawn during periods long rains . Courtship during breeding involves the male chasing the female, touching her flanks with his muzzle, swimming with his fins spread around her in a figure of eight or circles, and guiding the female to the spawning area. If the female does not follow him, then the male continues to circle from her to the spawning site. Directly above the selected substrate, the male swims close to the female, spreads the dorsal and caudal fin around her body so that the genital pores of the individuals come closer together, and the male himself can twitch with a high frequency and low amplitude. This behavior triggers the simultaneous release of eggs and sperm. During one spawning it is repeated several times, and at each stage the female releases 5-20 eggs. The male's courtship is most active in the first 30 minutes, although it lasts about an hour, while the female spawns in the first half hour (Darrow & Harris, 2004). Wild zebrafish exhibit similar territorial and courtship behavior (Spence et al., 2007b). Under natural conditions, males are forced to pursue the female throughout the entire thickness of the water, while the female rises to the surface and then sinks to the bottom to the spawning site. Usually 3-7 individuals are involved in the race. Courtship on the part of the male is triggered by the pheromones of the females. Males, but not females, were attracted to egg extract added to the aquarium (Hurk & Lambert, 1983). Anosmic males (lack of smell) showed no courtship behavior, while controls courted only ovulating females. In addition, anosmic zebrafish were extremely aggressive, suggesting an inhibitory effect of pheromones on feeding aggression in both sexes. Danios display a reproductive pattern common to many cyprinid fish; they exhibit group spawning and free scattering of eggs (Breder & Rosen, 1966). Females spawn directly on bare substrate, but when provided with a good artificial substrate, such as a plastic surface, they prefer to lay their eggs on it (Spence & Smith, 2005). Some male zebrafish are territorial during spawning (Spence & Smith, 2005). Both territorial and regular males exhibit similar courtship displays. However, while non-territorial fish pursue females, the activity of territorial fish is limited to a distance of several body lengths from the spawning site, from which they drive away males. Aggression in territorial individuals has been studied in studies that vary sex ratios and group densities (Spence & Smith, 2005). It turned out that its degree increases depending on the planting density. Courtship behavior increased with increasing proportion of females, whereas in the male-dominated group, courtship rates decreased to levels observed at low stocking densities. The reproductive success of territorial males has been shown to depend on stocking density (Spence, Jordan & Smith, 2006). At low densities, territorial individuals produced significantly more offspring than non-territorial individuals. The opposite trend was observed with increasing group size. Thus, male zebrafish demonstrate two reproductive tactics: site guarding and active pursuit females, whose success is related to population size. High stocking densities result in reduced egg production by females (Spence & Smith, 2005). This phenomenon is determined by a decrease in the number of eggs in packs released per spawning, rather than by the removal of some females from breeding (Spence et al., 2006b). There are several explanations for this; An increase in male-to-male aggression may influence female competition and access to spawning grounds. Additionally, decreased egg production may be due to inhibition by pheromones emitted by other females. It has been shown that females exposed to the pheromones of other females prior to spawning are less willing to breed compared to isolated fish (Gerlach, 2006). It is worth noting that dominant females produce more eggs (Gerlach, 2006). Studies using large 2 x 2 meter aquariums have demonstrated female avoidance of each other, and, moreover, the effects of each other's pheromones (Delaney et al., 2002). Females prefer to be in groups consisting of one or more males than females. Thus, competition plays a role in the reproduction of zebrafish, both among males and females.

Sexual partner preferences. Relationship between male and female zebrafish

Under natural conditions, it is difficult to determine female preferences in species where males compete for mating opportunities. IN in this case The dominance of one or another male plays a key role. However, there is evidence that females prefer larger males (Pyron, 2003). This is consistent with evidence that the body size of bony fishes correlates with their dominance in the group (Wootton, 1998). When egg production was considered as a criterion of preference, females showed preference for certain males (Spence & Smith, 2006). However, there was no correlation with either male dominance or female choice (Spence & Smith, 2006). Suggestions have been made about the role of pheromones in choosing a sexual partner. In particular, female zebrafish prefer the odors of alien males over their own brothers (Gerlach & Lysiak, 2006). It is possible that two mechanisms of sexual selection, male competition and female preference, are simultaneously involved in reproduction. For example, if a female does not want to mate with a dominant male, then he can still do it to the best of his ability. In addition, competition among males for mating may be in close interaction with competition among females (Gerlach, 2006). In fact, reproductive success is similar among male and female zebrafish, and sexual selection plays a minor role (Spence et al., 2006b). This is confirmed by their weak sexual dimorphism.

Selection of substrate The female prefers a specific substrate for laying eggs. In studies with domestic and wild specimens in separate cages, it was found that females prefer gravel bottoms rather than muddy bottoms (Spence et al., 2007b). Territorial males also tend to defend bottom gravel areas. This behavior is explained by the much better survival of eggs on a solid substrate, where they are supplied with oxygen and also protected from cannibalism. In laboratory conditions, preferences for plant thickets were also revealed, although the latter do not affect the safety of the masonry in any way. However, plants make a significant contribution to increasing larval survival; they provide attachment sites and help reach the surface for swim bladder inflation (Laale, 1977). In natural areas where zebrafish are the predominant species, such as floodplain ponds, the substrate is often muddy, and the fish wade to spawn in shallow waters among vegetation that protects them from predators (Engeszer et al., 2007; Spence et al., 2007b) . Thus, the choice of producers is aimed at places with better water circulation, where there are no predators. Finding spawning areas is one of the few mechanisms in species that do not exhibit parental care. It helps to increase the survival rate of clutches and larvae.

Zebrafish fry

Zebrafish fry require a live starter food, but substitutes can be used if necessary. Let's consider, as advice, the most important points zebrafish rearing, where zebrafish fry grow in winter period and do not receive live, complete food.
By the time the zebrafish fry swim, you need to be prepared in advance. Zebrafish fry eat boiled yolk quite well, and will have to be used as a starter feed. To raise several hundred fry, one will be enough chicken egg. Boil the egg and separate the yolk from it, so that the yolk does not spoil; it should always be stored in the refrigerator.
Before feeding the fry, take a transparent glass or jar, fill it with water, then take the yolk, cut off the top of it and rub the surface of the cut part of the yolk with your index finger or a watercolor brush, then rinse the brush or finger in a jar of water.
After the suspended yolk particles settle to the bottom, drain muddy water and repeat this until the water becomes clear. Next, carefully and preferably pour the water with the yolk into the aquarium into the fry using the compressor sprayer.

Be sure to plant ampullaria in the aquarium; these snails, by eating uneaten particles of the yolk, are of great benefit by maintaining cleanliness in the aquarium. After 7-10 days, when the fry grow up, they need to be switched to larger food; a good transition would be to scraped beef heart.
It is very important to monitor the water temperature. An increase in water temperature increases the metabolism in the body of fish, the growth of fry also accelerates, but there is a limit to everything, crossing which means killing the fish.
Zebrafish fry grow well at a water temperature of 26° degrees; raising the water temperature above is not recommended. As the zebrafish fry grow, the water temperature must be gradually lowered.

The zebrafish fry eventually turn into these beautiful, in this case, pink large zebrafish.

Good luck with your zebrafish!

Danio rerio are active fish that live in schools with a clear hierarchy and have an interesting color.

Representatives of this type of fish were among the first to settle in aquariums and are still very popular among aquarists.

Danio rerio are unpretentious and do not require specific housing conditions, so even beginners in the aquarium hobby can cope with their maintenance.

What kind of fish is this?

Danio rerio (lat. Danio rerio) – freshwater fish family of carp genus zebrafish. Due to their beauty and lack of aggression, many species are popular in the aquarium hobby. In their natural environment, zebrafish can live both in small streams, canals and ponds, and in rivers.

The habitat depends on the time of year: during the rainy season, fish are localized in flooded rice fields and puddles, where they feed and reproduce, and at the end of the rainy season they return to rivers and large reservoirs.

The first mention of zebrafish dates back to 1822., when they were discovered in rivers and streams on east coast India, Pakistan, Nepal, Myanmar and Bhutan. They came to us in 1905-1906 and were re-introduced to the USSR in 1950.

Appearance

The fish has a narrow, elongated body, the maximum length of which in aquarium conditions is 5-6 cm; its lips are decorated with pairs of mustaches.

The body from the gill covers to the fin is decorated with parallel stripes of yellow, yellow-green and black-blue.

How to distinguish between a male and a female?

Females have a larger and rounder body than males and wide stripes on the abdomen, tapering towards the tail and head. The body of males is shortened and thin with brighter luminescent stripes.

The anal fin in males is short and pointed, in females it is long and rounded.

How long do they live?

In their natural environment, zebrafish live for about 1 year., in aquariums - 3-4 years, lifespan depends on conditions of maintenance and care.

Types and their photos

Glofish

Glofish is a genetically modified species of rerio with a bright color. These fish have low requirements regarding food and care, but they live in warm water up to 28 °C.

Veiled

This variety differs from the main one in having a long pectoral fin and a bushy tail reaching 2 cm.

Red

A variety obtained by implanting a sea coral gene into the DNA of a fish.

When kept in an aquarium, it reaches 5 cm in length. Along the red body are darker stripes running from the gill valves to the caudal fin.

Pink

Small fish, the body length of which does not exceed 6 cm. The pink color alternates with white stripes located along the body. They feel comfortable in a container filled with stones, driftwood, floating plants, at a water temperature of 18-22 °C. The species appeared in Europe in 1911.

Blue

The length of the translucent body is no more than 4 cm, the color can be pale gray-blue with a golden tint or rich, the fins are green with a yellow tint. The belly is bluish in color with golden stripes along it, and the fins are translucent. Females, as a rule, are grayer in color, males are slimmer, their color is more intense.

Firefly

A bright orange-yellow fish, the body length of which is 3 cm. The tail fin is transparent in the middle with bright yellow outer rays. Females have a yellow fin on their back, while males have a red fin.

Care and maintenance

Additional aeration is desirable, but it does not need to be installed, since zebrafish swim in the upper layers of water, where maximum amount oxygen. For the same reason The aquarium must always be covered, since in case of danger the fish can jump out of the water.

The volume of the aquarium depends on the number of fish: if you plan to keep 5 fish, a 20 liter aquarium is enough, if 10 or more, then the volume of the aquarium should be at least 35 liters.

Important! The aquarium should be long and narrow.

Daylight hours for an aquarium should last 10-12 hours; the rest of the time, artificial lighting is required at the rate of 0.5 W per 1 liter. water.

Small pebbles and gravel are used as soil. Preferable plants include Heleocharis, Vallisneria, Cabomba, Sagittaria and other long-leaved algae, which must be planted along the walls - a school of zebrafish should have an open area of ​​the aquarium with good lighting for swimming.

Hardness – 5-15 dH, acidity – 6.0-7.5 pH.

Once every 1-2 weeks it is necessary to change the water - approximately 20-25% of the volume of the aquarium, in addition, a good filtration system is needed that sucks up leftover food and waste. After some time, bacteria will appear in the filter tube, enriching the water with the necessary microflora.

Temperature

The water temperature in summer should be 20-25°C, in winter – 17-21°C.

Feeding

Under natural conditions they feed on various insects, seeds and larvae; in an aquarium they eat any food, preferring to swallow it from the surface of the water.

Dry food contains useful macro- and microelements, vitamins and minerals, but you should not constantly feed it to your fish. you need to alternate dry food with live food: bloodworms, artemia, tubifex.

When using bloodworms as food for zebrafish, it is necessary to wash it in advance and soak it in a solution of potassium permanganate for several hours.

Food must be given 2-3 times a day in small portions, since fish of this species are prone to overeating, which can lead to various diseases, bloating and accumulation of toxins, and uneaten food causes oxidation of water and the proliferation of harmful microorganisms in it.

The most popular foods for zebrafish are General Duna, Tetra, Sera, Denerle.

Compatibility with other aquarium fish

With the correct selection of aquarium neighbors, the quality of life of zebrafish significantly improves and its duration increases.

Peaceful The nature of zebrafish allows them to get along with almost all non-aggressive fish, for example with:

  • guppy;
  • platies;
  • mollies;
  • tetras;
  • swordtails;
  • rasborami;
  • minors;
  • thorns;
  • neon;
  • cockroaches.

Zebrafish are incompatible with large, aggressive and slow fish, such as:

  • acne;
  • angelfish;
  • koi carp;
  • discus;
  • astronotuses;
  • cichlids.

It is better to keep zebrafish in small schools of 10-15 individuals, where a clear hierarchy will be observed, and the entire family will be able to cope more easily with stressful situations.

Reproduction

Female zebrafish are not viviparous; they lay eggs, which are then fertilized by the male.

Spawning occurs in a separate container. This can be a small (10-15 liters) volume aquarium or, in extreme cases, a three-liter jar.

Place fontinalis or peristolium on the bottom, pressing down the algae with small stones so that they do not rise, and pour in fresh water, standing for at least 48 hours, the temperature of which is 23-26 °C. The water level above the algae should rise by 5-7 cm.

It is necessary to place a pregnant female and several males in a prepared tank 7-10 days before spawning. This should be done in the evening and in the morning the female will begin to lay eggs, producing 50-400 eggs at a time.

Reference! If spawning has not begun in the morning, it is necessary to leave the spawners in the spawning tank for another day, generously feeding them with live bloodworms and daphnia.

Once the process is complete, the spawners should be returned to the main tank and half of the water in the spawning tank replaced with fresh water. After 3-4 days, larvae appear from the eggs and settle on the walls of the tank; after a few days, fry appear, which must be fed with rotifers or ciliates.

As the fry grow, their diet needs to be changed. and after 20-30 days give them cyclops, daphnia or bloodworms. Over time, they need to be transplanted into a larger tank and fed like adult fish.

Diseases

In general, zebrafish have quite good health and disease resistance, which is one of the reasons for the popularity of this type of fish. However, if the conditions of detention are not observed, they may be susceptible to certain diseases.

Tuberculosis

This is an infectious disease that enters the aquarium with soil, algae or other infected fish. The fish become lethargic, lose their appetite, and scales fall out.

Tuberculosis can be cured only in the early stages of the disease. The main medicine is kanimycin, it must be mixed with food in equal parts.

Important! The infected fish must be kept in a separate container with water, and at the end of treatment, regardless of its outcome, general cleaning is required general aquarium and disinfection of decorative elements.

Bug-eyed

The most common disease in zebrafish that occurs due to unsatisfactory water quality.

Fish get sick during spawning, and the occurrence of symptoms is often not monitored, since the main one is an enlarged abdomen, which can be mistaken for a sign of pregnancy.

After a few weeks, a more serious symptom becomes noticeable - the fish’s eyes bulge and eventually fall out, which causes death.

Alkalosis

Alkalosis, or alkaline disease, occurs as a result of an imbalance in the acid-base balance of water. If the fish often jump out of the water, itch against the walls of the aquarium or its bottom, and their skin turns pale, these are signs of alkalosis.

To fix the problem, you need to install a pH buffer, maintaining the acidity of water at the required level.

Growths on the body

This problem occurs quite rarely and when it occurs, it is necessary to transfer the fish from the general aquarium to a separate container for quarantine, where the water temperature is 28 °C, to use salt baths.

Trichondiasis

This is an infectious disease caused by Trichodina ciliates, which occurs due to insufficient disinfection of objects placed in the aquarium. If a fish gets trichondiosis, it rubs against the walls of the aquarium, the color changes her skin becomes paler, and a dirty coating can be seen on her body.

It is necessary to increase the water temperature to 30 °C and take baths with trypaflavin or table salt.

Where to buy and what to look for?

When purchasing, you need to examine the skin of the fish and make sure that there are no signs of disease or mechanical damage on the body and fins.

Important! The fish may look too pale as a result of being frightened by the hand-to-hand transfer process.

After purchasing, you should place the zebrafish in a separate container to ensure its health.

The cost of fish depends on the rarity of the species. Common varieties of zebrafish cost from 35 rubles, fluorescent ones – from 45 rubles, and firefly zebrafish – from 137 rubles. per copy.

Video on the topic

Watch a useful video about zebrafish:

Conclusion

Danio rerio are unpretentious and at the same time very beautiful fish. With proper care, properly selected lighting and decor, an aquarium inhabited by fish of this species will decorate any interior for several years.

Diseases often affect weakened fish. Typically, the behavior of a sick fish differs from the behavior of other fish. A sick fish swims differently, breathes frequently, hides in thickets of plants, and itches on the ground or plants. A sick fish loses its appetite and its fins are compressed. All these are signs of the initial disease of the fish.

Often one of the causes of fish disease is their improper maintenance, so aquarium fish need to be closely monitored. If the fish grow in unfavorable conditions, then they become unarmed infectious diseases. Often fish get sick due to low water temperature and insufficient oxygen content in the water.

Also, one of the causes of fish disease is improper feeding. Fasting for adult fish practically does not harm them, but for fry it is a big minus. In the first days of life, fry need to eat well in order to grow. Overeating for adult fish causes obesity, which subsequently leads to their death, since obesity is not treated. Feeding monotonous food can lead to inflammation of the stomach and intestines. With this disease, the fish usually do not lose their appetite, but their color becomes darker and their movements are more constrained. Inflammation of the stomach and intestines in fish weakens them, and this is a high chance that the fish will catch infectious diseases.

How to cure fish?
1. When unfavorable conditions of detention, improper feeding and injury to fish, treatment simply involves creating optimal conditions for the fish.

Curable diseases: clouding of the fish's eyes, damage to the fins, mucus on the gills, changes in the color of the gills, fading of the color of the fish - all this is treated with short-term but repeated baths (water 30-32 ° C with a high concentration of methylene blue). Baths are also used if the fish move little and are covered with all kinds of specks or spots. In the intervals between baths, the fish are kept (as already described above) in a separate vessel.

Incurable diseases:
If a fish loses its balance and swims with its tail down or sideways, then such a fish is incurable.
Bug eyes in one or both eyes are incurable.
Tumors on the gills and skin of fish are incurable.