Crayfish eggs: methods of larval reproduction

Sometimes, when cooking crayfish, we notice that some individuals have roe under their tails. It is an amazing sight — lots of tiny eggs tightly attached to the female's abdomen. But how did they get there? The crayfish reproduction process is a whole story with its own rituals, struggles, and care for offspring.

It all starts with distinguishing males from females. This is not so difficult if you know what to look for. Males usually have larger and more powerful claws, and the first two pairs of abdominal legs are modified and serve as reproductive organs. Females have normal legs, but nature has provided a convenient place for carrying eggs under their wide tail.

Crayfish mating is a real adventure. The male must not only find a female ready to reproduce, but also hold her, often overcoming resistance. After fertilization, the eggs attach to the legs under the female's tail, where she spends long weeks constantly sorting and cleaning her future offspring.

Small crayfish are born looking similar to their parents, but they cling to their mother's abdomen for a long time until they grow stronger. Watching a female crayfish carefully guarding her offspring is one of the most interesting aspects of the life of these underwater creatures.

How crayfish reproduce

It is interesting to observe how crayfish reproduce. The age of sexual maturity depends on the species of arthropod:

• long-clawed river crayfish can reproduce by the age of 3.
• dwarf crustaceans reach sexual maturity at 3.5–4 months.

But it is not so easy for a young crayfish to reach sexual maturity. In water bodies, numerous molts make crayfish helpless, and they are often attacked by adults.

The age of sexual maturity depends on the species of crayfish

A female that has reached sexual maturity grows up to 7 centimeters, while dwarf species grow up to 6 centimeters. During the breeding season, males are characterized by increased aggression and persistence.

How long crayfish live in nature remains a mystery even to scientists. It is assumed that their lifespan is 10–25 years. No consensus has been reached. In aquarium conditions, arthropods can live up to 7 years, in rare cases slightly longer.

Sexual dimorphism in crayfish: how to distinguish males from females

People often get these exotic pets out of curiosity, without knowing much about them. The main thing to start with is learning how to tell the sex of your favorite creatures.

Inexperienced owners often place two individuals of the same sex in one container, but miracles do not happen—there will be no offspring.

Some believe that all crayfish are hermaphrodites, have no sex, and any crayfish can produce offspring on its own. This is a misconception; if you look closely, you can distinguish between “boys” and “girls.” The correct choice of sex and mature individuals is especially important when mating.

It is not so easy to determine the sex of arthropods. Sexual dimorphism is not very pronounced. It is worth figuring out how to distinguish between crustaceans:

• Female crayfish are smaller in size, but this is not the main indicator. Crayfish develop differently, which leads to similar sizes of individuals of different sexes.
• Female crayfish may not have a pair of front legs at all, or they may be poorly developed. Their abdomen is wider than their cephalothorax. Their claws are shorter and the tips are not as sharp.
• The female reproductive organs are located in front of the third pair of legs, counting from the last pair. All other limbs are used not only for movement, but also for carrying future offspring. During fertilization, females can be easily identified by the presence of eggs, which they hold with their legs.
• Males are distinguished by longer and thicker claws, and a slightly narrower abdomen. The limbs located near the abdomen are longer. Males have: the first pair of legs are gonopods, the second pair are for spermatophore delivery, and the genital openings and tubular formations are near the last (fifth) pair of legs.

Female crayfish are smaller in size.

The coloration of crustaceans may vary depending on their habitat. The color and chemical composition of the water also have an impact.

It is important for them to blend in with their surroundings and not stand out against the background of silt and various snags. Crayfish are usually brown, greenish-brown, or bluish in color.

How to choose a suitable pair

For successful reproduction, it is necessary to select individuals that have reached sexual maturity: females should be 3-6 years old and up to 12 cm long, with a body weight of up to 60 g, while males should be 2-4 years old and slightly larger than their partners.

In decorative species of crayfish, fertility mainly depends on the parameters of the female. The larger the female, the more eggs she can carry.

Readiness for mating is determined by the appearance of the individuals:

• In males, the seminal glands change color to milky white and become longer. The first legs under the abdomen change shape, as they are used during mating. They swell and turn white.
• The female also undergoes changes—her ovaries enlarge, which is a clear indicator of reproduction.

Another sign of excellent crayfish health is their activity. They should move their claws quickly.

Creating a favorable environment for crayfish reproduction

To ensure crayfish reproduction, you need to create favorable conditions in your home aquarium. If the arthropods feel comfortable in their new environment, they will be able to reproduce.

Crayfish reproduction diagram

What you need to provide for crayfish at home:

• Purchase a large aquarium with a tightly closing lid. It is important to remember that arthropods are excellent jumpers and can then spread throughout the room.
• Maintain the temperature in the aquarium at approximately +18…+20 degrees.
• Monitor water purity, as pets are sensitive to this.
• Place river sand or various pebbles on the bottom. They should be of different sizes to give the pets a choice.
• Provide high-quality and varied food and vitamin supplements.
• Prepare a separate container for the offspring. Parents eat their young and relatives in the aquarium and in nature.
• Crayfish spend most of their time in hiding. For this, they need tree stumps, large plastic pipes, grottos, colored pebbles, pots, and shards. Anything that is suitable for hiding adults and young will do. All individuals are particularly vulnerable during molting, so they always hide, even from their own kind. Larger crayfish can easily eat weaker and smaller individuals that have shed their chitinous shell.

Crayfish spend most of their lives at the bottom, so when choosing an aquarium, it is better to give preference to a wider one. Choose a habitat with a volume of at least 150 liters with a constant supply of oxygen.

The mating process of crayfish

The pre-spawning period for crayfish begins in autumn and ends with spawning in May. They move to shallow water, where it is much warmer.

It is interesting to see how river crayfish reproduce. Male crayfish are usually larger than females. The mating season is October-November or at the end of winter (February-March). It is important that the water temperature is +10 degrees Celsius.

Female crayfish always molt before breeding, which attracts the attention of their partners. Then you can observe their mating games. This is the courtship period, when males touch the female with special “antennas.”

Before breeding, the female crab molts.

Mating and fertilization will be successful when the male has reached a large size, is mature in age, and is strong. Mating lasts about 2–3 weeks, and fertilization is external. In one season, a male can fertilize up to three females. To reproduce well, you need physically strong, healthy individuals.

During mating, the male crayfish wraps his legs around the female and presses tightly against her inner side. The male transfers spermatophores to the female's abdomen. The female tries to break free from the powerful grip, which causes her to lose a lot of strength. She then hides in her burrow, crawling out only to search for food.

The male crayfish is full of energy and ready to fertilize 2-3 females. When he mates 2-3 more times, he also gets tired and hungry. He may eat the last female after mating.

To avoid such cases, you should control the number of pets, with 1:3 being the optimal ratio.

The male transfers spermatophores to the female's abdomen

Carrying crayfish eggs

The future mother should be placed in a separate container and provided with complete rest. If this is not done, all the young will be eaten by their relatives.

The number of eggs depends on the age and parameters of the female. The female lays from 20 to 200 eggs.

Watching crayfish give birth is an interesting activity. A fertilized female crayfish will lay eggs after about 20 days. They will stick to her ovipositor, located on her tail. The eggs will remain there until the crayfish larvae are born.

This is a time of severe trials for the female. She will have to chase the water, actively working with her tail, to regularly wash the eggs and saturate them with oxygen. If the female spends a lot of time in a burrow with stagnant water, the eggs may die.

The female crayfish lays eggs 20 days after mating.

In natural conditions, small insects such as beetles or scorpions can cause harm. In any case, some of the eggs will break off and be lost.

Where and how river crayfish eggs develop

The offspring will grow on the female's abdomen until the next molting. The crustaceans will grow unevenly, so it is better to choose a spacious aquarium.

The eggs under the female's tail will develop until the beginning of summer. In winter, the number of eggs will decrease due to loss or fungal infection. The total development period of crayfish embryos is approximately 50-60 days.

Spawning always occurs at night and lasts about 3 hours, with up to 200 eggs in a clutch. Mature eggs take on a brownish tint. The crustaceans hatch in warm spring weather, requiring a water temperature of +21…+24 degrees Celsius.

The eggs under the female's tail will develop until the beginning of summer.

The larvae, after hatching from the eggs, reach 9–11 mm in length. At first, they remain under their mother's tail for about 10 days. This provides reliable protection from predators. Then they begin their independent life.

Young crayfish

Grown crayfish can also eat their smaller brothers. Therefore, it is better to prepare containers in advance so that you can separate them in time.

Red cabomba; Plants

The third option for preserving offspring is to remove the breeders immediately after spawning. This option is simple, but requires the aquarist to be attentive and timely. The water must be changed as it becomes dirty. It is necessary to change 20% of the water once every 5-7 days. This is the optimal time interval to prevent water contamination.

In this regard, it is very important not to overfeed the fish, so as not to cause problems with their gastrointestinal tract. Feed the swordtails once a day and give them fasting days. This will be one of the keys to success in keeping them. It should be noted that when buying any dry food, you should pay attention to the date of manufacture and shelf life, try not to buy food by weight, and store food in a closed container—this will help prevent the growth of pathogenic flora. In a large species aquarium, you can keep a whole school of 3 or even 6 individuals.

The average temperature in the aquarium should range from 24 to 27 degrees Celsius.

A heavily pregnant swordtail female =) To protect the offspring, you can also use special funnel-shaped spawning boxes – the female stays in the funnel, and the spawned fry fall out of the funnel into the spawning aquarium. This ensures that there is no contact between the parent and the fry.

Crayfish are omnivorous, and young crayfish feed in the same way as adults. Any organic waste in the aquarium (as in open water bodies) will become food for the young. The basis of the crustaceans' diet in nature is carrion. In a confined space, there is not enough variety in food, and they may eat their fellow crayfish.

Young crustaceans feed in the same way as adults

Young crayfish need to be fed, suitable food includes:

• dry mix for fry;
• artemia (tiny crustaceans);
• finely chopped tubeworms;
• vitamin supplements are also essential.

In captivity, insect larvae, minced meat, boiled potatoes, snails, and grated carrots are added to the feed. In their natural environment, they feed on greens, small fish, and earthworms. The animals grab their prey with powerful claws, then tear off small pieces and send them to their mouths.

In captivity, crayfish can be fed minced meat

The following equipment is necessary to properly care for crustaceans in an aquarium:

• Filter. It is better to choose an internal filter for regular water cleaning. If there is a hose with an external cleaner, crayfish can easily escape.
• Compressor. It is important for oxygenating the aquarium water. An air supply is necessary to ensure the reproduction of crayfish.
• Thermometer with temperature control. To ensure a comfortable living and breeding environment, arthropods need a specific temperature regime. If the temperature is too high, oxygen will not dissolve well in the water.

Non-predatory fish, which typically inhabit the upper layers of the aquarium water, will coexist with the arthropods in the aquarium. This way, the pets will not interfere with each other.

In an aquarium, owners can often observe the male eating the female. This may be due to hunger or weakness of the individuals. You need to be attentive in order to remove the fertilized female and babies in time.

The first molting of the babies

After 10 days, the young crustaceans will undergo their first molt, which will make them look similar. By this time, their body weight will also increase to 21-30 g, and their length to 1.1-1.2 cm.

When the first molting is over, all the babies will leave their shelter. But they will swim only a short distance away. At the first sign of danger, they instantly return to their mother's belly, which is a refuge from any trouble.

Ten days after birth, the first molting of the crustaceans will occur.

In an aquarium, the young must be kept separate from the adults. It is impossible to determine the sex of the young, as their sexual organs develop much later.

Young crayfish molt once in the first year, up to four times in the second year, and then twice a year. At home, they will molt more often.

Breeding business

Recently, it has become fashionable to breed fish and crayfish. But the business idea of breeding crustaceans will require a lot of effort and time. After all, the animals must first be raised, then their eggs must be obtained and the fry must be raised. It will not be possible to quickly recoup all the material costs.

Breeding crayfish requires a lot of time and effort.

So, to sum up the above, we can recommend the following:

But don't confuse them with internal backpacks, such as Tetra EasyCrystal.

– For aquariums up to 100 liters – internal filters. In conclusion, it should be noted that there are other less common methods and mechanisms for filtering aquarium water, such as a filter located in the aquarium lid. Such filter locations are less popular and also have a number of advantages and disadvantages. In addition, you can make your own filter, for example, from a plastic canister and bottle. There are plenty of examples of DIY filters online and on YouTube.

This is the most typical backpack filter.

– For small aquariums up to 20 liters – hanging backpack filters.

– For large aquariums with a volume of over 150 liters, external aquarium filters are the best choice. This is a compromise between the aquarist's desire to install filtration and the physical impossibility of squeezing anything into a mini aquarium. Such filters are called “backpacks” or “waterfalls.” This filter is best suited for small aquariums, where any internal filter would be superfluous in a volume of 7-10 liters. They are attached to the outer wall of the aquarium, the intake tube is lowered into the aquarium, and the outlet creates a waterfall.

Understanding the main stages of their life cycle — from distinguishing males from females by the size of their claws and the shape of their abdomen to the appearance of larvae — is not only interesting but also useful. This knowledge helps to preserve natural populations and successfully breed crayfish at home or on farms.

The main thing to remember is that this process requires special conditions. A female with roe needs clean, oxygen-rich water, shelter, and peace. If you are lucky enough to observe such a “caring mother,” treat her with the utmost care, because the birth of a new generation of these amazing creatures depends on it.