Frequently asked questions about viviparous
What is viviparous?
Most fish lay eggs, but some species give birth to fry. There are two types of viviparous – viviparous and oviparous. The oviparous bear eggs inside, and the fry are born fully formed. They get their food from the deutoplasm. In the case of viviparous, nutrition is obtained directly from the mother. About 15 of the 480 known fish families exhibit some form of live birth. This includes half of all sharks and rays, as well as viviparous carpenters such as guppies, swordsmen, and mollinesians, as well as a number of unusual species.
How do viviparous mate?
Males of viviparous species, such as guppies, swordsmen, and mollinesias, possess a modified anal fin called gonopodium, which is used for internal fertilization of females. In females, gonopodium it is absent, instead of the usual triangular anal fin. On this basis, you can easily determine the sex. In some species, such as Phallichthys fairweatheri, the size of the gonopodium can reach 50% of the body length. Gonopodium may also be present in female guppies with elevated levels of male hormones. Such individuals are useless for breeding, and you should avoid adding such individuals to your aquarium.
Do I need to keep them in pairs?
Males of viviparous species can be overly active sexually, so it is better for females when there are at least two females for each male.
How long does pregnancy last?
The duration of pregnancy varies depending on the species, but the most common viviparous – carpozubye-produce from 20 to 200 fry every 4-6 weeks. Most viviparous species quickly reach sexual maturity. Male guppies are ready for procreation in two months, females – in three. Therefore, if you have a lot of females in the aquarium, the population can quickly grow unnecessarily. In the aquarium, fry continue to appear, although there are no males. How is that possible? A viviparous produce spermatophore – small clumps of sperm and fertilize their females. In some species, spermatozygotes can reside in the folds of the ovaries and uterus of females for up to a year, allowing females to fertilize multiple litters from a single mating. Therefore, when buying females, it is possible that they are already fertilized by males, so fry may appear in your aquarium. If you do not need fry – do not start females.
How to feed baby fish?
The fry of viviparous species are usually larger than the fry of other species, and are often able to eat the same as adults, unlike the fry of ordinary fish, which are first fed from the yolk SAC. Most newborn fry are good at eating liquid or powdered food for viviparous fish, as well as live or frozen Artemia nauplii. They grow quickly and after a couple of weeks they can be transferred to feeding adult food.
Do I need to use a cage?
Most experts agree that for viviparous species it is not necessary to use a cage, its use exposes females of the species to excessive stress. A sufficient number of fry can be grown in the General aquarium, provided that a large number of shrubby plants, such as kabomba, are placed in the aquarium, as well as in the absence of large fish capable of eating the fry. For large broods, a separate aquarium is required.
I’m told guppies are easy to keep. Why do my fish keep dying?
A couple of decades ago, guppies were considered disease-resistant and easy to maintain. Today, everything has changed quite a lot, and it has become quite difficult to keep guppies, as they are prone to various diseases and are sensitive to pollution. Some stores no longer sell guppies, and very few recommend guppies for novice fish breeders. It is likely that constant mating, the use of hormones and the misuse of antibiotics have led to genetic changes and health problems in many members of the species.
The fins of my guppies are constantly torn. What is the reason?
Males have guppy very long fins, and other fish, especially barbs and Tetra, you can take a bite out of these pieces. Therefore, before buying fish, you need to make sure that they are compatible. And while fin biting is common, torn fins in guppies can sometimes be a sign of a disease thought to be caused by a parasite called tetrachymena. Often the treatment is very complex, but antiparasitic treatment, especially involving the use of copper, can be effective. The addition of aquarium salt in the amount of 2-3 grams per litre can help reduce salt loss through the open wound. Good water quality is vital.