Livebearing fish are some of the most popular tropical aquarium fish of all time and include
Fish. Live birth is also rare in fish, accounting for about two percent of known species, including guppies and sharks.
Fish reproduction methods vary, but most types of fish lay eggs. The female fish lays unfertilized eggs in water nests or builds a safe area for them, then the male fertilizes these eggs; that is, the eggs are fertilized and mature outside the mother's body.
Some aquarium fish carry the eggs inside of them. When the eggs are fertilized, they eventually hatch inside the mother, and the babies emerge in a live birth. Other types of fish lay hundreds of eggs in nests within the aquarium, in this case, the males fertilize these eggs, and then they hatch into live fish.
Goldfish are never actually pregnant, as they spawn instead of give birth. They do carry eggs which take 2-7 days to hatch after being deposited and fertilized.
Aquarists commonly refer to ovoviviparous and viviparous fish as "livebearers". Examples include guppies, mollies, moonfish, platys, four-eyed fish and swordtails. All of these varieties exhibit signs of their pregnancy before the live fry are born.
"The reproductive behaviour of fishes is remarkably diversified: they may be oviparous (lay eggs), ovoviviparous (retain the eggs in the body until they hatch), or viviparous (have a direct tissue connection with the developing embryos and give birth to live young).
Aquarium fishes
Important group of egg-layers are barbs, rasboras, goldfish, tetras, danios, betas, angelfish and gouramis.
Guppies rapidly reach maturity. Since guppies give live birth instead of laying eggs, guppy fry (baby fish) are born more developed that most fish.
Fish pregnancies usually last between 3 weeks and 10 months. This huge range is due to the differences between various fish species. Aquarium fish like goldfish or guppies are at the lower end of the spectrum. On the other end, the basking shark and frilled shark have gestation periods of 3 and 3.5 years, respectively.
Ideally, pregnant females should be placed on their own in a separate aquarium with lots of feathery plants where they can give birth in a stress-free environment.
Pregnant female fish often develop a "gravid spot" on the abdomen near the rear vent. This is typically black or bright red, and grows more pronounced over the course of the pregnancy. Some fish always have this spot, but it will typically grow brighter or darker during once the fish is pregnant.
The Australian three-toed skink (Saiphos equalis) is doubly remarkable: Not only can it both lay eggs and bear live young, but it can do both within a single litter of offspring.
Only two mammals lay eggs: the platypus and the echidna. All other mammals give birth to live babies. Of all the birds that lay eggs, hummingbirds lay the smallest eggs, and ostriches lay the biggest eggs.
Many sharks are viviparous, meaning they give birth to live young. Like all sharks, species such as blue, bull, and hammerhead sharks rely at first on a yolk sac for nutrition. But they also develop a placental connection similar to a mammal's umbilical cord.
Livebearing fish are some of the most popular tropical aquarium fish of all time and include guppies, platies, mollies and swordtails. They are so-called because the females give birth to live young, instead of laying eggs like other freshwater fish species.
It is possible to raise baby fish in your main tank, but generally, few will survive this. Larger fish will see them as tasty snacks and even vegetarian fish may be tempted. They can also suffer injuries from being chased and bullied.
But in a nutshell, in some species, the male fish inseminates the female fish who then grows the fry inside her body, other fish lay eggs, which are then fertilized by the male outside of the female's body, and there are a few hermaphrodites self-fertilize, without the need for mating at all.
Crocodilians are either hole nesters or mound nesters. That is, they either excavate a hole, usually in sand, and bury their eggs, or they construct a mound, usually out of vegetation, and deposit their eggs in the centre of it.
There are over 500 species of shark living in waters around the world and the majority give birth to live young. The remainder are oviparous, meaning they lay eggs.
You can determine the sex of your fish by inspecting its gonads (reproductive organs), which are located towards the top of the gut cavity. Mature female fish will have orange ovaries and male fish will have white testes (see photos above).
New discoveries amaze us each day. And this exactly what has happened yet again. Two female ray fish have given birth to pups without a male ray fish being present in their ranks. The news has created quite a stir in scientific community and beyond.
Seahorses and their close relatives, sea dragons, are the only species in which the male gets pregnant and gives birth. Male seahorses and sea dragons get pregnant and bear young—a unique adaptation in the animal kingdom. Seahorses are members of the pipefish family.
Some would try to make you believe that a pregnant goldfish is called a twit, or a twerp. In reality there is no term for a pregnant goldfish because goldfish never get pregnant! Female Goldfish lay eggs and the eggs are fertilised by male fish outside of the body.