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At least one group of fish has been named after its pregnancy characteristics. The surfperch, genus Embiotoca, is a saltwater fish with a gestation period of three to six months. [13] This lengthy period of pregnancy gives the family its scientific name from the Greek "embios" meaning "persistent" and "tokos" meaning "birth".
Examples include the oviparous sharks, such as the horn shark, and oviparous rays, such as skates. In these cases, the male is equipped with a pair of modified pelvic fins known as claspers. Marine fish can produce high numbers of eggs which are often released into the open water column. The eggs have an average diameter of 1 millimetre (0.039 in).
Male pregnancy is a common feature in the family Syngnathidae, which includes pipefish, seahorses, and sea dragons. [12] This type of polyandry has been demonstrated by analyzing the genetic composition of Gulf pipefish , Sygnathus scovelli and straightnose pipefish , Nerophis ophidion , which shows that males only mate once during their ...
The fish family Syngnathidae has the unique characteristic of a highly derived form of male brood care referred to as "male pregnancy". [2] The family is highly diverse, containing around 300 different species of fish.
Ovoviviparous fish give birth to live young. Unlike viviparous species, their embryos are nourished by an egg yolk, and not directly by the parent.. See also:Category:Viviparous fish - fish which give birth to live young which receive nourishment whilst in the womb.
Coelacanth eggs are large, with only a thin layer of membrane to protect them. Embryos hatch within the female and eventually are born alive, which is a rarity in fish. This was only discovered when the American Museum of Natural History dissected its first coelacanth specimen in 1975 and found it pregnant with five embryos. [67]
Livebearers are fish that retain their eggs inside the body and give birth to live, free-swimming young. They are especially prized by aquarium owners. They are especially prized by aquarium owners. Among aquarium fish, livebearers are nearly all members of the family Poeciliidae and include: guppies , mollies , platies and swordtails .
For example, male testes of spawning fish are smooth and white and account for up to 12% of the mass of the fish, while female ovaries are granular and orange or yellow, accounting for up to 70% of the fish's mass. Male lampreys, hagfish and salmon discharge their sperm into the body cavity where it is expelled through pores in the abdomen.