Fish pregnancy

Fish pregnancy is gestation in which developing embryos remain inside a parent’s body before live birth. It occurs through several reproductive strategies, with embryos nourished by yolk, maternal tissues, or both.

Connect

Viviparity: Reproduction in which embryos develop within a parent and offspring are born alive. Fish pregnancy is one form of viviparity, though the embryos’ sources of nourishment vary.
Internal fertilization: Fertilization in which sperm and egg unite inside the female reproductive tract. Internal fertilization commonly precedes fish gestation, but does not by itself mean embryos are retained.
Guppy: A small live-bearing freshwater fish native to northeastern South America and widely kept in aquariums. Guppies are a familiar example of fish that retain developing young and give birth to free-swimming fry.
Mammalian pregnancy: Gestation in mammals, typically involving prolonged development inside the uterus and maternal nourishment. Fish pregnancy can resemble mammalian gestation, but many fish embryos rely chiefly on yolk.
Lecithotrophy: Embryonic nutrition supplied primarily by yolk deposited in an egg before development. Many pregnant fish retain yolk-rich eggs without supplying substantial nutrients during gestation.
Oviparity: Reproduction in which animals lay eggs that develop outside the parent’s body. Egg-laying is the main contrast with fish pregnancy, where embryos remain inside until birth.
Mosquitofish: A small live-bearing fish genus, Gambusia, native to the Americas and introduced widely for mosquito control. Mosquitofish provide a well-studied example of internal gestation without a mammal-like placenta.
Marsupial reproduction: Reproduction in which young are born at an early stage and commonly continue development in a pouch. Marsupials show that live birth need not involve the long internal development seen in many pregnant fish.
Matrotrophy: Embryonic nutrition supplied by a parent during development, beyond the resources stored in the egg. Some pregnant fish transfer additional nutrients to embryos while they develop.
Ovoviviparity: A traditional term for live birth from eggs retained inside the parent and nourished mainly by yolk. This label has often been applied to yolk-dependent pregnant fish, though biologists increasingly prefer precise nutritional terms.