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Superfetation (also spelled superfoetation – see fetus) is the simultaneous occurrence of more than one stage of developing offspring in the same animal. [1] [2] [3]In mammals, it manifests as the formation of an embryo from a subsequent menstrual cycle, while another embryo or fetus is already present in the uterus.
In 1982, twins who were born with two different skin colors were discovered to be conceived as a result of heteropaternal superfecundation. [7] [5] In 1995, a young woman gave birth to diamniotic monochorionic twins, who were originally assumed to be monozygotic twins until a paternity suit led to a DNA test. This led to the discovery that the ...
A pregnant Southern platyfish. Pregnancy has been traditionally defined as the period of time eggs are incubated in the body after the egg-sperm union. [1] Although the term often refers to placental mammals, it has also been used in the titles of many international, peer-reviewed, scientific articles on fish.
Females can produce eggs faster than males can brood them, and are limited by the size of the male's brood pouch, which cannot carry all the eggs of a female similar to himself in size. [ 9 ] [ 10 ] Male brood time is approximately four to six weeks, during which time the male provides oxygen and nutrients to the developing embryos until they ...
Seahorses are renowned for mating for life, with the male carrying the eggs. But after following three male pygmies and one female for weeks, Smith discovered that the sex lives of the smaller ...
In the Star Trek: Enterprise episode "Unexpected", Trip Tucker becomes pregnant with the offspring of a female of another species, described late in the chapter, set in mid-22nd century, as being "the first recorded instance of a human male pregnancy". In the video game The Sims 2 male characters can be impregnated via cheat codes or alien ...
The male seahorse is equipped with a brood pouch on the ventral, or front-facing, side of the tail. When mating, the female seahorse deposits up to 1,500 eggs in the male's pouch. The male carries the eggs for 9 to 45 days until the seahorses emerge fully developed, but very small. The young are then released into the water, and the male often ...
Pregnant male pipefish can absorb nutrients from their broods, in a manner very similar to filial cannibalism found in many other families of fish. The smallest eggs in a brood of various egg sizes usually have lower survival rates than larger ones due to the larger eggs having a longer-lasting food source (absent contributions from the father ...