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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.
In ovoviviparous fish the eggs develop inside the mother's body after internal fertilisation but receive little or no nourishment directly from the mother, depending instead on a food reserve inside the egg, the yolk. [10] Each embryo develops in its own egg. Familiar examples of ovoviviparous fish include guppies, angel sharks, and coelacanths.
The fish reaches a size of up to 10 cm (4 in). It is found among plants over sandy and muddy bottoms in shallow waters. It feeds mainly on plants, and to a lesser extent, upon worms, crustaceans, and insect larvae. [2] This species of fish was once used for human pregnancy tests. Female specimens were injected with the urine of the woman to be ...
Human pregnancy can be divided into three trimesters, each approximately three months long: the first, second, and third trimester. The first trimester is from the last menstrual period through the 13th week, the second trimester is 14th–28/29th week, and the third trimester is 29/30th–42nd week. [ 6 ]
Mosquitofish introduction outside of their native range can also be harmful to ecosystems. [25] [26] Mosquitofish can consume or injure other small fish or otherwise harm them through competition. [19] The ecological impacts of mosquitofish are partly dictated by their sex ratio, which can vary dramatically across their introduced range. [27]
Another factor is due to the shortage of food stocks during winter as the insects are being driven away and as the result, bat hibernate in pregnant condition. [24] In pinnipeds, the purpose of delayed implantation is in order to increase survival chance of the young animals as the mother ensure that the neonates are born at an optimal season. [25]
External fertilization is a mode of reproduction in which a male organism's sperm fertilizes a female organism's egg outside of the female's body. [1] It is contrasted with internal fertilization, in which sperm are introduced via insemination and then combine with an egg inside the body of a female organism.
Radakov estimated herring schools in the North Atlantic can occupy up to 4.8 cubic kilometres with fish densities between 0.5 and 1.0 fish/cubic metre, equivalent to several million fish in one school. [8] Herring are amongst the most spectacular schoolers ("obligate schoolers" under older terminology).