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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, e.g. [2][3][4][5] Consistent with this definition, there are ...
The eggs have an average diameter of 1 millimetre (0.039 in). The eggs are generally surrounded by the extraembryonic membranes but do not develop a shell, hard or soft, around these membranes. Some fish have thick, leathery coats, especially if they must withstand physical force or desiccation. These type of eggs can also be very small and ...
Common goldfish in a pond Common goldfish in aquarium. It is a common practice to keep common goldfish in a small bowl, but this allows waste in the water to build up to toxic levels and does not provide enough oxygen. For each small/young goldfish, there should be a minimum of 10 US liquid gallons (38 liters; 8.3 imperial gallons) of water. [3]
Guppy. The guppy (Poecilia reticulata), also known as millionfish or the rainbow fish, [3] is one of the world's most widely distributed tropical fish and one of the most popular freshwater aquarium fish species. It is a member of the family Poeciliidae and, like almost all American members of the family, is live-bearing. [4]
The comet-tailed goldfish breed was developed in the United States from the common goldfish by Hugo Mulertt, a government worker, in the 1880s. The comet goldfish was first seen in the ponds of the U.S. Government Fish Commission in Washington, D.C. [1] [2] Mulertt later became a propagator of goldfish and an author of books on goldfish.
Ranchu. The Ranchū (蘭鋳, 蘭虫, 卵虫, "Dutch worm") (also Maruko) [1] is a hooded variety of goldfish native to Japan, which lacks a dorsal fin. [2] It is referred to as the "king of goldfish" by the Japanese. [3] Maruko more commonly refers to the egg-fish goldfish. [4]
The black spots are the developing eyes. Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, to spawn refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is known as spawning. The vast majority of aquatic and amphibious animals reproduce ...
The egg is not retained in the body for most of the period of development of the embryo within the egg, which is the main distinction between oviparity and ovoviviparity. [1] Oviparity occurs in all birds, most reptiles, some fishes, and most arthropods. Among mammals, monotremes (four species of echidna, and the platypus) are uniquely oviparous.