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Most male fish have two testes of similar size. In the case of sharks, the testes on the right side is usually larger [citation needed].The primitive jawless fish have only a single testis, located in the midline of the body, although even this forms from the fusion of paired structures in the embryo.
Fingerling – refers to a fish that has reached the stage where the fins can be extended and protective scales have covered the body. [4] At this stage, the fish is typically about the size of a human finger, [5] hence the name. Once reaching this stage, the fish can be considered a juvenile, and is usually active enough to move around a large ...
One eye can look forward while the other looks backward at the same time. The baby flounders have one eye on each side of their bodies like ordinary fish, and swim like other fishes do, but later on, as they undergo maturation to adulthood, the right eye moves to the left side, and flounders start to swim sideways, which gives them the ability ...
In birds and mammals altricial species are those whose newly hatched or born young are relatively immobile, lack hair or down, are not able to obtain food on their own, and must be cared for by adults; closed eyes are common, though not ubiquitous. Altricial young are born helpless and require care for a length of time.
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". The table below shows the gestation period and number of young born for some selected fish.
In some families, the eyes are usually on the right side of the body (dextral or right-eyed flatfish), and in others, they are usually on the left (sinistral or left-eyed flatfish). The primitive spiny turbots include equal numbers of right- and left-sided individuals, and are generally less asymmetrical than the other families. [ 1 ]
This process continues, so that each generation is half (or hemi-) clonal on the mother's side and has half new genetic material from the father's side. [62] [66] This form of reproduction is seen in some live-bearing fish of the genus Poeciliopsis [64] [67] as well as in some of the Pelophylax spp. ("green frogs" or "waterfrogs"):
Fish born in different regions will show clear differences here. Studies of the commercial fishing industry in the United States show that the population of bluefin tuna in the North Atlantic is made up of fish hailing from both coasts. While the fish may live in close proximity out in the Atlantic, they return to their natal region to spawn.