In some bony fishes the eggs simply develop within the female, the young emerging when the eggs hatch (ovoviviparous). Many skates and rays also bear live young. Members of about a dozen families each of bony fishes (teleosts) and sharks bear live young. In some fishes the eggs are fertilized internally but shed before development takes place. In the females the eggs are formed in two ovaries (sometimes only one) and pass from the ovaries to the urogenital opening and to the outside. Sometimes accessory organs are used to fertilize females internally-for example, the claspers of many sharks and rays. Sometimes the pelvic fins are modified to help transmit the milt to the eggs at the female's vent or on the substrate where the female has placed them. In sharks and rays and in cyclostomes the duct leads to a cloaca. In bony fishes a sperm duct leads from each testis to a urogenital opening behind the vent or anus. Males produce sperm, usually as a milky white substance called milt, in two (sometimes one) testes within the body cavity. The mortality of the young and especially of the eggs is very high, and often only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid. Many shore and freshwater fishes lay eggs on the bottom or among plants. The eggs of pelagic fishes usually remain suspended in the open water. The methods of reproduction in fishes are varied, but most fishes lay a large number of small eggs, fertilized and scattered outside of the body. Although the term reproduction encompasses a great variety of means by which organisms produce new offspring, reproductive processes can be classified into two main types: Sexual reproduction and asexual reproduction. Reproduction is a fundamental feature of all known life each individual organism exists as the result of reproduction. In biology, reproduction is the process by which new individual organisms are produced. Smit Ramesh Lende 1 ,Ramchandra khileri 2ĭepartment of Fisheries Resource Manegment
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