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Five modes of reproduction can be differentiated in fish based on relations between the zygote(s) and parents: [6] [7] Ovuliparity : Fertilization of eggs is external; zygotes develop externally. Oviparity : Fertilization of eggs is internal; zygotes develop externally as eggs with large vitellus .
Fish reproduction. A pair of bettas spawning under a bubble nest. Fish reproductive organs include testes and ovaries. In most species, gonads are paired organs of similar size, which can be partially or totally fused. [ 1 ] There may also be a range of secondary organs that increase reproductive fitness.
Fish embryos go through a process called mid-blastula transition which is observed around the tenth cell division in some fish species. Once zygotic gene transcription starts, slow cell division begins and cell movements are observable. [4] During this time three cell populations become distinguished. The first population is the yolk syncytial ...
The development of a zygote into an adult is a complex and delicate process of interactions between genes and the environment that must be carried out precisely, and if there is any alteration in the usual process, caused by the absence of a necessary gene or the presence of a different one, it can arrest the normal development causing the non ...
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete (haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). [1]
This type of reproduction had been seen before in bony fish, but not in cartilaginous fish such as sharks. [71] In the same year, a female Atlantic blacktip shark in Virginia reproduced via parthenogenesis. [72] On 10 October 2008, scientists confirmed the second case of a "virgin birth" in a shark.
In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell, (spermatozoon). [1] Once fertilized, the ovum becomes a single diploid cell known as a zygote.
Cleavage (embryo) In embryology, cleavage is the division of cells in the early development of the embryo, following fertilization. [1] The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called ...