Reproductive biology of freshwater fishes from the Venezuelan floodplains |
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Authors: | H Y Guerrero E Cardillo G Poleo D Marcano |
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Institution: | (1) Laboratorio de Neuroendocrinología Comparada, Instituto de Medicina Experimental, and Escuela de Medicina J.M. Vargas, Universidad Central de Venezuela, Apartado 47633, Caracas, 1041, Venezuela;(2) Estación de Piscicultura, Decanato de Agronomía, Universidad Centro Occidental Lisandro Alvarado, Barquisimeto, Venezuela |
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Abstract: | This review describes the endocrine changes that occur during the annual reproductive cycle of Pygocentrus cariba, Pimelodus blochii, and Oxydoras sifontesi and their relationships with the environmental characteristics of Venezuelan floodplains. Most reproductive studies of teleosts
have focused on changes that occur during annual cycles in temperate species but, in tropical fish, this has been examined
less frequently. P. cariba, P. blochii, and O. sifontesi are seasonal breeders widely distributed along the Orinoco River. Under natural conditions they have an annual gonadal cycle
closely related to changes in the annual hydrology cycle of the Orinoco River which defines two seasons on the floodplain:
inundation and isolation. The reproductive cycle of these species seems to be controlled by cues from the external environment.
Relevant data about gonadal maturation, for example gonadosomatic index and sexual hormones secretion, are contrasted. The
role of catecholamines in neuroendocrine control of the reproductive axis is also considered in this work. |
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Keywords: | Catecholamine Estradiol Gonadal development GnRH Hypothalamus Pituitary Sex hormones Teleost Testosterone |
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