992 resultados para Reproductive mode


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The influence of the 1992-1993 El Nino events on the reproductive behavior of the Scomber japonicus peruanus (Chub mackerel) was studied from samples collected monthly, along the Peruvian coast (3 degrees 23`S-14 degrees 00`S), from January 1990 to December 1993. The monthly variation of the gonadosomatic index and the frequency of the periods of gonad maturation evidenced that the spawning of the species occurred all year long, being more intense in summer. The values of the gonadosomatic index were higher during the occurrence of the 1992-1993 El Nino, while the body weight and gonad weight decreased. Regarding the condition factor, its values decreased in females over 35 cm in fork length.

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This paper characterizes the developmental stages of the testes and vasa deferentia of the Panulirus echinatus Smith, 1869 through comparisons between microscopic findings, macroscopic aspects, and gonadosomatic index (GSR). The lobsters were sampled monthly (November 1999 to October 2000) using seine nets and a total of 1716 males were obtained at Tamandare Bay. Each carapace was cut to allow evaluation of the reproductive organs; the testes and vasa deferentia were dissected, weighed, fixed in Bouin`s solution up to 12 hours and submitted for histological analysis to determine the presence and/or absence of spermatozoa. These measures, along with change in color, size, diameter, development of the spermatophores and the GSR allowed the caracterization of three development stages: immature, intermediate and ripe. In conclusion, the maturity of the testes precedes the maturity of the vasa deferentia. To evaluate if gonadosomatic relation was a good quantitative indicator of the maturity stage, t tests (alpha = 0,05) were used and verified significant difference in the averages of GSR. The statistics corroborated that GSR can be used as indicative of the developmental stages for P. echinatus.

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A study in the comparative physiology of the infecundity of the adolescent organism.

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Mode of access: Internet.

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Mode of access: Internet.

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Thesis (Ph. D.) - Cornell University, 1921.

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Mode of access: Internet.

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Vol. for 1995 in 3 pts.: v. 1 Eastern United States ; v. 2 Central United States ; v. 3 Western United States.