Efeito do contato macho-fêmea na preferência da fêmea e na competição entre machos na tilápia-do-Nilo
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Data
2008-07-03
Autores
Castro, André Luis da Silva [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O comportamento reprodutivo dos teleósteos envolve a seleção de parceiros para acasalamento por meio de escolha da fêmea e da disputa entre machos. A disputa pode levar à formação de hierarquia de dominância, na qual os machos dominantes têm vantagem no acasalamento por impedir que outros machos se aproximem da fêmea. Por outro lado, é possível que a fêmea prefira machos com maior habilidade competitiva, antes da formação da hierarquia. Assim, para compreender os fatores que afetam a preferência da fêmea e se a presença da fêmea durante as competições fornece vantagem na luta dos machos, realizamos dois estudos com a tilápia-do-Nilo (Oreochromis niloticus). O primeiro estudo testou a preferência das fêmeas em relação à características indicadoras da habilidade competitiva dos machos, sem a interferência da competição entre eles. Para isso, uma fêmea foi submetida ao contato visual com dois machos isolados e a preferência por um deles foi testada. Posteriormente os mesmos machos interagiram e estabeleceram a dominância. O macho preferido não se tornou dominante. Assim, não houve associação entre a preferência da fêmea e características indicadoras da habilidade competitiva dos machos. No segundo estudo testamos o efeito do contato visual de um macho com uma fêmea sobre a disputa hierárquica entre machos, uma vez que as interações macho-fêmea podem modular a reprodução e agressão dos peixes. Para isso, um macho em contato visual prévio com uma fêmea interagiu com um macho previamente isolado até o estabelecimento hierárquico. Porém, o macho em contato visual com a fêmea não se tornou dominante nem emitiu maior freqüência de ataques ao oponente. A presença da fêmea causou aumento do Índice Gonadossomático do...
Reproductive behavior of many fish species is performed by sexual selection and mate choice based on male-male contests. In such situation, selection is related to individual male competitive ability. Competition causes a social hierarchy, and dominant fish takes advantages for mating by avoid subordinate approach of females. Thus, it is possible that female prefer highest competitive ability males. To understand factors affecting female preference and, whether female presence can affect reproductive male ability, we performed two studies with Nile tilapia (Oreochromis niloticus) to understand the factors involved in dominance and female choice. In the first study we tested the female preference for highest competitive ability male. For this purpose, a female was kept in a visual contact with two males and the preference was tested by recording time female spent near to them. After that, both males were put together to fight, and we analyzed the chosen male was the winner. There was no association between female choice and male competitive ability. In the second study, we tested the effect of male visual contact with female and we supposed this could guarantee victories in a contest. Thus, a male was kept seeing a female during 6 days, and after that it was paired with a 6-days isolated male until hierarchical settlement. Female presence causes gonadosomatic index rise, but did not enhance chances for male victory in the social contest. This means that males that have more developed gonads do not take advantage in social interactions. Finally, we concluded that: i) females showed preference for one male; ii) female preference is not associated to male competitive ability; iii) visual stimulated males by female (with better gonadal condition) have not advantage in the hierarchy settlement.
Reproductive behavior of many fish species is performed by sexual selection and mate choice based on male-male contests. In such situation, selection is related to individual male competitive ability. Competition causes a social hierarchy, and dominant fish takes advantages for mating by avoid subordinate approach of females. Thus, it is possible that female prefer highest competitive ability males. To understand factors affecting female preference and, whether female presence can affect reproductive male ability, we performed two studies with Nile tilapia (Oreochromis niloticus) to understand the factors involved in dominance and female choice. In the first study we tested the female preference for highest competitive ability male. For this purpose, a female was kept in a visual contact with two males and the preference was tested by recording time female spent near to them. After that, both males were put together to fight, and we analyzed the chosen male was the winner. There was no association between female choice and male competitive ability. In the second study, we tested the effect of male visual contact with female and we supposed this could guarantee victories in a contest. Thus, a male was kept seeing a female during 6 days, and after that it was paired with a 6-days isolated male until hierarchical settlement. Female presence causes gonadosomatic index rise, but did not enhance chances for male victory in the social contest. This means that males that have more developed gonads do not take advantage in social interactions. Finally, we concluded that: i) females showed preference for one male; ii) female preference is not associated to male competitive ability; iii) visual stimulated males by female (with better gonadal condition) have not advantage in the hierarchy settlement.
Descrição
Palavras-chave
Peixe - Reprodução, Seleção sexual em animais, Competição (Biologia), Preferência sexual - peixes, Hierarquia de dominância - peixes, Competitive ability, Sexual selection, Reproduction
Como citar
CASTRO, André Luis da Silva. Efeito do contato macho-fêmea na preferência da fêmea e na competição entre machos na tilápia-do-Nilo. 2008. viii, 61 f. Tese (doutorado) - Universidade Estadual Paulista, Centro de Aqüicultura, 2008.