ABSTRACT. Tadpoles of Scillax rizibilis (Bokermann) (Anura, HyJidae): evalua· ting the paternal effects. A controlled experiment, related with the mating system of Scill.ax rizibilis (Bokermann, 1964), was conducted to assess if larval variation could be due to size of male or its ability to manage an amplexus. Adult indi viduals were caught during breeding activity (from February 1993 to January 1994), in a temporary pond in the municipality of Ribeirao Branco. Sao Paulo State, southeastern Brazil. The duration of the larval period was not different between tadpoles of large and small males, nor was it different between tadpoles coming from natural or artificial pairs. The reproductive status of the male (if it had managed an amplexus) also did not influence the total length nor the mass of the tadpoles close to metamorphosis. However. tadpoles of larger and heavier males were. on average, approximately 5.5% and II % larger and heavier. respectively, than tadpoles of smaller males. These results indicate that the breeding system of S. rizibilis could potentially have a directional effect on the larval characteristics. KEY WORDS. Scillax rizibilis, mating system, larval characteristicOs processos e as conseqiiencias decorrentes dos sistemas de acasalamento tern proporcionado diversos estudos tanto empfricos como te6ricos (WlLCZYNISKI & RY AN 1992; WAGNER 1998). A manutenyao, pela seleyao natural , de preferencias reprodutivas pelas femeas e raramentequestionada paraespecies nas quais os machos de anuros fornecem recursos ou realizam cuidado parental (veja exemplos em HOWARD 1978;KLUGE 1981). Por outro lado, quando os machos nao fornecem nem recursos nem cuidado parental, a manutenyao de preferencias reprodutivas e mais controversa (WOODWARD 1987;HOWARD et aL. 1994). Todavia, estudos recentes, com especies que apresentam estas caracterfsticas reprodutivas, tern demonstrado que a escolha realizada pela femea e adaptativa (BOURNE 1993;BASTOS & HADDAD 1996).Os anuros sao exce lentes objetos de estudo dos efeitos evolutivos do sistema de acasalamento, pois e possfvel identificar diversas caracterfsticas que afetam a performance de girinos, tais como crescimento larval mais nipido (TRAVIS 1983) e perfodo larval menor (TRAV IS & TREXLER 1986). A comparayao entre as caracterfsticas dos girinos poderia permitir avaliar se as dimensoes do macho (massa ou comprimento rostro-anal) ou a sua capacidade de conseguir amplexo sao relacionadas com a performance larval, de maneira que se possa verificar se ha alguma vantagem para a descendencia.