Biologia reprodutiva e alimentar de Trigonectes balzanii (Perugia, 1891) (Cyprinodontiformes: Rivulidae) em ambientes aquáticos temporários, Pantanal, Brasil.

Abstract

This study describes morphological, reproductive, and trophic aspects of Trigonectes balzanii, a rivulid widely distributed in temporary aquatic habitats of the Brazilian Pantanal. A total of 186 individuals collected from temporary environments were analyzed to characterize population, reproductive and feeding patterns. No significant differences in length and weight were observed between sexes, although only males were recorded in the largest size and weight classes. The overall sex ratio did not differ from 1:1, with a predominance of males in the larger size classes. Females showed a high frequency of reproductive activity throughout the year, with partial and continuous spawning. The length at first maturation (L₅₀) was estimated at 19.77 mm. Fecundity ranged from 54 to 77 oocytes, with no significant correlation with body length or weight. The oocyte diameter distribution indicated a pattern of partial spawning. The diet was composed predominantly of microcrustaceans, aquatic and terrestrial insects, and plant material, characterizing T. balzanii as a generalist insectivore and omnivore. An ontogenetic trophic shift was observed, with smaller individuals consuming mainly microcrustaceans and larger individuals showing a more diversified diet. No significant differences in diet composition were detected between males and females. The results contribute to the knowledge of T. balzanii biology and expand information on Rivulidae inhabiting temporary environments of the Pantanal.