Abstract
The reproductive biology of a population of the weakly electric fish Brachyhypopomus draco from southern Brazil is described. Information is provided on the establishment of the reproductive period in this species and its relations with environmental and feeding factors, as well as on the absolute and relative fecundities, spawning type, sex ratio and sexual dimorphism. The species exhibits a relatively long reproductive period, a relative fecundity of 0.173 oocytes per mg of female total weight, and fractional spawning. The sex ratio did not differ from 1:1 during all sampled months. Sexual dimorphism related to hypertrophy of the male's distal portion of caudal filament was observed and males grew to greater lengths than females. Male gonadosomatic index (GSI) was significantly related to water depth, oxygen saturation and temperature. Female GSI was significantly related to water depth and hepatosomatic index.
Highlights
The order Gymnotiformes is restricted to Neotropical freshwaters, occurring from southern Mexico to Argentina, and to the Caribbean island of Trinidad (Mago-Leccia, 1978; Crampton & Albert, 2006)
In southern Brazil, studies on the reproductive biology of gymnotiform species have been undertaken by Cognato & Fialho (2006) on Gymnotus aff. carapo, by Giora & Fialho (2009) concerning Eigenmannia trilineata, and by Giora (2008)
The aim of this study was to characterize the reproductive biology of a population of Brachyhypopomus draco, recently described by Giora et al (2008), from southern Brazil by determining the reproductive period and its relations with environmental and feeding factors, and to determine the absolute and relative fecundities, spawning type, sex ratio and sexual dimorphism of the species
Summary
The order Gymnotiformes is restricted to Neotropical freshwaters, occurring from southern Mexico to Argentina, and to the Caribbean island of Trinidad (Mago-Leccia, 1978; Crampton & Albert, 2006). Representatives of this order can be found in several aquatic habitats, including river channels, floodplains, flooded forests, forest streams, waterfalls, swamps, coastal creeks and estuarine reaches (Crampton & Albert, 2006). In southern Brazil, studies on the reproductive biology of gymnotiform species have been undertaken by Cognato & Fialho (2006) on Gymnotus aff. In southern Brazil, studies on the reproductive biology of gymnotiform species have been undertaken by Cognato & Fialho (2006) on Gymnotus aff. carapo, by Giora & Fialho (2009) concerning Eigenmannia trilineata, and by Giora (2008)
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