Reproductive biology and development of sexually dimorphic structures in Aphyocharax anisitsi (Ostariophysi: Characidae)

Abstract

The reproductive period of Aphyocharax anisitsi is described through the analysis of specimens collected monthly from April 2001 to March 2002 in the arroio do Salso (3022'27"S, 5502'06"W), Rosário do Sul, Rio Grande do Sul, Brazil. The monthly variation of the Gonadosomatic Index mean (GSI) of both males and females allowed the recognition of a defined seasonal reproductive period occurring between September and February, showing a positive correlation with temperature and day-length. Absolute fecundity was 344.8 oocytes and relative fecundity 0.68 oocytes per mg of body weight. Absolute fecundity was correlated with standard length and total body weight. It was possible to identify two categories of males through the analysis of the number of rays bearing hooks on the anal fin: those with few or no rays bearing hooks identified as young males hatched in the last reproductive season, and those with a higher number of anal-fin rays bearing hooks identified as males that had already reproduced once or that are maturing and participating in their first reproductive period. Once developed, anal-fin rays are maintained permanently. A positive correlation was found between the GSI of maturing and mature males and the number of anal-fin rays bearing hooks from August to January. All specimens bearing gill glands were mature or undergoing maturation, and the frequency of occurrence of the gill glands increased with a rise of GSI.