Temperature-induced changes in reproductive variables in the teleost fish Lophiosilurus alexandri

The present study evaluates whether increased water temperature induces reproduction by Lophiosilurus alexandri under controlled conditions, and investigates the effects of this procedure on sexual steroids, hematological profile and behavior. A 44-week experiment was performed with four wild males and 12 wild females that had been acclimatized to captive conditions. Water temperature was maintained at 24.4 +/- 1.0 degrees C for weeks 1-22, and then at 29.0 +/- 1.1 degrees C for weeks 22-44. Spawn weight, number of eggs/spawn and hatching rate were satisfactory and ranged 27.5-127.5 g, 1209-5183 and 83-89%, respectively. Hematocrit, leukocytes and glucose were not influenced by increased water temperature, while higher values for erythrocytes were observed for both sexes. The lowest value for plasma protein was for females maintained at 29.0 degrees C, while the lowest value for testosterone was obtained at the end of the study period at a temperature in 29.0 degrees C. Serum values of 17 beta-estradiol were higher in females than in males, however, there was no evidence of variation as a function of experimental temperature or interaction with sex. The reproductive behavior of L. alexandri in captivity is described for the first time. The present study demonstrates that adult individuals are able to maintain a stable hematological profile during an increase in mean water temperature from 24.4 degrees C to 29.0 degrees C, even during the reproductive period, and still produce good quality larvae. Nonetheless, whether spawning was associated with increased 17 beta-estradiol levels could not be determined.