Reproductive cycle of Branchiura sowerbyi (Oligochaeta: Naididae: Tubificinae) cultivated under laboratory conditions

The biology of Branchiura sowerbyi Beddard, 1892 has been the focus of many studies in temperate regions, where the species is exotic, according to literature data. Due to its high productivity and easy cultivation, B. sowerbyi is of great interest as a food source for fish farming. The present study reports information on the reproductive biology and growth of B. sowerbyi under laboratory conditions at 25 +/- 1 degrees C. Weekly observations during 52 weeks indicated that the time between cocoon laying and young hatching was 14 to 16 days, the specific daily growth rate was 0.91 +/- 0.04% (mean +/- SD) and the time to reach sexual maturity was 40.83 +/- 6.88 days. As reported by other authors, the hatching rate observed was low (33.08%), but the survival rate of young was high, approximately 96%. Laboratory observations showed that B. sowerbyi has two annual reproductive cycles, the first (between the 5(th) and 24(th) week) being more pronounced than the second (between the 31(st) and 51(st) week) concerning the number of cocoons.