Male sterility thresholds,in a tropical cosmopolitan drosophilid, Zaprionus indianus

When grown and kept at extreme constant temperatures, Zaprionus indianus males are sterile and do not produce viable sperm. This, phenomenon, already investigated in two Drosophila species, might be a general feature in drosophilids. On the high temperature side, sterility thresholds were similar in Z. indianus and D. melanogaster. On the low temperature side, Z. indianus was much more sensitive to cold. This might explain why Z indianus is restricted to tropical and subtropical climates, while D. melanogaster also proliferates in temperate places. After returning to a middle, permissive temperature, males recovered fertility. The time to recover was always longer than in D. melanogaster, and the number of progeny much smaller in all cases. Such differences may be due to anatomical and functional divergences, and specially the longer sperm length in Z indianus. (C) 2003 Elsevier Ltd. All rights reserved.