Social regulation of testicular development in primary and secondary males of the dampwood termite Zootermopsis angusticollis Hagen

Summary.

The effect of the presence of female reproductives, larvae and other reproductive males on growth and testicular development was studied in males of the dampwood termite, Zootermopsis angusticollis. Compared to primary males, secondary males developed testes that were significantly larger under all social conditions tested. Testis diameter was strongly correlated with sperm number in both primary and secondary males, but was negatively correlated with mass gain in primaries and positively correlated with mass gain and secondaries. The presence of female reproductives had no effect on primary male development but promoted mass gain and testicular growth in secondary males. The presence of larvae had a negative effect on primary male body mass, but promoted testicular development. Secondary males nesting with larvae gained more mass and developed larger testes than those nesting without larvae. Co-maturing secondary males did not exhibit differences in testicular development or intrasexual aggression, nor was any one male preferentially allogroomed or fed by nestmates. Co-maturing secondaries are typically closely related and are not likely to engage in reproductive competition. The dissimilar physiological responses of primary and secondary males to social stimuli may reflect adaptations to the distinct social environments in which each reproductive form normally matures.