Dynamic endocrine responses to stress: Evidence for energetic constraints and status dependence in breeding male green turtles

During reproduction, male vertebrates may exhibit a continuum of interactions between sex and adrenal steroids during stressful events, the outcome of which may be important in either reducing or promoting male reproductive success. We studied adult male green turtles (Chelonia mydas) to examine if they altered plasma corticosterone (CORT) and androgen levels in response to a standardized capture/restraint stressor as potential mechanisms to maintain reproductive activity during stressful events. At the population level, we found that migrant breeding males had a significantly smaller CORT response to the capture/restraint stressor compared to nonbreeding males and that this decreased response coincided with the generally poorer body condition of migrant breeders. In contrast, plasma androgen levels decreased significantly in response to the capture/restraint stressor in migrant breeding males, but not in nonbreedinging and premigrant breeding males. For individual mi grant breeding males, the magnitude of their CORT and androgen responses to the capture/restraint stressor was highly correlated with their body condition and body length, respectively. Our results demonstrate that male green turtles exhibit complex interactions in their endocrine responses to a capture/restraint stressor and that variation in these interactions is associated with differences in males' reproductive, energetic, and physical state. We hypothesize that interplay between physical status and plasma hormone responses to stressors could have important consequences for male green turtle reproduction

Adding guarana powder to medfly diets: an alternative for improving the Sterile Insect Technique

ABSTRACT Ceratitis capitata (medfly) is a globally important horticultural pest that can be controlled using the sterile insect technique (SIT), but the success of SIT depends on the sexual performance of mass-reared males when released into the field. We added “guarana” (Paullinia cupana) powder (derived from an Amazonian fruit that is considered to be a stimulant with aphrodisiac effects, capable of improving human physical stamina) to the diets of adult male medflies to determine whether it increased their sexual performance. The basic diet of a protein extract + sucrose (1:3) was enriched with guarana powder (3 % on a volume basis). Experiments examining sexual competitiveness were performed using lab-reared males fed with the enriched diet vs. lab-reared males fed on the basic diet (and lab-reared females fed on the basic diet), as well as lab-reared males fed with the enriched diet vs. wild males fed on the basic diet (and wild females fed on the basic diet). The results of both experiments indicated that males maintained on diets enriched with guarana powder showed higher copulation successes than males fed only with the basic diet. Guarana powder therefore contributed to the greater mating success of lab-reared males (probably because of its stimulant properties), and may represent a new and viable option for increasing SIT effectiveness