PANAITOF, S.C.; SCOTT, M.P.; Univ. of New Hampshire, Durham; Univ. of New Hampshire, Durham: Juvenile hormone and parental responsiveness in single male burying beetles, Nicrophorus orbicollis

Burying beetles, Nicrophorus orbicollis, have facultative biparental care. They bury and prepare small vertebrate carcasses that provide food for their young; both remain to feed and guard the young. Although females are the more active parents, males can raise their young as single parents and compensate for the loss of their mate by adjusting the duration and intensity of parental care to match that of females. Juvenile hormone (JH, the major gonadotropin of insects) may be implicated in the physiology of parental care in burying beetles. In single males JH rises dramatically during larval care and stays elevated longer than in paired males. Here we investigated the relationship between JH titers and parental responsiveness (acceptance or rejection) to larvae of single males. Like females, males changed from infanticide to acceptance before their own larvae hatched. Single male parents were created by removing the female mate 4-2 days before larvae were expected to hatch. Males were given larvae at the time their larvae hatched. They were observed to see if they killed or accepted them then hemolymph samples were taken and JH measured. Single males that reject larvae at the time their own brood hatched had significantly depressed JH compared to those that accept them (p<0.001). Other single males were given larvae 48h or 24h before their own hatched and then again 48h or 24h later when their own hatched and were observed. Each male was bled twice, at the time he rejected and then when he accepted larvae. However only single males that rejected larvae 24h before their own hatched had significantly lower JH than at the time they accepted larvae. It appears that an increase in JH around the time of larval hatching may serve to heighten parental responsiveness.