Demography of gut symbiotic and aposymbiotic Nezara viridula L. (Hemiptera: Pentatomidae)

Abstract

Nezara viridula L. is a highly polyphagous and cosmopolitan pentatomid stink bug. Despite its economic importance, aspects of its biology are poorly understood. N. viridula has one primary bacterium associated with its gastric caeca, which females provide to offspring by smearing it on the surface of eggs during oviposition. We studied the impact of three temperatures and egg mass surface sterilization on N. viridula's nymphal development rate and reproductive performance. Our results show that maintenance of the symbiont is affected both by temperature and egg mass surface sterilization. We detected the symbiont in 100, 84, and 8.3% of the untreated control insects at 20, 25, and 30 degrees C, respectively, by using polymerase chain reaction. In insects originated from surface sterilized egg masses, the symbiont was never detected at 20 or 30 degrees C and was detected in only 1 of 21 insects at 25 degrees C. Nymphal mean development time decreased with increasing temperature, but there were no differences between the sterilized and control treatments. Sterilized insects at 20 degrees C lived longer than insects in any other treatment but never laid eggs. Life table analysis of N. viridula adults showed that net reproductive rate, intrinsic rate of increase, finite rate of increase, and gross reproductive rate were not significantly different among treatments except at 20 degrees C for the surface sterilized treatment. Mean generation time, however, was significantly longer at 20 degrees C (70.96 +/- 4.43 d), regardless of the surface sterilization treatment. Our results highlight the effect that temperature has on the maintenance of this symbiosis and its relationship with N. viridula host's development and reproduction.