The antennal sensilla of Melipona quadrifasciata (Hymenoptera: Apidae: Meliponini): a study of different sexes and castes

Abstract

The sensilla of insects are integumental units that play a role as sensory structures and are crucial for the per- ception of stimuli and for communication. In this study, we compared the antennal sensilla of females (workers and queens), males (haploid (n) and diploid (2n)), and queen-like males (QLMs, resulting from 2n males after juvenile hormone (JH) treatment) in the stingless bee Melipona quadrifasciata. Images of the dorsal antenna surfaces were acquired using a scanning electron microscope. As reported for other hyme- nopterans, this species exhibits a heterogeneous sensillar dis- tribution along the antennae. Thirteen different types of sen- silla were found in the antennae of M. quadrifasciata: trichodea (subtypes I to VI), chaetica (subtypes I and II), placodea, basiconica, ampullacea, coeloconica, and coelocapitula. Sensilla trichodea I were the most abundant, followed by sensilla placodea, which might function in olfac- tory perception. Sensilla basiconica, sensilla chaetica I, sen- silla coeloconica, and sensilla ampullacea were found exclu- sively in females. In terms of the composition and size of the sensilla, the antennae of QLMs most closely resemble those of the 2n male, although QLMs exhibit a queen phenotype. This study represents the first comparative analysis of the antennal sensilla of M. quadrifasciata. The differences found in the type and amount of sensilla between the castes and sexes are discussed based on the presumed sensillary functions.