Characterization of antennal sensilla, larvae morphology and olfactory genes of Melipona scutellaris stingless bee

Abstract

There is growing evidence in the literature suggesting that caste differentiation in the stingless bee, Melipona scutellaris, and other bees in the genus Melipona, is triggered by environmental signals, particularly a primer pheromone. With the proper amount of food and a chemical stimulus, 25% of females emerge as queens, in agreement with a long-standing “two loci/two alleles model” proposed in the 1950s. We surmised that these larvae must be equipped with an olfactory system for reception of these chemical signals. Here we describe for the first time the diversity of antennal sensilla in adults and the morphology of larvae of M. scutellaris. Having found evidence for putative olfactory sensilla in larvae, we next asked whether olfactory proteins were expressed in larvae. Since the molecular basis of M. scutellaris is still unknown, we cloned olfactory genes encoding chemosensory proteins (CSP) and odorant-binding proteins (OBPs) using M. scutellaris cDNA template and primers designed on the basis CSPs and OBPs previously reported from the European honeybee, Apis mellifera. We cloned two CSP and two OBP genes and then attempted to express the proteins encoded by these genes. With a recombinant OBP, MscuOBP8, and a combinatorial single-chain variable fragment antibody library, we generated anti-MscuOBP8 monoclonal antibody. By immunohistochemistry we demonstrated that the anti-MscuOBP8 binds specifically to the MscuOBP8. Next, we found evidence that MscuOBP8 is expressed in M. scutellaris larvae and it is located in the mandibular region, thus further supporting the hypothesis of olfactory function in immature stages. Lastly, molecular modeling suggests that MscuOBP8 may function as a carrier of primer pheromones or other ligands.

Morphological assessment of the sensilla of the antennal flagellum in different castes of the stingless bee Tetragonisca fiebrigi

“…Sensilla length was measured using the Image ProPlus 4.5 program (Ravaiano et al , ). We chose to study the dorsal surface of the antennae of T. fiebrigi because, as previously reported for other bees, sensilla are present in higher numbers and are more diverse on the dorsal surface of the appendage (Ravaiano et al , ; González‐Vaquero & Galvani, ; Carvalho et al , ; Galvani et al , ). In our case, there were fewer sensilla (two types of both sensilla trichodea and sensilla placodea) on the ventral surface of the antennae than in the dorsal surface, and only one subtype of sensilla trichodea on the pedicel of all classes of individuals of T. fiebrigi (Fig.…”

“…For instance, males of A. mellifera have a higher number of placodea sensilla than workers, allowing them to locate the queen (Esslen & Kaissling, ; Stort & Moraes‐Alves, ). More recently, studies found differences in the type and number of sensilla among castes and sexes of several species of stingless bees, including the genus Melipona (Nascimento et al , ; Ravaiano et al , ; Campos, ; Carvalho et al , ) .…”

“…Considering the sensilla in stingless bees, the most well‐known species are M. quadrifasciata (De Moraes & Landim, ; Ravaiano et al , ), M. scutellaris (Nascimento et al , ; Carvalho et al , ) , and Scaptotrigona postica (Stort & Barelli, ) . There are few studies on the sensilla of Tetragonisca ; however, among the species of this genus, Tetragonisca angustula is the most studied (Fialho et al , ; Dohanik et al , ).…”

Antennal asymmetry is not associated with social behaviour in Australian Hymenoptera

“…of sensilla per μm 2 ) of that antennomere. For the bee specimens (n = 6 workers of M. tomentifera and n = 5 workers of R. bituberculata), sensilla were typed following Carvalho et al (2017) and Frasnelli et al (2010a). For the bee specimens (n = 6 workers of M. tomentifera and n = 5 workers of R. bituberculata), sensilla were typed following Carvalho et al (2017) and Frasnelli et al (2010a).…”

“…For the ant specimens (n = 5 workers of each species), sensilla were typed following Dumpert (1972). For the bee specimens (n = 6 workers of M. tomentifera and n = 5 workers of R. bituberculata), sensilla were typed following Carvalho et al (2017) and Frasnelli et al (2010a). Head width just posterior to the eyes was calculated as a measure of body size (Boudinot & Fisher 2013;Spaethe et al 2007;Wild 2007).…”