Systematic and transcriptome studies on some species of Bombus Latreille, 1802 (Hymenoptera: Apidae)

The perception of chemical stimuli plays a role in vital decisions such as feeding, reproduction, and avoidance of predators throughout the life cycle of insects. The sense of smell, the sensitive precise discrimination, and interpretation in an unlimited spectrum of chemical information influence a variety of behavioral decisions that directly contribute to the survival of insects. Insects identify volatile molecules mainly through olfactory sensory neurons located in their antennae. In this process, the participation of odorant receptors (ORs), gustatory receptors (GRs), ionotropic receptors (IRs), odorant binding proteins (OBPs), chemosensory proteins (CSPs), and sensory neuron membrane proteins (SNMPs) from chemosensory families are required. The tongue length of the species of Bombus is examined in three groups; short, medium, and long. Tongue length is one of the main factors affecting food preference and the feeding mechanism. In this study, de novo transcriptome assembly was carried out in the antennae of short-tongued B. (Kallobombus) soroeensis and long-tongued B. (Subterraneoombus) fragrans workers to determine the expression variation in chemosensory gene families that play a role in food preferences. With reference-based bioinformatics approaches, 96 ORs, 9 GRs, 17 IRs, 11 OBPs, 5 CSPs, and 1 SNMP genes from the antennal transcriptome of B. soroeensis; 107 ORs, 9 GRs, 18 IRs, 10 OBPs, 5 CSPs and 2 SNMPs genes from the antennal transcriptome of B. fragrans were detected. The genus phylogeny of chemosensory gene families was constructed and selection pressures were determined in each gene family. As a result of comparative analyzes, differences in species-specific ligand susceptibility in ORs, GRs, IRs, OBPs, and CSPs expressions in B. soroeensis and B. fragrans antennae were revealed.