Similar Is Not the Same – Mate Recognition in a Parasitoid Wasp

Abstract

Finding and recognizing a suitable mate is a key prerequisite to reproductive success. Insects often recognize prospective mates using chemical cues and signals. Among these, cuticular lipids commonly serve for mate recognition at close range. The lipid layer on the surface of insects is comprised predominantly of cuticular hydrocarbons (CHCs), though more polar compounds may also be present. While the composition of the cuticular profile is typically species specific, many species additionally show differentiation between the sexes by sex specific compounds and/or compound ratios. It is often assumed that a clear sexual dimorphism of cuticular lipid profiles is a prerequisite for a potential function as sex pheromones. Both, sex specific single compounds or the profiles as a whole have been shown to serve as sex pheromones in parasitoid wasps. Here, we studied parasitoid wasps of the species Tachinaephagus zealandicus (Encyrtidae, Hymenoptera). Chemical analyses revealed that this species presents a case where males and females produce the same set of CHCs in similar relative amounts. To test whether these wasps nonetheless can use the cuticular lipids for close range mate recognition, we tested the reaction of males toward freeze-killed conspecifics. Males showed copulation behavior exclusively toward dead females, but not toward dead males. Dead females from which the cuticular lipids had been removed did not elicit copulation behavior by tested males. Reapplication of female whole body extracts restored bioactivity, and males reacted with copulation attempts as often as toward the freeze-killed females. Bioassays with lipid fractions revealed that only the CHC fraction was bioactive on its own. Here, again, males reacted to female, but not to male CHCs. Our results indicate that these wasps are capable of using CHCs for close range sex recognition despite the similarity of male and female profiles.

Silencing Doublesex expression triggers three-level pheromonal feminization in Nasonia vitripennis males

“…The attractiveness of the blend is often based on the quantity and ratio of the pheromone components, which may be correlated with nutritional condition, age or gamete quality of the sender [3,4]. Over shorter distances, sex-specific mixtures of low-volatility, fatty acid-derived hydrocarbons on the insect cuticle (cuticular hydrocarbons, CHCs) play a role in the recognition and mating processes of many insect species [5][6][7][8], and species can often be identified by their unique CHC profiles [5,9,10]. In many insects, the same CHC compounds are shared by both sexes but vary in their relative abundance [11][12][13], while others have evolved subsets of sex-specific CHCs to either attract potential mates or to repel competitors [14,15].…”

Cumulative effects of sex pheromone components in mate recognition of Muscidifurax raptorellus

“…To our knowledge, such a cumulative function of the three lipid fractions of different polarities for mate recognition has not been shown before in parasitoid wasps. In most reported cases, female CHCs lead to males spending more time on the filter paper or a dummy treated with that lipid class (Steiner et al, 2006; Ruther et al, 2011), and either CHCs alone or CHCs in combination with only one other lipid fraction or glandular secretions constituted the mate recognition signal (Steiner et al, 2006; Ruther et al, 2011; Ablard et al, 2012; Kühbandner et al, 2012; Stökl et al, 2014; Weiss et al, 2015; Böttinger et al, 2020; Würf et al, 2020; Jungwirth et al, 2021). Our results suggest that although sex‐specific CHC profiles are often considered to be an indication for the high potential of CHCs to function for mate recognition, this assumption should be taken with caution.…”

“…Thereafter, the solvent was evaporated, and the extract was re-dissolved in 400 µl of hexane (2 µl per individual). For fractionation, we prepared silica gel cartridges (Chromabond 100 mg; Macherey & Nagel, Düren, Germany) and fractionated aliquots of 100 µl of extract as described in Jungwirth et al (2021), eluting the compounds successively with 1 ml of each hexane, DCM, and methanol.…”

Reproductive Isolation in the Cryptic Species Complex of a Key Pest: Analysis of Mating and Rejection Behaviour of Onion Thrips (Thrips tabaci Lindeman)

“…Divergence among cross and control pairings in the T. tabaci cryptic species complex appears to start only after interaction, and become even stronger after male mounting, indicating the presence of cues acting only upon contact, such as CHCs. Communication in arthropods by CHCs seems to be widespread [22,23], and such substances have already been studied in thrips [85,86]. Despite the clear importance of CHCs in insect communication for mate recognition, there seems to be a discrepancy in the reliance solely on CHCs as sexual cues [24].…”

“…In order to mate, first the individuals of an insect pair need to be brought together from a distance, e.g., by means of volatile sex pheromones, then close range communication helps to identify each other as potential mating partners [20,21]. In this close-range recognition, cuticular hydrocarbons (CHCs) seem to play an important role in insects [22,23]; however, other types of cue might also be necessary [24,25].…”