Identification of Cuticular and Web Lipids of the Spider Argiope bruennichi

Emerging evidence shows that the cuticular and silk lipids of spiders are structurally more diverse than those of insects, although only a relatively low number of species have been investigated so far. As in insects, such lipids might play a role as signals in various contexts. The wasp spider Argiope bruennichi has probably the best investigated chemical communication system within spiders, including the known structure of the female sex pheromone. Recently we showed that kin-recognition in A. bruennichi could be mediated through the cuticular compounds consisting of hydrocarbons and, to a much larger proportion, of wax esters. By use of mass spectrometry and various derivatization methods, these were identified as esters of 2,4-dimethylalkanoic acids and 1-alkanols of varying chain lengths, such as tetradecyl 2,4-dimethylheptadecanoate. A representative enantioselective synthesis of this compound was performed which proved the identifications and allowed us to postulate that the natural enantiomer likely has the (2R,4R)-configuration. Chemical profiles of the silk and cuticular lipids of females were similar, while male cuticular profiles differed from those of females. Major components of the male cuticular lipids were tridecyl 2,4-dimethyl-C17-19 alkanoates, whereas those of females were slightly longer, comprising tridecyl 2,4-dimethyl-C19-21 alkanoates. In addition, minor female-specific 4-methylalkyl esters were detected.

Identification of Cuticular And Web Lipids of The Spider Argiope Bruennichi

Emerging evidence shows that the cuticular and silk lipids of spiders are structurally more diverse than those of insects, although only a relatively low number of species have been investigated so far. As in insects, such lipids might play a role as signals in various context. The wasp spider Argiope bruennichi has probably the best investigated chemical communication system within spiders, including the known structure of the female sex pheromone. Recently we showed that kin-recognition in A. bruennichi is mediated through the cuticular compounds consisting of hydrocarbons and to a much larger proportion of wax esters. By use of MS and various derivatization methods these esters were identified here to be esters of 2,4-di­methyl­alkanoates with varying chain length and 1-alkanols, such as tetradecyl 2,4‑di­methyl­hepta­decanoate. A representative enantioselectively synthesis to this compound was performed which proved the identifications and allowed to postulate the natural enantiomer to have (2R,4R)-configuration. Cuticular profiles of the silk and cuticula of females were similar, while male cuticular profiles differed quantitatively from those of females. In addition, minor female specific 4-methylalkyl esters were detected.

Family-specific chemical profiles provide potential kin recognition cues in the sexually cannibalistic spider Argiope bruennichi

Kin recognition, the ability to detect relatives, is important for cooperation, altruism and also inbreeding avoidance. A large body of research on kin recognition mechanisms exists for vertebrates and insects, while little is known for other arthropod taxa. In spiders, nepotism has been reported in social and solitary species. However, there are very few examples of kin discrimination in a mating context, one coming from the orb-weaver Argiope bruennichi . Owing to effective mating plugs and high rates of sexual cannibalism, both sexes of A. bruennichi are limited to a maximum of two copulations. Males surviving their first copulation can either re-mate with the current female (monopolizing paternity) or leave and search for another. Mating experiments have shown that males readily mate with sisters but are more likely to leave after one short copulation as compared with unrelated females, allowing them to search for another mate. Here, we ask whether the observed behaviour is based on chemical cues. We detected family-specific cuticular profiles that qualify as kin recognition cues. Moreover, correlations in the relative amounts of some of the detected substances between sexes within families indicate that kin recognition is likely based on subsets of cuticular substances, rather than entire profiles.

The possible role of ant larvae in the defence against social parasites

Temporary social parasite ant queens initiate new colonies by entering colonies of host species, where they begin laying eggs. As the resident queen can be killed during this process, host colonies may lose their entire future reproductive output. Selection thus favours the evolution of defence mechanisms, before and after parasite intrusion. Most studies on social parasites focus on host worker discrimination of parasite queens and their offspring. However, ant larvae can also influence brood composition by consuming eggs. This raises the question whether host larvae can aid in preventing colony takeover by consuming eggs laid by parasite queens. To test whether larvae could play a role in anti-parasite defence, we compared the rates at which larvae of a common host species, Formica fusca , consumed eggs laid by social parasite, non-parasite, nest-mate, or conspecific non-nest-mate queens. Larvae consumed social parasite eggs more than eggs laid by a heterospecific non-parasite queen, irrespective of the chemical distance between the egg cuticular profiles. Also, larvae consumed eggs laid by conspecific non-nest-mate queens more than those laid by nest-mate queens. Our study suggests that larvae may act as players in colony defence against social parasitism, and that social parasitism is a key factor shaping discrimination behaviour in ants.

Intraspecific Variation of the Composition of Linear Alkanes in Social Wasp Mischocyttarus consimilis

An important attribute of the evolution and maintenance of sociality in insects is their ability to distinguish members of their own colonies by means of chemical signals during their interactions. Of this type of signals, the cuticular hydrocarbons, responsible among other functions, for intraspecific recognition stand out. Linear alkanes are indicated as the class of compounds that would be most involved in water retention in the body of insects, however, some studies have investigated their role as mediators of interactions. Thus it is possible that there is significant intraspecific variation of its composition, so the objective of this study was to test the hypothesis that linear alkanes vary significantly among populations, castes and sexes, as well as between newly emerged females of different ages of the Mischocyttarus consimilis Zikán 1949 wasp. The samples were analyzed by gas chromatography with flame ionization detector and gas chromatography coupled to mass spectrometry. The results show that there is a significant variation between the chemical cuticular profiles of samples from different populations, as well as between castes, sex and newly emergent workers of different ages. Therefore, it is possible to infer that this class of compounds may vary according to genetic differences between populations, but also by different environmental conditions. The differences between castes, sex and ages suggest that these compounds may also be involved in mediating interactions between nestmates.