The dissertation is focused on the morphology of the sting of Crabronidae (Insecta: Hymenoptera), its interconnection with the organ’s functions, and with the group phylogeny. Previous studies of Crabronidae sting were rather fragmentary. A rigorous assessment of Crabronidae sting characters required an extension of knowledge on morphology of the organ. Some morphological characters of Crabronidae sting were hypothesized to be associated with traits of the prey or peculiar functions of this organ, like transportation of an impaled prey by Oxybelus species. However, some of these hypotheses contradict each other, necessitating more detailed and intercomparable data on the sting morphology to revise them. Recent studies of the phylogeny of the Crabronidae are based on molecular data. These studies are partly inconsistent and sometimes rejected by some authors due to the omission of morphological data. An assessment of the phylogenetic significance of the sting characters could demonstrate the value of this organ as a source of information for evolutionary research. Therefore, this work aimed to provide a morpho-functional characterization of the sting of wasps of the family Crabronidae (Insecta: Hymenoptera) and to determine the phylogenetic significance of its characters. To achieve this goal, a comparative and morphological analysis of the Crabronidae sting was carried out. The variability of the microsculpture characters of its skeletal elements in some species was investigated. The sting morpho-functional characters and their connection to the biology of the species were assessed. Besides, the superimposition of sting characters onto the phylogenetic tree of Crabronidae was studied.
The material was collected by the PhD-student personally and also obtained from the collections of Ukraine and Lithuania. 26 species of Crabronidae and related groups were studied. The morphology of the sclerites was studied with light microscopy, autofluorescence of the cuticle – with confocal laser scanning microscopy, fine details of the sculpture and the morphology of the sensilla – with scanning electron microscopy. The curvature of the second valvula and phylogenetic signal of categorical sting traits were measured using scripts in R program with geometric morphometry and Borges method (Borges et al., 2019) respectively. The phylogenetic analysis of the sting characters’ matrix was carried out using maximum parsimony optimality criterion in the PAUP* software.
As a result, the morphology of the sting sclerites of studied species was described in detail for the first time, leading to description of 53 morphological characters of the sting, each of which has two or more states. Nine states of these characters are characterized for Hymenoptera and Crabronidae for the first time. Also, the fine structure of the base of the Crabronidae valvilli was investigated for the first time. Intraspecific variability of two morphological characters of the sting was demonstrated for four wasp species for the first time in digger wasps.
The autofluorescence of the sting cuticle was studied for the first time and shown to correspond to a less sclerotized cuticle in Crabronidae species. Homogeneity of the composition of the cuticle within one specimen and their similarity between species of comparable sizes indicates that the composition of the cuticle does not play a key role in the functional peculiarities of stings of different species. We assume that the distribution of local curvature values along the second valvula affects the distribution of the load in the sclerite, while the well-developed, anteriorly branched dorsal rib of the second valvifer, and sclerotized cuticle in the basal junction influence mechanical stability of the sting in whole in species of the genus Oxybelus during the transportation of the impaled prey. Our results do not support the functional hypotheses stated in literature (Evans, 1962; Radović, 1985; Gadallah, 2001) about the role of barbs on the first valvula, the curvature of the second valvula, and the presence of apical setae of the third valvula in the keeping of the prey impaled on the sting.
The method of Borges with co-authors (Borges et al., 2019) does not show the statistically significant phylogenetic signal of categorial sting characters, while results of the superimposition of these characters on the dendrogram reflecting the modern assessment of the group phylogeny and parsimony analysis of the matrix suggest that some of them are phylogenetically significant. Superimposition of the characters states on the phylogenetic tree suggest four characters to be phylogenetically significant, and five character states to be apomorphic/autapomorhic for some studied genera and species.
The obtained results can be used in the development of concepts of bionic engineering structures for transporting cargo or piercing targets. The work can be used for the course "Modern methods in zoology".
