Insect larval development affects adult traits but the biometric relationships are usually poorly understood, including large odonates. In this study, measurements of morphological traits of larvae, exuviae and adults of Anax imperator were recorded. They were used to investigate the effects of early development on adult morphology. Results showed an increase in larval length during the final instar and the length of its exuviae significantly exceeded that of the larva. Length and body mass of teneral adults were strongly related to the length of their exuviae. Adult males were significantly longer than adult females, while both had the same body mass at emergence. Length of teneral adults was negatively related to the date of emergence in both sexes. During maturation, body mass of males only increased slightly whereas that of females increased greatly. Mature specimens were also significantly longer than teneral individuals. Body mass of mature males and length of mature females were both associated with the date of capture. Wing length did not differ between sexes or from data available from Great Britain. This study underscores the importance of taking into account larval growth in order to better understand the adult traits of odonates.
The direction and level of sexual size dimorphism (SSD) was examined in fire-bellied toads from the central Balkans. Samples were taken from 12 populations: three Bombina bombina, three B. variegata variegata and six B. variegata scabra populations. Intersexual variation of 20 morphometric characters was analysed. In addition, correspondence analysis of eight qualitative characters was performed. The results showed that, though body length had an inconsistent pattern of intersexual variation across taxa, other traits contributed to statistically significant level of SSD. The analysis on multivariate level revealed a highly significant effect of population in all three taxa, and significant effect of sex on character variation. Discriminant analysis confirmed a higher level of intersexual differences in B. variegata compared to B. bombina. Correspondence analysis showed that females and males were similar with respect to qualitative traits in all three taxa. At the univariate level, the most prominent features were: significant differences in tibia length in all three taxa, and highly significant differences in head width in B. bombina and in humerus length in B. v. scabra. These results are discussed with respect to specific reproductive behaviour and possible ecological differences between sexes.
Adult body size is the result of important environmental, maternal and/or genetic effects acting on animals during development. Here we investigate how sexual size dimorphism (SSD) develops in seven species of Odonata: Anax imperator, Cordulegaster boltonii, Onychogomphus uncatus, Oxygastra curtisii (Anisoptera), Cercion lindeni, Ischnura graellsii and Platycnemis acutipennis (Zygoptera). SSD of both the last larval and adult stages of the same individuals, which were reared under laboratory conditions, was measured. The aims were to investigate (i) whether SSD develops during the larval stage, (ii) the direction of larval and adult SSD, and (iii) whether the direction of adult SSD can be predicted by the mating system of a given species (e.g. males of territorial species being larger than females and the opposite for non-territorial species). We found that although larval differences in size may be present between the sexes, these are not necessarily shown in the adult stage (they may change or disappear). Also, the mating system was not related to patterns of adult SSD. Differences in SSD in larvae may be caused by differential use of resources via differential niche-utilisation or sex-specific growth patterns. We highlight the fact that sexual selection favouring large male size and fecundity selection, which selects for large females may be acting on the observed patterns in SSD in adults.