Gender-specific reproductive roles are important factors determining sexual dimorphism. Here, we investigate the effects of sex-based differences and reproductive status on the defence of Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae) against infection by Steinernema feltiae (Filipjev, 1934) (Rhabditida: Steinernematidae). Female and male beetles, either virgin or post-copulation, were exposed individually to nematodes. Individuals were then sampled every 12 h, dissected, and checked for the presence of nematodes; we also measured their phenoloxidase (PO) activity. Reproductive status affected resistance to nematodes and PO activity as infected virgin individuals had a higher PO activity and lower mortality than reproducing individuals, with no differences between sexes. Mortality also increased with time, while PO activity did not change. Parasite load was related to reproductive status and sex, with reproducing females with the highest parasite loads in all treatments, and virgin males with more nematodes than sexually active males. Our results indicate that the costs of reproduction impair the immunological system of T. castaneum similarly in both sexes. It is possible, however, that other components of the immunological system that we did not measure, such as lysozyme activity, are impaired by infection with S. feltiae in a sex-specific way., Paulina Kramarz, Dariusz Małek, Maria Gaweł, Szymon M. Drobniak, Joanna Homa., and Obsahuje bibliografii
Among populations of the Miniopterus bats of western Palaearctic, intraspecific variation has not been well documented. Herein we investigate sexual and age variation of these populations using two approaches – linear and geometric morphometrics. We analysed Moroccan (M. maghrebesnis), western and eastern European (M. schreibersii), Levantine (M. schreibersii), and east-Afghanistani (M. cf. fuliginosus) specimens; variation was compared between sexes of the particular specimen sets of three above mentioned Miniopterus spp. and between four age cohorts of
M. schreibersii samples. The results showed in all examined population sets males to be generally larger in size than females, the exception being the east-European animals. Significatly the most divergent sexes were those from eastern Afghanistan, the Levant and eastern Europe. The differences found between sexes in as well as between examined population sets can
be attributed to different life histories and/or to food competition. Weak correlations between patterns of sexual dimorphism and the newly proposed western Palaearctic classification of the Miniopterus bats suggest only a limited contribution of sexual variation to morphological variation in general. Certain aspects of age variaton were found in all examined morphological characters except the non-metric traits, which in turn indicates the importance of these traits for identification of the particular taxon across age categories.
The correlation between dorsal wing colours and spectral sensitivity of the compound eyes of 13 species of thecline butterflies, consisting of 8 sexually monomorphic and 5 dimorphic species, was investigated. Spectral reflectance of the dorsal surfaces of the wings was measured using a spectrophotometer and spectral sensitivities using electroretinography. All 13 species examined showed a common basic pattern of spectral sensitivity with a primary peak at a wavelength of 440–460 nm. Detailed analyses of the deviations in sensitivity from the basic pattern revealed a correlation in monomorphic species with conspicuous wing hues, especially in males., Michio Imafuku., and Obsahuje seznam literatury
Movements are involved in several routine processes and may scale up to important ecological processes such as dispersal. However, movement is affected by a wealth of factors including flight capacity and behavioural traits. Both frequently differ in the sexes, which may well affect movement. We here aim to disentangle the relative importance of sexual differences in flight capacity versus behaviour on small-scale movements under controlled laboratory conditions in the temperate-zone butterfly Lycaena tityrus. The morphology of males is typically associated with increased flight capacity in this species. Nevertheless, the flight performances of the sexes did not differ, but the mobility of the females was higher. Thus, flight capacity and patterns of movement may not be intimately associated. Rather, the costs and benefits of flight seem to differ substantially between the sexes, with females being more mobile, potentially as a risk spreading strategy, while males are territorial and thus more sedentary. Thus, predictions regarding movement based on morphology are difficult.
Throughout most of its range the Palaearctic moth Hepialus humuli shows a striking sexual dimorphism correlated with a dimorphism in wing scale ultrastructure. Male uppersides are uniformly silvery white, due to light reflection from unpigmented scales with an elaborate internal cuticular meshwork; the conspicuous wings are visual cues for females when lekking males swarm at dusk. Female uppersides have a yellow-and-orange pigment pattern, and commonplace scale morphology. Male specimens from the Shetland and Faroe Islands populations are polymorphic, with wing uppersides ranging from the typical uniform white to being patterned much as in females, or even more melanic; forewing length is slightly greater in the darker and patterned male morphs. Male wing-scale polymorphism is only modest: even the superficially most female-like specimens are overall similar to typical males with respect to important details of scale structure. The polymorphic N. Atlantic forms are likely derived from dimorphic ancestors of the continental type. The principal selective force favouring male darkening in these insular populations is most probably a locally strong predation by visual hunters (primarily gulls and terns) on the lekking moths, combined with a lessened importance of the colour-related conspicuousness of males for female mate-searching at the high ambient light level at the swarming time at these high latitudes. This assumption is supported by the finding of a higher abundance of cryptic males (and perhaps by the smaller average size of the non-cryptic male morphs) in sites with intense bird predation.
In the highly sexual-dimorphic nocturnal moth, Acentria ephemerella Denis & Schiffermüller 1775, the aquatic and wingless female possesses a refracting superposition eye, whose gross structural organization agrees with that of the fully-winged male. The possession of an extensive corneal nipple array, a wide clear-zone in combination with a voluminous rhabdom and a reflecting tracheal sheath are proof that the eyes of both sexes are adapted to function in a dimly lit environment. However, the ommatidium of the male eye has statistically significantly longer dioptric structures (i.e., crystalline cones) and light-perceiving elements (i.e., rhabdoms), as well as a much wider clear-zone than the female. Photomechanical changes upon light/dark adaptation in both male and female eyes result in screening pigment translocations that reduce or dilate ommatidial apertures, but because of the larger number of smaller facets of the male eye in combination with the structural differences of dioptric apparatus and retina (see above) the male eye would enjoy superior absolute visual sensitivity under dim conditions and a greater resolving power and ability to detect movement during the day. The arrangement of the microvilli in the rhabdom of both genders suggests that their eyes are polarization-sensitive, an ability they would share with many aquatic insects that have to recognize water surfaces. Although sexual recognition in A. ephemerella is thought to chiefly rely on pheromones, vision must still be important for both sexes, even if the females are wingless and never leave their watery habitat. Females swim actively under water and like their male counterparts, which fly above the surface of the water, they would have to see and avoid obstacles as well as potential predators. This, together with a small incidence of winged females, we believe, could be the reason why the eyes of female A. ephemerella are less regressed than those of other sexually dimorphic moths, like for instance Orgyia antiqua. Another, but difficult to test, possibility is that male and female A. ephemerella have diverged in their behaviour and habitat preferences less long ago than other sexually dimorphic moths.
The expression of sexually dimorphic phenotypes from a shared genome between males and females is a longstanding puzzle in evolutionary biology. Increasingly, research has made use of transcriptomic technology to examine the molecular basis of sexual dimorphism through gene expression studies, but even this level of detail misses the metabolic processes that ultimately link gene expression with the whole organism phenotype. We use metabolic profiling in Drosophila melanogaster to complete this missing step, with a view to examining variation in male and female metabolic profiles, or metabolomes, throughout development. We show that the metabolome varies considerably throughout larval, pupal and adult stages. We also find significant sexual dimorphism in the metabolome, although only in pupae and adults, and the extent of dimorphism increases throughout development. We compare this to transcriptomic data from the same population and find that the general pattern of increasing sex differences throughout development is mirrored in RNA expression. We discuss our results in terms of the usefulness of metabolic profiling in linking genotype and phenotype to more fully understand the basis of sexually dimorphic phenotypes., Fiona C. Ingleby, Edward H. Morrow., and Obsahuje bibliografii
Sexually dimorphic features of adult males and females of Soricidex dimorphus, a species unparalleled in its dimorphism by any described representative of the family Demodecidae, are compared by scanning electron microscopy. The account of sexual dimorphism in S. dimorphus is preceded by a review of sexually dimorphic features in other demodecid genera. Minute constituents of general morphology of demodecid mites such as claws, solenidia and spines of legs or palps, dorsal podosomal tubercles, and integumental slits and pores, part of which are reported and/or shown in scanning electron micrographs for the first time, are also receiving detailed attention.
The winter survival of three closely related univoltine heteropterans that overwinter as adults, Nabis rugosus, N. ericetorum and N. pseudoferus was investigated. After 150 days of low temperature treatment (3-5°C, 16L : 8D, r.h. 70-80%) more males than females died. The mortality rate ranged from 88.8 to 93.8% in males and from 54.2 to 60.7% in females. However, these sexual differences in mortality did not differ significantly across the three species and populations of different geographic origin. It remains a general question whether this considerable evolutionary stability in the sex-specific investment into reproduction and survival phylogenetically conserved or frequently evolves anew to similar levels in separated populations and species. In Nabis rugosus, the relative loss of body mass during overwintering was up to 37.8%. This reflects dramatic somatic costs of adult overwintering and indirectly supports the hypothesis that food supply during overwintering is important for some heteropteran predators. However, body mass before overwintering did not significantly explain the survival pattern in N. rugosus in either sex. The similar sex-specific survival rate of overwintering adult nabids regardless of species and geographic origin can be useful for studies on population dynamics of nabids in agroecosystems and biocontrol.
Sexual dimorphisms in adult size (SSD) and development time (SDTD) occur in many groups of organisms. In insects, some of the best examples occur in parasitoid wasps where most studies report that females are larger than males but take longer to develop. Sex-specific differences in the effects of size on reproductive success is generally regarded as the main factor responsible for SSD in parasitoids. Most studies also assume that development time must be extended in order to achieve larger size. Here, SSD and SDTD were compared in the solitary endoparasitoid, Microplitis mediator that develops in larvae of the moth Pseudoplusia includens. The relationship between male and female body size and development time were isometric in M. mediator, but contradict most predictions of parasitoid development models. Across first to fourth instars at parasitism, male wasps were consistently larger than females but completed their development significantly faster. The longer development time in female wasps was due primarily to an extended pupal phase, whereas the duration of larval development did not vary significantly with offspring sex. Secondary sex ratios (percentage male) also did not vary with host instar. We conclude that SSD in M. mediator is not only a function of extended development time, but also because of several possible factors: (i) selection favours an increase in male size (relative to female size); (ii) female size is constrained because of predation risk, (iii) as a cost of reducing the cost of inbreeding or (iv) constraints on egg maturation rate. We argue that failure to look carefully at how parasitoids grow can lead to incorrect conclusions about the basis or significance of SSD.