Filters
Morphology of mandibles of clown beetles (Coleoptera: Histeridae): hidden diversity, sexual dimorphism, and implications for prey range
Abstract Clown beetles (Histeridae) are stable components of carrion communities, but their prey range is poorly recognised. An indirect way to deduce species’ diet is to study the functional morphology of their mandibles. The use of a multimodal approach in the study of Margarinotus brunneus, Margarinotus striola succicola, Saprinus semistriatus, and Saprinus planiusculus revealed a hidden morphological diversity in their mandibles. Geometric morphometric analysis showed inter- and sex-specific differences in their shape. Synchrotron X-ray microtomography revealed variability in musculature between genera and the presence of a joint-like structure at the basal margins in the Saprinus species. Scanning electron microscopy showed variation in the surface of inner margins. Traditional morphometrics revealed differences in mandibular arc according to beetle species, sex, and left and right body sides. All species retained a roughly 17° asymmetry, with the right mandible always having the higher arc. We conclude that Saprinus species are adapted for cutting and puncturing soft-bodied prey, whereas Margarinotus beetles also feed on hard-bodied prey. Future studies should consider our findings for better planning of prey-choice experiments. Emphasis should be placed on recognising whether subtle differences in mandible shape involve differences in diets. This will be critical to determine the role of species in carrion ecosystems.
Trunk climbing among ground-dwelling European amphibians – first observation from Poland
Most European amphibian species are considered land-dwelling, associated with moving along the ground and as poor climbers. However, more recent research indicates that non-arboreal amphibians use nesting boxes and tree hollows in Central and Western Europe. This study describes the first observation of tree climbing by the common toad Bufo bufo (Linnaeus, 1758) and common frog Rana temporaria Linnaeus, 1758 in Poland. While conducting a night survey of newt mortality in the ‘Traszki Ratajskie’ protected area in an urban park in the city of Poznań, Poland, we detected the unexpected use of trees by two species of amphibians. In June 2020, we observed cases of Bufo bufo and Rana temporaria foraging on and using arboreal ambush sites. The toads were found at an average height of 124 cm above the ground, and the frogs at 35 cm, on the tree trunks and branches of two willows (Salix cfr. alba L.) and a dead silver birch specimen (Betula pendula L.). The willows had an extensive multi-stem structure, and exhibited signs of maturity and ageing (hollow-bearing trees with open cavities and crevices). This is the first observation of arboreal behaviour in B. bufo and R. temporaria in Poland. The climbing behaviour and use of tree sites were likely linked to the search for a humid shelter provided by the interior of the ageing trees, as well as to the foraging behaviour that we observed. Trees exhibiting signs of maturity usually have complex structures, and seem particularly important for amphibians during periods of drought, as both a suitable shelter and an area from which to ambush prey. We recommend focusing greater attention on the protection of mature, ageing trees, especially Salix spp. within a terrestrial buffer zone of at least 250 metres from ponds, as these are poorly researched components within amphibian habitats. This type of resource may be essential for long-term amphibian conservation due to site fidelity and the limited number of shelters in human-altered landscapes. The recently adopted EU Nature Restoration Law presents an opportunity to develop good practices in this area, particularly urban tree planting and habitat management.
Brain vs. endocast: Does size differ? A unique experiment based on a cohort of 75 volunteers
AbstractResearch on brain evolution centres mainly on internal mouldings of the skull, known as endocasts; however, the relationship between the size and asymmetry of the brain and endocasts has been poorly investigated in humans. Therefore, the main objective of this study was to investigate whether endocasts can be reliable indicators of brain size and asymmetry. Magnetic Resonance Imaging (MRI) of 75 participants was used to calculate the volume and surface area of the brain, the endocast, and their respective hemispheres. Two asymmetry indices (i.e. directional and absolute asymmetry) were used to assess the differences in volume and surface area between the sides of the brain and endocast. The Pearson correlation coefficient was calculated to assess the relationships between the parameters, and a Monte Carlo simulation for linear regression was performed to generate prediction equations for brain volume. The relationships between the level and direction of asymmetry indices were investigated using the Pearson correlation and McNemar's test, respectively. All correlations were statistically significant; however, correlation coefficients between volumes were stronger (0.894–0.931) than between volumes and surface areas (0.783–0.834). Brain volume can be predicted with high accuracy (ranging between 0.80 and 0.87) using the endocast total volume or the volume of one of the sides. The associations between the levels of asymmetry indices of the brain and endocast were non‐significant; however, the McNemar's test indicated that endocasts show the same left‐ or right‐biased asymmetry as the brain. This was the first study conducted on a large sample of brain and endocast data from the same individuals. The results demonstrated that brain volume can be accurately reconstructed using the volume of the endocast or one of its sides. This finding is especially important in the context of reconstructing fossil skulls, which are usually fragmented. Conversely, the asymmetry levels of endocast parameters are not reliable indicators of the actual level of brain volume asymmetry. Future research on fossils should focus on endocast asymmetry direction (left‐ or right‐biased) as this closely corresponds with brain lateralisation.