Testing the adaptive value of gastropod shell morphology to flow: a multidisciplinary approach based on morphometrics, computational fluid dynamics and a flow tank experiment

Abstract A major question in stream ecology is how invertebrates cope with flow. In aquatic gastropods, typically, larger and more globular shells with larger apertures are found in lotic (flowing water) versus lentic (stagnant water) habitats. This has been hypothetically linked to a larger foot, and thus attachment area, which has been suggested to be an adaptation against risk of dislodgement by current. Empirical evidence for this is scarce. Furthermore, these previous studies did not discuss the unavoidable increase in drag forces experienced by the snails as a consequence of the increased cross sectional area. Here, using Potamopyrgus antipodarum as a study model, we integrated computational fluid dynamics simulations and a flow tank experiment with living snails to test whether 1) globular shell morphs are an adaptation against dislodgement through lift rather than drag forces, and 2) dislocation velocity is positively linked to foot size, and that the latter can be predicted by shell morphology. The drag forces experienced by the shells were always stronger compared to the lift and lateral forces. Drag and lift forces increased with shell height but not with globularity. Rotating the shells out of the flow direction increased the drag forces, but decreased lift. Our hypothesis that the controversial presence of globular shells in lotic environments could be explained by an adaptation against lift rather than drag forces was rejected. The foot size was only predicted by the size of the shell, not by shell shape or aperture size, showing that the assumed aperture/foot area correlation should be used with caution and cannot be generalized for all aquatic gastropod species. Finally, shell morphology and foot size were not related to the dislodgement speed in our flow tank experiment. We conclude that other traits must play a major role in decreasing dislodgement risk in stream gastropods, e.g., specific behaviours or pedal mucus stickiness. Although we did not find globular shells to be adaptations for reducing dislodgement risk, we cannot rule out that they are still flow-related adaptations. For instance, globular shells are more crush-resistant and therefore perhaps adaptive in terms of diminishing damage caused by tumbling after dislodgement or against lotic crush-type predators

Genetic diversity of Thaumetopoea pityocampa in Greece: the role of Quaternary changes in Aegean Sea

Thaumetopoea pityocampa, the winter pine processionary moth, is one of the most important pests of pine trees in the Mediterranean region. To learn more about the refugial areas within the greater refugium of Greece, samples from 15 local populations were collected. Analysis of the Cytochrome Oxidase I region identified 15 haplotypes. One strongly supported clade was found, separating the Aegean island of Lesvos from the mainland populations. Mdiv analysis showed that this clade diverged from the general clade 155,000 y.a., suggesting the sea level changes during the Quaternary Period as a possible reason for its seclusion. Additionally, comparisons with similar studies in this region revealed a possible colonization of the eastern Aegean islands from the Turkish mainland rather than from Greece. However, no strong isolation-by-distance events were detected among the mainland populations, which could be attributed to the joint effect of regular gene flow and the lack of insurmountable geographic barriers. Finally, regarding population structure, Bayesian analysis as well as neutrality tests pointed towards an ongoing population expansion which verifies the potential invasiveness of this pest species, something that will have to be dealt with under the influence of climate change

Skin conductance in neonates suffering from abstinence syndrome and unexposed newborns

The aims of this study were to compare the skin conductance (SC) of newborns with opiate-induced neonatal abstinence syndrome (NAS) to that of unexposed newborns and to evaluate the potential of SC readings to detect distress in the context of NAS objectively. The SC of 12 newborns with NAS and 12 unexposed newborns was measured at nine specific times during their first 6 weeks of life. The number of SC fluctuations per second (NSCF/s), the amplitude of SC fluctuation, and the mean level of SC were recorded and analyzed. The SC of newborns treated for symptoms of NAS differed significantly from the SC of unexposed newborns with regard to the NSCF/s (p = 0.04). With the mean level of SC, we observed an interaction between groups over time (p value for interaction = 0.02). With increasing postnatal age, we observed higher values in all three SC parameters. Conclusion: The NSCF/s and the mean level of SC appear to be suitable to reflect the distress of newborns suffering from NAS. As it is known that the sensitivity of SC increases with the level of stress experienced, its potential to indicate elevated stress levels in infants with NAS should be investigated in future studies evaluating different therapy regimens