Caecilians are enigmatic limbless amphibians that, with a few exceptions, all have an at least partly burrowing lifestyle. Although it has been suggested that caecilian evolution resulted in sturdy and compact skulls as an adaptation to their head-first burrowing habits, no relationship between skull shape and burrowing performance has been demonstrated to date. However, the unique dual jaw-closing mechanism and the osteological variability of their temporal region suggest a potential relationship between skull shape and feeding mechanics. Here, we explored the relationships between skull shape, head musculature and in vivo bite forces. Although there is a correlation between bite force and external head shape, no relationship between bite force and skull shape could be detected. Whereas our data suggest that muscles are the principal drivers of variation in bite force, the shape of the skull is constrained by factors other than demands for bite force generation. However, a strong covariation between the cranium and mandible exists. Moreover, both cranium and mandible shape covary with jaw muscle architecture. Caecilians show a gradient between species with a long retroarticular process associated with a large and pennate-fibered m. interhyoideus posterior and species with a short process but long and parallel-fibered jaw adductors. Our results demonstrate the complexity of the relationship between form and function of this jaw system. Further studies that focus on factors such as gape distance or jaw velocity will be needed in order to fully understand the evolution of feeding mechanics in caecilians.
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RBINS Staff Publications 2021
Point source contaminations origin from historic or current activities and occur in a variety of forms, extents and contaminants involved (e.g. landfills, industrial facilities, storage tanks, disposal of hazardous waste). Point source contaminations may pose risks to human health and the environment; it is therefore important to develop/improve current methodologies to assess the migration potential of contaminants in groundwater. Groundwater quality monitoring around contaminated sites is typically done by sampling piezometers. Modelling approaches can help to predict the spatial and temporal evolution of contamination plumes, design remediation strategies and assess health and environmental risks. Reactive transport models can potentially improve the prediction of contaminant routes, as they explicitly account for changing geochemical environments and chemical reactions during transport. In spite of recent advances, real-world applications remain scarce as these require large numbers of site-specific parameters. The aim of the RESPONSE project is to improve the use of reactive transport models that simulate the fate of inorganic and organic contaminants in soils and groundwater. More specifically, this project aims to (1) identify the minimum amount of site-specific parameters needed to predict reactive transport of inorganic pollutants (e.g. heavy metals) and (2) improve/simplify the modelling of transport of xenobiotic organic contaminants (XOC, e.g. hydrocarbons and pesticides). The transport of XOCs is particularly complex to model due to the effects and zonation of microbial activity at the plume fringe in polluted aquifers. The RESPONSE project focusses on typical groundwater pollution problems encountered around old municipal landfill sites and cemeteries. Municipal landfills can still release hazardous pollutants such as heavy metals and XOCs, even if they are covered by fresh ground layers after abandonment. Cemeteries can be considered a special case of landfill, releasing various compounds to the environment such as arsenic, mercury, bacteria, viruses and herbicides. Both location types are potential point sources for mixed groundwater pollution, typically including high concentrations of dissolved organic carbon (DOC), heavy metals and XOCs. The methodology in this project involves both experimental and modelling aspects. During the first screening stage, groundwater samples were collected from shallow piezometers at fifteen contaminated sites across Belgium (municipal landfills and cemeteries). Also, an improved reactive transport model is built based on HYDRUS1D-MODFLOW-PHREEQC to explicitly account for the dynamic behaviour of chemical conditions at the soil-ground water interface. Next, based on laboratory analyses, three case-study sites will be selected for further modelling and testing.
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RBINS Staff Publications 2018
