Sebomic identification of sex- and ethnicity-specific variations in residual skin surface components (RSSC) for bio-monitoring or forensic applications

Background: “Residual skin surface components” (RSSC) is the collective term used for the superficial layer of sebum, residue of sweat, small quantities of intercellular lipids and components of natural moisturising factor present on the skin surface. Potential applications of RSSC include use as a sampling matrix for identifying biomarkers of disease, environmental exposure monitoring, and forensics (retrospective identification of exposure to toxic chemicals). However, it is essential to first define the composition of “normal” RSSC. Therefore, the aim of the current study was to characterise RSSC to determine commonalities and differences in RSSC composition in relation to sex and ethnicity. Methods: Samples of RSSC were acquired from volunteers using a previously validated method and analysed by high-pressure liquid chromatography–atmospheric pressure chemical ionisation–mass spectrometry (HPLC-APCI-MS). The resulting data underwent sebomic analysis. Results: The composition and abundance of RSSC components varied according to sex and ethnicity. The normalised abundance of free fatty acids, wax esters, diglycerides and triglycerides was significantly higher in males than females. Ethnicity-specific differences were observed in free fatty acids and a diglyceride. Conclusions: The HPLC-APCI-MS method developed in this study was successfully used to analyse the normal composition of RSSC. Compositional differences in the RSSC can be attributed to sex and ethnicity and may reflect underlying factors such as diet, hormonal levels and enzyme expression.Peer reviewedFinal Published versio

Enemies with benefits: parasitic endoliths protect mussels against heat stress

Positive and negative aspects of species interactions can be context dependant and strongly affected by environmental conditions. We tested the hypothesis that, during periods of intense heat stress, parasitic phototrophic endoliths that fatally degrade mollusc shells can benefit their mussel hosts. Endolithic infestation significantly reduced body temperatures of sun-exposed mussels and, during unusually extreme heat stress, parasitised individuals suffered lower mortality rates than nonparasitised hosts. This beneficial effect was related to the white discolouration caused by the excavation activity of endoliths. Under climate warming, species relationships may be drastically realigned and conditional benefits of phototrophic endolithic parasites may become more important than the costs of infestation

Between a rock and a hard place: combined effect of trampling and phototrophic shell-degrading endoliths in marine intertidal mussels

Ecosystems often face a complex combination of natural and anthropogenic disturbances. The assessment of anthropogenic pressures and co-occurring natural stressors is crucial to our understanding of ecosystem structures, dynamics and their conservation. The present study provides the first experimental assessment of the combined effects of trampling (anthropogenic stressor) and endolithic induced erosion (natural stressor) on two coexisting intertidal mussel species, Mytilus galloprovincialis (de Lamarck, 1819) and Perna perna (Linnaeus, 1758). Mixed beds of the two species experiencing a wide range of endolithic parasitation were exposed to increasing intensities of human trampling. Our results clearly show that endolith-infested mussels are more vulnerable to trampling than non-infested individuals. At high trampling intensities, P. perna suffered significantly lower mortalities rates than M. galloprovincialis. More than 20% of large, infested M. galloprovincialis individuals were crushed even at low trampling intensities. Unexpectedly, mortalities rates decreased with mussel size, suggesting a sheltering role of larger conspecifics. Beyond ecological interest, such findings can provide critical experimental support for conservation and management actions.Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) [UID/Multi/04326/2013, IF/01413/2014/CP1217/CT0004]South African Research Chairs Initiative (SARChI) of Department of Science and Technology (DST)National Research Foundation (NRF