The Dynamics of Lepus granatensis and Oryctolagus cuniculus in a Mediterranean Agrarian Area: Are Hares Segregating from Rabbit Habitats after Disease Impact?

The genera Oryctolagus and Lepus (order Lagomorpha) are essential elements in the trophic chain in the Iberian Peninsula, being the main prey of many predators, including some highly endangered predators such as the Iberian lynx (Lynx pardinus). Myxomatosis, a disease producing tumorations in conjunctive tissues, and produced by the Myxoma Virus, has caused mass mortalities in rabbits (Oryctolagus cuniculus) for decades. Recently, the virus has jumped interspecifically from rabbits to hares, and this has created a depletion in hare populations, generating great concern. We analyzed the population dynamics and distribution of both lagomorph species in a Mediterranean agricultural area of the south of Spain since the 1990s with a combination of systematic and non-systematic data. The appearance of the outbreak in the Iberian hare (Lepus granatenis) in 2018 enabled us to undertake an opportunistic analysis of its effects on the spatial structure and assemblages, as well as on the niches of both species using PCA analyses and ordination techniques. Analysis of the mortality effect on daily and seasonal cycles was also conducted, and relations with the temporal dimension was tested using generalized lineal models (GLMs). In our results, in addition to population and temporal patterns, we could observe a restructuring in hare distribution after the mortality event, highlighting that prior to the outbreak, rabbit and hare populations were spatially differentiated, although with some overlaps and niche similarities. However, since the outbreak, hare populations have been excluded from rabbit areas, suggesting that in the absence of rabbits, the virus has more difficulties to infect hares. We also provide an overview of the effect of this population depletion on the ecological and socio-economic dimension of this region, pointing out the importance of this situation for the area.

The Enrichment of Specific Hair Follicle-Associated Cell Populations in Plucked Hairs Offers an Opportunity to Study Gene Expression Underlying Hair Traits.

Gene expression differences can assist in characterizing important underlying genetic mechanisms between different phenotypic traits. However, when population-dense tissues are studied, the signals from scarce populations are diluted. Therefore, appropriately choosing a sample collection method that enriches a particular type of effector cells might yield more specific results. To address this issue, we performed a polyA-selected RNA-seq experiment of domestic horse (Equus ferus caballus) plucked-hair samples and skin biopsies. Then, we layered the horse gene abundance results against cell type-specific marker genes generated from a scRNA-seq supported with spatial mapping of laboratory mouse (Mus musculus) skin to identify the captured populations. The hair-plucking and skin-biopsy sample-collection methods yielded comparable quality and quantity of RNA-seq results. Keratin-related genes, such as KRT84 and KRT75, were among the genes that showed higher abundance in plucked hairs, while genes involved in cellular processes and enzymatic activities, such as MGST1, had higher abundance in skin biopsies. We found an enrichment of hair-follicle keratinocytes in plucked hairs, but detected an enrichment of other populations, including epidermis keratinocytes, in skin biopsies. In mammalian models, biopsies are often the method of choice for a plethora of gene expression studies and to our knowledge, this is a novel study that compares the cell-type enrichment between the non-invasive hair-plucking and the invasive skin-biopsy sample-collection methods. Here, we show that the non-invasive and ethically uncontroversial plucked-hair method is recommended depending on the research question. In conclusion, our study will allow downstream -omics approaches to better understand integumentary conditions in both health and disease in horses as well as other mammals.

Relationships between hair melanization, glutathione levels, and senescence in wild boars.

The synthesis of melanins, which are the most common animal pigments, is influenced by glutathione (GSH), a key intracellular antioxidant. At high GSH levels, pheomelanin (the lightest melanin form) is produced, whereas production of eumelanin (the darkest melanin form) does not require GSH. Oxidative damage typically increases with age, and age-related decreases in GSH have accordingly been found in diverse organisms. Therefore, there should be positive associations between the capacity to produce eumelanic traits, GSH levels, and senescence, whereas there should be negative associations between the capacity to produce pheomelanic traits, GSH levels, and senescence. We explored this hypothesis in a free-ranging population of wild boars Sus scrofa of different ages. As expected from the fact that pheomelanogenesis consumes GSH, levels of this antioxidant in muscle tended to be negatively related to pheomelanization and positively related to eumelanization in pelage, and the degree of pelage pheomelanization was positively related to oxidative damage as reflected by levels of thiobarbituric-acid-reactive substances (TBARS), which is consistent with the hypothesis that pheomelanin synthesis has physiological costs. In our cross-sectional sample, GSH levels did not show senescence effects, and we did not detect senescence effects in pelage melanization. Prime body condition and low TBARS levels were also associated with hair graying, which is attributable to a loss of melanin produced by oxidative stress, thus raising the possibility that hair graying constitutes a signal of resistance to oxidative stress in wild boars. Our results suggest that the degree of melanization is linked to GSH levels in wild boars and that their antioxidant damage shows senescence effects.

Antioxidant machinery differs between melanic and light nestlings of two polymorphic raptors.

Colour polymorphism results from the expression of multiallelic genes generating phenotypes with very distinctive colourations. Most colour polymorphisms are due to differences in the type or amount of melanins present in each morph, which also differ in several behavioural, morphometric and physiological attributes. Melanin-based colour morphs could also differ in the levels of glutathione (GSH), a key intracellular antioxidant, because of the role of this molecule in melanogenesis. As GSH inhibits the synthesis of eumelanin (i.e. the darkest melanin form), individuals of darker morphs are expected to have lower GSH levels than those of lighter morphs. We tested this prediction in nestlings of two polymorphic raptors, the booted eagle Hieraaetus pennatus and the Eleonora's falcon Falco eleonorae, both of which occur in two morphs differing in the extent of eumelanic plumage. As expected, melanic booted eagle nestlings had lower blood GSH levels than light morph eagle nestlings. In the Eleonora's falcon, however, melanic nestlings only had lower GSH levels after controlling for the levels of other antioxidants. We also found that melanic female eagle nestlings had higher levels of antioxidants other than GSH and were in better body condition than light female eagle nestlings. These findings suggest an adaptive response of melanic nestlings to compensate for reduced GSH levels. Nevertheless, these associations were not found in falcons, indicating species-specific particularities in antioxidant machinery. Our results are consistent with previous work revealing the importance of GSH on the expression of melanic characters that show continuous variation, and suggest that this pathway also applies to discrete colour morphs. We suggest that the need to maintain low GSH levels for eumelanogenesis in dark morph individuals may represent a physiological constraint that helps regulate the evolution and maintenance of polymorphisms.