Metabolomic profiling implicates mitochondrial and immune dysfunction in disease syndromes of the critically endangered black rhinoceros (Diceros bicornis)

The critically endangered black rhinoceros (Diceros bicornis; black rhino) experiences extinction threats from poaching in-situ. The ex-situ population, which serves as a genetic reservoir against impending extinction threats, experiences its own threats to survival related to several disease syndromes not typically observed among their wild counterparts. We performed an untargeted metabolomic analysis of serum from 30 ex-situ housed black rhinos (Eastern black rhino, EBR, n = 14 animals; Southern black rhino, SBR, n = 16 animals) and analyzed differences in metabolite profiles between subspecies, sex, and health status (healthy n = 13 vs. diseased n = 14). Of the 636 metabolites detected, several were differentially (fold change > 1.5; p < 0.05) expressed between EBR vs. SBR (40 metabolites), female vs. male (36 metabolites), and healthy vs. diseased (22 metabolites). Results suggest dysregulation of propanoate, amino acid metabolism, and bile acid biosynthesis in the subspecies and sex comparisons. Assessment of healthy versus diseased rhinos indicates involvement of arachidonic acid metabolism, bile acid biosynthesis, and the pentose phosphate pathway in animals exhibiting inflammatory disease syndromes. This study represents the first systematic characterization of the circulating serum metabolome in the black rhinoceros. Findings further implicate mitochondrial and immune dysfunction as key contributors for the diverse disease syndromes reported in ex-situ managed black rhinos.

Impact of Indigestible Materials on the Efficiency of Fecal Corticosterone Immunoassay Testing in Pituophis Species

Measuring fecal glucocorticoid metabolites (FGM) has recently become a sought-after method for assessing stress in animals. While there are many benefits to this methodology, there are also recognized limitations, including the apprehensive interpretation of results. While many factors can influence FGM levels, we aimed to standardize and improve these methods in snakes. Fecal samples were collected from Pituophis species and FGMs were extracted by two different sample collection methods: (1) fecal sample containing undigested materials and (2) fecal samples with undigested materials removed. These extracts were then used to quantify FGM concentrations using a corticosterone EIA kit. The results indicated that the samples with the undigestible materials removed had a 95% increase in overall yield (p < 0.01). Since the collected fecal samples contain 75% undigestible materials by weight, these results support our hypothesis that removing these materials will improve extraction methods for a more reliable measurement of corticosterone. This is the first step towards standardizing the methods for assessing stress by measuring fecal glucocorticoid metabolites in snakes.

A field-friendly alternative to freeze-drying faeces for glucocorticoid metabolite analyses of African wild dogs (Lycaon pictus)

Endocrine studies using faeces as hormone matrix have become increasingly popular to examine adrenocortical activity in wildlife. A prerequisite for this approach is to minimize alteration of faecal glucocorticoid metabolite (fGCM) composition post-defecation. This is done by freezing the collected material as soon as possible after collection, and removing moisture from the frozen faecal samples afterwards (usually by freeze-drying). In remote areas, freeze-drying opportunities are often limited, and in the case of the African wild dog (Lycaon pictus), established assays revealed that fGCM concentrations remain comparable for only ∼24h post-defaecation. In the present study, three cost-effective drying treatments (exposure to sunlight, placement in a solar oven, and use of a food dehydrator) were investigated as alternatives to the golden standard of freeze-drying faeces.•

In comparison to freeze-dried material, African wild dog faecal samples dried through sunlight exposure, a solar oven, and use of a food dehydrator revealed no significant differences in respective fGCM concentrations measured.

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A food dehydrator would be the preferable option to dry African wild dog faeces if limited electrical supply is available. This technique dries faeces the fastest, and negates any reliance on weather conditions.

Monitoring the effects of land transformation on African clawless otters (Aonyx capensis) using fecal glucocorticoid metabolite concentrations as a measure of stress

In a time of increasing environmental change caused by anthropogenic disturbance, there is a greater need to understand animal adaptations to manmade environments. In this regard, the measurement of stress-related endocrine markers provides a useful tool to examine the impact of environmental challenges and the physiological consequences for wildlife occupying such space. The aims of the present study were to validate fecal glucocorticoid metabolite (fGCM) concentrations as a measure of stress using samples from a male African clawless otter (Aonyx capensis; n = 1) and to compare fGCM concentrations of otters occurring in a transformed and in 2 natural areas in South Africa. From the 5 different enzyme-immunoassays (EIA) tested, a cortisol and oxoetiocholanolone (measuring 11,17 dioxoandrostanes) EIA revealed the highest response (74% and 48% increase, respectively) 30 and 24 hours after a stress event (translocation of a captive individual as part of its rehabilitation prior to release), respectively. For both EIAs, fGCM concentrations were comparable for samples collected up to 3 h post-defecation. Using the cortisol EIA for subsequent analyses, fGCM concentrations of animals from the transformed area (n = 20; mean [± SD]: 0.468 [± 0.539] µg/g dry weight [DW]) were significantly higher (P = 0.013) than those from otters in the natural areas (n = 17; 0.242 [± 0.226] µg/g DW). These preliminary results suggest that African clawless otters may have increased adrenocortical activity that could be due to conditions linked to living in a transformed environment.