Hidden but Potentially Stressed: A Non-Invasive Technique to Quantify Fecal Glucocorticoid Levels in a Fossorial Amphisbaenian Reptile

Abstract

To understand wildlife responses to the changing environment, it is useful to examine their physiological responses and particularly their endocrine status. Here, we validated an enzyme immunoassay (EIA) to non-invasively quantify fecal corticosterone metabolites (FCM) in the fossorial amphisbaenian reptile Trogonophis wiegmanni from North Africa. We supplemented animals assigned to the treatment group with corticosterone dissolved in oil applied non-invasively on the skin for several days, while control groups received the oil-alone solution. Fresh feces were collected at the end of the supplementation period, and FCM levels were quantified by an EIA. Basal FCM levels were similar for both treatments and increased at the end of the test, but FCM increased significantly more in corticosterone-treated animals. A further examination of FCM levels in a wild population of this amphisbaenian did not find overall sexual, size or seasonal differences but showed a high range of variation among individuals. This suggests that different uncontrolled intrinsic or local environmental variables might increase the circulating glucocorticoid levels of different individuals. Our results confirmed the suitability of EIA for analyzing physiological changes in FCM in this amphisbaenian species. This technique may be useful for understanding and remediating the little-explored potential stressors of the soil environment that may negatively affect the health state of fossorial reptiles.

Non‐invasive measurement of glucocorticoids: The reptile perspective

“…Researchers have favoured the use of EIA as analytical technique for FGM in reptiles against RIA, probably because EIAs do not use radioactive substances neither qualified personnel to be performed (Sheriff et al., 2011). Physiological validation by ACTH injection (Ganswindt et al., 2014; Scheun et al., 2018) or corticosterone administration (Martín et al., 2023) has been successfully performed on several occasions, demonstrating that FGM increases reflect the HPI axis activity, similarly to hormone concentrations in urine (Scheun et al., 2018). Failing to detect a relationship between ACTH administration and FGM levels has been mainly attributed to the irregular reptile defecation pattern (Berkvens et al., 2013).…”

Is reproductive management for oestrus detection a stressful routine for female European mink (Mustela lutreola)?

“…Invasive methods require handling and immobilisation of the animal, which can alter basal glucocorticoid concentrations (Sheriff et al 2011), while non-invasive methods avoid handling, thereby minimising measurement bias (Barja et al 2012). A standard method used to measure glucocorticoid levels relies on quantifying metabolites in fresh faecal samples since cortisol is rapidly metabolised and eliminated from the body through faeces, with peak concentrations in mammals occurring between 12 and 48 hours after the stressor stimulus (Barja et al 2012, Navarro-Castilla et al 2021, Martín et al 2023).…”

Multi-Residue Detection of Eight Glucocorticoids by Nano-Au/Fluticasone Propionate Electrochemical Immunosensor

“…Glucocorticoids can inhibit fibroblast proliferation and reduce serotonin formation, thus having a certain whitening effect on the skin [ 8 , 9 ]. Short-term use of skincare cosmetics containing glucocorticoids can create a false appearance of smooth and tender skin [ 10 ]. However, high-dose or long-term use may cause various adverse reactions, such as Cushing’s syndrome [ 11 ], severe infection [ 12 ], osteoporosis [ 13 ], diabetes [ 14 ], behavioral and cognitive changes, etc.…”