Cortisol coregulation in fish

Cortisol coregulation, which is the up- or down-regulation of partners’ physiological stress responses, has been described for individuals with strong attachment bonds, e.g. parents and their children, and romantic relationship partners. Research into moderating effects on cortisol coregulation suggests stronger covariation among distressed partners. Whether cortisol coregulation is unique to humans or can also be found in other species that share universal features of the vertebrate stress response remains unexplored. Using a repeated measures approach and non-invasive waterborne hormone analysis, we test the hypothesis that dyads of three-spined stickleback fish (Gasterosteus aculeatus) coregulate their cortisol levels in shared environments. Dyadic cortisol levels were unrelated when cohabiting (home tank), but significantly covaried when sharing a more stressful (as indicated by higher cortisol levels) environment (open field). Time-lag analysis further revealed that open field cortisol levels were predicted by partner’s cortisol levels prior to the shared experience. To our knowledge, this study provides the first evidence for coregulatory processes on cortisol responses in a non-human animal that lacks strong bonds and social attachment relationships, suggesting a shared evolutionary origin of cortisol coregulation in vertebrates. From an adaptive perspective, cortisol coregulation may serve to reduce risk in challenging, potentially threatening situations

Stress-induced changes in group behaviour

Testing animals in groups can provide valuable data for investigating behavioural stress responses. However, conventional measures typically focus on the behaviour of individual animals or on dyadic interactions. Here, we aimed to determine metrics describing the behaviour of grouping animals that can reveal differences in stress responses. Using zebrafish (Danio rerio) as a model, we observed replicated shoals both immediately and 24 hours after exposure to a novel environment, as an assessment of temporal change in response to an acute stressor. We quantified various standard behavioural measures in combination with metrics describing group structure, including different proximity, social, and spatial metrics. Firstly, we showed a high collinearity between most of the analysed metrics, suggesting that they describe similar aspects of the group dynamics. After metric selection, we found that under acute stress shoals had significantly higher shoal densities, a lower variation in nearest neighbour distances and were in closer proximity to the walls compared to the same groups tested 24 hours later, indicating a reduction in acute stress over time. Thus, the use of group metrics could allow for the refinement of behavioural protocols carried out in a range of research areas, by providing sensitive and rich data in a more relevant social context

Plasma levels of cortisol and glucose in response to capture and tank transference in Rhamdia quelen (Quoy & Gaimard), a South American catfish

Males and females of Rhamdia quelen (Quoy & Gaimard) were subjected to capture and tank transference in order to evaluate the stress response. This process provoked a characteristic stress response in both sexes, with cortisol values reaching a peak in one hour after stress. High levels of cortisol found in females were explained by the increase of energy demand and the mobilization in the vitellogenic phase. Several previous studies have shown that cortisol is strongly correlated to these periods in another catfish.32212112

Plasma steroid concentrations in relation to the reproductive cycle of cultured male Rhamdia quelen

The plasma concentrations of testosterone (T) of cultured jundia Rhamdia quelen increased progressively during spermatogenesis and reached a peak at the beginning of spermiation (e.g. fluidization of the sperm and production of milt). Plasma peaks of T occurred simultaneously to the highest production of T by the testis, however, both plasma concentrations an testis production of T decreased progressively during spermiation. Concentrations of 11-ketotestosterone(11-KT) peaked c. 1 month after the peak of T, concomitant with enhanced production of 11-KT by the testis. The concentrations of 11-KT during the first cycle were extremely high (>1 mug ml(-1)), but less during the second and third cycles, suggesting that this steroid is most important during the pubertal phase in male jundia. Plasma concentrations of both 17-hdroxy-4-pregene-3,20-dione (17-P) and 17,20beta-dihydroxy-4-pregen-3-one (17,20beta-P) Were significantly higher during spermiation than at an other times, and showed little variation. The pattern of steroid changes was cyclical and consistent with their proposed roles in male fish reproduction. (C) 2002 Published by Elsevier Science on behalf of The Fisheries Society of the British Isles.61375176