Chronic social stress impairs thermal tolerance in the rainbow trout (Oncorhynchus mykiss)

Abstract

SUMMARYWhen faced with limited resources, juvenile salmonid fish form dominance hierarchies that result in social stress for socially subordinate individuals. Social stress, in turn, can have consequences for the ability of the fish to respond to additional stressors such as pathogens or exposure to pollutants. In the present study, the possibility that social stress affects the ability of rainbow trout (Oncorhynchus mykiss) to tolerate acute increases in water temperature was investigated. To this end, we first evaluated physiological and cellular stress responses following a 1h heat shock in juvenile fish in dominance hierarchies. We measured stress hormone (cortisol and catecholamines) concentrations and blood, brain and liver tissue levels of three heat shock proteins (HSPs), the stress inducible HSP70, the constitutive HSC70 and HSP90, in dominant and subordinate trout. No effects of social status on the hormonal response to the heat stress were detected, but the cellular heat shock response in the brain and liver of dominant and subordinate individuals was inhibited. We then assessed thermal tolerance in dominant and subordinate fish through critical thermal maximum temperature (CT max ) trials and measured HSPs following the heat shock. Subordinate fish were less thermally tolerant than their dominant counterparts. We conclude that social stress impacts the ability of fish to respond, on a cellular scale and in a tissue-specific manner, to increases in water temperature, with likely consequences for overall fitness.

Effects of nutritional deprivation on juvenile green sturgeon growth and thermal tolerance

“…Fish were directly transferred from their treatment tanks to 12 l aerated, plastic buckets at 18 (handling control), 24, 26, or 28°C, where they remained for a 2-h exposure. Exposure time was based on previous findings of increased levels of HSP70 protein after a 2-h exposure (Dietz and Somero 1993;LeBlanc et al 2011), and acute exposure of 18°C-acclimated green sturgeon to 26°C has been shown to elevate HSP70 protein levels (Wang et al 2013). After the 2-h temperature exposure, fish were abruptly transferred to identical plastic buckets in a holding tank supplied with 18-19.1°C flow-through well water, where they were held for 2 h. Fish were then rapidly euthanized in buffered MS-222 before brain and mucus samples were collected.…”

Hormonal modulation of the heat shock response: insights from fish with divergent cortisol stress responses

“…Water temperature was then raised over 1.5 h from 13°C to 25°C, where it was maintained for 1 h before being returned to 13°C over the course of 15-20 min. This heat shock protocol was selected because similar heating rates and temperatures have been shown to induce a HSP response in rainbow trout (9,26), and because it would allow for comparison between studies. Additional blood samples (0.5 ml) were withdrawn when the water temperature first reached 25°C (HS sample) at the end of the 1-h heat shock (1-h sample), and 8 and 24 h after the initiation of the acute heat shock.…”

“…The rationale for this objective originated from a recent study where we determined that dominant and subordinate trout differed in thermal tolerance with subordinate fish exhibiting a lower critical thermal maximum (CT max ) than dominant fish (26). Like LR and HR fish, fish in dominance hierarchies are characterized by distinctive hormone responses to stress; dominant fish typically exhibit lower circulating cortisol levels than subordinate fish (24,34,42).…”

Thermal tolerance of the crab Pachygrapsus marmoratus: intraspecific differences at a physiological (CTMax) and molecular level (Hsp70)

“…In cells, the constitutive form Hsc70 remains unchanged (e.g., LeBlanc et al 2011) or is only slightly upregulated (up to 2-fold) in certain tissues (e.g., Liu et al 2004;Rendell et al 2006) whereas the inducible form Hsp70, is highly upregulated from low basal levels (Deane and Woo 2005). Thus, as both Hsp70 and Hsc70 confer thermal tolerance (e.g., Fangue et al 2006), accounting for both forms of Hsp70 is a better predictor of thermal tolerance (Sorte and Hofmann 2005).…”

“…Thus, as both Hsp70 and Hsc70 confer thermal tolerance (e.g., Fangue et al 2006), accounting for both forms of Hsp70 is a better predictor of thermal tolerance (Sorte and Hofmann 2005). The use of antibodies that detect both isoforms has already been carried out for HSP90 (e.g., LeBlanc et al 2011). …”