Husbandry of Zebrafish, Danio Rerio, and the Cortisol Stress Response

Abstract

The effect of common husbandry conditions (crowding, social environment, water quality, handling, and background color) on the cortisol stress response in adult zebrafish, Danio rerio, was investigated to check the usefulness of zebrafish as a model organism in aquaculture research. In addition, a noninvasive methodology for assessing stress was evaluated. Zebrafish showed a fast cortisol response with high values at 30 min that returned to basal levels within 2 h of poststress. There was a significant positive correlation between trunk cortisol concentrations and the free water cortisol rate (r(2)=0.829-0.850, p<0.001), indicating that measurement of the water-borne cortisol release rate may serve as a noninvasive and reliable stress indicator at the population level. Crowding resulted in 13- to 21-fold greater mean trunk cortisol concentrations compared with controls. However, even at low stocking density (2-5 fish/L), the maintenance cost was higher than the one at higher densities (10 fish/L) due to the formation of dominance hierarchies. The background color affected trunk cortisol concentrations, with fish exposed to brighter backgrounds (green and white) showing 3- to 8-fold greater mean trunk cortisol concentrations than fish exposed to a black background or transparent aquaria. Fish exposed to high stocking densities for 2 h or 5 days had similar high mean trunk cortisol levels, indicating that exposure of fish for the period of 2 h to a specific stressor may represent a chronic situation in zebrafish. It is concluded that adult laboratory zebrafish had a preference for a transparent or black background aquarium, at a number of 10 individuals per 2 L of available water volume, to express their normal behavior and avoid increased cortisol stress reaction.

On the proper rearing density in domesticated zebrafish to avoid unwanted masculinization. Links with the stress response

“…However, the most important aspect to consider is that the cortisol levels measured in our fish (<1 ng g −1 M b ) cannot be considered representative of a stressful situation, as reported values in zebrafish subjected to different types of stress (e.g. crowding, handling, visual predator) are much higher, in the range 4-12 ng g −1 (Ramsay et al, 2006;Barcellos et al, 2007;Pavlidis et al, 2013). The lack of a cortisolrelated stress response has been documented in other species such as the gilthead sea bream, Sparus aurata (Barton et al, 2005), and the wedge sole, Dicologoglossa cuneate (Herrera et al, 2015), suggesting that acclimation to a chronic stressor allowed the attenuation of cortisol release, which is more related to the acute rather than the chronic stress response.…”

“…Surprisingly, and opposite to what happens with rodents, where universal husbandry protocols are available, the zebrafish community lacks universal rearing guidelines. Although many authors have focused on the different aspects of rearing conditions (Westerfield, 1995;Casebolt et al, 1998;Trevarrow, 2004;Lawrence, 2007;Pavlidis et al, 2013;Giacomini et al, 2015), a main variable such as rearing density is still not clearly established. Thus, it is urgent to clarify the influence of rearing density on zebrafish sex differentiation.…”

Unpredictable chronic stress decreases inhibitory avoidance learning in Tuebingen Long-Fin zebrafish (Danio rerio Hamilton): stronger effects in the resting phase than in the active phase

“…The zebrafish is a relatively new model in genetics and brain-behaviour research and differences between strains of zebrafish (Egan et al, 2009;Vignet et al, 2013;Wahlsten et al, 2006) as well as rearing conditions within and between laboratories (Mahabir et al, 2013;Parker et al, 2012;Pavlidis et al, 2013) may affect the outcome of experiments. Our data strongly suggest that at a behavioural and physiological level the UCS protocol is robust and reproducible in decreasing inhibitory learning and elevating whole-body cortisol content across strains of zebrafish, i.e.…”

Juvenile Antarctic rockcod,Trematomus bernacchii, are physiologically robust to CO2–acidified seawater

“…Although it is challenging to unravel the specific cause underlying acclimation time effects, wild fish during development may undergo confinement stress with an increase in the cortisol stress hormone, a well-documented occurrence in teleost fishes (Barton and Iwama, 1991;Bonga, 1997). Furthermore, previous studies have shown that laboratory conditions, such as tank color and densities of fish held together, can affect behavior and physiology (Brown et al, 1992;Pavlidis et al, 2013;Hasenbein et al, 2016). For example, when held in lower densities, Arctic char (Salvalinus alpinus) exhibited altered swimming behavior and more aggressive interactions (Brown et al, 1992).…”