'Freeze or flee' reactions run in fish families

Date:
February 15, 2022
Source:
University of Exeter
Summary:
Families of fish tend to share similar reactions to stressful
situations, new research shows.



FULL STORY ========================================================================== Families of fish tend to share similar reactions to stressful situations,
new research shows.


========================================================================== University of Exeter scientists examined how Trinidadian guppies reacted
to stress -- did they freeze or flee? -- and also measured their hormonal responses.

The study found that some fish tend to produce more of the hormone
cortisol, and that these fish are more likely to flee -- while others
produce less cortisol and tend to freeze. This pattern runs in families.

The findings could help in the breeding of less-stressed fish for
aquaculture (fish farming) and other captivity such as aquariums.

"In the wild, an instinct to flee can help a fish escape from danger,
and a rush of cortisol helps them cope with that stress," said lead
author Dr Tom Houslay, of the Centre for Ecology and Conservation (CEC)
on Exeter's Penryn Campus in Cornwall.

"But in captivity, this reaction is unhelpful -- a chronic, high-cortisol stress response is harmful to health and welfare.



==========================================================================
"Our finding of a genetic link between the hormonal (cortisol) and
behavioural (freeze or flee) reactions suggests fish could be selected
for breeding based on their freeze or flee response.

"By selecting fish that tend to freeze in a stressful situation,
you create a genetic stock with a lower cortisol stress response."
This approach is simpler than other breeding methods, some of which
depend on blood sampling to identify genetic patterns.

"We need to stop thinking of fish as being all the same," said Professor Alastair Wilson, also from the CEC at the University of Exeter.

"Individuals and groups of close genetic relatives vary, and by taking
account of this we can selectively breed captive fish with lower stress
and better health." Biologists have long believed that this "integration"
of behavioural and hormonal responses must exist, but few formal genetic
tests have been carried out.



==========================================================================
In this study -- by a team including the University of Alabama --
researchers tested hormonal reactions by placing individual guppies in isolation for an hour. For a social fish like the guppy, the handling
and isolation is likely to be a mild stressor.

During a stress response, elevated cortisol levels help to shift the
body's energy balance in order to cope with the stressor. This aids
recovery, and prepares the body for any further stressor. Cortisol is a necessary part of coping with stress, but if this response is used too frequently then it can lead to health problems.

Cortisol leaks out through guppies' gills, so their hormones were measured
by testing the water after they returned to their usual tank.

Behaviour was tested separately, also by placing each guppy in a new
tank, and seeing whether they tended to stay still (freeze) or swim
around trying to escape (flee).

Hundreds of fish were observed in the study, and researchers looked at
the "family tree" of each to see how genetic relatedness correlated with behavioural and hormonal similarities.

The study was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

========================================================================== Story Source: Materials provided by University_of_Exeter. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Thomas M Houslay, Ryan L Earley, Stephen J White, Wiebke Lammers,
Andrew
J Grimmer, Laura M Travers, Elizabeth L Johnson, Andrew J
Young, Alastair Wilson. Genetic integration of behavioural and
endocrine components of the stress response. eLife, 2022; 11 DOI:
10.7554/eLife.67126 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220215095503.htm

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