Fish can show emotional fever: Stress-induced hyperthermia in zebrafish

Sonia Rey, felicity huntingford, Sebastian Boltana, reynaldo Vargas, Toby Knowles, Simon Mackenzie

Research output: Contribution to journalArticle (Academic Journal)peer-review

43 Citations (Scopus)
263 Downloads (Pure)


Whether fish are sentient beings remains an unresolved and controversial question. Among characteristics thought to reflect a low level of sentience in fish is an inability to showstress-induced hyperthermia (SIH), a transient rise in body
temperature shown in response to a variety of stressors. This is a real fever
response, so is often referred to as ‘emotional fever’. It has been suggested
that the capacity for emotional fever evolved only in amniotes (mammals,
birds and reptiles), in association with the evolution of consciousness in these
groups. According to this view, lack of emotional fever in fish reflects a lack
of consciousness. We report here on a study in which six zebrafish groups
with access to a temperature gradient were either left as undisturbed controls
or subjected to a short period of confinement. The results were striking: compared to controls, stressed zebrafish spent significantly more time at higher
temperatures, achieving an estimated rise in body temperature of about
2–48C. Thus, zebrafish clearly have the capacity to show emotional fever.
While the link between emotion and consciousness is still debated, this finding
removes a key argument for lack of consciousness in fish.
Original languageEnglish
Article number20152266
Number of pages7
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1819
Early online date25 Nov 2015
Publication statusPublished - Nov 2015

Bibliographical note

Date of Acceptance: 28/10/2015


  • zebrafish
  • ecthotherms
  • fish welfare
  • fish sentience
  • emotional fever
  • stress-induced hyperthermia
  • consciousness


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