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Review
. 2023 Feb 10;5(1):62-71.
doi: 10.3390/clockssleep5010007.

Cavefishes in Chronobiological Research: A Narrative Review

Vera V Pavlova  1 , Viacheslav V Krylov  1   2
Affiliations
Review

Cavefishes in Chronobiological Research: A Narrative Review

Vera V Pavlova et al. Clocks Sleep. .

Abstract

Cavefish are vertebrates living in extreme subterranean environments with no light, temperature changes, and limited food. Circadian rhythms in these fish are suppressed in natural habitats. However, they can be found in artificial light-dark cycles and other zeitgebers. The molecular circadian clock has its peculiarities in cavefish. In Astyanax mexicanus, the core clock mechanism is tonically repressed in the caves due to the overactivation of the light input pathway. A lack of functional light input pathway but rather the entrainment of circadian genes' expression by scheduled feeding were revealed in more ancient Phreatichthys andruzzii. Different evolutionarily determined irregularities in the functioning of molecular circadian oscillators can be expected in other cavefish. The unique property of some species is the existence of surface and cave forms. Along with the ease of maintenance and breeding, it made cavefish a promising model for chronobiological studies. At the same time, a divergence of the circadian system between cavefish populations requires the strain of origin to be indicated in further research.

Keywords: Astyanax mexicanus; behavior; caves; circadian clock; light–dark cycle; rhythm.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Blind Mexican tetra Astyanax mexicanus.
See this image and copyright information in PMC

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