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Proc Biol Sci. 2018 May 16;285(1878). pii: 20180243. doi: 10.1098/rspb.2018.0243.

Behavioural changes controlled by catecholaminergic systems explain recurrent loss of pigmentation in cavefish.

Author information

1
Department of Biology, University of Maryland, College Park, MD 20742, USA.
2
Department of Molecular Biology, Rudjer Boskovic Institute, 10000 Zagreb, Croatia.
3
Department of Biology, University of South Dakota, Vermillion, SD 57069, USA.
4
Department of Biology, University of Maryland, College Park, MD 20742, USA jeffery@umd.edu.

Abstract

Multiple cave populations of the teleost Astyanax mexicanus have repeatedly reduced or lost eye and body pigmentation during adaptation to dark caves. Albinism, the complete absence of melanin pigmentation, is controlled by loss-of-function mutations in the oca2 gene. The mutation is accompanied by an increase in the melanin synthesis precursor l-tyrosine, which is also a precursor for catecholamine synthesis. In this study, we show a relationship between pigmentation loss, enhanced catecholamine synthesis and responsiveness to anaesthesia, determined as a proxy for catecholamine-related behaviours. We demonstrate that anaesthesia resistance (AR) is enhanced in multiple depigmented and albino cavefish (CF), inversely proportional to the degree of pigmentation loss, controlled by the oca2 gene, and can be modulated by experimental manipulations of l-tyrosine or the catecholamine norepinephrine (NE). Moreover, NE is increased in the brains of multiple albino and depigmented CF relative to surface fish. The results provide new insights into the evolution of pigment modification because NE controls a suite of adaptive behaviours similar to AR that may represent a target of natural selection. Thus, understanding the relationship between loss of pigmentation and AR may provide insight into the role of natural selection in the evolution of albinism via a melanin-catecholamine trade-off.

KEYWORDS:

Astyanax mexicanus cavefish; anaesthesia resistance; loss and reduction of pigmentation; melanin–catecholamine trade-off; norepinephrine; pleiotropy

PMID:
29720416
PMCID:
PMC5966602
DOI:
10.1098/rspb.2018.0243
[Indexed for MEDLINE]
Free PMC Article

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