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Open Access Research article

Phenotypic plasticity in opsin expression in a butterfly compound eye complements sex role reversal

Andrew Everett1*, Xiaoling Tong1, Adriana D Briscoe2 and Antónia Monteiro1*

Author affiliations

1 Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St, New Haven, CT 06511, USA

2 Department of Ecology and Evolutionary Biology, University of California, Irvine, CA, 92697, USA

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Citation and License

BMC Evolutionary Biology 2012, 12:232  doi:10.1186/1471-2148-12-232

Published: 29 November 2012

Abstract

Background

Animals often display phenotypic plasticity in morphologies and behaviors that result in distinct adaptations to fluctuating seasonal environments. The butterfly Bicyclus anynana has two seasonal forms, wet and dry, that vary in wing ornament brightness and in the identity of the sex that performs the most courting and choosing. Rearing temperature is the cue for producing these alternative seasonal forms. We hypothesized that, barring any developmental constraints, vision should be enhanced in the choosy individuals but diminished in the non-choosy individuals due to physiological costs. As a proxy of visual performance we measured eye size, facet lens size, and sensitivity to light, e.g., the expression levels of all opsins, in males and females of both seasonal forms.

Results

We found that B. anynana eyes displayed significant sexual dimorphism and phenotypic plasticity for both morphology and opsin expression levels, but not all results conformed to our prediction. Males had larger eyes than females across rearing temperatures, and increases in temperature produced larger eyes in both sexes, mostly via increases in facet number. Ommatidia were larger in the choosy dry season (DS) males and transcript levels for all three opsins were significantly lower in the less choosy DS females.

Conclusions

Opsin level plasticity in females, and ommatidia size plasticity in males supported our visual plasticity hypothesis but males appear to maintain high visual function across both seasons. We discuss our results in the context of distinct sexual and natural selection pressures that may be facing each sex in the wild in each season.

Keywords:
Bicyclus anynana; Reaction norm; Ommatidia; Opsin; Sexual dimorphism; Temperature-size rule; Phenotypic plasticity; Body size; Allometry; Vision; Optics