Challenging the concept that eumelanin is the polymorphic brown banded pigment in Cepaea nemoralis

Susanne Affenzeller,Holm Frauendorf,Klaus Wolkenstein,Daniel J Jackson

doi:10.1038/s41598-020-59185-y

Susanne Affenzeller, Holm Frauendorf + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-59185-y

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Journal: Scientific Reports	Publication Date: Feb 12, 2020
Citations: 8	License type: open-access

Affiliation: University of Göttingen

Abstract

The common grove snail Cepaea nemoralis displays a stable pigmentation polymorphism in its shell that has held the attention of scientists for decades. While the details of the molecular mechanisms that generate and maintain this diversity remain elusive, it has long been employed as a model system to address questions related to ecology, population genetics and evolution. In order to contribute to the ongoing efforts to identify the genes that generate this polymorphism we have tested the long-standing assumption that melanin is the pigment that comprises the dark-brown bands. Surprisingly, using a newly established analytical chemical method, we find no evidence that eumelanin is differentially distributed within the shells of C. nemoralis. Furthermore, genes known to be responsible for melanin deposition in other metazoans are not differentially expressed within the shell-forming mantle tissue of C. nemoralis. These results have implications for the continuing search for the supergene that generates the various pigmentation morphotypes.

Highlights

The common grove snail Cepaea nemoralis displays a stable pigmentation polymorphism in its shell that has held the attention of scientists for decades
We test this assumption using two techniques: a newly developed sensitive analytical chemistry method that we recently reported for melanins[14]; and RT-quantitative PCR (qPCR) against melanin pathway genes with reference genes validated for C. nemoralis[15]
To further investigate the spatial distribution of eu- and pheomelanin in C. nemoralis shells we have conducted quantitative measurements of colour-sorted shell fragments

Summary

Introduction

The common grove snail Cepaea nemoralis displays a stable pigmentation polymorphism in its shell that has held the attention of scientists for decades. Our initial analytical chemistry experiments on whole shells of the common yellow banded morph of C. nemoralis detected all four common melanin oxidation products: pyrrole-2,3-dicarboxylic acid (PDCA) and pyrrole-2,3,5-tricarboxylic acid (PTCA) for eumelanin, and thiazole-4,5-dicarboxylic acid (TDCA) and thiazole-2,4,5-tricarboxylic acid (TTCA) for pheomelanin, albeit for eumelanin at levels significantly lower than the darkly pigmented shells of Mytillus edulis[16].

Results

Conclusion