Eumelanin and pheomelanin pigmentation in mollusc shells may be less common than expected: insights from mass spectrometry
Eumelanin and pheomelanin pigmentation in mollusc shells may be less common than expected: insights from mass spectrometry
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DOI：
10.1186/s12983-019-0346-5
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发表时间：
2019-12-23
影响因子：
2.8
通讯作者：
Jackson, Daniel J.
中科院分区：
文献类型：
--
作者：
Affenzeller, Susanne;Wolkenstein, Klaus;Jackson, Daniel J.
装饰许多系统发育不同的软体动物物种的贝壳的几何图案是由跨越可见光谱的色素组成的。尽管早期的化学研究暗示黑色素是一种常用的色素，但令人惊讶的是，用最近的敏感技术产生的证据很少支持这些观察结果。结果在双壳纲、头足纲和腹足纲三种甲壳纲的13种软体动物中首次采用质谱法测定了真黑素和幻黑素的存在。在双壳贝类Mytilus edulis中，我们证明真黑素主要发生在外壳的最外层，非矿化和高度色素层（通常称为膜）。我们还在头足类鹦鹉螺（Nautilus pompilius）和海洋腹足类Clanculus pharaonius和Steromphala adriatica的贝壳中发现了真黑素。在陆生腹足动物中，我们首次在软体动物的壳中证实了现象黑色素的存在。令人惊讶的是，在大量的棕色/黑色贝壳中，我们没有发现任何证据表明这两种黑色素存在。结论在复杂的生物样品分析中，我们建议采用高效液相色谱-质谱检测等方法，以避免黑色素的假阳性鉴定。我们的结果表明，许多软体动物物种使用尚未确定的色素来图案他们的壳。这对我们理解软体动物是如何进化出蛋壳着色和图案的能力，以及确定调节这些过程的分子机制具有重要意义。
Background The geometric patterns that adorn the shells of many phylogenetically disparate molluscan species are comprised of pigments that span the visible spectrum. Although early chemical studies implicated melanin as a commonly employed pigment, surprisingly little evidence generated with more recent and sensitive techniques exists to support these observations. Results Here we present the first mass spectrometric investigations for the presence of eumelanin and pheomelanin in 13 different molluscan species from three conchiferan classes: Bivalvia, Cephalopoda and Gastropoda. In the bivalve Mytilus edulis we demonstrate that eumelanin mainly occurs in the outermost, non-mineralised and highly pigmented layer of the shell (often referred to as the periostracum). We also identified eumelanin in the shells of the cephalopod Nautilus pompilius and the marine gastropods Clanculus pharaonius and Steromphala adriatica. In the terrestrial gastropod Cepaea nemoralis we verify the presence of pheomelanin in a mollusc shell for the first time. Surprisingly, in a large number of brown/black coloured shells we did not find any evidence for either type of melanin. Conclusions We recommend methods such as high-performance liquid chromatography with mass spectrometric detection for the analysis of complex biological samples to avoid potential false-positive identification of melanin. Our results imply that many molluscan species employ as yet unidentified pigments to pattern their shells. This has implications for our understanding of how molluscs evolved the ability to pigment and pattern their shells, and for the identification of the molecular mechanisms that regulate these processes.