Ibáñez Alejandro, Martín José, Marzal Alfonso, Bertolero Albert
Departamento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006, Madrid, Spain.
Division of Evolutionary Biology, Technical University of Braunschweig, Zoological Institute, Mendelssohnstr. 4, 38106, Braunschweig, Germany.
Naturwissenschaften. 2017 Jun;104(5-6):49. doi: 10.1007/s00114-017-1469-1. Epub 2017 May 24.
Many chelonians have colourful dots, patches and stripes throughout their body that are made up, at least in part, of carotenoids. Therefore, turtles are very suitable models to study the evolution and functionality of carotenoid-based colouration. Recent studies suggested a close link between colouration and immune system in these taxa. However, more research is needed to understand the role of these colourful stripes and patches in turtle visual signalling. The purpose of this study was to explore the relationship between growth rate and colouration in European pond turtles. In particular, we wanted to answer the question of whether there is a trade-off between growth and colour expression. We also aimed to explore the effect of body size and age on colour variation. Turtles from a reintroduction-breeding program were recaptured, weighed and measured over an 8-year period to estimate their growth rates and age. We also measured with a spectrometer the reflectance of colour patches in two different body parts: shell and forelimb. We found that turtles with a faster growth rate had brighter limb stripes independently of their age. On the other hand, shell colouration was related to body size with larger turtles having brighter shell stripes and higher values of carotenoid chroma. Our results suggest that fast-growers may afford to express intense colourful limb stripes likely due to their higher intake of carotenoids that would modulate both growth and colour expression. However, shell colouration was related to body size probably due to ontogenetic differences in the diet, as juveniles are strictly carnivorous while adults are omnivorous. Alternatively, shell colouration might be involved in crypsis as the shell is visually exposed to predators.
许多龟类全身都有色彩斑斓的斑点、斑块和条纹，这些至少部分是由类胡萝卜素构成的。因此，龟是研究基于类胡萝卜素的色彩形成的进化和功能的非常合适的模型。最近的研究表明，在这些分类群中，色彩与免疫系统之间存在密切联系。然而，需要更多的研究来了解这些色彩斑斓的条纹和斑块在龟的视觉信号传递中的作用。本研究的目的是探讨欧洲池龟的生长速度与色彩之间的关系。特别是，我们想回答生长与色彩表达之间是否存在权衡的问题。我们还旨在探讨体型和年龄对色彩变化的影响。在8年的时间里，对一个重新引入繁殖项目中的龟进行重新捕获、称重和测量，以估计它们的生长速度和年龄。我们还用光谱仪测量了两个不同身体部位——背壳和前肢——上彩色斑块的反射率。我们发现，生长速度较快的龟，其肢体条纹更亮，与年龄无关。另一方面，背壳颜色与体型有关，体型较大的龟背壳条纹更亮，类胡萝卜素色度值更高。我们的结果表明，生长速度快的龟可能有能力表现出强烈的彩色肢体条纹，这可能是由于它们摄入了更多的类胡萝卜素，而类胡萝卜素会同时调节生长和色彩表达。然而，背壳颜色与体型有关，这可能是由于饮食的个体发育差异，因为幼龟严格食肉，而成龟是杂食性的。或者，背壳颜色可能与保护色有关，因为背壳在视觉上容易暴露给捕食者。
