Ontogenetic changes in the ventral colouration of post metamorphic Elachistocleis haroi Pereyra, Akmentins, Laufer, Vaira, 2013 (Anura: Microhylidae)

Ontogenetic colour change (OCC) is defined as the progressive and non-reversible process of changes in colouration of organisms associated with their development. Among the many vertebrate groups, amphibians are particularly impressive for their strikingly wide variety of colours, colour patterns, and signals, whose evolutionary and ecological significance have been poorly studied. Elachistocleis comprises 18 species currently separated into two main groups based on their ventral colour pattern: one immaculate and the other with specks and/or colour patches. Elachistocleis haroi is a small-sized species within the immaculate venter group, distributed in the Yungas and Dry Chaco ecoregions from which little information is known. In a comprehensive sampling of post-metamorphic individuals of E. haroi at different stages of development we identified a significant in ventral colour pattern, which could denote a progressive filling of yellow colour according to an ontogenetic pattern. To test this hypothesis, we analysed 39 post-metamorphic individuals of E. haroi at different stages of development with imaging procedures. We found that yellow spots and their intensity are significantly related to snout-vent length, as major expansion of colour on the sides, gular region and male chest, as almost no development on the belly. We briefly discuss our findings in relation to sexual display and predation avoidance. To our knowledge, this is the first analysis of post-metamorphic OCC in ventral colouration in the genus Elachistocleis.个体发育色彩变化（Ontogenetic Colour Change, OCC）被定义为伴随生物体发育进程的渐进且不可逆的体色变化过程。在众多脊椎动物类群中，两栖动物以其极为丰富多样的体色、色彩模式与信号系统而极具代表性，但其相关进化与生态意义的研究仍较为匮乏。细趾蟾属（Elachistocleis）目前包含18个已描述物种，依据其腹部色彩模式可划分为两个主要类群：一类为无斑点的纯色腹部，另一类则带有斑点或色块。哈罗氏细趾蟾（Elachistocleis haroi）是纯色腹类群中的小型物种，分布于云加斯（Yungas）与干燥查科（Dry Chaco）生态区，目前对该物种的相关研究信息仍十分有限。本研究对不同发育阶段的哈罗氏细趾蟾变态后个体开展了全面采样，观察到其腹部色彩模式存在显著变化，该变化可能遵循个体发育模式下的黄色色素渐进填充过程。为验证这一假说，本研究通过成像技术对39只不同发育阶段的哈罗氏细趾蟾变态后个体进行了分析。研究结果显示，黄色斑点及其着色强度与吻肛长（snout-vent length, SVL）存在显著相关性：个体体侧、咽喉区域以及雄性胸部的色彩显著扩展，而腹部的色彩发育则几乎未发生变化。本研究还简要探讨了上述发现与性展示及反捕食策略之间的关联。据我们所知，本研究是首个针对细趾蟾属（Elachistocleis）物种腹部体色的变态后个体发育色彩变化的分析工作。