Millerichthys robustus is the only annual killifish distributed in America with phenotypic color variations, not yet described. Accordingly, we first describe the color pattern in both sexes to define its phenotypical variations. We then analyze the frequency of these phenotypes on a geographical scale, in four localities that represent opposite points of Millerichthys’s distribution in the Mexican southeast. Color analysis based on the RGB system allowed us to define five-color phenotypes in males continuously distributed in various perceptual units between two extreme colors (yellow-red): yellow, moderate orange, dark orange, strong orange and red. These color patterns found in M. robustus could be attributed to melanin, carotenoid, and pteridine pigments. The orange phenotypes was present in all localities studied. The yellow phenotype was present only in northeastern and northwestern locations, and the red phenotype was present only in northern populations. Female color variations were observed in the number of ocelli (from 1 to 15) at the base of the caudal peduncle and dorsal region. Ocelli have been associated with anti-predator functions because they resemble the eyes of vertebrates, thus shifting the target of predator attacks to less vital body parts. Females with 3 ocelli were the most frequent phenotype, and females with 13–15 ocelli occurred only in the northern populations. We concluded that male and female of M. robustus are not randomly distributed along their distribution range, which suggest that color phenotypes may react differently to biotic and abiotic factors that probably determine their distribution and frequency within the studied population.

Millerichthysrobustus是美国唯一分布有表型颜色变化的年度kill鱼（尚未描述）。因此，我们首先描述两种性别的颜色模式，以定义其表型变异。然后，我们在四个地区中分析了这些表型的频率，这些地区代表了墨西哥东南部Millerichthys分布的相对点。基于RGB系统的颜色分析使我们能够定义男性的五色表型，这些五色表型连续以各种感知单位分布在两种极端颜色（黄红色）之间：黄色，中度橙色，深橙色，深橙色和红色。在鲁棒分支杆菌中发现这些颜色图案可能归因于黑色素，类胡萝卜素和蝶啶色素。在研究的所有地区都存在橙色表型。黄色表型仅存在于东北和西北部地区，红色表型仅存在于北部人群中。观察到女性的颜色变化，在尾柄和背侧区底部的触骨数量（从1到15）。Ocelli已与抗捕食者功能相关联，因为它们类似于脊椎动物的眼睛，因此将捕食者攻击的目标转移到了不太重要的身体部位。ocelli为3的女性是最常见的表型，ocelli为13–15的女性仅在北部人群中出现。我们得出的结论是，鲁氏支原体的男性和女性 在其分布范围内不是随机分布的，这表明颜色表型对可能决定其在研究人群中的分布和频率的生物和非生物因素的反应不同。