ABSTRACT Recent molecular analyses characterized the freshwater crab Trichodactylus fluviatilis as a species complex. Considering this new scenario, studies about the population features are fundamental to understanding the biology of species belongs to this complex. We investigated the population from southeastern Brazil identify as Trichodactylus cf. fluviatilis, testing the hypotheses that sex ratio differs from the expected 1:1, and that the species shows sexual dimorphism in size, weaponry and body weight. The reproductive period and handedness were also investigated. Population features were determined based on the size-frequency distribution, gonadal development and sex ratio. Sexual dimorphism was analysed comparing the average size and the allometric coefficient. Handedness was verified according to the proportion of right and left chelipeds. Sex ratio skewed towards males and the reproduction was continuous. The sexual dimorphism in T. cf. fluviatilis was found in structures related to weaponry and reproduction. In weaponry, sexual dimorphism was demonstrated by robust chelipeds and high allometric values in males. In females, a high allometric was recorded to the abdomen, structure directly related to reproduction. The right-handedness was observed to the species. All these results contribute to a better understanding of the species’ life history.

中文翻译：

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初级淡水蟹 Trichodactylus 的种群特征、性别二态性和左手性 cf. 巴西东南部的河豚（Brachyura：Trichodactylidae）

摘要 最近的分子分析将淡水蟹 Trichodactylus fluviatilis 表征为一个物种复合体。考虑到这种新情况，关于种群特征的研究对于了解属于该复合体的物种的生物学至关重要。我们调查了来自巴西东南部的人口，确定为 Trichodactylus cf。Flviatilis，测试性别比例与预期的 1:1 不同的假设，并且该物种在大小、武器和体重方面表现出性别二态性。还调查了生殖期和惯用手。根据大小频率分布、性腺发育和性别比确定种群特征。比较平均大小和异速生长系数，分析了性二态性。根据左右螯足的比例来验证利手。性别比例偏向雄性，繁殖是连续的。T. cf. 中的性别二态性 在与武器和繁殖相关的结构中发现了fluviatilis。在武器方面，雄性螯足类动物强壮且异速生长值高，证明了性别二态性。在雌性中，记录到腹部的异速生长高，结构与繁殖直接相关。观察到该物种的右手性。所有这些结果都有助于更好地了解该物种的生活史。雄性螯足和高异速生长值证明了性别二态性。在雌性中，记录到腹部的异速生长高，结构与繁殖直接相关。观察到该物种的右手性。所有这些结果都有助于更好地了解该物种的生活史。雄性螯足和高异速生长值证明了性别二态性。在女性中，记录到腹部的异速生长高度，结构与繁殖直接相关。观察到该物种的右手性。所有这些结果都有助于更好地了解该物种的生活史。