Sperm analysis

There is genetic evidence that the two species of Brazilian grey Mazama, Mazama gouazoubira and Mazama nemorivaga, belong to different genera. This study identified significant differences that separated them into distinct groups, by analysing characteristics of the spermatozoa and ejaculate of both species. The characteristics that most clearly differentiated between the species were ejaculate colour, white for M. gouazoubira and reddish for M. nemorivaga, and sperm head dimensions; the area and width were the main variables that distinguished these species. Multivariate analysis of sperm size and sperm head format data accurately discriminated the two species (discrimination between two groups) with low error identification (0.0021), while the individuals analysed (discrimination between 5 groups) formed three groups (error identification = 0.16): group 1, individuals of M. nemorivaga; group 2, individuals of M. gouazoubira; and group 3, a single individual of M. gouazoubira. The results obtained in this work corroborate the hypothesis of the formation of new genera, and subspecies, for species of grey Mazama. Moreover, the low-cost and easily applied method described herein can be used as an auxiliary tool to identify subspecies or sibling species of other taxonomic groups.已有遗传学证据表明，巴西灰短角鹿属（Mazama）的两个物种——灰短角鹿（Mazama gouazoubira）与南美灰短角鹿（Mazama nemorivaga）——实际隶属于不同的属。本研究通过分析两个物种的精子（spermatozoa）与精液（ejaculate）特征，鉴定出了可将二者区分为独立类群的显著差异。二者最直观的区分特征为精液颜色：灰短角鹿的精液呈白色，南美灰短角鹿的精液呈红褐色；此外精子头部尺寸特征同样具备区分效力，其中头部面积与宽度是区分两物种的核心变量。对精子大小与精子头部形态数据开展的多变量分析，可精准区分这两个物种（二分类识别），识别错误率仅为0.0021；而在针对5个类群个体的分析中，样本被划分为3个组（识别错误率为0.16）：第1组为南美灰短角鹿个体，第2组为灰短角鹿个体，第3组仅包含1头灰短角鹿个体。本研究所得结果佐证了灰短角鹿属物种应划分至新属与新亚种的假说。此外，本文所述的低成本且易于操作的方法，可作为辅助工具用于鉴定其他分类类群的亚种或姊妹物种（sibling species）。