Ndayishimiye Jean Claude, Nyirabuhoro Pascaline, Wang Wenping, Mazei Yuri, Yang Jun
Aquatic EcoHealth Group, Fujian Key Laboratory of Watershed Ecology, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China. University of Chinese Academy of Sciences, Beijing 100049, China..
Zootaxa. 2020 Dec 1;4890(1):zootaxa.4890.1.5. doi: 10.11646/zootaxa.4890.1.5.
Difflugia australis, first described by Playfair (1918), has a unique morphotype. However, in the absence of morphometric data, it has not yet been reliably classified within the largest testate amoeba genus Difflugia. In this study D. australis collected from a subtropical reservoir in southeast China was investigated by means of light and scanning electron microscopy. Basing on biometrical data, we provide an improved diagnosis of this little known species. Difflugia australis is different from other similar congeners (i.e., D. bacillariarum Perty, 1849 and D. elegans Penard, 1890) mainly by the combination of the following features: the shell is broadly ovate, with rounded dome and convex sides converging down to a very short distance from the aperture and diverging suddenly into a short rim (collar). It is usually more or less asymmetrical, with one side being more dilated than the other. The shell surface is slightly smooth, composed of flat siliceous plates of irregular shape and size, mixed with fine grains; microbial spores of comparable forms are spread on the shell surface; particles are often interspersed with a network of organic cement with unique mesh pattern; one (sometimes two) slanting spine-like posterior end of the shell is variable in form; collar is mainly formed by small plates of equal size. The dimensions of the shell are: total shell length 88-106 µm; shell width 53-88 µm; aperture diameter 19-28 µm; collar height 3-6 µm; spine length 3‒23 μm. The size frequency distributions of both total shell length and shell width indicate that it is a size-monomorphic species with low variability.
南方砂壳虫（Difflugia australis）最早由普莱费尔于1918年描述，具有独特的形态类型。然而，由于缺乏形态测量数据，它尚未在最大的有壳变形虫属砂壳虫属中得到可靠分类。在本研究中，通过光学显微镜和扫描电子显微镜对从中国东南部亚热带水库采集的南方砂壳虫进行了研究。基于生物测量数据，我们对这个鲜为人知的物种进行了改进后的诊断。南方砂壳虫与其他相似的同属物种（即1849年的巴氏砂壳虫（D. bacillariarum Perty）和1890年的秀丽砂壳虫（D. elegans Penard））的主要区别在于以下特征的组合：壳呈宽卵形，顶部圆润，凸面汇聚至距开口非常短的距离，然后突然向外扩展成短边缘（领圈）。它通常或多或少不对称，一侧比另一侧更膨大。壳表面略显光滑，由形状和大小不规则的扁平硅质板组成，混有细颗粒；类似形态的微生物孢子散布在壳表面；颗粒常夹杂着具有独特网格图案的有机胶结物网络；壳的一个（有时两个）倾斜的刺状后端形态可变；领圈主要由大小相等的小板组成。壳的尺寸为：壳总长88 - 106微米；壳宽53 - 88微米；开口直径19 - 28微米；领圈高3 - 6微米；刺长3 - 23微米。壳总长和壳宽的尺寸频率分布表明它是一个尺寸单态且变异性低的物种。
