Sigala Itzel, Lozano-García Socorro, Escobar Jaime, Pérez Liseth, Gallegos-Neyra Elvia
Rev Biol Trop. 2016 Mar;64(1):377-97. doi: 10.15517/rbt.v64i1.18004.
Testate amoebae are common single-celled eukaryotic organisms in aquatic ecosystems. Despite their important role in these ecosystems, and their potential as bioindicators and paleoindicators, they remain poorly studied in Mexico. The major objectives of this study were to: 1) increase knowledge of testate amoebae in Mexico’s tropical lakes, and 2) create a catalog of high-quality scanning electron micrographs that can be used for future ecological and paleoenvironmental studies. We collected surface-sediment samples from 29 lakes, located in the Transmexican Volcanic Belt, one at each lake during June and October 2011, and March 2013. Sediments were collected with an Ekman grab and preserved in anhydrous ethanol. Sub-samples were observed under a stereomicroscope and morphometric data for each species were recorded. Total diameter and aperture diameter were measured on circular tests. Irregularly shaped tests were measured for length and width of the aperture and for the size of the whole test. If a specimen possessed spines, the length of one randomly selected spine was measured. The best-preserved specimen of each taxon was photographed with an optical microscope and a scanning electron microscope (SEM). We found 41 taxa of testate amoebae belonging to the genera: Arcella, Argynnia, Centropyxis, Cucurbitella, Cyclopyxis, Cyphoderia, Difflugia, Euglypha, Lesquereusia, Pentagonia, Pseudodifflugia and Scutiglypha. Twelve species not previously reported for Mexico were recorded, along with 13 varieties. The average number of taxa recorded in each lake was eight, and the highest taxonomic richness was 18. The taxon found in the greatest number of lakes was Centropyxis aculeata var. aculeata. Taxonomic richness varied among lakes in the same region. This could reflect lake-specific differences in environmental conditions, underscoring the need for more detailed studies that include collection of data on physical and chemical variables in the lakes. Our results highlighted the need of further studies for the distribution patterns and ecology of lacustrine testate amoebae.
有壳变形虫是水生生态系统中常见的单细胞真核生物。尽管它们在这些生态系统中发挥着重要作用，并且具有作为生物指示物和古指示物的潜力，但在墨西哥它们仍未得到充分研究。本研究的主要目标是：1）增加对墨西哥热带湖泊中有壳变形虫的了解，2）创建一个高质量扫描电子显微镜图像目录，可用于未来的生态和古环境研究。我们于2011年6月、10月以及2013年3月从位于跨墨西哥火山带的29个湖泊中采集了表层沉积物样本，每个湖泊采集一个样本。沉积物用埃克曼抓斗采集，并保存在无水乙醇中。在体视显微镜下观察子样本，并记录每个物种的形态测量数据。对圆形壳体测量其总直径和孔径。对形状不规则的壳体测量其孔径的长度和宽度以及整个壳体的大小。如果标本有刺，则测量一根随机选择的刺的长度。每个分类单元保存最好的标本用光学显微镜和扫描电子显微镜（SEM）拍照。我们发现了41个有壳变形虫分类单元，属于以下属：表壳虫属、银壳虫属、中心盘虫属、葫芦虫属、环纹虫属、杯形虫属、匣壳虫属、真壳虫属、莱氏虫属、五角虫属、拟匣壳虫属和盾形虫属。记录了12个此前未在墨西哥报道过的物种以及13个变种。每个湖泊记录的分类单元平均数量为8个，最高分类丰富度为18个。在最多湖泊中发现的分类单元是尖顶中心盘虫尖顶变种。同一地区不同湖泊的分类丰富度有所不同。这可能反映了湖泊特定的环境条件差异，强调了需要进行更详细的研究，包括收集湖泊物理和化学变量的数据。我们的结果突出了对湖泊有壳变形虫的分布模式和生态学进行进一步研究的必要性。
