中文摘要：

于2010年11月、2011年5月和8月调查了海南岛臂尾轮虫的多样性，共检出臂尾轮虫25种。其中，东洋界特有种3种：双叉异棘臂尾轮虫（Brachionus donnen bifurcus）、墨氏臂尾轮虫（B．murphyi）和黄氏臂尾轮虫（B．huangi）；东洋界新纪录种1种，刻纹臂尾轮虫（B．sericus）；对折臂尾轮虫（B．dimidiatus）、褶皱二叉臂尾轮虫（B．dichotomus reductus）和奇异方形臂尾轮虫（B．quadridentatus mirabilis）是中国的新纪录种或亚种。方形臂尾轮虫（B．quadridentatus quadridentatus）、萼花臂尾轮虫（B．calyciflorus）、镰形臂尾轮虫（B．falcatus）和角突臂尾轮虫（B．angularis）为常见种类。海南岛臂尾轮属种类多样性高于我国其他地区，并由广布种、全热带种和泛热带种类组成。海南岛与我国其他地区的臂尾轮虫种类组成Bray-Curtis距离指数随着纬度的增加而增加。

英文摘要：

Published information on Rotifera of Hainan Island is fragmentary, and more species than currently recorded may be expected. This contribution is part of an ongoing investigation to examine the species composition and distribution of the Rotifera from a wide range of freshwater habitats on Hainan Island. Species new to China are described based on material （parthenogenetic females） obtained from Hainan Island. Qualitative sampling of the littoral zones of reservoirs, ponds, temporal ponds, brooks, rivers and rice fields on Hainan Island, was carried out in November 2010, May and August 2011. About 134 samples were collected from 134 freshwater habitats （Fig. 1） using 35 ~tm plankton net, and preserved in 5% formaldehyde. In most localities, temperature and pH were measured. Twenty-five species of the genera Brachionus were identified （Table 1）. Brachionus donneri bifurcus, B. huangi and B. murphyi are endemic to the Oriental Zone. Brachionus quadridentatus mirabilis, B. dichotomus reductus, B. dimidiatus, B. huangi, B. lyratus, B. leydigii rotundus and B. sericus are new to Hainan Island. Brachionus quadridentatus mirabilis, B. dichotomus reductus and B. dimidiatus are new to China. Brachionus quadridentatus mirabilis was collected only from a small pond （pH 6.7） with extremely long median anterior, posterolateral and foot-opening spines （Fig. 2）. Brachionus dimidiatus was collected only from a small pond （pH 8.6） with Eichhornia crassipes. Its lorica has no caudal spines, and very short spines on the anterior margin （Fig. 3）. Brachionus dichotomus reductus was collected from a reservoir （pH 7.2） with much elongated median anterior spines and long caudal spines （Fig. 4）. Brachionus quadridentatus quadridentatus, B. calyciflorus, B. falcatus and B. angularis are the most common species in this genus. There are twelve cosmopolitan taxa, eight tropicopolitans taxa and five pantropical taxa on Hainan Island, and the biogeographical affinity of Brachionus has a circumtropical or cos