Chitons, belonging to class Polyplacophora, are common marine mollusks mainly inhabiting intertidal and shallow subtidal worldwide. They can be recognized by their eight overlapping shell plates (also known as valves), which are firmly surrounded by a tough muscular girdle.

Hainan Island and its vicinity comprise diverse habitats with a highly diverse marine fauna, while the chiton biodiversity of this area is poorly known.

Scientists from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) and Zoological Institute of the Russian Academy of Sciences organized a joint expedition to Hainan to study the chitons.

Based on their cooperative study on samples from this expedition and historical collections, they comprehensively reported the fauna of the living chitons from this area for the first time. Their findings were published in Zootaxa.

The present results showed that a total of 30 species belonging to 18 genera in seven families were recognized in the vicinity of Hainan Island. Six species were reported for the first time from this area, i.e., Rhyssoplax venusta, Lucilina lamellosa, L. tenuicostata, L. tilbrooki, Onithochiton stracki and Acanthochitona intermedia. Several species names were also corrected.

In additions, Callochiton sp. and Plaxiphora sp. were identified as Callochiton multidentatus and Plaxiphora bucklandnicksi, respectively. Acanthochiton sp. from Xisha Islands was identified as A. intermedia. Acanthochitona rubrolineata and Acanthochitona bednalli were excluded from distribution to the South China Sea.

"The eastern part of Hainan Island is influenced by the South China Sea Warm Current that contributes to the dispersal of larvae of warm water species to the north, up to Japan. The western part is located in the Beibu Gulf with relatively cold water in winter. Thus, Hainan Island shares many common species of chitons with Taiwan, Hong Kong, and Vietnam. In this region, we expect more species to be found in the future," said Dr. ZHANG Junlong from IOCAS.

The study was supported by the Bureau of International Cooperation, Chinese Academy of Sciences, and the National Natural Science Foundation of China.