Morphological and molecular study of the poorly known species Pseudanisakis rajae (Yamaguti, 1941) (Nematoda: Acanthocheilidae) from elasmobranchs in the Yellow Sea and Taiwan Strait off the coast of China Liang Li • David I. Gibson • Yuan-Yuan Liu • Lu-Ping Zhang Received: 12 August 2011 / Accepted: 27 August 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Ascaridoid nematodes identified as Pseu- danisakis rajae (Yamaguti, 1941) were collected from the skates Bathyraja smirnovi (Soldatov & Pavlenko), Okamejei kenojei (Mu ¨ller & Henle) and Raja pulchra Liu (Rajiformes: Rajidae) in the Yellow Sea and Taiwan Strait off the coast of China. Their examina- tion using light microscopy and, for the first time, scanning electron microscopy revealed erroneous and previously unreported morphological features, neces- sitating the redescription of this little known species. In addition, specimens of P. rajae collected from the three different hosts were characterised using molec- ular methods by sequencing and analysing the internal transcribed spacer (ITS) of the ribosomal DNA. These new morphological and molecular data enabled an updated diagnosis of this nematode and the presenta- tion of an identification key to the species of Pseudanisakis Layman & Borovkova, 1926. Introduction Our present knowledge of the composition of the ascaridoid nematode fauna of marine fishes from off the coast of China is far from complete, although many species have been described by Hsu ¨(1933), Wu (1927, 1949), Wang (1965, 1984), Yin (1983), Yin & Zhang (1983a, b), Luo (2001) and Luo & Huang (2001). In recent years, two of the authors of the present study (Li L. and Zhang L.-P.) have collected large numbers of ascaridoid nematodes from marine fishes in the Yellow Sea, East China Sea and Taiwan Strait as part of a helminthological survey of Chinese marine fishes. The results of systematic evaluations of some of this material have already been published (Li et al., 2007a, b, 2008). In the present paper, a detailed redescription of the hitherto poorly known nematode Pseudanisakis rajae (Yamaguti, 1941), using both light microscopy and, for the first time, scanning electron microscopy, is presented based on newly collected specimens from the stomach and intestine of the skates Bathyraja smirnovi (Soldatov & Pavlenko), Okamejei kenojei (Mu ¨ller & Henle) and Raja pulchra Liu (Rajiformes: Rajidae) in the Yellow Sea and Taiwan Strait. Previously unreported morphological features are revealed and others corrected. In recent years, molecular techniques, utilising the internal transcribed spacer (ITS) of nuclear ribosomal DNA (rDNA) as a genetic marker, have proved to be particularly useful for the accurate identification of ascaridoid nematodes at the species level for eggs, L. Li Á Y.-Y. Liu Á L.-P. Zhang (&) College of Life Science, Hebei Normal University, 050016 Shijiazhuang, Hebei Province, People’s Republic of China e-mail: lupingzhang0505@yahoo.com.cn D. I. Gibson Department of Zoology, Natural History Museum, Cromwell Road, London SW7 5BD, UK 123 Syst Parasitol (2012) 81:115–123 DOI 10.1007/s11230-011-9331-x