Khawia abbottinae sp. n. (Cestoda: Caryophyllidea) from the Chinese false gudgeon Abbottina rivularis (Cyprinidae: Gobioninae) in China: morphological and molecular data.

Khawia abbottinae sp. n. is described from the Chinese false gudgeon, Abbottina rivularis (Basilewsky) (Cyprinidae: Gobioninae), from the Yangtze River basin in China. The new species can be distinguished from the congeneric species mainly by the arrangements of the testes, which form two longitudinal bands (other congeneric species have the testes irregularly scattered throughout the testicular region) and their number (at maximum 85 testes versus at least 160 in the other Khawia spp.), and the morphology of the scolex, which varies from cuneiform to widely bulbate scolex, being separated from the remaining body by a short neck and possessing a smooth, blunt or rounded anterior margin. Other typical features of K. abbottinae are its small size (total length less than 1.5 cm) and body shape, with the maximum width at its first third. The distinct status of the new species was confirmed by molecular data (ssrDNA and ITS1 sequences). Phylogenetic analyses revealed a close relationship of the new species with K. rossittensis (Szidat, 1937) and K. parva (Zmeev, 1936), parasites of crucian carp and goldfish (Carassius spp.), but both species markedly differ from K. abbottinae in their morphology. Until now, five valid species of Khawia (K. abbottinae, K. japonensis, K. rossittensis, K. saurogobii and K. sinensis) have been reported from China.