Identification of Gangesia oligonchis Roitman & Freze, 1964 (Cestoda: Onchoproteocephalidea) from Tachysurus fulvidraco Richardson in central China: implications for the validity of Gangesia pseudobagrae Chen, 1962.

Owing to the brief and incomplete original description of Gangesia pseudobagrae Chen, 1962 (Cestoda: Onchoproteocephalidea) and high morphological similarity to Gangesia oligonchis Roitman & Freze, 1964 parasitising the same host Tachysurus fulvidraco Richardson, the taxonomic validity of G. pseudobagrae in China remains questionable. Therefore, we sampled and identified specimens of Gangesia Woodland, 1924 from the intestine of T. fulvidraco from three lakes in central China. Morphologically, the sampled specimens almost perfectly corresponded both to G. oligonchis and the limited available description of G. pseudobagrae: rostellum-like organ armed with a single complete circle of hooks (24-31 in number); four uniloculate suckers covered with minute hooklets; genital pore irregularly alternated; testes medullary, spherical to oval; ovary medullary, bi-lobed, follicular; cirrus-sac thick-walled and long; uterus medullary. 28S rDNA sequence also exhibited the highest similarity to G. oligonchis (99.4-99.7%). Phylogenetic analysis showed that 11 individuals of Gangesia from the three lakes in China clustered with G. oligonchis from Russia (no sequence of G. pseudobagrae available on GenBank). Based upon the high similarity of morphology and high similarity of 28S rDNA sequences, the specimens of Gangesia from T. fulvidraco in central China were identified as G. oligonchis. Our results indicate that there is only one species of Gangesia in T. fulvidraco from the Palaearctic region, and thereby support the proposed synonymisation of G. pseudobagrae and G. oligonchis.