Microcercous cercariae possess a very short tail and are produced by digenean species of several families including medically important species, such as members of the genera Paragonimus Braun, 1899, Nanophyetus Chapin, 1927 and Troglotrema Odhner, 1914. During our survey of cercariae of Paragonimus spp. in Vietnam, we found microcercous cercariae from ten (0.29%) out of 3,400 snails of Triculinae gen. sp. 2. They were morphologically and molecularly analysed for species identification. The molecular analysis, based on ITS2 sequences, revealed two distinct species: four specimens were identical to Paragonimus proliferus Hsia et Chen, 1964 (Paragonimidae Dollfus, 1939), and the other six specimens were closest to members of the family Troglotrematidae Odhner, 1914 and were temporarily named Troglotrematidae gen. sp. Morphologically, cercariae of the two species found in this study are similar to each other in their gross characteristics but can be distinguished from one another by subtle morphological details. The cercaria of P. proliferus has an I-shaped excretory bladder and does not have mucous gland cells. In contrast, that of Troglotrematidae gen. sp. has a Y-shaped excretory bladder and mucous gland cells. Besides, the redia of P. proliferus is elongate with a short intestine and contains 5-6 cercariae whereas that of Troglotrematidae gen. sp. is more round with a longer intestine and harbours 3-4 cercariae. Our results have shown the importance of the shape of the excretory bladder and the presence/absence of mucous gland cells of the cercaria as well as the shape and size of the redia, and its intestinal length as valuable taxonomic characters of intramolluscan trematode larvae. In addition, the finding of similar microcercous cercariae of different species in the same snail species suggests that careful attention to morphological details is required in the differentiation of Paragonimus cercariae and those of closely related species., Pham Ngoc Doanh, Hoang Van Hien and Bui Thi Dung., and Obsahuje bibliografii
We found unusual digenean intramolluscan stages, sporocysts and cercariae, in gastropods Sulcospira dautzenbergiana (Morelet) (Caenogastropoda: Pachychilidae) from Southern Vietnam and named them Cercaria cattieni 1. These cercariae have a stylet and thus belong to the Xiphidiata. However, such combination of characters as extremely large body size and I-shaped excretory bladder has not been found before in any other xiphidiocercariae. We obtained COI, ITS1, 5.8S + ITS2, and 28S rDNA sequences for C. cattieni 1. The latter allowed us to specify the phylogenetic position of the discovered cercariae: C. cattieni 1 falls within the superfamily Microphalloidea and is most closely grouped to Pachypsolus irroratus (Rudolphi, 1819) (Pachypsolidae), the sea turtle parasite. Information on the family Pachypsolidae is limited. Judging from the molecular phylogeny, C. cattieni 1 might be the larva of the Pachypsolidae, documented for the first time.