Morphological differences and molecular similarities between Paragonimus bangkokensis and P. harinasutai

Abstract

Paragonimus bangkokensis and Paragonimus harinasutai were found one after another in the same crab host, Potamon smithianus, in Thailand in 1967 and 1968. Both species were also recently found in China and Lao People's Democratic Republic (PDR). Those two Paragonimus spp. are distinguishable from each other by morphological features of metacercariae and adults. However, recently, the DNA sequences of second internal transcribed spacer region (ITS2) and cytochrome oxidase subunit 1 (CO1) genes of those two species in Thailand were reported to be highly similar to each other. In the present study, we collected P. bangkokensis in two provinces in Vietnam (the first record in Vietnam) and both P. bangkokensis and P. harinasutai in Lao PDR for the morphological and molecular phylogenetic analyses to clarify the mutual relationship between the two species. The results show that P. bangkokensis and P. harinasutai were distinguishable from each other by morphology such as the size of metacercariae and the arrangement of cuticular spines of adult worms. However, the molecular phylogenetic analyses of ITS2 and CO1 genes clearly indicate that P. bangkokensis and P. harinasutai make a monophyletic group.

Paragonimus paishuihoensis Metacercariae in Freshwater Crabs, Potamon lipkei, in Vientiane Province, Lao PDR

“…In the present study, molecular phylogenetic analyses revealed that P. paishuihoensis isolates from Lao PDR and Thailand were genetically almost completely identical with each other, thus forming a moderately to well-supported group in ITS2 and CO1 trees. Consistent with the previous reports [14,15], P. paishuihoensis sequences were clustered with P. harinasutai of China with a moderate bootstrap value of 76% to make a group separated from the rest of the P. bangkokensis / P. harinasutai . However, grouping with P. paishuihoensis and P. bangkokensis / P. harinasutai complex was supported by very low bootstrap values (less than 50%), especially in CO1 tree.…”

“…1) in addition to 3 previously reported species; P. harinasutai , Paragonimus heterotremus , and P. bangkokensis [13,14]. By light microscopic observations, these metacercariae were spherical in shape with 2 cyst walls (Fig.…”

Paragonimus and Paragonimiasis in Vietnam: an Update

“…Two types of indels (AT and ATC) were independently observed in ITS2 sequences among P. harinasutai / P. bangkokensis populations. These indels are not species-specific, but have some tendencies to associate with particular geographical populations, indicating recent gene flow between P. harinasutai and P. bangkokensis and recent divergence of these 2 species [16,18]. The recent discovery of naturally hybridized specimen between P. bangkokensis and P. harinasutai in central Vietnam [35] strongly supports their close relationship in the same species complex.…”

“…In that study, P. ohirai was identified based on the presence of grouped spines on the worm surface and possession of a ventral sucker that was larger than the oral sucker. However, these characters are also seen in other species, P. bangkokensis and P. proliferus , of which metacercariae were also discovered in Sin Ho district, Lai Chau Province [15,16]. Metacercariae of P. ohirai have never been found in freshwater crabs in Vietnam.…”

“…Metacercariae may occur in the same individual crab host [18,32-34]. Recent molecular studies provided strong evidence of their close phylogenetic relationship [16,18]. All P. harinasutai and P. bangkokensis populations from Thailand, Lao PDR, and Vietnam (and also P. microrchis from China as a synonym of P. harinasutai ) are genetically highly similar to each other and appear as a species complex in both ITS2 and CO1 trees.…”