This study evaluated different tissues of naturally contaminated oysters (Crassostrea belcheri) for the presence of noroviruses. RNA from digestive tissues, gills, and mantle of the oysters was extracted and tested for norovirus genogroup (G) I, GII, and GIV using RT-nested PCR. In spiking experiments with a known norovirus, GII.4, the detection limits were 2.97 × 10 RNA copies/g of digestive tissues, 2.62 × 10 RNA copies/g of gills, and 1.61 × 10 RNA copies/g of mantle. A total of 85 oyster samples were collected from a fresh market in Bangkok, Thailand. Noroviruses were found in the oyster samples (40/85, 47%): GI (29/85, 34.1%), GII (9/85, 10.5%), mixed GI and GII (1/85, 1.2%), and GIV (1/85, 1.2%). All three genogroups were found in the digestive tissues of oysters. Norovirus GI was present in all three tissues with the highest frequency in the mantle, and was additionally detected in multiple tissues in some oysters. GII was also detected in all three tissues, but was not detected in multiple tissues in the same oyster. For genogroup I, only GI.2 could be identified and it was found in all tissues. For genogroup II, three different genotypes were identified, namely GII.4 which was detected in the gills and the mantle, GII.17 which was detected in the digestive tissues, and GII.21 which was detected in the mantle. GIV.1 was identified in the digestive tissues of one oyster. This is the first report on the presence of human GIV.1 in oyster in Thailand, and the results indicate oyster as a possible vehicle for transmission of all norovirus genogroups in Thailand.
This study is mainly based on the collection of marine gastropods along the east coast of the Gulf of Thailand which had been carried out along the coastline in 55 sites from the province of Chonburi to Trad during April 2005-December 2009. As many habitats as possible were examined at each sites from sandy beaches, muddy sand, rocky shore, and coral reefs. A total of 306 species of gastropods were collected and had been classifi ed in53families 116genera.The most widespread species were Planaxis sulcatus (Planaxidae) and Polinices mammilla (Naticidae) found in 37 sites, followed by Echinolittorina malaccana (Littorinidae) in 35 sites. The highest diversity was 187 species in Trat whereas Koh Mark had the most abundance in this area. The lowest diversity was in Chanthaburi, 88 species, whereas Koh Nomsoa was the most abundant site.The diversity of gastropods in Chonburi was 152 species, whereas Koh Samaesarn and Koh Juang were the most abundant site. 137 species had been found in Rayong and Koh Munnai was the most abundant site. The data from this study had been compared with the resent studies in the late decade from the west coast of the Gulf of Thailand and Andaman Sea.The total gastropods in the late decade were 454 species 205 genera 69 families.
The presence of small black mussels in the upper intertidal zone of estuarine seashores in Southeast Asia is often overlooked, despite their numerical dominance. Here, we clarify their species identities, taxonomy, geographical distributions and genetic relationships. Our molecular results suggest that three closely related species in East and Southeast Asia form a sister clade to Australian and New Zealand Xenostrobus. Given their distinctness, we resurrect the genus Vignadula to distinguish these two clades. Vignadula atrata, first described from Japan and type species of the genus, is confined to north-east Asia, whilst two other Vignadula species occur natively in Southeast Asia. Of these two species, one is found throughout Thailand, Malaysia, Singapore and Java. We show that this species corresponds to Xenostrobus balani and Xenostrobus mangle described from the Malacca Strait, which are genetically indistinguishable and here considered as one and the same species, Vignadula mangle comb. nov. The other species, Vignadula kuraburiensis sp. nov., described in this study, has so far been found only in south-west Thailand. Members of Vignadula are, in turn, all clearly different from their closest morphological equivalent in Australia, Xenostrobus pulex. A new subfamily Xenostrobinae is proposed to accommodate the two genera Xenostrobus and Vignadula.
Three species of mussels collected from fresh-and low salinity (10 psu or lower) brackish-water environments in southern Thailand, Singapore, northern Borneo and south Sulawesi formed a new, well-supported and distinct mytilid clade based on molecular phylogeny. All are small (< 30 mm) species with either radially ribbed or smooth shells. Internally, the upper edges of the ascending lamellae of the outer and inner demibranchs are, respectively, fused to the mantle lobes and visceral mass. A new genus Parabrachidontes is proposed to accommodate the three species. Of the species in the new genus, one is described as new (Parabrachidontes amnicus sp. n.), and the other two poorly known species (P. leucostictus and P. cochinensis) are re-described. The Parabrachidontes clade is closely related to Mytella, Perna and Arcuatula. Together, they formed a well-supported clade, most members of which have ctenidial edges attached to the mantle and/or visceral mass. These genera are clearly distinct phylogenetically from two other mytilid clades containing brackish-and fresh-water species with ctenidia free of the mantle: one comprising the genera Limnoperna and Sinomytilus (together constituting the Limnoperninae), and the other Xenostrobus and Vignadula (forming the Xenostrobinae). We therefore suggest the existence of at least three lineages of mytilids living in rivers and estuaries of East Asia and Australasia.
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