Diversity of mollusks in the Lam Ta Khong reservoir, Nakhon Ratchasima, Thailand.

Sampling surveys to study the diversity of mollusks in the Lam Ta Khong reservoir, Nakhon Ratchasima Province, northeast Thailand, were carried out in the hot, rainy and cold seasons. The study area was divided into: Area I--the upper part where the Lam Ta Khong river drains; Area II--the mid-section of the reservoir; Area III--behind the dam. Mollusks were collected from four locations on each bank (to the right and left) of each area. Each location was sampled to include 6 cross-sectional stations; in total, 144 stations were sampled. In the deep water, an Ekman dredge was used to collect samples; the scoop or manual method was used at the water's edge. Ten species of snails and four species of clams were found. The dominant species of snails were: Clea helena, Bithynia siamensis goniomphalos and Melanoides tuberculata; clams were dominated by Corbicula sp. The intermediate host of the human blood fluke was not found. The population of most mollusk species increased during the cold season while that of clams and that of some species of snails increased during the rainy season. Clams and operculate snails predominated in Areas II and III. Pulmonate snails were mostly found close to the bank and on aquatic plants especially in Areas I and II. Operculate snails and clams mainly inhabited water 1 to 10 m deep. Two species of edible mollusks were found: Filopaludina martensi martensi and large numbers of Corbicula. Neither shedding light nor digestion with pepsin A revealed any human parasites in the mollusks sampled.