Species Diversity of Aquatic Mollusks and Their Cercarial Infections; Khao Yai National Park, Thailand

Abstract

Abstract

Aquatic mollusks were investigated by opportunistic collection in Khao Yai National Park,Thailand, every two months from March 2006 to January 2007. Our study focused on thehabitat and species diversity of aquatic mollusks, which can act as intermediate hosts of parasitictrematodes. The study assembled baseline information on parasitic animal and human diseases in thisarea. Three sampling areas were investigated for mollusk diversity: Kongkaew Waterfall, Lam TakhongStream, and Heo Suwat Waterfall. The mollusks were collected by hand-pick and scoop methods. Fivespecies of gastropod and bivalve mollusks were found: Melanoides tuberculata, Filopaludina martensimartensi, Clea (Anentome) helena, Pseudodon mouhoti, and Corbicula javanica. The physicochemicalcharacteristics and water quality of the streams varied slightly from one area to another, and betweenseasons. The water temperature was around 22-25 °C, and dissolved oxygen 7.1-9.5 mg/l. The cercarialinfections of the mollusks collected were investigated by shedding and crushing methods, and werecategorized into three species: Apatemon gracilis, Mesostephanus appendiculatus, and Loxogenoidesbicolor. A. gracilis and M. appendiculatus cercariae were found in the snail C. helena, in Lam TakhongStream and Heo Suwat Waterfall. The infection rates were 4.35% (2/46) and 6.52% (3/46), respectively.L. bicolor was found in the snail F. martensi in Lam Takhong Stream. The infection rate was 2.38% (1/42).M. tuberculata was the most densely populated species of aquatic mollusk in this study, whereasC. helena was the most important species for parasitic disease.

Keywords: aquatic mollusks; intermediate host; cercariae; trematode infections