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Diseases of Aquatic Organisms

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DAO 58:47-53 (2004)  -  doi:10.3354/dao058047

Investigation of Nematopsis spp. oocysts in 7 species of bivalves from Chonburi Province, Gulf of Thailand

C. Tuntiwaranuruk1,*, K. Chalermwat2, E. S. Upatham3, M. Kruatrachue4, C. Azevedo5

1Department of Biology, Faculty of Science, Burapha University, Chonburi 20131, Thailand
2Department of Aquatic Science, Faculty of Science, Burapha University, Chonburi 20131, Thailand
3Department of Medical Science, Faculty of Science, Burapha University, Chonburi 20131, Thailand
4Department of Biology, Faculty of Science, Mahidol University, Rama 6 Road, Payathai, Bangkok 10400, Thailand
5Department of Cell Biology, Institute of Biomedical Sciences and Center of Marine and Environmental Research, University of Porto, Lg. A.Salazar no 2, 4000 Porto, Portugal

ABSTRACT: This is the first detailed report of Nematopsis spp. in Thai bivalves. A monthly survey was conducted on 7 species of commercial bivalves from Chonburi province, on the eastern seaboard of Thailand, from November 2000 to November 2001 to investigate the prevalence of the apicomplexan parasite Nematopsis Schneider, 1892. Nematopsis spp. sporozoites were found in the cultivated bivalves Arcuatula arcuatula, Anadara granosa and Perna viridis as well as the locally harvested Paphia undulata. They were not found in Donax faba, Meretrix meretrix or Saccostrea cucullata. Using light microscopy, we were able to identiby 4 oocyst morphotypes of the gregarine Nematopsis spp. Prevalence of Nematopsis spp. during the 13 mo sampling period was highest in A. arcuatula (91.8%; n = 110) and lowest in A. granosa (59.2%; n = 130). The morphology of the oocysts differed between hosts, with an average (x ± SD) length/width of 16.28 ± 0.64/12.01 ± 0.35 µm (n = 50) for A. arcuatula, 16.90 ± 0.71/12.69 ± 0.33 µm (n = 50) for A. granosa, 17.61 ± 0.69/12.72 ± 0.36 µm (n = 50) for P. viridis, and 11.21 ± 0.62/8.55 ± 0.52 µm (n = 50) for P. undulata. Identification of oocysts of these apicomplexan gregarines to species was not attempted. The prevalence of infection in relation to habitat and time of sampling is discussed.

KEY WORDS: Nematopsis · Disease · Protozoa · Apicomplexa · Bivalve · Thailand

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