Arin Ngamniyom, Thayat Sriyapai, Pichapack Sriyapai, and Busaba Panyarachun

DOI: 10.14456/sjst-psu.2020.7

pp. 42 - 49

Abstract

The genus Stephanostomum consists of digenean parasites that are found in many marine teleost fish. In this study, we
aimed to describe the metacercarial cysts of Stephanostomum sp. in Javanese ricefish (Oryzias javanicus) collected from brackish
water of mangrove swamps in Sikao District, Trang Province, Thailand. The morphology and tegumental histology of the worms
were examined. Furthermore, molecular phylogenetic trees were established based on 16S, 12S, 18S and 28S ribosomal DNA
(rDNA) sequences, including an analysis of the symbiotic bacteria of Stephanostomum cysts using a 16S rDNA sequencing
method. Partial rDNA sequences of Stephanostomum were highly matched to S. cf. cestillium for percentage of similar identity
from the nucleotide database of GenBank. Proteobacteria and Firmicutes were dominant on parasitic cysts with their
environments. Our results contribute to the understanding of Stephanostomum from the Andaman Sea of Thailand.