Discovery of Encyclometra bungara (Digenea: Encyclometridae) in a new host (Enhydris enhydris) from Thailand and Cambodia through morphological and molecular identification

Abstract

The genus Encyclometra is one of the two genera in family Encyclometridae, known for parasitising the oesophagus, stomach, and intestine of snakes. Among Encyclometra, the species present are: Encyclometra colubrimurorum, Encyclometra japonica, Encyclometra asymmetrica, and Encyclometra bungara. Species discrimination within Encyclometra has predominantly relied on morphological differences, such as the length of the caeca and the position of the testes. Morphological overlaps exist among these species making species discrimination challenging. Additionally, the use of molecular information has been limited for Encyclometra. To determine the Encyclometra species infecting Enhydris enhydris from Thailand and Cambodia, morphological and molecular identification was conducted. Morphological characters and measurements were obtained from 30 Encyclometra adults, and they were compared with previous studies of other Encyclometra species. Novel sequences of E. bungara were generated using the nuclear 18S and 28S ribosomal RNA genes, and the mitochondrial cytochrome c oxidase subunit 1 gene. Our results revealed that the specimens could be morphologically identified as E. bungara, with support from molecular information obtained from the phylogenies of the three genetic markers employed. Molecular analysis showed that the Encyclometra specimens were distinct from E. colubrimurorum and E. japonica. Through morphological and molecular identification of the Encyclometra specimens found in Enhydris enhydris from Thailand and Cambodia, we describe and provide a record of E. bungara in a new host and new locality. Additionally, novel molecular sequences were generated, revealing the phylogenetic position of E. bungara within the superfamily Gorgoderoidea.