Sagaratrema eugari (Tubangui and Masilungan, 1936) (Digenea: Liolopidae) bridges a gap in liolopid diversity in sea snakes.

INTRODUCTION

The family Liolopidae comprises digenean trematodes parasitizing amphibians and reptiles, although the life cycles and evolutionary history of several taxa remain poorly understood. Species of Sagaratrema are primarily associated with marine elapid snakes from the Indo-West Pacific region; however, Sagaratrema eugari is exceptional because it has previously been reported from non-marine snake hosts. This study aimed to identify S. eugari from the little file snake, Acrochordus granulatus, and to provide its first molecular characterization and phylogenetic assessment.

METHODS

During parasitological surveys conducted in the Gulf of Thailand (Surat Thani and Chumphon provinces), five specimens of A. granulatus were examined for helminths. Recovered liolopid trematodes were identified based on morphology and characterized using based on 18S, ITS2, 28S rDNA, and COI mtDNA sequences. Phylogenetic analyses were performed to determine the evolutionary position of the species.

RESULTS

Liolopid trematodes were recovered from all three snakes examined in Surat Thani Province, whereas no infections were detected in the two specimens from Chumphon Province. Morphological observations were consistent with the original description of S. eugari and with the diagnostic features of the genus Sagaratrema. Molecular data provided the first genetic characterization of the species, and phylogenetic analyses confirmed its placement within Sagaratrema. Acrochordus granulatus is identified as a definitive host for S. eugari.

DISCUSSION: This study resolves the previously unknown phylogenetic position of S. eugari and expands the known host range of Sagaratrema beyond hydrophiine sea snakes. The findings suggest that the transmission ecology of S. eugari may involve interactions among mangrove, estuarine, and marine habitats. However, additional sampling across the parasite's geographic range is required to clarify its host associations and elucidate its complete life cycle.