Molecular confirmation of metacercaria of Clinostomum complanatum recovered from one‐stripe spiny eel Macrognathus aral

Abstract

The one-stripe spiny eel (Macrognathus aral, Bloch & Schneider, 1801) under the family Mastacembelidae, a native ornamental fish, were collected from the freshwater ponds and canals of West Bengal, with a purpose to raise the colony as ornamental fish broodstock. During acclimatization, fish were found to be lethargic and reluctant to consume feed followed by the appearance of deep wounds and red patches on the ventral part of the body surface. There was a mortality of 40.49% of affected fish within the next 48 hours. Post-mortem examinations revealed the presence of metacercariae inside the body cavity and on internal organs, spreading up to the buccal cavity. The abundance of the parasite was 15 to 36 numbers per fish. The length of the metacercaria varied from 5.2 mm to 9.8 mm. The metacercariae were identified as Clinostomum complanatum by light microscopy. Further, molecular confirmation of identification was done using PCR amplification and sequencing of the 18S RNA gene. This is the first report of metacercarial infestation of Clinostomum complanatum with molecular confirmation in indigenous M. aral with high ornamental value.