Completing the first molecular and morphological characterised life cycle of a crocodilian-infecting diplostomid, Neofibricola smiti (Digenea: Diplostomidae)

Abstract

The life cycles of trematodes infecting crocodilians remain poorly understood, with most species known exclusively from adult stages recovered from definitive hosts.The present study elucidates the life cycle of Neofibricola smiti Achatz, Martens, Kudlai, Junker, Boe et Tkach, 2022 from South Africa and identifies Bulinus sp. as first intermediate host, representing the first confirmed first intermediate host association for a crocodilian-infecting diplostomid.In addition, a metacercaria recovered from the eye viscera of Clarias gariepinus (Burchell, 1822) expands the known range of second intermediate hosts for N. smiti to include a clariid fish.Phylogenetic analyses of partial 28S rDNA, ITS2 rDNA, and COI mtDNA sequences generated from sporocysts, cercariae, and a metacercaria confirmed conspecificity with the sexual adult specimens previously described from the Nile crocodile, Crocodylus niloticus Laurenti, 1768, and metacercariae identified from Müller's clawed frog, Xenopus muelleri (Peters, 1844).The occurrence of metacercariae in both amphibian and fish hosts suggests either a broader second intermediate host range or more complex transmission pathways including paratenic host use, as has been demonstrated in other diplostomids.This study thus presents the first fully elucidated and molecularly characterised life cycle for a crocodilian-infecting diplostomid and advances our current understanding of host associations and transmission pathways within the Diplostomidae.