Investigating the presence of cryptic species in diplostomatid trematodes

Diplostomatid trematodes belong to a large group of parasitic flatworms that infect humans and animals. The lack of defining features and complexity of the trematode life cycle pose barriers to distinguishing cryptic species of trematodes, which appear to be related but are genetically distinct. Genetic signatures were used to group putative species of cercariae (a larval stage of diplostomatid trematodes), and morphological data were analyzed to determine if physical features could distinguish these species from one another, with potential diagnostic features being tail stem length and total length. DNA sequences indicated the presence of seven distinct species, and limited morphological variation between species suggested they are truly cryptic.