First Modern Morphological and Molecular Description of Saccocoelium Cephali Larvae Stages (Digenea: Haploporidae) from the Black Sea.

Purpose: Knowledge of haploporid trematode larvae is very poor. Until recently, only scattered reports from the Black and Medditeranean Seas were known. The present research is the first report of haploporid cercariae S. cephali from the gastropod Hydrobia acuta inhabiting the Black Sea. Thus, the present study aimed to investigate the larvae of one species from the Haploporidae family.

Methods: Hydrobia acuta molluscs were collected in the estuary of the Chernaya River (the Black Sea) during 2011-2013 and examined for trematode larvae. Found parthenitae were drawn and preserved for DNA extractions. Morphological features were compared to nominal species, and molecular comparisons were made of the subunit ribosomal DNA with other Haploporidae species.

Results: The haploporid parthenitae were found in the gonads of Hydrobia acuta molluscs. Most of the morphological characteristics of the specimens investigated agree with those of Saccococoelium sp. and are closest to those of S. cephali by shape and length of the body, ratio of suckers, ratio of tail length to body, shape, and size of the pharynx. Phylogenetic analysis from our study generated with Bayesian algorithm showed that studied cercariae specimens from the Black Sea were within the hapolporine clade and closely related to S. cephali from Spain.

Conclusion: Morphological characteristics of cercariae emerging from Hydrobia acuta from the Black Sea and the analysis of partial 28S rDNA sequences support the conspecificity of the parasite with S. cephali mature worms from the Mediterranean Sea.