First modern morphological and molecular description of Saccocoelium cephali larvae stages (Digenea: Haploporidae) from the Black Sea

Abstract Purpose Knowledge of haploporid trematode larvae is very poor. Until recently, only scattered reports from Black and Medditeranean Seas are 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 Haploporidae family. Methods Hydrobia acuta molluscs were collected in the estuary of the Chernaya River ( 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 genetic 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 morphological characteristics of specimens investigated agree with those of Saccococoelium sp. and closest to S. cephali by shape and length of the body, ratio of suckers, ratio of tail length to body, shape and size of pharynx. Phylogenetic analysis from our study generated with Bayesian algorithm showed that studied cercariae specimens ex H. acuta from the Black Sea was within hapolporine clade and closely related with S. cephali from Spain. The process of encystation of 1 cercaria in same mollusc was observed (adolescaria).Cercariae and metacercariae have been described and named as Saccocoelium cephalibased on its morphological, morphometric and molecular characteristics. Conclusion Morphological characteristics of cercariae emerging from Hydrobia acuta from Black Sea, also the analysis of partial 28S rDNA sequences support conspecificity of parasite with S.cephali mature worms from Mediterranean Sea.