Multifaceted taxonomy of two Dactylogyrus species on Enteromius paludinosus: Integrating light microscopy, scanning electron microscopy and molecular approaches.

Abstract

Dactylogyrus Diesing, 1850 is the most speciose genus of platyhelminths with more than 900 species, and over a hundred species recorded from Africa. Of the latter, six are from the straightfin barb, Enteromius paludinosus (Peters). Dactylogyrus teresae Mashego, 1983 and Dactylogyrus dominici Mashego, 1983 were collected from E. paludinosus in the Vaal River system, Gauteng, South Africa and their taxonomic data revised using standard protocols and modern approaches, alongside the type material. Whole worms were mounted on glass slides with glycerine ammonium picrate (GAP) and studied using light microscopy (LM). For scanning electron microscopy (SEM), whole worms were placed on concavity slides and the soft tissue digested to release the sclerotised copulatory organs and haptoral sclerites. A combination of these approaches (LM and SEM) was employed for the first time to study the sclerotised structures of GAP-mounted material. Soft tissues of SEM analysed specimens were genetically characterised using CO1 mtDNA, 18S-ITS1-5.8S rDNA and partial 28S rDNA fragments. Phylogenetic topologies were constructed using Bayesian inference. Results confirmed the morphologic and genetic distinctness of D. dominici and D. teresae, highlighting the importance of studying the varying orientations of specifically the vagina and transverse bar. This study presents a new locality record, the first SEM study of isolated sclerotised structures, as well as the first molecular data for the Dactylogyrus afrobarbae-like species. The multifaceted approaches applied to the same specimen in this study enabled improved resolution of individual specimens, showing promise for studies where limited specimens are available.