Phylogenetic Evidence for the Lissorchiid Concept of the Genus Anarhichotrema Shimazu, 1973 (Trematoda, Digenea)

Sergey G Sokolov,Sergei V Shchenkov,Ilya I Gordeev

doi:10.3390/d14020147

Abstract

Anarhichotrema Shimazu, 1973 is a monotypic digenean genus, with the type- and only species, Anarhichotrema ochotense Shimazu, 1973, known to infect North Pacific fishes. This genus was originally described as a member of the Lissorchiidae (Monorchioidea) and later moved to the Zoogonidae (Microphalloidea). Its exact phylogenetic position has remained unresolved due to the lack of molecular data. In this study, we isolated specimens of A. ochotense from the Bering wolffish, Anarhichas orientalis Pallas, 1814 caught in the Sea of Okhotsk, described them morphologically and performed a molecular phylogenetic analysis of their nuclear 18S and 28S rDNA regions. The specimens examined in our study generally corresponded to previous morphological descriptions of A. ochotense but were noticeably smaller, possibly due to the crowding effect. The phylogenetic analysis placed Anarhichotrema within the Lissorchiidae as a sister taxon to the group comprising freshwater lissorchiids. Thus, we restore Anarhichotrema to the Lissorchiidae, as originally assigned.

Highlights

Anarhichotrema Shimazu, 1973 is a monotypic digenean genus erected by Shimazu [1]
Maximum likelihood and Bayesian Inference analyses based on 28S rRNA gene data placed A. ochotense within the Monorchioidea, sister to the well-supported ‘freshwater lissorchiids’ clade; the position of A. ochotense was poorly-supported (Figure 1)
The specimens of A. ochotense described in our study are similar to those from Shimazu [1] in most of the morphological features related to the shape and location of the organs

Summary

Introduction

Anarhichotrema Shimazu, 1973 is a monotypic digenean genus erected by Shimazu [1]for A. ochotense Shimazu, 1973 described from the Bering wolffish Anarhichas orientalisPallas, 1814 (Anarhichadidae) caught in the Sea of Okhotsk. Anarhichotrema Shimazu, 1973 is a monotypic digenean genus erected by Shimazu [1]. For A. ochotense Shimazu, 1973 described from the Bering wolffish Anarhichas orientalis. 1814 (Anarhichadidae) caught in the Sea of Okhotsk. Twelve years later Machida [2]. Described the genus Neolissorchis Machida, 1985 with the type and only species Neolissorchis genge Machida, 1985 from the intestine of Zoarcid fish Lycodes sp. Machida [2] was apparently unaware of the publication by Shimazu [1] since he did not mention A. ochotense in his work. The two species had extremely similar morphology. Thereafter, Bray [3] reasonably synonymised Neolissorchis with Anarhichotrema and N. genge with A. ochotense. Later Kuramochi [4] found A. ochotense in a Zoarcid fish

Methods

Results

Conclusion