Two new species of Acanthocotyle Monticelli, 1888 (Monogenea: Acanthocotylidae), parasites of two deep-sea skates (Elasmobranchii: Rajiformes) in the South-East Pacific

Abstract

BackgroundParasites of deep-sea fishes from the South-East Pacific (SPO) are poorly known. Of c.1030 species of fish found in this area, 100–150 inhabit the deep-sea (deeper than 200 m). Only six articles concerning metazoan parasites of fish from deep-waters of SOP are known, and nine monogenean species have been reported. Currently, ten species are known in Acanthocotyle Monticelli, 1888 (Monogenea) and when stated, all of them are found in shallow waters (10–100 m). Acanthocotyle gurgesiella Ñacari, Sepulveda, Escribano & Oliva, 2018 is the only known species parasitizing deep-sea skates (350–450 m) in the SPO. The aim of this study was the description of two new species of Acanthocotyle from two Rajiformes.MethodsIn September 2017, we examined specimens of two species of deep-sea skates (Rajiformes), Amblyraja frerichsi (Krefft) and Bathyraja peruana McEachran & Myyake, caught at c.1500 m depth off Tocopilla, northern Chile, as a by-catch of the Patagonian tooth fish Dissostichus eleginoides Smitt fishery. Specimens of Acanthocotyle were collected from the skin of the skates. Morphometric (including multivariate analysis of proportional measurements, standardized by total length), morphological and molecular analyses (LSU rRNA and cox1 genes) were performed in order to identify the collected specimens.ResultsThe three approaches used in this study strongly suggest the presence of two new species in the genus Acanthocotyle: Acanthocotyle imo n. sp. and Acanthocotyle atacamensis n. sp. parasitizing the skin of the thickbody skate Amblyraja frerichsi and the Peruvian skate Bathyraja peruana, respectively. The main morphological differences from the closely related species Acanthocotyle verrilli Goto, 1899 include the number of radial rows of sclerites, the non-discrete vitelline follicles and the number of testes.ConclusionsThe two species of monogeneans described here are the only recorded parasites from their respective host species in the SPO. Assessing host specificity for members of Acanthocotyle requires clarifying the systematics of Rajiformes.

Parasitic flatworms infecting thorny skate,Amblyraja radiata:infection by the monogeneansAcanthocotyle verrilliandRajonchocotyle emarginatain Svalbard

“…PCA of A. verrilli (this study) and A. imo [49]. -hook, hp -haptor, rm -sucker rim, sb -sucker bulge, sp -sucker peduncle os -oral sucker.…”

“…The overall worldwide occurrence of Acanthocotyle spp. seems to follow the geographical distribution of their skate hosts as summarised in Ñacari et al [49]. Host-specificity ranges from one (9 species of Acanthocotyle) to five host species in A. lobianchi.…”

“…Based on the recent revision of Acanthocotylidae published by Kearn et al [32] combined with new species descriptions of Ñacari et al [49,50], there are 12 species of Acanthocotyle currently considered valid: Acanthocotyle atacamensis; Acanthocotyle elegans Monticelli, 1890; Acanthocotyle greeni Macdonald & Llewellyn, 1980; Acanthocotyle gurgesiella; Acanthocotyle imo ; Acanthocotyle lobianchi ; Acanthocotyle pacifica ; Acanthocotyle patagonica Kuznetsova, 1971; Acanthocotyle pugetensis ; Acanthocotyle urolophi ; Acanthocotyle verrilli ; Acanthocotyle williamsi Price, 1938. Acanthocotyle verrilli most closely resembles A. atacamensis, A. gurgesiella, A. imo and A. urolophi .…”

“…A) Principal component analysis (PCA) of A. verrilli (this study), A. atacamensis [49] and A. imo [49]. B) PCA of A. verrilli (this study) and A. atacamensis [49]. C) PCA of A. verrilli (this study) and A. imo [49].…”

“…B) PCA of A. verrilli (this study) and A. atacamensis [49]. C) PCA of A. verrilli (this study) and A. imo [49].…”