New insights into two poorly known monogeneans (Platyhelminthes), gill parasites of the European barracuda Sphyraena sphyraena (Teleostei, Sphyraenidae) with notes on Chauhanea Ramalingam, 1953 and closely related genera

Abstract

Two poorly known parasitic Platyhelminthes were collected from the gills of the European barracuda Sphyraena sphyraena in the western Mediterranean. Specimens of Chauhanea mediterranea Euzet & Trilles, 1960 and Rhinecotyle crepitacula Euzet & Trilles, 1960 (Polyopisthocotyla) are redescribed based on newly collected material. A careful examination of Ch. mediterranea revealed inaccuracies in previous interpretations of the female openings. The midventral opening, previously referred to as the ‘vaginal opening’ in Pseudochauhanea Yamaguti, 1965 and used to distinguish this genus from Chauhanea Ramalingam, 1953, is demonstrated to be the uterus, as confirmed by the presence of eggs in the thin-walled duct associated with this opening. The lateral position of the cirrus and vagina is also confirmed. Consequently, Pseudochauhanea is synonymized with Chauhanea, resulting in the following new combinations: Ch. elegans Fuentes-Zambrano, 1997 n. comb.; Ch. elongata Kritsky, Bilqees & Leiby, 1972 n. comb.; Ch. macrorchis Lin, Liu & Zhang in Zhang, Yang & Liu, 2001 n. comb.; Ch. mexicana Lamothe, 1967 n. comb.; Ch. sphyraenae Yamaguti, 1965 n. comb. A detailed investigation of the clamp sclerites of Ch. mediterranea indicates that both Chauhanea and Cotyloatlantica Bravo-Hollis, 1984 share the subdivision of the basal oblique sclerite, which is a continuation of the marginal sclerite in the anterior jaw, a key feature used to distinguish these genera. As a result, Cotyloatlantica is also synonymized with Chauhanea, and its species are transferred as follows: Ch. pretiosa (Bravo-Hollis, 1984) n. comb. The reinstatement of Ch. mediterranea Euzet & Trilles, 1960 as a valid name is supported, and an amended diagnosis of Chauhanea is provided. Additionally, R. crepitacula is accurately redescribed, with a new geographical locality record and an assessment of morphometrical and anatomical variations between Mediterranean and oceanic specimens.Systematics and integrative taxonomy of Monogenea parasitizing fishes of Swede