Molecular circumscription of new species of Gyrocotyle Diesing, 1850 (Cestoda) from deep-sea chimaeriform holocephalans in the North Atlantic Author Bray, Rodney A. Division of Parasites and Vectors, Department of Life Sciences, Natural History Museum, London SW 7 5 BD, UK Author Waeschenbach, Andrea Division of Parasites and Vectors, Department of Life Sciences, Natural History Museum, London SW 7 5 BD, UK Author Littlewood, D. Timothy J. Division of Parasites and Vectors, Department of Life Sciences, Natural History Museum, London SW 7 5 BD, UK Author Halvorsen, Odd Natural History Museum, University of Oslo, P. O. Box 1172, Blindern, 0318 Oslo, Norway Author Olson, Peter D. Division of Parasites and Vectors, Department of Life Sciences, Natural History Museum, London SW 7 5 BD, UK P.Olson@nhm.ac.uk text Systematic Parasitology 2020 2020-04-23 97 285 296 journal article https://doi.org/10.1007/s11230-020-09912-w 950d0ca1-62a2-4f36-898d-6dca2c5b90cf 4623814 86FBE97B-A44F-48E5-8600-294119A7F304 Gyrocotyle haffii n. sp. Type-host : Harriotta raleighana Goode & Bean ( Chimaeriformes : Rhinochimaeridae ), bent-nosed chimaera. Type-locality : Goban Spur ( 49°46 0 N , 12°21 0 W , depth 1,631–1,653 m , 22-23.iv.2001 ; RRS Discovery Cruise 252, No. 13951/14), North-East Atlantic. Type-material : Holotype ( NHMUK . 2019.11.21.1 ), paratype ( NHMUK . 2019.11.21.2 ) . Site in host : Spiral intestine. Representative DNA sequences: MN655880 ( ssrDNA ); MN657006 ( lsrDNA , domains D1-D3). ZooBank registration : The Life Science Identifier (LSID) for Gyrocotyle haffii n. sp. is urn:lsid:- zoobank.org:act:7717F9D6-4C9D-4C59-8D0A- 4C5E306B4671. Etymology: The species is named in honour of our late colleague and friend Professor Harford ‘Haffi 0 Williams in recognition of his contribution to the understanding of the Gyrocotylidea . Description [Based on a single intact, immature whole worm and second immature worm from which the central portion had been excised for molecular analysis; Figs. 2, 3]. With characters of the order. Body elongate with minute annular ridges; no large lateral flap. Length 23,504; greatest width near anterior extremity, 3,131. Rosette relatively small with few crenulations, 1,943 long. Anterior sucker large, oval, 1,750 X 1,223. Reproductive system immature; anlagen commences 2,852 from anterior extremity, 8,191 long; consisting of a long, narrow patch of stained tissue reaching, and a branched section passing, towards lateral margin of worm; apparently opening at c. 268 from anterior extremity. Only other evidence of reproductive organs is putative vitelline glands scattered around posterior extremity of anlagen. Diagnosis Gyrocotyle haffii n. sp. can be diagnosed from other congeners on the basis of unique nucleotide characters in our rDNA alignments (listed as alignment positionnucleotide): ssrDNA : 218-T, 723-A, 746-C, 747-A, 748-G, 1,158-T, 1,654-G, 1,673-C, 2,115-C; lsrDNA : 612-T, 837-A, 875-T, 1,306-A, 1,395-C, 1,402-A, 1,501-G. Remarks As far as we are aware there is only one previous report of a gyrocotylidean from Ha. raleighana , the bentnose chimaera. Parukhin (1966) reported ‘‘ Gyrocotyloides nybelini Fuhrmann, 1931 ’’ in this host from the South Atlantic Ocean. Parukhin (1968) repeated this report saying (in translation) ‘‘Found in Callorhynchus capensis . Two adult parasites were found in two fish. In addition, six larvae were found in one of them. In addition to C. capensis , specimens were found in two Hariota [sic] raleighana . In both cases there were two specimens. Previously, this species was observed in the Atlantic in Chimaera monstrosa ’’. In addition, it seems likely that the records of ‘cestode adults 0 from Ha. raleighana , Hy. mirabilis and C. monstrosa from the Rockall Trough off NW Scotland by Mauchline & Gordon (1984) refer to Gyrocotyle spp. There is no reliable morphological character to differentiate this species or indeed any of the gyrocotylidean species circumscribed by molecular means. Therefore, the species is diagnosed by its relatively marked sequence divergence from those of recognised species.