Derogenes abba, Bouguerche & Huston & Karlsbakk & Ahmed & Holovachov, 2024

Bouguerche, Chahinez, Huston, Daniel C., Karlsbakk, Egil, Ahmed, Mohammed & Holovachov, Oleksandr, 2024, Untangling the Derogenes varicus species complex in Scandinavian waters and the Arctic: description of Derogenes abba n. sp. (Trematoda, Derogenidae) from Hippoglossoides platessoides and new host records for D. varicus (Müller, 1784) sensu stricto, Parasite (Paris, France) 31 (26), pp. 1-25 : 6

Derogenes abba n. sp. ( Figs. 1A–1C )

urn:lsid:zoobank.org:act:7CB281BD-05E0-4BAF-A717-A1E4E1477AE1

Synonyms: Derogenes varicus DV 2 of Krupenko et al. [ 30]; D. varicus of Olson et al. [ 50].

Type-host: Hippoglossoides platessoides ( Pleuronectiformes : Pleuronectidae ), American plaice.

Type-locality: Svalbard, Norway, Arctic Ocean , at 79 59.860558 N, 15 27.879328 E, and 170 m depth .

Other hosts: Invertebrate hosts, first intermediate hosts: Amauropsis islandica ( Naticidae ), Iceland moonsnail; Euspira pallida ( Naticidae ), Pale moonsnail; Buccinum scalariforme ( Buccinidae ), ladder whelk (definitive host).

Other localities: United Kingdom, North Sea [ 50]. Keret Archipelago, White Sea. Dalniye Zelentsy, Barents Sea [ 30].

Site in host: Stomach.

Deposited examined material: Holotype (SMNHType-9562), 11 paratypes (SMNH- Type-9563–9573), and 2 paratypes with molecular information (hologenophores) (SMNH- Type-9563–9564) deposited in the Type collections of the Swedish Museum of Natural History (SMNH), Stockholm, Sweden. One paratype (TSZY-519) deposited in the collections of The Arctic University Museum of Norway (UiT), Tromsø, Norway.

Paratypes with molecular information: anterior parts of specimens mounted on a slide, posterior part used for molecular analysis: slide SMNH- Type-9563; slide SMNH- Type-9564.

Representative DNA sequences: Partial 28S, two sequences (GenBank, PP314018–PP314019); ITS2, two sequences (GenBank, PP314020, PP314022); Partial cox 1, two sequences (GenBank PP384389–PP384390).

Additional material examined for comparison: Whole mounts: (1) Eighteen specimens of D. varicus s. s. ex Salmo salar, Bremanger , Norway, Northeast Atlantic (SMNH 218683–218700). (2). Ten specimens of D. varicus s. s. ex Gadus morhua from Svalbard, Norway, Arctic (TSZY-520– 529). (3). Derogenes varicus s. l. from the collection of T. Odhner in the Invertebrates collection of the Swedish Museum of Natural History (SMNH): one specimen ex Limanda limanda from Gullmarsfjorden, Kristineberg, Sweden, NEA (SMNH-114551); one specimen ex Argentina sphyraena from Trondheim, Norway, NEA (SMNH-114558); one specimen ex Molva molva Trondheim , Norway, NEA (SMNH-114559); one specimen ex Brosme brosme from Trondheim, Norway, NEA (SMNH-114560); three specimens ex Hippoglossus hippoglossus from Trondheim, Norway, NEA (SMNH-104577); five specimens ex Platichthys flesus from Gullmarsfjorden, Kristineberg, Sweden, NEA (SMNH-208360).

Etymology: Named after ABBA, the Swedish pop supergroup renowned for hits like “ Dancing Queen ”, “ Chiquitita ” and “ Money, Money, Money ” which served as a source of entertainment for the first author during the creation of the illustrations. The group’ s name is an acronym of the first letters of their first names arranged as a palindrome. Invariable, treated as a noun in apposition.

Description: Measurements and comparisons in Tables 3–5 . Body stocky ( Figs. 1A and 1B ), nearly sausage-shaped; anterior and posterior ends rounded. Pre-oral lobe short. Oral sucker rounded. Pre-pharynx absent. Pharynx muscular. Oesophagus short. Intestines bifurcating anterior to sinus-organ. Intestinal caeca extending posteriorly to vitelline masses and terminating blindly. Ventral sucker rounded.

Male terminal genitalia in forebody. Sinus-sac oval to pyriform ( Figs. 1B and 1C ). Cone-shaped permanent muscular sinus-organ projecting into genital atrium. Ejaculatory duct and metraterm projecting into sinus-organ. Hermaphroditic duct thin-walled. Pars prostatica relatively short, lined by gland cells, leading to seminal vesicle. Seminal vesicle voluminous, oval, and thin-walled, situated in mid-forebody at considerable distance from ventral sucker. Testes oval to globular, symmetrical, posterior to ventral sucker.

Ovary globular, voluminous, post-testicular, sometimes overlapped by right vitelline mass. Laurer’ s canal not observed. Vitelline masses in hindbody, round to oval, paired, situated on each side of body. Vitelline ducts fuse antero-medial to ovary. Seminal receptacle not observed. Uterus convoluted, uterine coils extending from near posterior extremity to sinus sac. Eggs oval. Excretory vesicle Y-shaped; branches reuniting dorsal to pharynx.

The morphology of the cercaria was described by Krupenko et al. [ 30].

Figures

Figure 1. Derogenes abba n. sp. ex Hippoglossoides platessoides. A, whole body (Type-9562). B, terminal genitalia (Type-9562). C, hologenophore, forebody (Type-9563).