Progonus muelleri (Levinsen, 1881)

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 : 11-13

Progonus muelleri (Levinsen, 1881) ( Figs. 5A and 5B )

Type-host: Myoxocephalus scorpius (as Cottus scorpius ) ( Perciformes : Cottidae ), shorthorn sculpin [ 35].

Other hosts: Gadus macrocephalus (as Gadus ovak ) ( Gadiformes : Gadidae ), Greenland cod [ 35].

Type-locality: Aasiaat [Egedesminde], Greenland [ 35].

Site in host: Stomach.

Deposited examined material:

Whole mounts: Two specimens of P. muelleri ex Myoxocephalus scorpius from Aasiaat [Egedesminde], Greenland, deposited at the Natural History Museum of Denmark (SNM), Copenhagen, Denmark (NHMD-114950/ old catalogue number ZMUC-TRE-000032), Paralectotypes.

Transverse sections: T. Odhner’ s collections in the Invertebrates collection of the Swedish Museum of Natural History (SMNH), Stockholm, Sweden; two specimens ex Myoxocephalus scorpius from Spitsbergen , Svalbard, Norway , Arctic (SMNH 114584–114585) (identified and labeled by T. Odhner as P. muelleri ); One specimen from the same host and locality (SMNH 114587) (identified and labeled by T. Odhner as Genarches muelleri (Levinsen, 1881)) .

Longitudinal sections: T. Odhner’ s collections in the Invertebrates collection of the SMNH; one specimen ex

Abbreviations: CM, Central Mediterranean.

Myoxocephalus scorpius from Spitsbergen, Svalbard, Norway, Arctic (SMNH 114586) (identified and labeled by T. Odhner as P. muelleri ).

Additional material examined for comparison: Transverse sections: T. Odhner’ s collections in the Invertebrates collection of the SMNH: four specimens of D. varicus s. s. ex Limanda limanda from Gullmarsfjorden, Kristineberg, Sweden, NEA (SMNH 114554–114557) (identified and labeled by T. Odhner as D. varicus ).

Redescription: Body elongated, fusiform, rounded anteriorly ( Fig. 5A ). Tegument smooth, unarmed. Pre-oral lobe present. Oral sucker subterminal, small, rounded. Prepharynx not observed. Pharynx subglobular. Oesophagus not observed. Intestinal bifurcation in anterior third of forebody. Caeca wide, extending to and joining in anterior hindbody, forming cyclocoel, approximatively at level of testis. Ventral sucker subglobular, voluminous, clearly larger than oral sucker.

Genital pore a rounded pit, posterior to pharynx. Sinus sac oval to fusiform. Sinus-organ muscular, conical ( Fig. 5B ). Hermaphroditic duct thin walled. Seminal vesicle located in mid-forebody, saccular, fusiform. Pars prostatica short, lined with glandular cells. Testes two, oval, immediately posterior to ventral sucker.

Ovary globular, immediately post testicular. Uterus dorsal, extending to genital terminalia. Metraterm in midforebody, muscular. Eggs oval. Vitelline masses two, postovarian, subglobular. Excretory pore posterior, terminal. Excretory vesicle not detected. Excretory branches joining in forebody, dorsally to pharynx.

Remarks: The type-material received from Natural History Museum of Denmark (SNM), Copenhagen, Denmark includes nine specimens preserved in 70% ethanol from M. scorpius off Aasiaat [Egedesminde], Greenland, and were indicated as the Holotype. Two specimens were stained in acetocarmine, mounted on slides, and designated herein as Paralectotypes. Comparative terminal genitalia of D. varicus s. s. shown in Figure 5C .

Figures

Figure 5. Progonus muelleri (Levinsen, 1881) ex Myoxocephalus scorpius (NHMD-114950) and comparison between the terminal genitalia in Progonus and in Derogenes. A, P. muelleri ex M. scorpius (NHMD-114950), whole body. B, P. muelleri ex M. scorpius, terminal genitalia, horizontal section (SMNH-114586). C, Derogenes varicus sensu stricto ex Limanda limanda, terminal genitalia, horizontal section (SMNH- 114557).