taxonID	type	description	language	source
03E316070048FFAD72A1FC0B4566A3D9.taxon	discussion	The ‘ normani - group’ within Onisimus is characterized by a partly cleft telson, a completely constricted uropod 2, and a peculiar 1 st epimeral plate, with an anterodistal hook (Vader et al. 2005). The group consists of O. normani, O. turgidus, and 2 or 3 taxa closely related to O. turgidus, but strongly deviating in the arrangement of the setal teeth on the outer plate of maxilla 1. Material belonging to these taxa has been found in the W Atlantic Ocean, near Greenland and in the NW Pacific (Johnsen 2001). Most (or possibly all) species in this group appear to be obligate associates of sea anemones, a trait absent in all other Onisimus species. In Norwegian waters there are two species in this group, O. normani in W Norway north to Andfjorden, and O. turgidus in N Norway and the Barents Sea. They can be distinguished as follows:	en	Vader, Wim, Johnsen, Jan Roger, Tandberg, Anne Helene S. (2020): Onisimus turgidus (Sars, 1879) (Amphipoda, Uristidae), an overlooked amphipod from sea anemones in Northern Norway. European Journal of Taxonomy 724: 34-50, DOI: 10.5852/ejt.2020.724.1155
03E316070048FFA9707AFA7844B6A50E.taxon	description	Figs 1 – 3	en	Vader, Wim, Johnsen, Jan Roger, Tandberg, Anne Helene S. (2020): Onisimus turgidus (Sars, 1879) (Amphipoda, Uristidae), an overlooked amphipod from sea anemones in Northern Norway. European Journal of Taxonomy 724: 34-50, DOI: 10.5852/ejt.2020.724.1155
03E316070048FFA9707AFA7844B6A50E.taxon	materials_examined	Material examined NORWAY • 1 ♀ (10 mm); Korsfjorden; 680 m depth; 1968; Wim Vader leg.; from Bolocera tuediae; TSZCr 8659 (Figs 1 – 3) • 1 ♀ immature (8 mm); same collection data as for preceding; TSZCr 8659 • 1 spec.; Raunefjorden; 240 m depth; 1968; Wim Vader leg.; from Bolocera tuediae; TSZCr 8628 • 1 spec.; Korsfjorden; 680 m depth; 1968; Wim Vader leg.; from Bolocera tuediae; TSZCr 8623 • 1 spec.; same collection data as for preceding; TSZCr 8624 • 2 specs; same collection data as for preceding; TSZCr 9320 • 7 specs; Andfjorden; 69 ° 18 ′ 42 ″ N, 16 ° 23 ′ 24 ″ E; 498 m depth; 1 Jul. 1997; Wim Vader leg.; from Bolocera tuediae; TSZCr 12962	en	Vader, Wim, Johnsen, Jan Roger, Tandberg, Anne Helene S. (2020): Onisimus turgidus (Sars, 1879) (Amphipoda, Uristidae), an overlooked amphipod from sea anemones in Northern Norway. European Journal of Taxonomy 724: 34-50, DOI: 10.5852/ejt.2020.724.1155
03E316070048FFA9707AFA7844B6A50E.taxon	distribution	Distribution Although there are many records of O. normani in the amphipod literature, all except those from Southern Norway in reality are either O. turgidus or taxa very closely related to that species (Johnsen 2001). Johnsen mentions a record from Andsfjorden at 69 ° N (material in Tromsø Museum): otherwise this species has only been recorded from the Oslofjord and a number of localities in W Norway (Vader 1967). Onisimus normani appears to be an obligate associate of the sea anemone Bolocera tuediae, and it has only exceptionally been found in other sea anemones (Vader 1967, 1975), although it is well able to survive also in other sea anemone hosts in the laboratory (Vader & Lønning 1973).	en	Vader, Wim, Johnsen, Jan Roger, Tandberg, Anne Helene S. (2020): Onisimus turgidus (Sars, 1879) (Amphipoda, Uristidae), an overlooked amphipod from sea anemones in Northern Norway. European Journal of Taxonomy 724: 34-50, DOI: 10.5852/ejt.2020.724.1155
03E31607004CFFA17042FC20447AA519.taxon	description	Figs 4 – 10	en	Vader, Wim, Johnsen, Jan Roger, Tandberg, Anne Helene S. (2020): Onisimus turgidus (Sars, 1879) (Amphipoda, Uristidae), an overlooked amphipod from sea anemones in Northern Norway. European Journal of Taxonomy 724: 34-50, DOI: 10.5852/ejt.2020.724.1155
03E31607004CFFA17042FC20447AA519.taxon	materials_examined	Material examined NORWAY • 1 ♀, syntype (15 mm); Barents Sea; 72 ° 53 ′ N, 21 ° 51 ′ E; 408 m depth; 30 Jul. 1878; G. O. Sars leg.; stn 323 (trawl), Norwegian North sea Expedition; 1.5 ° C; silt.; F 1764 (Figs 4 – 6) • 1 ♀ (10 mm); Kuberget Ullsfjorden; 100 m depth; Sep. 1974; Wim Vader leg.; from Actinostola callosa; TSZCr 8573. (Figs 7 – 10) • 1 spec.; Ullsfjorden; from Actinostola callosa; TM IX- 95 • 2 specs; Ullsfjorden; 69 ° 39 ′ 48 ″ N, 19 ° 45 ′ 18 ″ E; 106 m depth; 28 Apr. 1995; Wim Vader leg.; from Actinostola callosa; stn JohanRuud 255 - 95; TSZCr 14488 • 21 specs; Ullsfjorden; Jun. 1995; Wim Vader leg.; from Actinostola callosa; stn Hyas 6 - 95; Arctic University Museum of Tromsø • 1 spec., Finnkroken; 50 – 60 fathoms depth; 1900; J. Sparre Schneider leg.; TSZCr 1171.	en	Vader, Wim, Johnsen, Jan Roger, Tandberg, Anne Helene S. (2020): Onisimus turgidus (Sars, 1879) (Amphipoda, Uristidae), an overlooked amphipod from sea anemones in Northern Norway. European Journal of Taxonomy 724: 34-50, DOI: 10.5852/ejt.2020.724.1155
03E31607004CFFA17042FC20447AA519.taxon	distribution	Distribution Johnsen (2001) studied samples of presumed Onisimus normani from different parts of the world, and concluded that they all (except the ones from S Norway) belonged in the turgidus species complex; unfortunately there was not sufficient material available to be able to revise this entire complex. The type material was collected from the Barents Sea and it has been collected from this area several times since (Bryazgin 1997; Lyubina et al. 2014, sub nomine O. normani; Zimina et al. 2019). Material from N Norway (Ullsfjorden) is quite similar to the type material, but the animals are smaller, 10 mm against 14 mm for the type. No fully adult or ovigerous specimens of O. turgidus have been found as yet, similar to the situation in O. normani. Onisimus turgidus also spends most of its life inside a sea anemone and like O. normani, likely leaves the host when almost adult.	en	Vader, Wim, Johnsen, Jan Roger, Tandberg, Anne Helene S. (2020): Onisimus turgidus (Sars, 1879) (Amphipoda, Uristidae), an overlooked amphipod from sea anemones in Northern Norway. European Journal of Taxonomy 724: 34-50, DOI: 10.5852/ejt.2020.724.1155
03E31607004CFFA17042FC20447AA519.taxon	biology_ecology	Biology Onisimus turgidus appears to be an obligate associate of sea anemones for most of its life-cycle. The preferred host of Onisimus turgidus in N Norway is Actinostola callosa. The numbers vary quite a lot from year to year (Moore et al. 1994; Vader & Krapp-Schickel 1996: table 2, sub nom. O. normani) but the species is never numerous even there: in 714 specimens of Actinostola Verrill, 1883 from Ullsfjorden 116 specimens of O. turgidus were found, an infection percentage of 0.16 amphipods per host. There is a significant positive correlation between the size of the Actinostola hosts and the number of Onisimus found inside: in the large sample of January 1974 sea anemones of 10 – 50 g wet weight contained 0.03 amphipods per host, those of 60 – 100 g 0.54 and the few of 100 – 150 g 3.00. Actinostola callosa in Ullsfjorden also is the host of another amphipod species, Stenothoe brevicornis Sars, 1883, that likewise feeds on host tissue, but this amphipod lives on the outside of the host, among the tentacles (Moore et al. 1994; Vader & Krapp-Schickel 1996). Onisimus turgidus in Ullsfjorden is also sometimes found inside Bolocera tuediae, the almost exclusive host of O. normani in S Norway (Vader 1973), but here it is even less common than in A. callosa: in 297 specimens of Bolocera Gosse, 1860 from Ullsfjorden only 14 specimens of Onisimus were found (0.05 amphipods per host). The parasitic isopod Parapodascon sp. that is quite common on O. normani in S Norway, has also been found a few times on O. turgidus from the Ullsfjord.	en	Vader, Wim, Johnsen, Jan Roger, Tandberg, Anne Helene S. (2020): Onisimus turgidus (Sars, 1879) (Amphipoda, Uristidae), an overlooked amphipod from sea anemones in Northern Norway. European Journal of Taxonomy 724: 34-50, DOI: 10.5852/ejt.2020.724.1155
