Orchestia forchuensis Myers & Lowry 2020, sp. nov.

• Main Authors: Myers, Alan A., Lowry, James K.
• Format: Text
• Language: unknown
• Published: Zenodo 2020
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Malacostraca; Amphipoda; Talitridae; Orchestia; Orchestia forchuensis; Reykjavík; Canada; Reykjanes; Myers; Seta; Steele; Lowry; Perez; Seal Islands; Vestmannaeyjar; McAllister; Mutton; Trepassey; Kópavogur; Seal Rock; Gooseberry Cove; Mutton Bay; Seal Bay; Hvassahraun; Nauthólsvík; Kaldrananes; Iceland; Newfoundland; North Atlantic
• Online Access: https://dx.doi.org/10.5281/zenodo.4331229; https://zenodo.org/record/4331229

Orchestia forchuensis sp. nov. (Figs 12–14) Orchestia gammarella .― Bousfield, 1958: 885, figs 1e, 10a.― Bousfield, 1973: 159, pl. 45.1. Orchestia gammarellus .― Ingólfsson, 1996: 39, fig. 10.― Henzler & Ingólfsson, 2007: 1. Not Orchestia gammarellus (Pallas, 1776): 191, pl. 14, fig. 25. Types. Holotype, male, 12.0 mm (CNMC 1984-462), Cape Fourchou, Yarmouth County, Nova Scotia, 5 July,1956, E.L. Bousfield. Paratypes. 4 males, 8 females (CNMC 1984-462), same data as holotype. Other material studied. 3 females, 25 juveniles (CNMC 1984-472), 3 miles west of Le Cou Harbour, southwestern Newfoundland (47 o 38'N58 o 41'W), 8 June 1966, D.E. McAllister; 2 males, 5 females (CNMC 1984-465) Gilbert Point, Digby County, Nova Scotia, E.L. Bousfield, 9 July 1958; 3 males, 5 females, 2 juveniles, (CNMC 1984-460), above Murphy's river, Salmonier Estuary, Newfoundland, 15 August, 1954, E.L. Bousfield; 7 males, 11 females, Nauthólsvík, between Kópavogur (pubby seal bay) and Reykjavík, Iceland (64.117714 oN 21.900876 oW), September 2019, Davíð Gíslason; 9 males, 10 females, salt-marsh, under stones in the saltmarsh grass Puccinella maritima beds Galgahavn, Iceland (64.0549 oN 21.5728 oW), 23 September 2019, Jorundur Svavarsson. Type locality. Cape Fourchu, Nova Scotia. Etymology. Named after the type locality. Description of adult male (15 mm). Head. Eyes of moderate size. Antenna 1 short, just reaching beyond peduncular article 4 of antenna 2; accessory flagellum absent; primary flagellum with 5 articles. Antenna 2 peduncular article 5, 1.3 × length of peduncular article 4; flagellum longer than combined length of peduncular articles 4 and 5, with 19-20 articles, final article cone shaped, with terminal cluster of imbricated setae. Labrum without epistome. Mandible left lacinia mobilis with 4 cusps. Maxilliped palp article 2 with distomedial lobe. Pereon. Gnathopod 1 subchelate, coxa smaller than that of coxa 2; posterior margin of carpus and propodus each with lobe covered in palmate setae; propodus length to carpus length 1:1.6; propodus strongly triangular; dactylus shorter than palm. Gnathopod 2 subchelate; basis 2.3 × as long as broad; merus posterior margin with 3-5 short setae; propodus weakly triangular, distal width 1.7 × proximal width. Pereopods 3–7 bicuspidactylate, cusps sometimes becoming lost in large males. Pereopods 3–4 dactylus unguis relatively slender, acute, becoming short and blunt on pereopod 7 in large males Peropod 4 dactylus thickened proximally with a notch midway along posterior margin. Pereopod 5 basis subovoid. Pereopod 7 basis posterior margin distinctly serrate; merus elongate, weakly triangular, becoming 2 × as wide distally as proximally in large males; carpus elongate pyriform, 1.5 – 2 × as long as broad carpus subequal to merus in small males, becoming 1.5 × longer in large males; propodus 1.2 × length of carpus. Pleon. Epimeron 3 posterior margin weakly crenulate. Uropod 1 peduncle longer than rami, without distolateral robust seta; rami subequal. Uropod 2 peduncle subequal in length with rami, rami subequal; exopod with 2 marginal robust setae; endopod with 3 marginal robust setae and 2 robust setae on inner face. Uropod 3 peduncle only a little longer than broad; ramus 2.3 × as long as broad 0.6 × length of peduncle, outer margin with 6 robust setae. Telson with about 9 apical robust setae on each side. Female (sexually dimorphic characters). Gnathopod 2 mitten-shaped; basis 2 × as long as broad, broadest proximally, anterodistal margin substraight; carpus 1.4 × length of propodus. Pereopod 7 stout, basis posterior margin weakly serrate, merus and carpus unexpanded. Habitat. Limestone, gravel and pebble beaches; marshes among the saltmarsh grass Puccinella maritima . Remarks. Orchestia forchuensis sp. nov. is close to O. gammarellus (Pallas, 1776) but can be distinguished by the shape of the adult male pereopod 7 that has the merus almost parallel-sided, only about twice as broad distally as proximally in O. forchuensis sp. nov. (strongly triangular, almost three times as broad distally as proximally in O. gammarellus ) and the carpus much longer than broad (almost as broad as long in O. gammarellus ). The basis of pereopod 5 has a weakly developed posterodistal lobe in O. fouchouensis sp. nov. (well-developed in O. gammarellus ) and the basis of the female pereopod 7 of Orchestia forchuensis sp. nov. is subovoid (approaches subquadranglar in O. gammarellus) . That the North American populations of ' Orchestia gammarellus' were probably a previously unrecognised species, was first pointed out by Perez-Schultheiss (2014, p. 30). Distribution. Canada Newfoundland: Campell's Creek Cove, Port-au-Port peninsula; Little Bay, near Springfield; Exploits estuary; Philip's Head; Placentia; Salmonier estuary; Trepassey, head of Mutton Bay; Fox Cove (Bousfield 1955); above Murphy's river, Salmonier Estuary (present study); Gooseberry Cove (47°03.3'N54°05.7'W), Kingwell Arm (47°33.5'N 54°06.O'W),Dirty Rocks (47°23.7'N54°16.1'W),Margery Cove (47°24.5'N54°09.0'W) (Fenwick & Steele 1983), Cou Harbour, south-western Newfoundland (47 o 38'N58 o 41'W) (present study). Nova Scotia . Machias Seal Rock; St. Andrews; Argyle (Bousfield 1955). Gilbert Point, Digby County, Nova Scotia (present study). New Brunswick . Bay of Fundy (Bousfield 1960); Tidal Cove; Machais Seal Islands (Bousfield 1958). USA (New England); coast of Maine to Casco Bay (Bousfield 1973). Iceland . Extreme southwest, from the Vestmannaeyjar Islands to Reykjavíc and the northwest peninsula area associated with warm springs; Hvassahraun (64°01'11''N22°09'19''W) Reykjanestjörn (63°47'52''N 22°43'912''W), Hveravik, Steingrimsfjördur (65°41'47''N21°33'55''W); Bjarnarstadir, Isafjördur (65°49'16''N 22°2'919''W) and Reykjanes, Reykjafjördur (65°55'25''N22°25'53''W); Kaldrananes (65°46'N21°24'W) and Skarð (65°29'N20°59'W) (Ingólfsson 1973, 1977, Morritt & Ingólfsson 2000, Ingólfsson et al . 2007, Henzler & Ingólfsson 2007). : Published as part of Myers, Alan A. & Lowry, James K., 2020, A revision of the genus Orchestia Leach, 1814 with the reinstatement of O. inaequalipes (K. H. 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