Pontocrates arcticus Sars, 1895

Myers, Alan A. & Ashelby, Christopher W., 2022, A revision of the genus Pontocrates Boeck, 1871 (Amphipoda, Oedicerotidae) with the description of P. moorei sp. nov. and the re-establishment of P. norvegicus (Boeck, 1860), Zootaxa 5115 (4), pp. 582-598 : 583-586

Pontocrates arcticus Sars, 1895

( Fig. 1 , 2 )

Pontocrates arcticus Sars, 1895 , 693.—? Raitt, 1938, 10,11.— Gurjanova, 1951, 525, fig. 343.

Pontocrates norvegicus Schneider, 1883 , 17, pl. 2, fig. 15, pl. 3, figs 21–22.— Schneider, 1885a, 13, pl. 1, figs 1–18.— Sars, 1892, 315, pl. 111, fig. 2.

Not Pontocrates norvegicus Boeck, 1871 , 171.

Type material. Syntypes (11 animals), Hasvig , West Finmark (UiO F14210)

Material studied. 1 male North Sea , UKCS 16 /29a, 57°57’36.00”N 001°48’57.60”E; 88 m depth; Muddy Sand; leg. Gardline, 16/10/2018 . 1 female North Sea , UKCS 16 /29a, 57°57’36.00”N 001°48’57.60”E; 88 m depth; Muddy Sand; leg. Gardline, 16/10/2018 . 1 male, 1 female North Sea , UKCS 22 /11, 57°39’46.40”N 001°08’44.00”E; 83.4 m depth; Sand; leg. Fugro, 04/01/2014 . 1 male North Sea , UKCS 16 /29a, 57°57’36.00”N 001°48’57.60”E; 88 m depth; Muddy Sand; leg. Gardline, 17/10/2018 . 2 females Belfast Lough , 54°43’59.88”N 005°35’60.00”W; 32 m depth; Sand; leg. DAERA, 10/03/2016 . 1 female Belfast Lough , 54°43’59.88”N 005°35’60.00”W; 32 m depth; Sand; leg. DAERA, 10/03/2016 . 3 females, Belfast Lough , 54°43’59.88”N 005°35’60.00”W; 32 m depth; Sand; leg. DAERA, 10/03/2016 . 1 female. Belfast Lough , 54°43’28.20”N 005°34’03.00”W; 34 m depth; Sand and Shell; leg. DAERA, 22/06/2016 . 2 females, Belfast Lough , 54°43’59.88”N 005°35’60.00”W; 32 m depth; Sand; leg. DAERA, 05/03/2013 . 1 male, 1 female, Belfast Lough , 54°43’59.88”N 005°35’60.00”W; 32 m depth; Sand; leg. DAERA, 10/03/2016 . 1 female, Belfast Lough , 54°43’59.88”N 005°35’60.00”W; 32 m depth; Sand; leg. DAERA, 08/03/2018 . 2 females, Belfast Lough , 54°43’59.88”N 005°35’60.00”W; 32 m depth; Sand; leg. DAERA, 08/03/2018 . 1 female, Belfast Lough , 54°43’59.88”N 005°35’60.00”W; 32 m depth; Sand; leg. DAERA, 08/03/2018 . 1 female Tartan Oil Field , 58°21’50.37”N 000°05’21.32”E; 142 m depth; Sandy Mud; leg. APEM, 14/09/2019 . 1 female Tartan Oil Field , 58°22’54.30”N 000°04’45.40”E; 141 m depth; Sandy Mud; leg. APEM, 12/09/2019 . 1 female Tartan Oil Field , 58°20’54.10”N 000°06’55.71”E; 142 m depth; Slightly sandy mud; leg. APEM, 18/09/2019 . 1 female Tartan Oil Field , 58°20’56.47”N 000°06’50.58”E; 142 m depth; Sandy Mud; leg. APEM, 16/09/2019 .

Description (male, Belfast Lough 4.5 mm)

Head Head rostrum short, strongly deflected, triangular in frontal view. Antenna 1 less than one third body length, peduncular article 3 much longer than 2; flagellum subequal in length with peduncle, with 7 articles. Antenna 2 very long, subequal in length with body, peduncular article 5 longer than 4, flagellum much longer than peduncle with about 55 articles.

Pereon. Gnathopod 1 coxa distally convex; basis stout, 4 x as long as broad, anterior margin substraight; merus blunt ending or with small posterodistal spine, but without distal extension; carpus reduced, with long, slender, distal process, extending to the tip of the dactylus; propodus slender subovoid, twice as long as broad, palm fimbriate, strongly oblique, with about 15 club-shaped robust setae each with a distal filament; dactylus elongate, slender, opposable to carpal process. Gnathopod 2 coxa subrectangular; basis very elongate, slender, parallel-sided; carpus small but with elongate spur that extends beyond tip of the propodus; propodus very elongate, slender, chelate, palm with club-shaped robust setae each with a distal filament; Pereopod 3 coxa elongate and sender, subrectangular; basis slender, 3.5 x as long as broad, posterior margin convex, anterior margin proximally concave, distally straight; merus anterior margin strongly convex; carpus and propodus elongate, subequal in length; propodus subrectangular, distally truncate; dactylus small almost hidden by long setae, anterodistal margin of merus and posterior margins of merus carpus and propodus and distal margin of propodus clothed in very long setae. Pereopod 5 basis anterior margin strongly convex, merus anterodistal margin strongly convex and with exceedingly long setae; carpus short, posterior margin irregular, with long setae; propodus longer than carpus, slender, anterior margin with long setae; dactylus elongate slender more than one third length of propodus. Pereopod 6 similar to pereopod 5 but more elongate; basis posterior margin with very long setae, anterior margin substraight; propodus subequal in length with carpus. Pereopod 7 very long, more than half body length, basis pyriform; merus, carpus, propodus and dactylus very long and slender.

Pleon. Epimera 1–3 rounded. Uropods 1–3 slender, peduncles extending about the same length. Uropod 1 peduncle much longer than subequal rami. Uropod 2 peduncle a little longer than subequal rami Uropod 3 rami subequal with each other and with peduncle. Telson distally rounded, not incised.

Female (sexually dimorphic characters). Antenna 2 only a little longer than antenna 1; flagellum with 10 articles.

Habitat and distribution. Sars (1892) recorded this species from 11–18 m depth. The material examined in this study expands this depth range to 8-323 m. The specimens were recovered from sandy substrates, with varying degrees of mud, shell or fine gravel. Pontocrates arcticus is found off all British Coasts , extending to the edge of the continental shelf off the South-West of Britain and to the limits of UK territorial waters. Beyond UK waters the species is recorded only from Norwegian waters .

Remarks. Pontocrates arcticus differs from all other Pontocrates species in its gnathopod 1–2 palms, which are fimbriated and bear club-shaped robust setae. It differs from P. moorei sp. nov., in its gnathopod 1, in that species the merus has a distal extension (absent in P. arcticus ), and the propodus is less than 2 x as long as broad and more rectangular (2 x as long as broad in P. arcticus ), in its gnathopod 2 in which the coxa is distally straight (convex in P. arcticus ), in its pereopods 3 and 4 which are very short (elongate in P. arcticus ) and in its pereopod 6 where the propodus is less than half length of the carpus (subequal in length in P. arcticus ). It differs from P. arenarius ( Spence Bate, 1858) , in the subrectangular coxa 1 (subtriangular in P. arenarius ), the elongate, subovoid propodus of gnathopod 1 (broad, subtriangular in P. arenarius ) and the subrectangular coxa 2 (posterior margin sinuous in P. arenarius ). It differs from P. norvegicus in the un-narrowed distal portion of coxa 1 (distally narrowed in P. norvegicus ) and in the elongate carpus and propodus of pereopod 3 (short carpus and propodus of pereopod 3 in P. norvegicus ).

Figures

FIGURE 1. Pontocrates arcticus male, Belfast Lough.

FIGURE 2. Pontocrates arcticus. male, Belfast Lough.