Pontocrates altamarinus (Spence Bate & Westwood, 1862)

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 : 593-595

Pontocrates altamarinus (Spence Bate & Westwood, 1862)

( Fig. 7 )

Kroyera altamarina Spence Bate & Westwood, 1863: 177–178 .— Reibisch, 1905, 183, pl. 5, figs 11–15.

Pontocrates altamarinus Sars, 1895 , 695, suppl. Pl. 7, fig. 2.— Stebbing, 1906, 240.— Stephensen, 1926, 79.— Stephensen, 1928. 216, fig. 43.— Stephensen, 1929, 114, fig. 27.— Schellenberg, 1942, 178, fig. 147.— Lincoln, 1979, 342, fig. 161.— Ledoyer, 1993, 604, fig. 415.— Barnard & Karaman, 1991, 565.— Moore & Beare, 1993, 610, fig. 2.— Zettler & Zettler, 2017, 245, figs. 168=170.

Pontocrates arenarius Chevreux & Fage, 1925 , 166, fig. 167.

Not Pontocrates arenarius Spence Bate, 1858 , 15, pl. 2, fig. 1.

Type material. Holotype ( Kroyera altamarina ), Sixty miles east of Shetland, Scotland ( BMNH 1911.11.8.1193)

Material studied. 1 female; Northumberland; 55°36’58.20”N 001°42’07.80”W; 7.68 m depth; Sand; leg. Environment Agency, 29/05/2015 . 1 female; Southern North Sea ; 51°37’10.46”N 001°27’58.38”E; 23.6 m depth; Coarse Sand; leg. APEM, 23/07/2014 . 1 female; Southern North Sea ; 51°32’54.20”N 001°21’16.38”E; 19.8 m depth; Coarse Sand; leg. APEM, 06/08/2014 . 2 females; Isles of Scilly; 49°56’41.15”N 006°18’3.70”W; 6.7 m depth; Sand; leg. Natural England, 26/05/2013 . 2 females; Newquay ; 50°25’20.40”N 005°04’41.40”W; 11.3 m depth; Sand; leg. Environment Agency, 14/03/2013 . 1 female; Great Yarmouth ; 52°35’34.70”N 001°43’34.57”E; 3 m depth; Gravelly Sand; leg. APEM, 30/01/2019 .

Description (female, Northumberland, 7.0 mm)

Head Head rostrum short, weakly deflected, triangular in frontal view. Antenna 1 about one sixth body length, peduncular article 2 twice length of 3; flagellum subequal in length with peduncle, with 8 articles. Antenna 2 only a little longer than antenna 1; flagellum with 10 articles.

Pereon. Gnathopod 1 1 coxa, distal margin convex; merus without distal extension; carpal spur distally expanded; propodus subovoid, about twice as long as broad, palm beaded, strongly oblique, merging imperceptibly with posterior margin, without club-shaped robust setae. Gnathopod 2 coxa subrectangular; basis very elongate, slender, medially swollen; carpus small but with elongate spur that extends beyond tip of the propodus; propodus very elongate, slender, chelate. Pereopod 3 coxa elongate and sender, subrectangular; basis stout, 2.5 x as long as broad, posterior margin convex, anterior margin weakly concave; merus antero-distal 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 convex; merus anterodistal margin strongly convex and with exceedingly long setae; carpus short, subrectanglar; propodus a little shorter than carpus, anterior margin with long setae; dactylus distinct. Pereopod 6 similar to pereopod 5 but more elongate; basis posterior margin with very long setae. 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 subequal with rami Uropod 3 rami subequal, longer than peduncle. Telson distally rounded, not incised.

Male (sexually dimorphic characters). Antenna 2 very long, a little shorter than body, peduncular articles 4 and 5 subequal; flagellum much longer than peduncle with about 40 articles.

Habitat and distribution. Found off all British coasts. Elsewhere it is known from Norway ( Sars, 1895); the Baltic ( Reibisch, 1905; Zettler & Zettler, 2017); Denmark (Stephensen, 1926,1928); the Netherlands ( Schellenberg, 1942); France (Chevreux & Fage, (1925) and the Mediterranean ( Chevreux & Fage, 1925, Ledoyer, 1993) and Senegal (Chevreux, 1925). In the present work from the lower shore to 18 m depth in sandy mud, sand, and gravelly sands. The record of 60 miles east of Shetland for the holotype is remarkable. According to Spence Bate and Westwood (1862) it is found at 70-90 fathoms (approx. 128-165 m). Lincoln records it from 5- 100 m. Ledoyer (1993) records it as infralittoral and Chevreux & Fage give 10- 30 m.

Remarks. This species is readily distinguished from all other species in the genus by the weakly deflected head rostrum. The ‘beading’ on the palm of gnathopod 1 is unique for this species among Pontocrates . It is a large species reaching up to 7.0 mm. Among Pontocrates , only P. norvegicus approaches this size. The gnathopod 1 propodus is very long and subovoid

Figures

FIGURE 7. Pontocrates altamarinus (Spence Bate), female, Northumberland.