Syrrhoe crenulata Goes , 1866

Fuchs, Luisa, Coleman, Charles Oliver & Loerz, Anne-Nina, 2019, The genus Syrrhoe (Crustacea, Amphipoda, Synopiidae) from the North Atlantic, Evolutionary Systematics 3 (1), pp. 85-108 : 85

Syrrhoe crenulata Goes, 1866 Figs 12, 13, 14, 15, 16, 17

Syrrhoe crenulata Goës, 1866, p. 527, fig. 25. - G.O. Sars 1895, p. 390, pl. 136. - Stebbing 1906, p. 282. - Shoemaker 1930, p. 73. - Stephensen 1931, p. 157, chart 47. - Stephensen 1931, p. 234. Shoemaker 1955, p. 39. - J.L. Barnard 1971, p. 74. J.L. Barnard 1972, p. 53

Material examined.

1 female, 10 mm, MAREANO 2013, R1218-471, 70°34 ’57” N, 30°56 ’37” E, 155-157 m, 17.8.2013, beamtrawl, ZMBN 127922; 1 female, Sabine Island, 74°36'N 18°59'W, 7-18 m, leg. Pansch, ZMB 4699; 6 females, IceAGE st. 1090, 66°0.03'N 25°3.18'W, 742.5 m, 10.9.2011, R/V Meteor, epibenthos sledge, ZMB 31710; 1 specimen ZMH-K 56188 (GenBank MK972328), 1 specimen ZMH-K 56189 (GenBank MK972329), North west Iceland, Denmark Strait, IceAGE st. 1104, 66°38.60'N, 24°31.97'W, 119 m depth, 13.09.2011.

Description

based on: female, with un-setose oostegites, 10 mm, ZMBN 127922.

Head. Head anteriorly not produced, rounded. Rostrum reaching about half of antenna 1 article 1; lateral cephalic lobe pointed; eyes present, with dark pigmentation (present in 5 year old ethanol sample), large, oval, on dorsal part of head.

Antenna 1 (Fig. 12d) article 1 not elongate, with 2 distal curved teeth of about the same length; article 2 without distomedial tooth, longer than article 1; article 3 shorter than article 1 and 2; accessory flagellum surpassing 3rd flagellar article, accessory flagellum 2nd article as long as first flagellar article, 3rd article less than a quarter length of 1st accessory flagellar article; flagellum 19-articulate. Antenna 2 (Fig. 12b) 5th peduncular article longest; flagellum 12-articulate.

Mandible (Fig. 12c) incisor multidentate; left lacinia mobilis wide and multidentate; setal row with 6 pappose setae; molar large, triturative; mandibular palp (Fig. 12c) article 2 with many slender setae on ventral margin; article 3 a tenth of the length of article 2 (knob-like), with 6 long slender setae, considerably longer than those of article 2. Maxilla 1 (Fig. 13b) inner plate with 10 long and 2 short plumose setae; outer plate with 11 apical robust setae, some of them are bifurcate; palp article 2 outer margin smooth, with apical and medial setation. Maxilla 2 (Fig. 13a) inner plate width more than 1.3 × outer plate, inner plate with row of stout facial setae. Maxilliped (Figs 13 c–e; 14 a–b) inner plate with 2 stout setae distally and a hook-like robust seta on disto-medial anterior face; outer plate not quite reaching apex of 2nd palp article, medially lined with rather long robust setae and slender setae submarginally; palp (Figs 13c, 14b) article 2 1.7 × the length of article 3; palp article 3 slightly inflated, 4th article curved, with a long unguis.

Pereon. Pereonites 1-6 posteromarginally smooth. Pereonite 7 dorsally rounded, not carinate, posterior margin smooth except for mid-dorsal marginal little point; posterolateral corner slightly produced.

Gnathopod 1 (Figs 14c, 15a) coxa, proximally wider than apically, subrectangular with obliquely truncate apex; basis longer than coxa; merus tapering, with group of setae on posterodistal margin; carpus subrectangular (posteriorly slightly expanded), with smooth setae along the posterior margin; propodus palm transverse, defined by 1 serrate robust seta, additional smooth robust setae absent; dactylus extending to palm margin. Gnathopod 2 (Figs 15b, c, 16a) coxa not distally tapering, apex oblique; basis longer than carpus; propodus palm transverse, slightly oblique, defined by 1 serrate robust seta, additional smooth robust smooth setae absent; dactylus well developed. Pereopod 3 (Fig. 16f) coxa anterodistal lobe present, produced subacutely rounded, posterodistal lobe present, rounded, half the depth of the coxa, posterodistal margin smooth; basis width slightly wider than ischium; ischium subrectangular, a third as long as merus; propodus longest; merus, carpus and propodus setae on posterior margin; dactylus only weakly curved. Pereopod 3-4 coxa pelagont. Pereopod 4 (Fig. 16b) coxa shorter than coxa 3, slightly curved posteriorly; ischium subrectangular, a third as long as merus; merus, carpus and propodus setae on posterior margin; dactylus very weakly curved. Pereopod 5-7 (Fig. 17 a–c) coxa posteromarginally notched. Pereopod 5-7 basis anterodistal corner produced as a recurved hook, posterior margin strongly serrate. Pereopod 5 basis subovoid, expanded, posterodistal lobe well developed, rounded, not extending past ischium. Pereopod 6-7 basis ovate, posterodistal lobe well developed, rounded extending below ischium.

Pleon. Pleonite 1-3 serrate posteromarginally and a middorsal short point. Epimeron 1-2 posteroventrally acute. Epimeron 3 (Fig. 12a) posterior margin and dorsally of posteroventral corner serrate, ventral margin serration absent, posteroventrally angular.

Urosomite 1-3 dorsal and lateral margins smooth. Uropod 1 (Fig. 16d) peduncle with long laterodistal process, at least 1/3 of length of outer ramus; inner ramus longer than peduncle; apical robust setae on tip of both rami. Uropod 2 (Fig. 16c) outer ramus half the length of inner ramus, outer ramus bearing apical robust setae on the tip. Uropod 3 (Fig. 16e) length not exceeding uropods 1-2; peduncle short (less than 2 × breadth). Telson (Fig. 17d) almost as long as uropod 3 rami, more than 3 × as long as wide, cleft more than 66%.

Distribution.

Circum-Arctic and northern boreal: off Oregon; Newfoundland; Massachusetts; Gulf of St. Lawrence; Maine; North Atlantic; North Sea; Norwegian Coast, Skagerak; Spitsbergen; East and West Greenland; Arctic Ocean, 7-742.5 m. These distributional records from the literature were not checked with the original material they are based on. Due to the close resemblance of S. crenulata and S. anneheleneae sp. nov. a mix-up between these species and their occurrence cannot be excluded.

Remarks.

There are two habitus characters that discriminate Syrrhoe crenulata from the other two North Atlantic Syrrhoe species: the posterior margins of its urosomites 1 and 2 are smooth with no trace of serration and the eyes are present and have a rather dark brownish pigmentation, which is detectable even in old ethanol material (vs. no eyes visible in S. affinis and white (in ethanol), apparently unpigmented eyes in S. anneheleneae sp. nov.). The former subspecies from the Antarctic species Syrrhoe crenulata psychrophila Monod, 1926 has been raised in rank to the separate species S. psychrophila by Schellenberg (1931), because it differs in several respect from nominate subspecies S. crenulata crenulata.

The interspecific molecular distances of 17,3% ± 2% between S. crenulata and S. anneheleneae sp. nov. confirm the species concept of Syrrhoe of the North Atlantic, which is based on minute morphological differences.