Amphilochus hamatus (Stephensen, 1925) Stephensen, 1925

Tandberg, Anne Helene S. & Vader, Wim, 2018, On a new species of Amphilochus from deep and cold Atlantic waters, with a note on the genus Amphilochopsis (Amphipoda, Gammaridea, Amphilochidae), ZooKeys 731, pp. 103-134 : 111-115

Amphilochus hamatus (Stephensen, 1925) comb. n.

Amphilochopsis hamatus Stephensen, 1925: 173, figs 52-53; Gurjanova 1951: 402, fig. 246; Barnard and Karaman 1991: 95.

Material examined.

Drawings are made from IINH37894 (BioIce 2077), IINH37898 (BioIce 2236), IINH37900 (BioIce 2318) and IINH37903 (BioIce 2367). Material from IceAGE and NorAmph has been used for molecular sequencing and comparisons. For a list of stations for the material, see Table 1. Type material not examined. The drawings are shown on Figs 9-12.

Description.

Head. Rostrum curved, reaches tip of article 1, antenna 1. Eyes not evident, but an ill-defined eye-patch can be seen. Cephalic lobe produced distally and rounded. Antenna 1 shorter than antenna 2; second peduncle-article with a triangular production on the apex the size of third peduncle article; peduncle subequal to ten-articulate flagellum; no accessory flagellum. Antenna 2 peduncle longer than flagellum; short setae on peduncle, and a pair of long setae at tip of flagellum.

Labrum asymmetrically bilobed. Mandible molar small but triturative, cone-shaped; incisor serrate; ten accessory spines; palp slender, 3-articulate with series of short setae on article 3, one long seta at tip; lacinia mobilis laterally expanded. Labium symmetric, with inner lobe reduced; sharp tooth making tip of outer lobe look dentate. Maxilla 1 palp 1-articulate, with a crown of two robust setae and a serrate distal margin; inner plate reduced, 1 seta; outer plate with four and eight heavy and five smaller setae. Maxilla 2 long and thin; inner plate shorter than outer plate; three heavy setae and eight smaller setae on outer plate; inner plate with seven short setae distally and one to two thin setae medially. Maxilliped inner plate small and thin, well separated, just reaching past ischium; outer plate reaching mid-merus, two strong setae distally, serrations on inner margin; palp slim, heavily setulated on carpus and propodus.

Mesosome dorsally smooth; segment 3 shorter than segment 4. Coxa 1 reduced, subquadratic and covered by coxa 2, which is longer than broad. Coxa 2 distal margin smooth, no setae. Coxa 3 concave, smooth, with setae on distal margin. Coxa 4 distal margin smooth with setae. Coxa 5-7 concave.

Pereopod 1 basis subequal to propodus length, upper half distally widened, three long setae posteriorly; carpal lobe 65% of propodus posterior margin; propodus subtriangular, palm oblique, serrate, no setae defining palmer corner, anterodistal tooth of medium size; dactylus with inner margin partly serrate. Pereopod 2 basis weakly longer than propodus, linear; merus with a clearly defined “hook” on posterior side, close to carpus; carpal lobe 100% of propodus posterior margin, boat-shaped with a row of setae on margin; propodus subovate, palm oblique, defined mostly by its serration and upper third with small setae, no setae defining palmar corner, anterodistal tooth large (same size as breadth of the base of dactylus); dactylus inner margin with a row of small and strong setae, otherwise smooth. Pereopod 3 posterior margin of basis with an even row of slender setae; merus with small lobe. Pereopod 4 basis with very thin setae. Pereopods 5 and 6 basis and merus with posterior lobes; dactylus longer than half-length propodus. Pereopod 7, basis and merus with posterior lobes.

Metasome smooth. Epimeral plates rounded, no teeth. Urosome smooth; segment 1 long; segments 2 and 3 short. Uropod 1 peduncle subequal to rami; rami subequal; both peduncle and outer ramus with marginal setae. Uropod 2 peduncle subequal to inner ramus; outer ramus half-length of inner ramus; setation on peduncle and rami. Uropod 3 peduncle marginally longer than rami; outer ramus half-length of inner ramus; rami shorter than telson; setation on peduncle and rami. Gills on segments 2 to 6. Oostegites on segments 2 to 6. Telson elongate, longer than broad; distal end entire and tridentate, all lobes rounded; no setae.

Distribution.

This species appears to have a wide depth range based on our collections (206 to 1407 m), although Stephensen (1925) found it only in deep water (700 to 2702 m). The temperatures it has been found at range from -0.6 to +7.0 °C. It is also recorded from the deep Norwegian Sea ( Dahl 1979), the Arctic basin ( Gurjanova 1951), Greenland ( Brandt et al. 1996) and the deep polar basin ( Tzvetkova and Golikov 2001).