Hemijassa goniamera

Hemijassa goniamera (Walker, 1903)

(Figs 17–21)

Jassa goniamera Walker, 1903, 61, 62, Plate 11, Figs 98–107 (part, according to Thurston (1974b), specimens less than 5 mm long are Parajassa georgiana); Stebbing, 1906, 739; Schellenberg, 1931, 253; Nicholls, 1938, 128; Stephensen, 1947, 73, Fig. 24; J. L. Barnard, 1958, 85; Lowry & Bullock, 1976, 75; Thurston, 1974b, 100.

Hemijassa goniamera Walker, 1907, 38.

Jassa falcata:? Chilton, 1912, 511; not Schellenberg, 1926, 383; Sexton & Reid, 1951, 72, 75, 77–78, 81–83, 85, 86; Bellan-Santini, 1972, 191.

Jassa ingens: K. H. Barnard, 1932, 242 Fig. 151C (in part).

Description of male. Lectotype (here designated): Length 18.3 mm.

Antenna 2: overlapped by antenna 1 to midway along article 5; article 5, posterior marginal setae very short and simple, minute compared with those of the female; flagellum 8 articles, the last 1/2 the size of the second last, article 1 46% of full length.

Mandible: palp articles 2 and 3 with a dorsal fringe of setae; raker spines 6 right, 8 left.

Gnathopod 1: coxal margins, anterior 72% of dorsal length, ventral margin straight; basis, anterior margin with a fringe of long setae laterally, posterior margin with many setae also, which are just as long and wide ranging as on the anterior margin, but more scattered; carpus, length 64% of propodus length, posterior lobe 47% of anterior margin length, anterodistal setal cluster short, 25% of the anterior margin length; propodus, palm convex; dactyl cusped along the full length, without facial striations.

Gnathopod 2: coxal margins, anterior 87% and posterior 100% of ventral length, ventral margin straight; basis, anterolateral flange with a row of long, simple filter setae (setae about 1/2 article width); carpus, posterior lobe with a cluster of distal setae; propodus, anterior margin with a series of clusters of short setae (setae about 1/2 basis width).

Pereopod 3: basis narrower than the gnathopod 1 basis, anterior margin shallowly concave; merus, anterior margin with a row of setae along its length, article width 45% of length; carpus barely 10% overlapped by merus; propodus width 40% of length.

Pereopods 5–7: basis posterodistally produced, anterior margin with a few short setae; merus and carpus, posterior margin not spinose.

Uropod 1: peduncle, posteroventral spinous process underlying 41% of the inner ramus, inner and outer rami with 12 and 13 mid-dorsal spines respectively, not terminating in a fringe of cusps ventral to the apical spine group.

Uropod 2: peduncle, posteroventral spinous process underlying 25% of the inner ramus.

Uropod 3: inner ramus not mid-dorsally spinose.

Condition. Left antenna 1, tip of flagellum missing, without left pereopod 7. Right appendages, telson and mouthparts slide mounted.

Description of adult female. Paralectotype: Length 19.9 mm. As in the genus description.

Condition. With all appendages. Right appendages, telson and mouthparts slide mounted.

Variation. Maximum body length: male 22 mm, female 20 mm. Hemijassa goniamera exhibits sexual dimorphism in the antenna 2 and gnathopod 2. The antenna 2 development appears to be much like that in species of Jassa, with antennae long with short filter setae in large males compared to females and small males (Figs 17, 18 and 20). The palm of gnathopod 2 is sinuous in small males, but with a ledge or tooth in large males (Fig. 20). In females the palm remains sinuous at all sizes (Fig. 18).

Type material examined. Lectotype, ♂, NHM 1987:515, Cape Adare, McMurdo Sound, Ross Sea, Antarctica (71°17ʹS, 170°14ʹE), “Southern Cross” Expedition, 5 November 1902. Paralectotypes, 5 ♂♂, 9 adult ♀♀, 6 small (juvenile?) males and 10 juvenile females, NHM 1902.11.5:6–10 (part), same location.

Other material examined. South Sandwich Islands: Visokoi I., 13 Nov. 1908, 60– 100 m, C. A. Larsen, coll., 1 ♀ (UiO F2968).

South Shetland Islands, Antarctica: off Cape Bowles, Clarence I., 23 Feb. 1927, ‘ Discovery’ station 170, 342 m, 5 ♂♂, 8 ♀♀ (NHM 1936:11.2:2411–2426 (part)); Bransfield Strait, 2 Mar. 1927, ‘ Discovery’ station 175, 200 m, 1 ♂ (NHM 1936.11.2: 2411–2428 (part).

Graham Region, Antarctica: Seymour I. (64°20ʹS, 56°38ʹW), 16 Jan. 1902, 150 m, Svenska Sydpolarexp. 1901– 1903, No. 5, 3 juveniles (SNM) and 10 juveniles (NRM 3679); SW of Snow Hill I., (64°36ʹS, 57°42ʹW), 20 Jan. 1902, 125 m, Svenska Sydpolarexp. 1901–1903, No. 6, 1 ♂, 1 ♀, 1 juvenile (NRM 3680).

Ross Sea, Antarctica: Coulman I., 13 Dec. 1902, 183 m, 1 ♂, 1 ♀ (NHM 1907.6.6:410–415); Flagon Pt., Winter Quarters Bay, McMurdo Sound, 23 Jan. 1903, ‘ Discovery’ Expedition, 1 ♂, 1 ♀, 1 juvenile (NHM 1907.6.6.414–415); Flagon Pt., Winter Quarters Bay, McMurdo Sound, 17 Jan. 1903, ‘ Discovery’ Expedition, 3 ♀♀ (NHM 1907.6.6:410– 415).

Weddell Sea, Antarctica: Cap Norvegia, (71°2ʹS, 12°W), 17 Feb. 1930, Norvegia Expedition, Riiser-Larsen, 1 ♀ (UiO); off Kapp Norvegia (70.0145°S, 10.00806°W), 30 Jan. 1998, Agassiz trawl beginning at 246 m, C. de-Broyer and Y. Scailteur, coll., Polarstern EASIZ II Expedition (Ant XV /3), 1 ♂ (RBINS IG28520); off Kapp Norvegia (70.01461°S, 10.00794°W), 31 Jan. 1998, Agassiz trawl beginning at 248 m, C. deBroyer and Y. Scailteur, coll., Polarstern EASIZ II Expedition (Ant XV /3), 2 ♂♂ (RBINS IG28252).

Commonwealth Bay, Antarctica: 21 Dec. 1913, 10– 120 m, Australasian Antarctic Expedition, 1 ♂ (AM P.18415).

Terre Adélie, Antarctica: Archipel de Pointe Géologie, 2 Jan.1965, 110– 130m, fond à bryozoaires, hydraires, spongiaires et alcyonaires, P.M. Arnaud, coll., station TA-D102 (D. Bellan-Santini loan).

Remarks. Schellenberg (1926) may have recorded H. goniamera at Gauss-Station (Kaiser Wilhelm II Land) during the Deutsche S̹dpolar-Expedition 1901–1903, collected on August 12, 1902 and named it Jassa falcata. Other specimens listed as “ J. falcata ” may have been P. wandeli, judging by their size and collection location. One collection of “ J. falcata ” from Terre Adélie, Antarctica and listed in Bellan-Santini (1972) was examined and found to be H. goniamera. It is likely that the other three collections listed therein (not seen) are also H. goniamera, judging by the size of the specimens (7–17 mm) and depth of collection (15–140 m).

Hemijassa goniamera is only known subtidally and can be found clinging to bryozoans and hydroids (Dauby et al. 2001). Trace metal levels are relatively low in H. goniamera and well within the range of other Antarctic amphipods (Keil et al. 2008).