Epimeria (Metepimeria) acanthurus ( Schellenberg, 1931 )

Coleman, Charles Oliver, Krapp-Schickel, Traudl & Häussermann, Vreni, 2022, Amphipod crustaceans from Chilean Patagonia, European Journal of Taxonomy 849 (1), pp. 1-57 : 20-29

Epimeria (Metepimeria) acanthurus ( Schellenberg, 1931)

Figs 12–17 , 30d

Metepimeria acanthurus Schellenberg, 1931: 162 , fig. 85, pl. 1 fig. g.

Epimeria acanthurus – K.H. Barnard 1932: 176, figs 104b, 108, pl. 1: fig.

Metepimeria acanthurus – J.L. Barnard 1958: 108. — Lowry & Bullock 1976: 122. — Watling & Holman 1981: 216–217, fig. 22. — J.L. Barnard & Karaman 1991: 397. — Gonzalez 1991: 60. — De Broyer & Jażdżewski 1993: 36. — Lörz & Brandt 2004: 179–190 (phylogeny). — Coleman 2007: 61, fig. 36, map 1 (rhomb).

“ Epimeria inermis 1” – Rauschert & Arntz 2015: 61, pl. 54.

Epimeria (Metepimeria) acanthurus – d’Udekem d’Acoz & Verheye 2017: 117–118 .

Material examined

CHILE • 1 ♀ (22 mm) with setose oostegites and slightly damaged mouthparts; Isla van der Meulen ; -48.2901°, -74.33583333°; 15 m depth; 23 Apr. 2015; 250HF24; on hydrozoans, sponges, gorgonians and soft corals (e.g., Alcyonium haddoni Wright & Studer, 1889 ); colour: orange with white specks, especially on the tergites of the pereonites; ZMB 34099 ( Figs 12–17 ) • 1 dissected ♀ (unspecified type material, with setose oostegites; Puerto Harris ; 11 Mar. 1896; Museum Stockholm leg.; ZMB 22838 .

Description (based on ♀ with setose oostegites, 22 mm).

BODY. Head ( Fig. 12a, d ) with slightly curved rostrum; eyes large and oval; frontal head margin weakly produced, ventral head margin straight. Pereonites 1–2 ( Fig. 12a ) slightly longer than pereonite 3. Pereonites 3–5 successively longer. Pereonite 5 with mid-dorsal rounded hump at posterior margin. Pereonites 6 and 7 dorsal outline sinuous and mid-dorsal rounded upright hump at posterior margin, that on pereonite 7 larger and slightly more curved posteriorly than that on 6; posterodorsolateral rounded hump on both sides. Pleonites ( Fig. 12a ) 1–3 progressively longer; pleonites 1–2 with similar dorsal outline as pereonite 7 and posterodorsolateral humps; pleonite 2 with additional hump anteriorly; pleonite 3 with 2 shallow dorsal depressions and mid-dorsal hump anterior of segmental end; posterior margins of pleonites sinuous; posteroventral corner of pleonite 1 angular, those of pleonites 2–3 pointed. Urosomite 1 longest, with mid-dorsal pointed process; urosomite 2 shortest; urosomite 3 with shallow lateral dorsal ridges.

HEAD APPENDAGES. Antenna 1 ( Fig. 13d ) peduncle stout, without long processes, peduncular articles length ratios: 1:0.4: 0.3; accessory flagellum uni-articulate, small, scale-like; flagellum 1 st article about as long as the next 3 articles, more than 11 articles (tip broken off) with groups of long setae and aesthetascs. Antenna 2 ( Fig. 13c ) peduncular articles 1–2 circumpass article 3; peduncular articles 4 and 5 subequal; flagellum 1 st article about as long as the next 3 articles, flagellum of more than 23 articles (tip broken off). Upper lip (labrum) ( Fig. 12b ) tapering distally with a shallow notch and fine setation on both sides of the notch. Mandible ( Fig. 13a–b, e ) body slender, molar triturative with serrate margins and tuft of setae on proximal margin; spine row consisting of 4 stout blade-like setae and slender additional setae; lacinia mobilis distally expanded, with 5 teeth; incisor with 6 stout rounded teeth; palp 3-articulate, length ratios of article 1–3: 1: 3.5: 2.9. Lower lip (hypopharynx) ( Fig. 12c ) with tapering distally subacute lobe and relatively short mandibular lobe. Maxilla 1 ( Fig. 14a ) inner plate with 10 plumose setae on medial margin, outer plate oblique with 11 distal spine-like setae with 1–3 distomedial processes; palp 2-articulate with short basal article and unknown distal article (damaged). Maxilla 2 ( Fig. 14c ) inner plate slightly narrower (92%) compared to outer plate, somewhat tapering distally, two rows of setae from the tip along the medial margin; outer plate subovoid with double row at apex drawing medially. Maxilliped inner plate ( Fig. 14b ) tapering distally, with 3 nodular setae apically, row of slender setae medially and subapically; outer plate ( Fig. 14d ) ovoid with serration ( Fig. 15a ) distomedially, row of setae along medial margin and submarginally distally; palp damaged.

PEREON. Gnathopod 1 ( Fig. 15b ) coxa tapering distally, apex pointed, few setae posteromarginally and some on medial face; basis slightly longer than coxa (104%), with row of short, slender setae anteromarginally and two groups of longer setae posteromarginally; ischium subquadrate; merus length 1.5× width, tapering distally, oblique apex with group of setae; carpus and propodus subequal in length with groups of setae posteromarginally; carpus with group of setae anterodistally; propodus with groups of setae on distal half of medial side; dactylus slightly curved with serrate inner curvature and distal unguis. Gnathopod 2 ( Fig. 15c ) similar in shape as gnathopod 1, but articles longer and coxa somewhat more bulky and with more setae on medial face. Pereopod 3 ( Fig. 16a ) coxa with rounded apex, weakly sinuous and with row of short setae posteromarginally; basis as long as merus and carpus combined, with setae on proximal lateral face and on both margins; ischium slightly expanded distally, slightly longer than wide; ischium to dactylus length ratios 1: 2.6: 2.1: 2.0: 1.3 and stout setae posteromarginally. Pereopod 4 ( Fig. 16b–c ) coxa longer than wide (116%), anteromarginally shallowly excavate; apex oblique, posterior margin with pointed process; basis as long as merus and carpus combined; ischium longer than wide, somewhat expanded distally; length ratios ischium to dactylus 1: 2.7: 2: 2.3:1.2. Pereopod 5 coxa ( Fig. 17a ) wider than long (119%) with wide anterior lobe and minute posterior lobe; basis anteromarginally straight, setose, posteroproximally lobate, posterodistomarginally straight, posterodistal oblique lobe; ischium subquadrate with posteromarginal notch; length ratios ischium to dactylus 1: 1.7: 2: 2.9: 1.2; merus and carpus drawn out anterodistally; ischium to propodus with robust setae along posterior margin. Pereopod 6 ( Fig. 17b ) similar in shape to pereopod 5, but anterior lobe of coxa smaller. Pereopod 7 ( Fig. 17c ) coxa slightly longer than wide (110%); basis posterior margin sinuous, posteroventral angle rounded and drawn out; length ratios ischium to dactylus 1: 2.1: 1.9: 2.5:1, shape and setation of these articles as for pereopod 5 and 6.

PLEOSOME AND UROSOME. Pleopod 1 ( Fig. 16f ) peduncle tapering distally; two coupling hooks on inner distal angle; rami longer than peduncle (145%), each article with a pair of long feather-like setae. Uropod 1 ( Fig. 17f ) peduncle weakly shorter than rami (94%), with robust setae on outer margin and a group of slender setae medioproximally; rami subequal. Uropod 2 peduncle ( Fig. 17g ) shorter than rami; outer ramus shorter than outer ramus (139 % of peduncle), inner ramus 2× the peduncle length. Uropod 3 ( Fig. 17h ) peduncle shortest; rami lanceolate, subequal in length, 2 × the peduncle length. Telson slightly longer than wide (113%), notched 24%.

Distribution (amended from De Broyer et al. 2007)

Falkland Islands: Discovery 1925–27: stn WS 81, West Falkland Island, off North Island, 81–82 m (bottom/habitat: sand; gear: nets); stn WS 85, East Falkland Island, off Lively sand; gear: nets); stn WS 85, East Falkland Island, off Lively Island, 79 m (bottom/habitat: sand, shells; gear: commercial otter trawl); stn WS 86, -53.883333°, -60.566667°, 151– 147 m (bottom/habitat: sand, shells, stones; gear: commercial otter trawl) (K.H. Barnard 1932).

Magellan Province: Puerto Condor, 90 m (bottom/habitat: rocks, ascidians); Bahia Harris, 27 m (bottom/ habitat: shells) ( Schellenberg 1931); Eltanin 9, stn 740, -56.1° to -56.116667°, -66.325°, 384–494 m; Hero 715, stn 894, -54.913333° to -55.916667°, -64.3° to -64.333333°, 263–285 m ( Watling & Holman 1981); Isla van der Meulen, 15 m (on hydrozoans) (this study).

Depth range

27– 494 m.

Type locality

Magellan Province: Puerto Condor, 90 m (bottom/habitat: rocks, ascidians); Bahia Harris, 27 m (bottom/ habitat: shells) ( Schellenberg 1931).

Type specimen location

ZMB, Berlin.

Remarks

When compared with the type material, stored at the Museum für Naturkunde Berlin (ZMB 22838), there are a few differences in the redescribed material: (1) less pronounced depression in the middle of the dorsal carinae on pereonites and pleonites; (2) shorter middorsal and symmetrical process on urosomite 1 (vs anterior margin shorter than posterior); (3) pereopod coxa 3 proximo-posteromarginally narrower; (4) pereopod coxa 4 with a narrower ventral margin, which additionally has a weak depression; (5) colour orange with white specks (vs white with red stripes in the type description: Schellenberg 1931: 162).

The few details illustrated by K.H. Barnard (1932) of material collected off the Falklands, deviate from our material in (1) the posterior margin of pleonite 3, which has a rather straight posterior margin with a pointed tooth and a drawn out middorsal carina (vs sinuous margin with rounded protrusion and rounded middorsal hump); (2) the pointed middorsal, slightly forward curved tooth (vs straight subacute tooth) on urosomite 1 and (3) the posteroventral angles of the basis of pereopods 5–7 are drawn out acutely (vs angularly subacute).

Watling & Holman (1981) published on material collected south of the Isla de los Estados. Their drawings match our material, except for the telson, which is notched only 12% (vs 26% in our material).

Figures

Fig. 12. Epimeria (Metepimeria) acanthurus (Schellenberg, 1931), ♀, 22 mm (ZMB 34099). a. Habitus, left body side. b. Upper lip. c. Lower lip, damaged. d. Right side of head. Scale bars: a, d = 1 mm; b–c = 100 µm.

Fig. 13. Epimeria (Metepimeria) acanthurus (Schellenberg, 1931), ♀, 22 mm (ZMB 34099). a. Mandible palp. b. Mandibular incisor, lacinia mobilis and raker row. c. Antenna 2. d. Antenna 1. e. Mandible. Scale bars = 100 µm.

Fig. 14. Epimeria (Metepimeria) acanthurus (Schellenberg, 1931), ♀, 22 mm (ZMB 34099). a. Maxilla 1. b. Inner plate of maxilliped. c. Maxilla 2. d. Outer plate of maxilliped. Scale bars = 100 µm.

Fig. 15. Epimeria (Metepimeria) acanthurus (Schellenberg, 1931), ♀, 22 mm (ZMB 34099). a. Serrate margin of outer plate of maxilliped. b. Gnathopod 1. c. Gnathopod 2. Scale bars = 100 µm.

Fig. 16. Epimeria (Metepimeria) acanthurus (Schellenberg, 1931),♀, 22 mm (ZMB 34099). a. Pereopod 3. b. Pereopod 4, medial aspect.c. Gill of pereopod 4. d. Oostegite of pereopod 5. e. Oostegite of pereopod 3. f. Pleopod 1. Scale bars = 1 mm.

Fig. 17. Epimeria (Metepimeria) acanthurus (Schellenberg, 1931), ♀, 22 mm (ZMB 34099). a. Pereopod 5. b. Pereopod 6. c. Pereopod 7. d. Telson.e. Oostegite of pereopod 5.f. Uropod 1. g. Uropod 2. h. Uropod 3. Scale bars: a–c, e = 1 mm; d, f–h = 100 µm.

Fig. 30. In vivo photos of some of the described amphipods. a. Sunamphitoe femorata (Krøyer, 1845). b. Numerous specimensof Caprellacf.equilibraSay, 1818,on thehydrozoanHalopteris schucherti Galea, 2006. c. Habitat of Leucothoe kawesqari Esquete & Aldea, 2015, on sponge. d. Epimeria (Metepimeria) acanthurus (Schellenberg, 1931). e–f. Podocerus cf. danae (Stebbing, 1888). g. Liouvillea rocagloria sp. nov. h. Habitat of Liouvillea rocagloria sp. nov. Photos: Iván Hinojosa (a); V. Häussermann & G. Försterra (b, d, h); G. Försterra & V. Häussermann (c, e–g).