Eurythenes gryllus (Lichtenstein, 1822)

Stoddart, Helen E. & Lowry, James K., 2004, The deep-sea lysianassoid genus Eurythenes (Crustacea, Amphipoda, Eurytheneidae n. fam.), Zoosystema 26 (3), No. 3, pp. 425-468 : 429-451

Eurythenes gryllus (Lichtenstein in Mandt, 1822) ( Figs 1-11 )

Gammarus gryllus Lichtenstein in Mandt, 1822: 34.

Lysianassa magellanica Milne Edwards 1848: 398 . — Lucas 1857: 13, pl. 1 fig. 3. — Bate 1862: 66, pl. 10 fig. 5; 1866: 330. — Lilljeborg 1865a: 3; 1865b: 2. — Bethune 1869: 431. — M. Sars 1869: 260.

Eurytenes magellanicus – Lilljeborg 1865a: 11, pls 1-3; 1865b: 6. — Sars 1891: pl. 30.

Lysianassa gryllus – Goes 1866: 517, pl. 36 fig. 1. — Bate 1867: 229.

Eurytenes gryllus – Boeck 1871: 105; 1872: 144. — Stuxberg 1880: 62. — Stephensen 1912b: 528.

Eurythenes gryllus – Smith 1884a: 54. — Hansen 1888: 67. — Chevreux 1889: 298, fig.; 1935: 50, pl. 1, figs 6, 7 — Stebbing 1893: 80; 1906: 73. — Chilton 1911: 563. — Stephensen 1925: 110; 1932: 356 (in part, part = E. obesus ); 1933: 12, figs 4, 5 (in part, part = E. obesus ); 1935: 91; 1942: 474 (in part, part = E. obesus ); 1949: 3 (?in part, part may = E. obesus ). — Schellenberg 1927: 679, fig. 70; 1955: 192. — K. H. Barnard 1937: 144. — Shoemaker 1945: 186 (in part, part = E. obesus ); 1956: 177. — Gorbunov 1946: 43. — Gurjanova 1951: 265, fig. 134; 1962: 340; 1964: 277. — Dahl 1954: 3. — Birstein & Vinogradov 1955: 225; 1958: 228; 1960: 183; 1962: 36; 1970: 420 (table 1). — Hurley 1957: 2 (in part, part may = E. obesus , part probably = E. thurstoni ). — J. L. Barnard 1958: 92; 1961: 35 (in part), fig. 5 (material from South Pacific and figs 6, 7 = E. thurstoni ). — Oldevig 1959: 19. — Templeman 1967: 215, figs 1-3. — Beck 1969: 34, 35. — Bowman & Manning 1972: 193, figs 2-5. — Paul 1973: 289. — Rannou & Nouguier 1974: 142. — Shulenberger & Hessler 1974: 185. — Dahl et al. 1976: 75, 78. — Lowry & Bullock 1976: 90. — Shulenberger & Barnard 1976: 241. — Griffiths 1977: 97. — Intes 1978: 4, fig. 4. — Andres 1979: 96; 1983: 186; 1987: 96. — Dahl 1979: 168, fig. 6. — George 1979a: 283; 1979b: 63. — Hessler et al. 1979: 704. — Ortiz 1979: 19. — Smith et al. 1979: 57. — Thurston 1979: 56; 1990: 262; 1994: 14, unnumbered fig.; 2000: 684 (table 2), 688, 690. — Hallberg et al. 1980: 280. — Just 1980: 164 (table 2), 167, 171. — Prince 1980: 63 (table 4). — Hessler 1981: 397. — Kamenskaya 1981: 95, figs 1, 2. — Umezu 1982: 2; 1984: 128. — Ingram & Hessler 1983: 683; 1987: 1889. — Lampitt et al. 1983: 73. — Petter 1983: 177, fig. 1. — Smith & Present 1983: 183. — Wickins 1983: 83. — Smith & Baldwin 1984: 1179. — Desbruyères et al. 1985: 233. — Hargrave 1985: 443. — Hopkins 1985: 202, 206, 210. — Laver et al. 1985: 1136. — Rauschert 1985: 319. — Wilson et al. 1985: 1248. — Ainley et al. 1986: 848. — Hasegawa et al. 1986: 70. — Reinhardt & Van Vleet 1986: 151, 157. — Baldwin & Smith 1987: 425. — Bucklin et al. 1987: 1795. — Charmasson & Calmet 1987: 1509; 1989: 159; 1990: 227. — Sainte- Marie & Hargrave 1987: 436. — Calmet & Charmasson 1989: 163. — Costello et al. 1989: 32. — Christiansen et al. 1990: 35; 2001: 2409. — Rauschert 1990: 454. — Vinogradov 1990: 42, 92; 1997: 77. — Wakabara et al. 1990: 5; 1996: 355 (table 1), 360 (table 2). — Barnard & Karaman 1991: 486. — Boudrias 1991: 13, figs 1, 2; 2002: 581. — Gage & Tyler 1991: 78. — Gonzalez 1991: 59. — Palerud & Vader 1991: 35. — Rauschert 1991: 37, 39. — Sainte-Marie 1991: 217; 1992: 105. — Steele & Steele 1991: 1250, figs 3, 4. — Hargrave et al. 1992a: 37; 1992b: 41; 1994: 1489; 1995: 1905. — Smith 1992: 1040. — Smith et al. 1992: 669, 671 (table 3). — Britton & Morton 1993: 369; 1994: 391. — Christiansen & Thiel 1993: 12. — De Broyer & Jazdzewski 1993: 67. — Heinrich et al. 1993: 6. — Lopes et al. 1993: 209. — Ishimaru 1994: 58. — Kaufmann 1994: 54. — Thurston & Bett 1995: 201. — Christiansen 1996: 345. — France & Kocher 1996a: 633 (in part, part = E. thurstoni ); 1996b: 304. — Vinogradov et al. 1996: 8. — Gebruk et al. 1997: 116. — Jones et al. 1998: 1124. — Matsumasa et al. 1998: 686. — Takeuchi & Watanabe 1998: 285. — Creasey & Rogers 1999: 28, 32, 42, 43, 50, 78, 81, 87, 96, fig. 11. — Witte 1999: 142. — Christiansen & Martin 2000: 3027. — Janssen et al. 2000: 3011 (table 5). — Bluhm et al. 2001: 642. — Bühring & Christiansen 2001: 369. — Dauby et al. 2001: 81. — Johnson et al. 2001: 198 (table 3). — Klages et al. 2001: 293. — Takeuchi et al. 2001: 653. — Cherel et al. 2002a: 272 (table 6); 2002b: 288 (table 3), 292 (table 4). — Thurston et al. 2002: 205. — Treude et al. 2002: 1281. — Premke et al. 2003: 283.

Euryporeia gryllus – Sars 1891: 86, [pl. 30 as Eurytenes gryllus ]. — Della Valle 1893: 848, pl. 60 fig. 58. — Chevreux 1895: 426; 1899a: 147, 148; 1899b: 152; 1900: 24, pl. 14 fig. 4; 1903: 96; 1905: 7; 1910: 4. — Holmes 1903: 277. — Brüggen 1907: 215. — Grieg 1925: 21.

Eurythenes magellanicus – K. H. Barnard 1932: 59. — J. L. Barnard 1958: 92. — Beck 1969: 35. — Conroy 1972: 56. — Arnaud 1974: 592 (list).

Eurysthenes gryllus – Smith 1884b: 181 (lapsus calami). Eurythenes grillus – Gilchrist & MacDonald 1980: 35 (lapsus calami).

Eurythennes gryllus – Poupin et al. 1990: 94, pl. 2 fig. g. — Poupin 1994: 16; 1996: 42, fig. h. (lapsus calami).

Eurythenes cf. gryllus – Lowry & Stoddart 1994: 158 (in part, part = E. thurstoni ).

Unnamed specimen in photograph – Yayanos 1978: 1056, fig. 1.

Not Eurythenes gryllus – Murdoch 1885 (= Anonyx nugax ). — K. H. Barnard 1940: 440, 515 (list) (= E. obesus ). — Springer & Bullis 1956: 6 (= E. obesus ). — Lowry & Stoddart 1993: 72 (= E. thurstoni ).

DIAGNOSIS. — Anterodorsal margin of head smooth. Gnathopod 1 parachelate; basis length 2 to 2.5 times breadth; propodus slightly tapering distally. Pereopods 3 to 7 dactyli short. Pereopod 4 coxa as deep as wide. Pereopod 7 basis, length of anterior margin subequal to breadth; posteroventral margin straight. Pleonite 3 with anterodorsal notch. Epimeron 3 posteroventral corner broadly rounded. Urosomite 1 not dorsodistally produced over urosomite 2. Uropod 3 peduncle, medial face without robust setae.

LICHTENSTEIN’ S SPECIMEN ( FIGS 1-3 )

Holotype (of Gammarus gryllus Lichtenstein in Mandt, 1822), female, 81 mm, with well developed setose oostegites, from stomach of Northern Fulmar , Greenland Sea ( ZMB 1265 ).

This specimen was described by Lichtenstein (in Mandt 1822), but not illustrated. The illustrations in Goes (1866) are the first (and only) of this specimen. The whole mouthpart bundle (including the upper lip and epistome) has been removed from the specimen and all these parts are now lost. This had probably occurred before Goes saw the specimen, as he did not illustrate any mouthparts. Other parts of the specimen are also missing, and may have been missing when it was first collected.

Description

Head much deeper than long, not extending much below insertion of antenna 2, anterodorsal margin smooth; lateral cephalic lobe small, narrowly rounded; rostrum absent; eyes not apparent. Antenna 1 peduncular article 1 short, length subequal to breadth, distal margin without significant protrusions; peduncular article 2 short, 0.35 times article 1; peduncular article 3 short, 0.13 times article 1; accessory flagellum 3+-articulate [broken], article 1 long, 5.3 times article 2; flagellum with strong two-field callynophore, 5+- articulate [broken], calceoli absent. Antenna 2 peduncle without brush setae; peduncular article 1 greatly enlarged, covering article 2 laterally; article 3 short, about 0.6 times article 4; flagellum 14+-articulate [broken]; calceoli absent.

Stoddart H. E. & Lowry J. K.

Mouthparts unknown.

Pereonites 1 to 5 dorsally smooth; pereonites 6 and 7 with weak dorsal ridge. Gnathopod 1 subchelate or parachelate [dactyl missing]; coxa vestigial; basis long, slender, length 2.3 times breadth, anterior margin smooth, with tufts of slender setae; ischium short, length 1.4 times breadth; merus with tuft of long slender setae near posterodistal corner; carpus wedge-shaped, produced anteriorly, short, length 1.5 times breadth, shorter than (0.9 times) propodus, with tuft of long slender setae on anterodistal corner and long slender setae near posterodistal corner; propodus large, subrectangular, length 1.9 times breadth, slightly tapering distally, posterior margin subtly sinusoidal, smooth, with some setae [most missing], palm transverse, margin straight, minutely serrate, posterodistal corner with at least one medial robust seta [broken, but socket visible; lateral area too damaged to assess]; dactylus unknown. Gnathopod 2 minutely chelate; coxa small, shorter than coxa 3; ischium long, length 3.6 times breadth; carpus long, length 4.3 times breadth, posterior margin straight; propodus subrectangular, long, length 3.1 times breadth; palm obtuse with convex rugose margin, with three medial and one lateral robust setae; dactylus not quite reaching corner of palm, posterior margin smooth. Pereopod 3 coxa large; merus expanded anteriorly; propodus with at least eight sets of setae on posterior margin [all broken] and one posterodistal robust seta; dactylus short, slender. Pereopod 4 coxa as deep as wide (length 1.03 times breadth), with large posteroventral lobe, anterior margin slightly round- ed; merus expanded anteriorly; propodus and dactylus missing. Pereopod 5 coxa with anterior and posterior lobes subequal; basis expanded posteriorly, posterior margin minutely crenate; merus expanded posteriorly, with curved posteri- or margin; propodus with nine groups of robust setae along anterior margin and two anterodistal robust setae; dactylus short, slender. Pereopod 6 coxa small, not lobate posteriorly; merus expand- ed posteriorly, with curved posterior margin; propodus with 10 groups of robust setae along anterior margin and two anterodistal robust setae; dactylus short, slender. Pereopod 7 basis expanded posteriorly, anterior length 1.1 times breadth, posterior margin slightly rounded, minutely crenate, posteroventral corner rounded, posteroventral margin straight; merus expanded posteriorly, with curved posterior margin; propodus with 10 groups of robust setae along anterior margin, two anterodistal robust setae and three pairs of robust setae along posterior margin; dactylus short, slender.

Oostegites present from gnathopod 2 to pereopod 5, long, setose [but with most setae missing]. Gills present from gnathopod 2 to pereopod 7.

Pleonites 1 to 3 with weak dorsal ridge; pleonite 3 with anterodorsal notch. Epimeron 1 anteroventral corner rounded, with a few slender setae. Epimeron 2 ventral margin lined with short fine setae, posteroventral corner produced into sharp spine. Epimeron 3 ventral margin lined with short fine setae, posteroventral corner broadly rounded. Urosomite 1 with anterodorsal notch. Uropod 1 peduncle with 26 dorsolateral, one apicolateral, 18 dorsomedial and two apicomedial robust setae, without plumose setae; rami subequal in length; outer ramus with 17 lateral and at least five medial robust setae; inner ramus with seven lateral and eight medial robust setae. Uropod 2 peduncle with 20 dorsolateral, two apicolateral, 11 dorsomedial and one apicomedial robust setae; rami subequal in length; outer ramus with 21 lateral and eight or nine medial robust setae; inner ramus with eight lateral and 11 medial robust setae, without constriction. Uropod 3 peduncle short, length 1.8 times breadth, without dorsolateral flange, with four apicomedial robust setae, without midmedial setae, with 10 distoventral robust setae, with lightly plumose setae on dorsomedial margin; rami paddle-like, subequal in length, inner ramus about 0.9 times outer ramus; outer ramus twoarticulate, article 2 short, article 1 with four lateral and seven medial robust setae; inner ramus with 11 medial robust setae; slender plumose setae present on both rami. Telson longer than broad, length 2.6 times breadth, deeply cleft (65%), without dorsal setae, distally tapered, without apical setae.

H. MILNE EDWARDS’ SPECIMEN ( FIGS 4-7 ) Holotype (of Lysianassa magellanica H. Milne Edwards, 1848 ), female, c. 85 mm, with well developed setose oostegites, collected by d’Orbigny from stomach of a large fish caught off Cape Horn, Drake Passage, [c. 56°S, 67°W] (MNHN-Am 3148).

H. Milne Edwards (1848) gave only a brief description of a few characters and no illustrations of his new species, Lysianassa magellanica . Lucas (1857) repeated some of Milne Edwards’ description and provided a whole animal figure. Bate (1862: 66) gave a brief description of Lysianassa magellanica , and a whole animal figure taken from a tracing of Lucas’ plate which he said he had “corrected from a specimen – the original type, I believe, of M. Milne-Edwards”. Bate’s figure is somewhat stylised compared to that of Lucas, and at least two of Bate’s “corrections” are wrong. Firstly, Lucas’ figure shows antenna 2 about twice the length of antenna 1, and he states that the first antennae are “courtes, […] ne dépassent pas la partie médiane du premier anneau thoracique” but the second antennae “atteignent le quatrième anneau du thorax”; Bates’ figure shows antennae 1 and 2 subequal, and his description states “Antennae subequal”. Lilljeborg (1865a: 3, footnote 1) wrote that in Bate’s (1862) British Museum Catalogue, “neither the description nor the drawing is good”. Bate (1866: 331) responded in defence of his illustration: “[…] we feel assured that both the short description and the figure may be depended

Stoddart H. E. & Lowry J. K.

upon, except perhaps that of one of the inferior antennae, which was broken off when we saw it […] but which, if our memory is not treacherous, was ascertained by comparison with the same organ on the opposite side; or it may have been hypothetically inserted”. Unfortunately both second antennae are now missing from the specimen, but there seems no reason to doubt Lucas’ description and figure; all specimens of Eurythenes that we have seen have the second antenna about twice the length of the first antenna. Secondly, the deep anterodorsal notches on pleonite 3 and urosomite 1 are clearly shown in Lucas’ figure, but have been omitted entirely in Bate’s figure. Bate’s (1862: 66) description of uropod 3 (the “posterior pair of pleopoda”) as “having the rami styliform, clean, scarcely longer than the base” is puzzling, wrong, and probably in part a misreading of both Milne Edwards’ and Lucas’ description of the telson as “deux appendices styliformes très forts représentent le septième anneau”. Bate’s confusion about uropods and telson is compounded in his 1866 report. He did not accept Lilljeborg’s genus Eurytenes and suggested that Lilljeborg’s material would fit just as well to Anonyx , “into which the species described as Lysianassa magellanica , with its squamiform, undivided telson, cannot enter” ( Bate 1866: 332). Bate further states that “the superior antennae […] carry a secondary appendage that itself reaches beyond that of the primary branch in L. magellanica ” ( Bate 1866: 331) . This statement was presumably based on Lucas’ figure, which actually shows both left and right antenna 1, not antenna 1 with its accessory flagellum. K. H. Barnard (1932) noted some of Bate’s confusing statements and re-published Milne Edwards’ original description. The specimen has never been adequately described or figured.

When we received this specimen it was mounted with glue onto a slab of glass. It was photographed in situ and then carefully removed from the glass. It is in relatively good condition, considering its history. The right gnathopod 1 and pereopod 5 were missing from the specimen and both antennae 2 were broken off at the end of the peduncle, the flagella missing. Many margins are abraded or worn, particularly those of the pereopods and uropods, so that many setae are missing, represented only by their insertion points or broken stumps. The apparently stocky dactyls of pereopods 3 and 6 are probably an artefact; the extremity of the cuticle seems abrad- ed or maybe digested.

Description

Head much deeper than long, not extending much below insertion of antenna 2, anterodorsal

Stoddart H. E. & Lowry J. K.

margin smooth; lateral cephalic lobe small, narrowly rounded; rostrum absent; eyes not apparent. Antenna 1 short, 0.1 times body; peduncular article 1 short, length 1.2 times breadth, distal margin without significant protrusions; peduncular article 2 short, 0.22 times article 1; peduncular article 3 short, 0.19 times article 1; accessory flagellum medium length (about 0.5 times primary flagellum), 15-articulate, article 1 long, 4.3 times article 2; flagellum 30+- articulate [broken], with strong two-field callynophore, calceoli absent. Antenna 2 relative length not known [both flagella missing]; peduncle without brush setae; peduncular article 1 greatly enlarged, covering article 2 laterally; peduncular article 3 short, 0.7 times article 4; [flagellum missing].

Mouthpart bundle subquadrate. Epistome and upper lip separate; epistome produced, angular; upper lip not produced, slightly rounded. Mandible incisors symmetrical, large, with smooth slightly convex margins; lacinia mobilis a long slender distally-cuspidate robust seta; accessory setal row left row with 13, right row with 15, short, slender, robust setae; intermediate setae pappose; molar large, setose with vestigial distal triturating patch; palp attached midway, article 1 short, length 1.3 times breadth, article 2 slender, length 2.6 times breadth, once article 3, with many submarginal posterodistal A2-setae, without D2-setae, article 3 falcate, long, length 3.2 times breadth, with one proximal A3-seta, with 46 D3-setae along most of posterior margin, with eight to 10 apical and subapical E3-setae. Maxilla 1 inner plate narrow, with 15 apical pappose setae; outer plate narrow, with 11 setal-teeth in 8/3 crown arrangement, with ST1 to ST3 large, slender, smooth to weakly cuspidate, ST4 to ST6 large, slender, four- to six-cuspidate, ST7 slightly displaced from ST6, long, slender, curved, nine-cuspidate medially; STA to STD large, broad, two- to six-cuspidate; palp large, two-articulate, with three apical and four subapical long robust setae and four subapical slender setae, flag seta absent, distomedial margin smooth. Maxilla 2 inner and outer plates broad; inner plate length 0.7 times outer plate. Maxilliped inner plate large, subrectangular, with four apical nodular robust setae and seven distal robust setae on lateral face near inner margin, oblique setal row well developed, with 14 pappose setae; outer plate medium size, subovate, with 18 apical pappose setae, with three apical robust setae, medial setae small, bead-shaped, submarginal setae absent; palp large, four-articulate, article 2 very broad, length 1.5 times breadth, 1.3 times article 3, article 3 long, slen- der, length 2.6 times breadth, dactylus well developed, with 10 subapical setae, unguis present.

Pereonites 1 and 2 dorsally smooth, pereonites 3 to 7 with mid-dorsal ridge. Gnathopod 1 parachelate; coxa vestigial; basis long, slender, length 2.2 times breadth, anterior margin smooth, with many slender setae; ischium short, length 1.4 times breadth; merus posterior margin lined with long slender setae; carpus wedge-shaped, not produced anteriorly, short, length 1.4 times breadth, shorter than (0.85 times) propodus, with long slender setae near posterodistal corner; propodus large, subrectangular, length twice breadth, tapering distally, posterior margin subtly sinusoidal, smooth, with slender setae, palm transverse, margin convex (posterior to small robust seta near insertion of dactylus), smooth, posterodistal corner with one medial and one lateral robust seta; dactylus simple, without subapical spines or slender setae. Gnathopod 2 minutely subchelate; coxa small, shorter than coxa 3; ischium long, length 3.6 times breadth; carpus long, length 4.2 times breadth, posterior margin straight; propodus subrectangular, long, length 3 times breadth, palm transverse, with straight, smooth margin, with two medial and four lateral robust setae; dactylus reaching corner of palm, posterior margin smooth. Pereopod 3 coxa large; merus expanded anteriorly; propodus with many slender setae along posterior margin and one posterodistal robust seta; dactylus short, stocky. Pereopod 4 coxa about as deep as wide (length 1.1 times breadth), with large posteroventral lobe, anterior margin slightly rounded; merus expanded anteriorly; dactylus short, slender. Pereopod 5 coxa with anterior and posterior lobes subequal; basis expanded posteriorly, posterior margin minutely crenate; merus expanded posteriorly, with curved posterior margin; propodus with nine groups of robust setae along anteri- or margin and two anterodistal robust setae; dactylus short, slender. Pereopod 6 coxa small, not lobate posteriorly; basis expanded posteriorly with minutely crenate posterior margin; merus expanded posteriorly, with slightly curved posteroproximal margin and slightly curved posterodistal margin; propodus with eight groups of robust setae along anterior margin and two anterodistal robust setae; dactylus short, stocky. Pereopod 7 basis expanded posteriorly, anterior length 1.2 times breadth, posterior margin slightly rounded, minutely crenate, posteroventral corner rounded, posteroventral margin straight; merus expanded posteriorly, with sloping straight posteroproximal margin and straight posterodistal margin; propodus with nine groups of robust setae along anterior margin, two anterodistal robust setae and three pairs of robust setae along posterior margin; dactylus short, stocky.

Oostegites present from gnathopod 2 to pereopod 5, long, setose. Gills present from gnathopod 2 to pereopod 7.

Pleonites 1 to 3 with mid-dorsal ridge, increasing in size posteriorly; pleonite 3 with anterodorsal notch. Epimeron 1 anteroventral corner rounded with a few short slender setae. Epimeron 2 ventral margin lined with short fine setae; posteroventral corner produced into sharp spine. Epimeron 3 ventral margin lined with short fine setae; posteroventral corner broadly rounded. Urosomite 1 with anterodorsal notch. Uropod 1 peduncle with 35 dorsolateral, 19 dorsomedial and three apicomedial robust setae; rami subequal in length; outer ramus with 20 lateral and seven medial robust setae; inner ramus with 11 lateral and 11 medial robust setae. Uropod 2 peduncle with 21 dorsolateral, 12 dorsomedial and one apicomedial robust setae; rami subequal in length; outer ramus with 21 lateral and eight medial robust setae; inner ramus with 13 lateral and 16 medial robust setae, without constriction. Uropod 3 peduncle short, length 1.7 times breadth, without dorsolateral flange, with three apicomedial robust setae, without midmedial slender or robust setae, with at least 10 distoventral robust setae, with lightly plumose setae on dorsomedial margin; rami paddle-like, subequal in length, inner ramus about 0.9 times outer ramus; outer ramus two-articulate; both rami with a few small robust setae on distolateral margin, slender plumose setae present on both rami; [most of the distal setae are missing, only insertion points remain]. Telson longer than broad, length twice breadth, deeply cleft (80%), without dorsal setae, distally tapered, tips of both lobes damaged.

Remarks

The mid-dorsal ridge is distinct but low from pereonite 3 to pleonite 1; from pleonite 2 to urosomite 1 the ridge is strong enough to be described as a slight carina, strongest on pleonite 3. On all segments the ridge is slightly more pronounced posteriorly.

LILLJEBORG’ S SPECIMEN ( FIGS 8-10 )

Material of Lilljeborg 1865a (as Eurytenes magellanicus ), immature female, 55 mm, with short non-setose oostegites, Bear Island, Arctic Ocean, [c. 74°N, 19°E], from stomach of Scymnus borealis (MNHN-Am 4479).

The label with this specimen reads: “ Eurythenes magellanicus . Île Boeren. Mer Glaciale. Lilljeborg. 133-67”. Lilljeborg (1865a: 3, 4), recorded three specimens of Lysianassa magellanica brought to the Zoological Museum by Mr Th. M. Fries, who “had received them from a shipper in Hammerfest, who had found them in the belly of an ‘Haaskierding’ […], on the banks by Beeren Island”. Bate (1867), writing in the Zoological Record for 1866, commented that he had received a letter from M. Alphonse Milne-Edwards saying that “J’ai reçu dernièrement de M. le Prof. Lilljeborg un exemplaire de son Eurytenes magellanicus […]”. With the agreement of Drs Saint Laurent and Defaye of MNHN, we believe the specimen we illustrate here is the one sent to Paris by Lilljeborg, and one of the three specimens he used when establishing the genus Eurytenes .

Description

Head much deeper than long, not extending much below insertion of antenna 2, anterodorsal margin smooth; lateral cephalic lobe small, narrowly rounded; rostrum absent; eyes not apparent. Antenna 1 short; peduncular article 1 short, length equals breadth, distal margin with small midmedial swelling; peduncular article 2 short, 0.37 times article 1; peduncular article 3 short, 0.19 times article 1; accessory flagellum 10+- articulate [broken], article 1 long, 4.4 times article 2; flagellum 10+-articulate [broken], with strong two-field callynophore, flagellum without robust setae, calceoli absent. Antenna 2 length not known; peduncle with weak brush setae [setae missing but insertion points visible]; peduncular article 1 enlarged, covering article 2 laterally; peduncular article 3 short, subequal to article 4; flagellum missing.

Mouthpart bundle subquadrate. Epistome and upper lip separate, epistome produced, rounded; upper lip not produced, slightly rounded. Mandible incisors large, with slightly convex margins; lacinia mobilis a long slender distallycuspidate robust seta; accessory setal row left and right with nine short, slender, robust setae; intermediate setae pappose; molar large, setose with vestigial distal triturating patch; palp attached midway; article 1 short, length 1.4 times breadth; article 2 slender, length 2.9 times breadth, 1.1 times article 3, with many submarginal posterodistal A2-setae, without D2-setae; article 3 falcate, long, length 3.1 times breadth, with one proximal A3-seta, with about 50 D3-setae along most of posterior margin, with two apical and six subapical E3-setae. Maxilla 1 inner plate narrow, with eight apical and subapical pappose setae; outer plate narrow, with 11 setal-teeth in 8/3 crown arrangement; ST1 to ST6 large, slender, weakly cuspidate, ST7 slightly displaced from ST6, elongate, slender, curved, eight-cuspidate medially; STA large, broad, two-cuspidate; STB and STC large, broad, five-cuspidate; STD large, broad, six-cuspidate; palp large, two-articulate, with five apical and one apicolateral long robust setae, with three subapical setae, flag setae absent, distomedial margin smooth. Maxilla 2 inner and outer plates broad; inner plate length 0.6 times outer plate. Maxilliped inner plate large, subrectangular, with three apical nodular robust setae; oblique setal row well developed, with at least 16 pappose setae; outer plate medium sized, subovate, with 18 apical pappose setae and three apical robust setae, medial setae small, bead-shaped, submarginal setae vestigial; palp large, four-articulate, article 2 very broad, length 1.8 times breadth (when completely flattened), 1.4 times article 3, article 3 long, slender, length 2.8 times breadth, dactylus well developed, with seven subapical setae, unguis present.

Pereonites 1 to 4 dorsally smooth; pereonites 5 to 7 with slight mid-dorsal ridge. Gnathopod 1 parachelate; coxa vestigial; basis long, slender, length 2.3 times breadth, anterior margin smooth, with tufts of slender setae; ischium short, length 1.3 times breadth; merus posterior margin lined with long slender setae; carpus wedge-shaped, produced anteriorly, short, length 1.5 times breadth, shorter than (0.79 times) propodus, with long slender setae near posterodistal corner; propodus large, subrectangular, length twice breadth, slightly tapering distally, posterior margin subtly sinusoidal, smooth, with tufts of slender setae, palm transverse, margin straight, minutely serrate, posterodistal corner with one medial and one lateral robust seta; dactylus simple, without subapical spines or slen- der setae, reaching beyond palm. Gnathopod 2 minutely subchelate; coxa large, shorter than coxa 3; ischium long, length 3.4 times breadth; carpus long, length 4.3 times breadth, posterior margin straight; propodus subrectangular, long, length 3.1 times breadth, palm slightly obtuse, with convex, rugose margin, with two medial and two lateral robust setae; dactylus reaching corner of palm, posterior margin smooth. Pereopod 3 coxa large; merus expanded anteriorly; propodus with seven tufts of slender setae along posterior margin [some setae missing, insertion points visible] and one posterodistal robust seta; dactylus short, slen- der. Pereopod 4 coxa as deep as wide (length 1.02 times breadth), with large posteroventral lobe, anterior margin slightly rounded; merus expanded anteriorly; propodus with five tufts of slender setae along posterior margin and one posterodistal robust seta; dactylus short, slender. Pereopod 5 coxa anterior and posterior lobes subequal; basis expanded posteriorly, posterior margin minutely crenate; merus expanded posteriorly, with curved posterior margin; propodus with eight groups of two or three short robust setae along anterior margin and two anterodistal robust setae; dactylus short, slender. Pereopod 6 coxa small, not lobate posteriorly; basis expanded posteriorly, posterior margin minutely crenate; merus expanded posteriorly, with curved posteri- or margin; propodus with eight groups of three or four short robust setae along anterior margin and two anterodistal robust setae; dactylus short, slender. Pereopod 7 basis expanded posteriorly, anterior length 1.1 times breadth, posterior margin slightly rounded, minutely crenate, posteroventral corner rounded, posteroventral margin straight; merus expanded posteriorly, with curved posterior margin; propodus with eight groups of two to five short robust setae along anterior margin and two anterodistal robust setae, with three pairs of robust setae along posterior margin; dactylus short, slender.

Oostegites present from gnathopod 2 to pereopod 5, short, non-setose. Gills present from gnathopod 2 to pereopod 7.

Pleonites 1 to 3 with slight but distinct middorsal ridge. Pleonite 3 with a deep anterodorsal notch. Epimeron 1 anteroventral corner rounded with a few short slender setae. Epimeron 2 ventral margin lined with short fine setae; posteroventral corner produced into sharp spine. Epimeron 3 ventral margin lined with short fine setae; posteroventral corner broadly rounded. Urosomite 1 with anterodorsal notch. Uropod 1 peduncle with 33 dorsolateral, at least 18 dorsomedial and one apicomedial robust setae; outer ramus with at least eight lateral and at least three medial robust setae; inner ramus with five lateral and at least eight medial robust setae [both rami missing distal portion]. Uropod 2 peduncle with 17 dorsolateral and about 10 dorsomedial robust setae; outer ramus with about 15 lateral and seven medial robust setae; inner ramus with at least two lateral and six medial robust setae [both rami missing distal portion]. Uropod 3 peduncle short, length 1.9 times breadth, without dorsolateral flange, with three apicomedial robust setae, without midmedial setae, with four distoventral robust setae, with lightly plumose setae on dorsomedial margin; rami paddle-like, subequal in length, inner ramus about 0.9 times outer ramus; outer ramus two-articulate, article 2 short, article 1 with six lateral and two medial robust setae; inner ramus with one lateral and two medial robust setae, slender plumose setae present on both rami. Telson longer than broad, length 2.3 times breadth, deeply cleft (79%), without dorsal setae, distally tapered, distal margins without setae [but both slightly damaged].

COMPARISON OF THE THREE SPECIMENS

These three specimens differ in many points, most of which are very slight and some of which may be due to difference in overall size. Differences in numbers of setae – for example in the accessory setal row of the mandible, on the inner plate of maxilla 1, on the inner and outer plates of the maxilliped, on the pereopods and on the uropods – are most likely size-related. So too is the development of the dorsal ridge. There are other small differences which do not appear to be size-related – for example the length to breadth of antenna 1 peduncular article 1 in the Milne Edwards specimen is slightly greater than in the other two specimens; the lateral cephalic lobe is slightly more rounded in the Lichtenstein specimen; the epistome is rounded in the Lilljeborg specimen but slightly angular in the Milne Edwards specimen; coxa 4 of the Milne Edwards specimen is slightly longer (relative to its breadth) than in the other two specimens.

The gnathopodal palms vary more than do other characters. Unfortunately neither of the gnathopod 1 dactyli is present in the Lichtenstein specimen, so it is not known if the dactyl overhung the palm or not. The size and shape of the gnathopod 1 palm in the Lichtenstein specimen is very similar to that of the Lilljeborg specimen (small, straight), but that of the Milne Edwards specimen is quite different (very small, convex). It is similar to that illustrated by Bowman & Manning (1972) for material from Guadalupe Island, eastern North Pacific Ocean. No other Eurythenes material that we have seen has this type of gnathopod 1, but it may be similar to that of the material recorded by Thurston et al. (2002) from the Atacama Trench, off northern Chile. The geographically closest specimens of the material recorded below – the large female from Macquarie Island and specimens from French Polynesia – have a small but straight, transverse palm on gnathopod 1, similar to that of the Lichtenstein and Lilljeborg specimens. The gnathopod 2 palm is different in all three specimens: obtuse in the Lichtenstein specimen, slightly obtuse in the Lilljeborg specimen and transverse in the Milne Edwards specimen. There are five illustrations of E. gryllus gnathopods in the literature: Lilljeborg (1865a), Goes (1866), Sars (1891), Bowman & Manning (1972) and Rauschert (1985). They also show a diversity of size and shape in the propodus/palm of both gnathopods. There is no clear pattern to this variation.

It is possible that “ Lysianassa magellanica ” represents a valid species, but until additional material of this form is recognised the name remains a junior synonym.

OTHER MATERIAL EXAMINED. — Australia. E of Flynn Reef, Queensland, RV Sunbird , SEAS, stn QLD-930, 16°37.81’S, 146°23.08’E, 1000 m, baited trap, bottom temperature 5.2°C, 6-7.VI.1993, J. K. Lowry, P. Freewater & W. Vader, 1 immature with short non-setose oostegites, 48 mm ; 2 immature without calceoli, 48 and 51 mm; 3 juveniles 31, 36 and 38 mm ( AM P61826). — Same data, SEAS, stn QLD-931, 20 immature and juvenile specimens 16- 30 mm ( AM P50237). — Same data, SEAS, stn QLD-932, 3 juveniles 16-17 mm ( AM P57605) ; 10 juveniles 16-25 mm ( AM P50242). — Same data, SEAS, stn QLD-948, 23 immature and juvenile specimens 16-48 mm ( AM P50290). — Same data, SEAS, stn QLD-949, 4 juveniles 17-24 mm ( AM P50296). — Same data, SEAS, stn QLD-950, 7 immature specimens 22-28 mm ( AM P61827). — E of Cairns, Queensland, RV Franklin , CIDARIS-1, stn 35.4, 16°54.4’S, 147°14.35’E, 1473-1590 m, beam trawl, 14.V.1986, M. Pichon, P. W. Arnold & R. A. Birtles, 1 without calceoli, 50 mm ; 1 with calceoli, 65 mm ( QM 2684 ) .

Western South Pacific Ocean (material recorded as Eurythenes cf. gryllus in Lowry & Stoddart 1994): New Caledonia. RV Vauban, stn CA-1, 20°44’S, 166°27’E, 1000 m, baited fish trap, A. Intes, 19.II.1977, 2 with calceoli, 52 and 64 mm ; 1 immature specimen 46 mm ( AM P28855) .

Loyalty Islands. W of Lifou, 20°48.12’S, 166°53’E, 1620-1630 m, beam trawl, 1.V.1987, BIOGEOCAL, stn CP 317, 1 without calceoli, 50 mm (MNHN- Am 4403).

French Polynesia. Fangataufa Atoll , Tuamotu Archipelago, 22°16’S, 138°42’W, 900-1000 m, baited trap, J. Poupin, 1 with setose oostegites, 90 mm ; 2 with calceoli, 62 and 78 mm ( AM P42139). — Just off Rapa, Austral Isles, RV Marara, SMCB , stn FRP-54, 27°35.3’S, 144°15.5’W, 870 m, baited trap, J. K. Lowry & J. Poupin, 17-18.VIII.1991, 1 without calceoli, 50 mm ( AM P42138) .

Southern Ocean: Macquarie Island. Bauer Bay, [c. 54°33’S 158°58’E], regurgitated by chick of Lightmantled Sooty Albatross, 3.I.1964, K. G. Simpson, Ser. No. M/64/Ar/1, 1 mature with setose oostegites, 120 mm ( AM P62147).

REMARKS

None of the specimens from trap samples on the east coast of Australia were mature. The largest female (48 mm) was only beginning to develop oostegites. However, the deepest trapset used in the project in which these specimens were caught was at 1000 m depth. This is probably the very top of the species’ bathymetric range in this area. Traps set at shallower depths in the same locality did not collect any Eurythenes .

The very large (120 mm) female from Macquarie Island has a well developed oostegite on gnathopod 1. It is the only specimen in this collection to have five pairs of oostegites. The next largest (90 mm) female, from French Polynesia, has four pairs of long, well developed, setose oostegites but no trace of an oostegite on gnathopod 1.

Eurythenes obesus ( Chevreux, 1905) ( Figs 12-15 )

Katius obesus Chevreux, 1905: 1 , figs 1-3; 1935: 63. — Stebbing 1906: 721. — Tattersall 1906: 29; 1909: 210. — Stephensen 1912a: 89; 1912b: 614; 1913: 123; 1915: 37; 1925: 126; 1933: 12, 13, 18, figs 6, 7. — Shoemaker 1920: 8 E; 1956: 177. — Schellenberg 1926: 217, fig. 26d; 1927: 681, fig. 72; 1931: 16. — K. H. Barnard 1932: 56, fig. 21, pl. 1 fig. 1. — Belloc 1960: 7. — Costello et al. 1989: 32.

Eurythenes obesus – Schellenberg 1955: 183, 192. — Shoemaker 1956: 178. — J. L. Barnard 1958: 92; 1961: 38, fig. 8. — Birstein & Vinogradov 1960: 184; 1962: 36; 1964: 163; 1970: 420 (table 1). — Hurley 1963: 59. — Brusca 1967: 384. — Imber 1973: 652. — Bellan-Santini & Ledoyer 1974: 681, pl. 25. — Griffiths 1975: 145; 1976: 56, 100. — Lowry & Bullock 1976: 89. — Ortiz 1979: 19. — Andres 1983: 186; 1987: 96, 97. — Umezu 1984: 128. — Hopkins 1985: 202. — Costello et al. 1989: 32. — Barnard & Karaman 1991: 486. — Boudrias 1991: 13. — Palerud & Vader 1991: 35. — De Broyer & Jazdzewski 1993: 68. — Kaufmann 1994: 54. — Piatkowski et al. 1994: 19 (table 1). — Thurston & Bett 1995: 201. — Johnson et al. 2001: 198 (table 3). — Cherel et al. 2002a: 268 (table 3); 2002b: 288 (table 3), 292 (table 4).

Eurythenes gryllus – K. H. Barnard 1940: 440, 515 (list). — Springer & Bullis 1956: 6.

Eurythenes gryllus – Stephensen 1932: 356 (in part).

TYPE MATERIAL. — Chevreux’s type specimen of E. obesus , a 12 mm? taken near the Azores, eastern North Atlantic Ocean, is now lost, according to Dr Christian Carpine of the Musée océanographique, Monaco. Because of the increasing complexity of species concepts in the genus Eurythenes it is important to fix the identity of E. obesus and establish the state of characters which are now considered important for delimiting species. Dr M. Thurston of the Southampton Oceanography Centre has made available a mature female specimen, taken near the Cape Verde Islands, eastern North Atlantic Ocean, which we here designate as the neotype for E. obesus . This is the specimen recorded and studied by Thurston & Bett (1995).

Neotype: 48 mm, with setose oostegites and hatchlings ( BMNH 2003.1059 ), RRS Discovery , stn 9541#30, NE of Cape Verde Islands, eastern North Atlantic Ocean, 20°1.8’N, 21°19.8’W- 20°1.3’N, 21°20.0’W, 995-1500 m over bottom depth 3800-3850 m, rectangular midwater trawl RMT 8, 1921-2321 hours, 22.IV.1977.

ADDITIONAL MATERIAL EXAMINED. — Eastern North Atlantic Ocean. RRS Discovery, stn 8508#13, 44°4.3’N, 12°44.7’W- 44°4.8’N, 12°47.9’W, 590- 610 m, rectangular midwater trawl RMT 8, 0551- 0651 hours, 14.IV.1974, with calceoli, 18 mm ( BMNH 2003.1060).

Australia. Western Front, Eddy J, E of Sydney, NSW, 33°33’S, 152°34’E, 271 m, 1835-1935 hours, 2.X.1979, stn SP 10-79, B. Jeffries & R. Fritz, 1 with oostegite buds, 25 mm ( AM P31001). — SE of Montague Island, NSW, FRV Kapala , stn K77-19-01, 36°24’S, 150°18’E- 36°30’S, 150°17’E, 128 m over bottom depth 146 m, midwater trawl, 0900- 1125 hours, 1.XI.1977, 1 with setose oostegites, 80 mm ( AM P30498). — S of Point Hicks, Victoria, RV Franklin, stn SLOPE 38, 38°39.23’S, 149°15.00’E, 1500 m over bottom depth 2900-3200 m, 8 m rectangular midwater trawl, 24.VII.1986, M. F. Gomon et al., 1 with oostegite buds, 24 mm ( NMV J 52806 ). — Off Freycinet Peninsula, Tasmania, RV Franklin, stn SLOPE 42, 42°03.30’S, 148°57.90’E, 900-1000 m over bottom depth 2100-2300 m, 8 m rectangular midwater trawl, 26.VII.1986, M. F. Gomon & L. Hamond, 1 juvenile 16 mm ( NMV J 52807 ). — Off Freycinet Peninsula, Tasmania, RV Franklin, stn SLOPE 44, 42°13.00’S, 148°46.10’E, 500-1000 m over bottom depth 1700 m, 8 m rectangular midwater trawl, 27.VII.1986, M. F. Gomon et al., 1 juvenile 22 mm ( NMV J 52808 ). — 61 km ENE of Cape Tourville, Tasmania, RV Franklin, stn SLOPE 75, 41°58.49’S, 149°04.41’E, 3 m Isaacs-Kidd midwater trawl over bottom depth 1685-2524 m, 28.X.1988, G. C. B. Poore et al., 1 ovigerous 34 mm ; 1 with oostegite buds, 24 mm ( NMV J 52805 ) .

Macquarie Island. Southern Ocean, [c. 54°35’S, 158°55’E], regurgitated by Northern Giant Petrel chick, Macronectes halli, 1970 , G. W. Johnstone, 1 with setose oostegites, 53 mm ( AM P20352).

Southern Ocean. 55°01.9’S, 99°53.7’E, to 1000 m, stn 125, rectangular midwater trawl, 0815-0900 hours, 15.III.1981, J. Kirkwood, 1 with setose oostegites, 50 mm ( AM P62437). — 64°18.3’S, 78°43.9’E, to 980 m, stn 80, rectangular midwater trawl, 1742- 1812 hours, 18.II.1981, J. Kirkwood, 1 juvenile, 16 mm ( AM P62438).

DIAGNOSIS. — Anterodorsal margin of head smooth. Gnathopod 1 parachelate; basis length 2 to 2.5 times breadth; propodus slightly tapering distally. Pereopods 3 to 7 dactyli long. Pereopod 4 coxa as deep as wide. Pereopod 7 basis length of anterior margin subequal to breadth; posteroventral margin rounded. Pleonite 3 with anterodorsal notch. Epimeron 3 posteroventral corner subquadrate. Urosomite 1 not dorsodistally produced over urosomite 2. Uropod 3 peduncle, medial face with robust setae.

DESCRIPTION

Based on neotype female. Head much deeper than long, not extending much below insertion of antenna 2, anterodorsal margin smooth; lateral cephalic lobe small, subacute; rostrum absent; eyes not apparent. Antenna 1 short; peduncular article 1 short, length 1.1 times breadth, distal margin without midmedial tooth; peduncular article 2 short, 0.2 times article 1; peduncular article 3 short; accessory flagellum 11-articulate, article 1 long, 3.3 times article 2; flagellum 25- articulate, with strong two-field callynophore, calceoli absent. Antenna 2 medium length, 1.6 times antenna 1; peduncle without brush setae; peduncular article 1 enlarged, covering article 2 laterally; peduncular article 3 short, 1.3 times article 4; flagellum 46-articulate, calceoli absent.

Mouthpart bundle subquadrate. Epistome and upper lip separate, epistome produced, rounded; upper lip not produced, slightly rounded. Mandible incisors large, symmetrical, with slightly convex smooth margins; lacinia mobilis a long slender distally-cuspidate robust seta; accessory setal row left and right with 10 short, slender, robust setae; intermediate setae pappose; molar large, setose, with vestigial distal triturating patch; palp attached midway; article 1 short, length 1.4 times breadth; article 2 slender, length 3.2 times breadth, 1.1 times article 3, with many submarginal posterodistal A2-setae, without D2- setae; article 3 falcate, long, length 3.2 times breadth, with one proximal A3-seta, with about 44 D3-setae along most of posterior margin, with two apical and four subapical E3-setae. Maxilla 1 inner plate narrow, with eight apical and subapical pappose setae; outer plate narrow, with 11 setal-teeth in 8/3 crown arrangement; ST1 to ST3 large, slender, three- to four-cuspidate, ST4 to ST6 large, slender, four-cuspidate, ST7 slightly displaced from ST6, elongate, slender, ninecuspidate medially; STA large, broad, two-cuspidate; STB to STD large, broad, five- to eight-cuspidate; palp large, two-articulate, with five apical and three apicolateral short robust setae, and four subapical slender seta, flag seta absent, distomedial margin smooth. Maxilla 2 inner and outer plates broad; inner plate length 0.7 times outer plate. Maxilliped inner plate large, subrectangular, with three apical nodular robust setae and three robust setae on lateral face; oblique setal row well developed, with at least 30 pappose setae; outer plate medium size, subovate, with 10 apical pappose setae and three apical robust setae, medial setae small, bead-shaped, submarginal setae vestigial; palp large, four-articulate, article 2 very broad, length 1.8 times breadth, 1.3 times article 3, article 3 long, slen- der, length 2.7 times breadth, dactylus well developed, with five subapical setae, unguis present.

Pereonites 1 and 2 dorsally smooth; pereonites 3 to 7 with sharp dorsal ridge. Gnathopod 1 parachelate; coxa vestigial; basis long, slender, length 2.3 times breadth, anterior margin smooth, with tufts of slender setae; ischium short, length 1.4 times breadth; merus posterior margin lined with long slender setae; carpus wedge-shaped, slightly produced anteriorly, short, length 1.4 times breadth, shorter than (0.7 times) propodus, with long slender setae near posterodistal corner; propodus large, subrectangular, length 2.1 times breadth, slightly tapering distally, posterior margin subtly sinusoidal, smooth, with tufts of slender setae, palm transverse, margin slightly convex, minutely serrate, posterodistal corner with one medial and one lateral robust seta; dactylus simple, without subapical spines or slender setae, reaching beyond corner of palm. Gnathopod 2 minutely subchelate; coxa small, shorter than coxa 3; ischium long, length 3.9 times breadth; carpus very long, length 5.2 times breadth, posterior margin straight; propodus subrectangular, long, length 4.0 times breadth, palm transverse, with convex, minutely serrate margin, with one medial and one lateral robust seta; dactylus not reaching corner of palm, posterior margin smooth. Pereopod 3 coxa large; merus weakly expanded anteriorly; propodus with four groups of slender setae along posterior margin and one posterodistal robust seta; dactylus long, slender. Pereopod 4 coxa deeper than wide (length 1.1 times breadth), with large posteroventral lobe, anterior margin curved; merus weakly expanded anteriorly; propodus with four groups of slender setae along posterior margin and one posterodistal robust seta; dactylus long, slender. Pereopod 5 coxa with anterior and posterior lobes subequal; basis expanded posteriorly, posterior margin smooth; merus expand- ed posteriorly, with sloping posteroproximal margin and straight posterodistal margin; propodus with five short robust setae along anterior margin and two anterodistal robust setae; dactylus long, slender. Pereopod 6 coxa small, not lobate posteriorly; basis expanded posteriorly, posterior margin minutely crenate; merus expanded posteriorly, with curved posterior margin; propodus with five groups of short robust setae along anterior margin and two anterodistal robust setae; dactylus long, slender. Pereopod 7 basis expanded posteriorly, anterior length subequal to breadth, posterior margin slightly rounded, minutely crenate, posteroventral corner subquadrate, posteroventral margin straight; merus expanded posteriorly, with curved posterior margin; propodus with five groups of four to eight short robust setae along anterior margin, two anterodistal robust setae and two pairs of robust setae along posterior margin; dactylus long, slender.

Oostegites present from gnathopod 2 to pereopod 5, long, setose. Gills present from gnathopod 2 to pereopod 7.

Pleonites 1 to 3 with sharp dorsal ridge. Pleonite 3 with an anterodorsal notch. Epimeron 1 anteroventral corner subquadrate with a few short slender setae. Epimeron 2 ventral margin lined with short fine setae; posteroventral corner produced into sharp spine. Epimeron 3 ventral margin lined with short fine setae; posteroventral corner subquadrate. Urosomite 1 with anterodorsal notch, with a dorsal ridge. Uropod 1 peduncle with 34 dorsolateral, 12 dorsomedial and one apicomedial robust setae, without plumose setae; rami subequal in length; outer ramus with 14 lateral and five medial robust setae; inner ramus with seven lateral and eight medial robust setae. Uropod 2 peduncle with 23 dorsolateral, two apicolateral, seven dorsomedial and one apicomedial robust setae; rami subequal in length; outer ramus with 16 lateral and five medial robust setae; inner ramus with nine lateral and nine medial robust setae. Uropod 3 peduncle short, length 1.4 times breadth, without dorsolateral flange, with four apicomedial, three midmedial and six distoventral robust setae, with lightly plumose setae on dorsomedial margin; rami paddle-like, subequal in length, inner ramus about 0.9 times outer ramus; outer ramus two-articulate, article 2 short, article 1 with three lateral and 11 distomedial robust setae; inner ramus with 11 distomedial robust setae; slender plumose setae present on both rami. Telson longer than broad, length 2.4 times breadth, deeply cleft (83%), without dorsal robust setae, distally tapered, without apical setae.

REMARKS

The 80 mm female from SE Australia ( AM P30498) is the largest specimen of E. obesus so far recorded. It has long, setose oostegites but was not carrying eggs or young. The oostegites were flat against the sternum; the gonopore is large and the encircling rim of tissue is soft; this female may have been close to producing a brood. There is no trace of an oostegite on gnathopod 1. This specimen is also notable for where it was captured: at 128 m depth over a bottom depth of 146 m. Although E. gryllus has occasionally been taken at relatively shallow depths such captures have been made over deep water (e.g., three records at 200 m or less recorded by Andres [1983], but over bottom depths of 3000- 4000 m). The previously shallowest recorded bottom depth over which E. obesus has been captured is 950 m ( Andres 1983).

Very little is known of the life habits of E. obesus . It has never been taken in baited traps; has frequently been taken in midwater trawls; and has once been recorded as burrowing into a salp ( Stephensen 1915), once as having coelenterate remains in the stomach ( Hopkins 1985), once with possibly siliceous sponge spicules in the stomach ( Brusca 1967), and once as attacking fish taken in midwater trawls ( Thurston & Bett 1995).

Figures

FIG. 1. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), holotype 81 mm (ZMB 1265).

FIG. 2. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), holotype 81 mm (ZMB 1265). Abbreviations: G1, G2, gnathopods 1, 2; P3-P7, pereopods 3-7. Scale bars: 2.0 mm.

FIG. 3. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), holotype 81 mm (ZMB 1265). Abbreviations: A1, A2, antennae 1, 2; EP1-EP3, epimera 1-3; H, head; T, telson; U1-U3, uropods 1-3. Scale bars: U1-3, T, 2.0 mm; A1, A2, 1.0 mm.

FIG. 4. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), holotype of Lysianassa magellanica H. Milne Edwards, 1848, c. 85 mm, (MNHN-Am 3148).

FIG. 5. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), holotype of Lysianassa magellanica H. Milne Edwards, 1848, c. 85 mm (MNHN-Am 3148). Abbreviations: A1, A2, antennae 1, 2; H, head; LMD, left mandible; MP, maxilliped; MX1, MX2, maxillae 1, 2; ★, lateral view of right mandible; ✪, maxilliped palp completely flattened. Scale bars: 1.0 mm.

FIG. 6. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), holotype of Lysianassa magellanica H. Milne Edwards, 1848, c. 85 mm (MNHN-Am 3148). Abbreviations: G1, G2, gnathopods 1, 2; P3-P7, pereopods 3-7. Scale bars: 2.0 mm.

FIG. 7. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), holotype of Lysianassa magellanica H. Milne Edwards, 1848, c. 85 mm (MNHN-Am 3148). Abbreviations: T, telson; U1-U3, uropods 1-3. Scale bars: 1.0 mm.

FIG. 8. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), material reported as Eurytenes magellanicus by Lilljeborg (1865a), immature 55 mm (MNHN-Am 4479).

FIG. 9. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), material reported as Eurytenes magellanicus by Lilljeborg (1865a), immature 55 mm (MNHN-Am 4479). Abbreviations: A1, A2, antennae 1, 2; H, head; MD, mandible; MP, maxilliped; MX1, MX2, maxillae 1, 2; U1-U3, uropods 1-3; T, telson. Scale bars: A1, A2, 0.5 mm; others, 1.0 mm.

FIG. 10. — Eurythenes gryllus (Lichtenstein in Mandt, 1822), material reported as Eurytenes magellanicus by Lilljeborg (1865a), immature 55 mm (MNHN-Am 4479). Abbreviations: G1, G2, gnathopods 1, 2; P3-P7, pereopods 3-7. Scale bars: 1.0 mm.

FIG. 11. — Recorded distribution of Eurythenes gryllus (Lichtenstein in Mandt, 1822).

FIG. 12. — Eurythenes obesus (Chevreux, 1905), neotype 48 mm (BMNH 2003.1059).

FIG. 13. — Eurythenes obesus (Chevreux, 1905), neotype 48 mm (BMNH 2003.1059). Abbreviations: A1, A2, antennae 1, 2; H, head; MD, mandible; MP, maxilliped; MX1, MX2, maxillae 1, 2. Scale bars: 0.5 mm.

FIG. 14. — Eurythenes obesus (Chevreux, 1905), neotype 48 mm (BMNH 2003.1059). Abbreviations: EP1-EP3, epimera 1-3; G1, G2, gnathopods 1, 2; P3-P7, pereopods 3-7; T, telson; U1-U3, uropods 1-3. Scale bars: 1.0 mm.

FIG. 15. — Recorded distribution of Eurythenes obesus (Chevreux, 1905).