Elasmopus spinidactylus Chevreux, 1907

Hughes, L. E. & Lowry, J. K., 2011, The genus Elasmopus (Crustacea: Amphipoda: Maeridae) in Australian waters, Journal of Natural History 45 (9 - 10), pp. 579-628 : 617-619

Elasmopus spinidactylus Chevreux, 1907

( Figure 16 )

Elasmopus spinidactylus Chevreux, 1907: 414 . Chevreux, 1908: 486, figs. 9, 10. Walker, 1909: 336. Schellenberg, 1938: 55. Shoemaker, 1942: 13. J.L. Barnard, 1965: 504. J.L. Barnard, 1970: 136, figs. 81, 82. Sivaprakasam, 1968: 104, fig. 8. Sivaprakasam 1969: 50, fig. 6g, h. Ledoyer, 1972: 223, pl. 40. Ledoyer, 1983: 482, fig. 183. Myers, 1985: 108, fig. 86. Ren, 1994:263, fig.11. Appadoo and Steele, 1998: 639. Soares et al., 1987 / 89: 248, 249. Appadoo and Myers, 2003: 74 , fig. 11. Horton, 2008: 837 .

Type locality

Makapou Island , Gambier Archipelago .

Material examined

Tasman Sea. Male specimen dissected, 8.1 mm, 1 slide, AM P.83317, (LHA-48); female dissected, 6.0 mm, 1 slide, AM P.83318 (LHA-48); 12 specimens, AM P.76742, Old Gulch , Lord Howe Island (31 ◦ 30 ′ 48 ′′ S, 159 ◦ 02 ′ 48 ′′ E), intertidal, lower sides of lower littoral boulders, 17 May 1977, coll. G.D. Fenwick, (LHA-48) ; 1 specimen, MAGNT Cr 016958, Hunter Point, Emily Bay, Norfolk Island (29 ◦ 3 ′ 47 ′′ S, 167 ◦ 57 ′ 17 ′′ E), 0–0.25 m, 18 April 1984, coll. H.K. Larson ; 1 specimen, MAGNT Cr 016955, Cascade, Norfolk Island (29 ◦ 1 ′ 30 ′′ S, 167 ◦ 58 ′ E), 0–0.25 m, 17 April 1984, coll. H.K. Larson.

Indian Ocean. 10+ specimens, AM P.82188, Lily Beach , Christmas Island (10 ◦ 28 ′ 1 ′′ S, 10 ◦ 42 ′ 40 ′′ E), intertidal pool on platform, November 1978, coll. J. Tranter.

Description

Based on male, 8.1 mm, 1 slide, AM P.83317.

Head. Eyes subovate; lateral cephalic lobe broad, truncate, anteroventral corner rounded, margin with anteroventral notch / slit. Antenna 1 longer than antenna 2; article 1 without robust setae along posterior margin; flagellum with 16 articles; accessory flagellum minute, bi-articulate. Antenna 2 peduncular article 2 cone gland reaching beyond end of peduncular article 3; article 4 longer in length than article 5; flagellum with seven articles. Mandible molar well developed, triturative; palp well developed, tri-articulate; article 1 about twice as long as broad, shorter than article 2; article 3 strongly falcate, short (twice as long as broad), with comb of short robust setae along anterodistal margin and three apical setae.

Pereon. Gnathopod 1 coxa anterior margin slightly concave, anteroventral corner produced, rounded; merus with sharp posterodistal tooth; carpus as long as broad, shorter than propodus; propodus anterior margin without setae, medial surface with setal comb, palm acute, convex, entire, defined by posterodistal corner, with posterodistal robust setae. Gnathopod 2 subchelate; propodus expanded, posterior margin and medial surface with rows of slender setae, palm extremely acute without corner, about half length of propodus, convex, smooth, distomedial shelf subtriangular with four robust setae, palmar margin without robust setae, medial surface with obtuse, subacute projection, reaching beyond propodus palm margin, without posteroventral corner or posteroventral robust setae; dactylus closing across margin of palm, reaching end of palm, with small posteroproximal shelf, apically subacute. Pereopod 4 coxa posteroventral lobe absent, posterior margin concave. Pereopods 5–7 narrow distally; basis posterior margin minutely crenulated, without long slender setae; merus and carpus not broadened; propodus not expanded posterodistally; dactylus anterior margin with three to five undulating processes, ungues simple. Pereopod 5 basis straight; carpus and propodus without slender setae along anterior margin. Pereopod 6 basis posterior margin straight, posterodistal corner produced as subquadrate to subacute lobe, extending below ischium. Pereopod 7 basis posterior margin convex.

Pleon. Epimera 1–2 posteroventral corner with small subacute spine. Epimeron 3 ventral margin smooth, posteroventral margin with a few broad serrations, corner with small subacute tooth. Urosomite 1 smooth, without carina. Uropod 1 peduncle with one basofacial robust seta. Uropod 2 inner ramus longer than peduncle, longer than outer ramus. Uropod 3 rami distally truncated, apical robust setae short; inner ramus narrow (length twice breadth), shorter than outer ramus; outer ramus subequal to peduncle. Telson moderately cleft (30–66% cleft), broader than long, lobes apically truncated, each lobe with two long and one short apical robust setae, with pair of lateral plumose setae.

Female (sexually dimorphic characters). Based on AM P.83318, 6.0 mm. Gnathopod 2 propodus expanded, subovoid, palm smooth, extremely acute without corner, subrectangular distomedial shelf with five robust seta.

Remarks

This species has a broad Indo-Pacific distribution. It is well illustrated by previous authors and a comparison between drawings shows no considerable variation. These are the first records of E. spinidactylus from Australian waters.

Distribution

Australia: Tasman Sea, Lord Howe Island (current study); Norfolk Island (current study). South Pacific. French Polynesia: Gambier Archipelago ( Chevreux 1908); Micronesia ( Barnard 1965); Fiji ( Myers 1985). North Pacific: Hawaii ( Barnard 1970). West Atlantic: Venezuela ( Shoemaker 1942; Soares et al. 1987 / 89). Indian Ocean: Chagos Archipelago ( Walker 1909); Christmas Island (current study).

Figures

Figure 16. Elasmopus spinidactylus Chevreux, 1907, male, 8.1 mm AM P.83317, Old Gulch, Lord Howe Island, Tasman Sea.