Elasmopus otus, Hughes & Lowry, 2011

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 : 608-613

Elasmopus otus sp. nov.

( Figures 12 , 13 )

Type locality

Western side of outer Latitude Rock, Forster, New South Wales, Australia (32 ◦ 12 ′ 39 ′′ S, 152 ◦ 34 ′ 6 ′′ E).

Type material

Holotype male, 7.3 mm, 4 slides, AM P.83323 ; Paratype female, 7.0 mm, 2 slides, AM P.83324; 1 specimen, AM P.77257, western side of outer Latitude Rock , Forster, New South Wales, Australia (32 ◦ 12 ′ 39 ′′ S, 152 ◦ 34 ′ 06 ′′ E), 10 m, barnacle chunks, hand collected on SCUBA, 18 March 2003 , coll. AM party on RV Baragula ( NSW 2166 ) .

Additional material examined

New South Wales. 10+ specimens, AM P.77194, south side of Fish Rock, south of Smoky Cape (30 ◦ 56 ′ 28 ′′ S, 153 ◦ 05 ′ 58 ′′ E), 20.3 m, encrusting matter on wire cable, hand collected on SCUBA, 11 February 2002, coll. K.B. Attwood, P.B. Berents, RV Baragula and RV Sula (NSW 1831) ; 10+ specimens, AM P.77201, northwest corner of Green Island, north of Smoky Cape (30 ◦ 54 ′ 41 ′′ S, 153 ◦ 05 ′ 18 ′′ E), 8 m, ascidians covered with algae and encrustations, hand collected on SCUBA, 15 February 2002 , coll. R.T. Springthorpe , RV Baragula ( NSW 1923 ); 5 specimens, AM P.77197, northwest corner of Green Island, north of Smoky Cape (30 ◦ 54 ′ 41 ′′ S, 153 ◦ 05 ′ 18 ′′ E), 11 m, tunicates and sponge, hand collected on SCUBA, 15 February 2002, coll. S.J. Keable, RV Baragula and RV Sula (NSW 1914) ; 8 specimens, AM P.77294, northeast side of Little Broughton Island, northeast of Port Stephens (32 ◦ 37 ′ 05 ′′ S, 152 ◦ 20 ′ 06 ′′ E), 17 m, rock reef with gutters and sand patches, kelp Ecklonia holdfasts, hand collected on SCUBA, 11 March 2006 , coll. R.T. Springthorpe , RV Baragula ( NSW 2940 ); 9 specimens, AM P.77198, northwest corner of Green Island, north of Smoky Cape (30 ◦ 54 ′ 40 ′′ S, 153 ◦ 05 ′ 17 ′′ E), 8 m, bryozoan ( Orthoscuticella sp.), hand collected on SCUBA, 15 February 2002 , coll. R.T. Springthorpe , RV Baragula and RV Sula (NSW 1916) ; 7 specimens, AM P83325 , southwest side of Boondelbah Island, east of Port Stephens (32 ◦ 42 ′ 30 ′′ S, 152 ◦ 13 ′ 32 ′′ E), 10 m, corallimorphs and red algae on barnacles scraped off large boulder, hand collected on SCUBA, 10 March 2006, coll. A. Murray ( NSW 2917 ) .

Etymology

Named from the wooden screw steamer which was wrecked at Forster in 1923, the type locality of this species.

Description

Based on holotype male, 7.3 mm, 4 slides, AM P.83323.

Head. Eyes subovoid; lateral cephalic lobe broad, truncated, anteroventral margin with notch / slit. Antenna 1 longer than antenna 2; peduncular article 1 subequal in length to article 2, without robust setae along posterior margin; article 2 longer than article 3; flagellum with 19 articles; accessory flagellum unknown. Antenna 2 peduncular article 2 cone gland reaching end of peduncular article 3; article 4 subequal in length to article 5; flagellum with nine articles. Mandible molar well developed, triturative, accessory setal row with three setae; palp tri-articulate; article 1 about twice as long as broad, shorter than article 2; article 2 subequal to article 3, with many slender setae; article 3 strongly falcate, short (twice as long as broad), longer than article 1, with comb of short robust setae along anterodistal margin and three long slender apical setae. Lower lip outer lobes with single pair of ducts; mandibular lobes apically rounded. Maxilla 1 inner plate subtriangular with three apical plumose setae.

Pereon. Gnathopod 1 coxa anterior margin straight, anteroventral corner produced, rounded; merus without posterodistal tooth; carpus twice as long as broad, longer

than propodus, with rows of long slender setae covering surface; propodus anterior margin with rows of long slender setae, medial surface without setal comb, palm acute, straight, entire, defined by posterodistal corner, with posterodistal robust setae. Gnathopod 2 subchelate; basis slender; merus with rounded distoventral corner; carpus compressed, lobate, projecting between merus and propodus; propodus expanded, anterior margin with rows of short slender setae, posterior with rows of long slen- der setae, medial surface with rows of short slender setae, palm acute, smooth, without posterodistal corner or robust setae, subtriangular distomedial shelf with robust setae, palmar margin without robust setae, with short subacute distal subpalmar seam; dactylus closing along and reaching end of palm, apically subacute. Pereopod 4 coxa posteroventral lobe with acute posteromedial corner. Pereopods 5–7 narrow distally; basis posterior margin slightly expanded, castelloserrate, without long slender setae; carpus and propodus with a few long, slender setae along anterior margin; propodus not expanded posterodistally; dactylar ungues simple. Pereopod 5 basis posterior margin straight, posteroventral corner broadly rounded. Pereopod 6 basis posterior margin convex, posteroventral corner with subjugated quadrate flap. Pereopod 7 basis posterior margin convex, posteroventral corner broadly rounded.

Pleon. Epimera 1–3 posteroventral corner subquadrate, notched with small subacute tooth. Urosomite 1–3 smooth, without carina. Uropod 1 peduncle with one basofacial robust seta; rami subequal in length. Uropod 2 rami subequal in length to peduncle; outer ramus shorter than inner ramus. Uropod 3 rami distally truncate; inner ramus short (length 1.8 times breadth), slightly shorter than outer ramus; outer ramus subequal to peduncle. Telson deeply cleft (more than 66%), longer than broad, apical margins straight, each lobe with five long apical robust setae, with pair of lateral plumose setae.

Remarks

Elasmopus otus sp. nov. has a distinct pereopod 6 basis posterodistal corner, which is developed as a quadrate process raised from the main plane of the basis article. The New South Wales species E. arrawarra Hughes and Lowry, 2006 ; E. warra Kelaher and Lowry, 2002 and E. otus sp. nov. appear as a closely related group. The pereopod 6 posterior margin is the most readily identifiable way to separate these species, which is entirely castelloserrate with defined posterodistal corner in E. otus sp. nov., partially castelloserrate in E. arrawarra and without castelloserrate margin in E. warra .

Elasmopus otus sp. nov. is further aligned with the tropical Australian E. pectenicrus , with the gnathopod 1 carpus and propodus anterior margin have rows of long slender setae, gnathopod 2 male propodus have a dense brush of long slender setae on the medial margin and subpalmar seam, pereopods 6–7 basis posterior margins are castelloserrate and the telson shape, cleftness and setation. However the latter species has a poorly defined subquadrate pereopod 6 corner. Elasmopus crenulatus Berents, 1983 also loosely fits into this group but lacks the gnathopod 1 carpus propodus long slender setae on the anterior margin and the pereopods 6–7 margin is more broadly crenulated than minutely castelloserrate.

Distribution

Australia. New South Wales: Forster, Smokey Cape, Port Stephens (current study).

Figures

Figure 12. Elasmopus otus sp. nov., holotype male, 7.3 mm AM P.83323, Latitude Rock, Forster, New South Wales.

Figure 13. Elasmopus otus sp. nov., holotype male, 7.3 mm AM P.83323; paratype female, 7.0 mm, AM P. 83324 Latitude Rock, Forster, New South Wales.