Elasmopus hyperopia, 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 : 594-598

Elasmopus hyperopia sp. nov.

( Figures 5 , 6 )

Type locality

The Blow Holes, Point Quobba, Western Australia (24 ◦ 39 ′ S, 113 ◦ 25 ′ E)

Type material

Holotype, male dissected, 4 slides, 6.3 mm, AM P.83326, The Blow Holes, Point Quobba , Western Australia (24 ◦ 39 ′ S, 113 ◦ 25 ′ E), 0 m, exposed intertidal rock shelf, fine thallus brown alga with epiphytes, 7 January 1984, coll. J.K. Lowry, R. Springthorpe and H.E. Stoddart (WA 443) . Paratypes: 10+ specimens, AM P.79340; 1 dissected male, 3 slides, AM P.83327; 1 dissected male, 3 slides, AM P.83328; The Blow Holes , Point Quobba (24 ◦ 39 ′ S, 113 ◦ 25 ′ E), 0 m, exposed intertidal rock shelf, fine thallus brown alga with epiphytes, 7 January 1984, coll. J.K. Lowry, R . Springthorpe and H.E. Stoddart (WA 443) .

Additional material examined

Western Australia. 10+ specimens, AM P.79394, The Blow Holes, Point Quobba (24 ◦ 39 ′ S, 113 ◦ 25 ′ E), 0 m, exposed intertidal rock shelf, broad thallus brown alga, 7 January 1984, coll. J.K. Lowry , R. T. Springthorpe and H.E. Stoddart (WA 441); 10+ specimens, AM P.79414, Bush Bay, 30 km south of Carnarvon (25 ◦ 10 ′ S, 113 ◦ 39 ′ E), 0 m, extensive shallow sand flats, black sponges covered with algae, epiphytes and sediment, 6 January 1984, coll. H.E. Stoddart (WA 422) ; 10+ specimens, AM P. 79461, west of Rottnest Island (32 ◦ 00 ′ S, 115 ◦ 16 ′ E), exposed reef flat, test of sea urchin Echinometra mathaei Blainville, 1825 , 1 November 1982, coll. D. Jones.

Etymology

Hyperopia is Greek for long sighted. Referring to the subtle sculpturing of the male gnathopod 2 palm, which is more easily distinguishable using the dissecting microscope than when observed under close magnification as a slide mount.

Description

Based on holotype male, 6.3 mm, AM P.83326.

Head. Eyes subovoid; lateral cephalic lobe broad, rounded, anteroventral margin with notch / slit. Antenna 1 longer than antenna 2; peduncular article 1 shorter than article 2, without robust setae along posterior margin; article 2 longer than article 3; flagellum with 17 articles; accessory flagellum minute, bi-articulate. Antenna 2 peduncular article 2 cone gland reaching at least to end of peduncular article 3; article 4 subequal in length to article 5; flagellum with 8 articles. Mandible molar well developed, triturative; accessory setal row with 3 setae; palp 3–articulate, article 1 about as long as broad, shorter than article 2; article 2 subequal to article 3 with several slender setae; article 3 strongly falcate, short (about 2.5 times as long as broad), longer than article 1, with comb of short robust setae along anterodistal margin and 1 apical seta. Lower lip outer lobes with single pair of ducts; mandibular lobes apically rounded. Maxilla 1 inner plate subtriangular with 2 apical plumose setae.

Pereon. Gnathopod 1 coxa anterior margin concave, corner slightly produced, rounded; merus with posterodistal tooth; carpus twice as long as broad, subequal in length to propodus; propodus, anterior margin with rows of long slender setae, medial surface without setal comb, palm acute, convex, entire, defined by posterodistal corner, with posterodistal robust setae. Gnathopod 2 subchelate; basis slender; merus with subquadrate distoventral corner; carpus compressed, lobate, projecting between merus and propodus; propodus expanded, palm about one-third length of propodus, straight, inner margin sculptured, subtriangular distomedial shelf, with group of robust setae, defined by posteroventral corner, without posterodistal robust setae; dactylus closing along and reaching end of palm, apically subacute. Pereopod 4 coxa posteroventral lobe well developed, with subrectangular posteromedial corner. Pereopods 5–6 narrow distally; basis posterior margin smooth, straight, without long slender setae, posteroventral corner broadly rounded; merus and carpus not broadened; carpus and propodus with long, slender setae along anterior margin; dactylar unguis simple. Pereopod 7 basis weakly expanded, without long slender setae, posteroventral corner broadly rounded; carpus and propodus with long, slender setae along anterior margin.

Pleon. Epimera 1–3 posteroventral corner with small subacute tooth, posteroventral margin smooth. Urosomite 1 smooth, without carina. Uropod 1 peduncle with one basofacial seta rami subequal in length; inner ramus about as long as peduncle. Uropod 2 rami subequal; inner ramus subequal in length to peduncle. Uropod 3 rami distally truncated, apical robust setae long and short; inner ramus short (length 1.5 times breadth), slightly shorter than outer ramus, subequal to peduncle. Telson deeply cleft (more than 66%), as long as broad, truncated distally, apical margins concave, each lobe with one short and two long apical robust setae, with two pairs of lateral plumose setae.

Remarks

Based on the overall form of gnathopod 2 with its relatively subtle palmar features, E. hyperopia sp. nov. is similar to E. menurte , E. palu Appadoo and Myers 2003 , E. slatyeri and E. varanocephalensis .

The gnathopod 2 propodus with a well-developed distal shelf separates E. hyperopia sp. nov., E. palu and E. varanocephalensis from E. menurte and E. slatyeri which have a weakly developed distal shelf. The gnathopod 2 propodus palm which is defined by a posterodistal corner and pereopods 5–7 with long slender setae on the anterior and posterior margins separates E. hyperopia sp. nov. from E. palu and E. varanocephalensis , as well as the aforementioned species, where the propodus is acute and the pereopods less setose.

Distribution

Australia. Western Australia: Rottnest Island; Carnarvon (current study).

Figures

Figure 5. Elasmopus hyperopia sp. nov., holotype male, 6.3 mm, AM P.83326, Point Quobba, Western Australia.

Figure 6. Elasmopus hyperopia sp. nov., holotype male, 6.3 mm, AM P.83326, Point Quobba, Western Australia.