Mallacoota nananui Myers, 1985

Lowry, J. K. & Hughes, L. E., 2009, Maeridae, the Elasmopus group *, Zootaxa 2260 (1), pp. 643-702 : 680-684

Mallacoota nananui Myers, 1985

( Figs 21 , 22 )

Mallacoota subcarinatus . — Ledoyer, 1984: 72, fig. 34.

Mallacoota nananui Myers, 1985: 121 , fig. 95. — Myers, 1986a: 1389, fig. 8. — Myers, 1986b: 277, fig. 8. — Springthorpe & Lowry, 1994: 26 (catalogue). — Lowry & Springthorpe, 2005: 267.

Material examined. 2 unsexed, AM P78037 ( QLD 1319 ); 4 unsexed, AM P75755 ( QLD 1909 ); 1 unsexed, AM P75621 ( QLD 1916 ); 1 unsexed, AM P75754 ( QLD 1917 ); 2 unsexed, AM P75753 ( QLD 1983 ); 2 unsexed, AM P75752 ( QLD 1985 ); 1 male , 9.0 mm, 5 slides, AM P78036 ( QLD 1986 ); many unsexed, AM P75629 ( QLD 1986 ); 7 unsexed, AM P75630 ( QLD ( QLD 2000 ); many unsexed, AM P75631 ( QLD 2004 ).

Type locality. Nananui Ra , Viti Levu , Fiji (~ 17°18’S 178°13’E) .

Description. 1 male, 9.0 mm, AM P78036.

Head. Head eyes ovate; lateral cephalic lobe broad, truncated, anteroventral margin with notch/slit, anteroventral corner rounded. Antenna 1 longer than antenna 2; peduncular article 1 subequal in length to article 2, with 1 robust seta along posterior margin; article 2 longer than article 3; accessory flagellum short, with 5 articles; flagellum with 22 articles. Antenna 2 peduncular article 4 longer than article 5; flagellum with 9 articles. Mandible incisor a smooth cutting edge with 2 apicomedial cusps; accessory setal row with 3 setae; palp reduced, 3-articulate; article 1 about as long as broad, shorter than article 2, inner margin article 1 not produced distally; article 2 subequal to article 3; article 3 long (more than 3 x as long as broad), rectolinear, longer than article 1.

Pereon. Gnathopod 1 coxa anteroventral corner produced, rounded, anterior margin concave; merus without posterodistal tooth; carpus about 2 x as long as broad, subequal in length to propodus (length 0.9 x propodus), setae in anterodistal bunches and along posterior margin; propodus palm acute, convex, entire, defined by posterodistal corner, with posterodistal robust setae. Gnathopod 2 coxa posteroventral corner notch absent; basis slender; merus with rounded distoventral corner; carpus compressed, projecting between merus and propodus, length 0.5 x breadth; propodus massive, without setal bunches along grossly sinusoidal posterior margin, palm acute, sinusoidal, sculptured, palm about half length of propodus, with subquadrate distomedial shelf, without group of robust setae on shelf, with shallow midmedial excavation, palmar margin without robust setae, without teeth along margin, subpalmar surface smooth, defined by posteroventral corner, without posterodistal robust setae; dactylus reaching end of palm, closing across margin of palm, without setae on anterior margin, without posteroproximal shelf, apically truncated, hammer-like. Pereopods 5–7 broad distally. Pereopod 4 coxa posteroventral lobe slightly developed, with subacute posteromedial corner. Pereopod 5 basis expanded, posterior margin straight, without long slender setae, posteroventral corner broadly rounded. Pereopod 6 basis posterior margin straight, without long slender setae, posteroventral corner produced distally, lobate; carpus and propodus with few long, slender setae along anterior margin; merus and carpus broadened; propodus expanded posterodistally to from a hood-like projection. Pereopod 7 basis posterior margin convex, smooth or minutely castelloserrate, without long slender setae, produced posterodistally (lobate), posteroventral corner broadly rounded; merus and carpus broadened; propodus expanded posterodistally to from a hood-like projection.

Pleon. Pleonites 1–3 dorsally smooth, without setae, spines or carinae. Epimeron 1 posteroventral corner with small acute or subacute spine. Epimeron 2 posteroventral corner acute. Epimeron 3 ventral margin smooth, posteroventral margin smooth, posteroventral corner with small acute spine. Urosomite 1 bicarinate, subtriangular. Urosomites 2–3 dorsally smooth, without setae, spines or carinae. Uropod 1 peduncle with basofacial robust seta. Uropod 3 rami distally truncated, apical robust setae long; inner ramus subequal in length to outer ramus; inner ramus short (length 1 to 1.9 x breadth); outer ramus long (length 2.4 x breadth), subequal to peduncle, 1-articulate. Telson moderately cleft (30 to 65%), broader than long, tapering distally, apical margins concave, apical conical extension reaching at least halfway along longest seta, without dorsal robust setae, each lobe with 4 long and short apical robust setae, without robust setae on inner and outer margins.

Habitat. Marine, epibenthic, littoral (1.5 – 3 m), on green algae, Halimeda and Caulerpa , on red and brown algae.

Remarks. Myers (1986b: 277, fig. 8b) considered that the reports of M. subcarinata from New Zealand ( Chilton 1915; J.L. Barnard 1972b) and from New Caledonia ( Ledoyer 1984) were M. nananui . But the toothed corner and straight posterior margin of the male gnathopod 2 propodus and lack of a basofacial seta on the peduncle of uropod 1, indicates that the New Zealand records represent an unnamed species that is more similar to M. latidactylus Ledoyer, 1983 . The report of M. subcarinata (phénotype de l'herbier) by Ledoyer (1984) from intertidal seagrasses at I’îlot Maître, New Caledonia appears to be M. nananui .

Mallacoota nananui is a distinctive species that can be differentiated from other species on the GBR by the massive propodus on the male second gnathopod with its characteristic sinusoidal posterior margin and hammer-like dactylus.

Distribution. Australia. Queensland: Heron Island; One Tree Island (current study). New South Wales: Lord Howe Island ( Lowry & Springthorpe 2005). Fiji: Viti Levu ( Myers 1985). New Caledonia. I’îlot Maître ( Ledoyer 1984). Tonga. ( Myers 1986b).

Figures

FIGURE 21. Mallacoota nananui Myers, 1985, male 8.0 mm, AM P78036, One Tree Island, Great Barrier Reef.

FIGURE 22. Mallacoota nananui Myers, 1985, male 8.0 mm, AM P78036, One Tree Island, Great Barrier Reef.