Nuuanu rectimana, Appadoo & Myers, 2005

Appadoo, C & Myers, AA, 2005, Amphipods of the Genera Ceradocus, Dulichiella, Melita and Nuuanu (Crustacea: Melitidae) from Mauritius, Indian Ocean, Records of the Australian Museum 57, pp. 221-236 : 235-236

Nuuanu rectimana n.sp.

Figs. 9–10

Nuuanu sp. 1 (Appadoo & Steele, 1998).

Type material. HOLOTYPE 3, 4 mm, AM P60905, 0.5–1 m depth, living on mixture of Enteromorpha flexuosa , Laurencia papillosa , Halodule uninervis, Poste La Fayette (20°08.2'S 57°44.5'E), Mauritius, C. Appadoo, 7 February 2000. PARATYPES: 13, 3♀♀, AM P60906, 0.5 m, living among Gracilaria salicornia, Souillac (20°31'S 57°30.7'E), Mauritius, 25 March 1999; 13, 1 juv. from green filamentous algae and Halodule uninervis Albion (20°13'S 57°23.7'E), 12 May 1998; 13 from Sargassum sp. , Bain Boeuf (19°59'S 57°36'E), 15 May 1998; 13 from Sargassum sp. , Bain Boeuf, 16 June 1998; 1 juv. from Jania sp. and Valonia sp. , Bain Boeuf, 28 July 1998; 1 juv. from Pocockiella variegata and Valonia sp. , Balaclava (20°03.7'S 57°30.7'E), 10 September 1998; 1 juv. from Gracilaria salicornia, Souillac , 25 March 1999; 233, 11♀♀, 5 juv. from Laurencia papillosa and Cladophora sp. , Albion, 20 April 1999; 1 juv. from Sargassum sp. , Amphiroa sp. , Pocockiella variegata and Cymodocea sp. , Bain Boeuf, 16 June 1999; 13, 2 juv. from Sargassum sp. , La Cuvette, 12 October 1999; 1♀ from coral rubble, Padina sp. and Pocockiella variegata , Flic-en-Flac, 10 December 1999; 1♀ from mixture of Padina sp. , Turbinaria sp. , Sargassum sp. , Pocockiella variegata, Bain Boeuf , 24 January 2000; 1 juv. from mixture of Enteromorpha flexuosa , Laurencia papillosa and Halodule uninervis, Poste La Fayette , 7 February 2000.

Description. Male length, 4.0 mm. Head with lateral cephalic lobe notched; ommatidia of eyes sparse. Antenna 1 poorly setiferous, peduncle article 2 slightly longer than article 1; article 3, 0.5× article 1; accessory flagellum 4- articulate, primary flagellum 30-articulate. Antenna 2 poorly setiferous, article 5, 0.8× article 4, flagellum 20-articulate. Mandible palp slender, subfalcate, article 2 longest; article 3, 0.8× article 2 and 2.1× article 1; article 3 with short setae on medial margin and three long terminal setae. Maxilla 1 palp 2-articulate, article 2 with stout blunt robust setae at tip; inner plate with a small protuberance at apex and with long marginal setae. Maxilla 2 inner plate with oblique setal row. Gnathopod 1 coxa 1.5× as long as broad, posterodistal margin with a notch and distal margin with very short setae; basis slender, 3× as long as broad, posterior margin with a strong patch of setae; carpus slender, subrectangular, 3.5× as long as broad; propodus 0.6× length of carpus; palmar margin oblique with few setae; dactylus short, fitting palm. Gnathopod 2 coxa subrectangular 1.6× as long as broad, posterodistal margin with notch and distal margin with very few short setae; basis 2.5× as long as broad; carpus over three and half times as broad as long; propodus subrectangular, posterior margin straight, defined by a small hump at the proximal end and well-developed blunt projections embedded at the distal end, densely setose, palm obsolete, dactylus 0.6× length of propodus, robust and broad throughout its length. Pereopod 3 coxa subrectangular, 2.2× as long as broad, posterodistal margin with notch; dactylus with two long stout setae and one small slender seta close to apical unguis. Pereopod 4 coxa 1.7× as long as broad, posterior margin excavate; other features similar to pereopod 3. Pereopod 5 basis 1.3× as long as broad, anterior margin convex and with stout robust setae, posterior margin serrated, convex proximally and concave distally; propodus subequal to carpus; dactylus with 2 long setae and one slender seta at unguis. Pereopod 6 basis about 1.5× as long as broad, similar to that of pereopod 5 except posterior margin is more castelloserrate. Pereopod 7 basis broadly expanded, about as long as broad, anterior margin with robust setae, posterior margin strongly convex, castellate with short setae; propodus slightly longer than carpus. Pleonites 1 and 2 with well-developed dorsal tooth. Epimera 1 to 3 subrectangular, distal margins smooth. Uropod 1 rami subequal to each other and 0.8× the length of peduncle. Uropod 2 rami subequal to each other, and slightly longer than peduncle, with stout robust setae. Uropod 3 peduncle 1.5× as long as broad; outer ramus 2-articulate, article 1 truncate with a stout robust setae on mid-lateral margin and two stout distal robust seta; article 2 produced with a stout robust seta; inner ramus short and sub-falcate; inner margins of both rami with very fine short setae. Telson cleft to 80% its length; telson lobes with broadly rounded apex, each with one plumose seta and two short slender setae.

Female: length, 4.2 mm (mature, oostegites with setae). Gnathopod 1 coxa 1.7× as long as broad, posterodistal margin with a notch and short setae; basis slender, 3.5× as long as broad; anterior margin with patches of setae, posterior margin with one strong patch of setae; propodus 0.7× length of carpus; palmar margin oblique, with short setae; dactylus stout, fitting palm. Gnathopod 2 coxa 2.1× as long as broad, posterodistal margin with notch and short setae; basis slender and 3.6× as long as broad; propodus 1.2× length of carpus; propodus slightly less 3.5× as long as broad, palmar margin oblique, defined by a stout robust seta; dactylus stout, fitting palm.

Remarks. The genus Nuuanu , established by Barnard (1970), belongs to the “ Gammarella ” group, recently revised by Lowry & Watson (2002). Males of Nuuanu rectimana n.sp. can easily be distinguished from Nuuanu amikai Barnard (1970) , recorded by Ledoyer (1978) from Mauritius, by the presence of a well-developed flat-topped processes on the propodus of gnathopod 2. Other differences include the shape, setation and spination of the telson. Nuuanu rectimana n.sp. telson is symmetrical with two robust setae and one plumose seta on each lobe whereas in Nuuanu amikai Barnard (1970: 167 , fig. 105) the telson is asymmetrical, with one robust seta and two plumose setae on one lobe and one plumose seta on the other. In addition in Nuuanu rectimana n.sp. the inner lobe of uropod 3 is slender, subfalcate and about half the left of the outer lobe whereas in N. amikai ( Barnard 1970: 168, fig. 106) the inner lobe is triangular and less than half the length of the outer ramus. Nuuanu rectimana n.sp. differs from Nuuanu numbadi Barnard (1974: 39 , fig. 27) from Australia by having more distally tapered telson lobes with one robust and two plumose setae as compared to more distally broad telson lobes with two robust and one plumose seta. Another difference is that epimera 2 and 3 are less acute in N. rectimana n.sp. than in N. numbadi .

Habitat. Nuuanu rectimana was collected in depths of less than 1 m, from seagrass ( Halodule uninervis or Cymodocea sp. ) mixed with other algae and coral rubble at Albion, Poste La Fayette and Bain Boeuf.

Type locality. Poste La Fayette , Mauritius .

Distribution. Mauritius.

Etymology. The species is named from the Latin rectus meaning straight and manus meaning hand, referring to the straight posterior margin of the propodus of the male gnathopod 2.

ACKNOWLEDGMENTS. We are grateful to the University of Mauritius and the Tertiary Education Commission for their support in carrying out the current study. Thanks also due to University of Mauritius (Higher Technical Education Plan) for fully sponsoring visits of one of us (C.A.) to University College Cork, Ireland. We are also deeply indebted to Prof. I. Fagoonee for his support in carrying out this study. We thank Prof. J. Davenport and the staff of the Department of Zoology at University College Cork, for their hospitality and support. The authors are also grateful to Dr J.K. Lowry of the Australian Museum for allowing us access to unpublished manuscripts and for critical appraisal of the manuscript.