Exampithoe (Melanesius) latibasis, Appadoo & Myers, 2004

Appadoo, C & Myers, A. A., 2004, Corophiidea (Crustacea: Amphipoda) from Mauritius, Records of the Australian Museum 56 (3), pp. 331-362 : 345-347

Exampithoe (Melanesius) latibasis n.sp.

Figs. 13–15

Perampithoe falsa.—Appadoo & Steele, 1998: 639; non K.H. Barnard, 1932.

Type material. HOLOTYPE 3, 3.3 mm, AM P65850, from Padina gymnospora and coral rubble, La Prairie (20°29'S 57°20.5'E), at depth less than 1 m, C. Appadoo, 14 October 1999. PARATYPES, 1♀, 3.3 mm, AM P64452, same data as holotype; 13, 3.3 mm, AM P64453, from Sargassum sp. , Roches Noires (20°6.2'S 57°44.5'E), 20 January 1999; 13, AM P60640, 333 and 2♀♀, AM P60641, from Sargassum sp. , Gelidiella acerosa and Ulva reticulata, Souillac (20°31'S 57°30.7'E), 14 December 1999; 233, AM P60642, from Amansia glomerata and Padina sp. ; 13, 9♀♀, 1 juv., AM P60643, from Sargassum sp. , Souillac (20°31'S 57°30.7'E), 8 April 1999; 333, 6♀♀, AM P60644, from Sargassum sp. , La Cuvette (20°00'S 57°34.2'E), 12 October 1999; 1♀, AM P60645, from Sargassum densifolium , Amansia glomerata , Jania adherens, Souillac , 14 October 1999.

Description. Male, 3.3 mm. Head longer than deep, distoventral corner excavate; eyes small, round, pink (in alcohol). Antenna 1 article 2, 0.7× article 1; article 3, 0.25× article 1; accessory flagellum absent; primary flagellum 32- articulate and bearing aesthetacs. Antenna 2 peduncle article 5, 0.9× article 4, flagellum poorly setiferous and 21-articulate. Mandible palp absent. Lower lip outer lobe wide, mandibular lobe rounded. Maxilla 1 inner plate small and triangular, with one seta. Maxilla 2 inner and outer plates narrow with long slender terminal setae. Maxilliped palp article 2 broad, unguis minutely serrate; article 4 small. Gnathopod 1 slightly larger than gnathopod 2; coxa 1.2× as logs as broad, anterodistal margin rounded, unproduced; basis 2.5× as long as broad, anterodistal lobe well developed, with one seta; carpus 1.5× as long as broad; propodus 2.1×as long as broad, palm small and transverse with one robust setae at base, followed by an excavation and a large robust seta; dactylus strongly overlapping palm, 1.6× the length of palm, inner margin smooth with few short fine setae. Gnathopod 2 coxa subquadrate, posterodistal margin with a few slender setae; basis 3× as long as broad, anterodistal lobe moderately developed; carpus slender, 2.2× as long as broad; propodus subrectangular, 2.5× as long as broad, palm transverse with one robust seta at its base; dactylus strongly overlapping palm, inner margin smooth. Pereopods 3–4 coxa subquadrate, with few slender setae on posterodistal margin; basis strongly expanded, 2× as long as broad; merus 1.5× as long as broad, anterior margin strongly expanded; carpus 1.7× as long as broad; propodus 1.2× as long as carpus. Pereopod 5 basis weakly expanded, 1.7× as long as broad; carpus 0.8× merus, subrectangular, 1.7× as long as broad; propodus slightly expanded distally, 4× as long as broad, with three robust setae on palm, one of which is curved. Pereopods 6–7, basis weakly expanded, 1.7× as long as broad; carpus subrectangular, 0.8× merus, 2.3× as long as broad; propodus slightly expanded distally, 3.5× as long as broad, with three

Female: 3.3 mm (ovigerous). Gnathopod 1 similar in size to gnathopod 2; coxa subquadrate; basis 3× as long as broad, with weakly developed anterodistal lobe; carpus 2.4× as long as wide; propodus subrectangular, 2.3× as long as wide, palmar margin small and transverse, dactylus strongly overlapping palm. Gnathopod 2 coxa subquadrate; basis 3× as long as broad; carpus 2.4× as long as broad; propodus subrectangular, 2.5× as long as broad, palm small; dactylus overlapping palm, 1.6× its length, inner margin smooth.

Distribution. Mauritius.

Habitat. This species lives mostly amongst the brown alga Sargassum sp. It was collected at depths of less than 1 m from four sites, Souillac, La Prairie, La Cuvette and Roches Noires.

Remarks. Exampithoe (Melanesius) latibasis n.sp. differs from E. (M.) cooki Ledoyer (1984) in having the male gnathopod 1 with a slender propodus with a short palm, followed by an excavation on the posterodistal margin. In E. cooki , the propodus is subovate and the posterodistal margin almost straight. The shape of the male gnathopod 1 propodus also distinguishes it from E. (M.) kutti Poore & Lowry (1997) , where the palmar margin is convex in both males and females.

Etymology. From the Latin latus meaning wide and referring to the expanded flattened bases of pereopods 3–4.

Material examined. 13, 1♀, 1 juv., AM P60646, from Digenia simplex, Albion (20°13'S 57°23.7'E), 22 October 1998 ; 233, 5♀♀, 4 juv., AM P60647, from Pocockiella variegata , Padina sp. and coral rubble, Flic-en-Flac (20°16.5'S 57°21.7'E), 5 April 1999 ; 333, 4♀♀, 4 juv., AM P60648, from Turbinaria ornata and Pocockiella variegata , Flic-en-Flac, 27 January 2000 .

Diagnosis. Antenna 1 accessory flagellum 6-articulate. Coxae 1–4 with one patch of setae on distal margin. Gnathopod 1 larger and more robust than gnathopod 2; propodus 1.3× as long as broad, palmar margin with a deep excavation. Gnathopod 2, propodus 1.9× as long as broad, palm oblique. Uropod 1 with large acute disto-ventral spur. Uropod 3 outer ramus with one straight and one weakly curved seta at distal end. Telson distally truncate, with welldeveloped patches of slender setae.

Type locality. Seychelles .

Distribution. Madagascar, Mauritius, Seychelles.

Habitat. This species lives mostly amongst red and brown algae and was collected at depths of less than 1 m. It was collected mostly from sites on the west and northwest coasts such as Flic-en-Flac, Albion, and Balaclava.

Remarks. The fact that Paragrubia vorax is readily distinguished from other ampithoids by the strongly enlarged gnathopod 1 in males has led to the species being recorded from many parts of the Indo-Pacific. It is probable that more than one species exists in the Paragrubia vorax complex. The material from Mauritius agrees with the description given by Chevreux (1901) from Seychelles (type locality) and also with that of Ledoyer (1982) in having a strongly excavate palm on the male gnathopod 1 propodus. Material described by J.L. Barnard (1970) from Hawaii and by Myers (1985a) from Fiji has a weakly excavate palm on the male gnathopod 1 and should probably be raised to the status of a new species.