Mallacoota insignis (Chevreux)

Appadoo, Chandani, Myers, Alan A. & Fagoonee, Indur, 2002, The genus Mallacoota (Crustacea, Amphipoda, Melitidae) from Mauritius, with description of a new species, Journal of Natural History 36 (7), pp. 767-796 : 787-791

Mallacoota insignis (Chevreux)

(®gure 13)

Elasmopus insignis Chevreux, 1901: 406 , ®gures 24±31. Walker 1909: 336.

? Elasmopus indicus Pirlot, 1936: 326 .

Maera insignis: Schellenberg, 1938: 50 , ®gure 24; Barnard, 1955: 23; Barnard, 1970: 147, ®gure 89; Sivaprakasam, 1970: 39, ®gure 1h; Ledoyer, 1972: 223, pls 41, 42.

Mallacoota insignis: Barnard, 1972a: 243 ; Ledoyer, 1978: 281, ®gure 31(I); Ledoyer, 1979: 82; Ledoyer, 1982: 552, ®gure 210; Myers, 1985: 117, ®gures 93, 94.

Material examined

5, 5, ®ve juv. from Sargassum densifolium and Ulva lactuca ; 1 from Sargassum densifolium ; 10, one juv. from Acanthophora spicifera, Souillac , 3 February 1998. 1, one juv. from Gelidiella sp. , Klondike, 12 May 1998. 2, two juv. from Sargassum sp. , Dictyota sp. and Turbinaria ornata, Roches Noire , 15 May 1998. 6, 2, 2 two juv. from Centroceras clavulatum and Sargassum sp. , Belle Mare, 16 May 1998. 7, 4, nine juv. from Gracilaria salicornia ; 1 from Amphiroa sp. , Amansia glomerata and Gracilaria millardetii ; 5 9 from Gracilaria salicornia, Souillac , 17 June 1998. 3, 7, 17 juv. from Amansia glomerata ; 3, one juv. from Acanthophora spicifera ; 1, 3, two juv. from Wurdemania sp.; 4, 5 from Sargassum densifolium ; two juv. from Gracilaria corticata, Souillac , 13 August 1998. 3, 7 from Sargassum binderi ; 1, four juv. from Dictyota divaricata, La Cuvette , 28 August 1998. 1, 2 from Gracilaria millardetii ; 1 from Acanthophora spicifera ; 1 from Digenia simplex , Acanthophora spicifera, Souillac , 10 November 1998.

1 from Sargassum sp. Roches Noire, 20 January 1999. 3 from Dictyota divaricata, Roches Noire , 10 February 1999. 1, 13, four juv. from Gracilaria corticata ; 14, 24, 13 juv. from Amansia glomerata and Ulva reticulata ; 2, 9 from Acanthophora spicifera, Souillac , 25 March 1999. 2, 3, eight juv. from Acanthophora spicifera and Centroceras clavulatum ; 2, 10 from Digenia simplex , Gracilaria salicornia and Gelidiella acerosa, Souillac , 8 April 1999. 1, one juv. from Digenia simplex , Dictyota divaricata and Gracilaria salicornia, Roches Noire , 9 April 1999. 7, 9, 10 juv. from Sargassum sp. and Ulva reticulata, La Cuvette , 5 May 1999. 3, 7, four juv. from mixture of Padina and Halimeda sp. , Grand Baie, 5 May 1999. 1, 6, one juv. from Gracilaria corticata , Amansia glomerata , Acanthophora spicifera and Centroceras clavulatum ; 1, 2, seven juv. from Digenia simplex and Halimeda sp. , Souillac, 17 June 1999. 1, one juv. from Digenia simplex , Padina sp. and Gracilaria salicornia, Roches Noire , 21 June 1999. 4, 23, 20 juv. from Sargassum densifolium and Amansia glomerata ; 1, 1, three juv. from Sargassum densifolium and Gracilaria corticata ; 5, 1, one juv. from Digenia simplex, Souillac , 4 August 1999. 4, 6, 12 juv. from Digenia simplex , Padina sp. and Jania adherens, Roches Noire , 6 August 1999. 9, 4, eight juv. from Sargassum sp. , La Cuvette, 12 October 1999. 3, 2, two juv. from Sargassum densifolium , Amansia glomerata , Jania adherens and Digenia simplex, Souillac , 14 October 1999. 2, one juv. from Digenia simplex , Padina sp. , Roches Noire, 15 October 1999. 1, 1 from Padina sp. ; 3 from Padina sp. , Sargassum densifolium , Pocockiella variegata, Bain Boeuf , 13 December 1999. 1, 3, one juv. from Ulva lactuca , Sargassum sp. , Gracilaria corticata and Amansia glomerata, Souillac , 14 December 1999. 3, 3 from coral rubble, Padina sp. , Digenia simplex , Dictyota divaricata and Turbinaria ornata ; 1, 2, seven juv. from Padina sp. , Digenia simplex , Sargassum sp. and Jania adherens, Roches Noire , 16 December 1999.

4, 1 from Padina sp. , Halimeda sp. , Sargassum sp. , Caulerpa sertulariodes , Dictyota divaricata and Digenia simplex, Roches Noire , 24 January 2000. 3, 5, ®ve juv. from coral rubble, Padina sp. , Turbinaria ornata , Caulerpa sertulariodes , Digenia simplex , Pocockiella variegata, Bain Boeuf , 24 January 2000. 7, 1, four juv. from Padina sp. , Gracilaria salicornia , Ulva lactuca , Hypnea sp. and Dictyota divaricata, Choisy , 25 January 2000. 3, 8, ®ve juv. from Sargassum sp. , Ulva lactuca , Digenia simplex and Centroceras clavulatum, La Cuvette , 25 January 2000. 12, 14, nine juv. from Sargassum densifolium , Ulva reticulata , Amansia glomerata and Jania adherens, Souillac , 10 February 2000.

Description

Colour (in formalin). Head and pereon segments 1±7 green anteriorly and white posteriorly. Epimera, urosomites and uropods white.

Male. Length, 7.2 mm. Head with notch below cephalic lobe. Eyes subround and black. Antenna 1 article 1 with three stout robust setae on ventral border and setae on distal; article 2 subequal to 1; article 3, 0.3 times article 1; articles 2 and 3 setose; accessory ¯agellum with three distinct articles; primary ¯agellum 24- articulate. Antenna 2, peduncle article 5, 0.7 times article 4; ¯agellum 11-articulate and subequal to peduncle. Mandible palp three-articulate; article 2, 1.6 times article 1; article 3 subequal to 2 with two terminal setae. Maxilla 1 inner plate with two plumose setae and ®ne setae on lateral margin; outer plate with ®ve serrate robust setae and a two-articulate palp. Maxilla 2 outer plate with distal setae and two robust setae at the base; inner plate with distal setae and some setae extending the lateral margins with a distinctively plumose setule. Maxilliped inner plate with apical and inner marginal setae; outer plate with stout marginal and terminal setae; palp four-articulate, articles 2 and 3 sparsely setose. Lower lip with acute mandibular lobes; inner and outer plates setose; outer plates with four blunt robust setae each. Gnathopod 1 coxa as wide as long, with a patch of setae on ventral margin; basis three times as long as wide, anterior margin with few robust setae, posterior margin with a patch of long setae; ventral margins of carpus and propodus strongly setose; propodus equal to carpus; palm oblique de®ned by a stout robust seta, palmar margin with short setae; dactylus slender and extending beyond palm. Gnathopod 2 robust compared to G1; coxa 1.2 times as long as wide with a small patch of short setae; basis 3.4 times as long as wide, anterior border lined with numerous setae, posterior border with fewer setae; basis and ischium with a small protuberance on distal lobes; carpus with strong robust setae on anterior margins, 2.5 times as wide as long; propodus 2.3 times as long as wide, anterior margin with strong robust setae, posterior margin irregularly toothed with setae concentrated on the ventral margin; dactylus large, curved and extending to about three quarter the length of propodus. Pereopod 3 coxa 1.5 times as long as wide, ventral margin with a small patch of setae (one-quarter the length of coxa); basis three times as long as wide; anterior margin with strong robust setae, posterior margin with few patches of setae; merus expanded posterodistally with patches of setae on margins; carpus and propodus spinous on posterior margin; carpus subequal to propodus; dactylus apically constricted and bearing a setule at constriction. Pereopod 4 similar to pereopod 3, except coxa 1.3 times as long as wide, excavate on posterior margin with very short setae on ventral margin; basis with strong robust setae on anterior margin and a few long setae on posterior margin; propodus 1.3 times carpus. Pereopod 5, coxa bilobed, twice as broad as long; basis 1.3 times as long as wide; merus 1.2 times as wide as long; carpus 1.2 times as long as wide; propodus twice as long as carpus and six times as long as wide. Pereopod 6 basis 1.4 times as long as wide; merus 1.5 times as wide as long; carpus 1.1 times as long as wide; propodus 2.7 times as long as wide and 1.4 times carpus. Pereopod 7 basis 1.1 times as long as wide; merus 1.8 times as wide as long; carpus 1.1 times as wide as long; propodus twice as long as wide and 1.5 times carpus. Epimeron 3 quadrangular. Epimera 1 to 3 have one row of robust setae. Uropod 1 rami equal to peduncle; peduncle spinous. Uropod 2 peduncle equal to outer ramus; inner ramus 0.7 times outer ramus. Uropod 3 rami equal to each other; peduncle 0.8 times rami and with robust setae on inner margin. Telson cleft to base, apical tooth weakly developed; each telson lobe with four long robust setae.

Female. Length, 6.2 mm.

Female antennae and epimeral plates similar to those of males. Gnathopod 1 coxa 1.4 times as long as broad with very short setae on ventral margin; basis anterior margin with few robust setae, posterior margin with a patch of long setae and few patches of short setae; basis and ischium with small protuberance at distal end; carpus subequal to propodus; ventral margin of carpus and propodus with dense patches of setae. Gnathopod 2 coxa twice as long as wide; basis anterior margin with robust setae, posterior margin with numerous setae; propodus 1.5 times length of carpus. Ventral margin of carpus and propodus setose; palm oblique with de®ning tooth; dactylus ®tting palm. Pereopod 3 and 4 similar to male. Pereopod 5, coxa bilobed, basis as long as broad; merus 0.7 times as wide as long; carpus 0.6 times as broad as long; propodus ®ve times as long as wide and 1.7 times carpus. Pereopod 6, basis 0.7 times as broad as long; merus 0.7 times as broad as long; carpus 0.5 times as broad as long; propodus seven times as long as wide. Pereopod 7, basis 1.1 times as long as broad; merus 0.8 times as wide as long; carpus 0.6 times as wide as long; propodus eight times as long as broad and 1.6 times carpus. Uropods and telson similar to those of male.

Remarks

Mallacoota insignis males range from 3.5 to 8.8 mm and females from 3.8 to 6.7 mm in size. Mallacoota insignis collected in this study agrees with the description given by Ledoyer (1982). The exact location of teeth on the margin of the propodus of gnathopod 2 varies with age (see Ledoyer, 1982, ®gure 210). The Mallacoota insignis reported by Ledoyer (1978) was most probably smaller than the adult specimen described here.

The species is distinguished from other Mallacoota species of Mauritius by its distinctively enlarged merus and carpus of pereopod 6 and pereopod 7. The less setiferous peduncular article 1 of antenna 1 helps to distinguish it from M. caerulea and M. schellenbergi .

Mallacoota insignis appears to be the most widely distributed Indo-Paci®c Mallacoota species. In Mauritius it has previously been recorded by Ledoyer (1978) and Appadoo and Steele (1998) and in this study it has been recorded from several sites of the island.

Habitat. Mallacoota insignis is a widespread species among algae and mixtures of algae and coral rubble in the intertidal and shallow-subtidal zones, at depths less than 1 m, of Mauritius. It is fairly common among the red algae, Amansia glomerata , Centroceras clavulatum , Digenia simplex , Gracilaria salicornia , and among the brown alga Sargassum sp. It occurs both at shores of low wave action, for example, Grand Baie, Belle Mare, Bain Boeuf, Choisy, and at shores of heavy wave action, for example, Roches Noire and Souillac.

Type locality. MaheÂ, Seychelles .

Distribution. Madagascar, Mauritius, Seychelles, India, Indonesia, Philippines, Fiji Kiribati, Tarawa, Hawaii.