Mallacoota caerulea, Appadoo & Myers & Fagoonee, 2002

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 : 768-776

Mallacoota caerulea n. sp.

(®gures 2± 5)

Mallacoota sp. 1 Appadoo and Steele, 1998: 639.

Type material. HOLOTYPE: male 6.0 mm from mixture of Padina boryana Thivy , Ulva lactuca Linnaeus , Hypnea cornuta (Kutzing) J. Agardh, Tamarin (20ss19.5¾S 57ss22¾E), 2 August 1999, AM P60091. PARATYPES: two males, same data as holotype, AM P60092; four males from Hypnea cornuta , Amphiroa X agilissima (Linnaeus) Lamouroux, Caulerpa sertulariodes (Gmelin) Howe and Padina sp. , Tamarin, 18 June 1999, AM P60093; seven males from mixture of Amphiroa X agilissima, Enteromorpha X exuosa (Wulfen) J. Agardh and Ulva lactuca, Tamarin , 2 August 1999, AM P60094; two males, 12 females from mixture of Enteromorpha X exuosa and Sargassum densifolium Zanardini, Tamarin , 11 October 1999, AM P60095.

Additional material. 2, 2, two juv., from Sargassum densifolium ; 1, two juv., from mixture of Sargassum densifolium and Gelidiopsis sp. ; 1, 1, one juv., from Gracilaria corticata J. Agardh ; one juv. from mixture of Ulva reticulata Forskal and Sargassum densifolium ; 1, one juv. from Acanthophora spicifera (Vahl) Borgesen ; one juv. from Sargassum densifolium and Ulva reticulata ; 1, 1, three juv. from Ulva reticulata and Sargassum sp. , Souillac, 3 February 1998. 2, 1, four juv. from Sargassum sp. , La Cuvette, 14 May 1998. 6, 6, eight juv. from Amphiroa sp. , Amansia glomerata C. Agardh and Gracilaria millardetii J. Agardh, Souillac , 17 June 1998. 2, 2 from Amansia glomerata ; two juv. from Gelidiopsis sp. ; 4, 4, four juv. from Digenia simplex (Wulfen) J. Agardh , 13 August 1998, Souillac. Two juv. from Eucheuma sp. , 27 October 1998, Souillac. 14, 7, one juv. from Acanthophora spicifera, Souillac , 10 November, 1998.

1, 1, 10 juv., from Sargassum sp. ; 2, three juv. from Sargassum sp. , Roches Noire, 20 January 1999. 2, 2, three juv. Gracilaria sp. and Ulva reticulata, Souillac , 8 February 1999. 11, 16, two juv. from Amansia glomerata and Ulva reticulata ; 8, 30 from Acanthophora spicifera , 25 March 1999, Souillac. 1, two juv. from mixture of Digenia simplex , Gracilaria salicornia (J. Agardh) Dawson and Gelidiella acerosa (Forskal) Feldmann and Hamel, Souillac , 8 April 1999. 2, one juv. from mixture of Caulerpa racemosa (Forskal) J. Agardh , Digenia simplex and Jania adherens Lamouroux , 9 April 1999, Roches Noire. One juv. from Padina sp. and Enteromorpha X exuosa, Tamarin, 18 June 1999. 21, 51, 33 juv. from mixture of Hypnea sp. , Amphiroa sp. and Caulerpa sertulariodes, Tamarin , 18 June 1999. 6, 8, eight juv. from mixture of Hypnea sp. , Amphiroa sp. , Caulerpa sertulariodes and Padina sp. , Tamarin, 18 June 1999. 15, 17, seven juv. from mixture of Padina sp. , Ulva lactuca and Hypnea cornuta, Tamarin , 2 August 1999; 13, 40, 26 juv. from Amphiroa X agilissima and Padina sp. , Tamarin, 2 August 1999. 14, 33, 48 juv. from mixture of Amphiroa X agilissima, Ulva lactuca and Enteromorpha X exuosa, Tamarin, 2 August 1999. 4, one juv. from Sargassum densifolium and Amansia glomerata ; 2, one juv. from Sargassu m densifolium and Amansia glomerata, Souillac , 4 August 1999. 1, three juv. from Digenia simplex, Souillac , 4 August 1999. 1, 1 from mixture of Padina sp. , Sargassum binderi Sonder and Dictyota divaricata Lamouroux, Palmar , 6 August 1999. 9, 26, one juv. from mixture of Centroceras clavulatum (C. Agardh) Montagne , Hypnea cornuta and Gracilaria sp. , 11 October 1999, Tamarin. 6, 23 from Enteromorpha X exuosa and Sargassum densifolium, Tamarin , 11 October 1999. 11, 20, 20 juv. from Sargassum sp. , Digenia simplex and Gelidiella acerosa 16 November 1999, RivieÁre des Galets. 2 1 from Digenia simplex , Padina sp., Amphiroa X agilissima and Corallina sp. , Gris Gris, 14 December 1999. One juv. from mixture of Sargassum sp. Ulva reticulata and Gelidiella acerosa, Souillac , 14 December 1999. 1 from mixture of Ulva lactuca , Sargassum sp. , Gracilaria sp. and Amansia glomerata, Souillac , 14 December 1999. 7 from mixture of Sargassum densifolium , Ulva reticulata , Amansia glomerata and Jania adherens ; 24, 27 0, four juv. from Sargassum densifolium , Ulva reticulata , Amansia glomerata and Jania adherens, Souillac , 10 February 2000.

Description

Colour (in formalin). Head blue; pereon segment 1 white, segments 2±7 blue anteriorly, white posteriorly; epimeral plates and urosome white; uropod 1 peduncle blue. Some specimens have the same colour pattern but with a pink colour replacing the blue. A few specimens were a deep mauve or green colour.

Male. Length, 7.2 mm. Head with small notch below cephalic lobe; eyes oval. Antennae 1 peduncular articles with long robust setae; peduncle article 1 subequal to article 2; article 3, 0.4 times as long as article 1; primary ¯agellum longer than peduncle with 26 articles; accessory ¯agellum two-articulate. Antenna 2 peduncle articles with long setae; ¯agellum shorter than peduncle, with 11 articles and a small terminal article; all articles densely setiferous. Mandible palp article 3 short and slender, 0.8 times length of article 2, with one terminal seta. Maxilla 1 inner plate with two plumose apical setae and few marginal setae; outer plate with four serrate robust setae; palp two-articulate. Maxilla 2 inner and outer plates with distal setae. Maxilliped inner plates with ®ne plumose apical setae and inner marginal setae; outer plates with stout inner marginal and terminal setae; palp four-articulate, article 1 with few robust setae and ®ne setae; articles 2 and 3 densely setiferous. Lower lip mandibular lobes acute; inner and outer plates setose; outer plate with two blunt robust setae on lobes. Gnathopod 1 coxa 1.2 times as long as wide, with long setae, 0.5±1.5 times coxa length, on ventral margin; basis with long setae, carpus with posterior margin setose and bearing ®ve medial groups of setae; propodus, 1.6 times length of carpus, with tufts of setae along posterior margin, medial comb row of setae and seven medial groups of setae; palm oblique, with ®ne setae and small robust setae; dactylus slender and overlapping palm. Gnathopod 2 stouter and more robust than gnathopod 1; coxa twice as long as wide, ventral margin strongly setose, setae 0.5±1 times coxal length; basis 3.5 times as long as wide, with two small robust setae on posterior border and three long ®ne setae on anterior border; carpus short, cup-shaped, with ®ve clumps of robust setae on anterior border; propodus, elongate, subovoid, 1.8 times as long as wide, posterior margin with few long setae; palm oblique, palmar margin with a deep proximal and a shallow distal sinus; dactylus adze-shaped, barely extending around de®ning cusp, inner margin with irregular crenulations, apex rounded. Pereopod 3 coxa 1.4 times as long as wide, ventral margin setae 0.5±0.8 times length of coxa; basis, with robust setae on anterior margin; merus widening distally with two robust setae; posterior margin with three groups of robust setae; carpus subequal to merus, posterior margin with three groups of robust setae; propodus subequal to carpus, posterior margin with many robust setae; dactylus apically constricted bearing two setae at constriction. Pereopod 4 coxa 1.1 times as long as wide, ventral margin bearing long setae, posterior margin excavate; basis, with setae mostly on posterior margin. Pereopod 5 coxa 0.8 times as long as wide; basis ovate, 0.9 times as wide as long, distal anterior margin with robust setae; posterior margin with small setae; merus, posterior and anterior margin extended ventrally, margins with numerous robust setae; carpus 0.8 times length of merus; propodus twice as long as carpus, anterior margin with numerous robust setae; dactylus stout, apically constricted bearing setae at apical constriction. Pereopod 6 similar to pereopod 5, but longer and stouter; coxa rectangular and twice as wide as long; carpus 1.5 times as long as wide; propodus, 1.2 times length of carpus. Pereopod 7 similar to P6; coxa rectangular, 2.5 times as wide as long; carpus 1.6 times as long as wide; propodus 1.1 times length of carpus. Epimera 2±3 each with one row of robust setae on posterior margin. Uropod 1 peduncle 1.2 times rami, outer and inner rami subequal; anterior margins with three stout robust setae. Uropod 2 peduncle subequal to inner ramus, peduncle with a row of stout robust setae on posterior margin, outer ramus 0.8 times inner ramus, inner ramus with a row of stout robust setae on inner margin. Uropod 3 peduncle subequal to outer ramus; outer ramus 1.1 times longer than inner ramus, both rami bearing stout robust setae. Telson cleft to base, apices with inner marginal tooth vestigial and bearing three stout robust setae.

Young males. Gnathopod 2 palmar margin with less apparent sinuses, dactylus shorter than the de®ning cusp and inner border of dactylus smooth.

Female. Length, 5.7 mm (mature, with juveniles in brood pouch). Female body setation and antennal setation like that of male, but coxae less setose.

Gnathopod 1 similar to that of male but coxa with fewer and shorter ventral setae. Gnathopod 2 with few setae on coxal plate; basis bearing long setae on anterior margin, merus, carpus and propodus strongly setose on posterior margin, propodus, oval, palm very oblique; dactylus small and ®tting palm. Pereopods 6 and 7 more slender than those of male. Pereopod 6 carpus twice as long as wide; propodus 1.4 times carpus. Pereopod 7 carpus 1.5 times as long as wide; propodus 1.5 times carpus. Etymology From the latin: caeruleum 5blue, referring to the normal coloration of this species.

Remarks

Mallacoota caerulea males range from 2.5 to 6 mm while females range from 3 to 6.2 mm in size. Both sexes of the species are easily recognized in formalinpreserved specimens by their colour pattern.

In males, the strongly setose coxal plates 1±4 distinguish this species from M. insignis and M. latibrachium . The male gnathopod 2 propodus with its oblique palm de®ned by two sinuses and a few patches of setae distinguish it from M. schellenbergi and M. insignis . The adze-shaped dactylus and fully cleft telson separate it from all other Mallacoota species recorded from Mauritius.

One of the notable characteristic of M. caerulea is the presence of only one terminal seta on mandibular palp article 3. The only other Mallacoota to have this feature is M. carausui from Cuba ( Ortiz, 1976).

Habitat. Mallacoota caerulea occurs on algae in the intertidal and shallowsubtidal at depths less than 1 m. It is common among the red algae, Acanthophora spicifera , Amansia glomerata , Jania adherens and Hypnea sp. This species occurs at sites of heavy wave action for example, Gris-Gris, Souillac and Roches Noire which are sites where either the coral reefs are discontinuous or very close to shore. It also occurs at sites which have some freshwater inūence for example, Riviere des Galets and Tamarin.

Distribution. Mauritius.