Enteromorpha, J.H.F.Linkon Esenbeck, 1820

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 : 778-782

Enteromorpha X exuosa and coral rubble, Poste La Fayette, 16 December 1999.

3, 15 from mixture of Padina sp. , Gracilaria salicornia , Ulva lactuca , Hypnea sp. and Dictyota sp. , Choisy, 25 January 2000. 7, 5, 19 juv. from mixture of Laurencia papillosa (Forskal) Greville , Halodule uninervis (Forskal) Ascherson and Enteromorpha X exuosa (Wulfen) J.zAgardh, Poste La Fayette, 7 February 2000. 1 from mixture of Sargassum densifolium , Ulva reticulata , Amansia glomerata and Jania adherens, Souillac , 10 February 2000.

Description

Colour (in formalin). Yellowish green without any speci®c colour pattern.

Male. Length, 4.7 mm. Dorsal margins of the head, pleon and epimeron setose. Head with notch present below cephalic lobe. Eyes round and black in colour. Antenna 1 peduncle article 1 bears four patches of long setae on the posterior margin; articles 2 and 3 with patches of setae all over; article 2 twice as long as article 3; accessory ¯agellum three-articulate; terminal article short; primary ¯agellum 25-articulate. Antenna 2 peduncular segments densely setose, article 4, 1.4 times article 5; ¯agellum densely setose, about half-length of peduncle and seven-articulate. Mandible with three-articulate palp; article 3, 1.8 times article 2 bearing two terminal setae. Maxilla 1 inner plate with two plumose apical setae and marginal setae; outer plate with ®ve serrate robust setae and palp two-articulate. Maxilla 2, inner and outer plates with distal setae; base of outer plate with two robust setae. Maxilliped, inner plate with plumose setae on apical and inner margin; outer plate with stout setae on apical and inner margin; palp four-articulate; articles 2 setose on inner margin; article 3 setose on distal end. Lower lip with acute mandibular lobes; inner and outer plates densely setose; outer plate with three to four blunt robust setae. Gnathopod 1 coxa 1.1 times as long as wide; setae present on ventral and lateral margin, setae short and less than half the length of coxa; basis with three long setae on posterior margin; basis and ischium with a small protuberance (carina) on the postero-ventral margin; carpus posterior margin densely setose and bearing four medial groups of setae; propodus 1.2 times carpus with medial comb row of setae and few patches of medial setae present; palm oblique, palmar margin with short ®ne setae and robust setae; dactylus slender and extending beyond palm. Gnathopod 2 coxa 1.4 times as long as wide, ventral margin bearing patches of setae less than three-quarter length of coxa; basis posterior margin with four long setae and numerous small robust setae; basis and ischium with well-developed carina on the posteroventral margin; carpus as long as wide with dense patches of setae on posteroventral margin; propodus elongate, subovoid and twice as long as wide, posterior margin with dense long setae, patches of shorter setae on medial face, propodus posterior margin with a rectangular blunt ¯at tooth; dactylus slender extending to about 60% length of propodus, with a blunt tip and a small cusp on inner margin. In young males, the blunt ¯at tooth is embedded in the posterior margin of the propodus, and dactylus is about one-third length of propodus. Pereopod 3 coxa, 1.9 times as long as wide bearing a few patches of setae on ventral margin, setae short or less than half length of coxa; basis with ®ve robust setae on anterior margin, posterior margin with two long setae and few small setae; basis and ischium with welldeveloped carina on posteroventral margin; carpus 0.7 times merus; propodus 1.6 times carpus, posterior margin spinous; dactylus constricted with setae at constriction. Pereopod 4 similar to pereopod 3 except coxa 1.3 times as long as wide and posteriorly excavate, ventral margin of coxa with a few long setae; propodus 1.3 times length of carpus. Pereopod 5 coxa bilobed, 1.8 times as wide as long; basis subovate, anterior margins with robust setae, posterior margin weakly crenulate with small setae; merus posterior margin extended ventrally; carpus 0.8 times merus; propodus twice as long as carpus and bearing long robust setae on distal margin; dactylus with setae at constriction. Pereopod 6 similar to P5 but more slender; coxa lobulate, 2.3 times as wide as long with a few robust setae; basis subovate; carpus 1.5 times as long as wide; propodus 1.6 times as long as carpus, distal margin of propodus with very long setae. Pereopod 7 similar to pereopod 6; coxa lobulate, 1.6 times as wide as long; basis subovate; carpus 1.6 times as long as wide; propodus 1.6 times length of carpus; setation similar to pereopod 6. Epimeron 3 subquadrate with one row of robust setae. Uropod 1 peduncle 1.3 times outer ramus; outer ramus 0.7 times inner ramus; inner ramus with few robust setae on border; outer ramus with three groups of robust setae. Uropod 2 peduncle 0.9 times outer ramus; outer ramus 0.9 time inner ramus. Uropod 3 peduncle subequal to outer ramus; inner and outer rami subequal with very long robust setae on distal margin. Telson cleft midway with three stout robust setae; apices with inner marginal tooth weakly developed.

Female. Length, 4.7 mm. Body and antennal setation similar to that of male. Gnathopod 1 coxa 1.3 times as long as wide, bearing setae on ventral margin and distal lateral margin, setae short and less than half-length of coxa. Other features similar to male except that carina on basis and ischium less developed. Gnathopod 2 coxa 1.4 times as long as wide with short setae on ventral and anterior margins; basis and ischium with carina; propodus twice as long as wide, palm oblique, palmar border with small ®ne setae and robust setae; dactylus small and ®tting palm. Pereopod 6 propodus 1.4 times carpus; carpus 1.6 times as long as wide. Pereopod 7, carpus subequal to propodus and 1.5 times as long as wide. Uropods and telson similar to those of male.

Remarks

Males of Mallacoota schellenbergi range from 4.3 to 5.7 mm and females from 4 to 5.7 mm in size. Present material agrees with that of Ledoyer (1984) from New Caledonia. This species is distinguished from other Mallacoota species in Mauritius by the male gnathopod 2 propodus, the posterior margin of which has a ¯at-topped tooth and is densely setose and the palm is very oblique. In mature specimens the dactylus has a cusp on the inner margin. In juveniles where the dorsal carinae on urosomite 3 are not very apparent, this species may be confused with Elasmopus species. They can be distinguished by the mandibular palp.

Previously known only from New Caledonia, this is the ®rst record from Mauritius.

Habitat. Mallacoota schellenbergi occurs mostly on algae, but can also be found in mixtures containing coral rubble, or seagrass for example Halodule uninervis . This species occurs on a wide variety of algae and is fairly common among the red algae, Acanthophora spicifera , Gracilaria species or Laurencia papillosa . Mallacoota schellenbergi is widespread in the intertidal zone and shallow-subtidal at depths less than 1 m. It occurs both at sites of low wave action, for example, Bain Boeuf, Choisy, and at sites of heavy wave action, for example, Souillac and Roches Noire. The species was collected from sites located on the north, east and south coasts.

Type locality. L’õÃloÃt MaõÃtre , New Caledonia .

Distribution. Mauritius, New Caledonia.