Metaprotella mauritiensis Guerra-García, 2003, n. sp.

Metaprotella mauritiensis n. sp. (Figs. 4–7)

Material examined. Holotype male (MNCN 20.04/5418a), living on fine sediment among soft corals of the genus Dendronephthya, 2–3 m, 20 July 2002 (CM). Allotype female (MNCN 20.04/5418b), collected together with the holotype male. Paratypes: 6 males, 5 females, 2 juveniles (MNCN 20.04/5418c), collected together the holotype; 1 male, 3 females, 1 juvenile deposited at the Albion Fisheries Research Center (AFRC), collected together the holotype

Type locality. Cap Malheureux, Mauritius (20º18’S, 57º47’E)

Etymology. The species bears the name of the Island where it was found, Mauritius.

Diagnosis. Head and body smooth. Pereonites 6 and 7 fused. Suture between the head and pereonite 1 well marked. Flagellum of antenna 2 with 2 articles; swimming setae absent. Mandibular palp 3­articulate; setal formula for terminal article 1­2­1; molar present. Pereopods 3 and 4 each reduced to minute round article. Pereopods 5–7 without grasping spines. Abdomen of male with a pair of uniarticulate appendages.

Description

Mature male (holotype, MNCN 20.04/5418a).

Body length 3.4 mm. Suture between head and pereonite 1 present; pereonite 3 longest. Pereonites 6 and 7 fused. Head and body smooth. Eye distinctive. Gills on pereonites 3 and 4, oval, length about 2 times the width; first pair 1.2 times as long as the second pair.

Mouthparts. Upper lip symmetrically bilobed; each lobe carrying a distal row of minute setulae. Mandibles with palp; mandibular molar process strong; left mandible with incisor and lacinia mobilis divided into 5 teeth, followed by 3 submarginal pectinate setae; right mandible incisor divided into 5 teeth followed by lacinia mobilis divided into 2 teeth, one wider and minutely serrate, followed by 2 pectinate setae; palp with 3 articles; article 1 lacking setae; article 2 with 2 setae on left mandible and without setae on the right mandible; article 3 with setal formula 1­2­1. Inner lobes of the lower lip well demarcated, rectangular, with margin smooth. Maxilla 1 outer lobe carrying 7 bifurcate spines; distal article of palp with 4 teeth and 5 robust setae on apical end, and 3 setae medially. Maxilla 2 outer lobe rectangular, carrying 7 setae; inner lobe oval, with 6 setae distally. Maxilliped inner plate oval, with 3 simple setae and 1 robust setae (like a tooth) on distal margin; outer plate larger than inner, inner margin setulose, bearing 1 seta apically; article 3 of the palp without distal expansion.

Antenna 1 a little shorter than the body length; article 2 of the peduncle the longest; flagellum 7­articulate.

Antenna 2 without swimming setae; peduncular article 1 without acute distal projection; flagellum 2­articulate.

Gnathopod 1 basis a little shorter than ischium to carpus combined; propodus oval with proximal grasping spine, palm margin almost smooth; dactylus minutely setose on inner margin.

Gnathopod 2 inserted on anterior half of pereonite 2; basis slender, as long as pereonite 2; propodus elongate, length about 2 times of width, with a minute grasping spine on small proximal projection, and another two triangular projection distally; dactylus with sparse setulae medially on the inner margin.

Pereopods 3–4 reduced to a minute round article. Pereopods 5–7 (from male paratype, MNCN 20.04/5418c) similar to each other, smooth, without grasping spines. Penes small, situated laterally.

Abdomen with a pair of 1­articulate appendages, pair of lobes and single dorsal lobe with pair of plumose setae.

Mature female (allotype, MNCN 20.04/5418b).

Body length 2.3 mm. Differences to the male: palm of gnathopod 2 straight, without projections. Oostegites on pereonite 3 and 4 with inner margin setose. Genital openings setose. Abdomen with pair of lateral lobes and single dorsal lobe.

Remarks.

The genus Metaprotella has been recently studied by Larsen (1997) and Guerra­García (2002a). Metaprotella mauritiensis n.sp. has been assigned to the genus Metaprotella mainly due to the fusion of the pereonites 6 and 7, but this new species can be easily distinguished from the remaining species of Metaprotella by the absence of grasping spines on the pereopods 5–7, the tiny pereopods 3 and 4 and the shape of the male gnathopod 2. The new species is small in size (males: 2.21 ± 0.73 mm (mean ± standard deviation), range (1.50–3.40 mm); females 1.82 ± 0.43 (1.30–2.60)). Curiously, although samples of sediment have been collected around the whole island, M. mauritiensis has been only found in the soft bottoms from the northern area, Cap Malheureux. The sediment in this area was surrounded by soft corals of the genus Dendronephthya. A key to species level, modified from Larsen (1997) and Guerra­García (2002a) is provided as a basic comparison among Metaprotella species.

Key to the world species of Metaprotella (modified from Larsen, 1997 and Guerra­García, 2002a)

1. Propodus of pereopods 5–7 without grasping spines. Pereopods 3 and 4 extremely reduced, almost absent. Body length of adults less than 3.5 mm. M. mauritiensis n. sp.

– Propodus of pereopods 5–7 with a pair of grasping spines. Pereopods 3 and 4 not reduced, with 1 or 2 articles. Body length of adults more than 3.5 mm....................... 2

2. Pereopods 3 and 4 with 2 articles ......................... M. tanzaniensis Guerra­García, 2002

– Pereopods 3 and 4 with 1 article................................................................................... 3

3. Propodus of male gnathopod 2 with an acute distal projection...................................... ................................................................................... M. makrodactylos Stebbing, 1910

– Propodus of male gnathopod 2 without acute distal projection.................................... 4

4. Male gnathopod 2 ventral margin of propodus with several conspicuous rows of dense setae. Dactylus of male gnathopod 2 decreasing in width midway................................ ................................................................................................... M. unguja Larsen, 1997

– Male gnathopod 2 ventral margin of propodus without conspicuous rows of setae. Dactylus of male gnathopod 2 not decreasing in midway............................................ 5

5. Suture between head and pereonite 1 absent...................... M. sandalensis Mayer, 1898

– Suture between head and pereonite 1 present..........……..............................................6

6. Body dorsally smooth.................................................................................................... 7

– Body with dorsal projections......................................................................................... 8

7. Pereonite 3 with one forward pointing spine laterally .... M. problematica Mayer, 1890

– Pereonite 3 lacking laterally spines............................... M. hummelincki McCain, 1968

8. Male gnathopod 2 lacking spines on basis.............................. M. africana Mayer, 1903

– Male gnathopod 2 with spines on basis......................................................................... 9

9. Pereopods 3 and 4 about 1/4 the length of the gills. Basis of male gnathopod 2 with dorsomedial spines ............................................................... M. excentrica Mayer, 1890

– Pereopods 3 and 4 about 1/2 the length of the gills. Basis of male gnathopod 2 lacking dorsomedial spines........................................................ M. haswelliana (Mayer, 1882)