Munidopsis hirtella, Macpherson & Segonzac, 2005

Macpherson, Enrique & Segonzac, Michel, 2005, Species of the genus Munidopsis (Crustacea, Decapoda, Galatheidae) from the deep Atlantic Ocean, including cold-seep and hydrothermal vent areas, Zootaxa 1095 (1), pp. 1-60 : 27-31

Munidopsis hirtella n. sp. ( Fig. 7 )

Material examined. Off Mauritania, EUMELI 2, Stn CP 08, 18º29’N, 20º59’W, 3126 m, 10.02.1991: 2 males 29.0– 32.6 mm. — Stn CP 09, 18º37’N, 21º03’W, 3125 m, 11.02.1991: 1 ovig. female 36.5 mm. Off Angola, BIOZAIRE 3, Stn CP 15, 05°51'S, 09°43.02'E, 3166 m, 28.12.2003: 3 females 27.8–33.8 mm.— Stn CP 16, 05°49.79'S, 09°44.08'E, 3172 m, 28.12.2003: 1 male 20.3 mm, 1 ovig. female 27.5 mm, 3 females 24.4–34.9 mm.— Stn CP 17, 05°48.69'S, 09°43.98'E, 3156 m, 30.12.2003: 1 male 21.9 mm.— Stn CP 19, 05°48.07'S, 09°41.60'E, 3184 m, 31.12.2003: 1 male 20.4 mm, 1 female 21.4 mm.— Stn CP 20, 05°46.89'S, 09°44.66'E, 3113 m, 02.01.2004: 1 male 16.1 mm.— Stn CP 22, 05°46.97'S, 09°44.18'E, 3121 m, 03.01.2004: 1 male 26.5 mm, 1 female 28.2 mm .

Types. The ovigerous male of 32.6 mm from EUMELI 2, Stn CP08 (MNHN­Ga 4622) has been selected as holotype, the other specimens are paratypes.

Etymology. From the diminutive of the Latin hirtus, hairy, in reference to the numerous setae on the carapace and abdomen.

Description. Carapace, exclusive of rostrum, slightly longer than wide, anterior and posterior cervical grooves evident but not deep, gastro­cardiac groove well­defined. Gastric and cardiac regions slightly convex, with both small and moderate­sized spines and tubercles as figured. Hepatic region and anterior half of branchial region each with small numerous spines and tubercles. Posterior half of carapace bearing elevated, interrupted transverse ridges. Spines, tubercles and ridges on carapace surface with numerous uniramous setae. Frontal margin oblique. Antennal spine well­developed. Posterior margin unarmed. Lateral margins nearly straight and subparallel, bearing strong spines on anterior half, first anterolateral, slightly smaller than second, divergent anteriorly, located distinctly mesial to level of remaining spines, second spine largest, directed slightly more laterad than preceding, 6 or 7 spines behind second spine, 2 or 3 of them about as large as first spine. Rostrum moderately narrow, somewhat upturned, middorsal ridge wide, length about one­third remaining carapace. Pterygostomian flap anteriorly ending in rounded tip, with numerous granules and short ridges.

Third thoracic sternite narrow, forming apposed lobe bearing anteromedian process at either side of deep median groove; depressed below level of, and, separated by deep groove from, anteriorly narrowed fourth thoracic sternite.

Abdomen spineless; segments 2–4 each with 2 moderately elevated transverse ridges, somewhat granulate, and with numerous unirramous setae; no ridge on segments 5–6; segment 6 having well­developed posterolateral lobes, slightly overreaching transverse posteromedian margin. Telson divided into 8 plates, length­width ratio 0.7.

Eyes slightly movable dorsoventrally, bearing distomesial eyespine strongly produced forward; cornea well­developed and lateral, distinctly broader than eyespine.

Article 1 of antennular peduncle with strong distodorsal and distolateral spines, with small tubercle­like spines distomesially. Article 1 of antennal peduncle bearing sharp, distolateral and distolateral spines; article 2 with sharp distolateral spine only exceeding midlength of article 3; article 3 narrower than 2, with small distomesial spine and a few distolateral tubercles.

Ischium of third maxilliped more than half as long as merus, bearing strong short spine on extensor distal margin and small spine on flexor distal margin, mesial crest with row of 21 denticles; merus with 3 or 4 spines and 2 or 3 acute granules on flexor margin, and one sharp extensor distal marginal spine; carpus unarmed, propodus relatively slender.

Chelipeds covered with small rugae and granules, uniramous setae more dense along mesial and lateral margins; about 1.9 times as long as postorbital carapace length. Basiischium with 2–4 spines on mesial margin, distodorsally with strong spine, distoventral margin at juncture with merus bearing several small spines. Merus slightly overreaching rostrum, armed with spines in rows, distomesial spine strongest. Carpus bearing row of mesial and lateral spines, a few distal spines on dorsal border. Palm with acute granules on dorsal margin, a few small spines along mesial margin, slightly shorter than fingers, less than twice as long as broad. Fingers unarmed, not gaping, distally spooned, prehensile edges crenulate.

Walking legs rather long, slender, subcylindrical; first walking leg overreaching chela. Merus longer on first leg than on second leg, shorter on third than on preceding legs, each bearing dorsal crest with row of spines continued on to corresponding crest on carpus, ventral margin with some spines; each carpus having dorsolateral and dorsoventral granulate crests without spines continued on to corresponding crests on propodus. Each propodus with proximal mesial crest with spines; propodus slightly longer than dactylus. Dactyli slender, gently but distinctly curved, terminating in acute corneous spine preceded by row of 13 or 14 very low, proximally diminishing processes, each process supporting corneous seta, ultimate process clearly closer to tip of dactylus than to penultimate process.

Epipods present on chelipeds.

Eggs: Diameter, 2.9 mm

Remarks. The sixth abdominal segment without produced posteromedian flap, the first walking leg exceeding the tip of the chela, eyes bearing a well­developed, anteriorly directed distomesial eyespine, and absence of a denticulate carina on the distolateral margin of the chela, link M. hirtella to M. subsquamosa Henderson, 1885 from the Pacific, Indian and Southern Oceans, between 2516 and 4260 m and M. recta Baba, 2005 from the Gulf of Panama, at 2950–3190 m (see Baba, 2005).

The new species is easily differentiated from M. subsquamosa by the size of the cornea: it is as broad as the eye spine in M. subsquamosa , instead of being distinctly broader in the new species. Furthermore, the gastric region has more spines in the new species than in M. subsquamosa , and the length of the dactylus of the walking legs is 0.61 that of propodus in M. subsquamosa , whereas in the new species, the dactylus is slightly shorter than the propodus. Finally, the body of the new species has numerous simple setae, whereas these setae are absent in M. subsquamosa .

Munidospis hirtella is differentiated from M. recta by the following characters:

– The gastric region and the lateral margins of the carapace have more spines in the new

species than in M. recta .

– The body has few uniramous setae in M. recta , whereas in M. hirtella the carapace,

abdomen and appendages have numerous uniramous setae.

– The flexor margin of the dactylus of the walking legs is nearly straight in M. recta ,

being considerably curving in the new species. Furthermore, the dactylus of the

walking legs is about 0.5 times the length of the propodus in M. recta , whereas in the

new species the dactylus is three­quarter the length of the propodus.

Distribution and habitat. The species has only been reported off western Africa, between Mauritania and Congo, at 3125–3166 m. The EUMELI specimens were collected in a sedimentary area, together with actiniarians, polychaetes, molluscs, shrimps, pagurids, echinoderms ant tunicates ( Galéron et al., 2000). The species was collected in the coldseep site Regab, and away from the influence of seepage (1.5 km north and 7.5 km south of the site).

Figures

FIGURE 7. Munidopsis hirtella n. sp., holotype, male (32.6 mm), off Mauritania, EUMELI 2, Stn CP08, MNHN­Ga 4622. A: carapace, setae omitted, dorsal; B: same, lateral; C: posterior part of sixth abdominal segment and telson; D: anterior part of sternal plastron; E: left antennule, antenna and ocular peduncle, ventral; F: endopod of right third maxilliped, lateral; G: right cheliped, lateral; H: right second pereiopod, lateral. Scale: A–C, G–H = 5 mm, D–F = 2 mm.