Munida simulatrix, Macpherson & Machordom, 2005

Macpherson, E. & Machordom, A., 2005, Use of morphological and molecular data to identify three new sibling species of the genus Munida Leach, 1820 (Crustacea, Decapoda, Galatheidae) from New Caledonia, Journal of Natural History 39 (11), pp. 819-834 : 825-828

Munida simulatrix sp. nov.

( Figure 2 )

Munida notata Macpherson 1994, p 500 (in part).

Material examined

New Caledonia. BIOCAL, stn 108, 9 September 1985, 22 ° 02.55 9 S, 167 ° 05.68 9 E, 335 m: 6 males 5.7–7.7 mm, four ovigerous females 5.6–7.8 mm .

NORFOLK 1, stn 1721, 26 June 2001, 23 ° 19.249 9 S, 168 ° 00.862 9 E, 416–443 m: one male 7.7 mm (holotype, MNHN-Ga 4617).

NORFOLK 2, stn 2092, 29 October 2003, 24 ° 45.17 9 S, 168 ° 07.23 9 E, 320–345 m: three males 7.6–9.6 mm, one ovigerous female 7.8 mm; stn 2118, 1 November 2003, 23 ° 22.87 9 S, 168 ° 00.86 9 E, 383–393 m: one ovigerous female 9.3 mm; stn 2119, 1 November 2003, 23 ° 22.75 9 S, 168 ° 01.64 9 E, 300 m: three males 7.9–9.8 mm, one ovigerous female 8.6 mm; stn 2127, 2 November 2003, 23 ° 16.03 9 S, 168 ° 14.60 9 E, 379– 381 m: two males 10.5–11.0 mm; stn 2130, 2 November 2003, 23 ° 15.90 9 S, 168 ° 13.54 9 E, 375–427 m: one female 10.9 mm; stn 2135, 3 November 2003, 23 ° 01.61 9 S, 168 ° 21.35 9 E, 295–330 m: one male 6.7 mm; stn 2139, 3 November 2003, 23 ° 00.56 9 S, 168 ° 22.80 9 E, 372–393 m: one male 8.5 mm, one ovigerous female 8.4 mm; stn 2148, 4 November 2003, 22 ° 44.20 9 S, 167 ° 15.97 9 E, 386–391 m: three males 6.3–7.7 mm, four ovigerous females 7.4–8.7 mm, one female 7.4 mm; stn 2151, 5 November 2003, 22 ° 42.75 9 S, 167 ° 14.10 9 E, 353–368 m: one male 9.6 mm, two ovigerous females 8.4–8.6 mm; stn 2152, 5 November 2003, 22 ° 44.72 9 S, 167 ° 13.89 9 E, 380–390 m: one male 11.2 mm, one ovigerous female 11.3 mm.

Loyalty Islands. MUSORSTOM 6, stn 398, 13 February 1989, 20 ° 47.19 9 S, 16705.65 9 E, 370 m: four males 9.2–10.1 mm, three ovigerous females 9.0– 9.5 mm .

Etymology

From the Latin simulatrix in reference to the similarity to M. notata .

Description

Carapace slightly longer than wide, longitudinally convex. Transverse ridges mostly interrupted, with dense, very short, non-iridescent setae and a few long setae. Few scales and secondary striae between main striae. One stria on intestinal region. Gastric region with 12 epigastric spines. One hepatic, one parahepatic, one anterior branchial and one postcervical spine on each side. Frontal margins transverse. Lateral margins subparallel. Anterolateral spine well developed, reaching level of sinus between rostrum and supraocular spines. Two small marginal spines before cervical groove, posterior spine larger than preceding one and about three times smaller than anterolateral spine. Branchial margins with five spines ( Figure 2A ).

Rostrum spiniform, three-quarters as long as remaining carapace, straight and slightly upwards directed. Supraocular spines reaching midlength of rostrum and not reaching end of corneae, parallel, directed upwards.

Thoracic sternites smooth. Fourth sternites with few short arcuate striae, concave medially. Anterior part of fourth sternite as wide as third ( Figure 2B ).

Second abdominal somite with one pair of spines on each side of anterior ridge. Second to fourth somites with several transverse striae.

Eyes large, maximum corneal diameter nearly half distance between bases of anterolateral spines.

Basal segment of antennule (distal spines excluded), about one-quarter carapace length, elongate, slightly over-reaching end of corneae, with two distal spines, mesial longer than lateral; two spines on lateral margin, proximal one short, located at midlength of segment, distolateral spine long, reaching end of distal spines ( Figure 2C ).

First segment of antennal peduncle with one strong distal spine on mesial margin, slightly over-reaching end of third segment and reaching base of long lateral spine of basal segment of antennule; second segment with two long distal spines, mesial spine longer than lateral spine, slightly over-reaching end of antennal peduncle; penultimate segment unarmed ( Figure 2C ).

Ischium of third maxilliped slightly longer than merus measured along dorsal margin, distoventrally bearing spine. Merus of third maxilliped with two well-developed spines on flexor margin, distal smaller, extensor margin with small distal spine ( Figure 2D ).

Chelipeds squamous, with long uniramous setae, most of them iridescent, denser on mesial and lateral borders of articles. Palm slightly longer than fingers. Merus armed with some spines, strongest spine on distal border short, reaching proximal third of carpus. Carpus with several spines on dorsal side and several spines scattered on mesial and ventral sides. Palm with spines scattered on mesial and dorsal sides and row of spines on lateral border. Fixed finger with some spines along lateral margin, movable finger with spines along mesial border, fingers distally curving and crossing, ending in a sharp point ( Figure 2E ).

Second pereiopod about two times carapace length; merus shorter than carapace, about six times as long as high, about three times carpus length and 1.5 times as long as propodus; propodus about 5.5 times as long as high, 1.5 times longer than dactylus ( Figure 2F ). Merus with well-developed spines along dorsal and ventral borders, increasing in size distally. Carpus with some dorsal spines and one distoventral spine. Propodus with 11 movable ventral spines. Dactylus slightly curving distally, with eight movable spinules along ventral margin, distal quarter unarmed ( Figure 2G ). Third pereiopod slightly shorter than second; fourth pereiopod clearly shorter than second and third. Merus of fourth pereiopod two-thirds length of second pereiopod.

Remarks

Munida simulatrix belongs to the group of species with the following features: five spines on the lateral margins of the carapace behind the cervical groove, smooth thoracic sternites, large eyes, abdominal somites that are unarmed or have spines on each side of the anterior ridge on the second somite, spiniform rostrum, a shorter distomesial than distolateral spine of the basal antennular segment and a distal spine on the extensor margin of the merus of the third maxilliped. The new species is very close to M. notata Macpherson, 1994 , found between 59 and 850 m in New Caledonia, Loyalty Islands, Chesterfield Islands, Vanuatu, Wallis and Futuna Islands, Fiji Islands and Tonga Islands ( Macpherson 1994, 2004). For comparison, material of M. notata collected during the NORFOLK 1 and 2 cruises and additional material, included in the original description ( Macpherson 1994), was used.

However, these two species are distinguished by the following morphological and molecular differences.

The dorsal surface of the branchial regions in M. notata have more secondary striae than M. simulatrix .

The distomesial spine of the basal antennal segment reaches the base of the long lateral spine of the basal antennular segment in M. simulatrix , whereas this does not occur in M. notata (see Macpherson 1994, Figure 34c). Furthermore, this distomesial spine of the basal segment clearly over-reaches the third segment in the new species, whereas in M. notata it only slightly exceeds this segment.

Molecular data allowed distinction between M. simulatrix and M. notata , even though these species are the most closely related of the three pairs of taxa studied. Fifteen substitutions were found in the 16S sequences analysed and 67–68 in the COI, which leads to a global divergence of 5.2% (1.4% for 16S and 8.2 for COI).

Distribution

New Caledonia at 295–443 m and Loyalty Islands (370 m) .

Figures

Figure 2. Munida simulatrix sp. nov., male 7.7 mm, holotype from stn 1721 (NORFOLK 1). (A) Carapace, dorsal view; (B) sternal plastron; (C) ventral view of cephalic region, showing antennular and antennal peduncles; (D) right third maxilliped, lateral view; (E) right cheliped, dorsal view; (F) right first walking leg, lateral view; (G) dactylus of right first walking leg, lateral view.