Munida mendagnai, Cabezas & Macpherson & Machordom, 2009

Cabezas, Patricia, Macpherson, Enrique & Machordom, Annie, 2009, Morphological and molecular description of new species of squat lobster (Crustacea: Decapoda: Galatheidae) from the Solomon and Fiji Islands (South-West Pacific), Zoological Journal of the Linnean Society 156 (3), pp. 465-493 : 474-476

MUNIDA MENDAGNAI SP. NOV. ( FIG. 4 )

Material examined: Solomon Islands. SALOMON 1. Stn 1825, 09°50.5′S, 160°57.9′E, 4 October 2001, 340– 391 m: 2 F, 7.1–7.2 mm (paratypes, MNHN-Ga6508). Stn 1826, 09°56.4′S, 161°03.9′E, 4 October 2004, 418– 432 m: 1 M, 10.0 mm (paratype, MNHN-Ga6509); 1 M, 7.3 mm (holotype, MNHN-Ga6510) .

Etymology: The name mendagnai is in honour of Alvaro de Mendaña, the Spanish explorer who named the Solomon Islands in 1568.

Description: Carapace 1.2 times longer than wide. Transverse ridges usually interrupted in cardiac and branchial regions by very short, non-iridescent setae, and by some scattered long iridescent setae. Small scales on intestinal region. Dorsal surface of carapace armed with 11–13 epigastric spines, one small hepatic, one parahepatic, and one postcervical spine on each side. Frontal margins transverse. Lateral margins subparallel. Anterolateral spine welldeveloped, situated at anterolateral angle, clearly not reaching the level of the sinus between the rostrum and the supraocular spines. Second marginal spine before cervical groove small, about 0.25 times the length of the anterolateral spine. Branchial margins with five small spines. Rostrum spiniform, nearly 0.7 times the length of the remaining carapace, horizontal, dorsally carinated and slightly convex. Supraocular spines short, clearly not reaching the midlength of the rostrum, and not reaching the end of the corneae, subparallel, slightly directed upwards ( Fig. 4A ).

Fourth thoracic sternite smooth, with a few short striae. Anterior part of fourth sternite narrower than third; median margin of third sternite contiguous with fourth sternite ( Fig. 4B ).

Second abdominal somite with eight or nine spines along anterior ridge. Second and third somites each with between four and six transverse striae.

Epistome crest with hump near mouth opening.

Eyes large: maximum corneal diameter 0.5 times the distance between the bases of the anterolateral spines.

Basal segment of antennule (distal spines excluded) about 0.3 time the carapace length, elongate, about 2.5 times longer than wide (excluding spines), reaching end of corneae, with two distal spines, mesial spine shorter than lateral spine; two spines on lateral margin, proximal one short, located at midlength of segment, distal one long, reaching end of distal spines ( Fig. 4C ). First segment of antennal peduncle with one short distomesial spine nearly reaching the end of the second segment; second segment with two distal spines, mesial spine longer than lateral spine, slightly exceeding end of antennal peduncle, and with one additional mesial spine at midlength; third segment unarmed ( Fig. 4C ).

With Mxp 3 ischium about 1.5 times the length of the merus, measured along the dorsal margin, and distoventrally bearing a spine. Merus of Mxp 3 with two well-developed spines on flexor margin, distal margin smaller; extensor margin unarmed ( Fig. 4D ).

With P1s subequal in length, between 1.8 and 2.8 times the carapace length, squamous, with numerous uniramous iridescent setae and plumose noniridescent setae, denser on mesial and lateral borders of articles. Merus shorter than carapace length, twice carpus length, armed with some spines, strongest spine on distal border, reaching proximal fourth of carpus. Carpus 1.4–1.7 times as long as high, shorter than hand, several strong spines on mesial border, and some small spines on dorsal side. Palm as long as fingers, with a row of mesial spines, with some scattered small spines on dorsal side, and one row of lateral spines continuing onto fixed finger and reaching tip. Movable finger unarmed, except proximal and distal spines. Fingers distally curving and crossing, ending in sharp points, cutting edges with small teeth of various sizes ( Fig. 4E ).

With P2 about twice the carapace length, with numerous uniramous iridescent setae and plumose non-iridescent setae along dorsal margins of articles; merus 0.8 times as long as carapace, between five and six times as long as high, 3.0–3.5 times the carpus length, and 1.5–1.8 times as long as the propodus; propodus between four and five times as long as high, and 1.2–1.3 times longer than dactylus ( Fig. 4F ). Dorsal border of merus with row of spines, increasing in size distally; ventral margin with row of spines, increasing in size distally. Carpus with several dorsal spines and one distoventral spine; distal margin clearly not reaching level of merocarpal articulation of P1. Propodus with between nine and 11 movable ventral spinules. Dactylus slightly curving distally, with seven movable spinules along ventral margin, distal fourth unarmed, ultimate spine clearly more remote from tip of dactylus than from penultimate spine ( Fig. 4G ). P3 0.9 times the length of P2; merus slightly shorter than that of P2; spination of P3 similar to that of P2 ( Fig. 4H ). P4 0.8 times the length of P2; merus 0.7 times the length of that of P2; spines along margins of merus and carpus less spinose than those of P2 and P3 ( Fig. 4I ); merocarpal articulation ending at the level of the anterior branch of the cervical groove.

Remarks: The new species is closely related to Munida angusta Macpherson, 2004 from the New Caledonia, Fiji, and Tonga islands ( Macpherson, 2004). The two species have five spines on the lateral margin of the carapace behind the cervical groove, eyes large, the second abdominal segment with spines, lateral portions of the posterior thoracic sternites without granules, rostrum spiniform, the epistome crest with a hump near the mouth opening, the distomesial spine of the basal antennular segment clearly shorter than the distolateral spine, and the distomesial spine of the second antennal article reaching the end of the fourth article. The two species can be distinguished according to the following characters.

1. The second and third abdominal segments have between four and six transverse striae in the new species, instead of only one or two striae in M. angusta .

2. The chelipeds (P1) are clearly larger and shorter in the new species than in M. angusta . In the new species, the length of P1 is between 1.8 and 2.8 times the carapace length, whereas this ratio is between 3.0 and 4.5 times in M. angusta . The carpus is more than three times longer than broad in M. angusta , and 1.4–1.7 times longer than broad in the new species. The movable finger has a row of spines along the mesial margin in M. angusta , whereas this margin has only one proximal and one distal spine in the new species.

3. The walking legs (P2–P4) are longer and more slender in M. angusta . P2 is about 1.5 times the carapace length in the new species, being 2.5 times that in M. angusta . Furthermore, the length of the merus of this leg is 0.8 times the carapace length in M. mendagnai sp. nov., being 1.2 times that in M. angusta . Finally, the dactyli of the walking legs are very slender, with the distal third of the ventral border unarmed in M. angusta , whereas dactyli are stouter, and the distal fourth of their ventral borders are unarmed, in the new species.

Distribution: Solomon Islands, at a depth of between 340 and 432 m.

Figures

Figure 4. Munida mendagnai sp. nov., male holotype, 7.3 mm (MNHN-Ga6510). Solomon Islands. A, carapace and abdomen, dorsal view. B, sternum. C, left antennule and antenna, ventral view. D, ischium and merus of right third maxilliped, lateral view. E, right cheliped, lateral view. F, right P2, lateral view. G, dactylus, right P2, lateral view. H, right P3, lateral view. I, right P4, lateral view. Scale: A, E, F, H, I = 1 mm; B, C, D, G = 0.5 mm.