Munida oblongata, 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 : 476-478

MUNIDA OBLONGATA SP. NOV. ( FIG. 5 )

Material examined: Solomon Islands. SALOMON 2. Stn 2297, 9°05.69′S, 158°14.82′E, 8 November 2004, 728– 777 m: 1 M, 6.1 mm (holotype, MNHN-Ga6511) .

Etymology: From the Latin, oblongus, meaning longer than broad, referring to the long and slender basal segment of the antennule.

Description: Carapace 1.2 times longer than wide. A few secondary striae between main transverse ridges. Ridges with very short non-iridescent setae. Gastric region with one pair of well-developed and two pairs of small epigastric spines. Usually one parahepatic spine and one postcervical spine on each side. Frontal margins almost transverse. Lateral margins slightly convex. Anterolateral spine moderately long, near anterolateral angle, not reaching the level of the sinus between the rostrum and the supraocular spines. Second marginal spine before cervical groove smaller than preceding one. Branchial margins with five spines. Rostrum spiniform, about 0.6 times as long as remaining carapace, straight, and horizontal. Supraocular spines reaching midlength of rostrum, and not reaching end of corneae, subparallel, directed slightly upwards ( Fig. 5A ). Thoracic sternites smooth. Anterior margin of fourth sternite clearly narrower than third ( Fig. 5B ).

Second abdominal somite with row of eight spines on anterior ridge, with one transverse stria; third and fourth somites without stria.

Epistome crest without hump near mouth opening.

Eyes moderately large: maximum corneal diameter 0.3 times the distance between the bases of the anterolateral spines.

Basal segment of antennule (distal spines excluded) very long, nearly 0.5 times the carapace length, three times longer than wide (excluding spines), clearly overreaching 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, not reaching end of distolateral spine ( Fig. 5C ). First segment of antennal peduncle with one moderately long distomesial spine nearly reaching end of second segment; second segment with two distal spines, mesial spine slightly smaller than lateral spine, exceeding third segment; third segment unarmed ( Fig. 5C ).

With Mxp 3 ischium about 1.5 times the length of the merus, measured along the dorsal margin, and bearing a spine distoventrally; merus with two spines on flexor margin, distal margin smaller; extensor margin unarmed ( Fig. 5D ).

With P1s subequal in length, about 2.5 times carapace length, squamous, with numerous non-iridescent uniramous and plumose setae, denser on mesial borders of articles. Carpus four times longer than high, as long as palm; palm slightly shorter than fingers. Merus armed with some spines, strongest spines on mesial and distal margins, reaching proximal quarter of carpus. Carpus with several spines along mesial, dorsal, and lateral sides. Palm with some spines along mesial and lateral margins, a few small spines on dorsal side. Fingers unarmed, except proximal spine on movable finger, distally curving and crossing, and ending in a sharp point ( Fig. 5E ).

With P2 about 2.4 times the carapace length; merus as long as the carapace, about 7.5 times as long as high, four times the carpus length and 1.6 times as long as propodus; propodus about seven times as long as high, 1.4 times dactylus length ( Fig. 5F ). Merus with welldeveloped spines along dorsal border, increasing in size distally, ventral margin with several spines and one long distal spine. Carpus with several dorsal spines, and one distoventral spine; distal margin clearly not reaching level of merocarpal articulation of P1. Propodus with six movable ventral spinules. Dactylus slightly curving distally, with eight movable spinules along entire ventral margin, last spinule very close to the end of the dactylus ( Fig. 5G ). P3 length 0.9 times P2 length, with similar spination and article proportions as in P2 ( Fig. 5H ). P4 length 0.8 times P2 length; merus nearly half the length of the P2 merus. Merus and carpus less spinose than those of P2 and P3 ( Fig. 5I ); merocarpal articulation ending at the level of the anterior branch of the cervical groove.

Remarks: Munida oblongata sp. nov. belongs to the group of species with five spines on the lateral margin of the carapace behind the cervical groove, eyes moderately large, the second abdominal segment with spines, the lateral parts of the posterior thoracic sternites without granules, rostrum spiniform, the epistome crest without a hump near the mouth opening, the basal article of the antennular segment very elongate, with the distomesial spine clearly shorter than the distolateral spine, the distomesial spine of the second antennal article not reaching the end of the fourth article, and with the distal half of the ventral border of the dactylus unarmed. The closest relative is M. parca from New Caledonia. The two species can be distinguished according to the following characters.

1. The supraocular spines reach the midlength of the rostrum in the new species, being clearly shorter in M. parca .

2. The basal segment of the antennular peduncle is three times longer than wide (excluding spines) in the new species, being less than 2.5 times that in M. parca .

3. The distal spines of the second segment of the antennal peduncle exceed the third segment in M. oblongata sp. nov., whereas these spines never reach the end of the third segment in M. parca .

4. The dorsal side of the P1 palm is armed with rows of spines in M. parca , whereas these spines are absent in the new species.

5. The movable spinules along the flexor margin of the dactylus of P2–P4 nearly reach the tip of the article in the new species; this margin is unarmed in the distal third in M. parca . Furthermore, the dactyli are more curved in M. parca than in the new species.

On the other hand, M. oblongata sp. nov. can be easily distinguished from M. caeli sp. nov. and M. lailai sp. nov. by the following aspects.

1. The supraocular spines reach the midlength of the rostrum in M. oblongata sp. nov., being shorter in M. caeli sp. nov. and M. lailai sp. nov.

2. The basal segment of the antennular peduncle (excluding spines) is clearly longer in M. oblongata sp. nov. than in M. caeli sp. nov.

3. The distomesial spine of the second segment of the antennal peduncle overreaches the third segment in M. oblongata sp. nov., whereas in M. lailai sp. nov. the spine never reachs the end of the third segment, and in M. caeli sp. nov. the spine slightly exceeds it.

4. The dorsal side of the P1 palm is armed with rows of spines in M. caeli sp. nov. and M. lailai sp. nov., whereas these spines are absent in M. oblongata sp nov.

5. The movable spinules along the flexor margin of the dactylus of P2–P4 nearly reach the tip of the article in M. oblongata sp. nov. This margin lacks spinules in the terminal third in M.caeli sp. nov. and M. lailai sp. nov. Besides, the dactyli are more slender in M. lailai sp. nov. and M. caeli sp. nov. than in the new species.

Distribution: Solomon Islands, at a depth of between 728 and 777 m.

Figures

Figure 5. Munida oblongata sp. nov., male holotype, 6.1 mm (MNHN-Ga6511). 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, B, E, F, H, I = 1 mm; C, D, G = 0.5 mm.