Munidopsis margarita Faxon, 1893

Rodríguez-Flores, Paula C., Seid, Charlotte A., Rouse, Greg W. & Giribet, Gonzalo, 2023, Cosmopolitan abyssal lineages? A systematic study of East Pacific deep-sea squat lobsters (Decapoda: Galatheoidea: Munidopsidae), Invertebrate Systematics 37 (1), pp. 14-60 : 39-43

Munidopsis margarita Faxon, 1893

( Fig. 15 a–j .)

Material examined

Lectotype. ECUADOR: Galápagos , Off Galapagos Islands , leg. USFC Steamer Albatross, Stn 3404, 28.iii.1891, 1.05000°S, 89.46666°W, 385 fms (704 m): M 7.5 mm ( MCZ IZ CRU-4551 ).

Paralectotype. Same collecting data as lectotype: 1 F 6.5 mm ( MCZ IZ-163061 ).

Non-type material. COSTA RICA: Seamount 6, leg. Greg Rouse, Avery Hiley, R/V Falkor, ROV SuBastian dive S0227, B3-7, 22.i.2019, 7.67944°N, 85.91141°W, 578 m: 1 F broken 8.9 mm (SIO-BIC C13957).

h, d, c

Description

Carapace

Spinose, slightly broader than long, widest at midlength; moderately flattened from side to side. Dorsal surface densely covered in spines and a few scales, each scale with a few setae; pair of epigastric spines strong, median processes with long setae, hepatic and anterior branchial areas with spinules; posterior cardiac and intestinal region covered with spinules and scales. Regions well delineated by deep furrows including distinct anterior and posterior cervical grooves. Gastric region elevated. Posterior margin armed with 3 pairs of spines, 2 median pairs (median pair the strongest) and 1 lateral pair, close to the carapace margin, posterior margin preceded by a depression. Rostrum triangular, width 0.2× anterior width of carapace, directed slightly upwards, dorsally carinate, margin distally armed with 5 small spines; 0.4× carapace length, 1.8× as long as broad. Frontal concave behind ocular peduncle, blunt outer orbital angle above antennal peduncle, ending in a small outer orbital spine (antennal spine). Lateral margins straight; anterolateral spine strong; anterior branchial margin with 6 spines, each pair constituting a strong spine followed by a small spine; 5–6 branchial spines behind posterior branch of cervical groove. Pterygostomian flap surface covered in granules, anteriorly acute, armed with a strong spine.

Sternum

0.9× as long as broad, maximum width at sternite 7. Sternite 3 broad, 3.2× wider than long, anterolaterally rounded, anterior margin with median notch flanked by 2 lobes. Sternite 4 narrowly elongated anteriorly; surface depressed in midline, smooth; greatest width 2.3× that of sternite 3 and 1.7× wider than long.

Abdomen

Tergites 2–3 armed with posterolateral broad spines, tergite 2 with 3 spines and 2 elevated transverse ridges, tergite 3 armed with 1 median spine, tergites 3–6 lacking a posterior ridge; tergite 6 with weakly produced posterolateral lobes and nearly transverse posteromedian margin. Telson composed of 7 plates; 1.2× as wide as long.

Eye

Eyestalk movable; peduncle forming a median spine, projecting from upper surface and exceeding cornea, peduncle shorter than cornea length; cornea subglobular; epistomial spine absent.

Antennule

Article 1 of peduncle with subequal dorsolateral and distolateral spines; distomesial margin slightly produced and granulated.

Antenna

Peduncle slightly exceeding eye. Article 1 with strong distolateral spine, not reaching end of article 2. Article 2 with well-developed distolateral spine, distomesial margin granulated. Article 3 with well-developed distomesial and distolateral spine. Article 4 unarmed.

Mxp3

Surface with granules. Ischium as long as merus measured on extensor margin; flexor margin of merus with 3 strong spines subequal in size; extensor margin with 2 small spines.

Slender, spinose, with numerous spines. Merus 2.7× carpus length, with rows of strong spines at lateral and mesial margins. Carpus 0.9× longer than broad, with rows of strong spines on dorsal, mesial and lateral surfaces. Palm armed with row of strong spines on mesial margin, lateral margin irregular, with few spines, slender, 2.3× longer than carpus, 1.2× longer than broad. Movable finger armed with a basal spine, 0.9× longer than palm, opposable margins nearly straight, not gaping, spooned; fixed finger without denticulate carina on distolateral margin.

P2–4

Slender, spinose, cylindrical in cross-section. P2 merus slender, 0.6× carapace length, 4× longer than high and 1.1× length of P2 propodus. P2–4 meri decreasing in length posteriorly (P3 merus 0.9× length of P2 merus, P4 merus 0.8× length of P3 merus); extensor margin of P2 and 4 meri with strong spines on all surfaces, distal part flattish, terminating in a thick spine; flexor margin with spines; carpi with spines on extensor margin, distal spine strong, carina along lateral side; P2 and 4 propodi 5.1–5.2× as long as high, trianguloid in cross-section, armed with small spines on lateral and extensor surfaces; dactyli 0.5× length of propodi; distal claw short, moderately curved; flexor margin distally curved, with 11–14 teeth at midlength, ultimate tooth at midlength between penultimate tooth and dactylar angle.

Epipods

Absent from pereopods.

Colouration

Carapace and eyes deep orange, P1–4 colourless.

Distribution

Previously known from Galapagos at 704-m depth. Newly registered from Costa Rica, at 578-m depth.

Genetic data

COI, 16S rRNA and 28S rRNA.

Remarks

Munidopsis margarita belongs to the group of species having a frontal margin with a delimited orbit, movable eye with small median spine projecting from upper surface, the abdomen armed with spines and the telson composed of 7–8 plates. This group includes M. hystrix , M. opalescens and M. margarita , and these are morphologically and genetically close. These species can be distinguished based on the following morphological characters:

• The spines on the carapace and rostrum margin are more prominent in M. opalescens and M. margarita than in M. hystrix .

• The rostrum is spiniform in M. hystrix but triangular in M. opalescens and M. margarita .

• Munidopsis margarita has abdominal tergites 2–3 armed with posterolateral spines, whereas these spines are absent in the other species.

• Munidopsis margarita has abdominal tergite 2 armed with 3 or more spines whereas this tergite is armed with a single median spine in the other species.

Genetic divergences among these species ranged from 6.8 to 10% for COI.

Figures

Fig. 15. Line diagrams of Munidopsis margarita Faxon, 1893, 1 F broken 8.9 mm (SIO-BIC C13957), Costa Rica. (a) Carapace and abdomen, dorsal view. (b) Carapace and abdomen, lateral view. (c) Sternal plastron. (d) Telson. (e) Cephalic region, showing antennular and antennal peduncles, ventral view. (f) Left Mxp3, lateral view. (g) Right P1, dorsal view. (h) Right P2, lateral view. (i) Right P3, lateral view. (j) Right P4, lateral view. (k) Right P4 dactyli, lateral view. Scale bars: 1 mm.