Munidopsis granosicorium Williams & Baba, 1989

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 : 34-36

Munidopsis granosicorium Williams & Baba, 1989

( Fig. 12 a–k .)

Material examined

Non-type specimens. COSTA RICA: Parrita Seep, leg. Lisa Levin, Kris Krasnosky, R/V Atlantis, HOV Alvin dive 4924, 7.vi.2017, 9.03168°N, 84.62100°W, 1402 m: 1 ov. F 6.1 mm (SIO-BIC C12819).

Description

Carapace

As long as broad, widest at midlength; heavily sculptured, ridged longitudinally; convex from side to side. Dorsal surface densely covered by denticles and tubercles, each denticle or tubercle with a few short setae, epigastric denticles strongly serrated, hepatic and anterior branchial areas with denticles and some acute granules. Regions well delineated by deep furrows including distinct anterior and posterior cervical grooves. Gastric region elevated, with a longitudinal ridge interrupted by cervical groove. Cardiac region elevated, including prominent longitudinal ridge. Intestinal region with longitudinal ridge, preceded by a depression. Posterior margin unarmed, preceded by transverse depression. Rostrum narrowly triangular, width 0.23× anterior width of carapace, directed slightly upwards, few spines on margin, dorsally carinate, 0.33× carapace length, 1.4× as long as broad. Basis of rostrum armed with pair of minute spines in line with base of eye, peri-epigastric. Frontal margin slightly concave behind ocular peduncle, blunt outer orbital angle above antennal peduncle, outer orbital spine and process (antennal spine) absent. Lateral margins nearly straight; anterolateral angle unarmed; branchial margins unarmed. Pterygostomian flap surface covered by denticles and granules, anterior margin blunt, unarmed.

Sternum

1.2× longer than broad, maximum width at sternite 7. Sternite 3 broad, 2× wider than long, anterolaterally rounded, anterior margin with median lobe flanked by 2 lobes. Sternite 4 narrowly elongated anteriorly, anterior margin serrated; surface depressed in midline, smooth; greatest width 3× that of sternite 3 and 2.0× wider than long.

Abdomen

Tergites with granules, tergites 2–4 armed with a median broad spine, tergites 2–3 with 2 elevated transverse ridges, lateral part of dorsal surfaces covered by granules and scales; tergites 4–6 lacking posterior ridge; tergite 6 with weakly produced posterolateral lobes and nearly transverse posteromedian margin. Telson composed of 8 plates; 1.2× as wide as long.

Eye

Eyestalk immovable; peduncle small, shorter than cornea length; cornea globular, prominent, exposed; epistomial spine absent.

Antennule

Article 1 of peduncle with subequal dorsolateral and distolateral spines, dorsolateral double, distolateral proximally armed with denticles; distomesial margin granulate.

Antenna

Peduncle slightly exceeding eye, armed with denticles and granules; article 1 with distomesial spine, distolateral with granules and denticles. Article 2 with well-developed distomesial and distolateral spine, lateral margin with produced denticles. Article 3 with a small lateral spine, distolateral and distomesial angles unarmed. Article 4 unarmed.

Mxp3

Surface with granules and denticles. Ischium as long as merus measured on extensor margin, distal margin serrated; flexor margin of merus with 4 spines decreasing in size distally, distal margin armed with one spine; extensor margin with distal spine.

P1

Moderately slender, with numerous granules and denticles, each scale with few short setae, 1.6× longer than carapace. Merus 1.75× carpus length, with few distal stout spines. Carpus 1.8× longer than broad, with rows of spines on mesial, lateral margins, mesial stronger, distal spines stout. Palm with row of spines on all surfaces, slightly longer than carpus, 1.6× longer than broad. Fingers armed with a small spine on midlength margins, as long as palm, opposing margins nearly straight, not gaping, spooned; fixed finger without denticulate carina on distolateral margin.

P2–4

Moderately slender, coarsely tuberculated or denticulated on all surfaces, with fine distally curved setae in meri, short setae in propodi, cylindrical in cross-section, slightly decreasing in size posteriorly. P2 merus moderately slender, 0.5× carapace length, nearly 2.2× longer than high and 0.9× length of P2 propodus. P2–4 meri decreasing in length posteriorly (P3 merus 0.9× length of P2 merus, P4 merus 0.95× length of P3 merus); extensor margin with granules and denticles along entire border, distal part cylindrical ending in 1–2 thick spines; flexor margin granulated, ending in thick spine; P2–4 carpi with denticles and spines on extensor margin, acute tubercles on lateral sides; P2–4 propodi with acute tubercles on extensor margin and lateral sides, distal flattened, ending in 3 flattened denticles, 7.2–7.6× as long as high, trianguloid in cross-section, unarmed; dactyli 0.5–0.6× length of propodi; distal claw short, moderately curved; flexor margin distally curved, with 7–8 min teeth only at distal-half margin, ultimate tooth closer to dactylar angle than to penultimate tooth.

Epipods

Present on P1–3.

Eggs

2 eggs of 1.9–2 mm in diameter.

Colouration

Carapace and pereopods whitish, with brownish setae. Eyes and Mpx3 light orange. Eggs light orange.

Distribution

Vancouver Island, Washington at 2020-m depth. Newly registered from Costa Rica at 1402-m depth.

Genetic data

COI, 16S rRNA and 28S rRNA.

Remarks

The specimen described from Costa Rica fits well with the description of M. granosicorium from Vancouver Island ( Williams and Baba 1989). However, there is some morphological variation in the relative width of the rostrum, with this being lender in the Vancouver specimen and broader in the Costa Rica specimen. There are also fewer but large eggs in the specimens from Costa Rica compared to those from Vancouver, suggesting lecithotrophic larval cycle that in turn implies poor long distance dispersal ability ( Baco et al. 2016). Given the geographical distance between the two known populations, these likely correspond to different species but an analysis of more material would be necessary to confirm this. Munidopsis granosicorium belongs to the group of species with the dorsal surface of the carapace covered by tubercles, granules or denticles, epigastric processes, the lateral margins of the carapace unarmed, a triangular rostrum, the frontal margin concave behind the ocular peduncle, eyes with the ocular peduncle short and fixed, without an eye-spine and the telson composed of 7–8 plates. This species closely resembles M. follirostris Khodkina, 1973 from Chile, M. sonne Baba, 1995 from Fiji, M. tuberosa Osawa, Lin & Chan, 2008 from southwestern Taiwan and the South China Sea, and M. dispar from the Mariana Trench. However, M. granosicorium is easily distinguished from these species by the following characters:

• M. granosicorium has the carapace heavily sculptured, with a longitudinal ridge on the gastric and cardiac regions, whereas the carapace lacks these longitudinal ridges in the other species.

• M. granosicorium has the rostrum broadly triangular whereas M. follirostris , M. sonne and M. tuberosa have the rostrum constricted between the eyes.

• The rostrum is dorsally carinated in M. granosicorium but the dorsal carina is absent in M. tuberosa .

• Abdominal somites 2–5 are armed with a median broad spine in M. granosicorium whereas these spines are absent in M. dispar , M. sonne and M. tuberosa .

• The lateral margin of the antennular peduncle is unarmed in M. granosicorium , whereas this is armed with small processes in M. tuberosa .

• M. granosicorium , M. follirostris and M. sonne have epipods in P1–3 whereas M. dispar lacks epipods on pereopods.

The closest species to M. granosicorium sequenced in this study is M. dispar . The genetic divergence for M. dispar and M. granosicorium ranged from 14.7 to 16.5% for COI. Unfortunately, we do not have genetic data for M. follirostris , M. sonne or M. tuberosa .

Figures

Fig. 12. Line diagrams of Munidopsis granosicorium Williams & Baba, 1989, ov. F 6.1 mm (SIO-BIC C12819), 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) Left P1, dorsal view. (h) Right P2, lateral view. (i) Right P3, lateral view. (j) Right P4, lateral view. (k) Right P3 dactyli, lateral view. Scale bars: 1 mm.