Munidopsis sedna, Rodríguez-Flores & Ambler & Nizinski, 2024

Rodríguez-Flores, Paula C., Ambler, Julie W. & Nizinski, Martha S., 2024, Integrative taxonomy reveals a new species of deep-sea squat lobster (Galatheoidea, Munidopsidae) from cold seeps in the Gulf of Mexico, Zoosystematics and Evolution 100 (4), pp. 1243-1257 : 1243-1257

Munidopsis sedna sp. nov.

Figs 4 , 5 , 6 A, B , 7

Munidopsis sp. nov. 1: Bergquist et al. (2003), p. 205, 206, 210, 216.

Munidopsis sp.: Fisher et al. (2007), p. 123.

Munidopsis sp. 1: Cordes et al. (2008), p. 781, 783, 786.

Munidopsis sp. (small): Lessard-Pilon et al. (2010), p. 1894, 1885, 1896, 1897.

Material examined.

Holotype. Gulf of Mexico, United States, Green Canyon, Block 246 , 27.6897 ° N, 90.6450 ° W, coll. TDI-Brooks International, E. Cordes & C. Fisher, LOPH II, Jason II ROV; Ronald H. Brown R / V, Cruise # RB- 10-07, Stn GC 246, sample # MMS-LOPH / II / J 2-528 / GC 246, 17 - Oct- 2010: M 9.7 mm ( USNM 1407437 ).

Paratypes. Gulf of Mexico, United States, Green Canyon, Block 246, 27.6897 ° N, 90.6450 ° W, coll. TDI-Brooks International, E. Cordes & C. Fisher, LOPH II, Jason II ROV; Ronald H. Brown R / V, Cruise # RB- 10-07, Stn GC 246, sample # MMS-LOPH / II / J 2-528 / GC 246, 17 - Oct- 2010: 1 M 7.9 mm ( USNM 1407438). — Green Canyon, Block 246, 27.6897 ° N, 90.6450 ° W, col. TDI-Brooks International, E. Cordes & C. Fisher, LOPH II Jason II ROV; Ronald H. Brown R / V, Cruise # RB- 10-07, Stn GC 246, sample # MMS-LOPH / II / J 2-528 / GC 246, 17 - Oct- 2010: 1 M 6.9 mm ( USNM 1407439) — Green Canyon, Block 246, 27.6897 ° N, 90.6450 ° W, coll. TDI-Brooks International, E. Cordes & C. Fisher, LOPH II Jason II ROV; Ronald H. Brown R / V, Cruise # RB- 10-07, Stn GC 246, sample # MMS-LOPH / II / J 2-528 / GC 246, 17 - Oct- 2010: 1 M 8.1 mm ( USNM 1407440). — Green Canyon, Block 246, 27.6897 ° N, 90.6450 ° W, coll. TDI-Brooks International, E. Cordes & C. Fisher, LOPH II Jason II ROV; Ronald H. Brown R / V, Cruise # RB- 10-07, Stn GC 246, sample # MMS-LOPH / II / J 2-528 / GC 246, 17 - Oct- 2010: 1 M 4.1 mm, 1 F 2.7 mm ( USNM 1407474). — Green Canyon 234 27.7461 ° N, 91.2211 ° W, coll. C. Fisher, CHEMO, Seward Johnson II R / V; Johnson Sea Link DSR / V, Cruise # 4436, Stn GC 234, sample # CHEMO / JSL / 4436, 534 m, 24 - Jun- 2002, 1 M 10.3 mm ( USNM s). — Green Canyon 234, 27.7461 ° N, 91.2211 ° W, coll. C. Fisher, CHEMO, Johnson Sea Link DSR / V, Cruise # 4588, Stn GC 234, sample # CHEMO / JSL / 4588 534 m, 5 - Sep- 2003: 34 M 3.3–9.1 mm, 22 ov. F 4.5–7.6 mm, 17 F 3.6–7.2 mm, 7 specimens with rhizocephalan barnacles parasites ( USNM 1666805). — Garden Banks 535, 27.4289 ° N, 93.5897 ° W, coll. C. Fisher, CHEMO, Johnson Sea Link DSR / V, Cruise # 4583, Stn GB 535, sample # CHEMO / JSL / 4583, 575 m, 3 - Sep- 2003: 4 M 4.5–7.9 mm, 4 ov. F 5.2–9.4 mm, 3 F 4.8–8.0 mm, 1 juv 3 mm ( USNM 1666806). Bush Hill, Green Canyon, 27.780300 ° N, 91.5064 ° W, col. C. Fisher, CHEMO, Johnson Sea Link I DSR / V; Seward Johnson R / V, Cruise # JSL I 1991, sample # JSL 3129, 549 m, 15 - Sep- 1991: 1 M 8.5 mm ( USNM 1704816). — 180 km south of New Orleans, LA, Gulf of Mexico, Brine Pool NR 1 cold seep, 27.7230 ° N, 91.2750 ° W, coll. R. Vrijenhoek et al., R / V Seward Johnson I and II, 650 m, 3 - Oct- 2001: 6 M 7.75–10.11 mm, 7 ov. F 6.72–9.9 mm, 1 F 8.91 mm ( SIO-BIC C 13985).

Other material.

For comparison, additional material of Munidopsis sedna sp. nov., M. longimanus , and M. brevimanus (A. Milne-Edwards, 1880) was examined (see Suppl. material 1).

Etymology.

In Inuit mythology, Sedna is the goddess of the sea and marine animals, also known as the Mother or Mistress of the Sea. The specific name is substantive in apposition.

Diagnosis.

Carapace, excluding rostrum as long as broad, dorsal surface nearly smooth or covered with small granules. Rostrum broadly triangular, not acute at tip, ca. one-third carapace length. Frontal margin without delimited orbit, transverse. Cervical grooves distinct. Lateral margins subparallel, without distinct spines. Sternum longer than wide, maximum width at sternites 4 to 6; sternite 3 short and wide, width about half that of sternite 4. Abdomen spineless; telson with 10 plates. Eyes small, movable, and unarmed; cornea small, slightly elongated; peduncle larger than cornea. Antennular article 1 swollen laterally. Basal part of each Mxp 3 not separated by an appreciable gap; merus with 2 acute spines on flexor margin. P 1 long and slender, more than twice carapace length, longer than P 2. P 2 –4 moderately stout; extensor margin of articles carinate; propodi not expanded distally; dactyli curved distally; flexor margin with row of 8–12 teeth bearing corneous spinules. Epipods absent from all pereiopods.

Description.

Carapace: As long as broad, widest at posterior part; convex from side to side. Dorsal surface sparsely covered with small granules or nearly smooth, hepatic and anterior branchial areas with minute granules or smooth. Regions well delineated by furrows, anterior and posterior cervical grooves distinct. Gastric region slightly convex. Posterior margin unarmed, dorsally smooth. Rostrum spatulate, horizontally straight, 0.3 – [0.4] times carapace length, 0.2 – [0.3] times anterior width of carapace, [1.2] – 1.9 times as long as wide; dorsal surface concave, with small granules. Frontal margin straight behind ocular peduncle; outer orbital angle not produced, concave; orbit not delimited. Lateral margins straight, no spines; anterolateral angle not produced; blunt, sparsely granulate; branchial margins granulate; deep notch between hepatic and branchial margins. Epistomial spine absent. Pterygostomian flap surface covered with small granules, anterior margin blunt.

Sternum: Slightly longer than broad, maximum width at sternites 4 to 6. Sternite 3 broad, [3.0] times wider than long, anterolaterally produced and often serrated; anterior margin with broad median notch flanked by 2 lobes. Sternite 4 widely elongate anteriorly; anterior margin often serrated; surface depressed in midline, smooth; greatest width [3.3] times that of sternite 3 and [2.1] times length.

Abdomen: Unarmed. Tergites often with small sparse granules on all surfaces; tergites 2–3 each with 1 elevated transverse ridge; tergites 4–6 without ridges; tergite 6 with weakly developed posterolateral lobes and nearly transverse posteromedian margin. Telson composed of 10 plates; [0.7] times as wide as long.

Eye: Eyestalk movable, partially concealed beneath rostrum; peduncle elongated, smooth, [2.7] times as wide as long; cornea ovoid, narrower than peduncle; length [1.3] times that of peduncle.

Antennule: Article 1 of peduncle with dorsolateral and distolateral spines subequal in size; distolateral margin with denticles; distomesial margin with smaller denticles.

Antenna: Peduncle usually not exceeding eye, armed marginally with denticles and granules. Article 1 with small distolateral spine, distomesial angle produced but unarmed. Article 2 unarmed or with minute distomesial and distolateral spine. Article 3 with small distomesial and distolateral spines or with prominent distal denticles. Article 4 unarmed.

Mxp 3: Lateral surface with scattered granules. Ischium [1.1] times longer than merus measured on extensor margin; distal extensor margin serrated. Flexor margin of merus with 2 prominent proximal spines subequal in size and small distal spine; extensor margin with several denticles and small or large distal spine. Carpus with several denticles on dorsal surface.

P 1: Slender, 2.4–2.8 (females) and 3.0 – [3.7] (males) times longer than PCL, cylindrical. Merus 3.0 – [3.6] times as long as carpus, with denticles and granules. Carpus [1.1] – 1.5 times longer than broad, unarmed. Palm unarmed, slender, [2.8] – 3.0 times longer than carpus, [2.5] – 2.8 times as long as broad. Fingers unarmed, smooth, [0.6] – 0.7 times longer than palm; opposable margins nearly straight, gaping, distally spoon-shaped; fixed finger without denticulate carina on distolateral margin. Heterochely present in some specimens.

P 2 – 4: Moderately stout, subcylindrical, flattened in cross-section, slightly decreasing in size posteriorly; surfaces with some denticles and granules. P 2 merus moderately slender, [0.7] times PCL, nearly [3.5] times longer than high, [1.3] times length of P 2 propodus. Meri decreasing in length posteriorly (P 3 merus [0.9] length of P 2 merus, P 4 merus [0.9] length of P 3 merus); extensor margin strongly carinate, distal part ending in thick spine; flexor margin with a row of spines. Carpi with spines on each extensor margin, 2 parallel granulate carinas along dorsal side. Propodi 4.5–5.2 times as long as high, flattened in cross-section, with some tubercles proximally on each extensor margin; lateral surface with some small spines on proximal half; flexor margin unarmed. Dactyli moderately slender, 0.5–0.6 times length of propodi; distal claw short, moderately curved distally; flexor margin nearly straight, armed with 8–12 corneous spines.

Epipods absent from pereiopods.

Eggs: About 5–25 rounded eggs of about 1 mm each.

Coloration: Carapace and abdomen orange, white stripe in midline. Eyes light orange. Pereopods orange or light orange, whitish distally.

Distribution.

Gulf of Mexico, from 479 to 1,250 m depth.

Habitat.

All specimens examined were collected from cold seeps or associated with the seep communities surrounding brine pools.

Genetic data.

COI, 16 S rRNA, and 28 S rRNA (see Table 1 ).

Remarks.

The new species belongs to the Elasmonotus group (A. Milne Edwards, 1880), characterized by species having a carapace with a transverse frontal margin, without a delimited orbit, an elongated cornea, and the dorsal surface of the carapace usually smooth. Within the Elasmonotus group, Munidopsis sedna sp. nov. is morphologically similar to M. brevimanus and M. longimanus ; however, the new species can be distinguished from these other species by the following morphological characters:

The abdominal tergites 2–4 are smooth and unarmed in M. sedna , whereas they are armed with a broad median spine covered with tubercles in M. longimanus and M. brevimanus .

The carapace ornamentation is smooth and / or sparsely granulated in the new species, whereas it is highly tuberculate and porose in M. brevimanus and M. longimanus , respectively.

The P 1 is longer and more slender in the new species than in M. brevimanus .

The abdomen is more elongated in dorsal view in M. longimanus and M. brevimanus than in the new species, whereas the rostrum is relatively shorter in the new species.

Mayo (1974) discussed the differences between M. brevimanus and M. longimanus in detail. The main differences between these two species are the relative length of the P 1, which is much shorter and stouter in M. brevimanus than in M. longimanus (and also in the new species); and the relative length of the median spines on the abdominal tergites 2–4, which are less projected in M. brevimanus than in M. longimanus (the spines are absent in the new species). Nevertheless, M. longimanus females and juveniles seem to have fewer projected abdominal spines ( Mayo 1974; this work). The overlap of morphological characters and the general similarity of these two species led of M. brevimanus being considered a junior subjective synonym of M. longimanus (see A. Milne-Edwards and Bouvier 1894: 283). However, after further examination of the type specimens of the two species and other material, Chace (1942) resurrected M. brevimanus as a valid taxon; this taxonomical decision was later confirmed by Mayo (1974).

Figures

Figure 4. Line drawings of Munidopsis sedna sp. nov., Gulf of Mexico, holotype, male 9.7 mm (USNM 1407437). A. Carapace and abdomen, dorsal view; B. Thoracic sternum, ventral view; C. Telson; D. Right part of the cephalothorax, ventral view, showing antennular article 1 and antennal peduncle, and anterior part of the pterygostomian flap; E. Left Mxp 3, lateral view; F. Right P 1, dorsal view; G. Left P 2, lateral view; H. Left P 3, lateral view; I. Left P 4, lateral view; J. Left P 2 dactylus, lateral view. Scale bars: 1 mm.

Figure 5. Drawings of Munidopsis sedna sp. nov., Gulf of Mexico, paratype, male 8.5 mm (USNM 1704816). A. Carapace and abdomen, lateral view; B. Carapace and abdomen, dorsal view; C. Telson; D. Right Mxp 3, lateral view; E. Sternites 3 and 4, ventral view; F. Right P 1, dorsal view. Scale bars: 4 mm (A, B, F); 2 mm (C, E); 1 mm (D).

Figure 6. 3 D renderings of micro-computed tomography x-ray images. A, B. Munidopsis sedna sp. nov., Gulf of Mexico, male, paratype (USNM 1666822); C, D. Munidopsis longimanus, Guadeloupe (MNHN - 2013-18823).

Figure 7. In situ image of Munidopsis sedna sp. nov. in a brine pool in the Gulf of Mexico. Photo courtesy of the BBC.