Munidopsis testuda, Rodríguez-Flores & Seid & Rouse & Giribet, 2023

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 : 49-51

Munidopsis testuda sp. nov.

( Fig. 19 a–j .)

ZooBank: urn:lsid:zoobank.org:act:9CD8FBD7-C6D7-410D-9D30-C367 EDF0B7AF

Material examined

Holotype. ECUADOR: Galapagos Archipelago, leg. R/V Thomas Washington, Stn PLUM 02 WT, Rock Dredge D- 08, 23.i. 1990, 1.11683°N, 88.26283°W, 1000– 917 m: ov. F 15.1 mm, 2 eggs ( SIO-BIC C9639 ).

Etymology

From the Latin testudo (meaning ‘turtle’), referring to Galapagos Islands but also the squamate carapace of the species, like a turtle shell.

Diagnosis

Carapace dorsally covered in granules and scales, wider scales at posterior, with dorsal deep furrows, cervical grooves distinct. Rostrum broad, dorsally elevated, spadeshaped, dorsally carinate, distally armed with 2 spines. Frontal margin nearly straight, spine below antennal angle. Orbit not excavated, outer orbital angle with a blunt lobe. Anterolateral angle armed with a spine. Branchial margin armed with a spine. Abdominal somites unarmed. Telson divided into 7 plates. Sternite 3 anterolaterally rounded, anterior margin with median lobe flanked by 2 lobes, sternite 4 narrowly subtriangular. Eyes unarmed, movable, epistomial spine present, cornea elongated. Article 1 of antennule with dorsolateral and distolateral spines, distolateral double. Article 1 of antenna with strong distomesial spine and distolateral spines. Mxp3 merus rectangular in lateral view. P1 stout, unarmed, fixed finger without denticulate carina on distolateral margin. P2–4 stout, unarmed; meri carinated, dactyli slender, curving, flexor margin with minute teeth along all margins decreasing proximally. Epipods present on P1–2.

Description

Carapace

Slightly broader than long, widest at midlength; moderately convex from side to side. Dorsal surface densely covered in granules and scales, each scale with a few short setae; hepatic and anterior branchial areas with scales and some acute granules; posterior cardiac and intestinal region covered in larger scales. Regions well delineated by deep furrows including distinct anterior and posterior cervical grooves. Gastric region slightly elevated. Posterior margin unarmed, preceded by elevated ridge. Rostrum broad, dorsally elevated, spade-shaped (lateral margins constricted between eyes), width 0.2× anterior width of carapace, directed slightly upwards, dorsally carinate, distally armed with 2 broad spines; 0.4× carapace length, 1.8× as long as broad. Frontal margin nearly straight behind ocular peduncle, blunt outer orbital angle above antennal peduncle, outer orbital spine and process (antennal spine) absent; spine below antennal angle, ventral to frontal margin, close to epistomial spine. Lateral margins straight; anterolateral spine broad; anterior branchial margin with one broad spine; one broad branchial spine behind posterior branch of cervical groove. Pterygostomian flap surface covered in granules and scales, anteriorly acute.

Sternum

0.9× as long as broad, maximum width at sternite 6. Sternite 3 broad, 3.2× wider than long, anterolaterally rounded, anterior margin with median lobe 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

Unarmed; tergite 2 with 2 elevated transverse ridges, lateral parts of dorsal surfaces covered in granules and scales; tergites 3–6 lacking a posterior ridge; tergite 6 with weakly produced posterolateral lobes and nearly transverse posteromedian margin. Telson composed of 8 plates; 1.5× as wide as long.

Eye

Eyestalk movable, partially concealed by rostrum; peduncle covered with a few granules, shorter than cornea length; cornea ovoid and elongated; lateral surface contiguous to epistomial spine, epistomial spine ventral to frontal margin.

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 distomesial spine and distolateral spines, not reaching end of article 2. Article 2 with well developed distomesial and distolateral spines, distomesial margin granulated. Articles 3–4 unarmed.

Fig. 19 . (Caption on next page)

Mxp3

Surface with granules. Ischium as long as merus measured on extensor margin; flexor margin of merus with 3 spines subequal in size and a smaller distal spine; extensor margin with 6 granules or blunt spines.

P1

Stout, with numerous minute granules and scales, each scale with few short setae, 1.3× longer than carapace. Merus 2.2× carpus length, with distal stout spines. Carpus 0.9× longer than broad, with some distal stout spines, a few acute granules along dorsal side. Palm unarmed, stout, slightly longer than carpus, 1.2× longer than broad. Fingers unarmed, 1.2× longer than palm, opposing margins nearly straight, not gaping, spooned; fixed finger without denticulate carina on distolateral margin.

P2–4

Stout, coarsely granulated, devoid of setae, cylindrical in cross-section, slightly decreasing in size posteriorly. P2 merus stout, 0.6× carapace length, 2.7× 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 0.85× length of P3 merus); extensor margin of P2–4 meri carinate, with small granules along entire border, distal part flattish ending in thick spine; flexor margin granulated; carpi with one thick distal spine on extensor margin, granulated carina along lateral side; P2–4 propodi 5.1–5.2× as long as high, trianguloid in cross-section, unarmed; dactyli 0.5× length of propodi; distal claw short, moderately curved; flexor margin distally curved, with 11–12 dactylar teeth at entire margin, each with slender corneous spine, ultimate tooth closer to penultimate tooth than to dactylar angle.

Epipods

Present on P1–2.

Colouration

Unknown.

Distribution

Galapagos Islands, at 917–1000-m depth.

Genetic data

COI, 16S rRNA and 28S rRNA.

Remarks

The new species represents a highly divergent lineage that shares a trifid rostrum with the trifida -group ( Fig. 1 , 2 ): e.g. M. trifida from East Pacific, M. ahyongi Dong & Li, 2021 and M. comarge from the West Pacific. M. testuda sp. nov., however, does not have a close relationship or share a common ancestor with this group of species ( Fig. 1 , 2 ) and differs from this group in having epipods on P1–2 instead of having pereopods without epipods or only in P1, and a carapace that is as long as broad instead of broader than long. The new species is closely related to M. carolinensis Dong & Li, 2021 from the Caroline Ridge in the tropical West Pacific and M. expansa Benedict, 1902 from off Florida and the Caribbean Sea. However, the new species can be distinguished from the other species by the following morphological characters:

• The rostrum is triangular in M. carolinensis and M. expansa whereas this is spade-shaped and constricted between the eyes in the new species.

• The scales on the carapace and pereopods are smaller and less dense in M. carolinensis and M. expansa than in the new species.

• The new species has an additional pair of spines apart from the epistomial spines, each lateral to the eyestalk and ventral to the frontal margin, whereas this pair of spines is absent in M. carolinensis and M. expansa .

• The new species has epipods on pereopods 1–2 whereas M. carolinensis has pereopods without epipods.

Munidopsis testuda sp. nov. and M. carolinensis diverge on 18% for COI. Unfortunately, no molecular data are available for M. expansa .

Figures

Fig. 19. Line diagrams of Munidopsis testuda sp. nov., ov. F 15.1 mm, holotype (SIO-BIC C9639), Ecuador: Galapagos. (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.

Fig. 1. Phylogenetic hypothesis of the concatenated data set (COI + 16S rRNA + 28S rRNA) resulting from the ML analysis. Tip labels in bold indicate new taxa. Asterisks indicate supported nodes: ML bootstrap support>70%/Bayesian posterior probability>0.95.

Fig. 2. Phylogenetic hypotheses based on the COI data alone resulting from the Bayesian analysis, with results from the species delimitation analyses (ASAP, ABGD, bPTP, GMYC); a grey box indicates that the specimens are not part of the species hypothesis of the black bar. Tip labels in bold indicate new taxa. Colours indicate geographic distribution as specified on the map. Gradients of depth and habitat are also indicated. Asterisks indicate supported nodes: ML bootstrap support>70%/Bayesian posterior probability>0.95.