Gonionida kaimei Komai & Tsuchida & Fujiwara 2023, n. sp.
Creators: name: Komai, Tomoyuki
name: Tsuchida, Shinji
name: Fujiwara, Yoshihiro
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Munididae
Gonionida
Gonionida kaimei

description: Gonionida kaimei n. sp.
[New Japanese name: Kaimei-chu-koshiori-ebi]
(Figs. 1–3)
Type material. Holotype: JAMSTEC 105802, male (cl 7.6 mm), R / V Kaimei, KM20-10 cruise, KM-ROV dive #125, Shoho Seamount, Nishi-Shichito Ridge, 32°19.39’N, 138°44.48’E, 456.9 m, 30 November 2020, suction sampler, DNA voucher (see Table 1).
Description. Carapace (Fig. 1A) 1.2 times longer than wide. Dorsal surface gently convex transversely; main transverse ridges mostly not interrupted; few secondary transverse striae present between main ridges; most ridges and striae with dense short, non-iridescent setae. Rostrum spiniform, 0.5 times as long as carapace, directed forward, faintly sinuous in lateral view; dorsal carina not clearly delimited. Supraocular spines relatively long and slender, nearly parallel to rostrum in dorsal view and very slightly ascending in lateral view, 0.4 length of rostrum. Gastric region slightly elevated, with 4 pairs of epigastric spines and minute median tubercle aligned, spine posterior to base of supraocular spine strongest; anteriormost transverse ridge (just behind epigastric spines) consisting of small, scale-like ridges. Cervical groove distinct. One parahepatic, 1 anterior branchial and 1 post-cervical spines present on each side, parahepatic spine strongest. Anterior part of branchial region with few striae. Lateral part of posterior branchial region with 5 transverse ridges or striae (excluding posterior transverse ridge). Intestinal region with 1 short, arcuate, stria on median part. Posterior transverse ridge without stria. Frontal margins slightly oblique. Lateral margins faintly convex in dorsal view. Anterolateral spine located at anterolateral angle, rather long, reaching sinus between rostrum and supraocular spines, slightly divergent; no spine on frontal margin mesial to anterolateral angle. Hepatic margin with 1 main spine and 1 additional spinule, main spine about 0.3 length of anterolateral spine. Branchial margins each with 5 moderately small spines, anteriormost spine larger than others.
Orbit with 1 spinule directed anterolaterally.
Pterygostomial flap unarmed on anterior margin (Fig. 1E); lateral face strongly rugose with irregular transverse or obliquely transverse ridges.
Epistomial ridge sinuous, ending anterior to excretory pore of article 1 of antennal peduncle.
Thoracic sternum (Fig. 1B) distinctly wider than long, widest at sternite 7. Sternite 3 3.9 times wider than long, slightly wider than anterior margin of sternite 4, narrowly separated from sternite 4; anterior margin minutely granulate, bilobed with distinct median notch; anterolateral angles subacute. Sternite 4 with few short striae medially; anterolateral margins faintly granulate. Sternites 5–7 smooth, without striae. Sternites 6 and 7 without carinae or granules on lateral parts. Transverse ridges nearly smooth, with row of short setae.
Pleomere 1 tergite (Fig. 1A) with several punctae. Pleomere 2 (Fig. 1A) anterior ridge bearing 4 pairs of relatively large spines; tergum with 1 main transverse ridge 2 transverse striate (anterior striae widely interrupted, posterior striae complete; pleuron with a few short striae. Pleomere 3 (Fig. 1A) anterior ridge unarmed; tergum with 1 main transverse ridge and 1transverse striae anterior to main ridge; pleuron with few arcuate striae. Pleomere 4 with anterior ridge unarmed; tergum with 1 main transverse ridge, 2 transverse striae interrupted medially; pleuron with few arcuate striae. Pleomere 5 with 1 main transverse ridge, 2 transverse striae on tergum; pleuron with few striae. Pleomere 6 (Fig. 1C) with 2 pairs of oblique striae anterolaterally; tergum with W-shaped striae posteriorly. Telson (Fig. 1C) 1.4 times wider than long, incompletely divided into 4 main plates (division between lateral and posterolateral plates indistinct); surface with scattered squamiform ridges; posterior margin divided into 2 rounded lobes by deep median notch.
Eyes (Fig. 1A) large. Cornea strongly dilated, corneal width much greater than sinus between rostrum and supraocular spine and 0.4 of distance between anterolateral spines of carapace. Ocular peduncle narrowed proximally, without setiferous striae on dorsal surface; setae consisting of eyelash short.
Antennular peduncle basal article (Fig. 1D) relatively slender, overreaching distal corneal margin, length excluding distal spines twice of width; distal spines moderately long and slender, unequal with distomesial spine distinctly shorter than distolateral spine; ventral surface with several squamiform ridges; 2 lateral spines present, first spine overreaching distolateral spine, arising at about midlength of segment, second spine short, located just lateral to base of first spine; statocyst lobe slightly inflated.
Antennal peduncle (Fig. 1E) moderately stout, reaching midlength of eye. Article 1 with moderately long distomesial spine reaching mid-length of article 2; distolateral margin barely produced, unarmed. Article 2 without striae on ventral surface; distomesial spine obliquely directed, reaching distal margin of article 3; mesial margin with 3 minute denticles; distolateral spine shorter than distomesial spine, directed distally, reaching mid-length of article 3. Articles 3 and 4 unarmed.
Maxilliped 3 moderately slender. Ischium with small flexor distal spine; lateral surface with irregularly tuberculate median ridge and short transvers ridges or striae. Merus (Fig. 1F) with 2 greatly unequal spines on flexor margin, proximal spine much stronger than distal spine; 1 minute additional denticle between two main flexor spines; extensor distal margin unarmed; lateral surface with some tiny scale-like ridges. Carpus smooth on extensor surface. Propodus slightly longer than carpus, not particularly expanded. Dactylus shorter than propodus.
Cheliped (Figs. 1G, 2A–C, 3) about twice as long as carapace, equally broad generally on merus, carpus and palm; mesial surface of merus to palm with mixture of short plumose setae and long, stiff iridescent setae. Merus surfaces squamous, with longitudinal row of 7 spines on dorsal midline (spines noticeably increasing in size distally) and 2 spines distomesially, distomesial spine prominent, strongly diverging, thus falling far short of midlength of carpus, second spine much shorter than distolateral spine, located slightly proximal to base of distomesial spine; ventrolateral distal angle with small spine; mesial face with 1 small spine in addition to strong ventromesial distal spine. Carpus subequal in length to palm, 1.7 times longer than wide (excluding spines); dorsal surface with median row of 3 spines increasing in size distally and 2 mesial spines, dorsomesial margin with 4 spines increasing in size distally, in addition to tiny spine at distomesial angle; mesial surface with 1 small subdistal spine; ventrolateral distal angle with tiny spine; ventral surface squamous. Palm parallel-sided, 1.9 times longer than wide; dorsal surface with median row of 5 spines, 1 spine at articulation to dactylus, without squamiform tubercles or ridges; dorsolateral margin with 6 spines extending onto proximal 0.3 of fixed finger, dorsomesial margin with 3 spines; mesial face with 1 strong spine medially; ventral surface with 1 small spine at articulation to dactylus and scattered squamiform tubercles. Fixed finger nearly straight, with 2 small subterminal spines; dorsal surface with few granules; occlusal margin with row of minute, acute or subacute denticles. Dactylus 1.3 times longer than palm, terminating in sharp, curved claw crossing tip of fixed finger; mesial margin with 1 slender proximal spine only; dorsal surface unarmed; occlusal margin with row of minute denticles over entire length. No hiatus between dactylus and fixed finger.
Ambulatory legs (pereopods 2–4) (Figs. 2D, F, G, 3) moderately long and stout, decreasing in length posteriorly; dorsal or extensor margins or meri, carpi and propodi with sparse row of long iridescent setae (longest on propodi). Pereopod 2 (Fig. 2D) about twice as long as carapace, far overreaching tip of anterolateral spine on carapace by mero-carpal articulation. Merus subequal in length to carapace, 5.8 times longer than high; dorsal margin with row of 11 spines (distal spine strongest); ventral margin with 1 strong distal spine followed by 3 smaller spines and several short transverse ridges, lateral face only with few tiny ridges. Carpus about 0.4 length of propodus, with 4 spines noticeably increasing in size distally on extensor margin; flexor distal margin produced in strong spine; lateral surface with longitudinal ridge adjacent to extensor margin. Propodus with 1 minute spine proximally, lateral face almost smooth; flexor margin with row of 10 equidistant movable spines, basal protuberance of ultimate spine bearing tiny fixed spine. Dactylus (Fig. 2E) 0.6 times as long as propodus and 4.9 times as long as high, slightly curved in distal part, bearing sparse short to long stiff setae on extensor margin; lateral surface with row of short, curled setae slightly diverging against extensor margin; flexor margin faintly sinuous, with 9 corneous spinules increasing in length distally along over entire length; slender subterminal spinule at base of unguis.
Pereopod 3 (Fig. 2F) similar to pereopod 2, reaching anterolateral angle of carapace by mero-carpal articulation. Merus 0.8 length of that of pereopod 2; dorsal margin with row of 8 spines; ventral margin with strong distolateral spine followed by 2 small spines and several transverse ridges. Carpus with 3 spines on extensor margin; ventrodistal margin produced into strong spine. Propodus with 9 movable spines on flexor margin. Dactylus with 7 corneous spinules and subterminal spinule at base of unguis on flexor margin.
Pereopod 4 (Fig. 2G) reaching nearly to lateral end of cervical groove of carapace by mero-carpal articulation. Merus 0.7 length of that of pereopod 2; dorsal surface with 1 small dorsodistal spines; ventral surface with strong distal spine followed by 2 small spines and several transverse ridges, lateral surface with some short squamiform ridges. Carpus with dorsodistal spine; ventrodistal angle produced into strong spine. Propodus similar to those of second and third pereopods, bearing 9 movable spines on flexor margin; dactylus 0.6 times as long as propodus, with 8 corneous spines and subterminal spinule on flexor margin.
Pereopod 5 merus slightly squamous on outer surface, ventral margin sharply edged.
Uropodal exopod (Fig. 1C) with lateral margin faintly denticulate, armed with few, minute movable spinules; outer surface laterally with short transverse striae each bearing 1 or 2 minute spinules; posterior margin with row of closely spaced spinules. Endopod with lateral margin faintly denticulate; outer surface with several short squamiform ridges sometimes bearing 1 or 2 spinules; posterior margin with row of spinules.
Colouration in life. Body and appendages generally orange-red on dorsal side, rostrum and supraorbital spines darker; corneas brown; fingers of chelipeds darker; longish setae on chelipeds and pereopods 2–4 iridescent; meri of pereopods 2–3 paler; pleomeres 5 and 6, and telson whitish; longish setae on chelipeds and ambulatory legs iridescent (Fig. 3).
Distribution. Presently known only from the type locality on Shoho Seamount, Nishi-Shichito Ridge, at depth of 456.9 m.
Remarks. Gonionida kaimei n. sp. resembles closely G. tangaroa (Ahyong, 2007), known from the Bismarck Sea and Norfolk Ridge, Tasman Sea (Ahyong 2007; Macpherson et al. 2020), sharing the presence of anterior branchial and postcervical spines, a row of spines along the anterior ridge of the pleomere 2 tergite, relatively short chelipeds with a very strong distomesial spine on the merus and proximal and subterminal spines on the margin of the pollex, and the flexor dactylar spine of the walking legs arranged regularly on the flexor margin without distinct hiatus. The new species differs from G. tangaroa in more numerous secondary striae on the pleomere 2 and 3 tergites (Fig. 1A versus Ahyong 2007: fig. 19A, as Munida), less stout article 1 of the with antennular peduncle with more elongate lateral spines (Fig. 1D versus Ahyong 2007: fig. 19B), generally more pronounced spines on the pereopod 1 chela (Fig. 1G versus Ahyong 2007: fig. 19E), more stout dactyli of the pereopods 2–4 (Fig. 2D–G versus Ahyong 2007: fig. F–H), and the living colouration (red-orange overall versus pale, diffuse pink body and red chelipeds; Fig. 3 versus Ahyong 2007: fig. 14E). Gonionida rubrimana (Ahyong, 2007), also known from the Norfolk Ridge, is also similar to M. kaimei n. sp., but the new species is distinguished from G. rubrimana by the unequal distal spines of the article 1 of antennular peduncle (versus subequal in the length) (Fig. 1D versus Ahyong 2017: fig. 18B) and the living colouration (red-orange overall versus pale, diffuse pink body and red chelipeds; Fig. 3 versus Ahyong 2007: fig. 14D).
The K2P genetic divergence of the COI marker between G. kaimei n. sp. and the other congeners ranges from 9.1% to 15.1% (Table 3), indicating that the new taxon is genetically distinct from other congeners available for the analysis, including G. tangaroa and G. rubrimana mentioned above (Macpherson & Machordom 2005).
For information, interspecific genetic divergences of the 16S rRNA gene among 19 species of Gonionida available for analysis are also presented (Table 4). Overall genetic divergences range from 0% to 4.5% (mean 2.0%). Genetic divergence between the new species and other congeneric species ranges from 2.2% to 4.0%.
Etymology. The new species is named after the JAMSTEC’s R/V Kaimei for her contributions to the documentation of the fauna in the Japanese MPA.
description: Published as part of Komai, Tomoyuki, Tsuchida, Shinji & Fujiwara, Yoshihiro, 2023, New record of two species of munidid squat lobster (Decapoda: Anomura) from the North-West Pacific off Japan, pp. 239-254 in Zootaxa 5369 (2) on pages 241-246, DOI: 10.11646/zootaxa.5369.2.4, http://zenodo.org/record/10152389