Sclerocrangon rex Komai & Matsuzaki, 2016, n. sp.
Creators: name: Komai, Tomoyuki
name: Matsuzaki, Koji
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Crangonidae
Sclerocrangon
Sclerocrangon rex

description: Sclerocrangon rex n. sp.
[New Japanese name: Daiou-kijin-ebi] Figs 1–5
Sclerocrangon derjugini.— Zarenkov 1965: 1765, fig. 6. Not Sclerocrangon derjugini Kobjakova, 1936. Sclerocrangon igarashii Komai & Amaoka, 1991: 33 (part).
Sclerocrangon sp.— Fujiya et al. 2013: 18, fig. 2B.
Material examined. Holotype: Nemuro Strait, off Rausu, 700–1000 m, 6 December 2014, gill net, coll. K. Matsuzaki, ovigerous female (cl 41.0 mm), CBM-ZC 13502.
Paratypes: Off Kushiro, Hokkaido, 500–600 m, August 1988, commercial trawler, coll. J. Sasaki, 1 male (cl 30.0 mm), 2 ovigerous females (cl 38.6, 39.0 mm), CBM-ZC 13503; same data as holotype, 3 ovigerous females (cl 39.6, 41.1, 45.5 mm), CBM-ZC 13504.
Description of females. Body (Fig. 1) robustly built; integument firm, surface covered entirely with short pubescence.
Rostrum (Figs 2 A, B; 3A) overreaching distal corneal margins but not reaching distal end of basal article of antennular peduncle, tapered to subacute, upturned tip; lateral margins strongly raised, armed with pair of triangular, acutely pointed teeth, continuous with postorbital carina on carapace; lateral surface with oblique row of moderately long stiff setae; ventral surface bluntly carinate medially, terminating in laterally compressed, triangular tooth directed ventrally and exceeding as far as or slightly beyond upper tip.
Carapace (Figs. 2 A; 3A) sculptured with shallow to deep depressions and longitudinal carinae. Middorsal carina extending over entire length of carapace and anteriorly to posterior half of rostrum, bearing 3 prominent, equidistant teeth each with anterodorsally directed tips; first tooth narrower than other two teeth; dorsal margin of first tooth slightly convex, that of second tooth slightly sinuous, that of third tooth nearly straight. Gastric region shallowly depressed, with pair of bare spots lateral to base of first middorsal tooth and obsolescent oblique carina lateral to base of second middorsal tooth. Postorbital carina blunt, but distinct, reaching to midlength of carapace, with 1 minute tubercle near anterolateral corner and 1 small spine posterior to level of hepatic spine. Branchiocardiac carina short, somewhat oblique in dorsal view, not connected with postorbital carina. Upper branchial carina terminating anteriorly in moderately strong, acuminate hepatic spine, followed by 1 small spine and 1 tiny tubercle or spine. Lower branchial carina blunt, sinuous, extending from tip of branchiostegal tooth to near posterolateral margin of carapace.
Anterolateral margins of carapace bluntly carinate; orbital margin with row of stiff setae partially covering cornea of eye; antennal spine small, slightly ascending in lateral view, accompanied by deep depression inferior to its base. Branchiostegal teeth prominent, directed anterolaterally, lateral margin extending to inferior to base of hepatic tooth as sharp carina; inferior surface deeply depressed; distance between tips of branchiostegal teeth subequal to carapace length. Hepatic groove deep, oblique, interrupting branchiostegal carina and upper branchial carina. Pterygostomial margin with minute spine. Juncture between postorbital ridge and orbital margin with deep cleft; postorbital suture extending along postorbital carina. Ventral margin of carapace sharply carinate.
Thoracic sternum deeply concave; sternites 5 and 6 each with non-acuminate median keel, sternite 7 with minute median tubercle anteriorly, sternite 8 unarmed; sternite 5 with pair of conspicuous tubercles just posterior to coxae of pereopod 3.
Pleon (Figs 2 C, D; 3B, C) sculptured with carinae and depressions or sulci. Pleomeres 1–5 with sharp middorsal carina, pleomere 6 with sharp submedian carinae. Pleomere 1 with crest-like middorsal carina; tergum with shallow transverse sulcus bifurcate laterally and extending onto pleura; lateral surface with 3 protuberances at boundary between tergum and pleuron; anterolateral margin with 1 small spine; pleuron with submarginal carina along anterior to ventral margin, ventral margin armed with 1 small blunt tooth posteriorly. Pleomere 2 with middorsal carina lower than that on pleomere 1; tergum with shallow, broad sulcus bordered by blunt transverse carinae, posterior branch extending onto pleuron as a narrow groove; posterodorsal margin notched medially; lateral surface with 2 low protuberances; pleuron with blunt submarginal carina, armed with 2 small, blunt teeth on ventral margin. Pleomere 3 middorsal carina gently arcuate in lateral view, its posterior end slightly produced; tergum posteriorly with blunt submarginal carina extending onto pleuron; lateral surface with low, faintly bilobed elevation; pleuron armed with 2 subacute teeth on ventral margin. Pleomere 4 with middorsal carina produced posteriorly as moderately strong tooth; tergum posteriorly with obsolescent transverse submarginal carina terminating at posterolateral notch marking boundary between tergum and pleuron; lateral surface with faintly branched obsolescent ridge; pleural surface entirely shallowly depressed, with blunt submarginal carina, ventral margin with 2 subacute teeth. Pleomere 5 with middorsal carina gently arcuate in lateral view, produced posteriorly into strong tooth; tergum anteriorly with distinct transverse groove, posterodorsal margins sinuous in either side of posteromedial tooth, with small blunt lobe at just superior to posterolateral notch; lateral surface with blunt bifurcate carina; pleural surface shallowly concave, with submarginal carina along ventral margin, margin with acute posteroventral and anteroventral teeth. Pleomere 6 about 1.1 times as long as pleomere 5 and 1.7 times as long as wide; submedian carinae with slightly sinuous dorsal margins, each terminating posteriorly in small spine exceeding beyond posterodorsal margin; lateral surface with blunt carina extending from base, curving downward, not reaching to posterolateral margin; ventrolateral margins somewhat elevated, diverging posteriorly, with acute tooth at posteroventral angle; posterolateral process strong, supported by blunt elevation, terminating in strong tooth.
Pleonal sternites 1–5 each with small median tubercle; sternite 6 shallowly depressed, with small preanal spine.
Telson (Figs 2 D; 3C) 1.4 times as long as pleomere 6, gradually tapering posteriorly to blunt to acute apex; dorsal surface deeply grooved medially, dorsolateral carinae highly elevated, with 2 pairs of small spiniform setae; apex flanked by 1 pair of minute spiniform setae.
Cornea (Figs 2 A, B; 3A) well developed, hemispherical, contiguous, darkly pigmented, its maximal width 0.15–0.17 of carapace length; eyestalk with blunt dorsodistal tubercle with covering of short setae.
Antennular peduncle (Figs 2 A, B; 3A) slightly overreaching midlength of antennal scale, every article covered with short pubescence. Article 1 slightly longer than distal 2 articles combined, with blunt dorsodistal angle; ventromesial ridge with tiny tubercles proximal to midlength; stylocerite broad, with acute distal spine and angular proximolateral margin. Article 2 approximately as long as wide. Article 3 with small dorsodistal lobe. Outer flagellum overreaching distal margin of scaphocerite composed of 25–30 articles, male flagellum of 35 articles. Inner flagellum setose, slightly longer than outer flagellum.
Antenna (Figs 2 A, B; 3A) with very stout basicerite (article 2) bearing strong distolateral spine directed anterolaterally and small dorsodistal lobe; dorsal surface with shallow oblique groove. Scaphocerite (antennal scale) oblong, approximately half length of carapace, 1.7–1.8 times as long as wide, surfaces covered with dense short pubescence; dorsal surface with 3 longitudinal carinae; lateral margin faintly convex; distolateral tooth small, supported by lateral-most carina, not reaching broadly rounded distal lamella. Carpocerite (article 5) subcylindrical, somewhat flattened dorsoventrally, slightly curved laterally, falling far short of distal margin of lamella. Flagellum damaged in all available specimens, but preserved proximal part not so flexible, poorly setose. Mouthparts (dissected from one of paratypes) as illustrated (Fig. 4 A–F), typical of genus.
Maxilliped 3 (Fig. 5 A, B) overreaching distal margin of scaphocerite by half or more length of ultimate segment. Articles of endopod each with covering of short pubescence. Antepenultimate article (basis-ischium-merus fused article) sinuous, somewhat flattened dorsoventrally, bearing 1 slender spiniform seta adjacent to ventromesial distal angle and 1 recurved, minute spiniform seta adjacent to ventrodistal margin; proximomesial margin slightly expanded. Penultimate article (= carpus) subrectangular, flattened dorsoventrally, about 2.5 times as long as wide; mesial face with numerous long stiff setae, composing grooming apparatus. Ultimate segment spatulate with both lateral and mesial margins gently convex, 4.0 times as long as wide, tapering, terminally with short spiniform seta; lateral and mesial margins thick long stiff setae, mesial margin also with several cluster of long spiniform setae. Exopod (not illustrated) tapering, reaching midlength of antepenultimate segment; flagellum bent at base.
Pereopod 1 (Fig. 5 C, D) stout, reaching distal margin of scaphocerite; each article with short pubescence. Coxa laterally with prominent articular condyle to basis. Basis with deep foramen on mesial face proximally. Merus slightly broadened distally, with small dorsodistal spine; ventral surface with shallow longitudinal sulcus, unarmed. Carpus short, cup-like, armed with small distolateral and moderately large ventrolateral distal spines; ventromesial distal angle with cluster of stout spiniform setae, forming part of grooming apparatus. Palm stout, slightly widened distally, about 2.6 times as long as wide at midlength, proximal part subcylindrical, distomesial part strongly flattened; occlusal margin nearly transverse, slightly convex, bordered by chitinous plate; thumb narrowly triangular, flattened, acuminate. Dactylus tapering to acute tip, tip not overreaching base of thumb when closed.
Pereopod 2 (Fig. 5 E) slender, chelate, carried flexed, overreaching distal margin of antennal scale by half length of chela. Coxal with long process extending into branchial chamber (not figured). Merus longer than ischium. Chela (Fig. 5 F) about half length of carpus. Dactylus 0.4–0.5 times as long as palm; occlusal margins of fingers pectinated with minute spiniform setae (Fig. 5 G).
Pereopod 3 (Fig. 5 H) slender, overreaching antennal scaphocerite by length of dactylus; coxa to merus with covering of short pubescence, pubescence on carpus fading in distal half, propodus and dactylus glabrous. Coxa with prominent tuft of stiff setae on posteromesial angle (not illustrated). Merus slightly longer than ischium. Carpus distinctly longer than merus, 2.8 times as long as propodus. Dactylus about 0.3 times as long as propodus, terminating in hood-like process accommodating tuft of minute setae (not illustrated).
Pereopod 4 (Fig. 5 I) stout, falling slightly short of distal margin of scaphocerite, articles with covering of pubescent except for dactylus. Coxa with prominent condyle laterally at articulation with basis. Basis and ischium short. Merus subcylindrical, slightly widened distally, with longish setae on dorsal and ventrolateral margins. Carpus also subcylindrical, with row of longish setae on ventrolateral margin. Propodus narrowing distally, about 1.8 times as long as carpus. Dactylus (Fig. 5 J) flattened dorsoventrally, spatulate, about half length of propodus; lateral and mesial margins sharply edged, ventral and dorsal surfaces bluntly carinate medially; dorsal surface with submarginal row of pores along lateral and mesial margins (these pores possibly representing setal pockets, but setae absent or at most obsolescent); apex with minute conical unguis clearly basally demarcated and horizontally flanked by acute projections from corpus (Fig. 5 K).
Pereopod 5 (Fig. 5 L) generally similar to pereopod 4, reaching midlength of scaphocerite.
Branchiae including pleurobranchs on thoracomeres 4–8; no arthrobranch or podobranch.
Pleopods devoid of appendices internae.
Uropod with protopod bearing small posterolateral spine and short crested ridge on outer surface mesially; articulating condyle well developed, with small tubercle. Both exopod and endopod slightly overreaching apex of telson. Exopod with sinuous lateral margin, terminating in small triangular, acute tooth; no spiniform seta just mesial to posterolateral tooth; dorsal surface with 2 longitudinal carinae lateral to midline; diaeresis extending from base of posterolateral tooth toward mesial, but fading away mesial to midline. Exopod with middorsal carina and rounded depression proximomesially, bordered by proximal part of middorsal carina and branched transverse carina.
Eggs large, almost spherical, diameter 4.0– 4.1 mm.
Description of male. Body more slender than in females; spines or teeth on carapace and pleon more acuminate than in females (Fig. 6 A–C). Thoracic sternites 5–8 each with laterally compressed, acuminate median teeth decreasing in size posteriorly; sternite 5 with pair of tubercle posteriorly. Middorsal carina on pleomeres 1–5 higher, more strongly crested than in females. Outer antennular flagellum longer and broader, composed of about 35 articles. Pereopods 4 and 5 more slender than in females. Pleopod 1 (Fig. 4 G, H) with endopod about one-third length of exopod, narrowing in proximal half, distal half elongate suboval-shaped, margins with numerous long stiff setae Pleopod 2 (Fig. 4 I, J) with appendix masculina elongate, tapering to rounded apex, margins with numerous long spiniform setae, dorsal surface covered with numerous short stiff setae; endopod reduced to thick, rounded lobe fused to base of appendix masculina.
Colouration in life. Body and appendages generally brown, whitish along ventral margins of carapace and pleomeres 1–4; dorsal faces of meri to propodi of pereopods 4 and 5 whitish, ventral faces reddish brown (Fig. 1 A, B).
Distribution. Presently known only from off Kushiro and Nemuro Strait, eastern Hokkaido, at depths of 500–1000 m.
Remarks. Sclerocrangon was originally established for Cancer boreas Phipps, 1774 (type species) by Sars (1883), although no proper generic diagnosis or description was given. Later, Sars (1885) published a generic diagnosis of his new genus and a detailed description of Sclerocrangon ferox (Sars, 1877) under an incorrectly identified name S. salebrosus (Owen, 1839). Since then, several crangonid species had been described in or assigned to Sclerocrangon (e.g., Faxon 1893; Rathbun 1902, 1904; Brashnikov 1907; Yokoya 1933; Kobjakova 1936, 1937, 1955; Birstein & Vinogradov 1951, 1953; Yaldwyn 1960). Zarenkov (1965) reviewed 58 species assigned to Crangon Fabricius, 1798 and Sclerocrangon, restricting the following six species to Sclerocrangon: S. atrox Faxon, 1893 (eastern Pacific, off Baja California Peninsula to northern Peru, at depths of 800–1586 m: Hendrickx 2015), S. boreas (Arctic to northern North Pacific, subtidal to 400 m: d’Udekem d’Acoz 1999; Komai & Komatsu 2009), S. derjugini Kobjakova, 1936 (possibly endemic to the Sea of Okhotsk, at depths of 182–1000 m: Komai & Amaoka 1989; this study), S. ferox (Arctic to northern North Atlantic, at depths of 90–1000 m: Squires 1990; d’Udekem d’Acoz 1999), S. salebrosa (Owen, 1839) (northern North Pacific, Bering Sea to Sea of Japan, at depths of 10–250 m; Kim & Komai 2002) and S. zenkevitchii Birstein & Vinogradov, 1953 (Bering Sea to off the Pacific side of northern Japan, at depths of 2986–4070 m: Komai & Komatsu 2009). Since then, two new species have been described from the western part of the North Pacific, i.e., S. unidentata Komai & Takeda, 1989 (off Iwate Prefecture to Suruga Bay, Japan: Komai & Takeda 1989; Komai 2011) and S. igarashii Komai & Amaoka, 1991 (South Kuril Islands to off Kushiro, Hokkaido: Komai & Amaoka 1991). Kim & Komai (2002) clarified that Sclerocrangon gasuyebi Yokoya, 1933 was a junior subjective synonym of S. salebrosa. At present, eight species are known in Sclerocrangon, of which six species occur in Japanese waters (Hayashi 2016). The genus is characterized by the moderately to strongly sculptured body integument, the lack of submedian gastric spines on the carapace, the presence of at least one tooth on the pleural margin of each pleomere and the greatly reduced endopod of the male second pleopod which is fused with an enlarged appendix masculina. In particular, the character of the male second pleopod is autapomorphic to Sclerocrangon (Christoffersen 1988), supporting the monophyly of the genus.
The new species is close to Sclerocrangon derjugini and S. igarashii, both occurring in waters off eastern Hokkaido (Komai & Amaoka 1989, 1991), in the general armature and sculpture on the carapace and pleon. In particular, the rostrum with a pair of lateral teeth and a prominent, ventrally directed midventral tooth is diagnostic (cf. Komai & Amaoka 1991). Differentiating characters among the three species are summarized in Table 1. The new species is readily distinguished from its two relatives by the possession of a small extra spine on the postorbital carina, located slightly posterior to the level of the hepatic spine. Such an extra spine is absent in S. derjugini and S. igarashii, as well as the other congeneric species. Sclerocrangon derjugini differs from S. rex n. sp. and S. igarashii in the absence of an orbital spine or tubercle, the absence of a second spine on the branchial carina, the spiniform dorsodistal tubercle of the eyestalk, relatively slender pereopods 4 and 5 with dactyli having submarginal row of numerous short stiff setae along margins (cf. Komai & Amaoka 1989). In S. rex n. sp. and S. igarashii (cf. Komai & Amaoka 1991), there is a tubercle (S. rex n. sp.) or spine (S. igarashii) on the orbital margin; the branchial carina bears a second spine in addition to a terminal spine; the dorsodistal tubercle on the eyestalk is blunt or subacute, never spiniform; the dactyli of pereopods 4 and 5 each has a submarginal row of pores, but setae are absent or obsolescent. Furthermore, the posterodorsal spine of pleomere 5 is acute in S. rex n. sp. and S. derjugini, but it is more strongly produced in S. derjugini than in S. rex n. sp. In S. igarashii, this spine is blunt or subacute (Komai & Amaoka 1991, fig. 1). Sclerocrangon igarashii has enlarged middorsal teeth on the carapace and middorsal carina on pleomere 1–5. In particular, the second middorsal tooth on the carapace is highly crested with a strongly convex dorsal margin and a blunt or subacute apex in S. igarashii. In S. rex n. sp. and S. derjugini, this tooth is acuminate with a nearly straight or slightly convex dorsal margin. Finally, S. rex n. sp. is perhaps the largest in the family, attaining 45.5 mm in cl.
The geographical ranges of these three species seem to be different, though those of S. rex n. sp. and S. igarashii partially overlap. Presently, S. rex n. sp. is known off Kushiro and Nemuro Strait, eastern Hokkaido. Sclerocrangon derjugini is restricted to the Sea of Okhotsk. Sclerocrangon igarashii occurs in the South Kuril Islands to off Kushiro.
Zarenkov (1965) published a figure he attributed to Sclerocrangon derjugini (Fig. 6, showing carapace in dorsal view, pleomere 6 in dorsal view and endopod of the male pleopod 2), although he did not provide detailed information on his material. The figure of the carapace clearly shows a small extra spine on the postorbital carina located slightly posterior to the level of the hepatic spine, which is characteristic for S. rex n. sp. Consequently, Zarenkov’s (1965) figure of S. derjugini is here referred to the new species. Komai & Amaoka (1991) believed that Zarenkov (1965) had actually examined S. igarashii, instead of S. derjugini, but their interpretation is corrected herein. Fujiya et al. (2013) reported on an unidentified species of Sclerocrangon on the basis of material from off Rausu, Nemuro Strait, very close to the type locality of the new species. The authors clearly mentioned the presence of an extra spine on the carapace on their specimens, though they incorrectly called it a hepatic spine. Although Fujiya et al. (2013) specimens were not available for examination, there is little doubt that they actually represent S. rex n. sp.
Etymology. The Latin specific name “ rex ” (= king) refers to the fact that the new species is the largest among the family Crangonidae.
Restricted synonymy (for full synonymy, see Baba et al. 2008: 168).
Munidopsis verrilli Benedict, 1902: 291, fig. 34 (type locality: off South California, 1500–1800 m).— Schmitt 1921: 169,
fig. 108.— Wicksten 1982: 245.— Baba & Poore 2002: 245, fig. 10.— Baba 2005: 194, 298.— Osawa & Takeda 2007:
142, fig. 6C, D.— Baba et al. 2008: 168.— Baba et al. 2009: 275, figs 252, 253.— Dong & Li 2015: 94, figs 3, 6, 8 C. Material examined. Nemuro Strait, off Rausu, Shiretoko Peninsula, Hokkaido, 700–1200 m, December 2015, commercial gill net for Sebastrolobus macrochir, coll. K. Matsuzaki, 1 male (cl 23.5 mm), CBM-ZC 13505; RV “ Tansei-maru ”, KT02-3 cruise, stn E-1, Okinawa Trough, 26°11.34’N, 124°54.27’E to 26°12.65’N, 124°55.47’E, 991 – 955 m, beam trawl, 21 April 2002, 1 female (cl 20.3 mm), NSMT-Cr 17851.
Coloration in life. Body and appendages entirely white; corneas opaque.
Distribution. Recorded from both East and West Pacific. East Pacific: off Oregon, San Nicolas Island, Santa Cruz Basin, from Monterey Bay to off Cerros Island, and off San Diego; West Pacific: Indonesia (Makassar Strait), Tasmania, South China Sea, Taiwan, and Japan (Okinawa Trough and Sea of Okhotsk side of Hokkaido); 732–4169 m.
Remarks. The present specimen from Hokkaido agrees well with previous taxonomic accounts of Munidopsis verrilli from various localities (Benedict 1902; Schmitt 1921; Baba & Poore 2002; Baba 2005; Osawa & Takeda 2007; Baba et al. 2009). Diagnostic features for species recognition include: carapace surface with sparse setae arranged in tufts or short transverse rows (Figs 7; 8A, B); carapace spines including one pair of epigastric, one pair of postocular, one pair of anterolateral and four pairs of lateral branchial (Fig. 8 A, B); ocular peduncle with anterior and lateral spines, cornea well exposed, clearly visible in dorsal view (Fig. 8 B); chelipeds long, far exceeding beyond anteriorly stretched pereopods 2–4 (Fig. 7).
We compared our Hokkaido specimen with the specimen from the Okinawa Trough reported by Osawa & Takeda (2007), and confirmed that they are indeed very similar to each other. In the Hokkaido specimen, the armature of the dorsomesial margin of the cheliped palm is weak, unarmed on the right and armed with one spine and one protuberance, instead of two spines on both sides in the specimen from Okinawa Trough. This minor difference is likely intraspecific variation.
Dong & Li (2015) identified a specimen from a cold seep off Guandong Province in the South China Sea with M. verrilli, with notes on some minor morphological differences from the previous accounts of the species. Our examination of the specimen from Hokkaido confirms the observation of Dong & Li (2015), suggesting a necessity of reappraisal of the specific identity of the specimen from the South China Sea.
The squat lobster fauna from the high latitudinal area in the northwestern Pacific is very poor (Makarov 1938, 1962; Vinogradov 1950; Komai et al. 1992). With regard to Munidopsidae, Munidopsis antonii (Filhol, 1884) has been recorded from the Sea of Okhotsk at a depth of 3500 m (Makarov 1938, 1962; as Munidopsis beringana Benedict, 1902); and Munidopsis petalorhyncha Baba, 2005 was originally described from the Kuril Trench at depths of 5035–5210 m (as M. subsquamsosa latimana Birstein & Zarenkov, 1970). The present specimen represents the first discovery of the family from waters off northern Japan.
description: Published as part of Komai, Tomoyuki & Matsuzaki, Koji, 2016, Two deep-sea decapod crustaceans collected off eastern Hokkaido, Japan: Sclerocrangon rex n. sp. (Caridea: Crangonidae) and Munidopsis verrilli Benedict, 1902 (Anomura: Munidopsidae), pp. 92-106 in Zootaxa 4162 (1) on pages 92-106, DOI: 10.11646/zootaxa.4162.1.4, http://zenodo.org/record/265869