Lysirude goekei, Takeda & Ohtsuchi & Komatsu, 2021

Takeda, Masatsune, Ohtsuchi, Naoya & Komatsu, Hironori, 2021, Crabs (Crustacea, Decapoda) from the Sea off East and Southeast Asia collected by the RV Hakuhō Maru (KH- 72 - 1 Cruise) 1. Sulu Sea and Sibutu Passage, Bulletin of the National Museum of Nature and Science. Series A, Zoology 47 (2), pp. 65-97 : 77-80

Lysirude goekei sp. nov.

( Figs. 9–10 )

Lyreidus channeri : Griffin, 1970, p. 107, figs. 6d, i, r, 7f, 8e, pl. 2 fig. B. [Not Lyreidus channeri Wood-Mason, 1885 ]

Lysirude channeri : Goeke, 1985 [1986], p. 215, fig. 6: Feldman, 1992, fig. 10: Tucker, 1998, fig. 1 (3–4); Ng et al., 2008, p. 42 (in list), fig. 17: Guinot et al., 2013, p. 289, fig. 40C–D. [Not Lysirude channeri (Wood-Mason, 1885) ]

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 13 (Sulu Sea , 08°20.8′N, 118°19.8′E – 08°20.6′N, 118°18.8′E; 730–738 m deep); 3 m beam trawl; 27 May, 1972; ˁholotype, NSMT-Cr 28969 .

Measurements. CB 16.6 mm excluding carapace anterolateral spines; CL 26.4 mm excluding rostrum; length of rostrum, 4.1 mm; length of eyestalk, 2.3 mm.

Diagnosis. Carapace pyriform, smooth, convex dorsally sideways; rostrum, external orbital spines and anterolateral spines of carapace elongate. Pleomeres 3–4 each with medial spine. Cheliped merus with proximal spine; carpus with distal spine; palm without tooth on upper margin, with 3 triangular teeth on lower margin, proximal tooth rudimental. Carpus of first ambulatory leg with subdistal tooth on upper margin. Propodus of third ambulatory leg strongly lobate on inner margin; dactylus paddle-shaped. Fourth ambulatory leg reduced. G1 with trilobate apex.

Description of holotype (Male). Carapace ( Fig. 9A ) narrowly pyriform, 1.59 times as long as broad, dorsally convex transversely, widest at anterolateral corner; anterolateral margin divergent toward anterolateral spine, with median inconspicuous hump, covered with minute granules; lateral margins of both sides subparallel in anterior half, convergent in posterior third, beaded with small granules in posterior half of lateral margin and posterior margin; posterior margin wider than frontal neck; dorsal surface seemingly smooth, but entirely covered with microscopic pits, with pair of shallow subparallel furrows along center of carapace. Rostrum ( Figs. 9 , 10A ) elongate, triangular, ca. 1.7 times as long as broad, ca. 1.8 times as long as eyestalk. Supraorbital margin ( Figs. 9–10A ) U-shaped, provided with a very short, obliquely-outward directed furrow at base of external orbital spine; external orbital spine elongated, slightly longer than rostrum, ca. 2.0 times as long as eyestalk, slightly directed outward. Eyestalk ( Fig. 10A ) short, lanceolate, movable, with small, pyriform, pigmented cornea on lateral side of apex.

Pleon ( Fig. 9A–B ) with free 6 slender pleomeres and small triangular telson; first 3 pleomeres visible in dorsal view; surfaces of all pleomeres and telson smooth, longitudinally convex along median line, furnished with short setae along lateral margins; pleomeres 3–4 each with porximally recurved, medial spine.

Third maxilliped ( Fig. 9B ) elongate, narrow, with oblongly quadrate ischium and merus; ischium with transverse suture on mesial half of proximal 0.2; exopod reaching beyond ischium.

Cheliped segments ( Fig. 9 ) subcylindrical to compressed; merus with short spine on proximal 0.3 of dorsal surface; carpus with strong spine on distal part of dorsal surface; palm ( Fig. 10B ) compressed, crested on upper margin, with 3 triangular teeth on lower margin, teeth becoming larger distally, proximal tooth rudimentry; upper margin of movable finger crested, cutting edge weak, without teeth; fixed finger broad, compressed, cutting edge irregularly crenulate.

Ambulatory legs ( Fig. 9 ) different in shape from each other. First leg rather compressed; merus with a median line of scattered granules and very short setae on lower surface; carpus crested on upper margin with distal denticle; propodus broadened, crested on both margins; dactylus lanceolate. Second leg longest, subcylindrical, weakly crested on both margins of propodus, with lanceolate dactylus. Third leg short, rather compressed; ischium with a small distal tooth; propodus ( Fig. 10C ) short, crested on outer margin, with strongly expanded, ovate lobe on inner margin, lobe entirely fringed with long setae; dactylus foliaceous, paddle-shaped, entirely fringed with long setae along expanded inner margin. Fourth leg reduced, fringed with short setae on propodus and dactylus.

G1 ( Fig. 10D–E ) stout, trilobate at apex; distolateral lobe of apex rounded, with aperture; mesial lobe tongue-shaped; medial lobe small, triangular. G2 ( Fig. 10F ) stout, slightly shorter than G1, acuminate at tip,

Etymology. Named after Dr. Gary D. Goeke for his great contributions to the taxonomy on raninid crabs.

Remarks. Currently, the genus Lysirude comprises three recent species, viz., L. nitidus (A. Milne-Edwards, 1880) from the western Atlantic, L. channeri (Wood-Mason, 1885) (with L. gracilis Wood-Mason, 1888 as a synonym) from the Indo-West Pacific and L. griffini Goeke, 1985 from the Philippines. However, the recent redescription of L. channeri on the basis of the holotype and recently collected specimens from the Bay of Bengal by Rozario et al. (2017) and the present study reveal that the records of L. channeri from the West Pacific are due to mis- identification, representing a new species distinct from the Indian Ocean form. In this paper we described L. goekei sp. nov. based on the Sulu Sea specimen, with photographs and line drawings. The records of L. channeri listed in the above synonymy list (p. 77) are referrable to the new species.

Lysirude goekei is readily distinguished from L. channeri by the following features: 1) the rostrum and external orbital spine are elongate and ca. 1.7 and 2.0 times as long as the eyestalk, respectively (vs. slightly longer than the eyestalk in L. channeri ); 2) the marginal spine between the external orbital spine and the anterolateral spine of the carapace is represented by a low swelling (vs. strong in L. channeri ); 3) the upper margin of the cheliped palm has no tooth (vs. with a subterminal tooth in L. channeri ); 4) proximal-most tooth of the lower margin of the cheliped palm is rudimentary, tubercle-like (vs. distinct and triangular in L. channeri ). The pigmentation of cornea may also differentiate both species (unpigmented in L. channeri ).

Griffin (1970) considered that the lack of the intercalated spine of the carapace in the specimen from the South China Sea may be due to breakage during life, but the lack of this spine is constant as observed among the specimens from the Philippines ( Goeke, 1985 [1986]; Feldman, 1992; Tucker, 1998; Ng et al., 2008; Guinot et al., 2013; this study). Goeke (1985 [1986]: fig. 6B) showed a variation in the presence of the intercalated spine on the carapace in the Philippine juvenile specimen, and also mentioned that the presence of the intercalated spine is also rarely seen among juveniles in the Atlantic species, L. nitidus .

Distribution. South China Sea and Philippines, 366–820 m deep.

Figures

Fig. 9. Lysirude goekei sp. nov., male, holotype (NSMT-Cr 28969. CB 16.6mm; CL 26.8mm including rostrum). Dorsal (A) and ventral (B) views.

Fig. 10. Lysirude goekei sp. nov., male, holotype (NSMT-Cr 28969. CB 16.6mm; CL 26.8mm including rostrum). Orbital region in dorsal view (A), left chela in outer view (B), propodus and dactylus of left third ambulatory leg (C), left G1 in mesial view (D), apex of the same enlarged (E), left G2 in mesial view (F). Scale bar: 2mm for A–C, 1mm for D, F, and 0.25mm for E.