Ctenocheles sinicus, Kou & Poore & Li, 2024

Kou, Qi, Poore, Gary C. B. & Li, Xinzheng, 2024, A new species of Ctenocheles Kishinouye, 1926 (Decapoda, Axiidea, Ctenochelidae) from China, Zootaxa 5529 (2), pp. 381-395 : 383-386

Ctenocheles sinicus sp.nov.

( Figs. 1–7 )

http://zoobank.org/ urn:lsid:zoobank.org:act:7F284D42-FDBD-4962-8B6B-8400FAFCB063

Type material. Holotype: Male (cl 8.1 mm, tl 39.5 mm), Taiwan Strait, off southeast coast of Nanri Island , Fujian, southwestern continental shelf of East China Sea , Northwest Pacific , 25°6'11"N, 119°33'27"E, 50 m depth, fishing vessel, bottom trawl, 28 November 2023, MBM 304652 .

Paratypes: Female (cl 9.9 mm, tl 51.2 mm), same collecting location as holotype, 16 November 2023, MBM 304653 ; male (cl 7.7 mm, tl 39.0 mm), same collecting location as holotype, 12 December 2023, MBM 304654 .

Etymology. The species name alludes to locality of origin, China.

Diagnosis. Rostrum unarmed dorsally, reaching proximal one-third of eyestalks. Carapace with suborbital angle rounded. Maxillipeds 2 and 3 each with short exopod. Pereopod 1 merus and ischium smooth on lower margin. Major cheliped with fingers twice as long as palm. Pereopod 2 ischium with prominent spiniform setae along lower margin. Male pleopod 1 unsegmented, tapering. Uropodal exopod with distal margin divided by notch, anterodistal angle rounded.

Description of male holotype. Body slender, weakly calcified. Pleon and telson together 3.5 times as long as carapace.

Rostrum triangular in dorsal view, apex acute, reaching proximal one-third of eyestalks, unarmed, median rostral carina extending posteriorly to mid-length of carapace. Carapace smooth, sparsely setose, anterolateral angle obtusely rounded; gastric region flat, with low prominence at anterior quarter of carapace; cardiac region slightly more elevated than gastric region, with pronounced trapezoidal prominence; cervical groove well-defined, reaching three-quarters length of carapace; postcervical carina distinct, extending to posterior end of carapace; linea thalassinica complete; anterior branchiostegal margin deeply notched, fringed with long setae; branchiostegite with hepatic boss, posterior region inflated, defined by arcuate groove; pterygostomial angle prominently produced.

Thoracic sternite 6 narrow; sternite 7 broad, shield-shaped, central region concave, posterior half with distinct groove in midline, anterolateral angles blunt.

Pleonites smooth, unarmed; pleonite 1 tergite with deep grooves on lateral surfaces; pleonite 2 as long as pleonite 1, pleuron with incomplete lateral suture, posteroventral angle rounded; pleonite 3 slightly longer than pleonites 4 and 5, 0.8 times as long as pleonite 2, pleura 3–5 with incomplete sutures laterally, ventral margin and posteroventral angle slightly produced, lateral and dorsal surfaces with patches of long plumose setae; pleonite 6 as long as pleonite 2, arcuate in dorsal view, pleuron ventrally rounded, with rounded posterolateral projection.

Eyestalks contiguous, flat, subrectangular, twice as long as wide, anterior margin oblique, with obtuse anteromesial tip, reaching distal two-thirds of antennular basal article; cornea depressed, weakly pigmented.

Antennular peduncle reaching almost distal margin of antennal article 4; article 1 widest, with statocyst; article 2 as long as article 1, 2.3 times as long as wide; article 3 0.7 times as long as article 2, 2.1 times as long as wide; dorsal and ventral flagella subequal in length, longer than peduncle. Antennal peduncle article 1 unarmed, with lateral antennal gland; article 2 with 1 blunt ventrolateral tooth, left side with 1 tiny distolateral spine; scaphocerite subacute, almost reaching end of article 3 in lateral view; article 3 2.2 times as long as wide; article 4 2.1 times as long as of article 3, 5.4 times as long as wide; article 5 0.4 times as long as of article 4; flagellum longer than antennular flagella.

Mandible with 3-segmented palp, article 3 spatulate, fringed with setae; incisor process bearing essentially 4 teeth on cutting margin; molar process very short, partly fused with incisor, with 4 (left) or 5 (right) blunt processes. Maxillule with 2-segmented endopod, article 1 longer than article 2; article 2 curved distally, sparsely setose; basal endite with row of spiniform setae along distal margin; coxal endite not particularly enlarged, rounded distally, with row of robust setae along distal margin. Maxilla with endopod tapering; basal and coxal endites each deeply subdivided, setose on distal margins; scaphognathite anterior lobe reaching three-quarters of endopod, posterior lobe without long seta.

Maxilliped 1 with small, tapering endopod, curved distomesially; endite well-developed, densely setose mesially; exopod broad, overreaching basal endite by half length, setose distally; epipod bilobed, ear-shaped, with posterior lobe elongate.

Maxilliped 2 ischiomerus 3.2 times as long as wide, slightly curved, flexor margin with row of long setae; carpus short, cup-shaped; propodus subrectangular, 2.0 times as long as wide, about half as long as ischiomerus; dactylus short, subsemicircular, 0.3 times as long as propodus, tip with stout serrate setae; exopod short, unsegmented, reaching midlength of ischiomerus, tip with long plumose seta; epipod lanceolate.

Maxilliped 3 ischium 2.8 times as long as wide, crista dentata of 15 small teeth; merus 0.8 times as long as ischium, armed with 1 subdistal spine on mesial margin; carpus unarmed, as long as merus; propodus unarmed, 2.4 times as long as wide, 0.9 times as long as carpus; dactylus suboval, 3.1 times as long as wide; exopod unsegmented, reaching distal 0.7 length of ischium.

Chelipeds unequal and dissimilar. Major (right) cheliped, ischium compressed laterally, 4.0 times as long as greatest width at distal end, lower margin unarmed; merus 1.1 times as long as ischium, 3.0 times as long as wide, upper margin arcuate, lower margin straight, smooth; carpus short, cup-shaped, unarmed; propodal palm slightly swollen, smooth, 0.8 times as long as merus, 1.3 times as long as greatest width, with oval concavity on distodorsal margin; fixed finger and dactylus 2.1 times as long as upper margin of propodus, distally curved mesially, outer margins unarmed, opposable margins armed with about 40 irregular long and short narrow spines. Minor (left) cheliped, 0.6 times as long as major cheliped; ischium and merus compressed laterally, subequal in length, unarmed; carpus 0.4 times as long as merus, unarmed; propodal palm 0.9 times as long as merus, 3.0 times as long as wide, unarmed; fixed finger and dactylus 1.6 times as long as upper margin of propodus, distally slightly curved mesially, outer margins unarmed, opposable margins armed with about 25 weak teeth.

Pereopod 2 ischium 0.7 times as long as wide, with 13 (left) or 12 (right) prominent spiniform setae along lower margin; merus 3.2 times as long as wide, upper margin unarmed, lower margin with 5 (left) or 6 (right) prominent spiniform setae proximolaterally; carpus 0.5 times as long as merus, cup-shaped, unarmed; chela subrectangular, propodal palm unarmed, 0.4 times as long as carpus, 0.5 times as long as wide; fingers 2.3 times as long as upper margin of propodus, terminating in corneous unguis, opposable margins smooth.

Pereopod 3 ischium 1.2 times as long as wide, unarmed; merus 3.1 times as long as greatest width, upper margin slightly arcuate in distal half, unarmed, lower margin with 5 slender spiniform setae; carpus 0.7 times as long as merus, unarmed, widening distally; propodus 0.8 times as long as carpus, lateral surface with numerous spiniform setae on lower margin; dactylus stout, 0.6 times as long as propodus, curved ventrally, terminating in corneous unguis.

Pereopod 4 ischium 2.0 times as long as wide, unarmed; merus 3.8 times as long as greatest width, unarmed; carpus 0.8 times as long as merus, unarmed; propodus 0.7 times as long as carpus, lateral surface with numerous spiniform setae on lower margin, distal lower-mesial surface densely setose; dactylus stout, 0.6 times as long as propodus, curved ventrally, lateral surface with several spiniform setae, terminating in corneous unguis.

Pereopod 5 coxa with gonopore; ischium 1.8 times as long as wide, unarmed; merus 5.0 times as long as wide, unarmed; carpus 0.7 times as long as merus, upper margin arcuate in distal half, unarmed; propodus 0.9 times as long as carpus, distoventral margin protruding below dactylus, distal lower-lateral surface densely setose; dactylus twisted, curved ventrally, terminating in corneous unguis.

Pleopod 1 uniramous, unsegmented, rod-like, distally constricted, 4.0 times as long as greatest width, with 8 long mesial marginal setae. Pleopod 2 biramous; endopod longer and broader than exopod, 2.8 times as long as greatest width; appendix masculina spatulate, 1.8 times as long as appendix interna, exceeding apex of endopod, anterior surface with 2 rows of long terminal seta; appendix interna rod-like, 0.2 times as long as endopod, tip slightly curved, bearing cluster of small hooks; exopod 4.2 times as long as greatest width. Pleopods 3–5 similar, biramous, endopod longer and broader than exopod; with linear appendix interna, 0.15 times as long as endopod.

Uropod almost as long as telson, marginally densely setose; peduncle stout, posterior margin protruding, armed with curved tooth above endopod; endopod oval, 1.5 times as long as wide, dorsal surface with 2 longitudinal rounded carinae, one along anterior margin and one median, distal margin with 5 (left) and 7 (right) spiniform setae; exopod 1.1 times as long as greatest width, longer and broader than endopod, anterodistal angle rounded, dorsal surface with 3 longitudinal rounded carinae, one along anterior margin and two submedian, distal margin separated by shallow notch, with 24/15 (left) and 23/16 (right) spiniform setae increasing is size near posterior angle.

Telson subrectangular, 0.9 times as long as wide, lateral margin constricted at anterior 0.4 length, unarmed, dorsal surface with pairs of submedian carinae and oblique lateral carinae, posterior margin truncate, middle slightly concave, each side with 5 slender spiniform setae.

Branchial formula as follows.

Female paratype. Generally similar to male, body stouter. Pleopod 1 uniramous, unsegmented, rod-like, 10 times as long as wide, without marginal seta. Pleopod 2 biramous; endopod longer and broader than exopod, 3.0 times as long as greatest width, with shallow, transverse suture along proximal one-third; appendix interna rod-like, 0.2 times as long as endopod, tip slightly curved, bearing cluster of small hooks; exopod 4.8 times as long as greatest width.

Colour in life. Body and pereopods generally yellowish; gastric region and cheliped fingers pink; ovary orange; cornea blackish ( Fig. 1 ).

Distribution. Known only from the type locality: Taiwan Strait, the East China Sea, Northwest Pacific, 50 m depth.

Figures

FIGURE 1. Ctenocheles sinicus sp. nov., paratype female, cl 9.9 mm, tl 51.2 mm, colour in life, MBM 304653: A, left lateral view, B, right lateral view; C, dorsal view.

FIGURE 2. Ctenocheles sinicus sp. nov., holotype male, cl 8.1 mm, tl 39.5 mm, MBM 304652:A, carapace, eyestalks, antennae, antennules, dorsal view; B, carapace, eyestalk, antenna, antennule, left lateral view; C, sternites 6–8, pereopodal coxae 3–5, ventral view; D, pleon, left lateral view; E, anterior carapace, antennae, antennules, mandibles, labium, ventral view; F, left antenna, lateral view; G, left maxilliped 3, outer view; H, left maxilliped 3, ischium, inner view. Scales = 1 mm.

FIGURE 3. Ctenocheles sinicus sp. nov., holotype male, cl 8.1 mm, tl 39.5 mm, MBM 304652: A, right (major) cheliped, mesial view; B, right (major) cheliped, lateral view; C, right (major) cheliped, anterior propodus, fingers, mesial view; D, left (minor) cheliped, mesial view; E, left (minor) cheliped, lateral view; F, left (minor) cheliped, fingers, mesial view. Scales = 1 mm.

FIGURE 4. Ctenocheles sinicus sp. nov., holotype male, cl 8.1 mm, tl 39.5 mm, MBM 304652:A, left pereopod 2, mesial view; B, left pereopod 2, lateral view; C, left pereopod 3, mesial view; D, left pereopod 3, lateral view; E, left pereopod 4, mesial view; F, left pereopod 4, lateral view; G, left pereopod 5, mesial view; H, left pereopod 5, lateral view. Scale = 1 mm.

FIGURE 5. Ctenocheles sinicus sp. nov., (A–F) holotype male, cl 8.1 mm, tl 39.5 mm, MBM 304652; (G, H) paratype female, cl 9.9 mm, tl 51.2 mm, MBM 304653: A, left pleopod 1, posterior view; B, left pleopod 2, anterior view; C, left pleopod 2, posterior view; D, left pleopod 3, anterior view; E, left pleopod 3, posterior view; F, posterior pleonite 6, telson, uropods, dorsal view; G, left pleopod 1, anterior view; H, left pleopod 2, anterior view. Scales = 1 mm.

FIGURE 6. Ctenocheles sinicus sp. nov., holotype male, cl 8.1 mm, tl 39.5 mm, MBM 304652: A, anterolateral carapace, maxillipeds 2 and 3, pereopodal coxae 1 and 2, lateral view; B, left maxilliped 2, outer view; C, left maxilliped 3, outer view; D, anterior carapace, antennules, antennae, mandibles, labium, ventral view; E, left maxilliped 1, inner view; F, left maxilla, inner view; G, left maxillule, inner view; H, right mandible, outer view; I, right mandible, inner view; J, left mandible, inner view; K, left mandible, outer view. Scales = 0.5 mm. Yellow arrows indicate exopods on maxillipeds 2 and 3; white arrow indicates epipod on maxilliped 2; red arrows indicate labium.

FIGURE 7. Ctenocheles sinicus sp. nov.: (A–F) holotype male, cl 8.1 mm, tl 39.5 mm, MBM 304652; (G) paratype female, cl 9.9 mm, tl 51.2 mm, MBM 304653: A, left pereopod 2, detail of propodus and fingers, lateral view; B, left pereopod 3, details of propodus and fingers, lateral view; C, left pereopod 3, details of propodus and fingers, lateral view; D, right pereopod 4, details of propodus and fingers, mesial view; E, left pleopod 1, posterior view; F, left pleopod 2, detail of appendix masculina and appendix interna, anterior view, G, left pleopod 1, anterior view. Scales = 0.5 mm.