Guyanacaris xinzhengi, Kou & Poore & Liu, 2024

Kou, Qi, Poore, Gary C. B. & Liu, Xinming, 2024, Description of a new species of Guyanacaris Sakai, 2011 (Decapoda: Axiidea: Axiidae) from the South China Sea, Raffles Bulletin of Zoology 72, pp. 62-70 : 63-69

Guyanacaris xinzhengi , new species

( Figs. 1–5 )

Material examined. Holotype, male (cl 14.9 mm, tl 40.5 mm), Beibu Gulf , northern continental shelf of the South China Sea, Northwest Pacific, 250–300 m depth, fishing vessel, bottom trawl, 4 November 2020, MBM 304660 .

Etymology. The new species is named after Dr. Xinzheng Li, principal investigator at the Institute of Oceanology, Chinese Academy of Sciences (IOCAS), who is also the first Chinese marine biologist to take the manned submersibles “ Jiaolong ” and “ Deep-sea Warrior ” to explore the deep sea, and for his great contribution to deep-sea research and crustacean taxonomy in China. Two of the authors (QK, XL) are grateful for his mentoring and guidance.

Diagnosis. Rostrum reaching midlength of antennular peduncle article 2, with 5–7 lateral teeth. Lateral gastric carina with 8 or 9 teeth; submedian gastric carina with 6 teeth; median gastric carina with 7 anterior teeth, 1 tubercle and 6 posterior teeth. Eyestalk reaching tip of rostrum. Chelipeds unequal, dissimilar. Major cheliped, merus upper margin with 2 prominent teeth and lower margin with 5 prominent teeth; carpus upper margin tuberculate; palm upper margin tuberculate, with 1 prominent proximal tooth and short longitudinal submesial row of 8 teeth; fixed finger opposable margin with notch and 1 triangular tooth in proximal half; dactylus 0.8 times as long as palm, opposable margin with 1 prominent bifid proximal tooth and 1 triangular notch in proximal half, upper margin unarmed. Minor cheliped, merus with 3 prominent teeth on upper margin and 5 prominent teeth on lower margin; carpus with upper margin tuberculate; palm upper margin tuberculate, with 1 prominent proximal tooth and a row of 8 teeth; fixed finger opposable margin sharply denticulate; dactylus 1.7 times as long as palm, opposable margin denticulate, upper margin unarmed. Uropodal endopod with 2 teeth on anterior margin; 1 anterolateral tooth; dorsal surface with longitudinal ridge armed with 4 or 5 teeth. Uropodal exopod with 5 or 6 teeth on anterior margin; anterolateral angle with 1 prominent spiniform setae; dorsal surface with longitudinal ridge armed with 3 teeth. Telson with 3–5 lateral teeth, 3 pairs of small posterolateral teeth and 1 median tooth.

Description. Body robust, integument solid, surface sparsely setose. Rostrum triangular in dorsal view, bending downward, 0.13 times as long as carapace, 1.8 times as long as wide at base, apex acute, reaching midlength of antennular peduncle article 2; lateral margins with 7 (left), 5 (right) small, shallow teeth, continuous with lateral carinae; ventral margin unarmed.

Carapace smooth, sparsely setose, anterolateral margin with 1 small antennal spine; cervical groove distinct, unarmed,

Kou et al.: A new axiidean shrimp from the South China Sea almost reaching anteroventral pterygostomial angle; gastric region slightly inflated, with 5 longitudinal carinae, distinct, entire, reaching cervical groove; median carina armed with 7 anterior teeth, 1 small tubercle and 6 posterior teeth; submedian gastric carinae armed with 6 teeth; lateral carinae armed with 1 supraocular tooth and 8 (left) or 9 (right) prominent teeth; postcervical carina distinct, extending almost to posterior end of carapace; inferior orbital angle and pterygostomial angle rounded, unarmed.

Thoracic sternite 6 with median groove separating pair of acute opposing teeth. Sternite 7 subrectangular, concave in midline, with sharp anterolateral angles.

Pleonites sparsely setose, dorsal surface with distinct, longitudinal median carina and pair of submedian carinae; pleonite 1 0.65 times as long as pleonite 2, pleuron posteroventrally subacute, unarmed; pleonites 2–5 subequal in dorsal length, pleura posteroventrally nearly right-angled, with 1–6 minute teeth on ventral margin; pleonite 6 1.4 times as long as pleonite 5, pleuron ventrally rounded, with a small tooth at anterior ⅓, posterolateral projection subacute, posterior margin unarmed.

Eyestalk cylindrical, reaching tip of rostrum, unarmed; cornea pigmented, division between cornea and eyestalk clear.

Antennular peduncle reaching almost distal margin of antennal article 4; article 1 with statocyst, with acute stylocerite; article 2 0.25 times as long as article 1, 1.2 times as long as wide; article 3 1.3 times as long as article 2, 1.7 times as long as wide. Antennal peduncle article 1 bearing 1 prominent tooth and 6 or 7 denticles on ventrodistal margin; article 2 with 1 blunt ventrolateral tooth, distal spine acute, reaching middle of scaphocerite; scaphocerite slender, acute, reaching midlength of article 4, with 1 small proximal mesial tooth; article 3 with 1 acute ventromesial tooth; article 4 3.4 times as long as wide; article 5 0.60 times as long as of article 4.

Maxilliped 3 coxa and basis with 1 distomesial spine; ischium 1.1 times as long as merus, mesial margin with 2 small spines, crista dentata of 17 small teeth; merus 1.2 times as long as carpus, armed with 4 spines on mesial margin in distal half, distalmost spine largest; carpus with 1 distal spine on mesial margin, 0.90 times as long as propodus; propodus unarmed, 1.7 times as long as dactylus; dactylus cylindrical, 2.5 times as long as wide; exopod distal half segmented, reaching middle of carpus.

Chelipeds unequal and dissimilar, densely setose; carpuspalm length of major cheliped 0.9 carapace length, of minor cheliped 0.7 carapace length. Major (left) cheliped, coxa and basis with 1 distal tooth on mesial margin; ischium compressed laterally, 0.60 times as long as wide, armed with 5 teeth on lower margin, distalmost tooth largest, upper margin unarmed; merus 3.6 times as long as ischium, lower margin with 5 prominent teeth, subequal in size, upper margin arcuate, with 2 prominent teeth, distoventral angle with 1 acute tooth; carpus 0.70 times as long as merus, lower margin unarmed, upper margin tuberculate, distal margin finely denticulate; propodal palm inflated, slightly longer than merus, upper margin 1.1 times as long as wide, tuberculate, with 1 prominent proximal tooth and short longitudinal submesial row of 8 teeth, lateral and mesial surfaces with few scattered tubercles, lower-lateral carina sharp, extending to midlength of fixed finger, with 28 submarginal tubercles, distolateral margin with 1 small acute tooth, distomesial margin oblique, unarmed; fixed finger 0.70 times as long as palm, distally slightly upturned, lower margin unarmed, opposable margin with shallow concavity over proximal third, 1 prominent triangular tooth at midlength, followed by several weak teeth distally; dactylus 0.8 times as long as palm, distally curved, upper margin unarmed, opposable margin with 1 prominent bifid proximal tooth and several weak teeth distally, separated by 1 triangular notch. Minor (right) cheliped shorter, more slender than major, palm 0.70 times width of major; coxa and basis with 1 distal tooth on mesial margin; ischium compressed laterally, 0.6 times as long as wide, with 4 teeth on lower margin, upper margin unarmed; merus 3.5 times as long as ischium, lower margin armed with 5 prominent teeth, subequal in size, upper margin arcuate, armed with 3 prominent teeth, distoventral angle with 1 acute tooth; carpus 0.6 times as long as merus, lower margin unarmed, upper margin tuberculate, distal margins finely denticulate; propodal palm slightly inflated, slightly shorter than merus, upper margin 1.1 times as long as wide, tuberculate, with 1 prominent proximal tooth and submesial longitudinal row of 8 teeth, lateral and mesial surfaces with few scattered tubercles, lower-lateral carina sharp, extending almost to distal third of fixed finger, with 33 submarginal tubercles, distolateral margin with 3 teeth, distomesial margin with 5 denticles; fixed finger 1.5 times as long as palm, nearly straight, distally slightly upturned, opposable margin with row of irregular sharp teeth along whole length, below with additional ridge of 13 teeth on mesial surface; dactylus 1.4 times as long as palm, distally curved, upper margin unarmed, opposable margin with row of sharp teeth along whole length, above with 3 proximal teeth on mesial surface.

Pereopod 2 coxa with 1 mesial and 1 distomesial tooth; basis with 1 mesial tooth; ischium 1.5 times as long as wide, with 3 prominent teeth on lower margin; merus 3.7 times as long as ischium, upper margin unarmed, lower margin with 3 prominent teeth, plus 1 subdistal tooth on lateral surface; carpus 0.5 times as long as merus, unarmed; palm unarmed, 0.7 times as long as carpus, 1.8 times as long as wide; fingers as long as palm, terminating in corneous unguis, opposable margins with row of 26 spinules.

Pereopod 3 coxa with 1 mesial teeth; basis unarmed; ischium 1.8 times as long as wide, unarmed; merus 4.3 times as long as ischium, upper and lower margins unarmed, lateral surface with 1 prominent subdistal tooth; carpus half as long as merus, unarmed; propodus 1.4 times as long as carpus, lateral surface with 10 (left), 7 (right) spiniform setae along whole length, mesial surface unarmed, 1 long spiniform seta at lower distal angle; dactylus lanceolate, densely setose, lateral surface with 9 (left), 8 (right) spiniform setae, mesial surface unarmed, terminating in corneous unguis.

Pereopod 4 similar to pereopod 3, slightly shorter. Right side missing. Left with propodus lateral surface with 2 rows of 23 spiniform setae along whole length, mesial surface unarmed, 1 long and 3 short spiniform setae at lower distal angle, distal lower-mesial surface densely setose; dactylus lateral surface with 6 spiniform setae, mesial surface unarmed, terminating in corneous unguis.

Pereopod 5 left side missing. Right with precoxal lobe suboval; coxa with gonopore, coxa to carpus unarmed; propodus subchelate, distal lower-lateral surface densely setose, with 7 slender spinules at lower distal angle; dactylus slightly twisted, densely setose, upper-mesial surface with 1 spiniform seta, lateral surface unarmed, terminating in corneous unguis.

Pleopod 1 uniramous, rod-like, slightly tapering, 7.0 times as long as wide. Pleopod 2 biramous; endopod slightly longer than exopod; appendix masculina rod-like, 0.20 times as long as endopod, with numerous terminal setae; appendix interna 1.2 times as long as appendix masculina, tip slightly curved, bearing cluster of small hooks. Pleopods 3–5 similar, biramous, endopod slightly longer than exopod; with appendix interna, slender, 0.35 times as long as endopod.

Uropod almost as long as telson, marginally densely setose; peduncle stout, unarmed; endopod 1.6 times as long as wide, with 2 subdistal teeth on anterior margin and 1 longer anterodistal tooth, distoposterior margin unevenly rounded, dorsal surface with longitudinal ridge and row of 4 (left), 5 (right) teeth; exopod with almost complete transverse suture, 1.3 times as long as wide, slightly longer than endopod, anterior margin armed with 6 (left), 5 (right) small teeth over distal two-thirds, anterodistal angle with 1 prominent spiniform seta, distoposterior margin rounded, dorsal surface with longitudinal ridge armed with 3 teeth; transverse suture with 11 (left), 10 (right) denticles; exopod and endopod both with short simple setae and long plumose setae along posterodistal margins.

Telson subrectangular, 1.4 times as long as wide, lateral margins parallel, straight, with 3 (left), 5 (right) small teeth, posterior margin rounded, with prominent median tooth, posterolateral angle with 3 denticles; dorsal surface armed with 2 pairs of teeth, with dense short simple setae, midline concave, posterolateral and posterior margins with long plumose setae.

Colour in life. Body and pereopods generally orange; carapace with 4 transverse, white bands; each pleonite with 1 white transverse band; pleopods, telson and uropodal endopods entirely orange; uropodal exopods generally white with posterior margin orange. Cornea of eye brownish, opaque; eyestalk orange ( Fig. 1 ).

Distribution. Known only from the type locality: Beibu Gulf, the South China Sea, 250–300 m depth.

GenBank accession numbers. OR886605 (16S rRNA), OR887453 (COI).

Figures

Fig. 1. Guyanacaris xinzhengi, new species. Holotype, MBM 304660 (male, cl 14.9 mm, tl 40.5 mm), colour in life. Dorsal view (above), lateral view (below). Scale=1 cm.

Fig. 2. Guyanacaris xinzhengi, new species. Holotype, MBM 304660 (male, cl 14.9 mm, tl 40.5 mm). A, carapace, eyestalks, antenna, antennule, dorsal view; B, carapace, eyestalk, antenna, antennule, lateral view; C, anterior carapace, antenna, antennule, ventral view; D, sternites 6–8, pereopodal coxae 3–5, ventral view; E, pleon, pleopod 1, lateral view; F, maxilliped 3, left, outer view; G, same, ischium, inner view. Scale=1 mm.

Fig. 3. Guyanacaris xinzhengi, new species. Holotype, MBM 304660 (male, cl 14.9 mm, tl 40.5 mm). A, major cheliped, left, mesial view; B, same, lateral view; C, minor cheliped, right, lateral view; D, same, mesial view. Scale=5 mm.

Fig. 4. Guyanacaris xinzhengi, new species. Holotype, MBM 304660 (male, cl 14.9 mm, tl 40.5 mm). A, pereopod 2, right, lateral view; B, same, fingers, lateral view; C, pereopod 3, left, lateral view; D, same, dactylus, lateral view; E, same, dactylus, mesial view; F, pereopod 4, left, lateral view; G, same, dactylus, lateral view; H, same, dactylus, mesial view; I, pereopod 5, right, lateral view; J, same, dactylus, lateral view; K, same, dactylus, mesial view. Scale=1 mm.

Fig. 5. Guyanacaris xinzhengi, new species. Holotype, MBM 304660 (male, cl 14.9 mm, tl 40.5 mm). A, pleonite 1, pleopods 1, ventral view; B, pleopod 1, left, lateral view; C, pleopod 2, right, anterior view; D, same, appendix masculina, appendix interna, anterior view; E, posterior pleonite 6, telson, left uropod, dorsal view; F, posterior telson, dorsal view. Scale=1 mm.