Guyanacaris keralam Padate & Cubelio & Takeda 2022, sp. nov.
Creators: name: Padate, Vinay P.
name: Cubelio, Sherine Sonia
name: Takeda, Masatsune
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Axiidae
Guyanacaris
Guyanacaris keralam

description: Guyanacaris keralam sp. nov.
(Figs 2–5)
urn:lsid:zoobank.org:act: 6FE055EC-2D4E-46C7-80ED-4C30F540F940
Material examined. Holotype. Male (CMLRE / IO /SS/AXI/00001, CL 50.0 mm, TL 119.0 mm), Arabian Sea, west off Kasaragod, Kerala, India, FORVSS station 31810, 12.10°N, 74.32°E, 316–326 m depth, 26 August 2013, Expo model trawl, coll. Dr. Rajool Shanis C.P.
Diagnosis. Rostrum with 4 or 5 lateral spines. Lateral gastric carina with 5 spines; submedian gastric carina with 6 spines; median gastric carina with 3 anterior spines, 1 tubercle and 4 posterior spines. Eyestalk short of midlength of rostrum. Antennular peduncle not reaching to distal margin of antennal article 4. Antennal article 4 longer than article 2, scaphocerite overreaching midlength of article 4. Chelipeds subequal, major P1 dactylus with 6 erect dorsal spines, minor P1 dactylus with 5 erect dorsal spines; fingers at least 3 times palm length. P3–4 propodi and dactyli with corneous movable spines.
Description of holotype. Carapace minutely granular, sparsely setose (Figs 1A, C, 2A, B). Rostrum acute, 0.19 times post-rostral carapace length, 0.45 times length of front-to-cervical groove, acute, short of base of distalmost antennular article, and midlength of penultimate antennal article (article4), bearing 4lateral spines on the right margin, 5 lateral spines on the left margin anterior to supraocular spine, weakly continuous with lateral gastric carinae (Figs 1A, C, 2A, B, D). Supraocular spine slightly shorter than rostral spines, anterolateral margin with 1 antennal spine. Lateral gastric carina bearing 5 spines; submedian gastric carina bearing 6 spines; median gastric carina bearing 3 anterior spines, 1 tubercle and 4 posterior spines; cervical groove distinct, extending anteriorly up to hepatic region, unarmed; post-cervical and branchiostegal regions unarmed, low median longitudinal post-cervical carina present (Figs 1A, C, 2A, B, D). Thoracic sternite 7 (P4) deeply divided in midline over posterior two-thirds, bearing sharp oblique lateral ridge; sternite 8 (P5) with setose semicircular flap on anterior face at base of P5 (Figs 1B, 2C).
Pleonal 1 pleuron twice as deep as middorsal length, bearing 1 ventral spine; pleuron 2 broad, lateral length 1.6 times dorsal length, gently convex anteroventrally, bearing 13 marginal spines ventrally; pleura 3–5 ventrally subquadrate, posterior margins almost straight, pleura 3–4 bearing 6 marginal spines each, pleuron 5 bearing 5 marginal spines; pleuron 6 bluntly triangular, bearing 1 ventral spine (Figs 1A, C, 2A); pleura 1–5 with lateral crease (Figs 1C, 2A).
Ocular peduncle 0.46 times rostral length; cornea lightly pigmented (Fig. 2B, D). Antennular peduncle not reaching to distal margin of penultimate antennal article (article 4) (Fig. 2B, D, E, F). Antennal article 1 bearing 1 spine on distoventral margin, ventral margin with 1 row of blunt spinules; article 2 distal spine (stylocerite) slender, directed anteriorly, short of midlength of antennal article 4; scaphocerite gently curved, overreaching midlength of article 4, bearing mesial spine at base; article 3 with broad mesiodistal spine on ventral margin; article 4 length 1.40 times length of article 2 (excluding distal spine); article 5 0.46 times length of article 4 (Fig. 2B, D, E, F).
Pleurobranch gills absent; well-developed epipods and podobranch gills on maxillipeds 2–3 and pereopods 1–4; 2 arthrobranch gills each on maxilliped 3 and pereopods 1–4.
Maxilliped 3 coxa bearing 1 spine; basis bearing 1 spine; ischium ventral margin bearing 3 spines, crista dentata with 17–21 teeth (Fig. 2G); right merus ventral margin bearing 4 spines (Fig. 3G), left merus with 3 spines; right carpus ventral margin bearing 1 subdistal spine, left carpus spine damaged; exopod with well-developed flagellum, reaching distal end of merus (Fig. 2H).
Chelipeds (PI) subequal in length, propodus of right P1 slightly more swollen, ornamentation slightly dissimilar. Major (right) P1 coxa bearing 1 curved spine proximally, 2 spines distally on ventral margin, lateral margin bearing 1 spine and 3 spinules; basis ventral surface bearing 1 spine, terminal spine on lateral margin behind ischial articulation; ischium ventral margin bearing 2 rows of 3–5 spines (Fig. 3A, B); merus dorsal margin bearing 5 spines, anterior 2 forming 1 pair with spinule at carpal articulation, outer ventral margin bearing 10 small spines and 8 spinules, inner ventral margin bearing 5 large spines, distoventral lobule with large hook-like spine, lateral surface sparsely spinose distally, mesial surface smooth (Fig. 3A, B); carpus dorsal surface bearing 3 spines, lateral surface bearing 12 spinules including 2 on distal margin, mesial surface bearing 1 pair of blunt spinules distally, ventral margin bearing 3 spinules distally (Fig. 3A, B); propodus dorsal margin bearing 2 irregular rows of 3–5 spines, ventral margin bearing 13 spines in lateral row, mesial surface inflated (Fig. 1B), bearing 13 spines (anterior largest), pollex (fixed finger) inner surface bearing 5 spines dorsally, lateral surface sparsely spinose, 2 irregular rows of 3 spines each proximally; pollex 3.00 times as long as upper palm, cutting edge straight with 30 bluntly triangular teeth (Fig. 3A, B); dactylus dorsal margin with 6 spines, lateral and mesial surfaces unarmed, cutting edge bearing 30 bluntly triangular teeth (Fig. 4A, B); both fingers heavily setose (Fig. 1A, B, C).
Minor (left) P1 coxa bearing 1 curved spine proximally, 2 spines distally on ventral margin, lateral margin bearing 1 spine and 3 spinules; basis ventral surface bearing 1 spine, terminal spine on lateral margin behind ischial articulation; ischium ventral margin bearing 2 rows of 3–5 spines; merus dorsal margin bearing 5 spines, 1 spinule at carpal articulation, outer ventral margin bearing 9 small spines and 8 spinules, inner ventral margin bearing 4 large spines, distoventral lobule with large hook-like spine, lateral surface sparsely spinose distally, mesial surface smooth; carpus dorsal surface bearing 2 spines, lateral surface bearing 11 spinules including 2 on distal margin, mesial surface bearing 1 pair of blunt spinules distally, ventral margin bearing 2 spinules distally; propodus dorsal margin bearing 2 irregular rows of 3–4 spines, ventral margin bearing 14 spines in lateral row, mesial surface gently inflated (Fig. 1B), bearing 10 spines (anterior largest), pollex (fixed finger) inner surface bearing 3 spines dorsally, lateral surface sparsely spinose, 2 oblique rows of spines proximally, 2 spines in upper row, 5 spines in lower row; pollex 3.20 times as long as upper palm, cutting edge straight with approximately 29 bluntly triangular teeth (Fig. 3C, D); dactylus dorsal margin with 5 spines, lateral and mesial surfaces unarmed, cutting edge bearing 33 bluntly triangular teeth (Fig. 4C, D); both fingers heavily setose (Fig. 1A, B, C).
P2 ischium bearing 1 large subdistal and 4 proximal spinules ventrally; merus bearing 1 large subdistal and 2 smaller proximal spines ventrally; carpus 0.78 times as long as chela; propodus upper margin 0.77 length of dactylus (Fig. 4A), fingers bearing pectinate teeth on cutting margins (Fig. 4A, B). P3 ischium bearing 5 proximal spinules ventrally; merus bearing 1 distoventral spine; propodus 1.22 times as long as dactylus, lateral surface bearing transverse sets of corneous spines (Fig. 4C); dactylus curved, lateral surface bearing 2 rows of 5–10 corneous spines, distal tip corneous, tapering to a claw (Fig. 4C, D). P4 ischium bearing 5 proximal spinules ventrally; merus bearing 1 distoventral spine; propodus 3.04 times as long as dactylus, lateral surface bearing transverse sets of corneous spines (Fig. 4E); dactylus curved, lateral surface bearing 2 rows of 6–11 corneous movable spines, distal tip corneous, tapering to a claw (Fig. 4E, F). P5 propodus 2.55 times as long as dactylus, subchelate, with short fixed finger (Fig. 4G); dactylus unarmed, heavily setose proximally, distal tip corneous (Fig. 4G, H).
Pleopod 1 present, bearing 2 long setae distally (Fig. 4I). Pleopod 2 endopod bearing appendix masculina and appendix interna attached at proximal one-thirds portion, appendix interna 0.33 times length of endopod, subequal to appendix masculina (Fig. 4J). Pleopods 3–5 appendix interna 0.36 times length of endopod.
Telson 1.31 times as long as broad, lateral margin bearing 3 spines in the middle third portion, 1 spine in the posterior third portion, posterior margin broadly convex, densely setose with posteromedian spine, posterolateral angle unarmed; dorsal surface with 1 pair of submedian subcircular depressions anteriorly, 2 spines in each oblique row (Fig. 4K). Uropodal endopod 1.06 times as long as wide, with 3 lateral spines, longitudinal ridge bearing 5 spines. Uropodal exopod 1.34 times as long as wide, with 3 lateral spines, dorsal surface bearing 2 longitudinal ribs, inner rib unarmed, outer rib with 2 spines, posterolateral angle with 1 fixed spine; transverse suture with 9 spines (Fig. 4K).
Preserved colouration (in formalin for 7 years and recently transferred to 70% ethanol) is brown with dark yellow setae; PI chelae and carpi light grey (Fig. 1A, B, C).
Etymology. The species name is derived from the vernacular Malayalam word “Keralam” denoting the southwestern Indian state of Kerala; used as noun in apposition.
Remarks. Poore & Collins (2009) commented that Calocaris (Calastacus) hirsutimana Boesch & Smalley, 1972, Axiopsis (Axiopsis) caespitosa Squires, 1979 referred to Acanthaxius by Sakai and de Saint Laurent (1989), and Acanthaxius polychaetes Sakai, 1994, differed from the typical Acanthaxius in the presence of male pleopod 1, absence of prominent supraocular spine, comparatively more compact propodus on the major cheliped with few lateral spines, and presence of prominent lateral spine on the telson; additionally, Acanthaxius spinulicauda (Rathbun, 1902) reportedly differed from the type species A. pilocheira K. Sakai, 1987 in possessing a less spinose carapace. They further suggested the creation of new genera to accommodate these species.
Sakai (2011) retained A. spinosissima in Acanthaxius due to the absence of male pleopod 1. He erected a new genus, Guyanacaris, for C. hirsutimana (as type species) and A. caespitosa, owing to an elongate, forwardly directed antennal scaphocerite and the presence of uniramous, bisegmented male pleopod 1. He erected another genus, Bruceaxius K. Sakai, 2011, for A. polychaetes (as type species), owing to the presence of uniramous, bisegmented male pleopod 1, with a digitiform distal segment, carapace with anterolateral spine and postcervical carina, P1 chela with unarmed dorsal margin and thickly setose lateral surfaces, fingers of larger cheliped shorter than palm, those of smaller cheliped distinctly longer than palm, and pleonal 1–5 tergites and pleura separated by longitudinal carina. Moreover, he transferred A. spinulicauda to another genus Leonardsaxius K. Sakai, 2011, owing to smooth submedian and lateral gastric carinae on the carapace.
Dworschak (2013) and Dworschak and Poore (2018) recognized Guyanacaris for G. hirsutimana and G. caespitosa. Moreover, Dworschak and Poore (2018) considered Sakai’s (2011) definition of Guyanacaris to be weak. Sakai (2015) described a second species of Bruceaxius, B. thailandensis. Poore (2020) commented that A. polychaetes K. Sakai, 1994 and A. spinosissima (Rathbun, 1906) probably belonged to Guyanacaris owing to the presence of multi-spinate lateral gastric carinae converging anteriorly on small supraocular spines, and a mesial spine at the base of scaphocerite. If A. polychaetes, type species of Bruceaxius, is considered to be a Guyanacaris, then Bruceaxius should be considered to be a synonym of Guyanacaris. With regards to B. thailandensis, it was noted that the line illustration of the antennal peduncle (Sakai 2015: Fig. 3A) did not clearly indicate the presence of a mesial spine at the base of scaphocerite. In view of this, it is herein considered that B. thailandensis differs from the typical Guyanacaris in the absence of a mesial spine at the base of scaphocerite, major P1 carpus, propodus and dactylus with tuberculate upper margins, male pleopod 2 with tri-segmented appendix masculina (Table 2). It is therefore suggested that this species may be tentatively retained in Bruceaxius.
......continued on the next page
......continued on the next page
......continued on the next page
In view of this, Guyanacaris K. Sakai, 2011, is presently considered to represent 5 species— G. caespitosa (Squires, 1979), G. hirsutimana (Boesch & Smalley, 1972), G. keralam sp. nov., G. polychaetes (K. Sakai, 1994) and G. spinosissima (Rathbun, 1906), with known geographical distribution in the Atlantic and Indo-Pacific Oceans. This genus differs from Acanthaxius Sakai & de Saint Laurent, 1989, in having short supraocular spine, the presence of post-cervical carina on the carapace, dentate margins of pleura 1–2, angular to almost straight posterior margins of pleura 3–5, scaphocerite with mesial spine at base, and the presence of male pleopod 1 (Sakai 2011; Poore 2020; present study). Morphological comparisons among the species of Guyanacaris and Bruceaxius are provided in Table 2.
Distribution. Southeastern Arabian Sea, India — 326 m.
description: Published as part of Padate, Vinay P., Cubelio, Sherine Sonia & Takeda, Masatsune, 2022, Two axiidean ghost shrimps (Crustacea: Decapoda) from India, Guyanacaris keralam sp. nov. (Axiidae) and Paragourretia galathea (K. Sakai, 2017) (Ctenochelidae), pp. 195-217 in Zootaxa 5093 (2) on pages 200-209, DOI: 10.11646/zootaxa.5093.2.4, http://zenodo.org/record/5905225