Eiconaxius kensleyi, Lin, Tomoyuki Komai Feng-Jiau & Chan, Tin-Yam, 2010

Lin, Tomoyuki Komai Feng-Jiau & Chan, Tin-Yam, 2010, Five new species of Axiidae (Crustacea: Decapoda: Axiidea) from deep-water off Taiwan, with description of a new genus, Zootaxa 2352, pp. 1-28 : 21-26

publication ID	https://doi.org/ 10.5281/zenodo.193489
DOI	https://doi.org/10.5281/zenodo.6211761
persistent identifier	https://treatment.plazi.org/id/038C87AC-5E5C-FFB1-43E0-CCD653B5CE96
treatment provided by	Plazi
scientific name	Eiconaxius kensleyi
status	sp. nov.

Treatment

Eiconaxius kensleyi View in CoL n. sp.

( Figs. 11 View FIGURE 11 , 12 View FIGURE 12 , 13 View FIGURE 13. A F)

Type material. Holotype: male (cl 3.1 mm), TAIWAN 2000, stn DW 45, 22°47.10’N, 121°27.30’E, 439 m, 2 August 2000 ( NTOU A0 0 111).

Description. Rostrum ( Fig. 11 View FIGURE 11 A–C) lanceolate, apically narrowly rounded, straight, slightly overreaching distal margin of first segment of antennular peduncle; lateral margins faintly serrulate, slightly upturned.

Carapace ( Fig. 11 View FIGURE 11 A, B) with gastric region slightly convex; cervical groove absent; median carina entire, slightly broadened posteriorly, but not distinctly bifurcate; submedian carina absent; lateral carinae reaching posteriorly to about anterior one-fourth of carapace length, not constricted posterior to orbit; submarginal carina less distinct.

First abdominal pleuron ( Fig. 11 View FIGURE 11 D) with strongly convex anterior margin; second to fourth pleura with angular posterolateral margins none forming acute ventral or posteroventral tooth; fifth pleura broadly rounded; anterolateral margins of second to fifth pleura unarmed; sixth abdominal somite short, unarmed on posterodorsal margin or ventral margin. Telson ( Fig. 11 View FIGURE 11 E) with greatest width at about midlength, with 5 (left) or 6 (right) serrations on lateral margin, including 1 tiny posterolateral one; moderately small posteromedian tooth present.

Eye ( Fig. 11 View FIGURE 11 A, B) reaching midlength of rostrum; cornea subglobose, not faceted, lacking pigment. Antennular peduncle ( Fig. 11 View FIGURE 11 A, B) with distal two segments subequal in length to first segment; flagella longer than carapace. Antennal peduncle ( Fig. 11 View FIGURE 11 A, B) moderately stout; distolateral prolongation of second segment acute, overreaching distal margin of third segment of antennular peduncle; third segment with relatively large spine at ventromesial distal angle; antennal acicle large, acuminate, reaching nearly to distal margin of fifth segment of antennal peduncle or far overreaching distal margin of antennular peduncle; flagellum missing.

Third maxilliped moderately slender for genus; ischium with crista dentata consisting of row of tiny denticles.

Major (right) cheliped ( Fig. 12 View FIGURE 12 A) massive. Ischium with 1 tiny tooth subterminally on dorsal and ventral margins respectively. Merus strongly compressed laterally; dorsal margin strongly convex, sharply carinate, bearing 1 minute denticle distal to midlength, but otherwise smooth, terminating distally in tiny tooth; ventromesial margin sharply carinate, with 1 relatively large subterminal tooth and 1 minute denticle; distolateral projection blunt. Carpus cup-shaped, much higher than long, ventral angle faintly dentate. Chela slightly longer than carapace (including rostrum). Palm 1.2 times longer than high, dorsal margin distinctly carinate, terminating distally in small acute tooth, with 2 tiny denticles somewhat proximal to dorsodistal tooth, lateral surface convex with few scattered tubercles proximal to base of dactylus; ventrolateral carina sharp, extending to distal 0.25 of fixed finger, accompanied with deep groove; distinct submarginal carina along finger cleft; mesial surface also with few scattered tubercles. Fixed finger nearly straight with distal part very slightly curved, with 1 blunt, distinct tooth arising at about mid-length, otherwise nearly smooth; finger cleft shallowly excavate; lateral face slightly concave. Dactylus shorter than palm, terminating in curved calcareous claw, dorsal margin sharply carinate; lateral surface faintly sulcate along dorsal carina; cutting edge with 1 large, obtuse tooth proximally and with broad convexity subdistally.

Minor (left) cheliped ( Fig. 12 View FIGURE 12 B) subequal in length to and less stout than major cheliped. Ischium with 1 tiny subdistal denticle on dorsal and ventral margins respectively. Merus strongly compressed laterally; dorsal margin strongly convex, distinctly carinate, bearing 2 minute denticles in distal half, terminating distally in minute denticle; ventromesial margin sharply carinate, with 1 relatively large subdistal tooth accompanying by 1 tiny tooth; distolateral projection subacute. Carpus cup shaped, much wider than long, ventral angle faintly dentate. Chela slightly longer than carapace (including rostrum). Palm slightly becoming wider distally, 1.1 times longer than high; dorsal surface weakly carinate in distal half, rounded in proximal half, entire, terminating distally in small tooth; lateral surface generally convex, smooth; ventrolateral carina distinct, but not very sharp, extending from midlength of palm to midlength of fixed finger. Fixed finger slightly deflexed, almost straight but distally slightly curved, cutting edge very faintly dentate; finger cleft with sharply pointed, triangular cusp; lateral face shallowly concave, flanked by distinct upper ridge along cutting edge and ventrolateral ridge shallowly concave. Dactylus about 1.3 times longer than palm, terminating in curved calcareous claw, dorsal margin bluntly carinate; lateral surface smooth; cutting edge with 1 small subacute tooth proximally, but otherwise nearly entire.

Second to fourth pereopods of similar length, moderately stout. Second pereopod ( Fig. 12 View FIGURE 12 C) unarmed on ischium to carpus; chela about 1.5 times longer than carpus, with scattered tufts of setae; fixed finger slightly deflexed, with row of minute corneous spinules on cutting edge ( Fig. 12 View FIGURE 12 D); dactylus about 0.5 times as long as palm, with some tufts of long setae and with row of minute corneous spinules on cutting edge ( Fig. 12 View FIGURE 12 D). Third pereopod ( Fig. 12 View FIGURE 12 E) unarmed on ischium to carpus; propodus about 1.5 times longer than carpus, with 4 sets of slender spiniform setae (each consisting of 2 or 3 spiniform setae) and 1 spiniform seta on lateral surface ventrally and 1 spiniform seta at ventrodistal margin ( Fig. 12 View FIGURE 12 F); dactylus ( Fig. 12 View FIGURE 12 F) strongly compressed laterally, suboval, terminating in clearly demarcated claw, with 7 accessory spinules on flexor margin; lateral surface unarmed. Fourth pereopod ( Fig. 12 View FIGURE 12 G) similar to third pereopod; propodus with 4 sets of slender spiniform setae and 1 ventrodistal spiniform seta; dactylus with 7 spiniform setae on flexor margin; lateral surface unarmed. Fifth pereopod ( Fig. 12 View FIGURE 12 H) shorter than preceding pereopods; dactylus suboval, terminating in clearly demarcated claw, armed with 5 spiniform setae on flexor margin; propodus with grooming apparatus ventrodistally.

First pleopod absent. Second to fifth pleopods slender, biramous, each with appendix interna; appendix masculina on second pleopod subequal to appendix interna, bearing about 6 stiff setae. Uropodal endopod ( Fig. 11 View FIGURE 11 E) with about 10 serrations, more closely spaced posteriorly; exopod ( Fig. 11 View FIGURE 11 E) with about 14 serrations on lateral and posterior margins, posteriormost one slightly larger than others, mesial margin nearly regularly convex.

Coloration. Body including eyes whitish overall, except base of rostrum reddish.

Distribution. Known only from southeastern Taiwan; at depth of 439 m.

Remarks. The two new species described in this study appear close to E. laccadivensis (Alcock & Anderson, 1894) and E. mortenseni Sakai, 1992 in the entire median carina on the carapace, which is not bifurcate but slightly broadened posteriorly, and the non-acuminate pleura of the second to fifth abdominal somites. From E. laccadivensis , these two new species differ in the rostrum only slightly overreaching the distal margin of the first segment of the antennular peduncle, rather than reaching the distal segment of the antennular peduncle in E. laccadivensis (cf. Alcock 1901; Alcock & McGilchrist 1905). Alcock (1901) noted that the cutting edge of the fixed finger of E. laccadivensis carried two enlarged teeth separated by a characteristic notch near the finger cleft, although which cheliped is not specified. Concerning the general pattern of the armature found in species of Eiconaxius , it can be assumed that Alcock (1901) mentioned the major cheliped. In the two new species, the cutting edge of the fixed finger of the major cheliped is armed only with one blunt tooth at the midlength. Furthermore, the lateral margin of the rostrum is entire in E. rubrirostris n. sp., but microscopically serrulate in E. laccadivensis (cf. Alcock 1901) and E. kensleyi n. sp. The two new species are distinguished from E. mortenseni by the shape of the rostrum. The rostrum is lanceolate with a narrow, blunt apex in the two new species, while it is rounded in E. mortenseni ; the lateral margin is serrulate in E. kensleyi n. sp. but entire in E. mortenseni and E. rubrirostris n. sp. The minor cheliped of E. rubrirostris n. sp. is provided with a distinct median carina on the lateral surface of the dactylus, which is absent in E. mortenseni or obsolete in E. kensleyi n. sp. Furthermore, the ventrolateral carina extending from palm to fixed finger of the minor cheliped seems to be more pronounced in E. rubrirostris n. sp. than in E. mortenseni and E. kensleyi n. sp. Eiconaxius rubrirostris n. sp. further differs from E. kensleyi n. sp. in the slightly constricted lateral carinae on the carapace, the possession of three tiny denticles on the posterodorsal margin of the sixth abdominal somite, the lack of a sharp dorsodistal tooth on the palm of the major cheliped, and the more strongly denticulate cutting edge of the minor chela. In Eiconaxius kensleyi n. sp., the lateral carinae of the carapace are not constricted; the posterodorsal margin of the sixth abdominal somite is unarmed; the palm of the major cheliped is armed with a small, but distinct dorsodistal tooth; the cutting edge of the minor chela is only faintly denticulate. The armament of the ventral margin of the merus of the major cheliped may be also significant, although some degree of variation is seen in other species of the genus (T. Komai, personal observation). Eiconaxius rubrirostris n. sp. possesses only a minute subterminal denticle on the ventral margin of the merus of the major cheliped, whereas E. kensleyi n. sp. has a conspicuous subterminal tooth on that margin.

Eiconaxius andamanensis (Alcock, 1901) is also rather similar to the two new species. Nevertheless, E. andamanensis seems to differ from these two new species by the short antennal acicle, which does not reach the distal margin of the fifth segment of the antennal peduncle, and the sharply pointed posterolateral angles of the second to fourth pleura (Alcock 1901). In the two new species, the second to fourth pleura are angular or rounded; and the antennal acicle nearly reaches the distal margin of the fifth segment of the antennal peduncle.

Etymology. This new species is dedicated to the late Brian Kensley of the National Museum of Natural History, Smithsonian Institution, in recognition of his significant contributions to the systematics of malacostracan crustaceans, particularly Axiidea.