Eiconaxius rubrirostris, 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 : 18-21

Eiconaxius rubrirostris n. sp.

( Figs. 9 , 10 , 13 E)

Type material. Holotype: male (cl 5.4 mm), TAIWAN 2000, stn CP 55, 24°24.40’N, 122°18.0’E, 638–824 m, 4 August 2000 ( NTOU A0 0 114).

Description. Rostrum ( Fig. 9 A, B) lanceolate, apically narrowly rounded, straight, reaching slightly beyond distal margin of first segment of antennular peduncle; lateral margins nearly smooth, slightly upturned. Carapace ( Fig. 9 A, B) with gastric region very slightly convex; cervical groove faint; median carina entire, broadened posteriorly, but not distinctly bifurcate; submedian carina absent; lateral carinae reaching posteriorly to about anterior one-third of carapace length, slightly constricted posterior to orbit; submarginal carina distinct.

First and second abdominal somites damaged. Second to fourth pleura ( Fig. 9 C) angular (second and third) or rounded posteroventrally (fourth), none forming acute ventral or posteroventral tooth, fifth pleura generally rounded ventrally; anterolateral margin of fourth and fifth pleura each with minute tooth ventrally; sixth abdominal somite short, with 3 obtuse small protuberances on posterodorsal margin, unarmed on pleural ventral margin. Telson ( Fig. 9 D) with greatest width at anterior 0.25 length, with 8 serrations, including 1 tiny posterolateral one, on lateral margin; moderately small posteromedian tooth present.

Eye ( Fig. 9 A) reaching midlength of rostrum; cornea subglobose, not faceted, lacking pigment. Antennular peduncle ( Fig. 9 A, B) with distal two segments subequal in length to first segment; flagella nearly as long as carapace. Antennal peduncle ( Fig. 9 A, B) moderately stout; distolateral prolongation of second segment acute, overreaching distal margin of second segment of antennular peduncle; third segment with small 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 moderately slender (distal half missing).

Third maxilliped ( Fig. 10 A) moderately slender for genus; ischium with crista dentata consisting of row of tiny denticles

Major (right) cheliped ( Fig. 10 B, C) massive. Ischium unarmed on ventral margin. Merus strongly compressed laterally; dorsal margin strongly convex, bearing minute denticle distal to midlength, but otherwise smooth, terminating distally in minute tooth; ventromesial margin sharply carinate, with 1 minute subterminal denticle; laterodistal projection subacute. Carpus cup shaped, much wider than long, ventral angle faintly dentate. Chela slightly longer than carapace (including rostrum). Palm 1.05 times longer than high, dorsal margin sharply carinate, terminating distally in small subacute tooth, with tiny denticle somewhat proximal to dorsodistal tooth, lateral surface convex with several scattered tubercles in distal half; ventrolateral carina sharp, extending to distal 0.20 of fixed finger, accompanied with deep groove; mesial surface also with scattered tubercles in distal half. Fixed finger nearly straight but distally slightly upturned, with 1 blunt, small but distinct tooth arising at about mid-length, otherwise minutely dentate; finger cleft shallowly excavate; lateral face flanked by blunt upper ridge along cutting edge and ventrolateral ridge concave. Dactylus nearly as long as palm, terminating in slightly curved calcareous claw, dorsal margin sharply carinate; lateral surface shallowly sulcate along dorsal carina; cutting edge with 1 obtuse tooth proximally, otherwise unarmed.

Minor (left) cheliped ( Fig. 10 D) slightly shorter and less stout than major cheliped. Ischium with 1 minute denticle slightly distal to midlength. Merus strongly compressed laterally; dorsal margin sinuous, sharply carinate, bearing 3 minute denticles distal to midlength, terminating distally in minute denticle; ventromesial margin sharply carinate, with 2 tiny subdistal spinules; laterodistal projection subacute. Carpus cup shaped, much wider than long, ventral angle faintly dentate. Chela subequal in length to carapace (including rostrum). Palm slightly becoming wider distally, 1.1 times higher than long; dorsal margin sharply carinate, smooth, terminating distally in minute denticle; lateral surface generally convex, smooth; ventrolateral carina sharp, extending to midlength of fixed finger; mesial surface smooth. Fixed finger slightly deflexed, almost straight but distally slightly upturned, with row of small, triangular or rounded teeth over entire length; finger cleft with 3-spined cusp laterally; lateral face flanked by sharp upper ridge along cutting edge and ventrolateral ridge shallowly concave. Dactylus about 1.4 times as long as palm, terminating in slightly curved calcareous claw, dorsal margin sharply carinate; lateral surface with distinct longitudinal carina on midline; cutting edge faintly dentate.

Second to fourth pereopods of similar length, moderately stout. Second pereopod ( Fig. 10 E) 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; dactylus about 0.6 times as long as palm, setose, also with row of minute corneous spinules on cutting edge. Third pereopod ( Fig. 10 F) unarmed on ischium to carpus; propodus about 1.5 times longer than carpus, with 5 sets of slender spiniform setae on lateral surface ventrally and 1 spiniform seta at ventrodistal margin; dactylus ( Fig. 10 H) strongly compressed laterally, suboval, terminating in clearly demarcated claw, with about 8 spiniform setae on flexor margin and 1 set of 2 slender spiniform setae on lateral surface. Fourth pereopod ( Fig. 10 G) similar to third pereopod; propodus with 7 sets of spiniform setae and 1 ventrodistal spiniform seta; dactylus with 9 spiniform setae on flexor margin and 1 set of 3 spiniform setae on lateral surface. Fifth pereopods missing.

First pleopod absent. Second to fifth pleopods slender, biramous, each with appendix interna; appendix masculina on second pleopod subequal to appendix interna, bearing about 10 stiff setae. Uropodal exopod ( Fig. 9 D) with about 13 serrations on lateral and posterior margins, posteriormost one larger than others, mesial margin nearly regularly convex; endopod ( Fig. 9 D) with about 7 serrations increasing in size posteriorly.

Coloration. Body generally whitish, but rostrum distinctly reddish; cornea of eye opaque.

Distribution. Known only from northeastern Taiwan; at depths of 638- 824 m.

Remarks. Affinities of this new species are given under Eiconaxius kensleyi n. sp.

Etymology. The Latin “ rubrirostris ” refers to the distinctly red rostrum in this new species.

Figures

FIGURE 9. Eiconaxius rubrirostris n. sp., holotype, male (cl 5.4 mm), NTOU A 00114. A, carapace and cephalic appendages, lateral view (antennular and antennal flagellum partially broken off); B, anterior part of carapace and cephalic appendages, dorsal view (antennular and antennal flagellum partially omitted); C, abdomen, telson and uropod, lateral view (first and second somites damaged); D, telson and left uropod, dorsal view (setae omitted). Scale bars: 1 mm.

FIGURE 10. Eiconaxius rubrirostris n. sp., holotype, male (cl 5.4 mm), NTOU A 00114. A, right third maxilliped, lateral view; B, chela and carpus of right cheliped, lateral view; C, merus and ischium of right cheliped, lateral view; D, left cheliped, lateral view; E, right second pereopod, lateral view; F, right third pereopod, lateral view; G, right fourth pereopod, lateral view; H, same, dactylus and distal part of propodus, lateral view. Scale bars: A – G = 1 mm; H = 0.5 mm.

FIGURE 13. A, Formosaxius dorsum n. gen., n. sp., holotype, female (cl about 12.0 mm), NTOU A 01087; B, Formosaxius dorsum n. gen., n. sp., paratype, female (cl 12.6 mm), NTOU A 00023; C, Ambiaxius propinquus n. sp., holotype, hermaphrodite (cl 11.8 mm), NTOU A 00110; D, Calastacus formosus n. sp., holotype, hermaphrodite (cl 7.6 mm), NTOU A 00083; E, Eiconaxius rubrirostris n. sp., holotype, male (cl 5.4 mm), NTOU A 00114; F, Eiconaxius kensleyi n. sp., holotype, male (cl 3.1 mm), NTOU A 00111.