Izucaris crosnieri, Li, 2008

Li, Xinzheng, 2008, Report on some species of Palaemonidae (Crustacea, Decapoda) from French Polynesia, Zoosystema 30 (1), pp. 203-252 : 207-214

Izucaris crosnieri n. sp.

( Figs 1-4 ; 5A )

TYPE MATERIAL. — Marquesas Is. Eiao, MUSOR- STOM 9, stn CP 1157, 7°59.2’S, 140°44.2’W, 100 m, 23.VIII.1997, ovig. ♀ holotype (cl 3.10 mm) (MNHN-Na 15616). — Stn CP 1157, 7°59.2’S, 140°44.2’W, 100 m, 23.VIII.1997, 1 ♀ paratype (cl 3.41 mm) (MNHN-Na 15617). — Stn CP 1158, 7°58.7’S, 140°43.9’W, 109- 110 m, 23.VIII.1997, 2 ♀♀ paratypes (cl 2.54, 2.73 mm) (MNHN-Na 15618).

TYPE LOCALITY. — French Polynesia (Marquesas Is), 100-110 m depth.

ETYMOLOGY. — It is a pleasure to dedicate this species to Alain Crosnier in recognition of his great contribution to the carcinological fauna of the Indo-Pacific region, and his help to my shrimp research.

DISTRIBUTION. — Only known from type locality in Marquesas Islands in French Polynesia ; 100-110 m depth.

DESCRIPTION

A small sized pontoniine shrimp of slightly depressed and robust body form.

Carapace glabrous, slightly depressed. Rostrum unarmed, nearly horizontal, slightly overreaching distal end of distal segment of antennular peduncle, 0.57-0.70 times as long as carapace; distal half laterally compressed, dorsal and ventral margins unarmed, dorsal margin slightly sinuous, with base above orbital margin slightly convex and subapically slightly concave, tip acute, anterodorsally pointed; lateral carinae well developed, strongly expanded laterally on proximal half of rostral length, forming supraocular eave extending posteriorly on carapace to about anterior third of carapace length, covering most of eyestalk, eave unarmed, anterior margin oblique, anterolateral angle broadly rounded. Carapace armed only with long slender acute antennal spine, without epigastric, supraorbital, hepatic, or branchiostegal spines; antennal spine with developed antennal carina posteriorly, extending posteriorly on carapace to about anterior fourth of carapace length; area between supraocular eave and antennal carina hollowed, forming deeply concave orbital depression, orbit deeper and broader anteriorly than posteriorly, extending posteriorly to about anterior half of carapace; antennal groove distinct, extending posteriorly from anterior margin of carapace below antennal spine to about anterior fourth of carapace length. Pterygostomian margin produced as distinct pterygostomian lobe curving outward anteriorly, with distinct creased line at base of lobe. Anteroventral angle rounded.

Fourth to eighth thoracic sternites broad, unarmed, posterior margin of fourth thoracic sternite with low transverse carina.

Abdominal somites glabrous, pleura of first 3 somites rounded, pleura of fourth and fifth somites truncate rounded posterolaterally; sixth somite short, about 0.35 of carapace length, 1.3 times longer than high, 1.4 times as long as fifth, posterolateral and posteroventral angles truncate rounded.Telson about 1.7 times as long as sixth somite, 2.4 times longer than anterior width, anterior margin about 2.7 times wider than posterior margin, with 2 pairs of small dorsolateral spines marginally at 0.6 and 0.9 of telson length; posterior margin rounded, with 3 pairs of terminal spines (holotype with 3 submedian and 1 intermediate spines), lateral pair is similar to dorsolateral spines, intermediate pair slightly longer and stouter than others, submedian pair very slender, not setose.

Eye well developed, slightly compressed, cornea hemispherical, obliquely jointed with stalk, diameter about 0.2 of carapace length, stalk without anterodorsal tubercle, width subequal to corneal diameter, dorsal length about 0.7 of corneal length.

Antennular peduncle robust, extending to near tip of rostrum. Proximal segment with medial length about 0.25 of carapace length, 1.4 times longer than central width, with slender acute stylocerite laterally, extending to near 0.6 of medial length; anterolateral margin broadly produced, non-setose, with strong stout acute anterolateral tooth distinctly exceeding anterior margin of intermediate segment; ventromedial tooth absent; statocyst normally developed. Intermediate segment short, dorsal length about 0.2 of proximal segment length, 0.5 times shorter than distal width, lateral margin expanded, with broad, setose lateral lobe. Distal segment about 0.5 of proximal segment length, 1.1 times longer than distal width; upper flagellum biramous, 6 proximal segments fused, fused portion subequal to proximal segment, shorter free ramus with only 2 segments, with about 12 groups of aesthetascs, longer free ramus slender, filiform, with about 12 segments; lower flagellum slender, filiform, with more than 25 segments.

Antenna with basicerite unarmed ventrolaterally; scaphocerite well developed, broad, far overreaching tip of rostrum, about 0.55 times as long as carapace, 1.7 times longer than maximum width, distal margin strongly produced, rounded, far overreaching distolateral tooth, lateral margin distinctly convex, with stout acute distolateral tooth; carpocerite about 0.4 of scaphocerite length, 2.3 times longer than wide; flagellum well developed, slender, longer than 2.2 times as long as carapace length.

Mouthparts similar to those of Izucaris masudai Okuno, 1999 . Mandible without palp; molar process normal, with four strong teeth, upper inner tooth low; incisor process truncate distally with three stout acute teeth, central tooth smaller than outer teeth. Maxillula with broad upper lacinia, bearing strong spiniform setae and simple setae marginally; lower lacinia with several strong spiniform setae distally, sparse slender simple setae on posterior margin; palp distinctly bilobed, anterior lobe curved, without seta distally. Maxilla with short, stout, slightly tapered distally, curved medially non-setose palp; endites obsolete; scaphognathite well developed, broad, about three times as long as its central width. First maxilliped with short, stout, non-setose palp, medial margin slightly sinuous; basal endite large, broad, with marginal setae; exopodal flagellum absent, caridean lobe large, oval, with plumose marginal setae; epipod large, bilobed. Second maxilliped without exopodal flagellum; dactylar segment broad with dense serrulate spines and simple setae medially, medial margin slightly concave, not deeply emarginate; propodal segment with spiniform setae and sparse simple setae distomedially; carpal segment with lower angle produced, rounded; epipod large, broad; without podobranch. Third maxilliped without exopod; endopod robust, ischiomerus and basis completely fused, with basal portion convex medially, combined segment about 0.4 of carapace length, 4.7 times longer than central width, with sparse setae along medial margin; penultimate segment about 0.25 of combined segment length, 1.5 times longer than wide, with several spiniform setae medially and 1 distolateral spiniform seta; terminal segment about third of fused segments length, distally tapering, 3.3 times longer than proximal width, with long spiniform setae distally and medially; epipod subrectangular; with small arthrobranch.

Pereiopods robust. First pereiopod, overreaching level of distal end of scaphocerite by chela and most of carpus; chela about 0.44 times as long as carapace, palm slightly depressed, 2.9 times longer than wide, with 5 or 6 transverse rows of short cleaning setae on proximal fifth of ventral margin, fingers about 0.7 of palm length, tips hooked, with sparse simple distal setae, cutting edges nearly straight, entire, dactyl tapering distally, about 4.8 times longer than proximal width; carpus subcylindrical, slightly tapering proximally, about 1.4 times as long as chela, 6.8 times longer than distal width, with a transverse row of distoventral cleaning setae; merus slightly compressed, subuniform, about 1.2 times as long as chela, 5.7 times longer than deep; ischium slightly compressed, about 0.8 of chela length, 3.1 times longer than distal depth; base and coxa without special features.

Second pereiopods strongly dissimilar and unequal. Left major pereiopod large and robust, overreaching carpocerite by chela, overreaching distal end of scaphocerite by fingers and distal half palm; chela large, robust and long, palm subcylindrical, subuniform, about 0.8 times as long as carapace, 3.3 times longer than proximal depth, covered with fine setae; fingers with strongly hooked tips, dactyl broad flattened, curved medially, about 0.4 times as long as palm, 2.0 times longer than broad, dorsolateral margin oblique so that distal half tapers distally to hooked tip, lateral surface with fine setae, cutting edge bearing four truncate teeth, distal second teeth large, proximal second teeth smaller than distal second teeth, proximal and distal teeth low and small; fixed finger tapered distally to hooked tip, proximal expanded, with a deep proximal cavity on cutting margin to fill the base of dactyl, cutting edge with about seven small low teeth; carpus cuplike, widening distally, about 0.2 as long as palm, 0.7 times shorter than distal depth; merus slightly compressed, about half of palm length, 2.4 times longer than proximal depth, unarmed; ischium slightly compressed, slightly tapered proximally, about 0.4 of palm length, 2.0 times longer than distal depth; base and coxa without special features. Right minor pereiopod shorter and more slender than major, overreaching distal end of scaphocerite by finger and distal fifth of palm; chela covered by long fine setae, palm slightly compressed, subuniform, about 0.45 times as long as carapace, 2.7 times longer than wide; fingers with acute hooked tips, covered with setae, with long and curved subapical setae, cutting edges nearly straight, with very small acute teeth; carpus cup-like, about 0.4 as long as palm, 1.3 times longer than distal depth; merus slightly compressed, subequal to palm in length, about 3.0 times longer than proximal depth, unarmed; ischium slightly compressed, slightly tapered proximally, about 0.9 of palm length, 2.6 times longer than distal depth; base and coxa without special features.

Ambulatory pereiopods robust. Third pereiopod extending to distal end of scaphocerite; dactyl simple, hooked, dorsal margin length about third of propod, 2.5 times longer than proximal depth, dorsal margin evenly convex, ventral margin sinuous on proximal half, slightly concave on distal half, unguis distinct; propod slightly compressed, about half of carapace length, 4.7 times longer than proximal depth, with long and curved distoventral and distodorsal setae, without spines; carpus tapered proximally, about 0.4 of propod length, 1.7 times longer than distal depth, distodorsal lobe produced distinctly; merus with distal third depressed, gradually compressed proximally, about 0.9 of propod length, 2.8 times longer than central depth, unarmed; ischium tapered proximally, slightly compressed, about 0.6 of propod length, 2.0 times longer than distal depth; base and coxa normal. Fourth and fifth pereiopods similar to third, fourth pereiopod propod subequal to third, fifth pereiopod propod 1.1 times longer than third, fifth pereiopod exceeding anteroventral angle of carapace.

Uropod distinctly exceeding distal end of telson; protopodite with posterolateral angle short, rounded; exopod about 0.65 of carapace length, 2.0 times longer than central width, lateral margin feebly convex, with acute movable spine distally, without distal tooth; diaeresis distinct; endopod 0.9 times as long as exopod, 2.4 times longer than central width.

Egg number more than 60, size moderate, maximum length 0.44 mm.

Coloration

Based on the photograph ( Fig. 5A ) of a paratype (MNHN-Na 15617) provided by J. Poupin.

Shrimp body pink, with long longitudinal brownish stripes on rostrum and dorsal surfaces of carapace and abdomen, and short traverse or oblique brown to brown-yellowish stripes on lateral surfaces of carapace and abdomen, and surfaces of pereiopods.

REMARKS

Izucaris crosnieri n. sp. is the second species of the genus Izucaris . It is very similar to the other species of the genus, I. masudai but can be easily distinguished from the latter by the major second pereiopod chela, with a strongly broadened and flattened dactylus medially curved; the anterior dorsolateral pair of telson spines situated at about 0.6 of the telson length, distinctly posterior to the midlength of the telson (vs. at midlength in I. masudai ); the distolateral spine of proximal antennular peduncle segment distinctly exceeding the anterior margin of the intermediate segment (vs. not extending to the margin in I. masudai ); the cutting edges of the first pereiopod fingers entire (vs. bearing blunt teeth in I. masudai ). Izucaris crosnieri n. sp. also resembles the species of the genus Pontonides Borradaile, 1917 , from which it can be separated by the long and distally compressed rostrum, and the normal, not deeply emarginate medial margin of the dactylar segment of the second maxilliped.

The peculiar major second pereiopod of I. crosnieri n. sp. looks somewhat like that of Periclimenes platydactylus n. sp. (see below), but its dactyl is shorter and broader than that of the latter.

The collection position and depth of this new species extend the geographic range of the genus Izucaris to French Polynesia, and its bathymetric range to 100- 110 m. The only other species of the genus, Izucaris masudai , was recorded from the Izu Peninsula, Honshu, Japan, from 20- 27 m.

Figures

FIG. 1. — Izucaris crosnieri n. sp., holotype ovig. ♀ (cl 3.10 mm) (MNHN-Na 15616), body, lateral view. Scale bar: 1 mm.

FIG. 2. — Izucaris crosnieri n. sp.: A-D, F-I, holotype ovig. ♀ (cl 3.10 mm) (MNHN-Na 15616); E, paratype ♀ (cl 3.41 mm) (MNHN-Na 15617); A, rostrum and carapace, lateral view; B, anterior carapace and appendages, dorsal view; C, tailfan, dorsal view; D, E, tip of telson; F, right eye, dorsal view; G, right antennule, dorsal view; H, right antenna, ventral view; I, right uropod.Scale bars: A, B, 1 mm; C, F-I, 0.5 mm; D, E, 0.25 mm.

FIG. 3. — Izucaris crosnieri n. sp., holotype ovig. ♀ (cl 3.10 mm) (MNHN-Na 15616): A, mandible; B, maxillula; C, maxilla; D, first maxilliped; E, second maxilliped; F, third maxilliped. Scale bars: 0.5 mm.

FIG. 4. — Izucaris crosnieri n. sp., holotype ovig. ♀ (cl 3.10 mm) (MNHN-Na 15616): A, right first pereiopod, lateral view; B, same, chela, dorsal view; C, major (left) second pereiopod, lateral view; D, same, fingers, lateroventral view; E, same, medial view; F, minor (right) second pereiopod, lateral view; G, same, chela, dorsal view; H, left third pereiopod, lateral view; I, right third pereiopod, dactyl and distal part of propod, lateral view. Scale bars: A, C, F, H, 1.0 mm; B, D, E, G, 0.5 mm; I, 0.25 mm.

FIG. 5. — A, Izucaris crosnieri n. sp., paratype ♀ (cl 3.41 mm) (MNHN-Na 15617); B, Periclimenes aleator, Bruce,1991,ovig. ♀ (MNHN- Na 15982) (provided by J. Poupin).