Periclimenes platydactylus, Li, 2008

Li, Xinzheng, 2008, Report on some species of Palaemonidae (Crustacea, Decapoda) from French Polynesia, Zoosystema 30 (1), pp. 203-252 : 231-236

Periclimenes platydactylus n. sp.

( Figs 16-19 )

TYPE MATERIAL. — Marquesas Is. Nuku Hiva, MUS- ORSTOM 9, stn CP 1177, 8°45.1’S, 140°15.1’W, 108-112 m, 25.VIII.1997, ovig. ♀, holotype (cl 1.80 mm) (MNHN-Na 15609).

TYPE LOCALITY. — French Polynesia (Marquesas Is ); 108-112 m depth .

ETYMOLOGY. — “Platys”, Greek for flat, broad; “daktylos”, Greek for finger. The specific name is in reference to the dactyl of the second pereiopod having the lateral flange strongly expanded so that the dactyl looks broad and lamellar.

DISTRIBUTION. — Only known from type locality.

DESCRIPTION

A small sized pontoniine shrimp of subcylindrical body form.

Carapace smooth, glabrous. Rostrum well developed, compressed, shallow, horizontal, straight, extending to distal margin of scaphocerite, about 1.3 times carapace length; dorsal margin near straight, with 8 acute teeth, evenly distributed along whole length, subequal with exception of the anteriormost tooth smaller, posteriormost tooth at level just above orbital margin; lateral carinae distinct; ventral margin with basal half nearly straight, with 3 acute teeth on distal half, anteriormost ventral tooth just before second distal dorsal tooth; interdental spaces setose, proximal ventral carina non-setose. Supraorbital and epigastric spines absent; orbit feebly developed, inferior orbital angle produced, tip rounded; antennal spine acute, marginal, just below to inferior orbital angle, distinctly overreaching tip of inferior orbital angle; hepatic spine as well developed as antennal spine, slender, slightly below the level of antennal spine, posterior to level of posteriormost dorsal rostral tooth; anterolateral angle of carapace rounded.

Abdominal segments smooth, glabrous; third segment with tergum normal, without dorsally compressed process; sixth segment 0.72 of carapace length, 2.24 times of fifth segment length, 2.09 times longer than deep, posterolateral angle produced, acute, posteroventral angles rounded; pleura of first 3 segment broadly rounded, fourth and fifth posteriorly produced, posterolateral angles bluntly rounded. Telson 1.23 times sixth segment length, 4.09 times longer than anterior width, with 2 pairs of small dorsolateral spines at 0.51 and 0.79 of telson length, spines about 0.06 of telson length; posterior margin produced postero-medially, without acute posterior median point, with 3 pairs of posterior spines, lateral spines small, similar to dorsolateral spines, intermediate spines long, robust, about 0.19 of telson length, submedian spines slender, nude, about 0.09 of telson length.

Eye well developed, with globular cornea, diameter of cornea 0.26 of posterior orbital carapace length, without accessory pigment spot; stalk robust, width similar to corneal diameter, length 1.17 times as long as corneal diameter.

Antennular peduncle extending to level between distal first and second dorsal rostral teeth; proximal segment depressed, medial margin length 0.52 times as long as carapace, 2.09 times longer than its central width, lateral margin straight, with long slender acute distolateral tooth, reaching beyond level of produced anterolateral margin, anterior margin with a transverse row of short plumose setae, anterolateral margin with 4 plumose setae, medial margin straight, with small hooked ventromedial tooth at about 0.47 of medial margin length; stylocerite acute, extending to 0.54 of medial margin length; intermediate

Li X.

segment slightly depressed, dorsal length 0.28 of medial margin length of proximal segment, 1.07 times longer than maximum width, lateral margin slightly expanded laterally, with 4 plumose setae; distal segment cylindrical, 0.36 times as long as medial margin length of proximal segment, 1.70 times longer than distal width; upper flagellum biramous, with 3 proximal segments fused, shorter free ramus with 5 segments, 1.62 times of fused portion length, total length of shorter free ramus and proximal fused portion about 0.42 of carapace length, with 5 groups of aesthetascs; longer ramus slender, filiform, more than 1.2 times of carapace length; lower flagellum slender, filiform, about as long as carapace length.

Antennal basicerite robust, with small acute lateral tooth; scaphocerite well developed, extending near tip of rostrum, 0.93 times as long as carapace length, 3.33 times longer than wide, distal margin strongly produced, rounded, distinctly overreaching distolateral tooth, lateral margin feebly concave, with strong acute distolateral tooth; carpocerite extending to 0.45 of scaphocerite length, 4.61 times longer than wide; flagellum well developed, slender, more than 3.6 times of postorbital carapace length.

Epistome unarmed. Fourth thoracic sternites unarmed; posterior sternites narrow.

Mouthparts typical of the genus.Mandible without palp; molar process normal, with four strong blunt teeth; incisor process obliquely truncate distally with three stout acute teeth, central tooth smaller than outer teeth. Maxillula normal. Maxilla with short simple non-setose palp; basal endite bilobed distally, upper lobe stouter than lower, with simple setae distally; scaphognathite well developed, about 3.34 times longer than central width. First maxilliped normal. Second maxilliped with normal endopod, dactylar segment about 2.33 times longer than broad, with numerous serrulate spines medially; propodal segment broad, distal margin with several long serrulate spiniform setae; exopod with 2 long setae distally; without podobranch. Third maxilliped with endopod extending near to tip of carpocerite, ischiomerus and basis almost completely fused, combined segment 0.41 times of carapace length, 4.78 as long as proximal width ischiomerus, setose medially; penultimate segment about 0.52 of combined segment length, 3.39 times longer than proximal width, with 5 long and robust setae medially; terminal segment about 0.40 of combined segment length, slightly tapering distally, 4.52 times longer than proximal width, with short and robust setae medially, tip with 3 setae; exopod slender, extending to 0.93 of combined segment length, with 4 fine setae distally; coxa with oval lateral plate and small arthrobranch.

Pereiopods slender. First pereiopods extending to distal end of scaphocerite; chela slender, 0.41 of carapace length, palm subcylindrical, 4.44 times as long as wide, with several long setae, ventral margin with 5 transverse rows of short cleaning setae on proximal 0.4 of length; fingers 0.57 times of palm length, slender, base slightly expanded, tapered distally, surrounded with several setae on outer surface, cutting edges sharp, entire, tips strongly hooked; carpus elongate, slightly swollen distally, 1.10 times of chela length, 6.61 times longer than distal width, with a row of serrulate cleaning setae distoventrally corresponding those on palm; merus 1.32 times of chela length, 7.34 times longer than distal depth; ischium 0.70 of chela length, 4.43 times longer than distal depth; basis and coxa without special features.

Second pereiopods sub-symmetrical, slender, smooth, glabrous, exceeding carpocerite by chela, carpus and distal fourth of merus. Major (right) second pereiopod with chela 1.14 of carapace length, palm subcylindrical, subuniform, 7.16 times longer than maximum width at proximal third of palm length, with sparse setae; dactyl 0.40 of palm length, 3.31 times longer than maximum depth at about 0.6 of dactylar length, with strongly developed lateral flange so that the dactyl looks lamellar, tip strongly hooked, with cluster of long subdistal setae, cutting edges sharp, with 2 small teeth at 0.24 and 0.39 of dactylar length; fixed finger somewhat robust, slightly tapering distally, 5.10 times longer than proximal depth, without lateral flange, tip strongly hooked, with cluster of long subdistal setae, cutting edge sharp, with 2 teeth at 0.34 and 0.47 of fixed finger length larger than dactylar teeth, with proximal excavation present to fit proximal part of dactyl cutting edge; carpus cup-like, 0.22 times of chela length, 1.82 times longer than distal width; merus slightly compressed, 0.64 of chela length, 5.87 distal depth, unarmed distoventrally; ischium slightly compressed, 0.35 times of chela length, 4.30 times distal depth; basis and coxa normal. Minor (left) second pereiopod similar to major, very slightly smaller than major.

Ambulatory pereiopods slender. Third pereiopod exceeding carpocerite by dactyl and propod, overreaching distal end of scaphocerite by dactyl and distal third of propod; dactyl elongate, slender, compressed, 0.24 of propod length, 5.32 times longer than basal depth, unguis indistinct, very slender and elongate, ventral margin evenly concave, corpus with ventral margin near straight, distal accessory tooth minute in left third pereiopod, wanted or absent in right third pereiopod and other ambulatory pereiopods; propod compressed, subuniform, 0.76 of carapace length, 10.59 times longer than deep, with pair of long slender simple distoventral spines, spines 0.07 of propod length, extending proximal 0.31 of dactyl length, distal end of propod with ventrolateral, ventromedial and dorsal cluster of long curved setae, ventral margin of propod with four single spines distributed at 0.10, 0.22, 0.41 and 0.71 of propod length, of which, distal three similar to or slightly shorter than distoventral spines, proximal ventral spine much shorter than distoventral spines, several long curved setae along whole length of ventral and dorsal margins; carpus subcylindrical, tapered proximally, 0.37 of propod length, 3.78 times longer than distal depth, with distinct distodorsal lobe; merus slightly compressed, 0.94 of propod length, 8.60 times longer than distal depth, subuniform, unarmed; ischium slightly tapered proximally, 0.43 of propod length, 4.81 times longer than distal depth; basis and coxa without special features.Fourth and fifth pereiopods similar to third, fourth propod 1.04, fifth propod 1.08 times as long as third propod; fifth exceeds carpocerite by dactyl and distal 0.60 of propod.

Uropod distinctly exceeding telson. Protopodite with posterolateral angle short, rounded; exopod 0.80 times as long as carapace length, 3.16 times longer than central width, lateral border slightly convex, with very small acute distal tooth and large mobile spine medially, diaeresis distinct; endopod narrow, 0.92 of exopod length, 3.53 times longer than wide.

Egg with maximum length 0.41 mm, egg number about 18.

REMARKS

The systematic position of Periclimenes platydactylus n. sp. whitin the genus is not clear.Its lamellar dactyl of the second pereiopod, which is about 0.40 of the length of the palm, the rostral formula of 1+7/3 with the posteriormost tooth situated above the orbital margin, distinctly anterior to the level of hepatic spine, the simple chela of the first pereiopod, biunguiculate ambulatory dactyls in which the accessory tooth is minute, may differentiate the new species from most others of the genus Periclimenes . The well developed lateral dactylar flange of the second pereiopod of the new species are similar to those of the P. alcocki group, but the new species can be distinguished from all the members of that group by the combined features of only two pairs of dorsolateral telson spines, the minute accessory tooth of ambulatory dactyl, the posteriormost tooth of dorsal rostral series situated above the orbital margin, and the shallower bathymetric range of 108-112 m (the P. alcocki group is usually found at more than 200 m depth).

Figures

FIG. 16. — Periclimenes platydactylus n. sp., holotype ovig. ♀ (cl 1.80 mm) (MNHN-Na 15609), body, lateral view. Scale bar: 1 mm.

FIG. 17. — Periclimenes platydactylus n. sp., holotype ovig. ♀ (cl 1.80 mm) (MNHN-Na 15609): A, rostrum and anterior carapace; B, telson; C, eye; D, antennule; E, antenna; F, uropod. Scale bars: 0.5 mm.

FIG. 18.— Periclimenes platydactylus n. sp.,holotype ovig.♀ (cl 1.80 mm) (MNHN-Na 15609):A, mandible;B, maxilla;C, first maxilliped; D, second maxilliped; E, third maxilliped. Scale bars: 0.5 mm.

FIG. 19. — Periclimenes platydactylus n. sp., holotype ovig. ♀ (cl 1.80 mm) (MNHN-Na 15609): A, first pereiopod; B, same, chela; C, major (right) second pereiopod; D, same, chela; E, minor (left) second pereiopod; F, left third pereiopod; G, right third pereiopod, dactyl and distal part of propod. Scale bars: A-F, 0.5 mm; G, 0.25 mm.