Periclimenes loyautensis, Li & Bruce, 2006

Li, Xinzheng & Bruce, Alexander J., 2006, Further Indo-West Pacific palaemonoid shrimps (Crustacea: Decapoda: Palaemonoidea), principally from the New Caledonian region, Journal of Natural History 40 (11 - 12), pp. 611-738 : 700-703

Periclimenes loyautensis sp. nov.

( Figure 24 )

Material examined

Loyalty Islands: MUSORSTOM 6, stn CP464, 21 ° 02.309S, 167 ° 31.609E, 430 m, coll. B. Richer de Forges , 21 February 1989, 1 ovig. ♀ holotype (MNHN-Na 14947) .

Description

A medium size, robust pontoniine shrimp of subcylindrical body form; lacking right second (major?), fifth and left third pereiopods, left second (minor?) pereiopod detached.

Carapace smooth, glabrous. Rostrum well developed, moderately deep, compressed, extending well beyond antennular peduncle, about 0.66 of carapace length, not reaching distal scaphocerite, anteroventrad except the anterad tip; dorsal carina deep, with seven subequal acute teeth along all length, proximal three more closely grouped than distal teeth, first tooth situated just posterior to posterior orbital margin; lateral carinae feebly developed, slightly upcurved distally and extending posteriorly on carapace posterodorsally; ventral carina feebly developed, with three low acute teeth on distal half margin, smaller than dorsal teeth; interdental spaces and proximal ventral carina feebly setose. Supraorbital spine absent; epigastric spine situated at anterior 0.3 of the carapace length, with basal suture; orbit feebly developed, inferior orbital angle strongly produced, round; antennal spine small slender marginal, distinct below the inferior orbital angle, not exceeding inferior orbital angle; hepatic spine larger than antennal one, slender, very slightly lower than, almost at same level of antennal spine, below between the epigastric spine and the first dorsal rostral tooth and closer to first dorsal rostral spine in lateral view; anterolateral angle of carapace not produced, bluntly rounded.

Abdominal segments smooth, glabrous; third abdominal segment not produced, noncarinate; pleura of first three segments broadly rounded, fourth and fifth posteriorly produced rounded, sixth segment about 1.8 times length of fifth, subcylindrical, about 1.73 times longer than deep, subuniform, posterolateral angle acute, posteroventral angle rounded. Telson about 1.53 times sixth segment length, about 3.7 times longer than anterior width, lateral margins with posterior two-thirds straight, convergent, posterior margin about 0.32 of anterior margin width, rounded, without posterior median point; dorsal surface with four pairs of small but well-developed dorsolateral spines at 0.4, 0.6, 0.75, and 0.9 of telson length, spines about 0.044 of telson length; posterior margin with three pairs of spines, lateral spines short, similar to dorsolateral spines, intermediate spines long, robust, about 0.12 of telson length, submedian spines slender, about 0.41 of intermediate spine length.

Eye small, with globular cornea, corneal diameter 0.13 of posterior orbital carapace length, without accessory pigment spot; stalk subequal to corneal diameter, subequal to corneal width, feebly compressed.

Antennular peduncle overreaching distal ventral rostral tooth; proximal segment about 2.0 times longer than central width, with slender acute stylocerite laterally, reaching to about 0.7 of segment length, anterolateral margin feebly produced, setose, with long slender acute lateral tooth reaching near to the end of dorsal margin of intermediate segment; statocyst small; medial margin setose, with ventromedial tooth at about 0.5 of length; intermediate segment with dorsal length about 0.3 of proximal segment length, 1.1 of width, lateral margin expanded, setose; distal segment about 0.43 times proximal segment length, slender, about 2.0 times longer than distal width; upper flagellum biramous, with 10 proximal segments of rami fused, shorter free ramus with five segments, length about 0.5 of fused portion, total length about 0.54 of carapace length, with about 23 groups of aesthetascs; longer ramus, slender, filiform, distal segments lost; lower flagellum slender, filiform, about 0.87 times carapace length.

Antennal basicerite robust, with acute distolateral tooth; carpocerite about 0.49 of length of lateral margin of scaphocerite, about 3.2 times longer than width, subcylindrical, reaching about 0.41 of total length of scaphocerite; flagellum well developed, slender, about 2.2 times postorbital carapace length; scaphocerite well developed, distinctly exceeding tip of rostrum, broad, about 2.5 times longer than wide, greatest width at about 0.4 of length, distal margin bluntly rounded, distinctly exceeding distolateral tooth, lateral margin nearly straight, with strong acute distolateral tooth.

Epistome unarmed. Fourth thoracic sternite without slender median process; posterior sternites unarmed.

Mouthparts mainly undissected. Mandible without palp; incisor process distally with three (right) or four (left) stout acute teeth, central teeth smaller than outer teeth. Third maxilliped with slender endopod, extending distally to three-quarters length of carpocerite, ischiomerus and basis incompletely fused, basal portion medially expanded, convex, combined segment compressed, setose medially; intermediate segment about 0.43 of combined proximal segment length, with several groups of long finely serrulate spiniform setae medially; terminal segment about 0.33 of combined proximal segment length, distally tapering, with seven transverse groups of spiniform setae ventromedially, with long distal spiniform setae; exopod with slender flagellum extending to the distal end of ischiomerus, with eight to nine plumose setae distally; arthrobranch distinct.

First pereiopods moderately slender, exceeding tip of rostrum by length of chela; chela with palm subcylindrical, slightly compressed, about 2.33 times longer than maximal depth, at about proximal 0.3 of length with several tranverse rows of short cleaning setae proximoventrally; fingers 0.83 of palm length, slender, tapering, cutting edges sharp, entire, tips hooked, base slightly expanded, surrounded by palisade of long setae medially and laterally at about 0.3, 0.7 and subterminally of fingers; carpus about 1.22 of chela length, 5.4 times longer than distal width, subuniform, with seven to eight serrulate cleaning subdistal setae ventrally; merus about 1.4 times chela length, 7.0 times longer than distal width; ichium 0.78 of chela length, 4.5 times longer than distal width, not strongly carinate distoventrally, obliquely articulated with basis.

Left (minor) second pereiopod well developed, exceeding carpocerite by carpus and chela; chela about 0.93 times postorbital carapace length; palm about 4.0 times longer than maximal depth, with very small tubercles; fingers about 0.7 of palm length, with strongly hooked tips, cutting edges entire, sharp, proximal 0.3 of fixed finger cutting edge with two teeth, proximal one larger and round, distal one smaller and acute, proximal 0.4 of dactyl cutting edge with two acute teeth, proximal one larger than distal; dactyl about 5.3 times longer than proximal depth, with feebly developed lateral flange; carpus cup-like, about 0.43 of palm length, 1.87 times distal width, with scattered small tubercles; merus about 0.9 of palm length, subequal to ischium, with tubercles ventrally; basis and coxa normal.

Ambulatory pereiopods slender. Third pereiopod exceeds carpocerite by dactyl, propod, and distal two-thirds of carpus; dactyl compressed, curved, about 0.18 of propod length, unguis distinct, about 0.61 of dorsal length of corpus, 3.7 times longer than proximal width; corpus about 2.5 times longer than proximal depth, dorsal margin feebly convex, non-setate, ventral margin straight, with acute distal accessory tooth, about 0.29 of unguis length, with two distolateral sensory setae; propod about 0.58 of carapace length, 13 times longer than maximum width, subuniform, with slender simple distoventral spine and five single spines distributed along ventral margin, and scattered long simple setae distally; carpus about 0.53 of propod length, 6.1 times longer than distal width, with distodorsal lobe, unarmed; merus subequal to propod length, 9.2 times longer than central width, uniform, unarmed; ischium subequal to carpus length, 0.52 of propod length, 4.9 times longer than distal width, slightly tapered proximally; basis and coxa without special features. Fourth and fifth pereiopods similar to third, fourth propod subequal, fifth propod 1.1 times third propod length; fifth exceeds carpocerite by dactyl and almost all propod.

Pleopods without special features.

Uropod distinctly exceeding distal end of intermediate posterior spine of telson; protopodite with posterolateral angle short, rounded; exopod 2.7 times longer than central width, lateral border distinctly convex, with small acute distal tooth, with large mobile spine medially, diaeresis distinct; endopod about 0.97 of exopod length, 3.6 times longer than wide.

Ova small, numerous, more than 400.

Measurements (mm)

Carapace length, 5.81; carapace and rostrum, 9.86; total body length (approximately), 26.6; second pereiopod chela, 5.46; length of ovum, 0.45.

Systematic position

Periclimenes loyautensis is very close to P. aleator Bruce, 1991 and other species of ‘‘ P. alcocki species group’’ which have more than two (usually four) pairs of dorsolateral telson spines, second pereiopods with lateral flange and covered with fine tubercles. It can be distinguished from P. aleator by the hepatic spine very slightly below the level of the antennal spine, at almost the same level, also the relatively more slender ambulatory pereiopods and longer uropods which overreach the distal end of intermediate posterior spine of telson. In P. aleator , the hepatic spine is distinctly lower than antennal spine, the ambulatory pereiopods are relatively robust, uropods reach to about middle of intermediate posterior spine of telson. Periclimenes loyautensis differs from P. alcocki Kemp, 1992 , by the larger cornea, the diameter is 0.13 of carapace length, and larger dorsolateral telson spines, about 0.044 of telson length, and the third pereiopod without transverse rows of setae distally, propod with well-developed spinulation, dactyl with longer and more slender accessory tooth. In latter species, the corneal diameter is about 0.1 or less of carapace length, the dorsolateral telson spines minute, and the posterior telson spines are also much shorter. Periclimenes loyautensis is also similar to P. crosnieri n. sp., the biunguiculate dactyl of ambulatory pereiopods easily distinguish it from that species, in which the ambulatory dactyl is simple.

Etymology

The specific name is given from its type locality, the Loyalty Islands .

Figures

Figure 24. Periclimenes loyautensis, new species, holotype ovigerous female (MNHN-Na 14947). (a) Carapace; (b) telson; (c) same, distal part; (d) eye, distal view; (e) minor second pereiopod; (f) same, fingers; (g) third pereiopod, propod and dactyl; (h) same, distal propod and dactyl.