Periclimenes paralcocki, 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 : 707-710

Periclimenes paralcocki sp. nov.

( Figure 27 )

Material examined

Tuvalu: MUSORSTOM 7, Banc Bayonnaise , stn CP631, 11 ° 549S, 179 ° 329W, 600 m, coll. 29 May 1992, 1♀ holotype (MNHN-Na 14865) .

Description

A large pontoniine shrimp of subcylindrical body form, very similar to Periclimenes alcocki Kemp, 1922 ; lacking right (major?) second pereiopod.

Carapace smooth, glabrous, with feeble dorsal hump on posterior two-fifths. Rostrum well developed, compressed, moderately deep, anteroventrad mostly and slightly upcurved apically, with feeble dorsal curvature, distinctly overreaching antennular peduncle, extending near to tip of scaphocerite, about 0.7 of carapace length; dorsal carina distinct, with seven large, acute teeth evenly distributed along dorsal margin, distal tooth much smaller than proximal teeth, first tooth situated on carapace just behind level of posterior orbital margin, with feeble basal suture; lateral carinae well developed, horizontal except up-curved distal part; ventral margin with three teeth on distal half between fifth and seventh dorsal teeth; interdental spaces and proximal ventral carina feebly setose. Supraorbital spine absent; epigastric spine situated at anterior 0.25 of carapace length, with basal suture; orbit feebly developed, inferior orbital angle produced, oval rounded; antennal spine small slender marginal, distinctly below inferior orbital angle, not exceeding inferior orbital angle; hepatic spine larger than antennal spine, slender, slightly lower than antennal spine, below the level between epigastric spine and first dorsal rostral tooth, remote from anterior carapace margin; 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 1.75 times length of fifth, subcylindrical, about 1.54 times longer than central depth, posterolateral angle acute, posteroventral angle rounded. Telson about 1.9 times sixth segment length, slender, about 4.3 times longer than anterior width, lateral margins sublinear, convergent, dorsal surface with three pairs of dorsolateral spines at 0.41, 0.73, and 0.87 of telson length, spines about 0.034 of telson length; posterior margin about 0.34 of anterior margin width, rounded, without acute posterior median point; posterior margin with normal three pairs of spines, lateral spines short, similar to dorsolateral spines, intermediate spines long, robust, about 0.067 of telson length, submedian spines about 0.45 of intermediate spine length, with sparse plumose setose.

Eye moderately reduced, with globular cornea, corneal diameter 0.125 of postorbital carapace length, without accessory pigment spot; stalk feebly compressed, subuniform, diameter subequal to cornea, length subequal to corneal diameter, subequal to dorsal width.

Antennular peduncle overreaching second ventral rostral tooth; proximal segment about 1.75 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 overreaching distodorsal end of intermediate segment; statocyst small; medial margin near straight, setose, with ventromedial tooth at about 0.5 of length; intermediate segment with dorsal length about 0.26 of proximal segment length, subequal to width, lateral margin expanded, setose; distal segment about 0.43 times proximal segment length, slender, about 1.77 times longer than distal width; upper flagellum biramous, with 11 proximal segments of rami fused, shorter free ramus with five segments, length about 0.4 of fused portion, total length about 0.48 of carapace length, with about 26 groups of aesthetascs; longer ramus slender, filiform, about 0.93 of carapace length; lower flagellum slender, filiform, about 0.93 times carapace length.

Antennal basicerite robust, with acute distolateral tooth; carpocerite subcylindrical, about 0.39 of scaphocerite length, 3.25 times longer than width; flagellum well developed, slender, about 3.5 times postorbital carapace length; scaphocerite well developed, distinctly exceeding distal end of antennular peduncle, slightly overreaching rostral tip, broad, about 2.37 times longer than wide, greatest width at about 0.3 of length, distal margin bluntly rounded, slightly exceeding the distolateral tooth, lateral margin feebly convex, with strong acute distolateral tooth.

Epistome unarmed. Fourth thoracic sternite without slender median process, with broad triangular plates, separated by deep median fissure, fifth sternite similar, subequal to those of fourth; 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 about 0.6 of carpocerite length, ischiomerus and basis fused incompletely, combined segment compressed, subuniform in ischiomerus portion and feebly produced medially in basal portion, setose medially, 5.4 times longer than central width; penultimate segment slightly compressed, about 0.53 of combined proximal segment length, with six groups of long finely spiniform setae medially; terminal segment about 0.37 of combined proximal segment length, 3.6 times longer than proximal width, distally tapering, with seven transverse groups of spiniform setae ventromedially, with long distal spiniform setae; exopod with slender flagellum just overreaching distal end of combined proximal segment, with nine plumose setae distally; coxa with small subacute setose medial process, rounded lateral plate, arthrobranch distinct.

First pereiopods moderately slender, extending slightly beyond distal margin of scaphocerite, exceeding carpocerite by chela and distal half carpus; chela with palm subcylindrical, slightly compressed, about 2.25 times longer than maximal depth, at about proximal 0.3 of length with six tranverse rows of short cleaning setae proximoventrally; fingers 0.86 of palm length, robust, tapering, subspatulate, surrounded by five groups of long setae medially and laterally along the fingers length, distal group shorter, cutting edges sharp, entire; carpus about 1.27 of chela length, 5.4 times longer than distal width, tapering proximally, with transverse row of serulate setae distoventrally; merus about 1.42 times chela length, 6.6 times longer than distal width, subuniform; ichium 0.64 of chela length, 2.7 times longer than distal width, feebly carinate distoventrally, obliquely articulated with basis; basis and coxa normal, no special feature.

Left (? minor) second pereiopod well developed, exceeding carpocerite by chela, carpus and distal sixth merus, scaphocerite by fingers and distal two-thirds of palm; chela subequal to postorbital carapace length; palm about 4.2 times longer than maximal depth, with very small tubercles; fingers about 0.6 of palm length, with strongly hooked tips, cutting edges entire, sharp, proximal 0.3 of fixed finger cutting edge with two small teeth, proximal one smaller, rounded, distal one larger, acute, proximal 0.4 of dactyl cutting edge with two small acute teeth, proximal tooth larger than distal; dactyl about 4.3 times longer than proximal depth, with feebly developed lateral flange; carpus cup-like, about 0.37 of palm length, 1.67 times distal width, with scattered small tubercles; merus about 0.8 of palm length, covered with scattered small tubercles; ischium 0.66 of palm length; basis and coxa normal.

Ambulatory pereiopods robust. Third pereiopod exceeds carpocerite by dactyl and propod, scaphocerite by dactyl; dactyl compressed, curved, about 0.15 of propod length, unguis distinct, about 0.54 of dorsal length of corpus, 4.2 times longer than proximal width; corpus about 2.38 times longer than proximal depth, dorsal margin feebly convex, non-setose, ventral margin largely straight, with acute distal accessory tooth, about 0.31 of unguis length, with short distolateral sensory setae; propod about 0.56 of carapace length, 9.3 times longer than maximum wide, subuniform, with pair of distovental spines and one pair of sub-distoventral spines, and three spines distributed along distal 0.6 of ventral margin, with row of long simple setae distolaterally, and group of long simple setae distodorsally, small groups of long simple setae along ventral and dorsal margins; carpus about 0.51 of propod length, 4.3 times longer than distal width, with long produced distodorsal lobe, unarmed; merus subequal to propod, 7.9 times longer than central width, uniform, unarmed; ischium 0.49 of propod length, 3.4 times longer than distal width, feebly tapered proximally; basis and coxa without special features. Fourth and fifth pereiopods similar to third, fourth propod subequal, fifth 1.09 times third propod length; fifth exceeds carpocerite by dactyl and distal one-third propod.

Pleopods without special features.

Uropod distinctly exceeding distal end of extended intermediate posterior spine of telson; protopodite with posterolateral angle short, rounded; exopod 2.59 times longer than central width, lateral border distinctly convex, with small acute distal tooth, and small mobile spine medially, diaeresis distinct; endopod about 0.93 of exopod length, 3.3 times longer than central width.

Measurements (mm)

Carapace length, 8.38; carapace and rostrum, 14.4; total body length (approximately), 40.0; left (? minor) second pereiopod chela, 8.23.

Systematic position

Periclimenes paralcocki n. sp. is very close to P. alcocki Kemp, 1922 . The telson with three pairs of dorsolateral spines distinguishes the new species from P. alcocki and other related species immediately. Most of the other P. alcocki allied species, which are distributed in deep water and with more than two pairs of dorsolateral telson spines, have four pairs of dorsolateral telson spines except P. albatrossae Chace and Bruce, 1993 , which has seven pairs of those spines. Periclimenes paralcocki can be distinguished from P. alcocki also by the relatively larger cornea, telson spines and accessory tooth of ambulatory pereiopod dactyl, and the rostrum distinctly reaching beyond the antennular peduncle, the flexor margin of ambulatory pereiopod propod is armed with spines and setae along the whole length. In P. alcocki , the rostrum does not exceed the antennular peduncle, the flexor margin of ambulatory pereiopod propod is unarmed except for the distal part. The number of dorsal telson spines of P. alcocki may show considerable variation ( Bruce 1996, p 230), so the corneal diameter, length of rostrum, length of dorsolateral telson spines, and armature of ambulatory propod should be used to distinguish the allied species in the Periclimenes alcocki species group as well as the number of dorsolateral telson spines.

Etymology

Para (Greek), near, and the specific name alcocki , referring to the close relationship between the two species.

Figures

Figure 27. Periclimenes paralcocki, new species, holotype ovigerous female (MNHN-Na 14865). (a) Carapace and anterior appendages; (b) anterior carapace; (c) eye, dorsal view; (d) antennular peduncle; (e) antenna; (f) left third pereiopod; (g) same, distal propod and dactyl; (h) telson; (i) same, distal part.