Periclimenes alexanderi, Li, 2008

Li, Xinzheng, 2008, Report on some species of Palaemonidae (Crustacea, Decapoda) from French Polynesia, Zoosystema 30 (1), pp. 203-252 : 219-224

Periclimenes alexanderi n. sp.

( Figs 7-10 )

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, holotype ♂ (cl 2.15 mm) ; paratypes, ♂ (cl 1.91 mm), ♀ (cl 1.74 mm) (MNHN-Na 15611) .

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

ETYMOLOGY. — The specific name is given in honour of Alexander J. Bruce, who has given the biggest contribution to research of Pontoniinae over the past 50 years.

DISTRIBUTION. — Only known from the type locality.

DESCRIPTION

A small sized pontoniine shrimp of subcylindrical and robust body form.

Carapace smooth, glabrous. Rostrum well developed, anteroventrad, equal to 0.78-0.87 carapace length, reaching to near distal end of third segment of antennular peduncle, deep, extending distinctly anteroventrally, distally acute, up-curved; dorsal margin convex, with 6 or 8 acute teeth, posteriormost tooth just over or slightly posterior to orbital margin; lateral carina conspicuous, markedly thickened; ventral carina distinct, ventral margin slightly concave to straight in about proximal 0.80 of rostral length, strongly upcurved in distal 0.20 so that distal margin is distinctly convex, with single small acute tooth at 0.80 of rostrum length, dorsal interdental spaces setose, ventral margin of carina setose proximally to tooth. Supraorbital and epigastric spines absent, obscure epigastric tubercle present; orbit developed; inferior orbital angle distinctly produced, blunt, broad; antennal spine small, slender, somewhat submarginal, extending to tip of inferior orbital angle; hepatic spine small, slender, similar to antennal, at distinct lower level to antennal spine, slightly posterior to level of first dorsal rostral tooth; anterolateral angle of carapace not produced, bluntly angular.

Abdominal segments smooth, glabrous; third segment not posterodorsally produced; fifth segment 0.50-0.62 of sixth segment length, sixth segment 0.56-0.61 of carapace length, 1.50-1.70 times longer than deep, with posterolateral angle acute, posteroventral angle stout, less acute; pleura of first 3 segments enlarged, broadly rounded, fourth and fifth slightly produced posteriorly, rounded. Telson short and broad, 1.26-1.36 times sixth segment length, 3.43-3.81 times longer than anterior width, tapering posteriorly, lateral margin almost straight, posterior margin about 0.36 of anterior width, with projecting median point; two pairs of dorsal spines present at 0.55-0.62 and 0.74-0.85 of telson length, spines 0.05-0.06 of telson length; posterior margin with 3 pairs of spines, lateral spines small, similar to dorsal spines, intermediate spines well developed, robust, 0.15-0.16 of telson length, submedian spines 0.45-0.50 of intermediate spine length, slender.

Eye with large globular, well pigmented cornea, with distinct accessory pigment spot, oblique, diameter 0.31-0.33 of carapace length; stalk short and robust, slightly compressed, swollen anteroproximally and tapering anterodistally, posterior margin length 0.85-0.95 of corneal diameter, 0.91-1.05 as long as maximum width.

Antennular peduncle robust, slightly exceeding tip of rostrum; proximal segment 0.45-0.50 of carapace length, 1.70-1.85 times longer than central width, with slender acute stylocerite laterally, reaching to 0.50-0.60 of medial length; anterolateral margin broadly produced with large lobe, reaching to beyond middle of intermediate peduncular segment, anteriorly setose, with acute distolateral tooth extending far beyond anterolateral margin and near to level of proximal margin of distal peduncular segment; ventral medial border with small acute tooth proximally at 0.36-0.42 of length; statocyst normally developed, with granular statolith; intermediate segment short, dorsal length 0.25-0.34 of proximal segment length, 0.80-0.90 as long as wide, with broad, setose lateral lobe; distal segment 0.26- 0.34 of proximal segment length, 1.03-1.16 times longer than wide; upper flagellum biramous, 4 or 5 proximal segments fused, shorter free ramus with 2 to 4 segments only, total length of shorter ramus 0.56-0.68 of postorbital carapace length, with 9- 16 groups of aesthetascs, longer ramus with more than 12 free segments; lower flagellum very slender, 1.22-1.26 of postorbital carapace length.

Antennal basicerite with stout, acute lateral tooth; carpocerite short, about 0.23-0.26 of scaphocerite length, slightly compressed, very slightly tapering proximally, 1.65-1.88 of distal width, flagellum more than 4 four times carapace length; scaphocerite extending far beyond rostrum and antennular peduncle, 0.91-1.00 of carapace length, broad, 2.82-2.93 times longer than central width, lateral margin near straight, with stout distolateral tooth, distal margin broadly produced, rounded, exceeding distolateral tooth distinctly.

Epistome unarmed. Fourth thoracic sternite with low transverse ridge with median notch, fifth with similar stronger low transverse ridge; posterior sternites narrow.

Mouthpart generally typical of genus. Mandible normal, molar process normal, with strong blunt teeth; incisor process distally truncate, with 3 acute teeth, central tooth small, outer teeth unequal. Maxillula with feebly bilobed palp; upper lacinia slightly expanded, distal margin with 6-8 simple spines and numerous short setae; lower lacinia short, tapering, blunt, with numerous setae and slender distal spines. Maxilla with short, robust, non-setiferous palp, basal endite deeply bilobed, upper lobe larger, distally rounded with about 5-7 slender simple setae, lower lobe distally oblique, with about 4-6 setae; scaphognathite well developed, about 4.60 times longer than central width, posterior lobe large, anterior lobe narrower. First maxilliped with robust non-setiferous palp, basal endite large, broadly rounded, medial margin moderately setose, coxal endite obsolete; exopod large, triangular, deeply bilobed. Second maxilliped with endopod of normal form, dactylar segment with numerous serrulate spines medially, propodal segment with anteromedial margin strongly spinose; exopod slender, with 4 plumose distal setae; epipod subrectanular, without podobranch. Third maxilliped with endopod moderately robust, extending to about middle of carpocerite, ischiomerus and basis fused, combined segment about 0.43 of carapace length, about 5.94 times longer than central width, subuniform, bowed, compressed, medial margin with numerous slender setae; penultimate segment compressed to subcylindrical from proximal to distal, about 0.65 of proximal segment length, about 4.95 times longer than proximal width, with feebly grouped long slender setae medially; terminal segment subcylindrical, about 0.44 of proximal segment length, with long slender simple terminal spine, tapering distally, with about 6 transverse groups of serrulate spines ventromedially; exopod with slender flagellum with 7 plumose distal setae; coxa with small setose medial process, lateral plate small, rounded; arthrobranch small, with 2 small lamellae only.

First pereiopod moderately slender, extending anteriorly exceeding carpocerite by distal 0.67 to all carpus and chela, extending to or beyond distal margin of scaphocerite lamella by fingers.Chela with palm subcylindrical, slightly compressed, slightly tapering proximally, 0.23-0.25 of carapace length, 1.88-1.98 times longer than distal depth, with 4 or 5 transverse rows of short serrulate cleaning setae proximally; fingers subspatulate, 1.00-1.13 of palm length, tapering distally, dactyl 4.16-4.78 times longer than proximal width, without strongly hooked tip distally, cutting edges situated laterally, entire, laterally covered with several groups of long setae; carpus 1.54-2.06 times of palm length, robust, tapered proximally, 3.43-5.32 times longer than distal width, with several serrulate setae distally; merus 2.09-2.24 of palm length, subuniform, 5.72-6.46 times longer than central width; ischium robust, 1.09-1.19 of palm length, 3.16-3.24 times of distal width, ventral margin with subdistal setose carina; basis with ventral setose carina; coxa with large linguiform process ventrally.

Second pereiopods symmetrical, similar, equal or subequal. In males, major (when subequal) or both second pereiopods (when equal) exceeding carpocerite by chela, carpus and distal fourth to third of merus, exceeding scaphocerite by fingers and distal 1-2 thirds of palm, chela with palm subcylindrical, slightly compressed distally, with sparse tubercles each with single short apical seta, 0.74 to 1.02 of carapace length, 3.07-3.55 times longer than deep; fingers with strongly hooked tips, lateral surfaces with sparse tubercles and long curved setae, dactyl 0.51-0.64 of palm length, 3.96-4.20 times longer than proximal depth, distal 0.68 of cutting edge concave, entire, proximal 0.32 with 2 teeth, distal tooth strong, subacute, proximal tooth rounded, fixed finger with distal 0.60 of cutting edge convex, entire, proximal 0.40 with two teeth separated by diastema for distal dactylar tooth; carpus short and stout, cup-like, distally expanded, with very sparse tubercles, 0.27-0.35 of palm length, 1.19-1.27 times longer than distal width; merus with sparse tubercles, 0.64-0.71 of palm length, 3.43-3.58 times longer than central width, compressed proximally, distoventral margin plain, with distoventral lateral margins angulate; ischium 0.65-0.69 of palm length, 3.42-3.87 times longer than distal width, compressed, proximally tapered, with very sparse tubercles. Female with second pereiopods similar to but less strong than those of males, smooth, without tubercles, glabrous except fingers with long setae on lateral surfaces, exceeding carpocerite by chela, exceeding scaphocerite by fingers; palm 0.66 of carapace length.

Ambulatory pereiopods moderately robust. Third pereiopod exceeding scaphocerite by dactyl; dactyl biunguiculate, equal to about 0.25 of propod length; unguis about 0.62 of dorsal corpus length; corpus compressed, about 2.83 times longer than proximal depth, with acute distoventral tooth, 2 distolateral and 1 distomedial setae; propod slightly compressed, about 0.70 of carapace length, 8.52-11.10 times longer than central deep, with 2 pairs of spines distoventrally and 3-7 single ventral spines, and several simple setae; carpus 0.38-0.44 of propod length, unarmed, slightly tapered proximally, 3.42-3.96 times longer than distal width, with well marked distodorsal lobe; merus compressed, 0.89-0.91 of propod length, uniform, 5.50-6.60 times longer than central width, unarmed; ischium compressed, 0.44-0.48 of propod length, slightly tapered proximally, 3.03-3.42 times longer than distal width; basis and coxa without special features. Fourth and fifth pereiopods similar to third, fourth propod 1.03-1.05 times as long as third, fifth 1.04-1.12 times.

Uropod far overreaching telson, protopodite with posterolateral angle rounded; exopod 0.87-0.95 of carapace length, elongate, 3.03-3.37 times longer than wide, lateral margin feebly convex, with strong distolateral tooth and slender acute mobile spine medially, diaeresis distinct; endopod 0.85-0.88 of exopod length, 3.20-3.66 times longer than wide.

REMARKS

Periclimenes alexanderi n. sp. is most closely related to P. parvispinatus Bruce,1990 , and shares with the latter the following major morphological characteristics: rostrum with a deep lamina, dorsal teeth almost all situated on the rostrum proper, with one small ventral tooth, eye with globular cornea, first pereiopods without well developed pectinate cutting edges on the fingers, ambulatory pereiopods with simply biunguiculate dactyl. Periclimenes alexanderi n. sp. may be readily distinguished from P. parvispinatus by the presence of a distinct accessory pigment spot on eye. Other differences are that, in P. alexanderi n. sp., the anterior pair of dorsal telson spines are present posterior to the middle of the telson length, hepatic and antennal spines are not tiny, fingers of the first pereiopod are longer than the palm; in P. parvispinatus , the anterior pair of dorsal telson spines are present at the middle line of the telson length, posterior margin with a small central projection, hepatic and antennal spines are tiny, fingers of the first pereiopod are shorter than the palm.

Figures

FIG. 7. — Periclimenes alexanderi n. sp., holotype, ♂ (cl 2.15 mm) (MNHN-Na 15611), body, lateral view. Scale bar: 1 mm.

FIG. 8. — Periclimenes alexanderi n. sp.: A, C, paratype ♂ (cl 1.91 mm);B, D, E, holotype,♂ (cl 2.15 mm) (MNHN-Na 15611);A, carapace; B, C, telson; D, eye; E, uropod. Scale bars: A-C, E, 1 mm; D, 0.5 mm.

FIG. 9. — Periclimenes alexanderi n. sp.,holotype,♂ (cl 2.15 mm) (MNHN-Na 15611):A, antennule;B, antenna;C, mandible;D, maxillula; E, maxilla; F, first maxilliped; G, second maxilliped; H, third maxilliped. Scale bars: A, B, H, 1 mm; C-G, 0.5 mm.

FIG. 10. — Periclimenes alexanderi n. sp., holotype, ♂ (cl 2.15 mm) (MNHN-Na 15611): A, first pereiopod; B, same, chela; C, second pereiopod; D, same, chela; E, third pereiopod; F, same, dactyl and distal part of propod. Scale bars: A, C-E, 1 mm; B, 0.5 mm; F, 0.25 mm.