Periclimenes forgesi, 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 : 686-691

Periclimenes forgesi sp. nov.

( Figures 19 , 20 )

Material examined

New Caledonia: (i) BATHUS 3, stn CP846, 23 ° 02.909S, 166 ° 57.979E, 500–514 m, 1 December 1993, 1 ovig. ♀ holotype (MNHN-Na 14928); (ii) NORFOLK 1, Norfolk Ridge, stn CP1670, 23 ° 399S, 167 ° 599E, 382–386 m, Banc Jumeau-ouest, 21 June 2001, 1 ovig. ♀ paratype (MNHN-Na 15869) .

Description

A medium to large body size pontoniine shrimp of subcylindrical body form. Holotype with right scaphocerite, first, second, fourth and fifth pereiopods, most of telson except proximal part anterior to anterior pair of dorsolateral spines, uropod with distal part posterior to diaeresis lost; right third pereiopod and left fourth merus to dactyl detached; both hepatic spines and first three dorsal rostral teeth broken basally. Paratype with the tip of rostrum broken, right fourth, left fourth and fifth pereiopods lost; dactyl of left (major) second pereiopod lacking.

Holotype. Carapace smooth, glabrous. Rostrum short, slender, compressed, reaching to distodorsal end of second segment of antennular peduncle, about 0.42 of carapace length, feebly expanded laterally proximally, with feeble crest on proximal part and tapering distally; dorsal margin with seven small subequal acute teeth, more or less evenly distributed along whole length, second tooth situated just above posterior orbital margin; lateral carinae feebly developed; ventral margin straight, with one small acute tooth at distal 0.18 of rostral length, anterior to the distal dorsal tooth. Supraorbital spine absent, epigastric spine situated at anterior 0.21 of carapace length, distinctly smaller than dorsal rostral teeth; orbit feebly developed, inferior orbital angle produced, bluntly round; antennal spine small, slender, marginal, distinct below inferior orbital angle, not exceeding inferior orbital angle; hepatic spine feebly larger than antennal spine, small, slender, slightly below level of antennal spine, at level of first dorsal rostral tooth in lateral view; anterolateral angle of carapace not produced, bluntly rounded.

Abdominal segments smooth, glabrous; pleura of first three segments broadly rounded, fourth and fifth posteriorly produced, bluntly rounded; third segment without dorsal prominence; sixth segment about 1.7 times length of fifth, subcylindrical, about 1.75 times longer than deep, subuniform, posterolateral and posteroventral angles bluntly angulate.

Eye normally developed, cornea globular, well pigmented, diameter 0.16 of postorbital carapace length, without accessory pigment spot; stalk feebly compressed, feebly tapered proximally, 0.63 of corneal diameter and 0.74 of central width.

Antennular peduncle overreaching rostrum by third segment; proximal segment 1.85 times longer than central width, with slender acute stylocerite laterally, reaching to about 0.7 of segment length, anterolateral margin produced, setose, with long slender acute lateral tooth overreaching middle dorsal length of intermediate segment; statocyst small; medial margin straight, with plumose setose, ventromedial tooth minute, at about 0.5 of length. Intermediate segment obliquely articulated with distal segment, dorsal margin oblique proximolaterally, middle dorsal length about 0.26 of proximal segment length, 1.1 times width (not including lateral lobe), lateral margin expanded, with long robust plumose setae, medial margin similarly setose to lateral margin. Distal segment with mid-dorsal length 0.42 of proximal segment length, 1.4 times longer than distal width; upper flagellum biramous, with 10 proximal segments of rami fused, shorter free ramus with six segments, length about 0.64 of fused portion, total length about 0.53 of carapace length, with 22 groups of aesthetascs; longer ramus (free portion) slender, filiform, about 0.83 times carapace length; lower flagellum slender, filiform, subequal to carapace length.

Antennal basicerite robust, with acute distolateral tooth; carpocerite robust, 2.7 times longer than width, subcylindrical, reaching about 0.46 of total length of scaphocerite; scaphocerite well developed, exceeding antennular peduncle by distal third of lamella, broad, 2.5 times longer than wide, greatest width at about 0.4 of length, distal margin produced, bluntly rounded, distinctly overreaching distolateral tooth, lateral margin straight, with strong acute distolateral tooth.

Epistome unarmed. Fourth thoracic sternite without slender median process, with low transverse ridge with a median notch posteriorly; fifth thoracic sternite with similar ridge, posterior sternites unarmed.

Mouthparts typical of the genus. Mandible without palp; molar process normal, with four strong blunt teeth, lower inner tooth bilobed; incisor process robust, obliquely truncate distally with three (left) or four (right) stout teeth, central tooth smaller than outer teeth. Maxillula with palp bilobed, lower lobe shorter, acute tip with very short seta, upper lobe longer, with rounded tip; upper lacinia oval, with 10 spines distally and scattered setae; lower lacinia slender, tapered with numerous spiniform setae distally and simple setae on outer surface. Maxilla with short simple non-setose palp; basal endite deeply bilobed, upper lobe stouter than lower, with simple setae distally; coxal endite obsolete, medial margin convex; scaphognathite well developed, about 2.9 times longer than central width. First maxilliped with elongate slender palp, with short setulose preterminal seta; basal endite large, broad, setose medially; coxal endite distinct, convex; exopod with normal flagellum with four plumose distal setae and simple setae on distal half laterally; caridean lobe well developed, broad; epipod large, triangular, bilobed. Second maxilliped with normal endopod, dactylar segment about 3.5 times longer than broad, with numerous serrulate spines medially; propodal segment broad, with distal margin with long spiniform setae; carpus, ischiomerus and basis without special features; coxa angularly produced medially, with four to five simple setae; exopod with slender flagellum with eight to nine plumose setae distally; epipod simple, without podobrach. Third maxilliped with slender endopod, exceeding carpocerite by distal quarter of terminal segment; ischiomerus and basis incompletely fused, border indicated only by medial notch, basal portion feebly expanded medially, combined segment length about 6.0 times central width, compressed, setose medially, with submarginal row of very short small spines on proximal medial ischial portion; intermediate segment about 0.58 of combined proximal segment length, 6.0 times longer than central width, with six groups of long finely serrulate spiniform setae medially; terminal segment about 0.44 of combined proximal segment length, distally tapering, about 4.8 times longer than proximal width, with seven groups of spiniform setae medially, and long spiniform distal setae; exopod with slender flagellum with about 10 plumose setae distally; coxa feebly produced medially, with oval lateral plate; arthrobranch distinct.

First pereiopods moderately slender, exceeding carpocerite by chela and distal five-sixths carpus; chela with palm subcylindrical, slightly compressed, about 2.25 times longer than depth, with six tranverse rows of short cleaning setae proximoventrally; finger subequal to palm length, slender, tapering, cutting edges sharp, entire, tips hooked, surrounded by four groups of palisade setae medially and laterally on distal half, setae shorter distally; carpus about 0.93 of chela length, 5.45 times longer than distal width, tapering proximally, with one row two groups serrulate cleaning setae distoventrally, outer group with eight long setae, inner group with six short setae, about half as long as the long setae; merus about 1.2 times chela length, 7.0 times longer than central width; ichium 0.6 of chela length, 3.3 times longer than distal width, not strongly carinate distoventrally, obliquely articulated with basis; basis and coxa without special features.

Left (minor) second pereiopod well developed, exceeding carpocerite by chela, carpus and distal third of merus, rostrum by chela and carpus; chela about 0.95 times carapace length, palm subcylindrical, subuniform, with sparse small tubercles on medial (fixed finger side) surface, about 4.8 times longer than maximal depth, fingers about 0.6 of palm length, with stout hooked tips and feebly developed lateral flanges, fixed finger stouter than dactyl, with few scattered small tubercles on lateral surfaces similar to those of palm, cutting edge with distal 0.72 entire, small tooth on proximal 0.23 and small blunt rounded tooth in proximal pit; dactyl about 3.6 times longer than proximal depth, cutting edge with distal 0.64 entire, two small teeth and two notches on proximal 0.36, proximal tooth larger and triangular; carpus cup-like, about 0.34 of palm length, 1.76 times longer than distal width, feebly excavate distally, proximally tapered; merus about 0.83 of palm length, subuniform, about 5.5 times longer than distal depth, armed with sparse small tubercles on flexor margin, without distoventral tooth; ischium about 0.8 of palm length, subequal to merus length, 4.7 times longer than distal width, feebly compressed, slightly proximally tapered; basis and coxa normal.

Ambulatory pereiopods robust. Third pereiopod exceeds carpocerite by dactyl, propod, and distal three-quarters of carpus; dactyl compressed, about 0.19 of propod length, unguis distinct, about 0.4 of dorsal length of corpus, corpus about 2.5 times longer than proximal depth, with one distolateral sensory seta, ventral margin feebly concave, with acute distal accessory tooth, distal accessory tooth reaching at about proximal 0.4 of unguis; propod about 0.64 of carapace length, 10.5 times longer than maximum wide, slightly tapered distally, with one pair of slender simple distoventral spines, one pair of similar subdistoventral spines, three single spines distributed on ventral margin, one small transverse row of long setae distolaterally and scattered setae on distodorsal and ventral margin; carpus about 0.47 of propod length, 4.2 times longer than distal width, unarmed; merus 0.94 of propod length, 8.85 times longer than wide, uniform, unarmed; ischium 0.42 of propod length, 3.62 times longer than distal width, slightly proximally tapered; 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 distal 9/10 propod.

Uropod with protopodite with posterolateral angle short, rounded; exopod 2.5 times longer than central width, lateral border feebly convex, with small acute distal tooth, mobile spine medially lost, diaeresis distinct; endopod subequal to exopod length, 3.3 times longer than wide.

Paratype. Similar to holotype. Rostrum with six dorsal teeth. Telson slender, 1.69 times sixth abdominal somite, 4.1 times proximal width, with four pairs of dorsolateral spines at 0.41, 0.58, 0.72 and 0.88 of telson length, right side with one additional spine at 0.95 of telson length, the spines about 0.056 of telson length; lateral margins straight, tapered distally, posterior margin 0.4 of proximal width, with three pairs of spines, lateral spines similar to dorsolatal spines, intermediate spines long and robust, about 0.12 of telson length, submedian spines slender, non-setae, about 0.36 of intermediate spine length. Uropod exceeding telson tip.

Measurements (mm)

Holotype. Carapace length, 7.3; carapace and rostrum, 10.3; total animal length (proximally), 29.5; left (minor) second pereiopod chela, 7.4; ovum length, 0.73.

Paratype. Carapace length, 6.8; total animal length (proximally), 28.6; left (major) second pereiopod chela, 10.4; right (minor) second pereiopod chela, 6.1.

Systematic position

In its general morphology, especially the raised proximal dorsal rostral carina, Periclimenes forgesi sp. n. shows a close resemblance to P. vaubani Bruce, 1990a . Periclimenes forgesi may be distinguished from that species easily by the four pairs of dorsolateral telson spines, and also the following features: (1) rostrum with deeper lamina; (2) carapace without epigastric tubercle; (3) hepatic spine on carapace subequal to antennal spine; (4) ambulatory propods lacking transverse rows of setae ventrally except the small row distoventrally; (5) scaphocerite with distal lamella distinctly exceeding distolateral tooth; and (6) first pereiopod with carpus shorter than chela. Periclimenes forgesi differs from the other deepwater Periclimenes species with four pairs of dorsolateral telson spines by the short and slender rostrum with a distinct proximal elevated dorsal margin over orbital region, ventral margin straight, with one tooth, cornea well developed, about 0.16 of the postorbital margin carapace length, hepatic not noticably larger than antennal spine, ambulatory propods lacking transverse rows of setae on ventral margin.

Etymology

The specific name is given in honour of the specimen collector, Dr Bertrand Richer de Forges.

Remarks

The small hepatic spines on both sides of the holotype are broken basally, appearing as if articulated on the carapace, making the species appear similar to Allopontonia iaini Bruce, 1972 . But, the armature of ambulatory pereiopods is not as in Allopontonia iaini , in which the ventral border of ambulatory propods are strongly spinulate, the ventral border of dactyl is denticulate, not armed with only one accessory tooth. In addition, Allopontonia is an echinoid-associated genus in shallow water.

Figures

Figure 19. Periclimenes forgesi, new species, holotype ovigerous female (MNHN-Na 14928). (a) Carapace and anterior appendages; (b) anterior carapace; (c) eye; (d) antennule; (e) antenna; (f) mandible; (g) maxillula, upper lacinia and palp; (h, i) same, lower lacinia; (j) maxilla; (k) first maxilliped; (l) second maxilliped.

Figure 20. Periclimenes forgesi, new species, holotype ovigerous female (MNHN-Na 14928). (a) Third maxilliped; (b) first pereiopod; (c) same, chela; (d) second pereiopod; (e) same, fingers; (f) third pereiopod; (g, h) same, distal propod and dactyl; (i) uropod.