Periclimenes pseudalcocki, 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 : 716-719

Periclimenes pseudalcocki sp. nov.

( Figure 30 )

Material examined

Indonesia: KARUBAR, Kai Islands , stn CP16, 5 ° 179S, 132 ° 509E, 315–349 m, 24 October 1991, 1♀ holotype (MNHN-Na 14855) .

Description

A large pontoniine shrimp of subcylindrical body form, very similar to Periclimenes alcocki Kemp, 1922 .

Carapace smooth, glabrous. Rostrum well developed, compressed, deep, especially anteroventrally and distinctly upcurved distally, distinctly overreaching antennular peduncle, extending near to tip of scaphocerite, about 0.68 of carapace length; dorsal margin with seven low acute teeth, first tooth situated on carapace just behind level of posterior orbital margin; lateral carinae well developed, except upcurved distal part; ventral margin with two small acute teeth on distal third and subapical small tubercle, first tooth at level of last dorsal tooth. Supraorbital spine absent; epigastric spine similar to dorsal rostral tooth, situated at anterior 0.23 of carapace length; orbit feebly developed, inferior orbital angle produced, oval rounded; antennal spine small slender marginal, distinctly below the inferior orbital angle, not exceeding inferior orbital angle; hepatic spine larger than antennal spine, stout, slightly lower than antennal spine, below 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 2.0 times length of fifth, subcylindrical, about 1.52 times longer than central depth, posterolateral angle acute, posteroventral angle rounded. Telson about 1.64 times sixth segment length, slender, about 3.35 times longer than anterior width, lateral margins sublinear, convergent, dorsal surface with four pairs of dorsolateral spines at 0.45, 0.64, 0.78 (average), and 0.90 (average) of telson length, dorsal spines about 0.045 of telson length; posterior margin about 0.40 of anterior margin width, rounded, with minute sharp posterior median point; posterior margin with normal three pairs of spines, lateral spines short and robust, similar to dorsolateral spines, intermediate spines long, robust, about 0.075 of telson length, submedian spines about 0.41 of intermediate spine length, non-setulose.

Eye reduced, with globular cornea, corneal diameter 0.11 of posterior orbital carapace length, without accessory pigment spot; stalk feebly compressed, subuniform, dorsal width subequal to corneal diameter, length 0.95 of corneal diameter.

Antennular peduncle overreaching second ventral rostral tooth; proximal segment about 1.43 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 0.54 of length; intermediate segment with dorsal length about 0.3 of proximal segment length, subequal to width, lateral margin expanded, setose, medial margin strongly setose; distal segment about 0.54 times proximal segment length, slender, about 1.7 times longer than distal width; upper flagellum well developed, biramous, with proximal 12 segments fused, shorter free ramus with four segments, length about 0.28 of fused portion, total length about 0.49 of carapace length, with about 28 groups of aesthetascs; longer ramus slender, filiform, about 0.55 of carapace length; lower flagellum slender, filiform, about 0.83 times carapace length.

Antennal basicerite robust, with strong acute distolateral tooth; carpocerite subcylindrical, about 0.39 of scaphocerite length, 2.67 times longer than width; flagellum well developed, slender, about 2.0 times postorbital carapace length; scaphocerite well developed, distinctly exceeding rostral tip, broad, about 2.16 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 notch, 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 reaching to distal end of carpocerite, similar to that of P. alcocki , coxa with arthrobranch distinct.

First pereiopods moderately slender, exceeding distal margin of antennal scale by chela, exceeding carpocerite by chela and five-sixths carpus; similar to that of P. alcocki .

Second pereiopods well developed, subsimilar except the fingers, chelae covered with small tubercles. Major (right) pereiopod exceeding distal end of antennal scale by chela, carpocerite by chela, carpus and distal third merus; minor (left) pereiopod also exceeding distal end of antennal scale by chela, carpocerite by chela, carpus and distal third merus. Other features very similar to those of P. alcocki .

Ambulatory pereiopods slender. Third pereiopod exceeds carpocerite by dactyl, propod and distal two-fifths carpus, scaphocerite by dactyl and half propod; dactyl compressed, slender, curved, about 0.18 of propod length, unguis distinct, about 0.62 of dorsal length of corpus, 5.5 times longer than proximal width; corpus about 2.57 times longer than proximal depth, dorsal margin feebly convex, non-setose, ventral margin largely feebly concave, except feebly convex proximal portion, distal accessory tooth acute, minute, about 0.11 of unguis length, with single short distolateral sensory seta; propod compressed, subuniform, about 0.52 of carapace length, 8.3 times longer than wide, with three transverse rows of long simple setae distoventrally and one row of similar setae distodorsally, without distoventral spines, major part of ventral border unarmed, nonsetose; carpus feebly compressed, tapering feebly proximally, about 0.59 of propod length, 4.9 times longer than distal width, with long produced distodorsal lobe, unarmed; merus compressed and feebly twisted, 1.16 of propod length, 7.9 times longer than central width, uniform, unarmed; ischium compressed, 0.64 of propod length, 4.0 times longer than distal width, feebly proximally tapered; basis and coxa without special features. Fourth and fifth pereiopods similar to third, fourth propod 1.1 of third propod length, fifth propod subequal to fourth; fourth and fifth dactyl with the accessory tooth very minute, like tubercle; fifth exceeds carpocerite by dactyl and distal two-thirds propod, scaphocerite by dactyl.

Pleopods without special features.

Uropod distinctly exceeding distal end of telson, exopod reaching the distal tip of extended intermediate posterior spines; protopodite with distolateral lobe broadly rounded; exopod 2.17 times longer than central width, lateral border feebly convex, with small distal tooth, and larger mobile spine medially, diaeresis distinct, at 0.75 of length; endopod subequal to exopod length, 2.7 times longer than central width.

Measurements (mm)

Carapace length, 8.64; carapace and rostrum, 14.2; total body length (approximately), 40.0; right (major) second pereiopod chela, 10.32; left (minor) second pereiopod chela, 7.88.

Systematic position

Periclimenes pseudalcocki n. sp. is very close to P. alcocki Kemp, 1922 . It can be distinguished from the latter by the smaller accessory tooth of ambulatory dactyl which is at most 0.11 of unguis length (in third pereiopod, it is like a tubercle in the fourth and fifth pereiopod), and the propod has no distoventral or ventral spines. In P. alcocki , the accessory tooth of ambulatory dactyl is about 0.2 of unguis length, and propod has one distoventral spine and two ventral spines. In addition, the rostrum of P. pseudalcocki is deeper, and dorsal telson spines larger (about 0.045 of telson length, it is 0.03 in P. alcocki ). Periclimenes pseudalcocki can be distinguished from other allied deep-water species with four pairs of dorsolateral telson spines by the markedly reduced cornea, the corneal diameter 0.11 of carapace length. Periclimenes pseudalcocki is also very similar to P. crosnieri n. sp. It can be distinguished from that species by the biunguiculate third pereiopod dactyl, non-spinules propod, reduced cornea, and other detailed features.

Etymology

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

Figures

Figure 30. Periclimenes pseudalcocki, new species, holotype female (MNHN-Na 14855). (a) Carapace and anterior appendages; (b) telson; (c) same, distal part; (d) eye, dorsal view; (e) antennular peduncle; (f) antenna; (g) third pereiopod; (h) same, distal propod and dactyl, lateral view; (i) same, medial view.