Periclimenes fenneri, Bruce, A. J., 2005

Bruce, A. J., 2005, Pontoniine shrimps from the 2003 NORFANZ Expedition, 10 May – 16 June (Crustacea: Decapoda: Palaemonidae), Zootaxa 981, pp. 1-20 : 5-11

publication ID	https://doi.org/ 10.5281/zenodo.171357
DOI	https://doi.org/10.5281/zenodo.6267309
persistent identifier	https://treatment.plazi.org/id/03DC837F-536D-DC6D-FECE-6A80C23DE6B3
treatment provided by	Plazi
scientific name	Periclimenes fenneri
status	sp. nov.

Treatment

Periclimenes fenneri View in CoL sp. nov.

( Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 , 8 View FIGURE 8. A C)

Diagnosis: Rostrum slender, dentition 1+9/3, exceeding antennular peduncle; carapace and abdomen smooth; hepatic spine large, antennal smaller; posterior margin of third abdominal tergite minutely denticulate; cornea well developed; fourth thoracic sternite without median process; second pereiopods missing; third pereiopod dactyl feebly biunguiculate, propod with numerous setae, single distoventral spine only: telson with two pairs of dorsal spines.

Material examined. 1 Ψ, NORFANZ stn. 154/109, West Norfolk Ridge, 34°37.20’S 158°59.03’E, 521–539 m, 3 June 2003, beam trawl, NMNZ CR. 9996.

Description: A small sized species of Periclimenes of subcylindrical body form.

Rostrum ( Fig. 2 View FIGURE 2 B) well developed, about 0.85 of CL, slightly exceeding antennular peduncle, slightly upcurved, shallow, acute, dorsal margin with distinct carina, best developed posteriorly, with 9 slender acute teeth evenly distributed along length, first tooth situated posterior to level of orbital margin, interdental spaces with short plumose setae; ventral margin carinate, proximal half concave, unarmed, proximally setose, distal half convex with 3 acute teeth, first tooth ventral to sixth dorsal tooth.

Carapace ( Fig. 2 View FIGURE 2 A) smooth, glabrous, with epigastric tooth at about 0.25 of CL; supraorbital spines absent; orbit feebly developed, inferior orbital angle produced, blunt, without ventral flange; antennal spine small, marginal, not exceeding inferior orbital angle; hepatic spine larger, at lower level than antennal spine, vertically below halfway between epigastric spine and first rostral tooth; anterolateral margin not produced, bluntly subrectangular.

Abdomen ( Fig. 2 View FIGURE 2 K) smooth, glabrous, third tergite not produced or carinate, posterior margin minutely denticulate ( Fig. 4 View FIGURE 4 H); pleura small, broadly rounded, margins nonsetose; sixth segment about 2.0 times as long as fifth, 0.7 of CL, 2.5 times longer than deep, posterolateral angle and posteroventral angles well developed, posterolateral larger, acute, posteroventral smaller, blunt.

Telson ( Fig. 2 View FIGURE 2 L) about 0.7 of CL, subequal to sixth segment length, slender, 3.8 times longer than anterior width, proximal fourth with sides subparallel, posterior three fourths lateral margins straight, posteriorly convergent to angular posterior margin, about 0.5 of anterior margin width, with 2 pairs of well developed similar submarginal dorsal spines, about 0.07 of telson length, at 0.43 and 0.77 of telson length; posterior margin ( Fig. 4 View FIGURE 4 I) with small obtuse median point, lateral spines small, about 0.6 of dorsal spine length, intermediate spines long slender, about 0.19 of telson length, submedian spines well developed, slender, about 0.68 of intermediate spine length, densely setulose.

Antennule ( Fig. 2 View FIGURE 2 C) with proximal segment 2.0 times longer than central width, medial and lateral margins subparallel, medial margin with slender ventral tooth at about 0.5 of length; distal margin with plumose setae, lateral margin with well developed distal lobe, rounded, with 5 short plumose setae, with large slender acute tooth laterally, slightly exceeding half intermediate segment length, distodorsal medially with numerous plumose setae, laterally with arc of about 15 plumose setae reaching to external margin; stylocerite slender, acute, reaching just beyond half segment length, statocyst normal, statolith subcircular. Intermediate segment 2.5 times longer than width, about 0.5 of proximal segment length; medial and lateral margins with long densely plumose setae, very obliquely articulated with distal segment. Distal segment about 0.75 of intermediate segment length, 2.0 times longer than width, flagella incomplete, proximal 4 segments fused.

Antenna ( Fig. 2 View FIGURE 2 D) with basicerite with strong distolateral tooth, ischiocerite and merocerite normal, carpocerite subcylindrical about 3.5 times longer than width, flagella lacking; scaphocerite ( Fig. 2 View FIGURE 2 E) well developed, exceeding antennular peduncle, lamella broad, about 2.8 times longer than central width, distal margin broadly rounded, well exceeding distolateral tooth, lateral margin sublinear, with strong acute distal tooth, about 0.13 of lamellar length.

Eye ( Fig. 2 View FIGURE 2 F) with large, well pigmented, globular cornea, about 0 18 of CL, without accessory pigment spot; stalk short, with about 0.8 of corneal diameter.

Ophthalmic somite small, without median dorsal process.

Epistome unarmed.

Mandible ( Fig. 3 View FIGURE 3 A) with corpus stout, without palp; molar process ( Fig. 4 View FIGURE 4 A) robust, tapering, distally truncate with 4 blunt tubercles and setose knob; incisor process ( Fig. 4 View FIGURE 4 B) distally oblique with 3 acute teeth, central tooth smaller than outer teeth.

Maxillula ( Fig. 3 View FIGURE 3 B) with bilobed palp ( Fig. 4 View FIGURE 4 C), dorsal lobe nonsetose, ventral lobe with small tubercle bearing short curved simple seta; basial endite 1.5 times longer than broad, centrally expanded, distal margin truncate with 6 robust short simple spines, with similar numbers of more slender spines and setae: coxal endite tapering, distally pointed with about 16 long simple distal and ventral spines.

Maxilla ( Fig. 3 View FIGURE 3 C) with tapering palp about 3.5 times longer than basal width,. with 3 short proximolateral setae, basial endite bilobed, distal lobe larger and longer than proximal lobe, with about 11 slender simple setae, proximal lobe with 8; coxal endite obsolete, medial margin broadly convex; scaphognathite elongate, narrow, about 3.0 times longer than central width, anteromedial margin emarginate.

First maxilliped ( Fig. 3 View FIGURE 3 D) with elongate, very slender palp, about 13.0 times longer than basal width, with preterminal plumose seta; basial endite broad, distally rounded, medial margin straight with numerous slender simple setiform spines marginally and submarginally, distinctly separated by small notch from smaller rounded coxal entire, fringed with 6 simple setae; exopod with well developed caridean lobe, flagellum appearing normal, although distal portion lost; epipod well developed, deeply bilobed, distal lobe larger than proximal.

Second maxilliped ( Fig. 3 View FIGURE 3 E) of normal form, endopod with dactylar segment broad, about 2.5 times longer than distal width, medial margin straight, with numerous robust. simple spines; propodal segment with anteromedial margin slightly medially produced, with numerous slender setiform spines; carpus, ischiomerus and basis without special features; exopod well developed, with 4 long plumose terminal setae, few short distal setae; coxa with large rounded lobe medially, with 6 slender simple setae; epipod subtriangular, without podobranch.

Third maxilliped ( Fig. 3 View FIGURE 3 F) extending to proximal end of carpocerite; ischiomerus fused to basis, junction indicated by small notch on medial margin, ischiomeral portion about 6.0 times longer than width, uniform, medial margin with numerous long simple setae, distolateral margin with two small blunt spines ( Fig. 4 View FIGURE 4 D), penultimate segment 0.7 of antepenultimate segment length, 4.3 times longer than proximal width, with numerous slender simple setae distributed along medial margin, terminal segment 0.5 of antepenultimate segment length, about 5.0 times longer than basal width, tapering distally terminating in short simple spine ( Fig. 4 View FIGURE 4 E), about 0.14 of segment length, ventromedial surface with about 6 transverse rows of setae, of increasing length distally, basal region with concave medial margin, nonsetose, exopod as second maxilliped, coxa with medial margin angular, with well developed semicircular lateral plate, without arthrobranch.

Thoracic sternites broad, third and fourth with low transverse ridge, fifth with stronger ridge with median notch, sixth to eighth unarmed, fourth without fingerlike median process.

First pereiopod ( Fig. 2 View FIGURE 2 G) slender, exceeding carpocerite by carpus and chela; chela ( Fig. 2 View FIGURE 2 H) slender, with subcylindrical palm about 3.0 times longer than deep, with two rows of short cleaning setae proximoventrally, fingers similar, slender, tapering distally, about 0.66 of palm length, with groups of long finely serrulate setae distally, distal half of cutting edges sharp, entire, tips strongly hooked with small stout terminal ungues; carpus about 1.3 times chela length, 7.0 times longer than distal width, tapering proximally, with several long robust serrulate setae distoventrally; merus slender, subequal to carpal length, uniform, 8.5 times longer than wide; ischium 0.54 0f carpal length, 3.8 times longer than distal width, tapering slightly proximally; basis and coxa of normal form, ventral basis with group of several short setae, distoventral coxa with small lobe with longer terminal setae.

Second pereiopods. Missing.

Third pereiopod. ( Fig. 2 View FIGURE 2 I) slender, exceeding carpocerite by distal third of carpus, propod and dactyl; dactyl normal ( Fig. 4 View FIGURE 4 F), slender, curved, feebly biunguiculate, about 0.15 of propod length; unguis ( Fig. 4 View FIGURE 4 G), feebly demarkated from corpus, curved, about 3.7 times longer than basal width, 0.75 of corpus length, corpus 1.8 times longer than basal width, dorsal margin convex, ventral margin concave with small subrectangular distal accessory tooth; propod ( Fig. 2 View FIGURE 2 J) about 0.7 of CL, 13.0 times longer than width, uniform, with numerous groups of long simple setae distally, largely obscuring the dactyl, with 1 distoventral spine (possibly 2), length greater than basal width of dactyl, 1 similar preterminal distoventral spine, ventral margin otherwise without spines or setae; carpus about 0.45 of propod length, 4.0 times longer than distal width, tapering slightly proximally, unarmed; merus subequal to propod length, 10.0 times longer than width, uniform, unarmed; ischium 0.6 of merus length, bowed, 0.6 times longer than depth, uniform, unarmed; basis and coxa without special features. Fourth and fifth pereiopods similar to third.

Uropod ( Fig. 2 View FIGURE 2 M) with protopodite normal, posterolaterally unarmed; rami slightly exceeding posterior telson margin, exopod about 3.6 times longer than distal width, with lateral margin entire, proximally feebly convex, distally sublinear, nonsetose, with small acute distal tooth, with much larger mobile spine medially ( Fig. 4 View FIGURE 4 J), dieresis poorly indicated; endopod slightly shorter than exopod, about 4.0 times longer than maximal width.

Measurements: Carapace length, 4.8 mms; carapace and rostrum, 9.0 mms; total body length (approx.), 25.0 mms.

Colouration ( Fig. 8 View FIGURE 8. A C): (From colour photo). Generally translucent, without conspicuous colouration. Second pereiopod with pinkish fingers.

Host: No data.

Etymology: The species is named in recognition of the enormous contribution to caridean systematics of Dr Fenner A. Chace (19082004).

Systematic position: Several “deepwater” species of Periclimenes have simple biunguiculate dactyls on the ambulatory pereiopods and two pairs of dorsal spines on the telson: P. coriolis Bruce, 1985 , P. curvirostris Kubo, 1940 , P. foveolatus Bruce, 1981 , P. involens Bruce, 1996 , P. laccadivensis (Alcock and Anderson, 1894) , P. latipollex Kemp, 1922 ., P. ordinarius Bruce, 1991 , P. parvispinatus Bruce, 1990 , P. richeri Bruce, 1990 , P. tenuirostris Bruce, 1991 , and P. vaubani Bruce, 1990 . All of these have a well developed, acute accessory tooth on each ambulatory dactyl. In none of these has a denticulate posterior margin to the third abdominal tergite been reported. The mouthparts of P. fenneri are typical of the genus Periclimenes .

Periclimenes fenneri appears most closely related to P. laccadivensis (Alcock and Anderson) and may be distinguished by the following features:

1 In P. fenneri the rostrum is longer, distinctly exceeding the antennular peduncle, vs falling short of distal end in P. laccadivensis .

2 Only a single postorbital rostral tooth present in P. fenneri , , vs two postorbital teeth in P. laccadivensis .

3 Posterior margin of third abdominal tergite denticulate in P. fenneri , vs entire in P. l a c cadivensis.

4 Carpus of first pereiopod about 1.3 times chela length in P. fenneri , vs “a little longer than chela” ( Kemp, 1922).

5 Dactyl of third ambulatory pereiopod with obsolescent accessory tooth in P. fenneri , vs well developed slender acute accessory tooth in P. laccadivensis .

Remarks: The present specimen is remarkable for the presence of a series of minute denticulations along the posterior margin of the third abdominal tergite. Such denticulations have only been recorded in species of the genera Exoclimenella Duris and Bruce, 1995 , and Periclimenella Duris and Bruce, 1995 . The species of these genera have the fingers of the first pereiopods strongly spatulate with finely pectinate cutting edges and can thus be readily omitted from consideration. These fingers in the present specimen lack these features and are typical of the genus Periclimenes . The tergal denticulations can be difficult to discern and may have been overlooked in other species of Periclimenes . Despite the lack of second pereiopods, P. fenneri can still be distinguished from all other IndoWest Pacific species of the genus Periclimenes by the diagnostic dactylus of the ambulatory pereiopods.