Periclimenaeus dactylodon, Bruce, 2012

Bruce, A. J., 2012, Periclimenaeus dactylodon sp. nov. (Decapoda: Pontoniinae), from Heron Island, Queensland, Australia, Zootaxa 3436 (1), pp. 51-60 : 51-60

publication ID	https://doi.org/ 10.11646/zootaxa.3436.1.4
persistent identifier	https://treatment.plazi.org/id/03958792-9221-FFB1-FF47-E91BFB09E501
treatment provided by	Felipe
scientific name	Periclimenaeus dactylodon
status	sp. nov.

Treatment

Periclimenaeus dactylodon View in CoL sp. nov.

( Figs 1 –7 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Material examined. Ovig. ♀, holotype ( QM W29142), 1 ♂ allotype ( QM W29143); 1 ovig. ♀, damaged, paratype ( QM W29144), Wistari Reef, Heron Island , Queensland, coll. R. Boer & Thompson, 8 May 1979, reef front spur, 24.5 m .

Diagnosis. Rostrum with dentition 4-5/0; slender, carapace without supraorbital spines or tubercles, first abdominal tergite without anterior dorsal lobe, scaphocerite reduced, incisor process of mandible bidentate, first pereiopod fingers spatulate, edges entire, second pereiopod chelae smooth, major dactyl with well developed molar process, cutting edge distally finely denticulate, merus with acute tubercles ventrally, minor second pereiopod dactyl semicircular, cutting edge strongly dentate, about 20 teeth, third pereiopod with dactyl lacking distal accessory tooth, with huge acute proximal process, third and fourth pereiopods with propod and carpus swollen, fifth pereiopod slender, caudal fan normal, telson with small dorsal spines at 0.2 and 0.65 of telson length, exopod of uropod with posterolateral tooth and spine only.

Description. Ovigerous female. A small stoutly built shrimp.

Rostrum ( Fig. 1C View FIGURE 1 ) slender, compressed, short, about 0.28 of CL, reaching to end of proximal segment of antennular peduncle, dorsal carina with 4 or 5 similar acute teeth on distal four-fifths, sparse interdental setae, ventral carina obsolete.

Carapace ( Fig. 1 View FIGURE 1 AB) smooth, glabrous, slightly compressed, without supraorbital teeth or tubercles, orbit feebly developed, without associated carinae, antennal spine ( Fig. 1B View FIGURE 1 ) well developed, paraorbital, inferior orbital angle obsolete, anterolateral carapace margin slightly produced.

Abdominal segments, without anteromedian dorsal lobe, first three pleura large, rounded, fourth and fifth smaller with posterolaterally rounded, sixth segment ( Fig. 5 View FIGURE 5 AB) depressed, with small acute posterolateral angle, larger acute posteroventral angle.

Telson ( Fig. 6C View FIGURE 6 ) 0.7 of CL, 2.2 times sixth abdominal segment length, 2.5 times longer than anterior width, laterally feebly convex, converging posteriorly to rounded posterior margin, about 0.33 of anterior width, without median process, with two pairs of small subequal dorsal spines at 0.2 and 0.65 of telson length, posteriorly ( Fig. 6D View FIGURE 6 ) with marginal lateral spines similar to dorsal spines, intermediate spines well developed, robust, simple, about 0.15 of telson length, submedian spines more slender, setulose, about 0.82 of intermediate spine length.

Antennule ( Fig. 1D View FIGURE 1 ) with proximal segment of peduncle ( Fig. 1E View FIGURE 1 ) about 1.8 times longer than central width, medial margin straight, with acute ventral tooth at about 0.5 of length, lateral margin produced, distally concave, with small acute distolateral tooth ( Fig. 5A View FIGURE 5 ), stylocerite acute, phylliform, statocyst with granular statolith, intermediate and distal segments short, subcylindrical, subequal, about 0.3 of proximal segment length, upper flagellum biramous, proximal five segments fused, short free ramus with single segment, with nine groups of aesthetascs, longer free ramus with five segments; lower flagellum short, filiform, with nine segments.

Antenna ( Fig. 1F View FIGURE 1 ) with basicerite unarmed; carpocerite reaching to middle of distal segment of antennular peduncle, far exceeding scaphocerite, subcylindrical, about 5.0 times longer than wide; merocerite and ischiocerite without special features; scaphocerite ( Fig. 1G View FIGURE 1 ) reduced, reaching to 0.6 of carpocerite length, about 3.0 times longer than wide, distal lamella rounded, lateral margin straight with slender distolateral tooth at 0.9 of length, 0.12 of lateral margin length, reaching almost to distal margin of lamella.

Eye ( Fig. 1H View FIGURE 1 ) with cornea hemispherical, oblique, diameter about 0.7 of medial stalk length, without visible accessory pigment spot, stalk about 1.2 times longer than deep, subcylindrical.

Mouthparts, (paratype, right).

Mandible ( Fig. 2A View FIGURE 2 ) with corpus robust, without palp, molar process ( Fig. 5B View FIGURE 5 ) subcylindrical, obliquely truncate distally, densely tessellate, fringed peripherally by short slender spinules; incisor process ( Fig. 5C View FIGURE 5 ) slender, tapering to two small acute distal teeth.

Maxillula ( Fig. 2B View FIGURE 2 ) with feebly bilobed palp ( Fig. 5D View FIGURE 5 ), lower lobe slightly produced with simple terminal seta; upper lacinia ( Fig. 5E View FIGURE 5 )distally convex with seven short simple spines and numerous slender spiniform setae; lower lacinia short, stout, tapering strongly, with numerous long serrulate spiniform setae.

Maxilla ( Fig. 2C View FIGURE 2 ) with flattened tapering palp, about 3.0 times longer than basal width, non-setose, basal endite bilobed, lobes unequal, distal lobe larger, rounded, with about 18 slender simple marginal setae, proximal lobe smaller with about 13 setae, coxal endite obsolete, medial margin convex, non-setose, scaphognathite normal, broad, about 3.0 times longer than central width, anterior lobe 1.2 times longer than wide, medial margin slightly concave, posterior lobe 3.0 times longer than basal width.

First maxilliped ( Fig. 2D View FIGURE 2 ) with flattened palp with slender terminal seta and smaller preterminal seta, basal and coxal endites fully fused, distally rounded, medial margin straight with numerous slender seta, decreasing proximally, exopod normal, flagellum slender, distal setae missing, caridean lobe large, about 2.5 times longer than central width, epipod well developed, rounded, deeply bilobed.

Second maxilliped ( Fig. 2E View FIGURE 2 ) with normal endopod, dactylar segment narrow, with numerous long slender serrulate marginal spines, propodal segment antero-medially rounded, not produced, with several long slender marginal spines, carpus merus and ischiobasis without special features, exopod with slender flagellum with four long ( Fig. 5E View FIGURE 5 ) distallyterminal plumose setae, coxa angularly produced medially, with oval epipod laterally without podobranch.

Third maxilliped ( Fig. 2F View FIGURE 2 ) with ischiomerus and basis fully fused, combined segment 2.3 times longer than basal width, tapering distally, sparsely setose, merus subcylindrical, 2.6 times longer than width, with several groups of spiniform setae medially, terminal segment 0.6 if meral length, 4.2 times longer than proximal width, tapering distally, with numerous spiniform setae, coxa robust, medial margin straight, non-setose, lateral margin with well developed low rounded lateral plate, without arthrobranch.

Thoracic sternite s narrow, unarmed.

First pereiopod ( Fig. 3A View FIGURE 3 ) normal, chela ( Fig. 3B View FIGURE 3 ) about 0.28 of CL, palm subcylindrical, slightly compressed, twice as long as deep, fingers about 0.8 of palm length, broad, spatulate, cutting edges entire, tips rounded with three small terminal teeth; carpo-propodal cleaning setae poorly developed; propod 1.2 times chela length, 3.9 times longer than distal width, tapering proximally; merus about 1.5 times chela length, 5.0 times longer than maximal width, tapering slightly distally; ischium 0.9 of chela length; basis without special features; coxa normal, without ventral process.

Second pereiopods unequal, dissimilar.

Major second pereiopod ( Fig. 4A View FIGURE 4 ) with chela about 1.15–1.28 times CL, palm subcylindrical, slightly swollen centrally, compressed, about 1.7 times longer than depth, smooth, glabrous; fingers ( Fig. 4 View FIGURE 4 BC) 0.33 of palm length, dactyl ( Fig. 4D View FIGURE 4 ) near semi-circular, about twice as long as maximal depth, compressed, dorsal margin strongly convex, tip acute, cutting edge with large molar process proximally, distally concave ( Fig. 4E View FIGURE 4 ), with about 20 small acute teeth, increasing in size distally, proximally minute; fixed finger about as long as proximal depth, cutting edge with deep fossa proximally, dorsal margin with acute setose process, ventral margin with rounded glabrous process, tip acute, slightly hooked; carpus about 0.6 of palm length, 1.5 times longer than maximal depth, distally excavate, tapering proximally, unarmed; merus robust, 1.5 times longer than central depth, slightly swollen centrally, ventral margin with seven small acute tubercles; ischium subequal to meral length, twice as long as distal width, tapering proximally, unarmed; basis and coxa without special features.

Minor second pereiopod ( Fig. 4F View FIGURE 4 ) with chela about 0.82–1.00 of CL, 0.72–0.77 of major chela length, palm sub-cylindrical, slightly swollen centrally, compressed, about 1.9 times longer than depth, smooth, glabrous; fingers ( Fig. 4G View FIGURE 4 ) about 0.28 of palm length, dactyl ( Fig. 4H View FIGURE 4 ) near semi-circular, about twice as long as maximal depth, distinctly exceeding fixed finger, compressed, dorsal margin strongly convex, tip with small rounded tooth continuous with sinuous cutting edge ( Fig. 4I View FIGURE 4 ), distally concave, proximally convex, with series of well developed teeth, about 20 acute teeth, large distally, proximally minute; fixed finger about as long as proximal depth, cutting edge longitudinally grooved, unarmed, tip acute, feebly hooked; proximal segmenta as for major pereiopod but smaller.

Third pereiopod ( Fig. 3C View FIGURE 3 ) robust, dactyl ( Fig. 5F View FIGURE 5 ) about 0.18 of propod length, compressed, unguis short, robust, curved, 1.7 times longer than basal width, without ornamentation, corpus with dorsal margin convex, about twice length of unguis, without distal accessory tooth, distal half of ventral margin feebly convex, entire, proximal half with large angular tooth, corpus with long sensory setae distolaterally, propod ( Fig. 3D View FIGURE 3 ) about 0.28 of CL, swollen, compressed, 2.2 times longer than central depth, tapering slightly distally, with stout distoventral spine laterally, shorter, slender spine medially, sparsely setose; carpus similar to propod, swollen, compressed, about 1.1 times propod length, unarmed; merus robust, 1.3 times propod length, compressed, 2.4 times longer than central width, unarmed; ischium subequal to propod length, 2.4 times longer than distal width, tapering strongly proximally, unarmed; basis and coxa stout, without special features.

Fourth pereiopod ( Fig. 3E View FIGURE 3 ) similar to third, dactyl ( Fig. 3F View FIGURE 3 , 5G View FIGURE 5 ) similar, corpus with distal ventral margin straight, proximal tooth larger, more irregular; propod ( Fig. 3G View FIGURE 3 ) about 0.9 of third propod length, 2.25 times longer than central depth, with paired unequal distoventral spines, proximal segments as in third pereiopod.

Fifth pereiopod ( Fig. 3H View FIGURE 3 ) slender, with dactyl ( Fig. 5H View FIGURE 5 )about 0.19 of propod length, unguis less curved, 2.8 times longer than basal width, about 0.6 of corpus length, corpus 1.5 times longer than proximal depth, ventral margin unarmed, with small rounded protuberance proximally, propod ( Fig. 3I View FIGURE 3 ) 0.4 of CL, 6.3 times longer than depth, subcylindrical, slightly compressed, with numerous distoventral setae and slender preterminal distal ventral spine; carpus about 0.6 of propod length, 4.0 times longer than wide, merus 1.1 times propod length, 4.0 times longer than wide, proximal segments as in third pereiopod.

Pleopods without special features.

Uropod ( Fig. 6E View FIGURE 6 ) normal, protopod posterolaterally unarmed; exopod well exceeding telson, about 2.8 times longer than maximal width, lateral margin convex proximally, straight distally, setose, with small acute distolateral tooth with slender spine medially ( Fig. 6F View FIGURE 6 ), about 2.5 times tooth length, diaeresis obsolete; endopod about 1.1 times exopod length, 3.05 times longer than central width, extending well beyond exopod.

Ova numerous and small.

Allotype, male. Generally similar to paratype female but body much smaller and more slender, with second pereiopod chelae relatively larger, particularly the major chela.

Rostrum as in female with five dorsal teeth, most distal tooth reduced.

Second pereiopods with major chela 2.3 times CL, fixed finger slightly exceeding closed dactylus; minor second pereiopod chela subequal to CL, 0.45 of major chela length, dentition of both chelae as in paratype female.

Ambulatory pereiopods as in paratype female ( Fig. 6 View FIGURE 6 GH).

First pleopod ( Fig. 6I View FIGURE 6 ) basipodite and exopod normal; endopod ( Fig. 6I View FIGURE 6 ) about 0.35 of exopod length, 2.5 times longer than proximal width, tapering distally, rounded, medial margin straight, with six simple spiniform setae, distolateral and distal margin with eight finely plumose setae.

Second pleopod ( Fig. 6K View FIGURE 6 ) basipodite and exopod normal; endopod ( Fig. 6L View FIGURE 6 ) about 0.9 of exopod length, with appendices ( Fig. 6M View FIGURE 6 ) at 0.3 of medial margin length, appendix masculina with corpus reduced, subcylindrical, about twice as long as wide, about 0.07 of endopod length, with two long finely setulose terminal spines, about 0.25mm length, one short preterminal medial spine, appendix interna about three times longer than corpus of appendix masculina, with few terminal cincinnuli.

Measurements. Holotype female—post-orbital carapace length, 2.8 mm; carapace and rostrum, 3.7 mm; total body length (approx.), 13.2 mm; major second pereiopod chela length, 3.6 mm; minor second pereiopod chela length, 2.8 mm; length of ovum, 0.5 mm. Allotype male—post-orbital carapace length, 2.0 mm; carapace and rostrum, 2.8 mm; total body length (approx.), 8.4 mm; major second pereiopod chela length, 5.7 mm, minor second pereiopod chela length, 2.2 mm. Paratype female—post-orbital carapace length, 3.5 mm; carapace and rostrum, 4.3 mm; major second pereiopod chela length, 3.9; minor second pereiopod chela length, 2.9 mm; length of ovum, 0.5 mm.

Host. Unidentified ascidian.

Colouration, (from photo). Generally translucent, with bluish tinge, densely covered with small white chromatophores on body, antennae, pereiopods and caudal fan, cornea golden, ovary pale greenish.

Etymology. From dactylos, Greek, finger, and odous, odontos, Greek, tooth, with reference to the third ambulatory dactyl.

Systematic position. Similar to P. myora Bruce, 1998 . Differs particularly in minor second pereiopod dactyl, ambulatory dactyl and non-swollen third pereiopod propodus and carpus in P. myora .

Periclimenaeus dactylodon and P. myora share the following characters:rostrum slender, with 3–5 acute dorsal teeth; without supraorbital teeth or tubercles; first abdominal tergite without anterodorsal medial lobe; proximal segment of antennular peduncle with distolateral tooth reduced; first pereiopod chela with slender spatulate fingers with entire cutting edges; major and minor second pereiopod dactyls with denticulate cutting edges; without distal accessory tooth on ambulatory dactyls; with acute basal process on ambulatory dactyls.

Periclimenaeus dactylodon and P. myora differ in the following characters: rostrum reaching to distal end of proximal segment of antennular peduncle with 4 or 5 dorsal teeth in P. dactylodon , versus shorter than distal end of proximal segment of antennular peduncle with three dorsal teeth in P. myora ; carpocerite far exceeding scaphocerite in P. dactylodon , versus shorter than scaphocerite in P. myora ; scaphocerite reduced in P. dactylodon , not exceeding middle segment of peduncle, versus normal in P. myora , reaching to end of antennular peduncle; incisor process of mandible in P. dactylodon bidentate, versus multidentate in P. myora ; first pereiopod chela shorter than carpus in P. dactylodon , versus subequal in P.myora ; minor second pereiopod dactyl with cutting edge sinuous with 20 teeth, large distally, minute proximally in P. dactylodon , versus concave with about 40 small acute teeth in P. myora ; third ambulatory dactylar corpus with huge triangular basal process in P. dactylodon , versus a small slender anteroverted tooth in P. myora ; third and fourth pereiopods with propod and carpus inflated in P. dactylodon , versus not inflated in P. myora ; with small dorsal telson spines at 0.2 and 0.65 of telson length in P. dactylodon , versus at about 0.5 and 0.75 in P. myora .

Remarks. Of the 58 Indo-West Pacific species of Periclimenaeus , including P. dactylodon , only 13 have the distal cutting edge of the major second pereiopod dactyl denticulate as well as a denticulate cutting edge on the minor dactyl. Of these, five have not yet had their hosts identified. Two species, P. fawatu Bruce, 2006 , and P. spongicola Holthuis, 1952 , have been reported in association with sponges and six, including P. dactylodon , in association with ascidians. A key for the identification of these species is provided by Bruce (2012).