Periclimenes sulcatus, Uriš, Zden Ě K Ď, Horká, Ivona & Marin, Ivan, 2008

Uriš, Zden Ě K Ď, Horká, Ivona & Marin, Ivan, 2008, Periclimenes sulcatus sp. nov., a new pontoniine shrimp (Crustacea: Decapoda: Palaemonidae) from Vietnam, Zootaxa 1860, pp. 35-50 : 36-45

Periclimenes sulcatus sp. nov.

( Figs 1–7 )

Diagnosis.— Periclimenes species with rostrum arched dorsally and straight ventrally, rostral dentition 1–2 + 5–8/1–2, posteriormost tooth (‘epigastric spine’) isolated from remainder of dorsal rostral series, situated posterior of hepatic spine, antennal and hepatic spines small, antennal spine marginal, hepatic spine slightly lower than antennal spine, lower orbital angle ovate, fourth thoracic sternite with subtriangular median process, cornea diameter about 0.25 of CL, accessory pigment on eyestalk spot large and with facets, first and second chelipeds feebly developed, fingers with cutting edges simple, third to fifth pereiopods dactyli biunguiculate, slender, propodi spinulate distoventrally, first three abdominal tergites with transverse sulci, telson with 4–6 pairs of small dorsolateral spines.

Material examined.— S of Nhatrang Bay, Vietnam, 12°09' 42.0" N; 109° 12' 13.1" E, tidal pools with seagrass, 0.1–0.2 m, hand net, 4 Sep. 2006, coll.: I. Marin, I. Horká, Z. Ď uriš: 1 Ψ ov. holotype, RMNH D 51964; 2 spms paratypes (1 Ψ ov., 1 Ψ), RMNH D 51970.— Same locality, Oct. 2006, coll.: I. Marin, 17 spms paratypes (4 ɗɗ, 4 ΨΨ ov., 4 ΨΨ, 5 juvs), ZMMSU.— Same locality, 11 Aug. 2007, 0.1–0.2 m, hand net, coll. Z. Ď uriš, I. Horká: 6 spms paratypes (2 ɗɗ, 2 ΨΨ ov., 2 ΨΨ), QM W28388. 12 spms paratypes, (4 ɗɗ, 4 ΨΨ, 4 ΨΨ ov.), NHMW 23024–23026.— Same locality, 8 Sep. 2007, 0.1–0.2 m, hand net, coll. Z. Ď uriš, I. Horká: 1 ɗ allotype, RMNH D 51965 . 19 paratypes (6 ɗɗ, 4 ΨΨ ov., 4 ΨΨ, 5 juveniles), RMNH D 519666–51968. 5 spms paratypes (juvs), QM W28389. 20 spms paratypes (8 juveniles, 4 ɗɗ, 4 ΨΨ, 4 ΨΨ ov.), CMN-ZC 02224– 0 2227. 12 spms (4 ɗɗ, 4 ΨΨ ov., 4 ΨΨ), MNHN-Na 16729–16731; 17 spms (4 ɗɗ, 4 ΨΨ, 4 ΨΨ ov., 5 juvs), ION. 5 juvs, NHMW 23023.— Hon Chong Beach, N of Nha Trang, 12°16' 21.4" N; 109°12' 13.5" E, 12 Aug. 2007, hand net, discarded fishnet net with scattered red algae, sandy bottom, 4 m, coll. Z. Ď uriš, I. Horká: 2 ΨΨ paratypes, MNHN-Na 16733.— N of Nhatrang Bay, 12°17'45.8"N; 109°14' 05.7"E, coll. Z. Ď uriš, I. Horká: 13 Sept. 2007, hand net, from gorgonian coral Rumphella sp., depth 4 m: 3 juvs paratypes, MNHN-Na 16732.Other material examined: 961 spms, S off Nhatrang Bay, Oct. 2006 coll. I. Marin, and Aug.–Sept. 2007, coll. Z.Ď uriš, I. Horká).

Description—ovigerous female holotype.—Body subcylindrical ( Fig. 1 ).

Rostrum ( Fig. 2 A) well developed, straight, reaching to about middle of distal antennular segment, about 0.85 of CL, slender, dorsal carina distinct, with 8 small acute evenly distributed teeth, similar but diminishing anteriorly, one tooth situated behind orbit, with numerous short interdental setae, ventral margin slightly concave, carina obsolete, with long plumose setae along whole length up to distal teeth, 2 small acute teeth distally; epigastric spine feebly separated from carapace by indistinct suture.

Carapace ( Figs 1 , 2 A) smooth, glabrous, with epigastric spine separated from first rostral tooth by larger gap than between first and second dorsal teeth, supraorbital spine absent, inferior orbital angle pronounced, obtusely angulate, with ventral flange (similar to that of a male paratype – Fig. 6 C), antennal spine slender, submarginal, placed well below and not exceeding inferior orbital angle, hepatic spine small, slender, about one spine length posterior to anterior carapace margin, slightly lower than antennal spine level, pterygostomian angle in right angle, obtuse.

Fourth thoracic sternite with subtriangular, ventrally flattened and anteriorly acutely produced median process, fifth sternite with low transverse lateral carina with wide shallow median notch, sixth to eighth sternites unarmed. Five pleurobranchs present on body wall.

Abdominal segments I–III with 1, 2 and 1 (respectively) low but distinct tranverse sulci dorsally and dorsolaterally ( Fig. 1 A–B). Third segment tergite slightly posterodorsally produced, sixth segment about 1.6 times fifth segment length, 1.8 times longer than deep, 0.8 of CL, fourth pleura bluntly angular, fifth pleura angular, not pointed.

Telson ( Fig. 2 D) about 0.8 of CL, 3.8 times longer than anterior width, lateral margins slightly sinuous, convergent, with 5 pairs of small similar submarginal dorsal spines, with first and last ones at about 0.5 and 0.85 of telson length (respectively), with spaces between pairs gradually diminishing posteriorly, posterior margin broadly subtriangular, about 0.4 of anterior width, lateral spines small, robust, 1.5–2 times longer than dorsal spines, intermediate spines about 0.2 of telson length, submedian spines about 0.6 of intermediate spine length, plumose.

Eyes ( Fig. 2 A–B) not reaching end of basal antennular peduncle, with well developed, pigmented globular cornea, with distinct, produced accessory pigment spot with facets, less distinct but larger than corneal facets, corneal diameter about 0.25 of CL, slightly wider than distal end of stalk, stalk length about 1.4 of corneal diameter.

Antennule peduncle ( Fig. 2 A–B) well exceeding rostrum, proximal segment of peduncle about 2.3 times longer than wide, medial margin straight, with small ventromedial tooth at about half of length, distolateral angle produced to distal tooth slightly exceeding anterior margin of anterior lobe, stylocerite slender, reaching to about 0.6 of medial margin length, statocyst normal; intermediate segment about 1.3 times wider than long, 0.2 of proximal segment length, lateral margin with numerous plumose setae, medial margin similarly setose; distal segment twice longer than wide, 0.25 of proximal segment length; upper flagellum biramous, proximal 6 segments fused, shorter free ramus with 3 segments, with about 6 groups of aesthetascs, longer free ramus and lower flagellum slender, filiform.

Antenna ( Fig. 2 A–B) with basicerite with well developed acute ventrolateral tooth; dorsal lobe quadrangular; carpocerite subcylindrical, reaching to about 0.5 of scaphocerite length, flagellum well developed, scaphocerite well exceeding antennular peduncle, about 3.5 times longer than broad, anterior margin rounded but projecting distomedially, lateral margin straight, with well developed tooth at 0.85 of scaphocerite length, lamina far exceeding distolateral tooth.

First pereiopod ( Fig. 3 A) normal, neither slender nor robust, reaching to end of first basal antennular segment, chela ( Fig. 3 B) with finger held ventrolaterally, ventral margin convex; palm slightly compressed, about twice as long as deep, with several transverse groups of short denticulate setae proximoventrally, fingers slightly shorter than palm, simple, with some groups of setae, both dactyl and fixed finger unidentate distally, cutting edges entire with narrow distal lamina; carpus subcylindrical, about 1.1 times chela length, 6 times longer than distal width, tapering proximally, unarmed; merus about 1.05 times carpus length, 1.2 times chela length, 6 times longer than width, unarmed; ischium about 0.4 of merus length, 0.45 of chela length; basis without special features, coxa with elongate setose ventral lobe ( Fig. 3 C).

Second pereiopods ( Fig. 3 D) similar, equal and slender, but similar to and only 1.4 times longer than first pereiopods, overreaching scaphocerite by length of fingers; chela ( Fig. 3 D) with finger held ventrolaterally, about 0.5 CL, ventral margin slightly sinuous, concave on level of fixed finger base; palm subcylindrical, oval in section, about 2.4 times longer than depth, fingers ( Fig. 3 E) about 1.2 times longer than palm; dactylus slender, 6.5 times longer than maximum depth near base, cutting edge laminar with series of 10 short spiniform setae on side of lamina and almost regularly spaced along lamina, proximally with low tubercle, dorsal margin convex without lateral flange; fixed finger with acute upturned tip, cutting edge similar to dactylar edge, with shallow basal pit to accommodate dactylar tubercle; carpus about 0.8 of chela length and 1.6 of palm length, 6 times longer than distal width, feebly expanded distally, tapered proximally; merus about 0.8 of carpus length, 5.5 times longer than deep, uniform; ischium 0.9 of chela length, 1.4 times merus length, about 10 times longer than distal width; basis about 0.24 ischium length, slender, unarmed; coxa without special features.

Third pereiopods ( Fig. 3 F) slender, not reaching end of scaphocerite but reaching about end of antennular peduncle; dactyl ( Fig. 3 I) slender, biunguiculate, gently curved, compressed, about 0.33 of propod length, 6.3 times longer than basal depth, unguis slender, situated at 0.65 of dactylar length, dorsal margin convex, ventral margin concave with well developed acute distal accessory tooth reaching about 0.4 of unguis length, with distolateral pair of sensory setae; propod about 0.6 of CL, about 15 times longer than wide, with pair of long slender distoventral spines ( Fig. 3 I) slightly longer than distal propod width or 0.33 of dactyl length, with two single ventral spines more proximally; carpus 0.6 of propod length, merus unarmed, 0.9 of propod length and 1.5 of carpus length, ischium 0.5 of merus length, basis and coxa short, without special features.

Fourth and fifth pereiopods ( Fig. 3 G–H,J–K) similar to third but slightly longer, with propodal to meral segments increasing in length—propodi of fourth and fifth legs 1.1 and 1.3 times longer (respectively) in comparison with third leg, carpi 1.0 and 1.2 times longer, meri 1.1 and 1.2 times, and ischia 1.05 and 1.3 times longer (respectively) than ones of third legs; propodal spinulation 2+2+1 on fourth legs and 4+3 (or 2)+2+1 spines situated distoventrally (respectively, from distal to proximal spines).

Uropod ( Fig. 2 D) normal; protopodite posterolaterally unarmed; exopod slightly exceeding telson, endopod reaching distal end of telson; exopod 3.5 times longer than width, with lateral margin straight, unarmed, setose ventrally, with small acute distolateral tooth with larger mobile spine medially; endopod about 0.85 of exopod length, 3.5 times longer than wide.

Mouthparts (ovigerous female paratype CL 1.9 mm, RMNH D 51970).—Paragnaths ( Fig. 4 A) well developed, alae with transversely elongate distal lobes and small ovate ventromedial lobes, corpus broad with posteriorly widening median groove bordered by swollen carinae. Mandibles ( Fig. 4 B–E) without palp, molar process stout, subcylindrical, expanding distally, with three large blunt processes, one setose, two smaller processes intervening, incisor process well developed, distally oblique with larger medial and lateral teeth and one smaller intermediate tooth, with two additional minute distal teeth on medial margin (left, Fig. 4 B,C), or three intermediate teeth (right mandible, Fig. 4 D,E). Maxillula ( Fig. 4 F) with bilobed palp, lower lobe with small ventral tubercle bearing short simple seta, upper lacinia broader proximally, tapering distally to transverse distal margin with about 8 short simple spines, with numerous short simple setae, some spiniform; lower lacinia elongate, with short slender spines and simple spiniform setae. Maxilla ( Fig. 4 G) with slender palp, about 3.5 times longer than basal width, tapering slightly distally, terminally rounded, three short plumose setae proximolaterally, basal endite deeply bilobed, upper lobe with about 15 slender simple (some serrulate) distal setae, lower lobe slightly more slender, with about 12 distal setae, coxal endite obsolete, medial margin non-setose; scaphognathite normal, about 3 times longer than central width, anterior lobe about 1.4 times longer than basal width, medial margin convex. First maxilliped ( Fig. 4 H) with slender tapering palp, about 4.5 times longer than basal width, basal endite well developed, broad, distally rounded, medial margin straight, with numerous simple long marginal and submarginal setae, coxal endite feebly separated from basal, medial margin convex with sparser similar setae; exopod with well developed flagellum with four plumose terminal setae, caridean lobe large, with numerous plumose marginal setae; epipod rounded, feebly bilobed, lobes subequal. Second maxilliped ( Fig. 4 I) of normal form, endopod with dactylar segment broad, about three times longer than central width, with numerous stout serrulate spines medially, propodal segment with distal margin broadly rounded with numerous spiniform marginal setae, carpus, merus and ischiomerus without special features; exopod with well developed flagellum with four long plumose terminal setae; coxa with medial margin slightly produced, setose, with ovate epipod laterally, without podobranch. Third maxilliped ( Fig. 4 J) with endopod robust, reaching to about distal end of carpocerite; ischiomerus feebly distinct from basis, about five times longer than proximal width, medial and lateral margins with numerous setulose setae, distal half with series of seven distinct ventrolateral to distoventral spines, penultimate segment about 0.6 of ischiomerus, about five times longer than width, with numerous slender simple setae distomedially and laterally, terminal segment about 0.7 of penultimate segment length, with numerous groups of simple or finely setulose spiniform setae, four transverse rows ventrally, basis short, about 0.2 of ischiomeral length, exopod with flagellum well developed, reaching almost to end of ischiomerus, with four long terminal plumose setae, coxa with medial process, unsetose, with large rounded lateral plate, with small bi-lamellar arthrobranch.

Male allotype.— The specimen ( Fig. 5 A) agrees well with the description of the holotype female, with the following exceptions: (1) rostrum shorter, reaching to middle of second antennular segment, with 7 dorsal teeth (latter one not post-orbital), epigastric spine present, (2) antennule with both upper and lower flagella about 3 or 2 times (respectively) longer than peduncle; with about 12 groups of aesthetascs; (3) more distinct and densely situated sensory setae on lower antennular and antennal flagella; (4) dorsal abdominal sulci less pronounced but distinct, with only one sulcus on second tergite; (5) pleopodal basipodites swollen, not slen- der, (6) male gonopods—as follows:

First pleopod ( Fig. 5 B) basipodite about 2.5 times longer than maximal width; exopod 1.2 times basipodite length, 4.0 times longer than wide; endopod 0.35 of exopod length, 1.6 times longer than central width (proximally off medial lobe), distally angulate, with rounded tip, medial margin with accessory, distally directed lobe rising on 0.5, and reaching 0.85, of endopod length, lateral notch of lobe reaching 0.74 of endopod length; with three short plumose setae distolaterally, medial margin with 5 long strong spiniform setae on proximal 0.4 of endopod length.

Second pleopod ( Fig. 5 C) with basipodite about 2.3 times longer than maximal width, slightly longer than first pleopod basipodite; exopod subequal to basipodite length, 3.5 times longer than maximal width; endopod about 0.9 of exopod length, 3.8 times longer than width, appendices at 0.33 of medial margin length, appendix masculina with corpus subcylindrical, slightly tapering distally, 6.5 times longer than width proximally, with 3 long slender simple terminal spines; appendix interna 1.2 times appendix masculina, with group of about 11 cincinnuli distomedially.

Remarks. The available material provides data on the morphological variability of Periclimenes sulcatus sp. nov. There are some remarkable differences between sexes, in addition to the shape of the male gonopods ( Fig. 5 B–E). The rostrum in males ( Figs 5 A, 6B) is shorter, not reaching the end of the intermediate segment of the antennular peduncle, while it reaches to the middle or the end of the third peduncular segment in grown and ovigerous females ( Figs 1 A, 2A–B, 6A). The antennular flagella are remarkably longer in males ( Fig. 6 B) than in females, being at least 2–3 times longer than the peduncle, but only about 1.5 times longer in females ( Figs 2 A–B, 6A). Both the lower antennular flagellum and the antennal falgellum of males bear more distinct and densely situated sensory setae on the upper surfaces ( Fig. 5 A). The pleopodal basipodites are swollen in males ( Fig. 5 A–C) but slender in females. The uropodal endopod is more heavily setose (plumose setae) dorsally in males ( Fig. 6 G) than in females.

The rostral dentition is variable to some extent. The epigastric spine may be reduced or lacking in some specimens, although well present in the majority of individuals. The dorsal rostral series consists of 6–9 teeth, with one or no tooth being post-orbital in position, while the ventral margin bears 1–2 distal teeth. Juveniles may have 3 or more dorsal teeth and a slender rostral apex. The maximum number of dorsal rostral teeth was found in the largest animals – invariably the ovigerous females; the minimum number was mainly in the smallest juvenile males – the latter with only one ventral tooth.

The lower orbital margin possess, although somewhat inconspicuous in the holotype or allotype, a ventral flange, well visible on the photograph from the scanning electron microscopy (SEM) of a male ( Fig. 6 C).

A minor variation was found in mouthparts. The incisor process of the mandibles usually has four strong terminal teeth, in contrast to three or five in the paratype female ( Fig. 4 B–E). The ischiomeral spinulation of the third maxillipeds may vary between 5 and 7 spines.

The posterior marginal denticulation on the dorsum of the third abdominal segment, recognized in some pontoniines, eg. genera Exoclimenella and Periclimenella (Ď uriš and Bruce 1995), is absent in P. s u l c a t u s sp. nov. A regularly cut marginal carina was, however, observed laterally on the posterior margins of the first and second segments ( Fig. 6 F), and also dorsally on the posterior margin of the carapace ( Fig. 6 E).

One of the most remarkable characteristics of the new species, which is reflected also in the proposed specific name, is the presence of distinct dorsal and dorso-lateral sulcation on the first three abdominal tergites. In some specimens, the sulcation may be obscure or less developed, but in most of them it is distinct and adding something like „false segmentation“ to the dorsal outline of the appropriate segments. In most adult specimens, at least the anterior sulcus is well distinct on these segments ( Fig. 6 D). This sulcation is also well developed in juveniles.

Another feature, the most important for the species recognition, is the multiple dorsal telson spination. The number of these spines commonly varies from 4 to 6 pairs. The maximum number is found mainly in ovigerous females (about 44 % of these are with 6 pairs). Only exclusively (6 % of 50 specimens examined for the telson armament) there are 3 spines on one side, but the second one has 4 spines in all these cases.

Measurements (mms).— Holotype: CL 1.95; RL 1.8; TL (approx.) 11.5; first pereiopod chela 0.7; second pereiopod chela 1.1; eggs (approx. 40 ones, stage – early eyespots) 0.46–0.48 x 0.32–0.34. Male allotype: CL 1.3; RL 1.2; TL (approx.) 10.0. Paratypes: ovigerous females: CL 1.7–2.4; RL 1.5–2.1; TL max.14; males: CL 1.4–1.75; RL 1.1–1.5; TL 8.5–11.5. The largest ovigerous female measured (CL 2.4, OU collection, Oct. 2006) had 99 eggs with eyespots, 0.48 x 0.34 mm large; the smallest ovigerous female measured (CL 1.3, OU collection, Oct. 2007), had 28 early eggs 0.40 x 0.30 mm large.

Habitat.— The species mainly inhabits muddy shallow-water seagrass beds ( Fig. 7 A) with two dominant species of seagrass: the small sized Thalassia hemprichii (Ehrenberg) Ascherson , and Enhalus acoroides L.C. Rich. ex Steud. , characterized by larger size and very long leaves. The new species is dominant in this habitat. The camouflage coloration of this species is clearly adapted to conceal it within muddy leaf habitats rather than on “clean” green leaves exposed to waves. The species is possibly a scavenger or micropredator. Most specimens were collected in shallow depths of 0.1–0.3 meters in pools at low tide. It is most abundant on seagrass but its affinity to these plants is low. The species also inhabits various substrata, e.g. bush-Like red algae, the gorgonian coral Rumphella sp., or any other suitable substrata—it also was found on a discarded muddy fishnet lying on the bottom at a depth of four meters.

Colouration.—Most specimens are almost fully transparent, with only traces of colouration ( Fig. 7 B– C,E). Adult females are more distinctly coloured ( Fig. 7 D), as follows: general body transparent, eyes grey, cornea with reddish spots, internal organs greyish with indistinct dark and light dots, body irregularly covered by reddish-brown to orange spots, similar spots situated on antennular peduncles, scaphocerites, eyestalks and tail fan, spots locally grouped to irregular transversal lines running antero-ventrally from behind carapace sides, and more densely to transverse bands along posterior margins of abdominal tergites. Indistinct whitishgrey colour present dorsally on the third abdominal segment, more distinct on posterior margins of abdominal segments, and on bases and apices of telson and uropods. The whitish-grey spots on uropodal exopods are almost eye-shaped. Sometimes with transverse lines of spaced whitish dots on abdomen. Egg masses greenish grey.

Etymolog y.—Derived from Latin “sulcus” (furrow) to reflect the specific integumental structures of the anterior abdominal segments dorsum.

Figures

FIGURE 1. Periclimenes sulcatus sp. nov., ovigerous female holotype. A—total view. B—Anterior abdominal segments I – III, lateral view of dorsum, vertical lines indicate borders of segments. Scale bars— 1 millimeter.

FIGURE 2. Periclimenes sulcatus sp. nov., ovigerous female holotype. A, anterior carapace, eye and antennae, lateral view. B, same, dorsal view. C, ventral armament of fourth (top) and fifth (below) thoracic sternites. D, sixth abdominal segment, telson and uropods, dorsal view. Scale bars— 1 millimeter.

FIGURE 3. Periclimenes sulcatus sp. nov., ovigerous female holotype. A, first pereiopod. B, same, chela. C, same, basal articles. D, second pereiopod. E, same, chela. F – H, third to fifth pereiopods, respectively. I – K, same, distal propodus and dactylus. Scale bars— 1 millimeter.

FIGURE 4. Periclimenes sulcatus sp. nov., ovigerous female paratype CL 1.9 mm, RMNH D 51970. A, paragnaths. B, left mandible, medial view. C, same, ventral view. D, right mandible, medial view. E, same, ventral view. F, maxillula. G, maxilla. H, first maxilliped. I, second maxilliped. J, third maxilliped. Scale bar— 1 millimeter.

FIGURE 5. Periclimenes sulcatus sp. nov. A – C, male allotype, D – E, male paratype CL 2.0 mm, authors’ collection. A, total view, lateral. B, first pleopod. C, second pleopod. D, endopod of first pleopod. E, appendix masculina and appendix interna of second pleopod. Scale bars— 1 millimeter.

FIGURE 6. Periclimenes sulcatus sp. nov., authors’collection (OU). A, ovigerous female paratype CL 2.0 mm, total view. B, male paratype CL 1.9 mm, anterior body and appendages. C – I, male paratype CL 1.6 mm: C, lower orbital angle, right side. D, posterior cephalothrax and anterior abdominal segments, left side, arrows indicating the ‘ sulci’ (only anterior ones developed there). E, posterior margin of carapace, dorsal. F, posterior margin of second abdominal segment, dorsolateral. G, posterior sixth abdominal segment, telson and uropod, left side. H, eye, anterolateral wiew. I, accessory pigment spot on eyestalk.

FIGURE 7. Periclimenes sulcatus sp. nov. A, habitat — seagrass Thalassia hemprichii (Ehr.) Asch. (small-sized) and Enhalus acoroides L. C. Rich. ex Steud. B – E, shrimp specimens showing cryptic colouration on muddy seagrass leaves.