Periclimenoides socotrae, Bruce, A. J., 2006

Bruce, A. J., 2006, Pontoniine shrimps (Decapoda: Palaemonidae) from the island of Socotra, with descriptions of new species of Dactylonia Fransen, 2002 and Periclimenoides Bruce, 1990, Zootaxa 1137, pp. 1-36 : 22-29

Periclimenoides socotrae sp. nov.

Figures 6–9

Diagnosis: Rostrum with 5 dorsal, 1 distoventral tooth, supraorbital teeth or tubercles absent, first abdominal tergite without anterior lobe, scaphocerite normal, with small distolateral tooth not exceeding lamella, first pereiopods with fingers subequal to palm, slender, spatulate, non­denticulate, second pereiopods slightly unequal and similar, chelae smooth, fingers simple, cutting edges finely denticulate, merus ventrally tuberculate, chela with dactyls elongate, fixed finger with cutting edge longitudinally grooved, third pereiopod with unguis short, stout, ventrally laminate, corpus with larger bluntly curved distal accessory tooth only, propod with three robust distoventral spines only, merus unarmed, uropodal exopod with distolateral tooth and spinule only, telson with normal dorsal spines at about 0.3 and 0.7 of telson length, with 3 pairs of normal posterior spines.

Material examined. (1) 1 ovig.Ψ, holotype, MAP­060, ST­016, 12°40.264’N 53°27.204’E, SW of Qualansiyah, NW­coast, 5–7 m, 8 March 1999, reg N o. SMF 29114. (2) 1 ovig.Ψ, paratype (dissected), MAP­137, ST­067, 12°40.429’N 54°11.731’E, Rhyi

di Hamri, E of Hawlaf, N coast, 7–9 m, 19 March 1999, reg No. SMF 29115.

Description: Medium sized pontoniine shrimp of stout subcylindrical body form.

Female. Carapace: ( Figure 6 A) smooth, compressed, without epigastric or hepatic spines, supraorbital spines or tubercles.

Rostrum: ( Figure 6 B) about 0.4 of carapace length, reaching to about middle of intermediate segment of antennular peduncle, slightly exceeding anteroverted corneal margin, slender, compressed, horizontal, with five slender acute subequal dorsal teeth, with sparse plumose interdental setae, first tooth situated anterior to postorbital notch, without distinct lateral carinae, inferior margin convex, with small acute distal tooth, slightly in advance of first dorsal tooth in holotype, slightly more posteriorly in paratype, non­setose, inferior orbital angle obsolete, antennal spine acute, marginal, anterolateral margin of branchiostegite slightly produced, broadly rounded.

Abdomen: well developed, swollen, first segment without median anterodorsal lobe, sixth segment short, about 0.25 of carapace length, subequal to length of fifth, length subequal to depth, depressed, with acute posterolateral and posteroventral angles ( Figure 6 I), pleura of first three segments large, broadly rounded, fourth and fifth small, rounded, feebly produced.

Telson: ( Figure 6 J) about 0.65 of CL, about twice as long as maximal width, near anterior margin, lateral margins feebly convex and posteriorly convergent, with two pairs of small submarginal dorsal spines at about 0.3 and 0.7 of length, anterior pair stouter than posterior pair, about 0.05 of telson length, posterior spines smaller, posterior margin ( Figure 8 I) broadly convex, without median point, about 0.5 of maximal width, with three pairs of spines, lateral spines small, about 0.3 of intermediate spine length, intermediate spines robust, about 0.22 of telson length, submedian spines slightly shorter and more slender than intermediate spines, sparsely setulose.

Antennule: ( Figure 6 C) with peduncle short, well exceeding carpocerite and rostrum, proximal segment about two times longer than greatest width, lateral margin feebly concave, bluntly angular proximally, tapering slightly distally, with small acute distolateral tooth, ventromedial margin with small acute tooth at 0.5 of length, stylocerite short, acute, reaching to about 0.4 of segment length, statocyst normal, with small granular statolith; intermediate and distal segments short, robust, subequal, together about 0.6 of proximal segment length; flagella short, upper flagellum biramous, proximal four segments of rami fused, stout, subequal to length of distal peduncular segments, short ramus single segmented, with about eight groups of aesthetascs extending along whole length of short fused ramus, longer ramus with five plus segments, lower flagellum simple, with about 12 slender subcylindrical segments, subequal to CL.

Antenna ( Figure 6 D)) short, with carpocerite reaching to distal margin of intermediate segment of antennular peduncle; basicerite normal, unarmed, antennal gland aperture not discernible,; carpocerite subcylindrical, 5.5 times longer than distal width, distinctly exceeding scaphocerite; flagellum short, reaching to about posterior carapace margin. Scaphocerite: normal, distinctly shorter than carpocerite, about 2.6 times longer than wide, maximal width distally at about level of distolateral tooth, broadening distally, lamella distally broadly rounded, lateral margin straight with short stout acute tooth distally, falling distinctly short of distal margin of lamella.

Eye ( Figure 6 E)) with cornea hemispherical, well pigmented, oblique, diameter about 0.18 of CL, without accessory pigment spot, stalk subcylindrical, swollen, medially flattened, about 1.2 times longer than wide.

Mouthparts: closely similar to Periclimenoides odontodactylus (Fujino & Miyake, 1968) . Mandible: right, ( Figure 6 F) with incisor process ( Figure 8 A) slender, with 2 small acute teeth distally, proximal tooth smaller and less acute than distal, molar process lost in dissection; without palp. Maxillula: ( Figure 6 G) with short feebly bilobed palp ( Figure 8 C), lower lobe with single slender simple seta; upper lacinia broad ( Figure 8 C) as long as wide, distally convex with five acute non articulated teeth ( Figure 8 D) and sparse simple setae.

Third maxilliped: ( Figure 6 H) reaching to about distal border of scaphocerite, ischiomerus and basis completely fused; with small arthrobranch.

Thoracic sternites: narrow, unarmed, broadening posteriorly.

First pereiopod: ( Figure 7 A) normal, neither long nor short, slender, exceeding proximal segment of antennular peduncle by carpus and chela; chela ( Figure 7 B) with palm about 1.9 times longer than deep, compressed, dorsal margin feebly convex, ventral border straight, sparsely setose, fingers slender, feebly spatulate, with several groups of short setae, dactylus about 0.7 of palm length, straight, 4.0 times longer than basal width, tapering strongly to slightly dilated tip with single small acute hooked tip ( Figure 8 E), cutting edges straight, sharp, entire, fixed finger similar to dactylus, two times longer than basal width, cutting edge sharp, entire, tip with small hooked tooth; carpus 1.25 times chela length, about 6.0 times longer than central width, tapering proximally; merus moderately slender, 6.0 times longer than central width, situated at 0.5 of length, tapering distally and proximally, about 1.1 times carpus length, unarmed; ischium short, 0.45 of merus length, robust, unarmed; basis and coxa short, stout, without special features, coxa without ventral process.

Second pereiopods: slightly unequal in length and similar in shape ( Figure 7 D) well developed, both present in holotype, one only in paratype female. Major pereiopod: (holotype) chela ( Figure 7 C) about 1.28 times CL, 1.15 times minor chela length, palm about twice as long as deep, slightly compressed, tapering distally, smooth, glabrous, fingers with cutting edges finely denticulate, dactylus about 0.4 of palm length, about three times longer than deep, compressed, distally acute, with tip extending well beyond fixed finger, with low acute tooth at about half length, fixed finger grooved, without molar process and fossa, with proximal tooth. Minor (?) pereiopod: (female paratype) ( Figure 7 D) smaller, about 1.2 of CL, chela with palm glabrous, subcylindrical, slightly compressed, 2.5 times longer than deep, slightly swollen proximally, fingers ( Figure 7 F, 5A) about 0.38 of palm length, dactylus ( Figure 7 G) compressed, distinctly overreaching fixed finger, three times longer than deep, dorsal margin moderately convex, with feebly blunt tip, cutting edge concave, finely denticulate, with about 25 low subacute denticles (damaged in dissection), decreasing in size proximally, with fixed finger about two times longer than basal width, with subacute feebly hooked tip, cutting edge with distal half finely denticulate as on dactylus, proximal half grooved, lateral ridge with long low tubercle ( Figure 9 C) bearing numerous minute acute conical denticles, medial ridge ( Figure 9 B) similar, with more acute tuberculate tooth; carpus articulating preterminally with propod, about 0.4 of palm length, 1.5 times longer than distal width, tapering strongly proximally, distally excavate, unarmed; merus about 0.5 of palm length, two times longer than central width, tapering slightly distally, ventral margin with five small acute tubercles; ischium subequal to meral length, 2.6 times longer than distal width, tapering strongly proximally, unarmed; basis and coxa robust, without special features.

Third pereiopod: ( Figure 7 E) exceeding basicerite by carpus, propod and dactyl; dactylus ( Figure 8 H) about 0.2 of propod length, with unguis distinctly demarcated, short, stout, subconical with ventomedial laminar flange, with minute strongly hooked styliform tip, about 0.2 of corpus length, about as long as basal width; about 1.5 times longer than deep, corpus strongly compressed, dorsal border feebly convex, ventral margin with stout blunt curved tooth distally, otherwise unarmed, sharp ventrally, with single distolateral sensory seta only; propod ( Figure 7 F) about 0.4 of CL, compressed, sparsely setose, 5.0 times dactylus length, 3.6 times longer than maximal width, situated at 0.25 of length, tapering distally, distal width about 0.6 of maximal width, ventral border straight, with stout lateral, ventral and medial distoventral spines, distomedial spine twice length of other spines, about 0.8 of corpus length, ventral border straight, unarmed; carpus 0.95 of propod length, swollen, 2.3 times longer than maximal width, tapering proximally, unarmed; merus robust, about 1.2 times propod length, 2.3 times longer than central width, compressed, tapering proximally and distally, unarmed; ischium equal to 0.9 of propod length, 2.1 times longer than distal width, tapering proximally; basis and coxa robust, without special features.

Fourth pereiopod ( Figure 7 G) generally similar to third, more slender, dactylus ( Figure 9 D), about 0.9 of third propod length, 4.0 times longer than wide, propod with three similar distoventral spines, carpus about 0.75 of third carpus length, more slender, 2.7 times longer than wide, merus 0.9 of third merus length, 3.2 times longer than wide, propod (Figurer 3J) about 0.37 of carapace length.

Fifth pereiopod ( Figure 7 H) more slender, dactylus ( Figure 9 E) similar to third pereiopod, propod about 0.45 of carapace length, 1.1.times third pereiopod propod length, subuniform, 5.7 times longer than wide, ventral margin with numerous slender spiniform setae distally, without spines.

Uropod ( Figure 6 K) with protopod unarmed posterolaterally; exopod broad, about 1.9 times longer than wide, lateral margin convex, sparsely setose, unarmed, with small acute distolateral tooth, with larger mobile spine medially, not reaching level of distal border of exopod, without distinct diaeresis; endopod 1.1 times exopod length, 2.6 times longer than broad, slightly exceeding endopod.

Ova : moderately numerous, about 40 (paratype), 60 (holotype), small.

Measurements (mm): Female holotype: total body length (approx.) 16.0; carapace length 3.5; carapace and rostrum 5.8; second pereiopod, major chela, 4.5; minor chela, 3.9; length of ovum, 0.55. Paratype: CL 2.5.

Host and colouration: Unknown.

Systematic Position: Periclimenoides socotrae is closely related to the only other species of the genus, P. odontodactylus (Fujino & Miyake, 1968; cf. Bruce, 1990) and does not require any major modification to the generic definition other than that the rostrum may have a ventral tooth and the ambulatory dactylus may be simple or biunguiculate. The unusual bidentate incisor process is confirmed as a generic character.

Periclimenoides socotrae may be distinguished from P. odontodactylus by the following features:

Remarks: The second pereiopods were left attached to the holotype and not removed for examination. The delicate denticulate cutting edges of the fingers of the paratype were damaged in the course of examination and the rigid dactyls of the holotype indicated that further examination would result in extensive damage to the specimen.

The type specimen of Periclimenoides odontodactylus was found in association with the sponge Ircinia fasciculatas (Pallas) (Fujino & Miyake, 1968) . The present species probably has a similar association.

Periclimenoides odontodactylus , type locality Ushibuka, Amakusa Island, Kyushu, Japan, is also known from Hong Kong ( Bruce, 1990), Philippine Islands ( Chace & Bruce, 1993), Western Australia and Queensland ( Bruce, 1981a, 1983a), to depths of 38 m, and has not as yet been found in the western Indian Ocean.

Figures

FIGURE 6. Periclimenoides socotrae sp. nov. (A), carapace and rostrum. (B), rostrum. (C), antennular peduncle. (D), antennal peduncle. (E), eye. (F), mandible. (G), maxillula, lacking lower lacinia. (H), third maxilliped. (I), fifth and sixth abdominal segments, lateral. (J), telson. (K), uropod. (A – H, J), ovigerous female paratype, (I), ovigerous female holotype.

FIGURE 7. Periclimenoides socotrae sp. nov. (A), first pereiopod. (B), same, chela. (C), major second pereiopod, chela, holotype. (D), minor second pereiopod. (E), third pereiopod. (F), same, propod and dactyl. (G), fourth pereiopod. (H), fifth pereiopod. (AB­D­J), ovigerous female paratype, (C), ovigerous female holotype.

FIGURE 8. Periclimenoides socotrae sp. nov., paratype. (A), mandible, incisor process. (B), maxillula, palp. (C), same, upper lacinia. (D), same, cutting edge. (E), first pereiopod, tips of fingers. (F), minor second pereiopod, fingers. (G), same, dactylus. (H), third pereiopod, distal propod and dactylus, medial aspect. (I), telson, posterior spines: inset above, dorsal spines, anterior spine, right; posterior spine, left.

FIGURE 9. Periclimenoides socotrae sp. nov., paratype. (A), minor second pereiopod, tips of fingers. (B), same, proximal cutting edge of fixed finger, medial ridge. (C), same, lateral ridge. (D), fourth pereiopod, distal dactylus. (E), fifth pereiopod, distal propod and dactylus.