Izu Islands.

Izu-ohshima Island. 1 ♂, 1 ♀ (2.7, 4.0 mm CL, NSMT-Cr 15184), Akino-hama, 34°47.2′N, 139°24.5′E, 20 m, 6 Apr 1997, coll. I. Soyama. Hachijo-jima Island. 1 ♂ (2.4 mm CL, CMNH-ZC 01567), Nakano-mama, 33°08.6′N, 139°46.8′E, 20 m, 29 Aug 1996, coll. J. Okuno; 1 ♀ (4.3 mm CL, CMNH-ZC 01668), Kyokucho-hama, 33°09.3′N, 139°46.7′E, 35 m, 6 Oct 2002, coll. J. Okuno and K. Tanaka.

East China Sea coast of Kyushu.

Nagasaki. 1 ♀ (3.0mm CL, CMNH-ZC 01700), 1 ovig. ♀ (5.7 mm CL, RMNH-D 50660), Tatsunokuchi, Koyagi, 32°41.7′N, 129°47.4′E, 15 m, 13 Sep 2003, coll. J. Okuno.

Ogasawara Islands.

1 ♀ (3.8 mm CL, CMNH-ZC 01640), Susaki, Chichi-jima Island, 27°04.3′N, 142°10.7′E, 25 Sep 1994, coll. H. Tachikawa.

Ryukyu Islands. 1 ovig. ♀ (4.6 mm CL, CBM-ZC 7851), Sunabe, Chatan, Okinawa-jima Island, 26°20.1′N, 127°44.5′E, 10 m, 28 Mar 1998, coll. Abe.

Other specimens: 1 ♂ (2.4 mm CL, NFU-530-2-2517), 1 ♂, 2 ♀ ♀ (2.4–2.8 mm CL, NFU-530-2-2518), Uchiura, Suruga Bay, Honshu, Japan, 35°01.5′N, 138°49.3′E, Nov 1974, coll. K. Suzuki.

Diagnosis. — A medium sized pontoniinid shrimp with subcylindrical body form. Carapace with single epigastric spine. Rostrum slender, feebly arched, dentate. Posterior half of third abdominal somite strongly elevated, feebly subcarinate. Ophthalmic somite with distinct interocular beak. Antepenultimate segment of third maxilliped nearly always with 1 distolateral spine. Dactylus and fixed finger of second pereiopod shorter than palm, with cutting edges usually den-tate proximomesially, without proximal concavity on edges. Carpus of second pereiopod distinctly shorter than chela. Ambulatory pereiopods with dactyli slender, distinctly biunguiculate, propodi with set of short spines on ventral surface. In life, tergum of third abdominal somite with rounded large patch, ground color orange, anteriorly covered with numerous red spots, posterodorsally white.

Description. — Carapace (Fig. 1) smooth, glabrous, lacking supraorbital spine; orbit (Fig. 2B) feebly developed, inferior orbital angle strongly produced, acute, with inner ventral flange; antennal spine well developed, slender, sub-marginal, arising distinctly ventral to orbital angle; hepatic spine large, arising slightly ventral to level of antennal spine; epigastric spine present; pterygostomian margin rounded.

Fig. 2.

Periclimenes speciosus sp. nov. Holotype male (CMNH-ZC 01666). A, anterior part of carapace, rostrum and cephalic appendages, dorsal view; B, anterior part of carapace and rostrum, lateral view; C, orbital region of carapace, ophthalmic somite and proximal parts of right antennular peduncle and antenna, lateral view; D, telson and right uropod, dorsal view; E, posterior part of telson, dorsal view; F, right antennular peduncle, dorsal view; G, right scaphocerite, dorsal view. D, G, marginal setae omitted.

Rostrum (Fig. 2B) slender, feebly arched, 0.9–1.0 times as long as carapace, reaching or slightly overreaching level of midlength of distal segment of antennular peduncle; dorsal margin usually with 7–8 (rarely 9) equidistant, small, acute teeth, interspaced by short setae; ventral margin with poorly developed blade, with row of long setae, subterminally with 1–2 (rarely 3) small, acute teeth.

Fourth thoracic sternite without finger-like median process; fifth sternite with pair of semiquadrate lobes posteriorly; posterior sternites unarmed.

Abdomen (Fig. 1) smooth, glabrous; pleura of first to third somites broad, rounded, those of fourth and fifth posteriorly produced, blunt; posterodorsal margin of third somite produced posteriorly, posterior half of tergum with strongly elevated, feebly compressed median carina; sixth somite 1.2–1.4 times as long as carapace, 1.3–1.4 times as long as telson in male, 0.9–1.1 times as long as carapace, 1.1–1.3 times as long as telson in mature female, posterolateral process acute, posteroventral margin produced, acute. Telson (Fig. 2D) tapering posteriorly, posterior margin (Fig. 2E) bluntly produced centrally, with 3 pairs of spines (lateral and intermediate spines simple, intermediate spines longest, submedian spines setulose); 2 pairs of small, subequal dorsolateral spines at midlength and posterior third length respectively.

Ophthalmic somite with distinct, short interocular beak (Fig. 2C). Eye (Fig. 2A) with large, globular cornea, without ocellus; stalk distinctly longer than corneal diameter, becoming slightly narrower distally, maximum width subequal to maximum corneal diameter.

Antennular peduncle (Fig. 2F) with proximal segment distinctly longer than distal two segments combined; disto-lateral margin strongly produced, reaching level of midlength of intermediate segment, with row of setae, lateral margin straight, terminating distally in small acute tooth reaching level of proximal one-fourth of distolateral lobe; ventromesial margin armed with small acute tooth; stylocerite short, slender, acute, reaching level of proximal one-third of proximal segment (distolateral lobe excluded); statocyst well developed, rounded; intermediate segment slender, distinctly less than half of proximal segment in length, slightly obliquely articulated with distal segment; distal segment subequal to intermediate segment in length, slender, non-setose. Upper flagellum biramous, proximal 11 segments fused, shorter free ramus 5–7 segmented; lower flagellum more slender than upper flagellum.

Antenna with stout basicerite (Fig. 2C) armed ventrolaterally with acute tooth, dorsal margin with distinctly raised lobe; scaphocerite (Fig. 2G) reaching distal end of antennular peduncle, 3.1–3.2 times as long as width, lateral margin almost straight, terminating in strong tooth falling short of distal margin of strongly produced lamella; carpocerite falling slightly short of midlength of scaphocerite.

Epistome unarmed.

Mandible (Fig. 3A) robust, without palp; incisor process obliquely truncated distally, with 3 large, acute teeth; molar process stout, distally oblique. Maxillule (Fig. 3B) with feebly bilobed palp, internal lobe with small distal protuberance; upper lacinia broad, curved, distal margin truncated, with about 6 simple spines, interspaced by long setae, ventral margin with 3 short spiniform setae; lower lacinia tapering distally, with some serrulate setae distally. Maxilla (Fig. 3C) with palp slender, tapering distally; distal endite developed, narrow, deeply bilobed, with sparse, simple setae distally; proximal endite obsolete, mesial margin feebly sinuous; scaphognathite well developed, posterior lobe short, distal half of anterior lobe narrow. First maxilliped (Fig. 3D) with long, slender, simple palp; distal endite with mesial margin bearing 2 rows of sparse setae, rounded distally; proximal endite small, rounded, separated from distal endite by shallow notch; caridean lobe broad; exopod with well-developed flagellum; epipod large, subquadrate, feebly bilobed. Second maxilliped (Fig. 3E) with normal endopod; dactylus broad, mesial margin almost straight; propodus with ante-romesial margin bluntly produced; carpus with distinct ventromesial process; merus about twice as long as carpus; ischium and basis completely fused, mesial surface distinctly concave; exopod with well developed flagellum; coxa inflated mesially; epipod oval, without podobranch. Third maxilliped (Fig. 3F) with endopod slender, falling slightly short of midlength of scaphocerite, ischiomerus and basis feebly articulated; ultimate segment tapering distally, ventrally with about 6 transverse rows of short setae, dorsally with sparse setae; penultimate segment 1.2–1.4 times as long as ultimate segment, with sparse long setae ventrally, sparse short setae dorsoproximally, long simple setae dorsodistally; antepenultimate segment nearly always with 1 small distolateral spine, ventral margin sparsely setose; exopod with well developed flagellum, distally with long plumose setae; coxal plate subquadrate; small arthrobranch present.

Fig. 3.

Periclimenes speciosus sp. nov. Holotype male (CMNH-ZC 01666). A, right mandible, ventral view; B, right maxillule, ventral view; C, right maxilla, ventral view; D, right first maxilliped, ventral view; E, right second maxilliped, ventral view; F, right third maxilliped, lateral view. C–E, setae omitted.

Branchial formula agrees quite with those of Periclimenes kobayashii and P. sarasvati (see Okuno and Nomura, 2002; Okuno, 2002).

First pereiopod (Fig. 4A) moderately slender, over-reaching distal margin of scaphocerite by length of dactylus. Chela (Fig. 4B) 0.4–0.5 times as long as carapace, 0.9–1.3 times as long as carpus; palm subcylindrical, slightly compressed, with 4 transverse rows of short serrulate grooming setae proximally; fingers 1.0–1.2 times as long as palm, each terminating in small, hooked unguis, cutting edges situated laterally, unarmed. Carpus 0.4–0.5 times as long as carapace, 1.7–2.6 times as long as palm, slightly widened distally, with longitudinal row of serrulate grooming setae distally. Merus unarmed, 1.1–1.2 times as long as carpus. Coxa with small, setose ventral process.

Fig. 4.

Periclimenes speciosus sp. nov. Holotype male (CMNH-ZC 01666). A, right first pereiopod, lateral view; B, same, chela and posterior part of carpus, mesial view; C, right second pereiopod, lateral view; D, right third pereiopod, lateral view; E, same, propodus and dactylus, lateral view; F, same, dactylus and posterior part of propodus, lateral view; G, propodus and dactylus of right fifth pereiopod, lateral view; H, endopod of right first pleopod, dorsal view; I, right second pleopod, dorsal view, marginal setae omitted.

Second pereiopods (Fig. 4C) well developed, similar, overreaching distal margin of scaphocerite by length of chelae. Chela slightly bowed, 0.8–1.5 times as long as car-apace, 1.7–2.7 times as long as carpus; palm 1.1–1.6 times as long as dactylus, slightly compressed; dactylus (Fig. 6A, B) terminating in hooked, acutely pointed unguis, cutting edge situated laterally, armed proximally with 0–4 (usually 2–3) small, acute, recurved teeth, remaining part entire, sharply edged; fixed finger (Fig. 6A, B) generally similar to dactylus, armed proximally with 0–5 (usually 2–5) small, acute, recurved teeth. Carpus slender, unarmed, slightly widened distally. Merus slender, unarmed, 1.3–1.4 times as long as carpus. Ischium slender, unarmed, 1.1 times as long as carpus.

Third pereiopod (Fig. 4D) slender, overreaching distal margin of scaphocerite by length of dactylus. Merus 1.7–2.6 times as long as carpus, unarmed. Carpus unarmed. Propodus (Fig. 4E) 2.0–2.1 times as long as carpus, with 2 long distoventral and 2 subterminal spines and spaced set of 2 spines on ventral surface, dorsal surface with few short setae. Dactylus (Fig. 4F) about 0.2 of length of propodus, length about 3.6 times as long as basal width, compressed laterally, dorsal margin convex, ventral margin with 1 sub-distal accessory tooth, unguis not clearly demarcated. Fourth pereiopod similar to third. Fifth pereiopod with propodus (Fig. 4G) bearing 1 distoventral and 1 subterminal spines on ventral surface and tufts of setae, and widely spaced set of 2 spines posterior to distal series of spines.

Endopod of male first pleopod (Fig. 4H) short, generally oval, distally expanded, with small, distally acute appendix interna. Endopod of male second pleopod (Fig. 4I) with appendices interna and masculina arising from proximal one-third of mesial margin; appendix interna slender, sub-equal to appendix masculine in length, with few distal cincinnuli; appendix masculina slender, with 6 long spiniform setae distally.

Uropod (Fig. 2D) with protopodite posterolaterally produced, but blunt; exopod broad, overreaching posterior margin of telson, broadly rounded distally, lateral margin nearly straight, terminating in small acute tooth, with smaller or subequal mobile spine just mesial to distolateral tooth; endopod oblong, falling slightly short of posterior margin of exopod.

Coloration (Fig. 5). — Body and appendages generally transparent. Carapace with rostrum transparent, posterodorsal and anterolateral regions with scattered purplish red and white spots. Pleura of first to fourth abdominal somites without spots in male, with purplish red and white oval patches at first to fourth pleura in female; third somite with large dorsal round patch over posterior two thirds, narrower posteri-orly than anteriorly, background white, with many red spots on anterior half (the white background being reduced to a network of pale orange irregular lines between the spots), posterior margin pinkish; posterior sixth abdominal somite and proximal telson and protopodite of uropod purplish red; distal three-fourth of telson white. Eyestalk white, with pale purple stripe anteriorly, ophthalmic somite with white longitudinal stripe anterodorsally. Chelae and carpi of anterior two pereiopods largely white, with hinge regions and tips of fingers purple. Proximal parts of pleopods with purplish red spots. Intermediate regions of uropodal exopod and endopod white, posterior third of endopod lemon yellow, posterior third of exopod with deep purple oval patch.

Fig. 5.

Periclimenes speciosus sp. nov. Holotype male (CMNH-ZC 01666). Fresh specimen, dorsal view.

Sexual dimorphism. — The mature females are larger and more robust than males. The known maximum postorbital carapace length is 6.7 mm in females instead of 4.0 mm in males. The length of sixth abdominal somite of mature females is shorter than that of males (0.9–1.1 times as long as postorbital carapace length vs 1.2–1.4 times as long). In life, the females show white patches on the pleura of first to fourth abdominal somites which are lacking in males.

Derivation of name. — The specific name is derived from the Latin speciosus, meaning brilliant, in reference to the strikingly beautiful coloration in life of the species. The name is an adjective.

Distribution. — Known from warm-temperate and sub-tropical waters of Japan, and possibly from Australia and New Caledonia (see Discussion).

Ecological notes. — Periclimenes speciosus is associated with various taxa of actiniarian and madreporarian anthozoans. The identifiable host species of the present material are summarized as Table 1.

Table 1.

Hosts of Periclimenes speciosus sp. nov.

Moreover, the underwater photograph shown by Minemizu (2000) and observation at Tateyama, Boso Peninsula, Japan by myself indicate that P. speciosus is a fish-cleaner. The process of the cleaning behavior between the shrimp and fishes is generally similar as in the case of P. kobayashii reported by Okuno and Nomura (2002).