Chirostylus ortmanni Miyake & Baba, 1968

Osawa, Masayuki, 2007, A new species of Chirostylus Ortmann, 1892 (Crustacea: Decapoda: Anomura: Chirostylidae) from the Ryukyu Islands, southwestern Japan, with a supplemental description of Chirostylus ortmanni Miyake & Baba, 1968, Zootaxa 1450, pp. 31-43 : 32-36

Chirostylus ortmanni Miyake & Baba, 1968

( Figs. 1 , 2 , 5 A, B)

[Japanese name: Orutoman-waraebi]

Chirostylus ortmanni Miyake & Baba, 1968: 383 , figs. 1c, 3. — Minemizu, 2000: 164, unnumbered fig.; 2002: 164, unnumbered fig. — Kato & Okuno, 2001: 91, unnumbered fig. — Kawamoto & Okuno, 2003: 70, unnumbered fig. — Baba, 2005: 208.

Chirostylus dolichopus . — Miyake, 1982: 143 (part), pl. 48, fig. 1; 1991: 143 (part), pl. 48, fig. 1; 1998: 143 (part), pl. 48, fig. 1. — Takeda, 1986: 125, unnumbered fig.; 1994: 229 (part), fig. 9. — Ogawa & Matsuzaki, 1993: 65, figs. 1, 2. — Asakura, 1995: 368 (part), pl. 98, fig. 6. [Not Chirostylus dolichopus Ortmann, 1892 ].

Type Material. ZLKU 13761, holotype female (cl 6.2 mm), off Okino-shima, Sea of Genkai, northern Kyushu, 90 m, 3 April 1963, coll. K. Sakai and K. Baba. Not available for study.

Material examined. NSMT-Cr 7787, 1 female (cl 6.7 mm), Manazuru, Kanagawa Prefecture, Sagami Bay, May 1981, coll. I. Soyama; NSMT-Cr 8037, 3 males (cl 2.4–6.5 mm), 1 female (cl 6.0 mm), Zyogasaki, Shizuoka Prefecture, Izu Peninsula, 20 m, 6 March 1981, coll. I. Soyama; NSMT-Cr 12523, 1 male (cl 6.0 mm), 1 female (cl 5.8 mm), Osezaki, Shizuoka Prefecture, Izu Peninsula, depth not recorded, 17 April 1975, collector not recorded; NSMT-Cr 11672, 1 ovigerous female (cl 4.9 mm), Sakurajima, Kagoshima Prefecture, 40 m, 1 August 1980, coll. K. Ogawa; NSMT-Cr 11673, 1 ovigerous female (cl 6.0 mm), Himejima, Sukumo, Kouchi Prefecture, 28 m, 14 August 1991, coll. K. Watanabe; NSMT-Cr 11674, 1 female (cl 6.0 mm), Miyake-jima Island, Izu Islands, MJ-1, 10 m, September 1984, coll. Okubo; NSMT-Cr 11675, 1 female (cl 5.8 mm), Miyake-jima Island, Izu Islands, MJ-2, 10 m, 1980–1985, coll. K. Ogawa and K. Matsuzaki; NSMT-Cr 11676, 1 female (cl 5.0 mm), Miyake-jima Island, Izu Islands, MJ-3, 10 m, 1980–1985, coll. K. Ogawa and K. Matsuzaki; NSMT-Cr 11677, 1 female (cl 5.8 mm), Miyake-jima Island, Izu Islands, MJ-4, 10 m, 1980–1985, coll. K. Ogawa and K. Matsuzaki; NSMT-Cr 11678, 1 female (cl 6.1 mm), Miyake-jima Island, Izu Islands, MJ-5, 10 m, 1980–1985, coll. K. Ogawa and K. Matsuzaki; NSMT-Cr 11679, 1 female (cl 3.4 mm), Miyakejima Island, Izu Islands (MJ-6), 10 m, 1980–1985, coll. K. Ogawa and K. Matsuzaki; NSMT-Cr 11680, 1 male, (cl 6.1 mm), Izu Ocean Park, IP-1, 20 m, 25 December 1986, coll. M. Morita; NSMT-Cr 11681, 1 male, (cl 5.0 mm), Izu Ocean Park, IP-2, 20 m, 25 December 1986, coll. M. Morita; NSMT-Cr 11682, 1 female (cl 6.8 mm), Izu Ocean Park, IP-3, 20 m, 25 December 1986, coll. M. Morita; NSMT-Cr 11683, 1 male (cl 7.0 mm), Oshima Island, Kushimoto, Wakayama Prefecture, KP-1, 30 m, 4 April 1987, coll. T. Fukuda; NSMT- Cr 11684, 1 male (cl 4.3 mm), Oshima Island, Kushimoto, Wakayama Prefecture, KP-2, 30 m, 4 April 1987, coll. T. Fukuda; CMNH-ZC 39, 2 males (cl 4.4, 6.1 mm), Off Hasama, Tateyama, Chiba Prefecture, Boso Peninsula, 30 m, 4 July 1998, coll. J. Okuno; CMNH-ZC 531, 1 male (cl 4.1 mm), Igai-jima, Kamogawa, Chiba Prefecture, Boso Peninsula, 16 m, 29 June 2001, coll. J. Okuno; CMNH-ZC 1164, 1 male (cl 4.6 mm), 1 female (cl 5.5 mm), Funatsukiba, Hachijo-jima Island, Izu Islands, depth not recorded, 27 August 1996, coll. J. Okuno; CMNH-ZC 1165, 1 male (cl 4.5 mm), Occhogahama, Hachijo-jima Island, Izu Islands, depth not recorded, 11 September 1997, coll. J. Okuno; CMNH-ZC 1166, 1 female (cl 4.2 mm), Occhogahama, Hachijo-jima Island, Izu Islands, depth not recorded, 11 September 1997, coll. J. Okuno.

Size. Male cl 2.4–7.0 mm, female cl 3.4–6.8 mm, ovigerous female cl 4.9–6.0 mm.

Description. Carapace ( Fig. 1 A–C) 1.1–1.3 times longer than greatest width. Rostrum low, rounded, unarmed or with spine clearly smaller than epigastric spines. Pair of epigastric spines situated behind eyes. Gastric region unarmed. Cardiac region with 1–3 spines in longitudinal row anteriorly. Branchial region unarmed or with 1–5 spines (including 1–4 spines on anterior portion) mesiad and parallel to entire lateral margin or along posterior concavity.

Pterygostomial flaps anteriorly ending in small spine, surface with several small spines.

Excavated sternum ( Fig. 1 D) anteriorly produced, subtriangular, ending in acute tip, surface with weak ridge in midline on anterior half and unarmed or with few minute spines and tubercles on posterior half. Sternite 3 surface ( Fig. 1 E–H) somewhat convex; anterior margin usually with 4 small spines (3 spines in NSMT- Cr 11681, 2 median spines subdivided distally in NSMT-Cr 11684, left spine subdivided distally in CMNH- ZC 39). Sternite 4 ( Fig. 1 E) unarmed or with acute or blunt spine on each proximal lateral margin.

Abdomen unarmed, but with short setae on dorsal surface; pleura of second to fourth segments subtriangular, those of fifth and sixth segments each ending in rounded margin. Telson divided into 2 lobes by indistinct transverse suture; posterior lobe narrower but distinctly longer than anterior, semi-elliptical.

Eyestalk ( Fig. 1 A–C) elongate; cornea slightly dilated.

Antennular peduncle ( Fig. 1 I, J), when fully extended, overreaching distal margin of cornea by distal one third to two thirds length of ultimate article; basal article bearing 2 or 3 spines on distolateral elongate projection, distolateral spine subequal to or larger than distomesial, when 3 spines present, proximal spine smaller than distal 2 spines; ultimate article distinctly longer than penultimate.

Antennal peduncle ( Fig. 1 I) short but slender, article 5 much longer than article 4, barely reaching to slightly overreaching proximal margin of cornea, with ventromesial distal spine.

Third maxilliped ( Fig. 1 D, K) slender; ischium with well developed crista dentata of 14–20 acute teeth; merus and carpus each bearing distolateral spine; propodus unarmed; exopod reaching 0.5–0.7 length of merus.

P1 ( Fig. 2 A, B) slender, 9.7–12.6 times as long as postorbital carapace. Merus longer than carpus and propodus, with 4 rows of sparse spines (1 dorsolateral, 1 dorsomesial, 1 mesial, and 1 ventral). Carpus with 4 rows of sparse spines (1 dorsolateral, 1 dorsomesial, 1 mesial, and 1 ventral). Palm 2.5–3.3 times longer than dactylus (movable finger), with 6 rows of sparse spines (1 dorsolateral, 1 ventrolateral, 1 lateral, 1 dorsomesial, 1 ventromesial, and 1 mesial). Opposable margins of fingers each with prominent tooth proximally and subtriangular, moderate-sized tooth on distal 0.3; median margin gaping, with row of small teeth; distal end with 2 unequal corneous spines.

P2–4 ( Fig. 2 C–F) long and slender, somewhat depressed lateromesially, subequal in length (meri successively diminishing in size posteriorly, propodi longer on P4 than on P2 and P3); P2 barely reaching to slightly overreaching distal margin of P1 carpus. Each merus with lateral surface bearing few spines; mesial surface unarmed or with few spines. Each carpus with extensor margin bearing row of closely-spaced spines in proximal part with few scattered spines beyond; lateral and mesial surfaces and flexor margin unarmed or with few spines. Each propodus narrower than merus and carpus in lateral view, 1.1–1.2 (mean, 1.1, on P2 and P3) and 1.1–1.3 (mean, 1.2, on P4) times as long as carpus, 6.0–8.1 (mean, 6.8, on P2), 5.8–7.8 (mean, 6.6, on P3), and 6.0–8.8 (mean, 7.3, on P4) length of dactylus, 12.3–15.3 (mean, 13.7, on P2), 12.3–16.8 (mean, 14.5, on P3), and 14.3–18.5 (mean, 16.1, on P4) times longer than proximal height; extensor margin with row of sparse spines; lateral and mesial surfaces unarmed or with few spines; flexor margin with row of 15–22 (P2 and P3), or 14–19 (P4) slender, corneous spines, distal spines closely arranged. Each dactylus with moderately curved extensor margin; flexor margin nearly straight, with 7–10 (P2), 6–10 (P3), and 6–9 (P4) corneous spines (including terminal spine) gradually decreasing in size toward base of article, distal 2 spines equal or subequal in length, ultimate spine equally broad as or somewhat narrower than penultimate.

Coloration ( Fig. 5 A, B). Body and pereopods with ground color of reddish brown. Carapace with moderately narrow, white or pale yellow line in large triangle bordered by dark brown, narrow lines; yellow line present along lateral margin; part between white and yellow lines and gastric and cardiac regions occasionally with white marks of irregular size. Abdominal tergites with dark brown and yellow, narrow lines along anterior and posterior margins and with moderately broad, dark brown line bordered by yellow, narrow lines along midlline. Pterygostomial flaps each with 2 narrow, longitudinal white stripes. P1 merus with longitudinal rows of small, closely-set, yellow spots; carpus and chela with longitudinal narrow, yellow stripes. P2–4 meri each bearing white or pale blue, blotch or band bordered by dark brown bands near distal end and longitudinal row of small yellow spots on remaining part (bases of spines) of extensor margin; carpi each with longitudinal yellow stripes; propodi dark brown with yellow tinge on distal part; dactyli yellow.

Distribution. Known only from Japan; Boso Peninsula of Honshu mainland to Satsuma Peninsula of southern Kyushu, and Izu Islands. The holotype was collected from off Okino-shima, northern Kyushu, at a depth of 90 m ( Miyake & Baba 1968). The specimens examined were obtained at depths of 10– 40 m.

Habitat and ecology. This species is found on soft and black corals (Alcyonacea and Antipatharia) or sponges ( Minemizu 2000, 2002; Kato & Okuno 2001).

The ecology of C. ortmanni (as C. dolichopus ) is noted in detail by Ogawa & Matsuzaki (1987). The authors suggested that the lifespan of the female is about one year based on the rearing under laboratory conditions.

Remarks. The holotype of Chirostylus ortmanni was not available for study. The specimen was previously deposited in the Zoological Laboratory, Faculty of Agriculture, Kyushu University (ZLKU), and now is supposedly transferred to the Kitakyushu Museum of Natural History and Human History, together with numerous crustacean specimens described by Dr. S. Miyake and his co-workers. However, the attempt to find the holotype of C. ortmanni in the collection of the museum was not successful (Dr. M. Shimomura; personal communication).

The morphology of the specimens examined in this study agrees well with the original description of C. ortmanni by Miyake & Baba (1968) in most diagnostic aspects. The above description complements their account of the species. Miyake & Baba (1968) also mentioned that their live specimen of C. ortmanni had two reddish orange bands on the distal portions of the P2–4 meri. This characteristic marking is distinct in the photograph of a live specimen shown by Minemizu (2000, 2002) and was also confirmed in the specimens examined from Boso Peninsula and Hachijo-jima Island.

Osawa & Nishikiori (1998) concluded that the specimens identified as C. dolichopus (NSMT-Cr 11672– 11686) by Ogawa & Matsuzaki (1993) are referable to C. ortmanni . The specimens were re-examined for the above description and support their conclusion. Accurate identification of a specimen from Aka-jima Island in the Ryukyus (cl 1.6 mm, NSMT-Cr 11686) is difficult since it is a juvenile. Judging from its locality, the specimen probably belongs to C. stellaris n. sp., described below.

Specimens in color photographs identified by Miyake (1982, 1991, 1998), Takeda (1986, 1994), and Asakura (1995) as C. dolichopus can be referred to C. ortmanni . They all have the color pattern characteristic of C. ortmanni . The illustration of C. dolichopus shown by Miyake (1960, pl. 48, fig. 8) also seems to agree with the coloration of C. ortmanni . However, Miyake and Baba (1968: 383) noted that “The coloration and some characters of the present material (of C. dolichopus ) are previously shown by Miyake (1960) ”. The correct specific identification of Miyake’s (1960) specimen is difficult without re-examination. The morphological distinctions between C. dolichopus and C. ortmanni are cited in key to species of the genus provided by Osawa & Nishikiori (1998) and Baba (2005).

Figures

FIGURE 1. Chirostylus ortmanni Miyake & Baba, 1968. NSMT-Cr 8037, male (cl 6.5 mm), Zyogasaki, Shizuoka Prefecture (A, D, E, I, K); NSMT-Cr 11681, male, (cl 5.0 mm), Izu Ocean Park (B, G, J); NSMT-Cr 11678, female (cl 6.1 mm), Miyake-jima Island, Izu Islands (C); NSMT-Cr 11682, female (cl 6.8 mm), Izu Ocean Park (F); NSMT-Cr 11684, male (cl 4.3 mm), Kushimoto, Wakayama Prefecture (H). A – C, carapace and ocular peduncles, dorsal view; D, anterior part of sternal plastron, including proximal parts of maxillipeds, ventral view; E, sternites 3 and 4, ventral view; F – H, anterior margin of sternite 3, ventral view; I, left ocular, antennular, and antennal peduncles, ventral view; J, basal article of left antennular peduncle, ventral view; K, carpus, merus, and distal part of ischium of right third maxilliped, lateral view. Scales equal 1.0 mm.

FIGURE 2. Chirostylus ortmanni Miyake & Baba, 1968. NSMT-Cr 8037, male (cl 6.5 mm), Zyogasaki, Shizuoka Prefecture (A, B); NSMT-Cr 11678, female (cl 6.1 mm), Miyake-jima Island, Izu Islands (C, D); CMNH-ZC 531, male (cl 4.1 mm), Kamogawa, Chiba Prefecture (E); NSMT-Cr 7787, female (cl 6.7 mm), Manazuru, Kanagawa Prefecture (F). A, ischium and merus of left P 1, mesial view; B, chela of left P 1, dorsal view; C, carpus, propodus, and dactylus of right P 2, lateral view; D – F, dactylus and distal part of propodus of right P 2, lateral view. Scales equal 1.0 mm.

FIGURE 5. Fresh specimens. Chirostylus ortmanni Miyake & Baba, 1968, CMNH-ZC 531, male (cl 4.1 mm), Kamogawa, Chiba Prefecture (A, B); Chirostylus stellaris, n. sp., CMNH-ZC 0 1115, paratype male (cl 4.1 mm), Kumejima Island, Ryukyu Islands (C, D); CMNH-ZC 2130, paratype female (cl 3.3 mm), Zanpa-misaki, Okinawa Island, Ryukyu Islands (E, F). A, C, entire specimen, dorsal view; B, D, carapace, abdomen, and meri of pereopods, dorsal view; E, F, live specimen in aquarium. Photographed by J. Okuno (A – D) and Y. Fujita (E, F).