Heptacarpus camtschaticus Stimpson 1860

Heptacarpus camtschaticus (Stimpson, 1860)

(Figs 1–4, 18, 19)

Hippolyte camtschatica Stimpson, 1860: 102 [type locality: not specifically indicated].

Spirontocaris camtschatica. – Rathbun, 1899: 556; 1904: 94, fig. 42.

Eualus camtshatica [sic]. – Brashnikov, 1907: 164, fig. 22a, b; Kobjakova, 1937: 117.

Eualus camtschatica. – Derjugin & Kobjakova, 1935: 142 (list); Kobjakova, 1936: 211, Makarov, 1941: 127; Kobjakova, 1958: 224.

Spirontocaris camtchatica [sic]. – Urita, 1942: 26.

Heptacarpus camtschaticus. – Holthuis, 1947: 12 (list); Squires & Figueira, 1974: 12; Butler, 1980: 217, unnumbered fig.; Haynes, 1981: 434, fig. 8 (first zoea); 1985: 277; Jensen, 1987: 399 (key); Williams et al., 1989: 17 (list); Wicksten, 1990: 594 (key); Komai, 1994: 82; Chace, 1997: 44 (list); Ivanjushina, 1997: 197; Andrianov & Kussakin, 1998: 264 (list); Minemizu 2000: 92, unnumbered fig.

Heptacarpus camtschatica. – Vinogradov 1950: 210, pl. 16, fig. 67A, B.

Not Spirontocaris camtschatica [= Heptacarpus acuticarinatus n. sp.]. – Balss, 1914: 44; Parisi, 1919: 47; Yokoya 1933: 26.

Not Heptacarpus camtschaticus [= Heptacarpus acuticarinatus n. sp.]. – Liu, 1963: 237; Hayashi & Miyake, 1968: 134, fig. 6; Kikuchi & Miyake, 1978: 24 (list); Hayashi, 1979: 14 (?part); Kojima & Hanabuchi, 1981: 45 (list); Ohta, 1983: 230 (list); Hayashi, 1992: 180, figs 223a, 224a, 225a; Liu & Zhong, 1994: 559 (list); Cha et al., 2001: 90 –91.

Not Heptacarpus camtschaticus [= Heptacarpus longirostris (Kobjakova, 1936)]. – Igarashi, 1971: 2, pl. 2, fig. 4.

Type material. Presumably no longer extant (Evans, 1967).

Material examined. Alaska. USNM 13177, 1 female (cl 6.8 mm), Cape Lisburne, 9–12.6 m, coll. W. Dall; USNM 27693, 3 females (cl 6.5–7.3 mm), Belkofskyi Bay, 27–45 m, 1880, coll. W. Dall. Aleutian Islands. USNM 13191, 1 ovigerous female (cl 8.5 mm), off station reef, Iliuliuk Harbor, Unalaska, 5.4 m. Kamchatka Peninsula. USNM 13491, 3 males (cl 5.2–5.3 mm), 1 ovigerous female (cl 7.5 mm), 1 juvenile (cl 3.3 mm), Rakovaya Bay, Avacha Bay, coll. L. Stejneger; ZISP, 2 females (cl 6.6, 8.2 mm), "Alatyr", stn 429, western Kamchatka, 23 m, gravel, 22 August 1963, coll. A. Neyman. Kurile Islands. ZISP 2/33569, Matsuba Bay, Shikotan Island, 19.5–25 m, 18 September 1949, dredge No. 23, coll. E. F. Gurjanova, 1 male (cl 6.8 mm); ZISP no number, 1 female (cl 6.8 mm), off Veslo Peninsula, Kunashir Island, 7–8 m, sea grass bed of Zostera asiatica, 6 August 1969, coll. Pushkin. Sakhalin. CBM-ZC 2412, 2 females (CL 7.0, 7.0 mm), Lebyazhiya Bay, 10 m, 31 July 1995, beam trawl, coll. M. Yabe. Japan. Hokkaido. CBM-ZC 92, 1 male (cl 4.6 mm), 3 females (cl 7.1–7.9 mm), off Usujiri, Minami Kayabe, 15–25 m, 11 June 1993, dredge, coll. F. Muto; CBM-ZC 270, 3 females (cl 6.0– 7.1 mm), same locality, 15–30 m, 19 August 1993, dredge, coll. F. Muto; CBM-ZC 2433, 1 female (cl 7.1 mm), RV Tansei-maru, KT95-13 cruise, stn 2, Nemuro Bay, eastern Hokkaido, 43°29.8’N, 145°31.6’E, 23 m, sand bottom, 15 September 1995, beam trawl, coll. T. Komai; CBM-ZC 5495, 1 male (cl 4.0 mm), off Usujiri, 20–25 m, 8 October 1991, dredge, coll. T. Komai; CBM-ZC 8602, 1 male (cl 5.4 mm), 3 females (cl 6.2–6.5 mm), same locality, 4 July 1992, dredge, coll. T. Komai; CBM-ZC 8599, 13 males (cl 4.0– 5.9 mm), 18 females (cl 5.4–8.1 mm), same locality, 13 November 1992, coll. T. Komai; HUMZ-C 1179, 1 female (cl 6.5 mm), off Irifune, Hakodate, Hakodate Bay, southern Hokkaido, depth unknown, 19 November 1990, small beam trawl, coll. T. Komai; HUMZ-C 2138, 1 female (cl 8.1 mm), off Usujiri, 20–30 m, 2 July 1991, dredge, coll. T. Komai; HUMZ-C 2158, 1 ovigerous female (cl 8.6 mm), same locality, 25 m, 23 April 1993, dredge, coll. F. Muto. Prymorie. ZISP, 1 female (cl 6.2 mm), Stark’s Strait, Peter the Great Bay, 4 August 1979, sea grass meadow, coll. L. V. Mikulich. Exact locality unknown. ZISP 41392-1, Pacific Ocean, dredge 91-95, 1 female (cl 6.3 mm).

Description of females. Body (Fig. 1) moderately slender for genus; integument naked, glabrous, not particularly firm. Rostrum (Figs 1, 2 A, B) straight, directed forward or slightly ventrad, styliform, slightly falling short of or reaching beyond distal margin of antennal scale, 1.03–1.43 length of carapace; dorsal margin armed with 5 or 6 teeth including 3–5 on rostrum proper and 1 or 2 on carapace, posteriormost tooth arising from 0.14–0.16 of carapace length, distal 0.28–0.59 of dorsal margin unarmed; ventral blade moderately deep, deepest at slightly proximal to midlength of rostrum; ventral margin with 4–7 (most frequently 5 or 6) teeth; teeth subequal or slightly unequal in size except for tiny distalmost tooth; lateral carina blunt. Carapace (Figs 1, 2 A, B) with postorbital rostral ridge low, not extending to anterior 0.25 of carapace length; dorsal margin in lateral view straight; no postorbital tooth; antennal tooth moderately small; suborbital lobe (Fig 2 C) conspicuous, rounded, constricted at base, reaching or slightly overreaching antennal tooth; pterygostomial angle unarmed or armed with tiny tooth.

Pleon (Fig. 1) dorsally rounded, weakly gibbous. Second somite with faint transverse groove on tergite. Dorsal surface of third tergite convex posteriorly, posterodorsal margin strongly produced and partially overhanging anterior part of fourth tergite. Pleura of anterior 4 somites broadly rounded, fifth pleuron with small posteroventral tooth; posterolateral margin of fifth pleuron slightly sinuous. Sixth somite 1.65–1.80 times longer than fifth somite and 1.90–2.10 times longer than high, bearing small posteroventral tooth; posterolateral process terminating in acute tooth. Telson (Fig. 2 D) about 1.20–1.30 length of sixth somite, 3.40–3.70 times longer than wide, lateral margins parallel in anterior 0.35, and then tapering posteriorly, armed with 3–6 (usually 4 or 5) dorsolateral spines on either side; posterior margin (Fig. 2 E) with 1 tiny median tooth and 3 pairs of spines, mesial pair smaller than 2 lateral pairs, bearing marginal setules.

Eye-stalk (including cornea) (Fig. 2 B) generally subpyriform; cornea slightly wider and subequal in length to remaining part of eye-stalk; ocellus distinct, showing as black spot; maximal diameter of cornea 0.15–0.17 of carapace length.

Antennular peduncle (Fig. 2 B) slightly falling short of midlength of antennal scale. First segment distinctly longer than distal 2 segments combined, unarmed on dorsodistal margin; stylocerite overreaching distal margin of first segment, rather abruptly tapering to sharp point, mesial margin convex, closely in touch with first segment; second segment about 0.30 length of first segment, with large spine at dorsolateral distal angle; third segment short, with moderately large spine on dorsodistal margin. Lateral flagellum with thickened aesthetasc-bearing portion 0.35–0.37 of carapace length.

Antenna (Fig. 2 B, F) with basicerite bearing moderately large ventrolateral distal tooth; carpocerite reaching 0.30 length of antennal scale or distal margin of second segment of antennular peduncle. Antennal scale 0.88–1.18 of carapace length and 3.40–4.00 times longer than wide; lateral margin nearly straight; distal lamella rounded, strongly produced, considerably exceeding beyond distolateral tooth.

Third maxilliped (Figs 1, 3 A) moderately stout, reaching distal 0.30–0.40 of antennal scale; ultimate segment about 2.40 length of carpus (= penultimate segment), tapering distally, with several darkly pigmented corneous spines distally; antepenultimate segment subequal in length to distal 2 segments combined, with long, slender spine on distolateral margin, lateral surface rounded, with scattered tufts of short setae.

First pereopod (Fig. 3 B) moderately stout, not reaching midlength of antennal scale; chela (Fig. 3 C) 1.40– 1.50 of carpal length; dactylus about half length of palm, terminating in 2 darkly pigmented, strong corneous ungues (Fig. 3 D); fixed finger terminating in single corneous unguis (Fig. 3 D); merus about 1.40 of carpal length, about 3.00 times longer than high; dorsolateral distal angle of ischium with tiny denticle. Second pereopods (Fig. 3 E) equal, slightly falling short of distal margin of antennal scale; dactylus about 0.60 of palm length; carpus about 4.00 times longer than chela, divided in 7 unequal articles; ischium slightly longer than merus, with few spiniform setae subproximally on ventral margin. Third to fifth pereopods moderately long and slender, slightly decreasing in length posteriorly. Third pereopod (Fig. 3 F) falling somewhat short of distal margin of antennal scale; dactylus (Fig. 3 G) about 0.25 of propodal length, about 2.50 times longer than deep, terminating in acute, pigmented unguis, armed with 5 or 6 accessory spinules notably increasing in size distally and also pigmented; propodus with 2 rows of slender spinules on ventral margin (Fig. 3 G); carpus 0.45–0.50 of propodal length; merus 7.50–8.50 times longer than high, armed with 3–5 spines decreasing in length proximally; ischium unarmed. Fourth pereopod (Fig. 3 H) reaching distal 0.20–0.25 of antennal scale; merus with 2–5 (usually 3 or 4) spines on lateral surface ventrally. Fifth pereopod (Fig. 3 I) reaching midlength of antennal scale; propodus with tufts of grooming setae distally (Fig. 3 J); merus with 2–4 (usually 3) spines on lateral surface ventrally.

Gill formula as in Table 1. Only third maxilliped with strap-like epipod corresponding to setobranch on first pereopod; no epipods on pereopods, and thus no corresponding setobranchs on second pereopod and thereafter.

Pleopods typical of genus; ventrolateral lobe of protopods expanded in spawning molt; endopod of first pleopod subtriangular, without appendix interna. Uropod (Fig. 1) with both rami slightly overreaching posterior margin of telson.

Description of male. Body more slender than in females (Fig. 4 A, C). Rostrum (Fig. 4 B) 1.22–1.42 length of carapace, anterior 0.28–0.53 unarmed. Third pleonal tergite more strongly convex than in females (Fig. 4 C). Corneal diameter about 0.20 of carapace length (Fig. 4 A). Outer flagellum of antennule (Fig. 4 A) larger than in females, thickened aesthetasc-bearing portion about half length of carapace. Antennal scale 0.98–1.21 times longer than carapace. Third to fifth pereopods less stout than in females. Meri of third to fifth pereopods armed with 3 or 4 (rarely 5) spines, 3 or 4 (rarely 2) spines and 3 (rarely 2) spines, respectively. Endopod of first pleopod (Fig. 4 D) elongate subtriangular, with conspicuous appendix interna at terminal position; distolateral lobule not differentiated; mesial margin with row of small spiniform setae, lateral margin with row of long plumose setae. Second pleopod with appendix masculina (Fig. 4 E) slightly shorter than appendix interna, with numerous long setae on dorsal surface to tip.

Coloration in life. Considerably variable from nearly colorless to brown, reddish brown or green.

Size. Females cl 5.3–8.9 mm, ovigerous females cl 7.5–8.9 mm; males cl 4.0– 6.6 mm.

Variation. A total of 65 specimens, including 42 females, 22 males and one juvenile, were examined for assessing morphological variation in some characters possibly providing diagnostic significance.

The number of the rostral ventral teeth varies from three to seven (Fig. 18), but more than half of the specimens examined (31 of 54 specimens; 57.4 %) have five teeth. Thirteen specimens (24.0 %) have six teeth, and eight (14.8 %) have four teeth. The possession of three or seven teeth appears unusual for the species, because there is only a single example for each case.

Frequency of the presence or absence of the pterygostomial tooth on the carapace varied with sexes (Table 2). Females are provided with the teeth on both sides in most specimens (84.6 %), and it is restricted to one side only in three specimens (7.7 %) or entirely absent in three specimens (7.7 %). On the other hand, only about one-fourth of males (27.3 %) have the teeth on both sides; five specimens (22.7 %) have the tooth on one side; and 11 specimens (50.0 %) entirely lack the tooth.

The number of the meral spines on the third pereopod is variable from three to six (Fig. 19), but the majority of the specimens (88.0 %) have four or five spines. Six specimens (10 %) have six spines; only one specimen has six spines only on the left side, and thus this condition is rather unusual for this species.

Distribution. Widely distributed in the northern North Pacific Ocean: Peter the Great Bay, Sakhalin, Hokkaido, Kurile Islands, Kamtchatka Peninsula, Cape Lisburne in the Chukchi Sea, Bering Sea to Strait of Georgia; subtidal to 45 m.

Remarks. This study demonstrates that Heptacarpus camtschaticus is restricted to cold waters, although widely distributed in the northern North Pacific. The occurrence of the species in Honshu to Kyushu of Japan and Korea has not been confirmed. Specimens from the Pacific coast of Honshu, Japan, and Korea, which agree with the accounts of Heptacarpus camtschaticus by Hayashi & Miyake (1968) and Hayashi (1979, 1992) do represent a separate taxon, H. acuticarinatus n. sp. Therefore, previous records of H. camtschaticus from the Pacific coast of Honshu to Kyushu islands of Japan, Korea, and northern China (Balss, 1914; Parisi, 1919; Yokoya, 1933; Liu, 1963; Hayashi & Miyake, 1968; Kikuchi & Miyake, 1978; Hayashi, 1979, 1992; Cha et al., 2001) are referred to the new species. Igarashi (1971) recorded H. camtschaticus from Usu Bay, Hokkaido. Although he did not properly describe morphological features of his specimen, the given photograph (Igarashi, 1971, pl. 2, fig. 4) clearly shows a short third maxilliped not reaching the midlength of the antennal scale and a somewhat geniculate pleon. These features clearly suggest that his specimen actually represent H. longirostris, instead of H. camtschaticus (see “Comparison”).