Heptacarpus geniculatus ( Stimpson, 1860 )

Komai, Tomoyuki & Ivanov, Boris G., 2008, Identities of three taxa of the hippolytid shrimp genus Heptacarpus (Crustacea: Decapoda: Caridea), with description of a new species from East Asian waters, Zootaxa 1684, pp. 1-34 : 15-21

Heptacarpus geniculatus ( Stimpson, 1860)

( Figs 10–13 , 18 , 19 )

Hippolyte geniculata Stimpson, 1860: 103 [type locality: Hakodate, Hokkaido]; Ortmann, 1890: 503 (in part), pl. 37, fig. 3; Doflein, 1902: 636 (in part).

Spirontocaris geniculata . – Rathbun, 1902: 45 (in part), fig. 19; Yokoya, 1930: 530; 1939: 270; Miyake, 1961: 8.

Spirontocaris alcimede De Man, 1906: 404 [type locality: Seto Inland Sea, Japan]; 1907: 416, pl. 32, figs 42–46; Yu, 1935: 43.

Heptacarpus geniculatus . – Holthuis, 1947: 12, 44; Liu, 1955: 38, pl. 14, figs 1, 2; Miyake et al., 1962: 123; Sando, 1964: 32; Kubo, 1965: 615, fig. 975; Kikuchi, 1968: 180; Hayashi & Miyake, 1968: 132, fig. 5; Kurata, 1968: 137, fig. 1; Mukai, 1969: 2, fig. 4; Kim & Park, 1972: 200, pl. 3, fig. 3; Motoh, 1972: 40, fig. 3, pl. 8, figs 1, 2; Miyake, 1975: 102 (unnumbered fig.), 242; Hayashi, 1976: 16; Kikuchi & Miyake, 1978: 24; Hayashi, 1979: 21 (in part); Yamashita & Hayashi, 1980: 20, fig. 2f–j; Kojima & Hanabuchi, 1981: 45 (list); Miyake, 1982: 47; Takeda, 1982: 21, fig. 63; Hayashi, 1989: 3; Komai et al., 1992: 193 (in part); Liu & Zhong, 1994: 559 (list); Hayashi, 1995: 311, fig. 21-252A, pl. 86, fig. 4; Chace, 1997: 44 (list); Komai, 1999: 59; Motoh & Toyota, 2005: 33, fig. 3-9; Yang & Kim, 2005: 12, fig. 1.

Heptacarpus geniculatus geniculatus . – Vinogradov, 1950: 211 (key).

Heptacarpus geniculata . – Kubo, 1960: 102, pl. 51, fig. 4.

? Spirontocaris geniculata . – Yokoya, 1933: 26; Nishimura, 1939: 26.

Not Spirontocaris geniculata . – Urita, 1942: 22. = Heptacarpus camtschaticus ( Stimpson, 1860) .

Not Heptacarpus geniculatus [= Heptacarpus longirostris ( Kobjakova, 1936) ]. – Igarashi, 1969: 7, pl. VIII, fig. 22, pl. XVI, fig. 49.

Not Heptacarpus geniculatus [= Heptacarpus pandaloides ( Stimpson, 1860) ]. – Miyake, 1982, pl. 16, fig. 3.

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

Material examined. Japan. CBM-ZC 510, 10 females (cl 6.3–7.4 mm), 3 males (cl 4.9–6.2 mm), Miyajima, Hiroshima Prefecture, Seto Inland Sea, subtidal, 13 October 1997, coll. K. Yamashita; CBM-ZC 591, 1 female (cl 3.1 mm), Takeoka, Futtsu, Boso Peninsula, intertidal, 13 May 1994, coll. T. Sunobe; CBM-ZC 959, 2 females (cl 8.8, 9.9 mm), Kanbayashi Port, Miyako Bay, Iwate Prefecture, subtidal, trap, 12 August 1994, coll. T. Komai; CBM-ZC 1694, 1 ovigerous female (cl 9.4 mm), Nebama, Otsuchi Bay, Iwate Prefecture, 3–4 m, Zostera belt, small beam trawl, 26 May 1995, coll. T. Komai; CBM-ZC 8525, 2 ovigerous females (cl 8.3, 9.4 mm), Kurahashi Island, Hiroshima Prefecture, Seto Inland Sea, 5 m, commercial trawler, 13 April 2005, coll. K. Hiramoto; HUMZ-C 140, 1male (cl 5.5 mm), Kanbayashi Port, Miyako Bay, 2–3 m, 30 December 1982, trap, coll. T. Komai; HUMZ-C 159, same locality, 24 October 1987, trap, coll. T. Komai; KMNH (formerly ZLKU 4058), 17 ovigerous females (cl 8.3–9.1 mm), 5 females (cl 8.6–10.3 mm), 33 males (cl 4.8–6.1 mm), Tomioka Bay, Amakusa Islands, Kumamoto Prefecture, subtidal, Zostera belt, 22 and 23 December 1958, small Danish seine, coll. T. Kikuchi; KMNH (formerly ZLKU 9411), 4 females (cl 4.1–7.8 mm), Aomori Bay, Mutsu Bay, Aomori Prefecture, subtidal, 20 July 1959, small Danish seine, coll. H. Sando.

Description of female. Body ( Fig. 10 ) slender for genus. Rostrum ( Figs 10 , 11 A, B) straight, directed forward, generally styliform, slightly falling short of to slightly overreaching distal margin of antennal scale, 1.11–1.57 of carapace length; dorsal margin armed with 4–6 (most frequently 5) teeth including 2–4 (most frequently 3) on rostrum proper and 1 or 2 on carapace, posteriormost tooth arising from 0.14–0.17 length of carapace, distal 0.34–0.72 of dorsal margin unarmed; ventral blade relatively shallow, deepest at proximal to midlength; ventral margin with 6–9 (rarely 5) teeth; teeth subequal or slightly unequal except for smaller distalmost tooth; lateral carina blunt. Carapace ( Figs 10 , 11 A, B) with postorbital rostral ridge low, not extending to anterior 0.25 of carapace length; dorsal margin in lateral view straight; suborbital lobe ( Fig 11 A) rounded, constricted at base, falling short of or reaching antennal tooth; pterygostomial angle unarmed or armed with tiny tooth.

Pleon ( Figs 10 , 13 E) strongly gibbous. Second somite with faint transverse groove on tergite. Dorsal surface of third tergite strongly elevated in posterior part; posterodorsal margin of tergite weakly produced. Pleura of anterior four somites broadly rounded, fifth pleuron with moderately large posteroventral tooth; posterolateral margin of fifth pleuron slightly sinuous. Sixth somite 1.75–1.90 times longer than fifth and about 2.00 times longer than high. Telson ( Fig. 11 C) about 1.20–1.30 length of sixth somite, 3.40–3.70 times longer than wide, armed with 3–5 (most frequently 4) dorsolateral spines on either side; posterior margin with 1 sharp median tooth and 3 pairs of unequal spines.

Eye-stalk ( Fig. 11 B) generally subpyriform; cornea slightly wider and shorter than remaining part of eyestalk; ocellus distinct, showing as black spot; maximal diameter of cornea 0.15–0.18 of carapace length.

Antennular peduncle ( Fig. 11 B) falling short of midlength of antennal scale. First segment unarmed on dorsodistal margin; stylocerite overreaching distal margin of first segment, acuminate, mesial margin convex or sinuous, 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 0.30–0.35 of carapace length.

Antenna ( Fig. 11 B, C) 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 0.96–1.29 of carapace length and 5.50–6.00 times longer than wide; lateral margin straight or slightly concave; distal lamella rounded, strongly produced, considerably exceeding beyond distolateral tooth.

Third maxilliped ( Figs 10 , 12 A) moderately stout, short, falling short of midlength of antennal scale; ultimate segment about 2.20 length of carpus (= penultimate segment), tapering distally, with several darkly pigmented corneous spines distally.

First pereopod ( Fig. 12 B) moderately stout, slightly overreaching base of antennal scale; chela ( Fig. 12 C) 1.50–1.70 of carpal length and 3.50–3.90 times longer than wide; dactylus about 0.60 length of palm, terminating in 2 darkly pigmented, strong corneous ungues ( Fig. 12 D); fixed finger terminating in single corneous unguis ( Fig. 12 D); carpus slightly widened distally; merus about 1.60 of carpal length, about 3.20 times longer than high; dorsolateral distal angle of ischium with minute denticle. Second pereopods ( Fig. 12 E) equal, reaching midlength of antennal scale; dactylus about 0.60 of palm length; carpus about 3.80 times longer than chela, divided in 7 unequal articles; ischium subequal in length to merus. Third to fifth pereopods relatively short, similar in structure. Third pereopod ( Fig. 12 F) overreaching midlength of antennal scale by length of dactylus; dactylus ( Fig. 12 G) 0.30–0.35 of propodal length, 3.50–3.80 times longer than deep, terminating in acute, pigmented unguis, armed with 5–6 accessory spinules on flexor margin; propodus with 2 rows of slender spinules on flexor margin; carpus 0.45–0.50 of propodal length; merus 8.50–9.50 times longer than high, armed with 6–8 spines ventrally; ischium unarmed. Fourth pereopod ( Fig. 12 H) not reaching midlength of antennal scale; merus with 4–7 lateral spines. Fifth pereopod ( Fig. 12 I) reaching 0.30 of antennal scale; propodus with tufts of grooming setae distally ( Fig. 12 J); merus with 3–5 lateral spines.

Gill formula as in Table 1 . Only third maxilliped with strap-like epipod corresponding to setobranch on first pereopod.

Uropod ( Fig. 10 ) with both rami slightly overreaching posterior margin of telson.

Description of male. Body more slender than in females ( Fig. 13 A, B). Rostrum ( Fig. 13 A) 1.32–1.55 length of carapace, anterior 0.39–0.71 unarmed. Third pleonal tergite very strongly convex in posterior part, sometimes markedly produced ( Fig. 13 B). Corneal diameter about 0.15–0.17 of carapace length ( Fig. 13 A). Outer flagellum of antennule larger than in females, thickened aesthetasc-bearing portion about 0.40 length of carapace ( Fig. 13 A). Antennal scale 1.16–1.26 times longer than carapace. Third to fifth pereopods less stout than in females, armature similar to that of females. Endopod of first pleopod ( Fig. 13 C) 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 distinctly longer than appendix interna, with numerous long setae on dorsal surface to tip ( Fig. 13 D).

Variation. A total of 79 specimens, including 43 females, 36 males, were examined for assessing morphological variation in some characters possibly providing diagnostic significance.

The number of ventral rostral teeth varies from five to ten ( Fig. 18 ), but the many of the specimens examined have seven or eight teeth (47 of 69 specimens; 68.1 %). Ten and nine specimens (14.5 % and 13.0 %) have nine or six teeth respectively. Only two specimens and a single specimen have five or ten teeth respectively, and thus the conditions may be rather exceptional for H. geniculatus .

Frequency of the presence or absence of the pterygostomial tooth on the carapace is summarized in Table 3 . Most of the females (35 of 42 specimens; 83.3 %) lack the pterygostomial tooth on either side, although seven specimens (16.7 %) have the tooth on both sides. There is no example that one side bears a tooth. On the other hand, the pterygostomial angle is exclusively unarmed on both sides in the male specimens.

The number of meral spines on the third pereopod varies from five to eight ( Fig. 19 ), but the majority of the examined specimens (82.0 %) have six or seven spines. Nine specimens (11.5 %) have five meral spines, and five specimens (6.5 %) have eight spines.

Size. Females cl 3.3–9.9 mm, ovigerous females cl 7.5–9.4 mm; males cl 4.9–6.1 mm.

Coloration in life. Variable; body and appendages transparent, dark brown, reddish brown, or green. occasionally with white middorsal longitudinal stripe.

Distribution. Temperate waters in East Asia: southern Hokkaido to Kyushu, Japan, Korea, and northern China, intertidal to 4 m. Abundant in Zostera belts of inshore waters.

Remarks. The present study shows that Heptacarpus geniculatus is restricted to temperate parts in East Asia. Therefore, the records by Doflein (1902) and Rathbun (1902) are referable to H. geniculatus only at least in part, because their material contained specimens from Nemuro ( Doflein, 1902) or from Muroran (as Mororan; Rathbun, 1902), the locations in Hokkaido where the occurrence of H. geniculatus has not been verified. Similarly, Nishimura’s (1939) record of Spirontocaris geniculata can not be referred to the present species, as his specimens came from Nemuro and Muroran. It is impossible to specify what species was actually represented by these records, because no information on morphology was provided. From Nemuro and the adjacent area, the occurrence of H. camtschaticus and H. longirostris has been confirmed. Furthermore, the occurrence of H. geniculatus at sublittoral depths exceeding 100 m has not been confirmed. Therefore, the record by Yokoya (1933) from north of Oga Peninsula, Akita Prefecture, at a depth of 145 m is questionably included in the synonymy.

We concur with previous authors that Spirontocaris alcimede de Man, 1906 is a junior synonym of Heptacarpus geniculatus . Eualus geniculata var. longirostris Kobjakova, 1936 , which was synonymized with H. geniculatus by Hayashi (1979), is resurrected as a full species (see “Remarks” of H. longirostris ).

Figures

FIGURE 10. Heptacarpus geniculatus (Stimpson, 1860). Ovigerous female (cl 9.3 mm; ZLKU 4058), Tomioka Bay, Amakusa, Kyushu, habitus in lateral view. Scale bar: 2 mm.

FIGURE 11. Heptacarpus geniculatus (Stimpson, 1860). Ovigerous female (cl 9.3 mm; ZLKU 4058), Tomioka Bay, Amakusa, Kyushu. A, rostrum and anterior part of carapace, lateral view; B, rostrum, anterior part of carapace and cephalic appendages, dorsal view (setae partially omitted); C, telson, dorsal view; D, left antennal scale, ventral view (setae omitted). Scales: 2 mm for A, B; 1 mm for C, D.

FIGURE 12. Heptacarpus geniculatus (Stimpson, 1860). Ovigerous female (cl 9.3 mm; ZLKU 4058), Tomioka Bay, Amakusa, Kyushu, left thoracic appendages. A, third maxilliped, lateral view; B, first pereopod, lateral view; C, chela of first pereopod, dorsal (extensor) view; D, tips of dactylus and fixed finger; E, second pereopod, lateral view; F, third pereopod, lateral view; G, dactylus and distal part of propodus of third pereopod, lateral view; H, fourth pereopod, lateral view; I, fifth pereopod, lateral view; J, dactylus and distal part of propodus of fifth pereopod, lateral view. Scales: 1 mm for A – C, E, F, H, I; 0.5 mm for D, G, J.

FIGURE 13. Heptacarpus geniculatus (Stimpson, 1860). A – D, male (cl 4.9 mm; CBM-ZC 510), Miyajima, Hiroshima Prefecture, Seto Inland Sea; E, female (cl mm; same lot). A, carapace and cephalic appendages, lateral view; B, pleon, telson and uropod, lateral view; C, endopod of left first pleopod, ventral view; D, appendices interna and masculina of left second pleopod, mesial view; E, third to fifth pleonal somites, lateral view. Scale bars: 2 mm for A, B, E; 0.5 mm for C, D.

FIGURE 18. Variation in the number of rostral ventral teeth of four Heptacarpus species.

FIGURE 19. Variation in the number of meral spines on the third pereopod of four Heptacarpus species.

Tables

TABLE 3. Variation in the presence or absence of a pterygostomial tooth in Heptacarpus geniculatus (Stimpson, 1860).

	Female	Male
Present on both sides	7 (16.7 %)	0 (0 %)
Present on one side	0 (0 %)	0 (0 %)
Absent on either side	35 (83.3 %)	36 (100 %)