Heptacarpus longirostris ( Kobjakova, 1936 )

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 : 21-28

Heptacarpus longirostris ( Kobjakova, 1936)

( Figs 14–19 )

Hippolyte geniculata . — Doflein, 1902: 636 (? part).

Spirontocaris geniculata . — Rathbun, 1902: 45 (part); Urita, 1942: 22.

Eualus geniculata ? — Derjugin & Kobjakova, 1935: 142 (list).

Eualus geniculata var. longirostris Kobjakova, 1936: 211 , fig. 38 [type locality: Peter the Great Bay]; Chace, 1997: 43 (list).

Eualus geniculata longirostris .— Kobjakova, 1937: 121; 1958: 225 (in part).

Heptacarpus geniculatus longirostris . — Vinogradov, 1950: 210, pl. 16, fig. 68; Kobjakova, 1967: 235; Andrianov & Kussakin, 1998: 264 (list).

Spirontocaris geniculata longirostris . — Kobjakova, 1958: 225.

Heptacarpus geniculatus . — Igarashi, 1969: 7, pl. VIII, fig. 22, pl. XVI, fig. 49; Hayashi, 1979: 21 (in part).

Heptacarpus camtschaticus . — Igarashi, 1971: 2, pl. II, fig. 4. Not Heptacarpus camtschaticus ( Stimpson, 1860) .

Type material. Presumably no longer extant.

Material examined. Kurile Islands. ZISP 2/33569, 2 females (cl 8.0, 10.0 mm), Matsuba Bay, Shikotan Island, 19.5–25 m, 18 September 1949, dredge No. 23, coll. E. F. Gurjanova, identified with Eualus geniculata longirostris by Z. I. Kobjakova; ZISP 1/33568, interior part of Anama Bay, Shikotan Island, 3 August 1949, trawl, coll. E. F. Gurjanova, 1 female (cl 7.7 mm), identified with Eualus geniculata longirostris by Z. I. Kobjakova. Japan. Hokkaido. CBM-ZC 8659, 2 females (cl 6.2, 7.3 mm), Notoro Lake, Abashiri, Hokkaido, subtidal, Zostera belt, 13 May 2005, sledge, coll. S. Chiba; CBM-ZC 8600, 1 female (cl 6.6 mm), 1 ovigerous female (cl 6.4 mm), Usujiri, Minami-Kayabe, 20 m, 13 November 1992, dredge, coll. T. Komai; CBM-ZC 8601, 2 females (cl 7.8, 8.4 mm), 1 male (cl 4.6 mm), same locality, 20–25 m, 8 October 1991, dredge, coll. T. Komai; CBM-ZC 8660, 8 females (cl 5.0– 7.3 mm), same locality, 30 September 2005, sledge, coll. S. Chiba; CBM-ZC 8661, 2 males (cl 3.7, 4.0 mm), 7 females (cl 8.2– 6.2 mm), Futatsu-iwa, Abashiri, Hokkaido, subtidal, Zostera belt, 10 September 2005, coll. S. Chiba; CBM-ZC 8662, 2 ovigerous females (cl 6.1, 7.8 mm), 3 females (cl 5.7–6.5 mm), 2 males (cl 4.2, 4.4 mm), Notoro Lake, Hokkaido, 3–4 m, 23 October 1997, coll. S. Goshima; CBM-ZC 9044, 1 female (cl 6.6 mm), off Usujiri, Minami Kayabe, 15–25 m, 11 June 1993, dredge, coll. F. Muto. Exact locality unknown. ZISP 41392-2, Pacific Ocean, dredge 91-95, 1 female (cl 6.4 mm). Prymorye. ZISP, 2 females (cl 7.1, 7.5 mm), Stark's Strait, Peter the Great Bay, 4 August 1979.

Description of female. Body ( Fig. 14 ) slender for genus. Rostrum ( Figs 14 , 15 A, B) straight, directed forward, slightly falling short of to slightly overreaching distal margin of antennal scale, 1.03–1.32 length of carapace; 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 0.15–0.19 length of carapace, distal 0.50–0.70 of dorsal margin unarmed; ventral blade relatively shallow, deepest at proximal to midlength of rostrum; ventral margin with 4–6 (rarely 7 or 8) teeth (teeth unequal in size but not increasing in size posteriorly); lateral carina blunt. Carapace ( Figs 14 , 15 A, B) with postorbital rostral ridge low, not extending to anterior 0.25 of carapace length; dorsal margin in lateral view slightly sinuous; suborbital lobe ( Fig 15 B) rounded, constricted at base, falling short of antennal tooth; pterygostomial angle frequently armed with tiny tooth.

Pleon ( Fig. 14 ) dorsally rounded, not markedly gibbous. Second somite with faint transverse groove on tergite. Dorsal surface of third tergite evenly convex, posterodorsal margin somewhat produced. Pleura of anterior 4 somites broadly rounded; fifth pleuron unarmed at posteroventral angle, posterolateral margin truncate. Sixth somite 1.75–1.90 times longer than fifth and 1.90–2.00 times longer than high. Telson ( Fig. 15 C) 1.15–1.30 length of sixth somite, about 4.40 times longer than wide, armed with 3 or 4 dorsolateral spines on either side; posterior margin bluntly triangular, with 3 pairs of unequal spines.

Eye-stalk (including cornea) ( Fig. 15 B) generally subpyriform; cornea slightly wider and shorter than 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. 15 B) falling short of midlength of antennal scale. First segment unarmed on dorsodistal margin; stylocerite reaching or slightly 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 small spine at dorsolateral distal angle; third segment short, with small spine on dorsodistal margin. Lateral flagellum with thickened aesthetasc-bearing portion 0.30–0.35 of carapace length.

Antenna ( Fig. 15 B, D) with basicerite bearing moderately large ventrolateral distal tooth; carpocerite reaching 0.25–0.30 length of antennal scale or distal margin of second segment of antennular peduncle. Antennal scale 0.89–1.11 length of carapace and 3.90–4.50 times longer than wide; lateral margin straight; distal lamella rounded, strongly produced, considerably exceeding beyond distolateral tooth.

Third maxilliped ( Figs 14 , 16 A) moderately stout, short, not reaching midlength of antennal scale; ultimate segment 1.90–2.00 length of carpus (= penultimate segment), tapering distally, with several darkly pigmented corneous spines distally.

First pereopod ( Fig. 16 B) moderately stout, overreaching base of antennal scale; chela ( Fig. 16 C) about 2.00 of carpal length and 3.00–3.50 times longer than wide; dactylus 0.45–0.50 length of palm, terminating in 3 darkly pigmented, strong corneous ungues ( Fig. 16 D); fixed finger terminating also in three corneous ungues ( Fig. 16 D); merus 1.60–1.70 of carpal length, about 3.40 times longer than high; dorsolateral distal angle of ischium with minute denticle. Second pereopods ( Fig. 16 E) equal, reaching midlength of antennal scale; dactylus about 0.60 of palm length; carpus about 4.30 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. 16 F) overreaching midlength of antennal scale by length of dactylus; dactylus ( Fig. 16 G) 0.28–0.35 of propodal length, 2.80–3.00 times longer than deep, terminating in acute, pigmented unguis, armed with 4–6 accessory spinules on flexor margin, of them distal 1 or 2 weakly hooked; propodus with 2 rows of slender spinules on flexor margin ( Fig. 16 G); carpus 0.45–0.55 of propodal length; merus 8.10–9.50 times longer than high, armed with 3–5 (rarely 2) lateral spines; ischium unarmed. Fourth pereopod ( Fig. 16 H) not reaching midlength of antennal scale; merus with 3 or 4 lateral spines. Fifth pereopod ( Fig. 16 I) reaching proximal 0.30 of antennal scale; propodus with tufts of grooming setae distally; merus with 3 or 4 (rarely 2) lateral spines.

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

Uropod ( Fig. 14 ) with both rami slightly overreaching posterior margin of telson. Description of male. Body slightly more slender than in females ( Fig. 17 A, C). Rostrum ( Fig. 17 B) 1.29–1.43 length of carapace, anterior 0.58–0.66 unarmed. Pleon ( Fig. 17 C) weakly geniculate; third pleonal tergite weakly convex in posterior part. Corneal diameter about 0.15–0.17 of carapace length ( Fig. 17 A). Outer flagellum of antennule larger than in females, thickened aesthetasc-bearing portion about 0.40–0.45 length of carapace ( Fig. 17 A). Antennal scale 0.97–1.11 times longer than carapace. Third to fifth pereopods less stout than in females, armament similar to that of females. Endopod of first pleopod ( Fig. 17 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 ( Fig. 17 E) with appendix masculina slightly shorter than appendix interna, with numerous long setae on dorsal surface to tip.

Variation. A total of 32 specimens, including 27 females and five males, were examined for assessing morphological variation in some characters possibly providing diagnostic significance.

The possession of five or six rostral ventral teeth appears usual for H. longirostris (26 of 30 specimens examined; 86.7 %), although the number of the teeth varies from four to eight ( Fig. 18 ). Only two specimens have four teeth; the possession of seven or eight teeth is found respectively in a single specimen.

Frequency of the presence or absence of the pterygostomial tooth on the carapace is summarized in Table 4 . Most of the females (22 of 27 specimens; 81.5 %) have the pterygostomial teeth on both sides, although only one specimen entirely lacks the tooth; four specimens (14.8 %) have the tooth on one side. All five male specimens have the pterygostomial teeth on both sides.

The number of the meral spines on the third pereopod varies from two to five ( Fig. 19 ), but the majority of the examined specimens (30 of 33 specimens; 90.9 %) have three or four spines. One specimen (11.5 %) has two meral spines, and other two specimens (6.1 %) have five spines.

Size. Females cl 5.4–8.2 mm, ovigerous females cl 6.1–7.8 mm; males cl 3.7–4.6 mm.

Coloration in life. Not recorded.

Distribution. Peter the Great Bay, southern Kurile Islands and Hokkaido, Japan, subtidal to 25 m. Abundant in Zostera belts of inshore waters.

Remarks. Kobjakova (1936) described a new taxon Eualus geniculata var. longirostris from Peter the Great Bay. This taxon is deemed as a subspecies according to the ICZN Code (ICZN, 1999). Later Kobjakova (1937) discussed more in detail the distinctions between the nominotypical and her new subspecies. The differentiating characters are: (1) rostrum long, reaching beyond scaphocerite, and about 1.5 times as long as carapace; (2) unarmed part of dorsal margin of rostrum large; (3) scaphocerite not longer than carapace; (4) pterygostomial tooth usually present and (5) lamellar part of scaphocerite exceeding distolateral tooth. Based on specimens from various localities in Japan, Hayashi (1979) critically examined these characters cited by Kobjakova (1936, 1937). He found that all but the third character are considerably variable, and thus came to a conclusion that Kobjakova’s taxon was a junior synonym of H. geniculatus .

However, we noticed the existence of a distinct species resembling Heptacarpus geniculatus and H. camtschaticus in our material, and then considered a possibility that Kobjakova’s taxon might correspond to the unidentified species under question. The unidentified species is characterized by the rounded fifth pleonal pleuron, the third maxilliped not reaching the midlength of the antennal scale, the possession of three ungues on each dactylus and fixed finger of the first pereopod (see “Comparison”). As noted above, in spite of the effort by the second author, the type material of Eualus geniculata longirostris was not located in the collection of the ZISP, in which it should be deposited. Nevertheless, fortunately, specimens identified with E. geniculata longirostris by Z. I. Kobjakova herself and those from the Peter the Great Bay, the type locality of the taxon, have been available for study (see “Material examined”). Reexamination of the material identified by Dr. Kobjakova has disclosed that two species, including H. camtschaticus , are confounded, but the second species corresponds to the unidentified species in question. Comparison with the accounts given by Kobjakova (1936, 1937) suggested that her new taxon does not correspond to H. camtschaticus in the usual presence of a pterygostomial tooth on the carapace in females and the greater unarmed part of the dorsal margin of the rostrum. We propose to reinstate Kobjakova’s taxon as a full species of Heptacarpus , because it is easily separable by morphological characters and distributional patterns from the other known species in the genus (see “Comparison”). It is likely that the type material used by Kobjakova (1936) might be actually a mixture of the two species, H. longirostris and H. camtschaticus , but we feel hesitation to designate a neotype for Kobjakova’s taxon, because a more through search would be desirable in order to confirm if the type material was really lost.

Igarashi (1969) reported Heptacarpus geniculatus from off Mashike, Oshoro Bay, and off Shimamaki, Hokkaido. The given photograph ( Igarashi, 1969, pl. 8, fig. 22) clearly shows that the pleon is not strongly geniculate, whereas it is strongly geniculate and gibbous at the third somite in H. geniculatus . Therefore, his record is at least partially referred to H. longirostris . As mentioned before, a specimen referred to H. camtschaticus by Igarashi (1971) actually represents H. longirostris .

Figures

FIGURE 14. Heptacarpus longirostris (Kobjakova, 1936). Female (cl 8.4 mm; CBM-ZC 8601), Usujiri, southern Hokkaido, habitus in lateral view. Scale bar: 2 mm.

FIGURE 15. Heptacarpus longirostris (Kobjakova, 1936). Female (cl 8.4 mm; CBM-ZC 8601), Usujiri, southern Hokkaido. A, rostrum and anterior part of carapace, lateral view; B, rostrum, anterior part of carapace and cephalic appendages, dorsal view; C, telson, dorsal view; D, left antennal scale, ventral view. Scale bars: 2 mm for A, B, D; 1 mm for C.

FIGURE 16. Heptacarpus longirostris (Kobjakova, 1936). Female (cl 8.4 mm; CBM-ZC 8601), Usujiri, southern Hokkaido, left 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. Scale bars: 1 mm for A, B, E, F, H, I; 0.5 mm for C, D, G.

FIGURE 17. Heptacarpus longirostris (Kobjakova, 1936). Male (cl 4.0 mm; CBM-ZC 8661), Abashiri, Hokkaido, Okhotsk Sea. A, carapace and cephalic appendages, lateral view; B, rostrum, lateral view; C, pleon, lateral view; D, endopod of left first pleopod, ventral view; E, appendices interna and masculina of second pleopod, mesial view. Scale bars: 1 mm for A – C; 0.5 mm for D, E.

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 4. Variation in the presence or absence of a pterygostomial tooth in Heptacarpus longirostris (Kobjakova, 1936).

	Female	Male
Present on both sides	22 (81.5 %)	5 (100 %)
Present on one side	4 (14.8 %	0 (0 %)
Absent on either side	1 (3.7 %)	0 (0%)