Heptacarpus acuticarinatus, Komai, Tomoyuki & Ivanov, Boris G., 2008

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 : 9-15

publication ID	https://doi.org/ 10.5281/zenodo.180453
DOI	https://doi.org/10.5281/zenodo.6236176
persistent identifier	https://treatment.plazi.org/id/03859630-FFA1-1C0C-CDF0-566728F2FD5A
treatment provided by	Plazi
scientific name	Heptacarpus acuticarinatus
status	sp. nov.

Treatment

Heptacarpus acuticarinatus n. sp.

( Figs 5–9 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 , 18 View FIGURE 18 , 19 View FIGURE 19 )

Spirontocaris camtchatica . – Balss, 1914: 44; Parisi, 1919: 47; Yokoya, 1933: 26. Not Spirontocaris camtschatica ( Stimpson, 1860) .

Heptacarpus camtschaticus . – Liu, 1963: 237; Hayashi & Miyake, 1968: 134, fig. 6; Kikuchi & Miyake, 1978: 24; Hayashi, 1979: 14; 1992: 180, figs 223a, 224a, 225a; Liu and Zhong, 1994: 559 (list); Cha et al. 2001: 90 –91. Not Heptacarpus camtschaticus ( Stimpson, 1860) .

Type material. Holotype. CBM-ZC 8980, ovigerous female (cl 5.4 mm), Sagami Bay, 35°07.858'N, 139°33.698'E, 100–101 m, sand bottom, 22 January 2003, RV Rinkai-maru, dredge, coll. T. Komai.

Paratypes. Japan. CBM-ZC 3531, 1 female (cl 4.0 mm), off Kominato, Boso Peninsula, 100–150 m, 27 February 1997, gill net, coll. T. Komai; CBM-ZC 2695, 5 females (cl 2.6–3.9 mm), 1 ovigerous female (cl 5.4 mm), off Shionomisaki, Kii Peninsula, 80 m, 25 July 1991, dredge, coll. S. Nagai; HUMZ-C 1174, 1 male (cl 3.7 mm), Kashima-nada Sea off Ibaraki Prefecture, depth unknown, 25 September 1989, larva net accidentally on bottom, coll. D. Kitagawa; NSMT-Cr S 9, 1 ovigerous female (cl 4.9 mm), Sagami Bay, 35°07.90’N, 139°34.48’E, 94–95 m, sand bottom, 27 February 2002, RV Rinkai-maru, dredge, coll. T. Komai. Korea. NFRDI-Cr 20070417-1, 2 females (cl 5.5, 5.6 mm), 1 male (cl 5.2 mm), Hansan Island, 20–30 m, September 1998; NFRDI-Cr 20070417-2, 5 ovigerous females (cl 5.9–6.4 mm), same locality, 20 April 1999; NFRDI-Cr 20070417-3, 5 ovigerous females (cl 6.1–6.8 mm), same locality, 20 May 1999.

Other material. Japan. HUMZ-C 29, 2 females (cl 5.2, 5.7 mm), off Irifune, Hakodate, Hakodate Bay, southern Hokkaido, ca. 30 m, 9 November 1986, gill net, coll. T. Komai; HUMZ-C 1179, 1 female (cl 5.0 mm), similar locality, depth unknown, 19 November 1990, small beam trawl, coll. T. Komai.

Description of female. Body ( Fig. 5 View FIGURE 5 ) moderately robust for genus. Rostrum ( Fig. 5 View FIGURE 5 , 6 View FIGURE 6 A, B) straight, directed forward, slightly falling short of or reaching distal margin of antennal scale, 1.22–1.53 length of carapace; dorsal margin armed with 5–7 teeth including 4–6 on rostrum proper and 1 or 2 on carapace, posteriormost tooth arising from 0.13–0.17 length of carapace, distal 0.16–0.30 of dorsal margin unarmed; ventral blade relatively deep, deepest at slightly proximal to midlength of rostrum; ventral margin with 5–8 teeth (teeth slightly unequal or subequal in size except for minute distalmost tooth); lateral carina sharply defined. Carapace ( Fig. 5 View FIGURE 5 , 6 View FIGURE 6 A, B) with postorbital rostral ridge low, not extending to anterior 0.25 of carapace length; dorsal margin in lateral view nearly straight; suborbital lobe ( Fig 6 View FIGURE 6 A) rounded, constricted at base, falling short of or reaching antennal tooth; pterygostomial angle always with small tooth.

Pleon ( Fig. 5 View FIGURE 5 ) dorsally rounded, not gibbous. Second somite with faint transverse groove on tergite. Dorsal surface of third tergite evenly convex, posterodorsal margin somewhat produced. Pleura of anterior four somites broadly rounded; fifth pleuron with moderately large posteroventral tooth, posterolateral margin sinuous. Sixth somite 1.50–1.60 times longer than fifth and 1.90–2.00 times longer than high. Telson ( Figs 5 View FIGURE 5 , 6 View FIGURE 6 C) 1.20–1.30 length of sixth somite, about 3.60 times longer than wide, armed with 5 or 6 dorsolateral spines on either side; posterior margin terminating in acute tooth, with 3 pairs of unequal spines.

Eye-stalk ( Fig. 6 View FIGURE 6 B) generally subpyriform; cornea slightly wider and longer than remaining part of eyestalk; ocellus distinct, showing as black spot; maximal diameter of cornea 0.20–0.22 of carapace length.

Antennular peduncle ( Fig. 6 View FIGURE 6 B) not reaching 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 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. 6 View FIGURE 6 B, D) with basicerite bearing moderately large ventrolateral distal tooth; carpocerite reaching 0.30–0.35 length of antennal scale or distal margin of second segment of antennular peduncle. Antennal scale 1.02–1.09 length of carapace and 3.30–3.70 times longer than wide; lateral margin straight; distal lamella rounded, moderately produced, exceeding beyond distolateral tooth.

Third maxilliped ( Figs 5 View FIGURE 5 , 7 View FIGURE 7 A) moderately stout, relatively long, reaching distal 0.15–0.30 of antennal scale; ultimate segment 2.20–2.40 length of carpus (= penultimate segment), tapering distally, with several darkly pigmented corneous spines distally.

First pereopod ( Fig. 7 View FIGURE 7 B) moderately stout, reaching nearly to midlength of antennal scale; chela ( Fig. 7 View FIGURE 7 C) about 1.85–2.00 of carpal length and 3.50–3.80 times longer than wide; dactylus 0.50–0.60 length of palm, terminating in 2 darkly pigmented, strong corneous ungues ( Fig. 7 View FIGURE 7 D); fixed finger terminating 1 corneous unguis ( Fig. 7 View FIGURE 7 D); merus about 1.70 of carpal length and about 3.20–3.40 times longer than high; dorsolateral distal angle of ischium with small denticle. Second pereopods ( Fig. 7 View FIGURE 7 E) equal, slightly falling short of distal margin of antennal scale; dactylus 0.70–0.75 of palm length ( Fig. 7 View FIGURE 7 F); carpus about 3.80 times longer than chela, divided in 7 unequal articles; ischium subequal in length to merus. Third to fifth pereopods relatively long, similar in structure. Third pereopod ( Fig. 7 View FIGURE 7 G) reaching or slightly overreaching distal margin of antennal scale; dactylus ( Fig. 7 View FIGURE 7 H) 0.25–0.30 of propodal length, 4.50–5.00 times longer than deep, terminating in long, acute, pigmented unguis, armed with 5 or 6 accessory spinules on flexor margin; propodus with 2 rows of slender spinules on flexor margin ( Fig. 7 View FIGURE 7 H); carpus 0.40–0.45 of propodal length; merus 9.00–9.50 times longer than high, armed with 7–10 lateral spines; ischium unarmed. Fourth pereopod ( Fig. 7 View FIGURE 7 I) reaching distal 0.70–0.80 of antennal scale; merus with 5–8 lateral spines. Fifth pereopod ( Fig. 7 View FIGURE 7 J) reaching midlength of antennal scale; propodus with tufts of grooming setae distally ( Fig. 7 View FIGURE 7 K); merus with 3–6 lateral spines.

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

Uropod ( Fig. 5 View FIGURE 5 ) with both rami reaching or slightly overreaching posterior margin of telson.

Description of males. Body slightly more slender than in females ( Fig. 8 View FIGURE 8 A, C). Rostrum ( Fig. 8 View FIGURE 8 A, B) 1.42–1.57 length of carapace, anterior 0.16–0.24 unarmed. Pleon ( Fig. 8 View FIGURE 8 C) weakly geniculate; third pleonal tergite evenly convex in posterior part. Corneal diameter about 0.20–0.22 of carapace length ( Fig. 8 View FIGURE 8 A). Outer flagellum of antennule larger than in females, thickened aesthetasc-bearing portion about 0.50 length of carapace ( Fig. 8 View FIGURE 8 A). Antennal scale 1.14–1.25 times longer than carapace. Third to fifth pereopods similar to those of females. Endopod of first pleopod ( Fig. 8 View FIGURE 8 D) elongate subtriangular, with conspicuous appendix interna at terminal position; distolateral lobule delineated; mesial margin with row of small spiniform setae, lateral margin with row of long plumose setae. Second pleopod with appendix masculina slightly shorter than appendix interna, with numerous setae increasing in length distally on dorsal surface to tip ( Fig. 8 View FIGURE 8 E).

Size. Females cl 3.0– 6.8 mm, ovigerous females cl 4.4–6.8 mm; males cl 5.2 mm.

Variation. A total of 25 specimens, including 23 females and two males, were examined for assessing morphological variation in some characters possibly providing diagnostic significance.

The number of the rostral ventral teeth varies from five to eight ( Fig. 18 View FIGURE 18 ).

In all the specimens examined, the carapace is provided with pterygostomial teeth on both sides.

The number of the meral spines on the third pereopod varies from seven to 10 ( Fig. 19 View FIGURE 19 ), but the majority of the examined specimens (23 of 25 specimens; 92 %) have seven to nine spines. Other two specimens (8.0 %) have ten meral spines.

Coloration in life. Body and appendages generally pale pink; cornea gray ( Fig. 9 View FIGURE 9 ).

Distribution. Southern Hokkaido to Kyushu, Japan, Korea, and Yellow Sea, 30– 150 m.

Remarks. The new species appears closest to Heptacarpus camtschaticus , with which it has been confounded, but is readily distinguished from the latter by a number of characters, including the sharp lateral carina of the rostrum and the relatively longer pereopods with more numerous meral spines (see “Comparison” for details). The present study strongly suggests that H. camtschaticus does not occur in the Pacific coast of Honshu to Kyushu, Japan. Thus, the records of H. camtschaticus by Balss (1914) and Parisi (1919) from Sagami Bay and Yokoya (1933) from Aichi Prefecture (all as Spirontocaris ) are referred to H. acuticarinatus n. sp. There is little doubt that the specimen from Amakusa, Kyushu, cited as H. camtschaticus by Hayashi & Miyake (1968), Kikuchi & Miyake (1978), Hayashi (1979, 1992), is identical with the new species, because the morphological attributes described or shown in these references closely fit those of the new species. Similarly, the occurrence of H. acuticarinatus n. sp. instead of H. camtschaticus has been confirmed in Korean waters. Therefore, Korean records of H. camtschaticus by Cha et al. (2001) are also referred to the new species. Regarding the geographical range, the record of H. camtschaticus from northern China ( Liu, 1963) is also most probably referred to the new species.

Etymology. The species name is a combination of the Latin acutus (= sharp) and carinatus (ridged), in reference to the characteristic sharp lateral carina of the rostrum.