Pandalus ivanovi, Komai, Tomoyuki & Eletskaya, Maria, 2008

Komai, Tomoyuki & Eletskaya, Maria, 2008, A new species of the pandalid shrimp genus Pandalus (Crustacea: Decapoda: Caridea) from the Sea of Okhotsk off eastern Sakhalin, Russian Far East, Zootaxa 1882, pp. 46-56 : 47-55

publication ID	https://doi.org/ 10.5281/zenodo.184238
DOI	https://doi.org/10.5281/zenodo.6228294
persistent identifier	https://treatment.plazi.org/id/03FC8790-FF8D-FF94-FF23-875187E7BAE1
treatment provided by	Plazi
scientific name	Pandalus ivanovi
status	sp. nov.

Treatment

Pandalus ivanovi View in CoL n. sp. ( Figs 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 , 8 View FIGURE 8 )

Material examined. Holotype: CBM-ZC 9221, female (CL 28.4 mm), off eastern Sakhalin, Sea of Okhotsk, 46°N, 145°E, 2005, 150– 200 m, rocky bottom, commercial fishing using shrimp basket, S. Miyaki leg. Paratypes: CBM-ZC 9222, 2 females (CL 31.0, 31.4 mm), same data as holotype; CBM-ZC 9223, 20 females (CL 30.2–35.6 mm), same data as holotype; MNHN-Na 16873, same data as holotype; NSMT-Cr 18306, same data as holotype; CBM-ZC 9224, 4 females (CL 30.6–33.1 mm), similar locality, 2005, M. Fujiwara leg.; VNIRO, 19 transitional males (CL 27.6–30.0 mm), 5 females (CL 29.0– 31.5 mm), 3 ovigerous females (CL 27.3–33.9 mm), off eastern Sakhalin, 49°15’N 144°35’E to 49°15’N 144°39’E, 90–120 m, FRV Viktoriya 2, September 2001.

Description. Females. Body ( Fig. 1 View FIGURE 1 ) moderately robust. Rostrum ( Fig. 2 View FIGURE 2 A, B) strongly curving dorsally, overreaching distal margin of antennal scale, 1.02–1.25 times as long as carapace; dorsal margin armed with 16–24 movable spines, including 9–14 on rostrum proper and 6–9 on carapace posterior to orbital margin, and 1 or 2 small fixed teeth near apex of rostrum, subdistal 0.50–0.60 leaving unarmed, posteriormost (first) spine arising at posterior to midlength of carapace (0.55–0.59 of carapace length); ventral margin armed with 7–9 fixed teeth increasing in size posteriorly, posteriormost tooth distinctly stronger than others; lateral carina conspicuous in posterior half. Carapace ( Fig. 2 View FIGURE 2 A) with postrostral ridge moderately high, somewhat crested but non-arched, extending nearly to posterodorsal margin; dorsal margin gently convex in lateral view, posteriormost 1–4 spines on peak; antennal tooth moderately strong; branchiostegal tooth small; no conspicuous ridges or carinae on lateral surface.

Pleon ( Figs 1 View FIGURE 1 , 2 View FIGURE 2 C) dorsally smooth. Third somite without middorsal projection or posterodorsal median tooth. Fourth and fifth somites each with posterolateral tooth on pleuron. Sixth somite about 0.40 times as long as carapace and 1.70–1.80 times longer than high; posterolateral process terminating in acute tooth. Telson ( Fig. 2 View FIGURE 2 D) moderately broad, armed normally with 5 or 6 pairs of dorsolateral spines; posterior margin terminating in small blunt triangular projection, with 3 pairs of unequal spines.

Eye ( Fig. 2 View FIGURE 2 A, E) broadly subpyriform, maximal diameter of cornea 0.17–0.20 of carapace length; ocellus present.

Antennular peduncle ( Fig. 2 View FIGURE 2 A, E) reaching midlength of antennal scale; first segment with short, rounded stylocerite; second segment unarmed on dorsal surface, but with few spinules on dorsodistal margin; distal 2 segments slightly shorter than first segment; aesthetasc-bearing portion of outer flagellum distinctly shorter than carapace.

Antennal ( Fig. 2 View FIGURE 2 A, E) with stout basicerite bearing moderately strong ventrolateral tooth; carpocerite moderately stout, far falling short of midlength of antennal scale; antennal scale 0.82–0.88 times as long as carapace and 4.20–4.50 times longer than broad, lateral margin nearly straight, distolateral tooth reaching distal margin of rounded lamella.

Mouthparts usual of genus (see Komai, 1999). Third maxilliped ( Figs 1 View FIGURE 1 , 3 View FIGURE 3 A, 4A) slightly overreaching distal margin of antennal scale; ultimate segment about 1.80 as long as penultimate segment (= carpus), terminating in small corneous spine, with numerous scattered spinules and several tufts of short setae on lateral surface and 2 or 3 tufts of longer spinules on dorsal margin subdistally; mesial face of ultimate segment with numerous transverse tracts of stiff setae and few long spines; carpus also with several spinules on lateral surface and numerous stiff setae on mesial surface; antepenultimate segment (merus-ischium-basis fused segment) slightly shorter than distal 2 segments combined, with small rounded tubercle basally on dorsal surface; dorsal surface elevated at midlength; ventral margin forming blunt edge fringed with row of numerous short setae; exopod absent.

First pereopod ( Fig. 3 View FIGURE 3 B) minutely chelate, slender, slightly falling short of distal margin of antennal scale; propodus about 0.60 times as long as carpus, tapering distally, with distinct longitudinal groove lined with tufts of short setae; ischium with narrow ventral lamina terminating acutely or subacutely at ventrodistal angle; row of spinules partially obscured by stiff setae present on ventral margin of ischium. Second pereopods greatly unequal with left much longer and slender than right. Left second pereopod ( Fig. 3 View FIGURE 3 C) greatly elongate, overreaching antennal scale by 0.80–0.90 length of carpus; chela small, dactylus slightly shorter than palm; carpus elongate, divided in 54–61 articles; merus entirely annulated; ischium distally annulated, ventral margin slightly expanded in proximal half to accommodate chela. Right second pereopod ( Fig. 3 View FIGURE 3 D) overreaching antennal scale by 0.3 length of carpus; chela about 0.25 times as long as carpus, dactylus shorter than palm; carpus divided in 19–24 articles; merus with few annulations distally; ischium entire, similar to left in structure. Third to fifth pereopods decreasing in length toward posterior. Third pereopod ( Fig. 3 View FIGURE 3 E) overreaching antennal scale by 0.5–0.6 length of propodus, subprehensile; dactylus ( Fig. 4 View FIGURE 4 C) sickle-shaped, 0.32– 0.47 times as long as propodus, with 22–27 accessory spinules becoming longer and more widely spaced distally and 1 subterminal spinule appressed to slender unguis; propodus slightly recurved, laterally compressed, all surfaces with scattered spinules, particularly flexor surface with numerous scattered spinules flanked by rows of long spinules (spinules becoming fewer proximally) ( Fig. 4 View FIGURE 4 D); carpus 0.50–0.60 times as long as propodus, with 2 or 3 lateral and 1 ventromesial spines and with scattered spinules on lateral to mesial faces ( Fig. 4 View FIGURE 4 E); merus 0.86–0.94 times as long as carapace, armed with 7–9 lateral and 6–9 ventral spines; ischium with 1 ventrolateral spine. Fourth pereopod ( Fig. 3 View FIGURE 3 F) overreaching antennal scale by length of dactylus; dactylus ( Fig. 4 View FIGURE 4 F) 0.22–0.34 times as long as propodus, armed with 17–21 accessory and 1 subterminal spinules; propodus nearly straight, less spinose than third; carpus with 3 lateral and 1 ventral spines and scattered spinules on lateral to mesial faces; merus 0.72–0.79 times as long as carapace, with 5–8 lateral and 5–8 ventral spines; ischium with 1 ventral spine. Fifth pereopod ( Fig. 3 View FIGURE 3 G) falling short of distal margin of antennal scale; dactylus ( Fig. 4 View FIGURE 4 G) short, somewhat curved, 0.15–0.22 times as long as propodus, with 9–12 accessory and 1 subterminal spinules; propodus with 2 rows of long spinules on flexor surface and with tufts of grooming setae distally ( Fig. 4 View FIGURE 4 G); carpus with scattered spinules on dorsal surface and with 2 lateral and 1 ventral spines; ischium with 1 ventral spine.

First pleopod with simple endopod. Second pleopod completely lacking trace of appendix masculina. Uropod ( Fig. 2 View FIGURE 2 C) with rami subequal in length, reaching nearly to tip of telson.

Eggs numerous; size 0.83–1.00 mm along short axis and 1.00– 1.17 mm along long axis.

Transitional males. Generally similar to females ( Fig. 5 View FIGURE 5 A). Rostrum 1.08–1.33 times longer than carapace. Endopod of first pleopod ( Fig. 5 View FIGURE 5 B, D) with subterminal appendix interna; proximomesial lobe well delineated. Appendix masculina on second pleopod ( Fig. 5 View FIGURE 5 C, E) slender, 1.8–2.0 times longer than appendix interna, bearing single or few spiniform setae terminally.

Coloration in fresh. See Fig. 6 View FIGURE 6 A. Background reddish brown. Rostrum pale, with red band distal to midlength, tip also reddish. Carapace with obscure transverse band along anterolateral margin, otherwise mottled with red or reddish brown. Red or reddish brown blotches on dorsal and lateral surfaces of first to sixth pleonal somites, often forming broad transverse band. Antennal flagellum with alternating red and white. Third maxilliped red, with dark reddish brown band around joint between ultimate and penultimate segments. First pereopod also red, with banding on propodus and carpus. Second pereopod each with carpus fading distally, chela white; merus and ischium red. Third to fifth pereopods generally pink; propodi each with reddish brown band subdistally, and often with second subproximal band; banding also present on meri. Uropod red.

Distribution. So far Known only from off eastern Sakhalin, Sea of Okhotsk, at depths of 90– 200 m.

Biology. In the Sea of Okhotsk, shrimp of the genus Pandalus and Pandalopsis form a major fishery resource, and it has been generally considered that the local shrimp fauna is well documented. Thus, the discovery of a new species having a high potential of commercial value from a rather well explored area is surprising. Perhaps, the habitat preference has prevented the discovery of this new species. The captain of the fishing boat capturing the new shrimp reported that the shrimp inhabited hard bottom, and that Pandalus hypsinotus did not occur in the fishing ground where P. ivanovi n. sp. was fished (S. Miyaki, personal communication).

The available material suggests that Pandalus ivanovi n. sp. is a protandrous hermaphrodite like other congeneric species ( Komai, 1999; Bergstrom, 2000), although no specimens of functional males were available for study. Nineteen specimens (CL 27.6–30.0 mm) have subterminal appendices internae on the endopod of the first pleopod and slender, nearly unarmed appendix masculina on the second pleopod. These features suggest that the specimens are in an early stage of transitional phase ( Butler, 1980; Komai, 1999). Females are generally larger than those of transitional males, measuring 29.0– 35.6 mm in CL.

Etymology. This new species is dedicated to the late Boris G. Ivanov, in recognition of his contributions to the taxonomy of the decapod Crustacea. He was the supervisor of the second author.

Remarks. The new species is referred to the Pandalus hypsinotus group of Komai (1999), including eight species, viz., P. chani Komai, 1999 , P. hypsinotus , P. formosanus Komai, 1999 , P. gracilis Stimpson, 1860 , P. gurneyi Stimpson, 1871 , P. nipponensis Yokoya, 1933 , P. p re n s o r Stimpson, 1869, and P. teraoi Kubo, 1937 . It is very similar to P. hypsinotus in the morphology and the general coloration in life. Shared characters are: the number of spines of the dorsal rostral series could be within a range of 18–24, of which seven to nine spines are on the carapace; the posteriormost spine of the dorsal rostral series arises distinctly posterior to the midlength of the carapace; the postrostral ridge is markedly elevated, thus the dorsal margin of the carapace is convex; the pleon is banded with dark reddish brown. Counts of spines or spinules on segments of the pereopods also agree for each other. Because of the strong similarity between the two taxa, we have examined the syntypes of Pandalus hypsinotus (type locality: Unalaska; Brandt, 1851) in order to confirm the specific identity. The condition of the syntypes is poor, but characters necessary for species recognition are still preserved ( Fig. 7 View FIGURE 7 ). It was confirmed that the eastern Sakhalin shrimp is an undescribed species.

The new species differs from P. hypsinotus in variable but apparently significant morphological characters. The rostrum is more strongly curved (cf. Figs. 2 View FIGURE 2 A and 6B), and tends to be proportionally shorter in P. ivanovi than in P. hypsinotus although the values partly overlap ( Fig. 8 View FIGURE 8 ). The proportional value against the carapace length ranges 1.02–1.29 (1.12 on average, n=55) in P. ivanovi , and 1.19–1.58 (1.332 on average, n=43) in P. hypsinotus . The postrostral ridge in transitional males and females is distinctly lower in P. ivanovi than in P. hypsinotus . The development of the postrostral ridge shows an ontogenetic variation in P. hypsinotus (cf. Komai, 1999), and thus perhaps it will be not reliable in identifying functional males. The carpal articles of the left second pereopods are constantly fewer in Pandalus ivanovi than in P. hypsinotus (54–63 versus 72–85). The dactylus of the fifth pereopod seems to be more strongly curved in P. ivanovi than in P. hypsinotus . The coloration in life is also different between the two species (cf. Fig. 7 View FIGURE 7 A, B). The general body color is more reddish in the new species than in P. hypsinotus ; bands on the pleon are wider in P. ivanovi n. sp. than in P. hypsinotus . Furthermore, Pandalus ivanovi n. sp. is characterized by its relatively small size; the largest specimen of P. ivanovi is 35.6 mm in CL; female specimens, including ovigerous, are 27.3–35.6 mm. The maximum size appears considerably different in P. hypsinotus according to different populations. Female specimens from East Asia are 36.1–45.0 mm in CL, and the specimens of less than 36 mm in CL are all functional males or transitional individuals. On the other hand, the female specimens from Canada are 32.5–40.0 mm in CL.

It is interesting to note that the two separate populations of Pandalus hypsinotus show differences in the relative length of the rostrum and overall body size. The rostrum seems to be proportionally longer in the Asian population than in the Canadian population (1.29–1.57 times as long as the carapace versus 1.19–1.42), although the values partially overlap. The body size is larger in the Asian population than in the Canadian population (transitional males CL 36.6–42.3 mm, females CL 36.1–47.5 mm versus transitional males CL 31.0–33.0 mm, females CL 33.6–40.0 mm). Haynes (1976), who described the larval stages of Pandalus hypsinotus from Alaska, noted several morphological differences between his larvae and those described by Kurata (1964) from Hokkaido, Japan. Detailed comparison will be necessary if the geographically separated populations belong to a same species.

It remains unclear whether the new species is endemic to the Sea of Okhotsk. Nevertheless, in spite of our collecting efforts, no specimens of the new species have been encountered in the collections made during recent fishery or scientific surveys or those in museum collections.