Eudorella orientalis Akiyama & Gamô, 2012, sp. nov.

Eudorella orientalis sp. nov.

(Figs. 30, 31)

Material examined. Holotype, ovigerous female, 4.7 mm, dissected (NSMT-Cr 22147), off Kushiro, Hokkaido, 39° 31.50ˏ N, 142°32.82ˏ E – 39°32.03ˏ N, 142°33.57ˏ E, 1002–1069 m (KH-01-2, St. TD-2), 25 September, 2001. Paratypes; 3ovigerous females, 4.4–4.8 mm, dissected (NSMT-Cr 22148) (KT-01-2, St. TD-2); 2 preparatory females, 4.3 mm, 4.4 mm, dissected (NSMT-Cr 22149), off Kushiro, Hokkaido, 42°27.52ˏN, 144°14.47ˏE – 42°26.85ˏN, 144°12.98ˏE, 965–982 m (KH-01-2, St. XR-2-1), 15 September 2001; 2 preparatory females, 4.8 mm 1 specimen damaged), dissected, 2 adult males, 4.5 mm, 5.4 mm, dissected (NSMT-Cr 22150), Hiroo Canyon, off Hokkaido, 42°11ˏN, 144°11ˏE – 42°11ˏN, 144°12ˏE, 1134–1219 m (KH-01-2, St. KC-0), 18 September, 2001: 3 ovigerous females and 2 adult males, 4.3–4.8 mm, dissected (NSMT-Cr 22151), off Abashiri, Okhotsk Sea, 42°09.63ˏN, 144°05.96ˏ E – 44°09.39ˏN, 144°51.55ˏE, 495–508 m (KT-04-20, St. AB-4-2), 12 September, 2004. 6 ovigerous females, 2.9–3.5 mm, dissected (NSMT-Cr 22152), off Kamogawa, 34°59.11ˏN, 140°036.29ˏE, 104 m (KT-03-17, St. KG-1), 17 November 2003; 1 ovigerous female, 3.5 mm, dissected (NSMT-Cr 22153), off Tanabe, Kii Peninsula, 33°37.02ˏN, 135°07.90ˏE – 33°36.94ˏN, 135°07.99ˏE, 288.6–298m (KT-05-30, St. TN-2-2), 26 November 2005; 1 ovigerous female, 3.1 mm (NSMT-Cr 22154), Enshu Nada, 34°37.52ˏN, 137 °59.38ˏE–34° 37.46ˏN, 137°59.53ˏE, 52–62 m (KT-02-5, St. EN-4-1), 27 May 2002; 2 ovigerous females, 3.6 mm (NSMT-Cr 22155), Enshu Nada, 34°35.32ˏN, 137°58.54ˏE – 34°35.24ˏN, 137°58.82ˏE, 175–200 m (KT-02-5, St. EN-4-3), 27 May 2002; 2 ovigerous females, 3.6 mm (NSMT-Cr 22156), Enshu Nada, 34°35.32ˏN, 137°58.55ˏE – 34°35.43ˏN, 137°58.78ˏE, 168–193.5 m (KT-04-6, St. EN-2), 2 May, 2004; 2 ovigerous females, 3.4, 3.36 mm (NSMT-Cr 22157), off Omae-zaki 34°38.40ˏN, 138°16.92ˏE – 34°38.26ˏN, 138°17.06ˏE, 247–303 m (KT-04-6, St. SB-1), 25 May 2002;10 ovigerous females, 2 adult male (1 female specimen dissected) (NSMT-Cr 22158), Okinawa Trough, 29°38.4ˏN, 127°36.0ˏE – 29°39.1ˏN, 127°35.9ˏE, 524–575m (KT-04-23, St. D1-aˏ), 12 October, 2004.

Description. Specimens from northern Japan. 11 ovigerous and preparatory females (Fig. 30). Integument weakly calcified. Carapace length 0.19–0.21 times total body length and as long as greatest width, latter being 1.1– 1.3 times depth; upper front corner with a group of setae projecting forward or upward; frontal margin not serrated; antennal notch with 2–4 and 2–3 teeth on upper and lower end respectively; anterolateral angle with prominent tooth directed forward, succeeded by a series of teeth on inferior margin. Each side of carapace with a row of several simple setae behind pseudo rostral lobe (Fig. 30 C). Pereon length 1.2–1.4 times carapace. Pleon very slen- der, length 0.52–0.56 times total animal length; width of carapace 2.7–3.0 times width of pleonite 1; dorso-posterior end of 5th pleonite with no long setae.

Antenna 1 (Fig. 30 D) 1st article of peduncle short, with 1–2 and 3–4 plumose setae on lower and inner margin, respectively; 3rd article of peduncle shorter than 2nd, with 3–5 plumose setae and 1 simple seta on outer and 4–6 plumose setae on inner margin. Main flagellum subequal in length to 2nd article of peduncle, with 3–4 simple setae on outer margin of basal article. Accessory flagellum shorter than basal article of main flagellum. Antenna 2 (Fig. 30 E) with 3 plumose setae on outer margin. Maxilliped 1 (Fig. 32 I) with 6–8 branchial lobules on well developed branchial plate. Maxilliped 2 (Fig. 30 J) basis slightly longer than combined length of succeeding 3 articles, with no setae on its inner margin or ventral surface. Maxilliped 3 (Fig. 30 K) basis length 1.1–1.3 times combined length of distal articles, with 9–11 and 4–5 plumose setae on inner margin and ventral surface, respectively; ischium with no spines on inner margin; carpus with 6–8 plumose setae on inner margin.

Pereopod 1 (Fig. 30 L) basis 0.7–0.8 times as long as combined length of remaining distal articles, with 10–13 plumose setae on inner margin; propodus 1.2–1.6 times as long as carpus and 1.9–2.1 times dactylus. Pereopod 2 (Fig. 30 M) basis 0.8–1.0 times as long as combined length of distal articles, with 9–17 plumose setae on inner margin; carpus 1.1–1.2 times merus; combined length of propodus and dactylus 1.2–1.4 times that of carpus; distal end of propodus with deep notch for nearly entire length of article, dactylus not swollen, with 10–12 stiff long setae on inner margin and apical end. Pereopod 3–5 (Fig. 30 N–P) basis lengths 1.9–2.2, 1.6–1.9, 1.0–1.5 times remaining distal articles, respectively.

Uropod (Fig. 30 Q) peduncle length 1.5–1.8 times pleonite 6, 0.97–1.13 times exopod, 0.81–0.90 times endopod, with 5–8 short setae on inner margin; exopod length 1.10–1.26 times basal article of endopod, with 8–9 setae on inner surface and apical end, with 4–6 setae on both dorsal and ventral surfaces. Endopod 1st article length 2.6– 3.0 times 2nd, with 5–9 spiniform setae on inner margin and 2–4 simple setae on outer margin; 2nd article with 3– 4 spiniform setae on inner margin; robust terminal setae of endopod defined at base.

Adult males (Fig. 31). Body with few thin setae. Carapace length 0.21–0.22 times total body length and 1.2– 1.4 times greatest width, latter 1.0–1.2 times depth; frontal margin not serrated (Fig. 31 A, C); anterolateral angle with small tooth directed forward; inferior margin not serrated; each side of carapace, behind pseudorostral lobe, devoid of setae. Pereon 1.0–1.2 times that of carapace. Pleon slender, 0.53–0.55 times total body length, with 2 pairs of pleopods; greatest width of carapace 2.4–2.8 times width of pleonte 1; posterior margin of pleonite 6 protruding conically, extending beyond opening of anus (Fig. 31 M).

Antenna 1 (Fig. 31 D) basal article of peduncle with 1–2 and 3–4 plumose setae on lower and inner margin, respectively; 3rd article of peduncle much shorter than 2nd, with 2–5 plumose setae and 0–2 simple setae on outer margin, and 4–6 plumose setae on inner margin. Main flagellum 4-articulate; 1st article subequal to 2nd, and slightly longer than 3rd; numerous aesthetascs present on basal article; 2nd article with 2 simple setae. Distal end of accessory flagellum reaching middle portion of 2nd article of main flagellum. Antenna 2 with 4 plumose setae on basal region of peduncle (Fig. 31 E). Basis length of maxilliped 3 (Fig. 31 F) 1.5–1.6 times length of distal articles together, with 7–10 and 4–6 plumose setae on inner margin and ventral surface respectively.

Pereopod 1 (Fig. 31 G) basis length 0.9–1.0 times distal articles together, with 11–14 and 8–11 plumose setae on inner and outer margin respectively; propodus 1.2–1.6 times carpus and 2.1–2.4 times dactylus. Pereopod 2 (Fig. 31 H), basis 1.1–1.2 times distal articles together, with 9–11 plumose setae on inner margin; carpus 0.9–1.2 times merus; combined length of propodus and dactylus 1.2–1.5 times carpus. Pereopod 3–5 (Fig. 31 I–K) basis lengths 3.1–3.6, 2.4–2.7, 1.5–1.6 times distal articles together, respectively.

Uropod (Fig. 31 M) slender. Peduncle 1.3–1.6 times as long as pleonite 6, 0.80–0.95 times exopod, 0.73–0.81 times endopod, with 6–7 spiniform and 4–6 plumose setae on inner margin. Exopod length 1.06–1.22 times basal article of endopod, with 8 plumose setae on inner margin and apical end, 4–5 setae on dorsal surface, 4–6 setae on ventral surface. Basal article of endopod 2.8–3.1 times as long as 2nd, with 14–21 spiniform and 4–5 weakly ciliated setae on inner margin; 2nd article with 4–6 spiniform setae on inner margin; terminal setae defined at base.

Etymology. The species name refers to the locality in which the specimens were collected.

Remarks. Eudorella orientalis sp. nov., resembles E. pacifica Hart, 1930, which is distributed over a very wide area of the northeastern and northwestern Pacific (Hart 1930; Lomakina 1968; Barnard & Given 1961; Liu & Liu 1991; Watling & McCann 1997; Hong & Park 1999). The former species is distinguished from the latter by: (1) the carapace with a row of simple setae on each side (without these setae in E. pacifica); (2) the carpus of pereopod 2 subequal or slightly longer than the merus (1.5 times in E. pacifica); and (3) the uropod endopod 1st article being 1.9–3.0 times as long as 2nd article (over 3 times in E. pacifica). Eudorella orientalis also resembles E. truncatula from the northern Atlantic, but can be distinguished from the latter by: (1) the carapace of females has a row of setae on each side (these setae are absent in E. pacifica); (2) the side plates of pereonites 2 and 3 in ovigerous females are not well developed, the carapace length is 2.6–4.3 times pereonite 2 (about 2 times pereonite 2 in E. truncatula); and (3) the uropod exopod in adult males is longer than the endopod 1st article (shorter in E. truncatula). Eudorella orientaris also resembles E. setoensis Akiyama & Gamô, 2006 from the Seto Inland Sea of Japan (see Remarks on E. setoensis).

Eudorella orientalis is classified into 3 local populations: from northern Japan, 495–1219 m (4.3–4.8 mm in body length): the southern coast of Honshu, 104–303 m (2.9–3.6 mm): and the Okinawa Trough, East China Sea, 524–575 m (3.0– 3.2 mm). This is based on the following observed morphological variations in ovigerous females: (1) The pleon of specimens from northern Japan and the Okinawa Trough is slender, the greatest width of the carapace being 2.81 ± 0.12 (N=7) and 3.12 ± 0.15 (N=8) times the width of the 1st pleonite (while the specimens from southern Honshu, it is 2.49 ± 0.19 (N=14)). (2) The pereon of the East China Sea population is short, 1.03 ± 0.05 (N=8) times carapace length, 1.32 ± 0.10 (N=14) and 1.28 ± 0.10 (N=7) in the populations from Honshu and northern Japan respectively. (3) In the population from northern Japan, the basis of maxilliped 3 is longer than combined length of the distal articles, and the ischium with has spine on the inner margin, while in the other two populations, the basis as long as the distal articles combined, and the ischium has a spine on the inner margin.

Distribution. Japan, 52–1219 m.