Eudorella dentata Lomakina, 1955

(Figs. 15–17)

Eudorella dentata Lomakina, 1955: 120 –122, figs. 20–22; Lomakina 1958: 226 –228, fig. 145; Akiyama 2009: 486.

Material examined. 4 preparatory females, 6.2–6.9 mm, dissected; 1 subadult male, 6.1 mm, 1 young female, 4.7 mm (NSMT-Cr 22124), off Kushiro, 42°28ˏN,144°15ˏE – 42°27ˏN, 144°13ˏE, 965–982 m (KH-01-2, St. XR-2), 15 September, 2001; 2 preparatory females, 6.1, 6.3 mm, dissected, 2 subadult males, 6.2, 6.5 mm, 1 young male, 5.2 mm (NSMT-Cr 22125), Hiroo Canyon, off Hokkaido, 42°11ˏN, 144°11ˏE – 42°11ˏN, 144°12ˏE, 1134–1219 m (KH-01-2, St. KC-0), 18 September, 2001; 1 young female, length 4.6 mm (NSMT-Cr 22126), off Todogasaki, 39°31ˏN, 142°32ˏE – 39°32ˏN, 142° 34ˏE, 1002–1069 m (KH-01-2, St. TD-2), 25 September, 2001.

Description. Preparatory females (Figs. 15, 16). Body moderately calcified. Carapace length 0.20–0.21 times body length, slightly longer than greatest width and depth; upper front corner with a bundle of short hairs projecting upward; frontal margin not serrated; triangular antennal notch shallow, with 2 teeth each on upper and lower ends (Fig. 15 C). Anterolateral angle with 2 prominent teeth, one directed upward and the other downward, succeeded by 8 teeth on inferior margin. Pereon length 1.3 times carapace length. Pleon rather thick, 0.53–0.57 times total body length. Dorso-posterior end of 5th pleonite with a bundle of long setae.

Antenna 1 (Fig. 15 D) 3rd article of peduncle shorter than 2nd, with 3–4 plumose setae and 1 simple seta on outer margin, 4–5 plumose setae and 1 plumose seta on inner and anterior margins, respectively; 1st article of peduncle with 1–3 and 2–3 plumose setae on lower and inner margins, respectively. Main flagellum shorter than 2nd article of peduncle and longer than the 3rd, with 2–3 simple setae on outer margin of 1st article. Accessory flagellum slightly longer than 1st article of main flagellum. Antenna 2 (Fig. 15 E) with 3 plumose setae on outer margin. Mandibles, maxilla 1 and maxilla 2 are normal (Fig. 15 F–H). Maxilliped 1 (Fig. 15 I) with 6–8 branchial lobules, branchial plate well developed. Maxilliped 2 (Fig. 15 J), basis much longer than combined length of ischium, merus and carpus, with several simple setae on inner margin; carpus with about 10 plumose setae on inner margin. Maxilliped 3 (Fig. 15 K) basis length 1.3–1.5 times length of distal articles combined, 7–9 and 4–9 plumose setae on inner margin and ventral surface, respectively; ischium with a stout spine on inner margin; carpus with 4– 5 setae on inner margin.

Pereopod 1 (Fig. 16 A) basis length 0.8–0.9 times length of distal articles combined, with 8–11 and 6–9 plumose setae on inner and outer margins, respectively; propodus much longer than merus; dactylus 0.5–0.6 times carpus. Pereopod 2 (Fig. 16 B) basis length 0.9–1.0 times length of distal articles combined; carpus subequal in length to merus; propodus with shallow notch on distal corner, reaching about middle portion of article; dactylus not swollen, as long as carpus and 2.9–3.8 times propodus, with 9–10 stiff setae projecting radially. Pereopod 3 (Fig. 16 C) basis 2.0–2.4 times length remaining distal articles, with 5 plumose setae on inner margin. Pereopod 4 (Fig. 16 D), basis 1.1–1.5 times distal articles combined. Pereopod 5 (Fig. 16 E), basis 0.8–1.1 times distal articles combined (Fig. 16 E).

Uropod (Fig. 16 F) peduncle length 1.3–1.5 times that of pleonite 6, 1.12–1.34 times exopod, 0.92–1.01 times 1st article of endopod, with 5–9 spiniform setae on inner margin. Exopod 0.94–1.01 times 1st article of endopod, with 7–8 plumose and 3–4 simple setae on inner margin and dorsal surface, respectively. Endopod 1st article 3.0– 3.6 times 2nd, with 6–10 spiniform setae on inner margin and 3–5 simple setae on outer margin; 2nd article subequal to robust terminal setae, with 3–4 and 1 spiniform setae on inner and outer margins, respectively.

Subadult males 6.1–6.5 mm in length (Fig. 17). Carapace 0.21–0.22 times as long as total body length, 1.2–1.3 times greatest width, the latter being 1.0–1.1 times depth; upper front corner with a bundle of short hairs projecting upward; antennal notch absent; anterolateral angle large with 2 prominent teeth, succeeded by a series of 7–10 teeth on inferior margin (Fig. 17 C). Pereon 1.1–1.2 times carapace. Pleon 0.55 times total body length; dorso-posterior end of 5th pleonite with several long setae.

Antenna 1 (Fig. 17 D) 3rd article of peduncle much shorter than 2nd, with 2–4 plumose and 1–3 simple setae on outer, 4 plumose setae on inner, and 1 plumose seta on anterior margin; 1st article of peduncle with 2 and 3–4 plumose setae on its lower and inner margins, respectively. Main flagellum shorter than 2nd joint of peduncle and longer than 3rd, with 2–3 plumose or simple setae on outer margin of basal article. Accessory flagellum slightly longer than 1st article of main flagellum. Antenna 2 (Fig. 17 E) proximal region of peduncle with 3 plumose setae; flagellum reaching middle portion of 4th pereonite. Maxilliped 3 (Fig. 17 F) basis length 1.5–1.6 times length of distal articles together, with 8–9 and 4–5 plumose setae on inner margin and ventral surface respectively; ischium with a stout spine on inner margin.

Pereopod 1 (Fig. 17 G) basis length 1.0 times length of distal articles combined, with 9–14 and 7–9 plumose setae on inner and outer margins, respectively; propodus longer than merus; dactylus length about 0.5–0.6 times as carpus length. Pereopod 2 (Fig. 17 H) basis 1.1–1.2 times distal articles combined, with 12–13 plumose setae on inner margin; carpus 0.9–1.1 times length of merus; dactylus 1.1–1.3 times as long as carpus and 3.3–3.9 times as long as propodus, with 9–10 stiff simple setae projecting radially. Pereopods 3–5 (Fig. 17 I–K) basis 2.8–3.0, 1.9– 2.3, 1.0–1.2 times distal articles combined, respectively.

Uropod (Fig. 17 M). Peduncle length 1.3–1.4 times that of pleonite 6, 1.11–1.16 times exopod, 0.87–0.98 times endopod, with 6–8 spiniform setae on inner margin. Exopod as long as 1st article of endopod, with 9 and 3–4 simple setae on inner margin and dorsal surface respectively. Endopod 1st article length 3.3–3.6 times 2nd article and 0.9 times peduncle, with 11 spiniform setae on inner margin and 4 simple setae on outer margin, 2nd article with 4 spiniform setae and 1 simple seta on inner and outer margins, respectively.

Remarks. Eudorella dentata is distinguishable from the other members of the genus by the two prominent teeth on the anterolateral angle of the carapace directed upward and slightly downward, except for E. truncatula (Bate 1856), which is found in the northern Atlantic and shows variation in this character (see illustrations by Sars 1879, 1900). The former species is distinguished from the latter as follows. (1) The dorso-posterior end of pleonite 5 is furnished with several long setae (no seta in E. truncatula). (2) The basis of maxilliped 2 is much longer than the combined length of the ischium, merus and carpus, with several setae on the inner margin (shorter than combined length of succeeding 3 articles, with no seta on inner margin in E. truncatula). (3) The basis of maxilliped 3 is much longer than the combined length of the distal articles (subequal in length in E. truncatula).

Other noteworthy characters of E. dentata are: (1) the accessory flagellum of antenna 1 is slightly longer than the 1st article of the main flagellum; (2) the propodus of pereopod 2 has a shallow notch on the distal corner; and (3) the posterior end of pleonite 6 in male specimens is weakly pointed. The depth of the habitat in northern Japan was deeper than that on the eastern coast of Russia, which is located in a colder latitude.

Distribution. Eastern coast of Russia, northern Japan, Northeast Pacific, 45–1219 m.