Eudorella aequiremis Hansen, 1920

Akiyama, Tadashi & Gamô, Sigeo, 2012, The cumacean Genus Eudorella (Crustacea: Peracarida) from Japanese Waters, Northwest Pacific, and E. suluensis sp. nov. from the Sulu Sea, Indo-West Pacific, Zootaxa 3319, pp. 1-56 : 7-11

Eudorella aequiremis Hansen, 1920

( Figs. 4–6 )

Eudorella aequiremis Hansen 1920: 27 , pl. 2, fig. 3a–d; Lomakina 1958: 223 –224, fig. 141.

Material examined. 1 ovigerous female, 3.8 mm (pleonite 6 damaged), 3 preparatory females, 3.9–4.6 mm; 1 young female, 4.0 mm; subadult male, 3.1 mm (pleonites 5 and 6 lost), 6 young males, 2.8–3.8 mm, 2 male manca larvae, length 2.4 mm (NSMT-Cr 22097); south of Kushiro, 42˚13ˏN, 145˚34ˏE – 42˚12ˏN, 145˚32ˏE, 3821–3851 m (KH-01-2, St. XR-7), 17 September, 2001; 1 preparatory female, abdomen lost (NSMT-Cr 22098), south of Kushiro, 42 23.83ˏN 145 31.06ˏE – 42 22.00ˏN, 145 27.70ˏE, 3108–3265 m (KH-01-2, St. XR-5), 16 September, 2001; 2 young males, 3.1 mm (NSMT-Cr 22099), off Todogasaki, 39°27ˏN, 143°38ˏE – 39°29ˏN, 143°39ˏE, 3110– 3290 m, (KH-01-2, St. TD-4), 26 September, 2001; 1 young female, 4.0 mm (NSMT-Cr 22100), off Todogasaki, 39°16ˏN, 144°45ˏE – 39°17ˏN, 144°42ˏE, 5573–5773 m (KH-01-2, St. TD-8), 29 September, 2001.

Description. Females (5 specimens; 3.9, 4.2, 4.6 mm in length except for 2 specimens with damaged pleon). Ovigerous female ( Figs. 4 , 5 ) carrying 4 eggs (1– 2 eggs possibly detached during collection). Integument moderately calcified. Carapace 0.21–0.22 times total body length, 1.2–1.3 times greatest width, latter being 1.0–1.1 times depth; frontal margin above antennal notch markedly serrated with 8–11 teeth ( Fig. 4 C); lower end of antennal notch with 1 tooth; between antennal notch and round anterolateral angle there is existing narrow gap without a tooth ( Fig. 4 C); anterior portion of inferior margin with 12–15 teeth. Pereon 1.0–1.1 times carapace ( Fig. 4 A). Pleon slender, 0.54–0.56 times total body length. Width of carapace 2.6–2.9 times width of 1st pleonite. Dorso-posterior end of 5th pleonite with no long seta.

Antenna 1 ( Fig. 4 D) 1st article of peduncle with 1–2 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 margin and 3–4 plumose setae on inner margin, 1–2 plumose setae or simple seta on frontal margin; main flagellum subequal in length to 2nd pedunclar article, with 2 setae, plumose or simple, on outer margin of basal article; accessory flagellum shorter than 1st article of main flagellum. Antenna 2 ( Fig. 4 E) with 3 plumose setae on outer margin of basal region, and with no setae on lower margin. Maxilliped 1 ( Fig. 4 I) with 3–4 branchial lobules. Maxilliped 2 ( Fig. 4 J) basis much shorter than combined length of succeeding 3 articles, with no setae on inner margin. Maxilliped 3 ( Fig. 4 K) basis, 0.9–1.0 times distal articles combined, with 7–9 and 3–5 plumose setae on inner margin and ventral surface, respectively; ischium without spine on inner margin; carpus with 5–7 plumose setae on inner margin.

Pereopod 1 ( Fig. 4 L) basis length 0.6–0.7 times distal articles together, with 9–13 plumose setae on inner margin and 4–6 plumose setae on outer margin; ischium with minute spine at distal corner; propodus 1.2–1.4 times carpus and 1.7–2.0 times dactylus. Pereopod 2 ( Fig. 5 A) basis 0.7–0.8 times distal articles combined; carpus 13–1.5 times merus and 0.8 times combined length of propodus and dactylus; propodus with deep notch on distal corner for nearly entire length of article; dactylus not swollen distally, with 9–11 stiff setae on its apical end and lateral margin. Pereopod 3 ( Fig. 5 B) basis 1.9–2.2 times as long as distal articles combined. Pereopod 4 ( Fig. 5 C) basis 1.5–1.9 times the distal articles combined, almost simple except for 1 seta on distal end. Pereopod 5 ( Fig. 5 D) basis 1.2–1.4 times distal articles combined with several short setae and auditory hairs.

Uropod ( Fig. 5 E) peduncle length 1.0–1.5 times pleonite 6, 0.75–0.98 times exopod, 0.88–1.06 times endopod, with 4 spiniform setae on inner margin. Exopod 1.04–1.17 times endopod, with 7 setae on inner margin and distal end, 3–5 setae on dorsal surface, 4–5 setae on outer margin. Endopod 1st article 2.0–2.3 times 2nd, with 6 spiniform setae on inner margin and 1 seta on outer margin; 2nd article with1–2 spiniform setae on inner margin; terminal setae robust, long, defined at base.

Subadult male ( Fig. 6 ). Length of carapace 1.5 times greatest width and depth; shape of carapace similar to females except that antennal notch absent ( Fig. 6 C). Pereon length 1.0 times carapace. Pleonite 5 and 6 lost during collection.

Antenna 1 ( Fig. 6 D) similar to that of female. Antenna 2 ( Fig. 6 E) with long flagellum, with 3 plumose setae on outer margin of basal region. Maxilliped 3 ( Fig. 6 F) basis length 1.1 times distal articles combined with 8 plumose setae on inner margin and 3 plumose setae on ventral surface; ischium without spine on inner margin.

Pereopod 1 ( Fig. 6 G) basis length 0.8 times distal articles combined: propodus 1.2 times carpus and 1.7 times dactylus. Pereopod 2 ( Fig. 6 H) basis as long as distal articles combined, with 9 setae on inner margin; carpus 1.4 times merus and 0.9 times combined length of propodus and dactylus. Pereopods 3–5 ( Fig. 6 I–K) basis 2.4, 2.3 and 1.6 times distal articles combined, respectively. Pleopod 1 ( Fig. 6 L) undeveloped.

Uropod lost during collection.

Remarks. Since the original description by Hansen (1920) from Davis Strait, western Atlantic, 2660 m depth, no additional specimen of this species has been reported. This species and E. arctica Hansen, 1920 are distinguished from the other species in the genus by the uropod endopod length which does not exceed that of the exopod ( Hansen 1920). Eudorella aequiremis is distinguished from E. arctica by the serrated frontal margin of its carapace and elongated carpus of pereopod 2. The Japanese specimens show different morphological characters from those of specimens from Davis Strait (inside the parentheses indicates the characteristics of the specimen from Davis Strait); (1) entire row of teeth on frontal margin of carapace marked (teeth on the middle portion minute), and (2) combined length of propodus and dactylus of pereopod 2 obviously longer than carpus, (equal in length or slightly longer than carpus), and (3) uropod exopod with 3–5 simple setae on outer margin (no setae). Based on these characters, it is possible that the Japanese specimens represent an undescribed species. However, additional specimens from other localities are needed for further study on this point.

Distribution. Davis Strait, western Atlantic, Pacific coast of northern Japan, 2660–5773 m.

Figures

FIGURE 4. Eudorella aequiremis Hansen, 1920, ovigerous female (H – K, preparatory female). A, body, lateral view, without last pleonite; B: anterior portion of body, from above; C, anterior portion of carapace, lateral view; D, antenna 1; E, antenna 2; F, mandibles; G, maxilla 1; H, maxilla 2; I – K, maxillipeds 1 – 3; L, pereopod 1.

FIGURE 5. Eudorella aequiremis Hansen, 1920. A – G, ovigerous female; H, preparatory female. A – D, pereopods 1 – 4; E, uropod with pleonite 6.

FIGURE 6. Eudorella aequiremis Hansen, 1920, subadult male (fifth and sixth pleonites and uropods lost). A, body, lateral view; B, anterior portion of body from above; C, anterior portion of carapace, lateral view; D, antenna 1; E, antenna 2; F, maxillipeds 3; G – K, pereopods 1 – 5; L, pleopod 1.