Eudorella ohtai, Akiyama, Tadashi & Gamô, Sigeo, 2012

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 : 39-42

Eudorella ohtai sp. nov.

(Figs. 27–29)

Material examined. Holotype, preparatory female, 5.1 mm, dissected (NSMT-Cr 22144), Okinawa Trough, 26°51´N, 126°27´E – 26°49´N, 126°25´E, 1846–1870 m (KH05-1, St. OT-3), 12 May 2005. Paratypes; 1 juvenile female, 1 juvenile male, length 4.2 mm, 3.5 mm (NSMT-Cr 22145), (KH-05-1, St. OT-3); 1 juvenile male, pleon damaged, western slope of Ryukyu Trench, 26°17.04´N, 128°27.03´E – 26°17.76´E, 128°28.15´E, 1943–2013 m, (KH-05-1, St. PS-7), 24 May, 2005; 2 juvenile females, 5.4, 4.7 mm, dissected (NSMT-Cr 22146), off Todogasaki, Pacific coast of northern Honshu, 39°17ˏN, 143°47ˏE – 39°15ˏN, 143°47ˏE, 4718–4990 m (KH-01-2, St. TD-5), 26 September 2001.

Description. Holotype preparatory female (Fig. 27, 28). Body slender, with few thin setae. Carapace length 0.19 times total body length and 1.4 times greatest width, latter being 0.9 times the depth; frontal margin of carapace serrated up to nearly anterior end of siphon (Fig. 27C, D); lower end of antennal notch and frontal end of anterolateral angle located slightly behind frontal margin of carapace. Pereon length 1.2 times carapace length. Pleon 0.57 times total body length; dorso-posterior end of pleonite 6 with no long setae.

Antenna 1 (Fig. 27E) 1st article of peduncle with 0 and 2 plumose setae on lower margin and inner margin, respectively; 3rd article of peduncle shorter than 2nd, with 5 plumose setae and 1 simple seta on outer margin, 6 thick plumose setae on inner margin; main flagellum shorter than 2nd article of peduncle, with 3 plumose setae on outer margin of basal article. Accessory flagellum as long as 1st article of main flagellum. Antenna 2 (Fig. 27F) with 3 and 0 plumose setae on outer and lower margin, respectively. Mandibles, maxilla 1 and 2 normal (Fig. 27 G– I). Maxilliped 1 (Fig. 27J), branchial plate small, with 3 branchial lobules. Maxilliped 2 (Fig. 27K, L) basis much shorter than combined length of succeeding 3 articles, with short setae scattered on dorsal surface. Maxilliped 3 ( Fig. 28 A) basis length 0.9 times length of distal articles together, with 7 plumose setae on inner margin and 7 plumose setae on ventral surface; ischium with blunt spine on inner margin; carpus with 10 plumose setae on inner margin; terminal setae much longer than dactylus.

Pereopod 1 ( Fig. 28 B) 3rd–7th articles lost during collection. Basis with 5 plumose setae and 1 simple seta on inner margin and 9 short setae on outer margin; distal corner with 3 spiniform setae and 1 long plumose seta. Pereopod 2 ( Fig. 28 C) basis length 0.9 times length of distal articles together, with 6 plumose setae on inner margin; carpus length 1.5 times that of merus and 1.2 times combined length of propodus and dactylus; propodus length less than half that of merus, with a shallow notch on distal corner, reaching middle portion of article; dactylus not swollen, with 14 stiff setae on lateral margin and apical end. Pereopods 3 and 4 ( Fig. 28 D, E) basis length 2.0 and 1.5 times distal articles together, respectively. Pereopod 5 ( Fig. 28 F) basis 1.5 times distal articles together, with only 2 short setae and 3 auditory hairs.

Uropod ( Fig. 28 G) peduncle length 1.3 times that of pleonite 6, 0.90 times exopod, and 1.06 times 1st article of endopod, with 4 or 5 spiniform setae; exopod 1.17 times 1st article of endopod, with 8 or 9 setae on inner margin and apical end, with 5 setae on dorsal surface, and with 2 setae on ventral surface; 1st article of endopod 3.3 times 2nd, with 7 or 8 spiniform setae on inner margin and 3 simple setae on outer margin; 2nd article with 3 or 4 spiniform setae on inner margin; terminal setae of endopod defined at base.

27. Eudorella ohtai sp. nov., preparatory female. A, body, lateral view; B, anterior portion of body, from above; C, D, anterior portion of carapace; E, antenna 1; F, antenna 2; G, mandibles; H, maxilla 1; I, maxilla 2; J, maxilliped 1; K, L, maxilliped 2.

Paratype young females. Morphological characteristics of specimen similar to holotype female, except: main flagellum of antenna 1 ( Fig. 29 ) with 1 seta (arrowhead) on inner distal corner of basal article, in addition to 1–2 plumose setae on outer margin; uropod peduncle length 1.1 times length of exopod, the latter with 7 setae on its inner and apical margins and 3 setae on its dorsal surface. Uropod endopod damaged during collection.

Etymology. The species name is dedicated to Dr. Suguru Ohta, Director of the R/V Hakuho-maru KH-01-2 and KH-05-1 cruises, during which the specimens were collected.

Remarks. This new species and E. hirsuta (Sars 1869) from the Northeast Atlantic are distinguished from the other members of the genus by the frontal margin of the carapace being serrated up to near the siphon. The female specimen of Eudorella ohtai sp. nov., is distinguished from E. hirsuta as follows. (1) The upper front corner of the carapace has very short setae, and body has few thin setae (whereas in E. hirsuta the upper front corner of the carapace has numerous long setae). (2) The antennal notch with a tooth on lower end (3 teeth in E. hirsuta ). (3) The 1st article of the main flagellum of antenna 1 has plumose setae (simple setae in E. hirsuta ). (4) The carpus of pereopod 2 is 1.2 times the combined length of the propodus and dactylus, 1.7 times dactylus, with no plumose setae (about 1.5 times combined length of propodus and dactylus, 2.4 times dactylus, with a row of several plumose setae on inner margin in E. hirsuta ).

In the two specimens from northern Japan, the 1st article of the antenna 1 main flagellum is furnished with a seta on the inner margin, in addition to the normal 1–2 setae on the outer margin ( Fig. 29 ), which is unique in Japanese Eudorella . This additional seta may be a local morphological variation of this species. Other noteworthy characters of E. ohtai are: (1) maxilliped 1 has small, undeveloped branchial plate bearing 3 small lobules; and (2) the basis of maxilliped 2 has short setae scattered on the dorsal surface.

Distribution. Pacific coast of northern Honshu, Okinawa Trough, western slope of the Ryukyu Trench, 1846– 4890 m.

Figures

FIGURE 28. Eudorella ohtai sp. nov., preparatory female. A, maxilliped 3; B, basis of pereopod 1; C – F, pereopods 2 – 5; G, uropod with pleonite 6.

FIGURE 29. Eudorella ohtai sp. nov., antenna 1 of young female collected from Pacific coast of northern Japan. Arrow head indicates seta on inner margin of main flagellum basal article.