Research Article |
Corresponding author: Michitaka Shimomura ( shimomura@kmnh.jp ) Academic editor: Charles Oliver Coleman
© 2016 Michitaka Shimomura, Ko Tomikawa.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Shimomura M, Tomikawa K (2016) Epimeria abyssalis sp. n. from the Kuril-Kamchatka Trench (Crustacea, Amphipoda, Epimeriidae). ZooKeys 638: 125-142. https://doi.org/10.3897/zookeys.638.10329
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A new deep-sea epimeriid, Epimeria abyssalis is described from the Kuril-Kamchatka Trench, in the northwestern Pacific. This species differs from its congeners in having a short rostrum and a telson with deep and narrow Y-shaped excavation. Epimeria abyssalis is the deepest recorded Epimeria species. A key to the north Pacific species of Epimeria is provided.
Epimeria , Epimeriidae , Kuril-Kamchatka Trench
Epimeria Costa, 1851, is the largest genus of the family Epimeriidae Boeck, 1871 and includes 54 species (
This deep-sea survey yielded an undescribed species Epimeria from an abyssal zone of the Kuril-Kamchatka Trench, the northwestern Pacific, which is described and illustrated in this work.
Amphipod specimens were collected during a survey of deep-sea benthic fauna of northern Japan by the R/V “Hakuho-Maru” of the Ocean Research Institute, University of Tokyo in 2001 (now the ship belongs to Japan Agency for Marine-Earth Science and Technology), from station KH-01-02-XR-8 and XR-12. The gear used for the collection was an ORE beam trawl of 4 m span (mesh size approx. 5 mm). Samples were elutriated on board through a 0.5 mm mesh sieve. The specimens retained were fixed and preserved in 70% ethanol. Appendages of each individual were dissected and observed using a compound and stereo microscopes. Total length was measured from the tip of the head to the end of the telson. Terminology follows
Epimeria tricristata Costa in Hope, 1851 (= Gammarus corniger Fabricius, 1779)
Holotype. Ovigerous ♀ (53 mm) (
Paratypes. 1 ovigerous ♀ (47 mm) (
Rostrum (Fig.
Urosomites 1–3 (Fig.
Antenna 1 (Fig.
Epimeria abyssalis sp. n., holotype female: A left antenna 1, medial B basal part of left antenna 1, medial C left antenna 2, medial D basal part of left antenna 2, medial E basal part of left antenna 2, lateral F flagella of left antenna 2, medial G labium, dorsal H anterior part of labium, dorsal I left mandible, medial. Scale bars: 1 mm.
Labrum (= upper lip) (Fig.
Epimeria abyssalis sp. n., holotype female: A molar process, incisor, lacinia mobilis and setal row of left mandible, dorsal B molar process of left mandible, dorsal C seta of setal row of left mandible, dorsal D right mandible, medial E molar process, incisor and setal row of right mandible, dorsal. Scale bars: 1 mm.
Epimeria abyssalis sp. n., holotype female: A left maxilla 1, dorsal B articles 1 and 2 of palp of left maxilla 1, dorsal C seta on article 2 of palp of left maxilla 1, dorsal D seta on outer plate of left maxilla 1, dorsal E seta on inner plate of left maxilla 1, dorsal F left maxilla 2, dorsal G seta on outer plate of left maxilla 2, dorsal H seta on outer plate of left maxilla 2, dorsal I seta on inner plate of left maxilla 2, dorsal J lower lip, dorsal. Scale bars: 1 mm.
Epimeria abyssalis sp. n., holotype female: A left maxilliped, ventral B left maxilliped, dorsal (omitted setae excluding setae on inner plates), dorsal C article 4 of left maxillipedal palp, ventral D seta on article 2 of left maxillipedal palp, ventral E seta on inner plate of left maxilliped, dorsal F seta on inner plate of left maxilliped, dorsal. Scale bars: 1 mm.
Gnathopod 1 (Figs
Epimeria abyssalis sp. n., holotype female: A left pereopod 1, lateral B distal part of propodus and dactylus of left pereopod 1, medial C left pereopod 2, lateral D distal part of propodus and dactylus of left pereopod 2, medial E left pereopod 3, lateral F distal part of left pereopod 3, lateral G seta on carpus of left pereopod 3, lateral. Scale bars: 1 mm.
Gnathopod 2 (Figs
Pereopod 3 (Figs
Pereopod 4 (Figs
Pereopod 5 (Figs
Pereopod 6 (Figs
Pereopod 7 (Figs
Epimeria abyssalis sp. n., holotype female: A left pereopod 7, lateral B distal part of propodus of left pereopod 7, lateral C left pleopod 1, dorsal D coupling hooks on peduncle of left pleopod 1, dorsal E seta on peduncle of left pleopod 1, dorsal F seta on outer ramus of left pleopod 1, dorsal. Scale bars: 1 mm.
Coxal gills on gnathopod 2 and pereopods 3–7 (Figs
Pleopods 1–3 (Fig.
Uropod 1 (Fig.
Uropod 2 (Fig.
Uropod 3 (Fig.
Telson (Fig.
(
Telson (Fig.
Epimeria abyssalis sp. n. can be identified and separated from other species of the genus by the following combination of characters: rostrum short, 0.2 times as long as head; eyes absent; pereonites 1–7 without dorsal carinae; palmar margins of propodi of gnathopods 1–2 transverse, strongly serrate; coxae 1–3 each with blunt apex; coxa 4 produced into posterodistal cusp directed posterodistally, laterally projected at mid part; anterior margin of coxa 4 slightly concave; coxa 5 as wide as coxa 4, subrectangular, without anterodistal and posterodistal projections; anterior margin of coxa 5 broadly rounded; basis of pereopod 7 broadest, as long as basis of pereopod 6, 1.6 times as wide as basis of pereopod 6; and telson 1.5 times as long as wide, with deep and narrow Y-shaped excavation, without setae.
Epimeria abyssalis sp. n. is close to E. pelagica and E. yaquinae, with which it shares a short rostrum, pereon without dorsal carinae, and coxa 5 lacking posterodistal projection are shared by E. pelagica and E. yaquinae. Epimeria abyssalis is distinguished from E. pelagica by the following features (those of E. pelagica in parentheses): eyes absent (present); article 1 of antenna 1 twice as long as wide (as long as wide); posterodistal angle of propodi of gnathopods 1 and 2 nearly right angle squared, (obtuse angle); coxa 3 blunt distally (pointed distally); coxa 4 moderately broad at basal part (narrow); propodi of pereopods 5 and 6 moderately short, 1.4 times as long as carpi (long, 1.7–1.9 times as long as carpi); basis of pereopod 7 broad, posterior margin convex (narrow, posterior margin slightly concave); inner ramus of uropod 1 broad, as long as outer ramus (narrow, shorter than outer ramus); and telson with deep and narrow Y-shaped excavation, without setae (deep and broad V-shaped excavation, with two pairs of setae distally). Epimeria abyssalis differs from E. yaquinae in the following features (those of E. yaquinae in parentheses): palmar margins of propodi of gnathopods 1 and 2 without projections (with pointed projections); labrum with shallow notch distally (without notch); uropod 3 slightly shorter than uropod 2 (longer than uropod 2); rami of uropod 2 broad (narrow); and telson with deep and narrow Y-shaped excavation (deep and broad V-shaped excavation).
Epimeria abyssalis is the deepest recorded Epimeria species. Epimeria was previously known down to 3710 m (Epimeria glaucosa J.L. Barnard, 1961).
Species name was derived from abyssus (L.) referring to its deep-water habitat.
1 | Rostrum short, not reaching half the length of article 1 of antenna 1; coxa 5 lacking posterodistal projection | 2 |
– | Rostrum long, reaching half the length of article 1 of antenna 1; coxa 5 with posterodistal projection | 4 |
2 | Telson with deep and broad V-shaped excavation | 3 |
– | Telson with deep and narrow Y-shaped excavation | E. abyssalis sp. n. |
3 | Eyes absent; palmar margins of gnathopods 1 and 2 with posterior projection; coxa 4 rounded distally | E. yaquinae |
– | Eyes present; palmar margins of gnathopods 1 and 2 without posterior projections; coxa 4 pointed distally | E. pelagica |
4 | Eyes present | 5 |
– | Eyes absent | E. subcarinata |
5 | Coxa 5 projection nearly reaching epimeral plate 1 | 6 |
– | Coxa 5 projection not reaching epimeral plate 1 | E. cora |
6 | Head ventral lobe not produced, | 7 |
– | Head ventral lobe produced | E. pacifica |
7 | Telson 1.2 times as long as wide; uropodal peduncle longer than rami | E. morronei |
– | Telson as long as wide; uropodal peduncle shorter than rami | E. ortizi |
We are grateful to Prof. Emeritus S. Ohta (University of Tokyo, Tokyo), director of the cruise and who facilitated the collection of the amphipod specimens. We would like to thank to the crew of the R/V “Hakuho-Maru” of the Ocean Research Institute, University of Tokyo, for their cooperation at sea. Also, many thanks are given to Dr. C. O. Coleman (Museum für Naturkunde), Dr. C. d’Udekem d’Acoz (Royal Belgian Institute of Natural Sciences), and an anonymous reviewer, for their valuable comments and suggestions on the manuscript. This research was supported in part by KAKENHI.