Petalosarsia gamoi, Akiyama, Tadashi & Gerken, Sarah, 2012

Akiyama, Tadashi & Gerken, Sarah, 2012, The Cumacean (Crustacea: Peracarida) Genus Petalosarsia (Pseudocumatidae) from the Pacific Ocean, Zootaxa 3320, pp. 1-35 : 15-19

Petalosarsia gamoi sp. nov.

( Figs. 10–12 )

Material examined. Holotype ovigerous female, 5.02 mm (NSMT-Cr 22078), Tosa Bay, 32°48.0ˏN, 133°46.6ˏE – 32°47.6ˏN, 133°45.4ˏE, 1053–1056 m (KT00-8, St. BT-4), 27 June 1999. Paratypes; 1 ovigerous female, 4.33 mm (dissected), 1 adult male, 3.90 mm, (KT00-8, St. BT-4); 1 ovigerous female, 5.02 mm (dissected), 1 manca larva (NSMT-Cr 22079), Tosa Bay, 32°57.6ˏN, 133°44.7ˏE – 32°57.6ˏN, 133°42.0ˏE, 994–1001 m (KT-00-8, St. BT-3), 25 June 2000; 2 ovigerous females, 5.48 m, 4.81 mm (dissected), 1 adult male, 4.79 mm (dissected), 1 preparatory female, 1 subadult male, 2 juveniles, 1 manca larva (NSMT-Cr 22080), Hyuga Basin, 32°23.4ˏN, 132°15.1ˏE – 32°25.2ˏN, 132°17.2ˏE, 1501–1516 m (KT-99-18, St. BT-4), 16 December, 1999; 1 ovigerous female, 4.81 mm (dissected) (NSMT-Cr 22081), Kumano Basin, 33°43.7ˏN, 136°46.2ˏE – 33°44.3ˏN, 136°47.6ˏE, 1966–1989 m (KT-04-6, St. KN-8-2), 2 May, 2005; 1 ovigerous female, 3.80 mm (NSMT-Cr 22082), 08°05.97ˏN, 118°20.78ˏE – 08°06.70ˏN, 118°20.43ˏE, 514–516 m (KH-02-4, St. 7A), 23 November 2002.

Other material. 1 preparatory female, Kumano Basin, 33°50.0ˏN, 136°32.6ˏE – 33°50.0ˏN, 136°28.9ˏE, 1947–2023 m (KT-99-18, St. BT-9), 20 December 1999; 1 preparatory female, 34°25.98ˏN, 139°52.32ˏE – 34°24.64ˏN, 139°52.36ˏE, 1478–1492 m (KT-02-5, St. MY) 28 May 2002; 1 preparatory female, 2 subadult males, 1 juvenile, 1 manca larva, off Chiba, 35°01.72ˏN, 140°47.89ˏE – 35°03.12ˏN, 140°49.14ˏE, 1160–1219 m (KT-01- 8, St. TK-2), 23 June 2001; 1 juvenile, 1 manca larva, Shima Spur, 33°59.33ˏN, 136°51.25ˏE – 33°58.29ˏN, 136°51.43ˏE, 857–918 m (KT-05-30, St. KB-1-4), 24 November, 2005; 1 subadult male, Kumano Basin, 33°45.87ˏN, 136°42.01ˏE – 33°46.89ˏN, 136°42.65ˏE, 1910–2011 m (KT-05-30, St. KB-2-2), 24 November 2005; 1 preparatory female, Hyuga Basin, 32°16.97ˏN, 132°28.96ˏE – 32°19.23ˏN, 132°30.75ˏE, 1651–1677 m (KT-07- 1, St. HB-1), 22 February 2007; 1 subadult male, Tosa Basin, 32°57.29ˏN, 133°43.90ˏE – 32°57.03ˏN, 133°45.50ˏE, 1009–1222 m (KT-07-1, St. TB-1-3), 21 February 2007; 1 preparatory female, 1 juvenile, west of Okinawa Isl., 26°27.06ˏN, 127°32.25ˏE – 26°27.50ˏN, 127°32.10ˏE, 641–650 m (TY06, St. 8), 27 May 2006; 3 preparatory females, 29°19.14ˏN, 127°40.87ˏE, 1017 m (N275, St. Q), 30 November 2008; 1 ovigerous female, 28°34.07ˏN, 127°02.62ˏE, 608 m (N295, St. R2-1), 19 November 2009. 1 adult male, 4.62 mm, Okinawa Trough 26°11.34ˏN, 124°54.27ˏE – 26°12.65ˏN, 124°55.47ˏE, 1493–1533 m (KT-02-3, St. E-1), 26 April 2002.

Description. Ovigerous females ( Figs. 10 , 11 ). Body well calcified, carapace with numerous small depressions, length 1.36–1.57 times width, length 1.87–1.99 times depth, length 0.28–0.30 times total body length. Dorsal surface surrounded by a pair of marked dorsolateral carina running entire length of each side, and a transverse ridge near hind margin, dorsolateral carina curved slightly outward at side of frontal lobe, with 9–13 teeth on anterior portion; just below row of teeth, shallow depression like sulcus present; transverse ridge present near hind margin of each side; width of anterior portion of pseudorostral lobes, between foremost teeth of left and right dorsolateral carina, 0.47–0.51 times greatest width of carapace; pseudorostrum long and acute, 0.21–0.25 times length of carapace; inferior margin smooth; anterolateral angle and antennal notch obsolete. Width of triangular eye lobe 0.125– 0.16 times width of carapace. Pereon 0.57–0.66 times carapace; side plates of pereonite 1–3 well developed. Pleon 0.51–0.53 times total body length.

Antenna 1 ( Fig. 10 C) 1st article of peduncle1.2–1.5 times combined length of 2nd and 3rd articles; distal end of 2nd article fringed with thin, broad collar exceeding joint between 2nd and 3rd articles; main flagellum tri-articulate, 0.5–0.6 times 1st article of peduncle; 1st article of main flagellum 1.1–1.6 times combined length of 2nd and 3rd; accessory flagellum minute. Antenna 2 ( Fig. 10 D) bi-articulate, with a plumose seta on distal end of each article. Labium with fine hairs and minute hook-like setae on inner margin ( Fig. 10 E). Mandibles, maxilla 1 and 2 are normal for the genus ( Fig. 10 F–H). Maxilliped 1 ( Fig. 10 I) with 1 branchial lobule; basal article longer than combined length of remaining distal articles. Maxilliped 2 ( Fig. 10 J) basis, 1.05–1.2 times combined length of ischium, merus, carpus and propodus, with a round plate on ventral surface, without spines near distal end. Maxilliped 3 ( Fig. 10 K) basis 1.1–1.2 times distal articles together, with 2–3 plumose setae on inner margin; carpus with 3–4 setae on inner margin.

Pereopod 1 ( Fig. 10 L) basis 1.2–1.35 times combined length of ischium and carpus, with 6–8 plumose setae on inner margin; length of carpus 2.0–2.2 times width and 2.4–2.7 times dactylus length, 0.61–0.70 times basis length. Pereopod 2 ( Fig.10 M), basis 0.8–0.9 times distal articles together, with 1–2 plumose setae on inner margin; dactylus longer than carpus. Pereopod 3 ( Fig. 11 A) basis 1.9–2.1 times length of remaining distal articles, with 2–5 long and several short plumose setae; exopod absent except for a pair of remnant terminal setae. Pereopod 4 ( Fig. 11 B) basis 1.3–1.4 times length of remaining distal articles, with 0–1 plumose seta; exopod absent. Pereopod 5 ( Fig. 11 C) basis 0.6–0.8 times length of remaining distal articles.

Uropod ( Fig. 11 D), peduncle 1.26–1.32 times pleonite 6 length, 0.59–0.67 times exopod length and 0.48–0.55 times endopod length; exopod 0.81–0.86 times endopod length, with 3 setae near apical end, terminal one thick and long; endopod with 5–7 spiniform setae on inner margin, 2 terminal setae. Telson 0.34–0.46 times pleonite 6 length.

Adult male ( Fig. 12 ). Carapace length 0.32 times total body length, length 1.72 times greatest width and 2.23 times depth; only anterior portion with lateral carina, with 5 teeth; hind margin of dorsal surface without ridge; frontal margin between lateral carina 0.70 times greatest width; pseudorostrum 0.162 times length of carapace; width of eye lobe 0.15 times width of carapace. Pereon 0.53 times carapace. Pleon 0.52 times total body length, with 2 pairs of pleopods. Pleonites 1–6 with groove on ventral surface, very shallow on pleonite 6.

Antenna 1 ( Fig. 12 C) basal article of peduncle 1.2 times combined length of 2nd and 3rd; main flagellum of 5 articles; 1st article with 13 aesthetascs; accessory flagellum of 3 articles, subequal in length to proximal 3 articles of main flagellum combined. Antenna 2 ( Fig. 12 D) peduncle with plumose seta; flagellum short, reaching middle portion of pleonite 3, of 22 articles. Maxilliped 3 ( Fig. 12 E) basis 1.3 times remaining distal articles, with 6 plumose setae on inner margin.

Pereopod 1 ( Fig. 12 F) basis 1.4 times combined length of ischium and carpus; carpus length 1.8 times width, 2.4 times dactylus length, 0.60 times basis length. Pereopod 2 ( Fig. 12 G) basis 0.9 times length of remaining distal articles. Pereopods 3, 4 ( Fig. 12 H, I) basis broad at base, 2.0 and 1.4 times remaining distal articles respectively. Pereopod 5 ( Fig. 12 J) basis 0.8 times remaining distal articles. Pleopod 1 ( Fig. 12 K) outer and inner ramus fused; outer ramus with 2 stiff and long, almost naked seta on ventral side and 2 robust, short naked seta (arrow heads) on dorsal side; inner ramus with 5 plumose setae (1 of them stiff and almost naked); inner margin of basal article with 6 plumose setae. Pleopod 2 ( Fig. 12 L) rudimentary.

Uropod ( Fig. 12 M) peduncle 1.48 times pleonite 6 length, 0.52 times exopod length and 0.41 times endopod length; exopod 0.80 times endopod; endopod with 8 or 9 spiniform setae on inner margin. Telson ( Fig. 12 M) triangular shape, 0.72 times pleonite 6.

Etymology. The species name is dedicated to Dr. Sigeo Gamô, in honor of his great contribution to cumacean taxonomy.

Distribution. Pacific coast of southern Japan, off Kyushu and Nansei Islands, East China Sea, 608–2023 m, Sulu Sea, 514– 516 m.

Remarks. The present new species is similar to P. brevirostris in that the dorsal surface of the carapace of females has strong, sharp edged dorsolateral carina whose anterior portion is serrated, and a ridge near the hind margin, but is distinguishable from the latter species by (1) elongate carapace, with acute, long pseudorostrum, (2) ocular lobe triangular (rounded in P. brevirostris ), (3) carpus of pereopod 1 narrow, 2.01–2.16 times its width (1.48–1.65 in P. brevirostris ), 2.43–2.70 times dactylus (1.82–2.20 in P. brevirostris ) (4) dorsolateral ridge of adult male running along only anterior portion of carapace, (5) antenna 2 of adult male short, reaching middle portion of pleonite 3, and (6) outer ramus of pleopod 1 with two thick naked setae (arrow heads).

A single ovigerous female from the Sulu Sea agrees well with specimens from Japanese waters, but shows minor morphological variation including (1) teeth on dorso-lateral ridges very small, not easily observable, (2) dorsal crest of pereonite 4 serrated for posterior half, while specimens in Japan serrated for entire length.

Figures

FIGURE 10. Petalosarsia gamoi sp. nov., ovigerous female. A, lateral view; B, anterior portion of body, from above; C, antenna 1; D, antenna 2; E, labium; F, mandibles; G, maxilla 1; H, maxilla 2; I – K, maxillipeds 1 – 3; L, M, pereopods 1, 2.

FIGURE 11. Petalosarsia gamoi sp. nov., ovigerous female. A – C, pereopods 3 – 5; D, uropod with pleonite 6.

FIGURE 12. Petalosarsia gamoi sp. nov., adult male. A, lateral view; B, anterior portion of body, from above; C, antenna 1; D, antenna 2; E, maxilliped 3; F – J, pereopods 1 – 5; K, L, pleopods 1, 2; M, uropod with pleonite 6.