Petalosarsia ryukyuensis, 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 : 11-15

Petalosarsia ryukyuensis sp. nov.

( Figs. 7–9 )

Material examined. Holotype ovigerous female (NSMT-Cr 22075), 3.44 mm, allotype adult male (NSMT-Cr 22076), 3.96 mm, paratypes 1 ovigerous female and 1 juvenile, 3.17 mm and 2.65 mm (NSMT-Cr 22077), southeast of Kumejima Island, Okinawa Trough, East China Sea, 25°30.96ˏN, 126°29.21ˏE, 25°30.88ˏN, 126°29.21ˏE – 25°48.97ˏN, 126°29.55ˏE, 372–375 m (KH-05-1, St. OT-14), 15 May, 2005.

Description. Holotype ovigerous female ( Figs. 7 , 8 ). Body moderately calcified, surface of integument smooth. Carapace length 1.00 times width, length 1.59 times depth, length 0.26 times total body length ( Fig. 7 A); anterior portion of dorsal surface with dorsolateral carina with 3 teeth; transverse ridge near hind margin absent. Frontal margin of pseudorostral lobes, between foremost teeth of dorsolateral carina, 0.60 times greatest width of carapace ( Fig. 7 B); pseudorostrum short and truncate, 0.11 times carapace length; anterolateral angle and antennal notch obsolete. Width of rounded eye lobe 0.15 times width of carapace. Pereon 0.74 times carapace; side plates of pereonite 2 and 3 well developed. Pleon 0.55 times total body length ( Fig. 7 A).

Antenna 1 ( Fig. 7 C), 1st article of peduncle 1.58 times combined length of 2nd and 3rd articles; 2nd peduncular article widely open distally; distal end of 2nd article fringed with thin, broad collar exceeding joint with 3rd article; conical 3rd article small; main flagellum of 3 articles, 0.54 times basal article of peduncle, with 2 aesthetascs; accessory flagellum minute. Antenna 2 ( Fig. 7 D) of 2 articles, with a plumose seta on distal end of each article. Maxilliped 1 ( Fig. 7 H) with 1 branchial lobule; basal article with a short brush of setae. Maxilliped 2 ( Fig. 7 I) basis, 0.95 times combined length of ischium, merus, carpus and propodus, with a round plate on ventral surface, a short seta on inner margin and 4 spines near distal end. Maxilliped 3 ( Fig. 7 J) basis 0.87 times distal articles together, with 2 plumose setae on inner margin.

Pereopod 1 ( Fig. 7 K) basis 1.1 times combined length of ischium and carpus, with 5 plumose setae on inner margin; carpus 1.7 times its width, 2.2 times dactylus length, 0.83 times basis length. Pereopod 2 ( Fig. 8 A) basis 0.8 times distal articles together, with 2 plumose setae on inner margin; dactylus longer than carpus. Pereopod 3 ( Fig. 8 B) basis 2.2 times remaining distal articles, with 3 long and 7 short plumose setae; exopod absent. Pereopod 4 ( Fig. 8 C) basis 1.55 times remaining distal articles; exopod absent. Pereopod 5 ( Fig. 8 D) basis 0.8 times remaining distal articles.

Uropod ( Fig. 8 E), peduncle 1.31 times pleonite 6 length, 0.58 times exopod length, 0.45 times endopod length; exopod 0.78 times endopod. Endopod with 4 setae on inner margin and with 2 terminal setae. Telson semicircular, 0.49 times length of pleonite 6.

Allotype adult male ( Fig. 9 ). Carapace length 0.30 times total body length, length 1.27 times greatest width and 1.96 times depth ( Fig. 9 A, B); only anterior portion with lateral carina, with 4 teeth; hind margin of dorsal surface without ridge; frontal margin between lateral carina 0.72 times greatest width ( Fig. 9 B); pseudorostrum 0.078 times length of carapace. Width of eye lobe 0.16 times width of carapace. Pereon 0.55 times carapace ( Fig. 9 A). Pleon 0.53 times total body length, with 2 pairs of pleopods ( Fig. 9 A).

Antenna 1 ( Fig. 9 C) 1st article of peduncle 1.64 times combined length of 2nd and 3rd; main flagellum of 5 articles; 1st article with 10 aesthetascs; accessory flagellum of 3 articles, as long as proximal 3 articles of main flagellum combined. Antenna 2 ( Fig. 9 D) peduncle with 1 plumose seta; flagellum of 22 articles, exceeding posterior end of telson . Maxilliped 3 ( Fig. 9 E) basis 1.1 times remaining distal articles, with 5 plumose setae on inner margin. Basis of maxilliped 3 and pereopods 1–4 strongly constructed at proximal portion, with well developed exopods.

Pereopod 1( Fig. 9 F) basis 1.45 times combined length of ischium and carpus; length of carpus 1.6 times its width, 2.15 times dactylus length, 0.59 times basis length; distal margin much broader than proximal margin. Pereopod 2 ( Fig. 9 G) basis 1.1 times remaining distal articles, dactylus slightly longer than carpus. Pereopods 3, 4 ( Fig. 9 H, I) basis broad at base, 2.45 and 1.6 times length of remaining distal articles respectively. Pereopod 5 ( Fig. 9 J) slender, basis 0.8 times remaining distal articles, with 3 plumose setae. Pleopod 1 ( Fig. 9 K), outer and inner rami fused; outer ramus with 3 long plumose seta (2 of them stiff and almost naked) on ventral side and 1 thick, short naked seta (arrow head) on dorsal side; inner ramus with 5 plumose setae (1 of them stiff and almost naked); inner margin of peduncle with 7 plumose setae.

Uropod ( Fig. 9 M), peduncle 1.47 times pleonite 6 length, 0.57 times exopod length and 0.45 times endopod length; exopod 0.79 times endopod length; endopod with 7 or 8 spiniform setae on inner margin. Telson ( Fig. 9 M) reaching over anus, triangular shape, 0.70 times pleonite 6 length.

Etymology. The species name refers to the locality that the specimens were collected at, the Ryukyu Islands.

Distribution. Southeast of Kumejima Island, Okinawa Trough, 372– 375 m.

Remarks. The Shape of appendages of the present new species is similar to Petalosarsia brevirostris Gamô, 1986 , but can be distinguished from the latter by (1) carapace with lateral carina only on anterior portion, while all P. brevirostris specimens examined have sharp dorsolateral carina running for the entire length of the carapace ( Fig. 3 A-D), and (2) ridge near hind margin of dorsal surface of carapace obsolete in female and wholly absent in male, and (3) carpus of pereopod 1 in two ovigerous females long, 0.82–0.83 times basis (0.64–0.72 in P. brevirostris , 10 specimens, Fig. 3 F).

Figures

FIGURE 3. Petalosarsia brevirostris Gamô. Ovigerous female; A, habitus, lateral view; B anterior portion of body, dorsal view; E, maxilliped 2; F, pereopod 1. Adult male; C, habitus, lateral view; D, anterior portion of body, dorsal view; G, pleopod 1.

FIGURE 7. Petalosarsia ryukyuensis sp. nov., ovigerous female. A, lateral view; B, anterior portion of body, from above; C, antenna 1; D, antenna 2; E, mandibles; F, maxilla 1; G, maxilla 2; H – J, maxillipeds 1 – 3; K, pereopod 1.

FIGURE 8. Petalosarsia ryukyuensis sp. nov., ovigerous female. A – D, pereopods 2 – 5; E, uropod with pleonite 6.

FIGURE 9. Petalosarsia ryukyuensis 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, pleopod 1, 2; M, uropod with pleonite 6.