Pasiphaea gracilis Hayashi, 1999

Komai, Tomoyuki, Ohtsuka, Susumu, Yamaguchi, Shuhei & Nakaguchi, Kazumitsu, 2018, New records of six deep-sea caridean shrimps (Crustacea: Decapoda) from the Ryukyu Islands and its adjacent waters, southwestern Japan, Zootaxa 4457 (1), pp. 114-128: 122-125

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Pasiphaea gracilis Hayashi, 1999


Pasiphaea gracilis Hayashi, 1999 

[New Japanese name: Akahoshi-shira-ebi]

Figs. 7BView FIGURE 7, 9View FIGURE 9

Pasiphaea gracilis Hayashi, 1999: 290  , figs. 15–17 [type locality: New Caledonia, 850 m].— De Grave & Fransen 2011: 258.

Material examined. T/RV “Toyoshio-maru”, 2005-04 cruise, stn 7, NE of Tokashiki Island, Kerama Islands,

26°19.38’N, 127°26.78’E, 593– 532 m, 26 May 2005, beam trawl, 4 males (cl 9.4–10.9 mm), 1 female (cl 10.7 mm), CBM-ZC 11339; 2010-03 cruise, stn 8, N of Zamami Island , Kerama Group, 26°19.03’N, 127°28.07’EGoogleMaps  , 550–628 m, 23 May 2010, sledge, 2 ovigerous female (cl 10.6, 11.1 mm), CBM-ZC 11269; stn 13, W of Amamiohshima Island , 28°23.54’N, 129°11.25’EGoogleMaps  , 0–508 m, bottom depths 683–708 m, 21 May 2010, ORI net oblique tow, 4 females (cl 8.4–10.2 mm), CBM-ZC 11279.

Coloration in fresh condition ( Fig. 7BView FIGURE 7). Body generally semitransparent, with scattered red chromatophores; dorsal and ventral margins of pleomere 6, telson and uropods reddish. Basal halves of fingers of pereopods 1 and 2 also reddish.

Distribution. Previously known from the South-West Pacific Ocean, i.e., Chesterfield Islands, New Caledonia, Wallis and Futuna Islands, and Indonesia; at depths of 600–1300 m ( Hayashi 1999). The present specimens greatly extend the geographical range of the species to the north and west.

Remarks. Pasiphaea gracilis  was originally described on the basis of material from the South-West Pacific localities, including Chesterfield Islands, New Caledonia, Wallis and Futuna Islands, and Indonesia, and referred to the P. sivado  species group ( Hayashi 1999). There have been no subsequent records of the species. The specimens examined in this study are identified as P. gracilis  on account of the following features (cf. Hayashi 1999): rostrum moderately small and moderately ascending ( Fig. 9A, BView FIGURE 9); carapace dorsally rounded, with shallow but distinct branchiostegal sinus ( Fig. 9A, BView FIGURE 9); pleomeres all rounded dorsally, pleomere 6 with posterodorsal spine ( Fig. 9CView FIGURE 9); posterior margin of telson truncate; meri of pereopods 1 and 2 with 4–8 and 10–15 spiniform setae, respectively ( Fig. 9D, EView FIGURE 9), included within variation range previously reported; ischium of pereopod 2 without spiniform seta on ventral margin ( Fig. 9BView FIGURE 9); and no pleurobranch on thoracomere 8. Our specimens represent the second record of the species since the original description.

Pasiphaea japonica Omori, 1976  was the only member of the P. sivado  species group known from Japan prior to this study. It is readily distinguished from P. debitusae  and P. gracilis  by the possession of a small pleurobranch on the thoracomere 8 and the more numerous spiniform setae on the pereopod 2 merus (14–23 in number). Pasiphaea mclaughlinae Hayashi, 2006a  , recently described from Taiwan and referred to the P. sivado  species group, resembles P. gracilis  , but the former is characteristic within the species group in having dorsally flat tergites of the pleomeres 3–5 (Hayashi, 2006).

Specimens in one of the three lots (CBM-ZC 11279) were collected together with specimens of P. debitusae  (CBM-ZC 11278). The two species can be distinguished from each other by the shape of the rostrum (broader and more ascending in P. gracilis  than in P. debitusae  ), the development of the branchiostegal sinus of the carapace (clearly defined in P. gracilis  versus obsolescent in P. debitusae  ), the armature of the ischium of the pereopod 2 (unarmed in P. gracilis  versus armed with one spiniform seta in P. debitusae  ), as well as the different coloration in life: the scattered red chromatophores are distributed all over the pleon in P. gracilis  , while they are not present on the dorsal side in P. debitusae  .

From Japanese waters, the following seven species of Pasiphaea  have been reported ( Hayashi 2007; Komai & Komatsu, 2016): P. amplidens Spence Bate, 1888  , P. exillimanus Komai, Lin & Chan, 2012  , P. japonica  , P. oshoroae Komai & Amaoka, 1993  , P. sinensis Hayashi & Miyake, 1971  , P. sinrekoi Burukovsky, 1987  , and P. tarda Krøyer, 1845  . Of them the specific identity of specimens identified as P. tarda  needs to be reassessed ( Hayashi, 2006b). With the addition of P. debitusae  and P. gracilis  , nine species of Pasiphaea  are now known from Japan.














Pasiphaea gracilis Hayashi, 1999

Komai, Tomoyuki, Ohtsuka, Susumu, Yamaguchi, Shuhei & Nakaguchi, Kazumitsu 2018

Pasiphaea gracilis

Hayashi, 1999 : 290
De Grave & Fransen 2011 : 258