Pagurixus fasciatus Komai & Myorin 2005
Creators: name: Osawa, Masayuki
name: Kawai, Takashi
name: Sakamaki, Takashi
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Paguridae
Pagurixus
Pagurixus fasciatus

description: Pagurixus fasciatus Komai & Myorin, 2005   
(Figs 1C, D, 3B–E)  
[Japanese name: Kashiwajima-himehonyadokari]  
 Pagurixus fasciatus Komai & Myorin, 2005: 2, figs 1–4 [type locality: Kashiwa-jima, Otsuki, Kochi Prefecture, southern Japan, 10–15 m].—Okuno et al. 2006: 156, plate 3E, F.— Okuno & Arima 2006: 36.— Komai 2010: 1287.— McLaughlin et al. 2010: 31 (list).   
 Material examined. Tanega-shima, Osumi Group: stn Kurosenohana 3, 30°40.4´N, 131°03.8´E, 7 m, 13–14 Aug. 2012, coll. T. Kawai, 1 male (sl 0.9 mm), RUMF-ZC 2329; stn Nishino-omote 1, 30°44.6´N, 130°59.4´E, 7 m, 3– 7 Aug. 2012, coll. T. Kawai, 1 male parasitized by peltogastrid rhizocephalan (sl 1.2 mm), RUMF-ZC 2330; stn Sumiyoshi 2, 30°40.0´N, 130°56.3´E, 7 m, 4–8 Aug. 2012, coll. T. Kawai, 1 male (sl 1.7 mm), 1 female (sl 1.4 mm), RUMF-ZC 2331; stn Sumiyoshi 3, 30°41.9´N, 130°57.6´E, 7 m, 4–8 Aug. 2012, coll. T. Kawai, 1 male (sl 1.5 mm), RUMF-ZC 2332. Yaku-shima, Osumi Group: stn Kurio 1-1, 30°13.9´N, 130°28.2´E, 7 m, 10 Aug. 2012, coll. T. Kawai, 1 male (sl 1.1 mm), 1 female (sl 1.1 mm), RUMF-ZC 2333.   
 Coloration in life. The coloration of the present specimens agrees well with that of P. fasciatus described by Komai & Myorin (2005: fig. 1). See Fig. 1C, D.   
 Distribution. Previously known only from Kashiwa-jima (Kochi Prefecture), Izu Peninsula, and Izu and Ogasawara Islands, Japan; intertidal to 30 m (Komai 2010). Now also recorded from Tanega-shima and Yakushima, Osumi Group in the northern Ryukyu Islands; 7 m.   
 Habitat. Rocky reefs, on interspaces of rocks with algae and/or corals.   
 Remarks. The present specimens generally agree well with the original description of P. fasciatus by Komai & Myorin (2005) in both morphology and coloration. Nevertheless, they have variations in the armature on the carpi of the second pereopods. Komai & Myorin (2005) described and illustrated P. fasciatus to have the carpi of the second pereopods unarmed on the dorsal margin, except for a dorsodistal spine. However, in the males of the present Ryukyu material, the dorsal margin of each carpus is slightly protuberant and either unarmed or armed with a tiny spine proximal to the midlength (Fig. 3B, C), this spine is more pronounced in the smallest specimen (sl 0.9 mm, RUMF-ZC 2329); whereas in the females, the dorsal margin always bears a small spine (Fig. 3D, E).   
 At our request, Dr. T. Komai kindly re-examined the holotype and three paratypes of P. fasciatus and two specimens of that species reported by Komai (2010). The holotype male (CBM-ZC 7980 in the collection of the Natural History Museum and Institute, Chiba) has a small dorsal spine on the carpus of the right second pereopod, which is visible only in the mesial view, but such a spine is absent on the left side. In three paratypes (CBM-ZC 7981), the spine is absent or reduced to a minute protuberance in two males, while it is distinct in one female. Two male specimens from the Ogasawara Islands (CBM-ZC 9646 and 9650) lack a dorsal spine on the carpus of each second pereopod. Thus, the armature on the carpus appears to vary in the previous reported material as in the present material from the Ryukyu Islands, and the dorsal spine tends to be reduced in males.   
In addition to the variation of the armature on the carpi of the second pereopods, a male specimen from Tanega-shima (RUMF-ZC 2332) has a small submedian spine on the dorsal margin of the carpus of the right third pereopod. Such a spine is absent on the carpus of the left third pereopod in the same specimen and on the carpi of both third pereopods in all other specimens. In all the specimens examined, the ventorolateral margin of the merus of the right cheliped has a row of small but distinct spines, although the margin was described as smooth or finely denticulate in the type specimens (Komai & Myorin 2005). The fourth pereopods are subequal in size on right and left and in both males and females; the setation is similar on right and left in males, but in females, setae on the mesial surfaces of the dactylus, propodus, carpus, and merus are longer and more pronounced on the left side than on the right side.
description: Published as part of Osawa, Masayuki, Kawai, Takashi & Sakamaki, Takashi, 2013, New records of Pagurixus Melin, 1939 (Crustacea: Decapoda: Paguridae) from the Ryukyu Islands, southwestern Japan, with description of a new species, pp. 350-366 in Zootaxa 3669 (3) on pages 353-355, DOI: 10.11646/zootaxa.3669.3.9, http://zenodo.org/record/5266714