Parametaphoxus asiaensis ( Hirayama, 1992 )

Shin, Myung-Hwa, Wongkamhaeng, Koraon & Kim, Won, 2016, A new record of Parametaphoxus asiaensis (Hirayama, 1992) (Crustacea: Amphipoda: Phoxocephalidae) from Korea, Journal of Species Research 5 (3), pp. 533-538 : 534-537

Parametaphoxus asiaensis ( Hirayama, 1992) ( Figs. 1-3 )

Metaphoxus fultoni : Hirayama, 1987, 58, figs. 260-263.

Metaphoxus fultoni asiaensis Hirayama, 1992 , 127, figs. 10-14; Lowry, 2000, 323; Ren, 2012, 378, fig. 164.

Parametaphoxus asiaensis Jarrett and Bousfield, 1994 , 122.

Material examined. 1$, Jongdal­ri , Gujwa­eup , Jeju­si, Jeju Island, Korea, 1 Aug 2004 ; 1$, Biyang­ri , Hanlim­eup , Jeju­si, Jeju Island, Korea, 14 Sep 2007 ; 1$ (NIBRIV0000681436), Dangjin , Chungcheongnam­do, Korea, 16 Oct 2007 .

Description. Female: Body ( Fig. 1A ) small, 3.24 mm long, smooth.

Head ( Fig. 1B ) about 15 percent of total body length, rostrum curved slightly downwards, un­constricted, extending beyond peduncular article 2 of antenna 1. Eyes rounded.

Antenna 1 ( Fig. 1C ) peduncular article 1 stout, about 1.7 times as long as article 2; flagellum 4­articulate, about 1.1 times as long as peduncular article 1; accessory flagellum 3-articulate. Antenna 2 ( Fig. 1D ) peduncular article 4 longer than broad, posterior margin short; peduncular article 5 shorter than article 4; flagellum 3­articulate.

Left mandible ( Fig. 1F ), incisor with 4 humps; lacinia mobilis with 6 teeth; raker low with 3 finely pectinate spines; molar process small and non­triturative. Right mandible ( Fig. 1G ), incisor with 3 teeth; lacinia mobilis flabellate, denticulate; raker low with 2 spines. Mandibular palp ( Fig. 1H ) 3­articulate; palp article 2 slightly longer than article 3, with 1 mediodistal seta; palp article 3 with 8 apical setae.

Upper lip ( Fig. 1E ) broad, rounded apically. Lower lip ( Fig. 1I ) mandibular process weak, apically rounded.

Maxilla 1 ( Fig. 1J ) inner plate broad, ovate, without seta; outer plate with 1 trifid, 2 bifid, and 4 serrate spines; palp uniarticulate, bearing 3 apical setae. Maxilla 2 ( Fig. 1K ) inner plate much shorter than outer, with facial oblique row of 3 setae; outer plate with 3 apical setae.

Maxilliped ( Fig. 1L ) inner plate with 2 apical setae; outer plate having 2 short teeth and 2 mid­length setae on apical margin, with 1 marginal seta. Maxillipedal palp ( Fig. 1M ) articles 2­3 with short and long setae; nail of article 4 long, stout.

Gnathopod 1 ( Fig. 2A ) coxa subrectangular, with 5 unequal simple setae on posterior half of ventral margin; basis longest, posterior margin with 2 long setae, anterodistal margin with 1 short seta; ischium short with 1 posterodistal seta; merus about 0.6 times carpus, meeting middle expansion of carpus, with 1 short posterodistal seta; carpus growing at proximal part of merus, with 1 setae; propodus subrectangular, bearing1 spine and 1 tooth posterodistally; palm parachelate weakly, with setae; dactylus falcate, reaching inner side of posterodistal tooth.

Gnathopod 2 ( Fig. 2B ) subchelate; coxa subrectangular, with 3 unequal simple setae on posterior half of ventral margin; basis posterior margin with 3 long setae; ischium short, with 1 short posterodistal seta; merus as long as carpus, posterodistal lobe acute with 1 seta; carpus with 1 midposterior seta; propodus longer than broad, palm transverse, defined by strong corner tooth with 1 spine.

Pereopod 3 ( Fig. 2C ) coxa subrectangular, ventral margin with 5 posterior submarginal setae; basis 2.2 times propodus; merus 1.8 times propodus; carpus bearing 2 unequal spines on posterior margin; propodus narrow, with 1 pair of locking spines. Pereopod 4 ( Fig. 2D ) coxa posterior margin deeply excavated; carpus bearing 2 unequal spines on posterior margin; propodus narrow, with 1 pair of locking spines; dactylus slender.

Pereopod 5 ( Fig. 2E ) relatively short, coxa bilobed, posterior lobe expanded; basis longer than broad, anterior margin with several setae, bearing developed posterodistal lobe; carpus about 2 times as long as ischium; propodus and carpus subequal in length; dactylus slen­ der, exceeding half of propodus.

Pereopod 6 ( Fig. 2F ) coxa bilobed, anterior lobe shallow; basis anterior margin strongly convex, with numerous bunches of long simple and plumose setae, posterodistal lobe well developed, over reaching distal end of ischium; merus slightly longer than carpus; carpus and propodus subequal in length; propodus slender; dactylus about half length of propodus.

Pereopod 7 ( Fig. 2G ) shorter than pereopod 6. Coxa weakly bilobed; basis prominently expanded backward, extending beyond end of carpus, slightly rounded ventrally, with 1 anterodistal spine, posterior margin finely crenulate; merus longer than carpus; carpus slightly shorter than propodus; propodus shorter than merus; dactylus 0.7 times propodus.

Epimeral plates 1­3 ( Fig. 3A ) rounded posterodistally; epimeral plate 2 bearing 1 facial plumose seta.

Uropod 1 ( Fig. 3B ) peduncle longer than rami, with 2 dorsolateral and 2 dorsomedial spines; rami subequal in length; outer ramus having 1 dorsolateral spine; inner ramus smooth, unarmed.

Uropod 2 ( Fig. 3C ) peduncle subequal to rami, with 2 dorsolateral and 1 dorsomedial spines; outer ramus slightly longer than inner ramus, bearing 1 dorsolateral spine; inner ramus smooth, unarmed.

Uropod 3 ( Fig. 3D ) peduncle about 0.6 times outer ramus, longer than inner ramus, with 2 laterodistal and 1 mediodistal spines; outer ramus biarticulate, proximal article about 1.5 times inner ramus, with 3 spines on distal corner, and distal article bearing 3 apical setae; inner ramus 0.7 times as long as first article of outer ramus, with 1 apical seta.

Telson ( Fig. 3E ) deeply cleft, each lobe rather slender, bearing 1 spine and 1 plumose seta, apically, and 1 pair of plumose setae, middorally.

Male: No males were identified in the current study.

Distribution. Korea (current study), Hong Kong, China, and Japan.

Remarks. In 1992, Hirayama described a new subspecies Metaphoxus fultoni asiaensis , in Hong Kong which was discriminated from M. fultoni fultoni (Scott, 1890) and M. fultoni tulearensis ( Barnard and Drummond, 1978) . According to Hirayama’s discussion, M. fultoni asiaensis has a pair of locking spines on the propodi of pereopods 3­4, same as that of M. fultoni tulearensis . In gnathopod 1 of M. fultoni asiaensis , however, the palm is almost transverse and the propodus is less prolonged than those of two subspecies, M. fultoni fultoni and M. fultoni tulearensis ( Hirayama, 1992) . Thereafter, Jarrett and Bousfield (1994) transferred M. fultoni asiaensis to the genus Parametaphoxus , and elevated the subspecies into species status. In this study, we followed the classifica­ tion scheme of Jarrett and Bousfield (1994).

Parametaphoxus asiaensis is similar to P. quaylei Jarrett and Bousfield, 1994 . However, it differs from latter species. In P. quaylei , the third article of mandibular palp has more distal setae than that of P. asiaensis . In P. quaylei , the proximal article of uropod 3 outer ramus has a marginal spine, whereas no spine is evident in P. asiaensis . In addition, the telson of P. quaylei bears two long apical spines, whereas there is a single short spine in P. asiaensis .

The characteristics of our specimens coincided with those shown in Hirayama’s original description. However, two minor differences were observed between our materials and the illustration of Hirayama’s female. In our specimen, the outer ramus of uropod 2 bears a marginal spine, and the epimeral plate 2 bears a single plumose seta on the ventral surface. However, there was no evident seta and spine in those of the Hirayama’s illustration. These variations might be a result of the developmental stages of the individuals examined, because the body length of our material was 3.24 mm, and that of Hirayama’s illustration was 2.3 mm.

Figures

Fig. 1. Parametaphoxus asiaensis(Hirayama, 1992), female.A, body; B, head; C, antenna 1; D, antenna 2; E, upper lip; F, left mandible; G, right mandible; H, mandibular palp; I, lower lip; J, maxilla 1; K, maxilla 2; L, maxilliped; M, maxillipedal palp. Scales: A, 0.5 mm; B, 0.2 mm; C, D, 0.1 mm; E, H, I, M, 0.05mm; F, G, J­L, 0.03mm.

Fig. 2. Parametaphoxus asiaensis(Hirayama, 1992), female.A, gnathopod 1; B, gnathopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6; G, pereopod 7. Scales: B­G, 0.2 mm; A, 0.1 mm.

Fig. 3.Parametaphoxus asiaensis(Hirayama, 1992), female.A, pleonites 1­3; B, uropod 1; C, uropod 2; D, uropod 3; E, telson. Scales:A, 0.2 mm; B, 0.1 mm; C­E, 0.05mm.