Paramphilochus parachelatus Ishimaru & Ikehara, 1986

Lee, Kyung-Sook, 2010, A new species and new record of the Amphilochidae (Crustacea: Amphipoda) from Korea, Zootaxa 2477, pp. 21-36 : 31-35

Paramphilochus parachelatus Ishimaru & Ikehara, 1986 ( Figures 6–8 ) (Korean Name: Nae-min-son-jjal-eun-kko-ri-yeop-sae-u, new)

Paramphilochus parachelatus Ishimaru & Ikehara, 1986 , p. 193, figs. 1–3; Ishimaru, 1990, p. 212, fig. 3.

Material examined. 4 specimens, Daejung Jejudo Is., 13 August 2003, algal wash, collector Y.H. Kim; 11 specimens, Daebo, Pohang-si, 26 August 2005, algal wash, collector Y.H. Kim; 3 ♀, Gajin, Goseong-gun, 20 October 2005, light trap, collector Y.H. Kim; 1 specimen, Dapo Port., Geojedo Is., 13 June 2008, light trap, collector Y.H. Kim; 3 specimens, Buheung-ri, Yeougdeok-gun, 20 June 2008, light trap, collector Y.H. Kim; 1 specimen, Jijuk Port, Goheung-gun, 25 June 2008, light trap, collector Y.H. Kim; 7 specimens, Sacheon, Gangreung-si, 11 July 2008, algal wash, collector S.S. Hong; 5 specimens, Jungrajin Port, Samcheok-si, 9 August 2008, algal and invertebrate wash, collector K.S. Lee; 1 specimen, Gonghyeonjin Port, Goseong-gun, 13 March 2009, algal and invertebrate wash, collector Y.H. Kim; 3 specimens, Seodo-ri, Geomundo Is., 16 April 2009, light trap, collector Y.H. Kim.

Description. ♀. Body ( Figs. 6 , 7A ) dorsally smooth, 3.3 mm long.

Head ( Fig. 7A ) slightly longer than pereonite 1; eye elliptical, medium to large size, with core of black pigment in alcohol; rostrum well developed, reaching distal end of peduncular article 1.

Antenna 1 ( Fig. 7B ) length ratio of peduncular articles 1–3 = 1.00: 1.00: 0.60, article 1 slightly wider than article 2; article 3 bearing coniform, 1-articulate accessory flagellum, 0.33 x length of flagellum article 1, with 2 unequal setae and tiny penicillate seta distally; primary flagellum 8-articulate, 0.91 x length of peduncular articles, each article with 1 or 2 long aesthetascs, respectively.

Antenna 2 ( Fig. 7C ) subequal in length to antenna 1; peduncular articles 1 and 2 short, article 4 subequal in length to article 5; flagellum 9-articulate, slightly shorter than peduncular articles.

Gnathopod 1 ( Fig. 7D ) coxa ovate, mostly hidden by coxa 2; basis rectangular; ischium 0.66 x length of merus; carpal lobe extending about 0.5 x along ventral margin of propodus, narrowly triangular, medially and distally with 3 setae; propodus about 0.7 x as wide as long, 4.1 x length of carpus, palm nearly transverse, convex, finely serrulate, with a row of feeble setae, palm corner defined by a pair of distal spines; dactylus about 0.6 x as long as propodus, nearly reaching palm corner, with a small inner marginal tooth subdistally. Gnathopod 2 ( Fig. 7E ) similar to gnathopod 1, but carpus and propodus of a different shape; coxa 2 subrectangular, ventral margin rounded; carpus very short, length 0.22 x propodus, carpal lobe very small, not guarding ventral margin of propodus; propodus parachelate, gradually widening distally, palm jutting obtusely forward; palm transverse, corner defined by a pair of distal spines; dactylus fitting palm, with a small tooth subdistally.

Pereopod 3 ( Fig. 7F ) coxa similar to coxa 2, with setules ventrally; basis rectangular, bearing feeble setae on anterior margin and 1 seta posterodistally; merus 1.37 x length of carpus, anterodistal corner protruding; posterior margins of merus to propodus with sparse clusters of setae; dactylus 0.38 x length of propodus, inner margin with distal tooth.

Pereopod 4 ( Fig. 7G ) similar to pereopod 3 except coxa broadened, posterior margin excavate.

Pereopod 5 ( Fig. 8A ) coxa broad, posterolobate, anterior margin broadly convex, posterior lobe narrowed; basis broadly rounded, expanded posteriorly, anterior margin with 2 rows of short spines, posterior margin with minute setules, posterodistal corner rounded; ischium 0.47 x length of merus, with 2 spines anteriorly; merus 1.14 x length of carpus, posterodistal corner overhanging; propodus as long as merus, longer than carpus, with row of anterior spines, with feeble posterior marginal setae.

Pereopod 6 ( Fig. 8B ) similar to pereopod 5, but the anterior margin of coxa 6 is straight, articles are slightly wider and propodus is longer.

Pereopod 7 ( Fig. 8C ) coxa small, ventral margin rounded; basis slightly broader than those of pereopods 5–6; articles 5–7 missing.

Epimeron 1 ( Fig. 8D ) subtriangular, posteroventral corner with small cusp.

Epimeron 2 ( Fig. 8D ) subrectangular, ventral margin with 4 spines; posteroventral corner with small cusp.

Epimeron 3 ( Fig. 8D ) subrectangular, ventral margin with 2 spines, posteroventral corner with small cusp.

Uropod 1 ( Fig. 8E ) peduncle longer than rami, 1.22 x length of inner ramus, with 11 dorsolateral, 2 dorsomedial and 1 apicomedial spine; outer ramus 0.86 x length of inner ramus, with 3 dorsolateral marginal spines; inner ramus with 3 dorsolateral and 3 dorsomedial spines.

Uropod 2 ( Fig. 8F ) peduncle short, 1.2 x length of outer ramus, with 5 dorsolateral and 1 apicomedial spines; outer ramus short, 0.71 x length of inner ramus, with 3 dorsolateral spines; inner ramus with 3 dorsolateral and 2 dorsomedial spines.

Uropod 3 missing.

Telson ( Fig. 8G ) linguiform, triangular, 1.65 x as long as wide, apically broadly rounded, with 2 pairs of penicillate setae on middorsal surface.

Remarks. In general, our specimens show many morphological similarities to the original description and figures of Ishimaru & Ikehara (1986). However, our specimens also display some important differences, such as the shorter carpal lobe of gnathopod 1, gnathopod 2 propodus broader, epimeron 1–3 bearing weakly toothed posteroventral corners (vs not toothed), uropod 2 outer ramus longer and the telson rounded apically (vs acutely pointed). However, as we have not had the opportunity to examine the type material of Ishimaru & Ikehara (1986), we cannot confidently determine whether our species is novel. Therefore at this time we conservatively maintain our Korean specimens as P. parachelatus until a detailed, comparative study can be made on the type material.

Distribution. Korea (Jejudo Island, south and east coasts), Japan.

Figures

FIGURE 6. Paramphilochus parachelatus, female, 3.3 mm, Daebo, Pohang-si, Korea.

FIGURE 7. Paramphilochus parachelatus Ishimaru & Ikehara, 1986, female, 3.3 mm, Daebo, Pohang-si, Korea: A, habitus, lateral; B, antenna 1; C, antenna 2; D, gnathopod 1; E, gnathopod 2; F, pereopod 3; G, pereopod 4. Scale bars = 0.4 mm (A), 0.1 mm (B – G).

FIGURE 8. Paramphilochus parachelatus Ishimaru & Ikehara, 1986, female, 3.3 mm, Daebo, Pohang-si, Korea: A, pereopod 5, B, pereopod 6; C, pereopod 7; D, pleonites 1 – 3; E, uropod 1; F, uropod 2; G, telson. Scale bars = 0.2 mm (D), 0.1 mm (A – C, E, F), 0.05 mm (G).