Two new species of pontogeneiid amphipods (Crustacea, Senticaudata, Calliopioidea) from Korean waters

Abstract Two new pontogeneiid amphipods, Eusiroides pilopalpus sp. n. and Paramoera dentipleurae sp. n., from Korean waters are described and illustrated. Eusiroides pilopalpus sp. n. can be distinguished from congeners by the following characters: mandibular palp article 3 has brush-like setation, maxilla 2 has an inner plate that is not enlarged, and gnathopods 1 and 2 ischium has a well-developed anterior lobe. Paramoera dentipleurae sp. n. can be discriminated from congeners by the following characters: head anterior cephalic lobe is sinusoid, pereopods 5–7 are homopodous and slender, pereopods 6 and 7 basis are proximally lobed but distally diminished on posterior margins, and epimeron 3 is prominently expanded posterodistally.


Materials and methods
Samples were collected from the benthic zones using a sledge net (mesh size 300 µm, mouth size 120 × 45 cm). Specimens were initially fixed with 5% formaldehyde-seawater solution. They were preserved with 85% ethyl alcohol after sorting in the laboratory. Samples were stained with lignin pink dyes. Specimen appendages were dissected in a Petri dish filled with glycerol using dissection forceps and a needle under a stereomicroscope (SZH10; Olympus, Tokyo, Japan). They were mounted onto temporary slides using glycerol-ethanol solution or permanent slides using polyvinyl lactophenol solution. Drawings were performed under a light microscope (LABOPHOT-2; Nikon, Tokyo) with aid of a drawing tube. Definition of the term for 'seta' and its types follows those of Watling (1989). Type material was deposited in the National Institute of Biological Resources (NIBR), Incheon, Korea. Etymology. The composite epithet of the specific name of pilopalpus is a combination of Latin pilosus and palpus meaning 'hairy palp'. This name refers to the character of the mandibular palp article 3: the surface is covered with several rows of minute setae along the distal two-thirds length and with a group of brush-like fine setae at the center of the outer margin. Noun in apposition.
Description of holotype female. Head (Fig. 1A): rostrum short; lateral cephalic lobes weakly produced and slightly oblique; antennal sinus not deep; eyes reniform, well-developed, enlarged.  Antenna 1 (Fig. 1B, C): stout, with length ratio of 1.0:0.7:0.3 in peduncular articles 1-3; peduncular article 1 with 1 group of 7 plumose setae on anterior margin proximally and with smooth groove bearing setae on lateral margin subdistally; peduncular article 2 with 1 subdistal and 2 distal setae laterally and 1 pair of distal setae medially on anterior margin, also with small groove bearing setae on distal margin; accessory flagellum uni-articulate, as long as 1 st proximal article of flagellum, with 5 setae on apex; flagellum more than 72-articulate and slightly longer than twice as long as peduncular articles 1-3 combined, proximal article longest, with single or paired aesthetascs and calceoli present from 1 st to 54 th articles discontinuously.
Maxilla 2 (Fig. 1K): inner plate ovoid, broader than outer plate, with 1 row of 8 weakly plumose and 1 long plumose setae on medial margin subdistally, covered with fine setae on apical and subapical margins; outer plate with 16 setae on apical margin, with 2 setae on lateral margin distally.
Maxilliped ( Fig. 2A): inner plate short, tongue-shaped, with 3 robust setae apically, with 8 bifid and 2 simple setae arranged from apex to mediodistal margin; outer plate elongate, 2.0 times as long as inner plate, lined with numerous long setae arranged from apex to medial margin, with 3 long weakly plumose setae on lateral margin; palp with expanded articles 1-3; article 1 with 1 group of 4 elongate setae laterodistally; article 2 lined with numerous simple long setae on medial margin, with 2 rows of setae subdistally, with 1 group of 6 unequal setae at laterodistal corner; article 3 0.3 times as long as article 2, with ledge bearing 1 row of long setae on surface, with 7 serrate and 4 simple setae at laterodistal corner, covered with numerous fine setae laterodistally; article 4 falcate, slightly shorter than article 3, with 4 setae along inner margin.
Gnathopod 1 (Fig. 2B, C): moderately subchelate; coxa expanded anterodistally, with 16 minute setae on round ventral margin, with 1 small notch bearing 1 minute seta posteroventrally, with 1 oblique row of 5 long setae on surface posteroventrally; basis lined with short setae and shallowly lobed anterodistally, with 2 groups of 3 submarginal setae proximally and with 2 groups of 9 subdistal and 3 distal setae medially on anterior margin, with 1 pair of elongate setae on posterior margin proximally and with 1 group of 6 setae at posterodistal corner; ischium largely lobed anteriorly, without setae on posterior margin and with 1 group of 11 setae posterodistally; merus forming groove anterodistally, with 1 row of 4 setae medially, with acute protrusion posterodistally, lined with numerous setae on posterior margin; carpus longer than merus, without setae on anterior margin and with 1 row of 5 setae at anterodistal corner, posterior margin broadly lobed laterally, weakly crenulate and with groups of serrate and simple setae and with 3 setae mediodistally; propodus ovoid, shorter than basis, with 1 group of 3 setae and 6 single setae on anterior margin and with 1 group of 9 setae at anterodistal corner, with 1 vertical row of 4 robust defining setae on medial surface near posterior margin, palm approximately 3.0 times as long as posterior margin and minutely pectinate, with 7 robust setae along toothed submargin; dactylus falcate, stout, long, fitting palm.
Gnathopod 2 (Fig. 2E, D): moderately subchelate, similar to gnathopod 1; coxa rectangular, not expanded anterodistally, with 1 oblique row of 4 elongate setae on surface posteroventrally, with 1 robust seta on posterior margin, ventral margin subrounded with 7 minute setae, coxal gill longer than coxa and expanded distally; basis shallowly lobed and lined with 8 setae anterodistally, with 1 group of 5 setae mediodistally on anterior margin, with 2 elongate setae proximally and lined with single or paired minute setae on posterior margin, with 1 group of 7 setae at posterodistal corner; ischium largely lobed and slightly dilated anterodistally, without setae on posterior margin and with 1 pair of subdistal and 1 group of 7 distal setae at posterodistal corner; merus forming groove anterodistally, with 1 row of 13 setae medially, with acute protrusion posterodistally; carpus longer than merus, with 2 setae on anterior margin and 1 group of 4 setae at anterodistal corner, posterior margin broadly lobed, weakly crenulate and with groups of simple setae; propodus triangular, shorter than basis, with 3 single and 2 pairs of setae on anterior margin and with 1 group of 8 setae at anterodistal corner, with 1 vertical row of 3 robust defining setae on medial surface near posterior margin, palm poorly defined, about 3.0 times as long as posterior margin and minutely pectinate, with 7 robust setae along toothed submargin; dactylus falcate, stout, long, fitting palm.
Pereopod 3 (Fig. 3A, B): coxa rectangular, similar to that of gnathopod 2, facial setae absent, with 7 minute setae on ventral margin, with 1 robust seta on posterior margin, coxal gill as long as coxa and expanded distally; basis slightly curved proximally, anterior margin lined with setae, anterodistal lobe weak with several setae, with more than 10 groups of minute setae on posterior margin; ischium short, anterodistally lobed, with 1 group of 3 setae at posterodistal corner; merus 0.7 times as long as basis, expanded anterodistally, with 3 proximal and 2 distal setae on anterior margin,  anterodistal corner produced with 1 group of 1 robust and 6 simple setae, with 3 groups of simple setae on posterior margin; carpus not expanded, 0.9 times as long as merus, with 2 setae on anterior margin and with 7 setae on anterodistal corner, with 3 pairs of 1 robust and 1 simple setae on posterior margin, posterodistal corner oblique with 4 lateral and 3 medial setae; propodus 1.1 times as long as carpus, with 5 pairs of setae on anterior margin and with 1 group of 5 setae at anterodistal corner, with 7 groups of robust and simple setae on posterior margin and with 1 group of 1 locking seta and 4 simple setae at posterodistal corner; dactylus falcate, as long as half of propodus.
Pereopod 5 ( Fig. 4A-C): coxa bilobed, posterior lobe narrower and more ventrally produced than anterior lobe, with 5 minute setae on ventral margin, coxal gill subovoid, smaller than that of pereopod 4; basis ovoid, with 3 elongate setae proximally and lined with 3 single setae and 5 groups of setae on anterior margin, anterodistal corner bluntly lobed with 1 group of 5 setae, posterior margin expanded and with 22 weak serrations bearing 1 minute seta, with 3 setae mediodistally, with 7 setae on medial surface proximally; ischium short, anterodistal corner weakly lobed downwards with 1 group of 6 setae, posterior margin largely expanded and slightly lurched posterodistally on lateral border; merus shorter than basis, with 4 groups of robust and simple setae on anterior margin and with 1 group of 5 robust setae at anterodistal corner, posterior margin expanded with 5 groups of robust and simple setae, posterodistal corner produced with 4 robust setae; propodus 1.4 times as long as merus, with 6 groups of paired setae on anterior margin, with paired locking setae and 3 simple setae at anterodistal corner, posterior margin irregularly setose with robust and simple setae, with 6 short setae at posterodistal corner; dactylus falcate, 0.3 times as long as propodus.
Pereopod 6 ( Fig. 4D, E): coxa bilobed, smaller than that of pereopod 5, anterior lobe small, posterior lobe expanded backwards and with 1 notch bearing 1 minute seta posteroventrally, coxal gill circular and slightly smaller than that of pereopod 5; basis ovoid, larger than that of pereopod 5, with 2 minute setae proximally and 7 groups of robust and simple setae on anterior margin, anterodistal corner bluntly lobed with 1 group of paired robust setae and 3 simple setae, posterior margin expanded with 25 weak serrations bearing 1 minute seta, with 23 setae proximally and 5 setae distally on medial border, with 8 setae on medial surface proximally; ischium short, anterodistal corner weakly lobed downwards with 1 group of 1 robust and 5 simple setae, posterior margin largely expanded and slightly lurched posterodistally on lateral border; merus shorter than basis, with 1 robust seta and 3 groups of robust and simple setae on anterior margin, with 1 group of 4 robust setae at anterodistal corner, posterior margin expanded with 2 setae and 3 pairs of robust and simple setae, posterodistal corner produced with 5 robust setae; carpus not linear, slightly shorter than merus, with 3 groups of robust and simple setae on anterior margin and with 1 group of 8 robust setae at anterodistal corner, posterior margin broadly expanded with 3 groups of simple setae, posterodistal corner weakly produced with 1 group of 7 robust setae; propodus 1.3 times as long as merus, with 6 groups of paired robust and simple setae on anterior margin, with paired locking setae and 7 simple setae at anterodistal corner, posterior margin setose irregularly with robust and simple setae, with 8 setae at posterodistal corner; dactylus falcate, 0.5 times as long as propodus.
Pleonal epimera (Fig. 6E): epimeron 1 with 1 oblique ledge on surface, with 1 group of 2 robust and 2 simple setae on ventral margin anteriorly, with 3 pairs of robust and simple setae and 1 robust seta submarginally, weakly produced at posteroventral corner; epimeron 2 larger than epimeron 1, also with 1 oblique ledge on surface, convex ventrally and with 4 pairs of robust and simple setae and 1 robust seta submarginally on anterior half of ventral margin, weakly produced at posteroventral corner; epimeron 3 largest, flattened ventrally, with 3 single setae and 1 pair of robust and simple setae on anterior half of ventral margin, posterior margin expanded backwards and with 11 serrations bearing 1 minute seta on distal half.
Male. Unknown. Remarks. Eusiroides pilopalpus sp. n. is very similar to E. japonica Hirayama, 1985. It can be readily distinguished from E. japonica by the following characteristic features: (1) degree of setation of peduncular articles 4 and 5 on antenna 2 is weaker than that of E. japonica; (2) anterior and posterior margins of peduncular article 5 on antenna 2 are parallel in E. pilopalpus sp. n. (vs. margins are gradually diminish distally, and  anterodistal and posterodistal corners are produced in E. japonica); (3) mandibular palp article 3 has a group of brush-like setae on the lateral surface (vs. several rows of minute setae in E. japonica); (4) expanded medial lobe of mandibular palp article 2 is not swollen in E. pilopalpus sp. n. (vs. swollen medially in E. japonica); (5) inner plate on maxilla 2 is not enlarged in E. pilopalpus sp. n. (vs. distinctly enlarged in E. japonica); (6) maxillipedal palp article 3 is covered with fine setae on its distal surface (vs. transverse rows in E. japonica); (7) anterior lobe of ischium on gnathopods 1 and 2 is well-developed in E. pilopalpus sp. n. (vs. moderately developed in E. japonica), (8) acute protrusion at the posterodistal corner of merus on gnathopods 1 and 2 is larger than that of E. japonica; (9) length of the dactylus on gnathopods 1 and 2 is longer than that of E. japonica; (10) posterior lobe of ischium on pereopods 5-7 is acutely produced distally; (11) merus, carpus, and propodus on pereopods 5-7 are more slender than those of E. japonica; (12) both pleonal epimera 1 and 2 have oblique ridges on their lateral surfaces (vs. the ridges are not present in E. japonica) and posterior margin of pleonal epimeron 3 has 11 serrations (vs. seven in E. japonica); (13) the outer ramus on uropod 2 has three dorsal setae medially (vs. dorsal setae are absent in E. japonica); and (14) the distal fourth of the telson is cleft in E. pilopalpus sp. n., (vs. cleft beyond the distal half in E. japonica) (Hirayama 1985).
Eusiroides pilopalpus sp. n. shares several characters with Eusiroides diplonyx Walker, 1909. However, E. diplonyx can be easily discriminated from its congeners because it has stout and round-ended locking setae on pereopods 3 and 4 (Walker 1909;Pirlot 1936;Barnard JL 1970;Myers 1985). These are not observed at E. pilopalpus sp. n. in this study. Furthermore, E. pilopalpus sp. n. is different from E. diplonyx in the following ways: (1) inner plate on maxilla 2 is not enlarged in E. pilopalpus sp. n. (vs. the inner plate of maxilla 2 is larger than the outer plate in E. diplonyx); (2) one group of fine setae on the surface of mandibular palp article 3 is present in E. pilopalpus sp. n. (vs. absent in E. diplonyx); (3) posterior lobe of the ischium on pereopods 5-7 of E. pilopalpus is more acute than that of E. diplonyx; and (4) the telson of E. pilopalpus sp. n. is cleft to one fourth of the length (vs. more than half the length in E. diplonyx) (Walker 1909;Pirlot 1936;Barnard JL 1970;Myers 1985;Ren 2012).
Maxilla 1 (Fig. 7M, N): outer plate with 10 dentate setae apically; palp long, beyond apical setae of outer plate, article 2 with 1 row of 9 setae on surface and 8 robust setae along apical and mediodistal margins, with 1 plumose and 1 simple seta at centre of lateral margin.
Maxilliped (Fig. 8A): inner plate subrectangular, swollen laterodistally, with 3 robust setae apically, with plumose setae on apex and mediodistal margin; outer plate as long as inner plate, convex laterally and wider than inner plate, with elongate plumose setae along apex and medial margin submarginally; palp elongate, slender, 4-articulate; article 2 subrectangular, longest, lined with long forked and simple setae on medial margin; article 3 thumb-shaped, with forked, serrate and simple setae on distal surface and margin; article 4 falcate, 0.8 times as long as article 3, lined with setae on medial margin, with 1 elongate seta apically.
Gnathopod 1 (Fig. 8B, C): subchelate; coxa subrectangular, ventral margin round with 5 minute setae and with 1 small notch bearing 1 minute seta posteroventrally; basis anterior margin straight with 8 minute setae, with 1 pair of elongate setae on medial surface anteroproximally, posterior margin with 1 elongate seta proximally, lined with 1 group of 4 elongate setae and with 3 minute setae, with 1 group of 3 simple setae subdistally; ischium with moderate anterior lobe, posterior margin convex with 1 simple seta and 1 group of 9 elongate setae; merus rectangular, as long as ischium, forming groove anterodistally, with medial and lateral protrusions distally, with 1 pair of short setae medially, with elongate setae in formula 1, 2, 3, 2 on posterior margin, lined with 14 long setae on distal margin; carpus longer than merus, with 1 lateral row of 5 setae anterodistally and 1 medial row of 5 setae on distal margin, posterior margin broadly lobed and weakly crenulate, with 4 groups of serrate and simple setae; propodus ovoid, as long as basis, with 4 setae on anterior margin, with 1 group of 6 simple setae at anterodistal corner, with 5 groups of serrate setae on weakly crenulate posterior margin, with setae of various combinations on medial surface, palm oblique with medial and lateral rows of simple setae, with robust defining setae of in formulae 1, 1, 3 laterally and 2, 3, 1 medially; dactylus falcate, stout, slightly shorter than palm.
Gnathopod 2 (Fig. 8D, E): also moderately subchelate, similar to gnathopod 1 in size; coxa subrectangular, with 3 minute setae on round ventral margin anteriorly, with 2 small notches posteroventrally, with 7 minute setae on anterodistal surface, coxal gill ovoid and large, slightly shorter than basis; basis anterior margin slightly convex lined with 10 minute setae, posterior margin with 1 elongate setae proximally and 1 group of 3 simple setae (2 elongate and 1 short) at proximal 1/3, lined with 7 simple setae and 1 group of 3 simple setae subdistally at distal half; ischium with moderate anterior lobe, posterior margin convex with 4 setae; merus as long as ischium, forming groove anterodistally, with medial and lateral protrusions distally, with 2 pairs of simple setae on anterior margin medially, with 1 seta and 2 pairs of setae on posterior margin distally, with 6 elongate setae on distal margin; carpus longer than merus, with 1 lateral row of 6 setae anterodistally, posterior margin broadly lobed and weakly crenulate with 5 groups of serrate and simple setae; propodus ovoid, as long as basis, with 4 simple setae on anterior margin, with 1 group of 6 simple setae at anterodistal corner, weakly crenulate posteriorly with 7 groups of serrate setae, palm more oblique than in gnathopod 1, with medial and lateral rows of simple setae, with robust defining setae laterally in formula 1, 2, 1; dactylus falcate, stout, slightly shorter than palm.
Pereopod 3 (Fig. 9A, B): coxa subrectangular, convex anteriorly, with 4 minute setae on anterior surface, ventral margin round with 3 marginal and 5 submarginal setae, with 2 small notches bearing 1 minute seta at posteroventral corner, posterior margin short, coxal gill ovoid and large, as long as coxa; basis anterior margin straight with 4 pairs and 6 minute setae, posterior margin setose; ischium short, with moderate anterior lobe, with 1 minute seta on posterior margin and 1 pair of simple setae at posterodistal corner; merus 0.7 times as long as basis, anterior margin weakly spinose and slightly expanded distally, with 1 group of 3 simple setae at anterodistal corner, posterior margin weakly setose; carpus not expanded and slightly curved, with 2 groups of simple setae on anterior margin and 1 pair of simple setae at anterodistal corner, with 1 minute and 3 pairs of simple setae on posterior margin, with several minute setae at posterodistal corner, distal margin round; propodus slender, 1.1 times as long as carpus, with 3 groups of simple setae on anterior margin and 1 row of 4 setae at anterodistal corner, with 1 small seta and 2 pair of setae on posterior margin, with 1 elongate, 1 robust and 2 moderate setae at posterodistal corner; dactylus short, with blunt protrusion bearing 1 seta on inner margin, apex curved and claw-like.
Pereopod 4 (Fig. 9C, D): coxa subquadrate, with acutely produced posterior margin; dactylus with blunt protrusion on inner margin but weaker than that of pereopod 3; other articles similar to those of pereopod 3 except for additional 1 robust seta at posterodistal corner of basis.
Pereopod 5 (Fig. 10A-D): elongate and slender; coxa bilobed, anterior lobe expanded downwards with 4 minute setae on ventral margin, posterior lobe not expanded with 1 small notch bearing 1 minute seta at posteroventral corner, coxal gill ovoid and small; basis subovoid, anterior margin convex with 1 group of 5 elongate setae proximally and lined with 7 robust setae, anterodistal corner weakly lobed downwards with 1 pair of robust setae, posterior margin moderately expanded with 13 weak serrations bearing 1 minute seta; ischium short, anterodistal corner weakly lobed downwards with 1 pair of setae, posterior lobe moderate; merus as long as basis, with short robust setae on anterior margin and with 1 pair of robust and simple setae at anterodistal corner, posterior margin weakly expanded and setose with robust setae, posterodistal corner slightly produced with 1 pair of unequal setae; carpus linear and slender, as long as merus, margins weakly setose, anterodistal and posterodistal corners with robust and simple setae; propodus also linear, 0.9 times as long as carpus, with 4 pairs of robust setae on anterior margin and with 1 group of 4 setae (1 simple elongate and 3 robust) at anterodistal corner, with 4 groups of robust and simple setae on posterior margin and with 10 setae (1 robust and 9 simple) at posterodistal corner; dactylus short, with blunt protrusion bearing 1 seta on inner margin, with curved and claw-like apex.
Pereopod 6 ( Fig. 10E): elongate and slender, longer than pereopod 5; coxa bilobed, smaller than that of pereopod 5, anterior lobe expanded downwards with 2 minute setae anteriorly, posterior lobe not expanded with notch bearing 1 minute seta at posteroventral corner, coxal gill ovoid and slightly smaller than that of pereopod 5; basis as long as that of pereopod 5, anterior margin convex with 1 elongate seta proximally and irregular spaced 7 robust and simple setae, anterodistal corner weakly lobed downwards with 1 robust seta, posterior margin expanded proximally and diminished distally, with 13 weak serrations bearing 1 minute seta and 2 minute setae distally; ischium short, anterodistal corner weakly lobed downwards with 1 group of 3 setae, posterior lobe moderate; merus as long as basis, setose with robust and simple setae on anterior margin, with 1 pair of setae at anterodistal corner, posterior margin weakly expanded and setose with elongate and short robust setae irregularly, posterodistal corner slightly produced with 1 group of 5 setae; carpus linear and slender, 1.1 times as long as merus, margins weakly setose, anterodistal and posterodistal corners with robust and simple setae; propodus also linear, as long as carpus, with 5 groups of robust and simple setae on anterior margin, and with 1 group of 4 setae (1 simple elongate and 3 robust) at anterodistal corner, posterior margin armed with setae of various combinations, with 9 setae (8 simple elongate and 1 robust) at posterodistal corner; dactylus short, with blunt protrusion bearing 1 seta on inner margin, with curved and claw-like apex.
Pereopod 7 (Fig. 11A, B): shorter but stouter than pereopod 6; coxa unilobed, with 1 simple seta at anterior corner, with 2 notches bearing 1 minute seta and 2 small naked notches on posterior margin; basis larger than that of pereopod 6, anterior margin widened with irregular spaced 8 minute setae, anterodistal corner a little lobed distally with 1 group of 3 robust setae, posterior margin expanded, angulate proximally and diminished distally, with 12 weak serrations bearing 1 minute seta and 2 naked serrations distally; ischium short, anterodistal corner weakly lobed downwards with 1 group of 5 robust setae, posterior lobe moderate; merus short, 0.7 times as long as basis, anterior margin straight and setose with single or paired setae, anterodistal corner weakly produced with 1 subapical simple seta and 1 pair of robust apical setae, posterior margin slightly expanded and setose with irregular elongate and short robust setae, posterodistal corner slightly produced with 1 group of 6 robust setae (1 elongate and 5 moderate); carpus linear, as long as basis, with 5 groups of robust setae on anterior margin and with 1 group of 7 robust setae at anterodistal corner, with 1 single and 5 groups of robust setae on posterior margin and with 1 group of 6 robust setae at posterodistal corner; propodus also linear, as long as carpus, with 5 groups of 3 robust setae on anterior margin and 1 group of 4 setae (1 simple elongate and 3 robust) at anterodistal corner, posterior margin armed with setae of various combinations, with 13 setae (2 robust and 11 simple) at posterodistal corner; dactylus short, with blunt protrusion bearing 1 seta on inner margin, with curved and claw-like apex.
Paramoera dentipleurae sp. n. can be discriminated from P. hanamurai by the following features: (1) upper and lower parts of the inferior antennal sinus do not overlap in P. dentipleurae sp. n.; (2) antenna 1 is longer than antenna 2 in P. dentipleurae sp. n., but antenna 2 is longer than antenna 1 in P. hanamurai; (3) setations of the peduncular articles on antennae 1 and 2 of P. dentipleurae sp. n. are weaker; (4) accessory flagellum has five apical setae in P. dentipleurae sp. n., but it has only two apical setae in P. hanamurai; (5) formulae of the robust defining setae at the palmar corners on gnathopods 1 and 2 are different from each other (1, 1, 3 for lateral setae and 2, 3, 1 for medial setae on gnathopod 1, and 1, 2, 1 for lateral setae in gnathopod 2 in P. dentipleurae sp. n., whereas there are three rows of three setae on the medial surface of gnathopod 1 and without setae on gnathopod 2 in P. hanamurai); (6) posterior margin of basis on pereopod 5 is more expanded distally and the length of the merus is shorter in P. hanamurai; (7) serration patterns are weaker and the posterodistal lobes are indistinct for basis on pereopods 5-7 in P. dentipleurae sp. n. compared to P. hanamurai; (8) each dorsal margin from pereon 7 to pleon 3 has a distal carina in P. dentipleurae sp. n., whereas the distal carina is absent in P. hanamurai; and (9) serration patterns of the posterior margins on the pleonal epimera are simpler in P. hanamurai compared to those in P. dentipleurae sp. n. (Hirayama 1990).