Gammaropsis longipropodi Hirayama, 1984

Jung, Tae Won, Choi, Hyun Ki, Kim, Min-Seop & Yoon, Seong Myeong, 2017, Two new species of amphipods (Crustacea: Amphipoda: Photidae) from Korean waters with a redescription of Gammaropsis longipropodi, Zootaxa 4300 (3), pp. 380-402 : 381-394

publication ID	https://doi.org/ 10.11646/zootaxa.4300.3.3
publication LSID	lsid:zoobank.org:pub:5EB278E4-1821-4A6E-8624-37C13162B9C2
DOI	https://doi.org/10.5281/zenodo.6028845
persistent identifier	https://treatment.plazi.org/id/1C5FF62E-FFB4-F868-FF07-FB89A9D1FE39
treatment provided by	Plazi
scientific name	Gammaropsis longipropodi Hirayama, 1984
status

Treatment

(Korean Name: Gin-pal-but-eun-kko-ri-yeop-sae-u, new) ( Figures. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Gammaropsis longiprotopodi Hirayama, 1984 , p. 74, figs. 92–94.

Material examined. one male (NIBRIV325712) and one female (NIBRIV325713), dissected appendages are mounted on permanent slide glasses and remain body is preserved in 99% ethanol; one male and one female (NIBRIV325714), preserved in 95% ethanol; collected from Nonggado Island (34°50′11″N, 128°09′28″E), Saryang-myeon Tongyeong-si Gyeongsangnam-do South Korea , 19 Apr. 2009, SCUBA diving (15–17 m depth), by T.W. Jung. five males and three females (NIBRIV470376), preserved in 99% ethanol; collected from Maando Island (35°45′10″N, 128°04′14″E), Mulgeon-ri Samdong-myeon Namhae-gun Gyeongsangnam-do South Korea , 2 Jul. 2009, SCUBA diving (11–15 m depth), by T.W. Jung. GoogleMaps

Description. Male. Body about 2.6 mm long.

Head ( Fig. 1 View FIGURE 1 A) 1.1x length of pereonites 1–2 combined; rostrum indistinct; anterior cephalic lobe produced forward, with round apex; eyes circular, moderate, occupying most of cephalic lobe; inferior antennal sinus deep.

Antenna 1 ( Fig. 1 View FIGURE 1 A) setose with single or paired setae posteriorly; with peduncular articles 1–3 in length ratio of 1:1.3:1; peduncular article 1 stout, drastically diminished distally; peduncular articles 2–3 prolonged, rectangular; accessory flagellum 3-articulate, long, 0.8x length of peduncular article 3; flagellum 8-articulate, as long as peduncular articles 2–3 combined, each article with aesthetasc and setae posterodistally.

Antenna 2 ( Fig. 1 View FIGURE 1 A) as long as antenna 1, also setose with single or paired setae posteriorly; gland cone developed; with peduncular articles 3–5 in length ratio of 1:2:2; flagellum 7-articulate, articles with setae distally.

Lower lip ( Fig. 1 View FIGURE 1 B) inner and outer lobes distinct, apical margin densely pubescent distally, mandibular process well developed.

Left mandible ( Fig. 1 View FIGURE 1 D, E) with 5-dentate incisor and 4-dentate lacinia mobilis; accessory setal row with four broaden dentate setae; molar triturative with a long plumose seta; palp 3-articulate; article 2 somewhat expanded medially, obliquely truncated and with five simple and three plumose setae distally; article 3 0.7x length of article 2, swollen medially, apex blunt with numerous long setae, with an oblique row of setae on surface.

Right mandible ( Fig. 1 View FIGURE 1 C) with four and 1/2-dentate incisor and multidentate lacinia mobilis; accessory setal row with three dentate setae; molar well developed, with a long plumose seta.

Maxilla 1 ( Fig. 1 View FIGURE 1 F) inner plate, apex triangulate with a seta subapically; outer plate subrectangular, apex lined with ten dentate setae; palp bi-articulate, slightly curved, apex of article 2 blunt with three stout setae distally and three simple setae subdistally.

Maxilla 2 ( Fig. 1 View FIGURE 1 G) inner plate ovoid, with several setae on distal half of medial margin and an oblique row of setae on surface; outer plate apex swollen and lined with several distal and subdistal setae.

Maxilliped ( Fig. 1 View FIGURE 1 H–J) inner plate subrectangular, expanded distally, with three plumose setae, one subdistal and three distal stout setae on apex, with a row of five long setae on proximal surface; outer plate elongate semiovoid, with eight stout setae gradually increasing from distal half to apex of medial margin and several groups of two or three long setae arranged on surface, with a row of five long setae on proximal surface; palp slender, 4- articulate; article 1 apex truncated obliquely; article 2 longest, slightly curved, lined with several paired setae on medial margin; article 3 swollen distally, with five plumose setae on mediodistal margin and four setae at laterodistal corner; article 4 short, with a simple and a long serrate seta at distal corner.

Gnathopod 1 ( Fig. 2 View FIGURE 2 A) coxa slightly expanded anteroventrally, with a small notch bearing a minute seta at posteroventral corner, convex and lined with several minute setae on ventral margin; basis moderate, somewhat curved, without setae on anterior margin, with three long setae on posterior margin; ischium with small anterior lobe, with a group of three unequal setae at posterodistal corner; merus larger than ischium, with short anterior margin, with angulate posterior margin bearing a row of several setae proximally, with a pair of setae on surface; carpus trapezoidal, with slightly convex anterior margin, with a pair of setae at anterodistal corner, posterior margin as long as half of anterior margin, weakly crenulate and line with numerous setae on posterior margin, with five groups of two or three setae on lateral surface; propodus as long as anterior margin of carpus, with a pair of setae at anterodistal corner, setose on lateral surface submarginally, posterior margin slightly longer than half of anterior margin, with weakly expanded and crenulate posterior margin bearing three groups of setae, palm concave, with several setae and a small protrusion near dactylus hinge, defined by a stout seta; dactylus falcate, apex beyond palm, lined with small teeth and minute setae on inner margin.

Gnathopod 2 ( Fig. 2 View FIGURE 2 B) enlarged; coxa slightly expanded anteroventrally, with a small notch bearing a minute seta at posterodistal corner, ventral margin convex and lined with several minute setae; basis slightly curved proximally and drastically increasing in width, anterior and posterior margins subparallel, with seven single and one paired setae arranged from proximal to distal anterior margin, with a long seta on posterior margin centrally; ischium without setae, with small anterior lobe; merus subrectangular, posterodistal corner produced roundly with a group of three setae; carpus triangular, 0.5x length of basis, with a group of four unequal setae at anterodistal corner, lined with several setae on posterior margin and posterodistal corner; propodus prolonged subrectangular, as long as basis, anterior margin slightly convex, gradually widening distally but greatest width at distal 2/3 of anterior margin, with a group of several setae at anterodistal corner, posterior margin straighten with five groups of setae and three single setae, lateral surface covered with several oblique rows of setae and single setae, palm transverse, with two strong triangular protrusions; dactylus falcate, not fitting palm, lined with small teeth and minute setae on inner margin.

Pereopod 3 ( Fig. 2 View FIGURE 2 C) coxa subrectangular, convex anteriorly, with a small notch bearing a minute seta at posteroventral corner, ventral margin convex and lined with several minute setae; basis weakly angulate at centre of anterior margin with two short setae, with three setae at anterodistal corner, posterior margin largely lobate and drastically expanded but somewhat flatten at centre with two long setae, distal 1/3 of posterior margin diminished in width with a seta distally; ischium with a seta posterodistally, with small anterior lobe; merus gradually expanded anterodistally with two setae, anterodistal corner produced with a group of three stout setae, posterior margin with a small seta and a group of three setae at posterodistal corner; carpus subrectangular, shorter than half of merus, with a pair of setae at slightly produced anterodistal corner, with two setae on posterior margin and with a pair of setae at posterodistal corner; propodus shorter than merus, drastically diminished in width, anterior margin convex proximally with a seta, with a group of six long setae at anterodistal corner, lined with several setae on posterior margin; dactylus falcate, as long as half of propodus.

Pereopod 4 ( Fig. 2 View FIGURE 2 D, E) similar to pereopod 3 in shape.

Pereopod 5 ( Fig. 2 View FIGURE 2 F, G) coxa bilobate, anterior lobe subrectangular, larger than posterior lobe, expanded distally, convex and lined with several minute setae on ventral margin, posterior lobe with two stout setae; basis broadly expanded proximally, gradually diminished in width, with convex anterior margin presented by seven small setae, with a pair of small setae at anterodistal corner, posterior margin weakly crenulate and lined with six minute setae; ischium with a pair of setae anterodistally, posterior lobe moderate; merus, anterior margin smooth with a seta and with a group of stout and simple seta at anterodistal corner, posterior margin gradually expanded distally with two setae, posterodistal corner slightly produced with a group of stout and simple seta; carpus rectangular, smaller than merus, slightly convex, each distal corners with a group of three long setae anteriorly and a paired setae posteriorly; propodus slender, slightly shorter than merus and carpus combined, somewhat narrower proximally, with three groups of stout and simple seta on anterior margin and a pair of setae on lateral surface, with a group of four setae at posterodistal corner; dactylus falcate, as long as about 1/3 of propodus.

Pleonal epimera ( Fig. 3 View FIGURE 3 A) posterior margin of each epimeron somewhat roundish expanded backward.

Uropod 1 ( Fig. 3 View FIGURE 3 C) peduncle rectangular with three lateral and three medial setae dorsally, inter-ramal process well developed, reaching half of inner ramus; both rami linear and slender; outer ramus shorter than inner ramus with a medial seta, with a group of four setae on apex; inner ramus with two medial setae, with five unequal setae on apex.

Uropod 3 ( Fig. 3 View FIGURE 3 B) biramus, as long as peduncle of uropod 1; peduncle rectangular with a lateral and a medial setae dorsodistally; rami lancerolate, outer ramus shorter than inner ramus, with a lateral seta, apex produced with a small seta; inner ramus with one lateral and two medial setae, apex produced with a small seta.

Telson ( Fig. 3 View FIGURE 3 B) flesh, distal margin concave, apex of each side with pair of setae.

Female. Body about 2.4 mm long.

Gnathopod 1 ( Fig. 3 View FIGURE 3 D) coxa to carpus almost identical to those of male; propodus not crenulate posteriorly, defining spine small, palm oblique but not concave, possessing small protrusion located at dactylus hinge that absent in males.

Gnathopod 2 ( Fig. 3 View FIGURE 3 E–G) not enlarged; propodus, palm concave with two defining setae; oostegite well developed, margin lined with long setae.

Remarks. According to the original description of Gammaropsis longiprotopodi Hirayama, 1984 , this species is characterized by specific gnathopod 2 in that the posterior margin of the carpus is not slenderly produced between the merus and the propodus, the propodus is uniform in width and very elongate, and the palm is transverse ( Hirayama, 1984). The Korean specimens agree well with those of the original description. Therefore, they are readily assigned to G. longiprotopodi . However, Korean specimens show some minor differences from the original description in mouth parts with the following features: 1) there are three apical setae on palp of maxilla 1 in Korean specimens (vs. five setae in original description); 2) the accessory setal row of right mandible has three dentate setae in Korean specimens (vs. four dentate setae in original description); 3) the inner plate of maxilliped is not oblique apically in Korean specimens (vs. slightly oblique in original description); and 4) the outer plate of maxilliped is elongate and semi-ovoid in shape in Korean specimens (vs. round apically in original description ( Hirayama, 1984).

Photis stridulus sp. nov.

(Korean Name: Teol-son-i-hyeong-kko-ri-da-ri-yeop-sae-u, new) ( Figures. 4–7 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Type locality. Maando Island (35°45′10″N, 128°04′14″E), Mulgeon-ri Samdong-myeon Namhae-gun Gyeongsangnam-do South Korea. GoogleMaps

Material examined. Holotype: female (NIBRIV470377), dissected appendages are mounted on permanent slide glasses and remain body is preserved in 99% ethanol; collect from type locality at 2 Jul. 2009, SCUBA diving (13–17 m depth), by T.W. Jung.

Etymology. The specific name is the Latin stridulus referring to having well developed stridulation ridges on the basis of gnathopod 2 and the coxa of pereopod 3.

Description. Holotype Female. Body about 2.7 mm long.

Head ( Fig. 4 View FIGURE 4 A) rostrum minute; anterior cephalic lobe subtriangular, slightly produced forward; eyes circular, moderate; inferior antennal sinus not deep.

Antenna 1 ( Fig. 4 View FIGURE 4 B) setose with feebly plumose setae posteriorly, with peduncular articles 1–3 in length ratio of 1:1.2:0.9; peduncular article 1 stout, with a short plumose seta on anterior margin and two pairs of plumose setae at posterodistal corner; peduncular articles 2–3 slender; flagellum 6-articulate, articles with setae distally, distal article with aesthetasc.

Antenna 2 ( Fig. 4 View FIGURE 4 C, D) as long as antenna 1, also setose with feebly plumose setae posteriorly; gland cone not developed; with peduncular articles 3–5 in length ratio of 1: 2.1:2 peduncular articles 4–5 slender and slightly curved, with plumose setae anterodistally; flagellum 7-articulate, articles with setae distally, article 6 with a pair of dentate setae distally, article 7 reduced.

Upper lip ( Fig. 4 View FIGURE 4 E) subhexagonal, slightly concave and covered with minute setae apically.

Lower lip ( Fig. 4 View FIGURE 4 F) inner lobe ovoid, with minute setae on apical and medial margins; outer lobe swollen apically with minute setae, mandibular process produced.

Left mandible ( Fig. 4 View FIGURE 4 I) with 4-dentate incisor and 4-dentate lacinia mobilis; accessory setal row with four dentate setae; molar triturative with a plumose seta; palp robust, 3-articulate; article 1 shortest; article 2 concave with 14 setae medially, and with two setae on lateral surface; article 3 slightly swollen, 0.7x length of article 2, with two and three setae on lateral surface, with six serrate setae on half of medial margin and five serrate setae on distal margin.

Maxilla 1 ( Fig. 4 View FIGURE 4 G) outer plate with ten dentate setae apically; palp bi-articulate; article 1 short, obliquely truncated distally; article 2 slightly dilated distally, with a row of four serrate setae on distal surface and six stout setae apically.

Maxilla 2 ( Fig. 4 View FIGURE 4 H) inner plate with five plumose setae along medial margin, apex with several simple setae marginally and serrate setae submarginally; outer plate larger than inner plate, lined with several marginal and submarginal simple setae on apex, with three feebly plumose setae at laterodistal corner.

Maxilliped ( Fig. 4 View FIGURE 4 J) inner plate slightly expanded laterodistally, with three stout and four plumose setae on apex, with a stout seta on medial margin subdistally and eight plumose setae on surface; outer plate elongate semicircular, not exceeding distal end of palp article 2, with eight stout setae those gradually increasing from distal half to apex of medial margin and with five pairs of facial setae bearing round apices; palp 4-articulate, slender; article 1 obliquely truncated distally; article 2 not expanded, setose medially; article 3 slightly dilated, with setae distally; article 4 falcate, slightly shorter than article 3, with a elongate seta apically.

Gnathopod 1 ( Fig. 5 View FIGURE 5 A, B) coxa expanded forward and slightly diminished ventrally, obliquely truncated proximally, ventral margin round and minutely crenulate, lined with ten setae; basis not slender, width almost steady in distal 3/4, with weak anterior lobe, with one abnormal and three serrate setae on anterior margin, with nine serrate and 13 short setae on posterior margin and a group of three setae at posterodistal corner; ischium with moderate anterior lobe, lined with ten setae on mediodistal and laterodistal margins successively; merus subrectangular, longer than ischium, produced anterodistally, angulate at distal 2/3 of posterior margin with four setae, with two rows of three and eight setae on lateral surface subdistally; carpus trapezoidal, 0.6x length of basis, anterior margin slightly convex with three submarginal setae and with two groups of two and four setae at anterodistal corner, posterior margin weakly crenulate and expanded downward with four pairs of serrate setae, with two oblique rows of setae on marginal surface laterally and setae on medial surface; propodus elongate triangular, gradually diminished distally, as long as carpus, anterior margin convex with two pairs of setae and with a group of six setae at anterodistal corner, posterior margin lined with four groups of three setae submarginally, with stout defining setae located at centre, distal 2/3 of posterior margin finely pectinate and with five setae, palm indistinct with a small seta near hinge; dactylus falcate, stout, 0.6x length of propodus, with pectinate inner margin, with developed distal teeth bearing three setae, with a feebly plumose seta.

Gnathopod 2 ( Fig. 5 View FIGURE 5 C, D) coxa enlarged, subrectangular, obliquely truncated proximally, ventral margin convex and minutely crenulate, lined with 13 setae; basis stout, shorter than coxa, with six minute setae on anterior margin and three long setae on medial surface proximally, with developed distal lobe possessing oblique stridulation ridges composed of 26 engraved slots on lateral surface and its apex reaching distal end of ischium, with three long plumose and 13 short setae on posterior margin and one plumose and three simple setae at posterodistal corner; ischium with small anterior lobe, with a seta on posterior margin and a group of three setae at posterodistal corner; merus subrectangular, smoothly diminished distally in width, setose distally; carpus convex anteriorly, with a row of eight setae along distal margin, with developed carpal lobe posteriorly bearing setae on convex apex; propodus 1.5x length of carpus, convex and densely setose anteriorly, slightly expanded posteriorly, palmer margin distinct and concave with small seta, densely setose submarginally, defined by a stout seta; dactylus falcate, stout, 0.6x length of propodus, pectinate on anterior margin, with developed distal teeth bearing three setae, with a feebly plumose seta.

Pereopod 3 ( Fig. 5 View FIGURE 5 E, F) coxa subrectangular, slightly dilated anteroventrally, with a long seta at anteroventral corner and lined with eight short setae on ventral margin, with stridulation ridges composed of 33 oblique engraved slots on ventral margin submarginally; basis stout, 0.9x length of coxa, lined with eight minute setae and with two simple and four serrate setae proximally, with a pair of unequal plumose setae on anterior margin distally, posterior margin slightly expanded and lined with four serrate and nine simple setae, with seven plumose setae distally; ischium with moderate anterior lobe, with three plumose setae on posterior margin centrally and a group of three long setae at posterodistal corner; merus 0.6x length of basis, anterior margin expanded and produced distally, densely setose with plumose setae marginally and submarginally, posterior margin straight with one simple and five plumose setae, with a pair of setae at posterodistal corner; carpus rectangular, 0.6x length of merus, with a pair of long setae at anterodistal corner, with two groups of unequal setae on posterior margin; propodus 1.3x length of carpus, not slender and slightly diminished in width distally, with two long setae on anterior margin and a group of four setae at anterodistal corner, with two minute setae on posterior margin and three setae at posterodistal corner; dactylus falcate, 0.6x length of propodus.

Pereopod 4 ( Fig. 6 View FIGURE 6 A, B) coxa subrectangular, slightly curved distally, lined with eight setae on ventral margin; basis expanded, slightly larger than that of pereopod 3, anterior margin weakly angulate centrally and lined with seven single and one paired setae, with three serrate setae proximally and two plumose setae distally, posterior margin with six long serrate setae at centre, distal 2/3 of posterior margin forming slightly swollen lobe lined with eleven plumose setae; ischium with moderate anterior lobe, with a pair of simple and plumose setae at posterodistal corner; merus 0.5x length of basis, anterior margin expanded, anterodistal corner weakly produced with a group of six setae, posterior margin straight with a simple and a plumose seta proximally, posterodistal corner with a group of four setae; carpus subrectangular, 0.6x length of merus, convex anteriorly, with a long seta at anterodistal corner, with a pair of setae on posterior margin, posterodistal corner slightly oblique with a pair of setae; propodus not slender, 1.4x length of carpus, gradually diminished in width distally, with a single and a pair of setae on anterior margin and with a group of three setae at anterodistal corner, with two minute setae on posterior margin and with a seta at posterodistal corner; dactylus falcate, 0.5x length of propodus.

Pereopod 5 ( Fig. 6 View FIGURE 6 C–E) shorter than pereopod 4, with length ratio of ischium, merus and carpus 1:1.5: 2; coxa bilobate, anterior lobe enlarged, circular, expanded downward, lined with ten setae on ventral margin, posterior lobe smaller and about 1/4 of anterior lobe, with a minute seta ventrally; basis subcircular, slightly expanded back and forth, lined with twelve minute setae on anterior margin, with 17 plumose setae on medial surface, with five minute setae on posterior margin; ischium quadrate, broader than long, with a seta at anterodistal corner, with moderate posterior lobe; merus rectangular, anterior margin slightly convex, with a group of three setae at anterodistal corner and a seta at posterodistal corner; carpus rectangular, slightly diminished than merus in width, anterior margin convex, with a pair of unequal setae at anterodistal corner, with a minute seta on posterior margin and a group of one serrate and three unequal setae at posterodistal corner; propodus not slender, width steady, as long as carpus, with one stout and two simple setae at anterodistal corner, with a seta on posterior margin and a stout seta at posterodistal corner; dactylus short, reduced, slightly sinuous posteriorly, with two pairs of setae on anterior margin distally and a lateral seta on posterior margin distally, unguis slightly curved distally.

Pereopod 6 ( Fig. 6 View FIGURE 6 F–H) slender, longer than pereopod 5; coxa bilobate, not deep, anterior lobe with one plumose and three simple setae, posterior lobe round with two minute setae ventrally; basis subovoid, anterior margin swollen and slightly dilated distally with seven minute setae proximally, posterior margin slightly expanded proximally and lined with eight minute setae; ischium subquadrate, broader than long, with a pair of setae at anterodistal corner, with moderate posterior lobe; merus, carpus and propodus rectangular, width steady, with length ratio of 1:1.3:1.4; merus with a seta at anterodistal and posterodistal corners, respectively; carpus with a pair of stout and simple seta at anterodistal corner and a group of three setae at posterodistal corner; propodus with a pair of unequal setae at anterodistal corner and with a group of six setae at posterodistal corner; dactylus falcate, 0.4x length of propodus, slightly wrinkly anteriorly, with a seta and a denticle on anterior margin distally and a long plumose seta on posterior margin proximally, unguis developed.

Pereopod 7 ( Fig. 7 View FIGURE 7 A, B) slightly longer and slender than pereopod 6; coxa unilobate, semiovoid, with one plumose and five minute setae anteriorly and one minute seta posteroventrally; basis subovoid, smaller than that of pereopod 6, anterior margin slightly convex, lined with eleven simple setae and with five plumose setae distally, posterior margin more extended, weakly angulate proximally, lined with six setae, with a pair of setae at posterodistal corner, with one simple and two plumose setae on medial surface; ischium subrectangular, with a seta at anterodistal corner, with moderate posterior lobe; merus, carpus and propodus rectangular, width steady, with length ratio of 1:1.1:1.3; merus with a long seta at posterodistal corner; carpus with a group of three setae at posterodistal corner; propodus with two setae on anterior margin, a pair of stout setae at anterodistal corner and a group of seven setae at posterodistal corner; dactylus falcate, 0.5x length of propodus, slightly wrinkly anteriorly, with a seta and a denticle on anterior margin distally and a long plumose seta on posterior margin proximally, unguis developed.

Pleonal epimera ( Fig. 4 View FIGURE 4 K) epimeron 1 round ventrally with a plumose seta submarginally; epimeron 2 subrectangular, slightly extended backward, round ventrally with two plumose setae submarginally; epimeron 3 produced backward at posteroventral corner, ventral margin with one plumose and three short setae submarginally.

Pleopod 1 ( Fig. 7 View FIGURE 7 G) peduncle subquadrate, short, with twelve plumose setae marginally and submarginally on distal half of lateral margin, with a pair of retinaculae at mediodistal corner; inner ramus longer than outer ramus, both rami 10-articulate and articles with a pair of plumose setae distally.

Pleopod 2 ( Fig. 7 View FIGURE 7 H) peduncle subquadrate, short, with four plumose setae submarginally and two simple setae distally on lateral margin, with a pair of retinaculae at mediodistal corner; inner and outer rami 9-articulate and 10- articulate, respectively, articles with a pair of plumose setae distally.

Pleopod 3 ( Fig. 7 View FIGURE 7 I) shortest; peduncle with one simple and three plumose setae submarginally and three setae distally on lateral margin, with a pair of retinaculae at mediodistal corner; inner and outer rami 8-articulate and 9- articulate, respectively, articles with a pair of plumose setae distally.

Uropod 1 ( Fig. 7 View FIGURE 7 C) peduncle longer than rami, with one medial and twelve lateral setae dorsodistally; inner ramus with three dorsomedial and four apical setae; outer ramus slightly shorter than inner ramus, with nine dorsolateral and two apical setae.

Uropod 2 ( Fig. 7 View FIGURE 7 D) shorter than uropod 1; peduncle with five lateral setae dorsally; inner ramus longer than outer ramus, with four dorsal and three apical setae; outer ramus with four dorsal and three apical setae.

Uropod 3 ( Fig. 7 View FIGURE 7 E) biramus; peduncle 0.9x length as long as that of uropod, gradually convergence distally; inner ramus very short, triangular, with a seta apically; outer ramus bi-articulate; proximal article 0.5x length of peduncle, with two dorsal and one pair of distal setae, distal article very short, with a simple and a stout seta apically.

Telson ( Fig. 7 View FIGURE 7 F) fleshy, triangular in dorsal view, both outer sides with a tubercle and a short seta.

Male. Unknown.

Remarks. This new species is closely similar to Photis ariakensis ( Hirayama, 1984) . However, Photis stridulus sp. nov. can be easily distinguished from P. ariakensis by the following features: 1) the carpus on gnathopod 1 of P. stridulus sp. nov. is slightly longer than that of P. ariakensis ; 2) the palm on gnathopod 1 of P. stridulus sp. nov. is short but obviously distinguishable (vs. indistinct in P. ariakensis ); 3) the oblique stridulation ridge on the lateral surface of the basis on gnathopod 2 is present (vs. absent in P. ariakensis ); 4), the palm of gnathopod 2 is quite different between the two species: the posterior margin of the propodus in P. stridulus sp. nov. is longer than that of P. ariakensis and the palmer margin is more excavate in P. stridulus sp. nov.; 5) the posterior margins of bases on pereopods 6 and 7 are more expanded proximally in P. stridulus sp. nov.; and 6) the posteroventral corner of pleonal epimera 3 is more produced in P. stridulus sp. nov. (vs. oblique in P. ariakensis ) ( Hirayama, 1984).

Myers (2009) has mentioned that genus Photis exhibits no or very little sexual dimorphism, different from other corophiidean amphipods ( Myers, 2009). However, the anterodistal lobe and stridulation ridges of the basis on gnathopod 2 as well as the ventral stridulation ridges on coxa 3 are dimorphic sexually in several species ( Conlan, 1983). In general, the anterodistal lobe of the basis on gnathopod 2 in females is absent or weaker than that in males. However, several species have developed anterodistal lobe of basis on gnathopod 2 in females, including Photis baeckmannae Gurjanova, 1951 , P. bifurcata Barnard, 1962 , P. californica Stout, 1913 , P. coeca Barnard, 1962 , P. conchicola Alderman, 1936 , P. fischmanni Gurjanova, 1951 , P. hawaiensis J.L. Barnard, 1955 , and P. spinicarpa Shoemaker, 1942 ( Stout, 1913; Alderman, 1936; Gurjanova, 1951; Barnard, 1955, 1962; Conlan, 1983).

Among them, only one species, P. fischmanni , has stridulation ridges of the basis on gnathopod 2 and coxa 3 simultaneously in females. This new species, P. stridulus sp. nov. also has anterodistal lobe and stridulation ridges of the basis on gnathopod 2 and ventral stridulation ridges on coxa 3 in female. However, P. stridulate is readily discriminated from P. fischmanni based on the following features: 1) the degree of setation of the appendages is weaker than that of P. fischmanni ; 2) the eyes are not occupying most regions of the anterior cephalic lobe (vs. occupying most regions in P. fischmanni ); and 3) the carpus and propodus on gnathopod 1 are slender than those of P. fischmanni (vs. more expanded posteriorly in P. fischmanni ) ( Gurjanova, 1938; Conlan, 1983).