Photis longicarpus, Jung, Tae Won, Coleman, Charles Oliver & Yoon, Seong Myeong, 2019

Jung, Tae Won, Coleman, Charles Oliver & Yoon, Seong Myeong, 2019, Taxonomic study on the photid amphipods (Senticaudata, Corophiida, Photoidea, Photidae) from Korean waters, with descriptions of a new genus and seven new species, ZooKeys 886, pp. 1-59 : 1

Photis longicarpus sp. nov. Figs 14 , 15 , 16 , 17

Etymology.

The composite epithet of the specific name, longicarpus, is a combination of the Latin words longus and carpus, meaning elongate carpus. This name refers to the elongate shape of the carpus of gnathopod 2 in males.

Material examined.

Holotype: ♂ (4.9 mm), NIBRIV0000753910. Geomeunyeo, Jeju-do Island, South Korea (33°14'23"N, 126°34'59"E), 30 Dec 2012, grab sampler (about 24 m depth), by Prof. HY Soh. Paratypes: 5 ♂♂ (3.2-4.5 mm) and 1 ♀ (3.1 mm), NIBRIV0000848928. Same data as holotype.

Diagnosis.

Gnathopod 1 elongate; coxa produced anterioventrally; basis 1.2 × as long as coxa; merus half as long as basis; carpus elongate, 0.9 × as long as basis; propodus half as long as carpus. Gnathopod 2 basis lateral borders forming developed lobe anteriodistally (not sac-like), with oblique stridulated ridges on the surface; carpus slightly elongate but shorter than that of gnathopod 1, 0.6 × as long as basis; propodus stout, subovoid, 1.2 × as long as carpus, palm defined by one acute spine. Female gnathopod 1 not elongate. Female gnathopod 2 as long as female gnathopod 1, but stouter; coxa anterioventral production weaker than that of male; basis with oblique stridulated ridges on lateral surface; merus 0.4 × as long as basis; carpus 0.4 × as long as basis; propodus without defining spine, but bearing defining robust seta medially. Pereopod 3 coxa with stridulated ridges on the surface along the ventral margin laterally in both sexes. Uropod 3 outer ramus biarticulated, 2nd article vestigial; inner ramus scale-like, 0.2 × as long as outer ramus.

Description.

Holotype male. Head ( Fig. 14A ) 0.8 × as long as pereonite 1; lateral cephalic lobe subtriangular; eye small, circular; antennal sinus deep.

Antenna 1 ( Fig. 14B ) peduncle 1st article stout, 0.7 × as long as head; 2nd article slender, 1.3 × as long as 1st article; 3rd article 0.8 × as long as 2nd article; accessory flagellum absent; flagellum 0.6 × as long as peduncle 1 st– 3rd articles combined, composed of seven articles (terminal article rudimentary).

Antenna 2 ( Fig. 14C ) 1.2 × as long as antenna 1; peduncle 3rd article exceeding end of cephalic lobe, 0.4 × as long as 4th article; 4th article 1.1 × as long as 2nd article of antenna 1; 5th article 0.9 × as long as 4th article; flagellum 0.6 × as long as peduncle 3 rd– 5th articles combined, composed of six articles (terminal article rudimentary).

Upper lip ( Fig. 14D ) convex anteriorly, entire, covered with minute setae.

Mandibles ( Fig. 14E, F ) with 5-dentate incisor, 4-dentate lacinia mobilis, and five raker setae on left mandible; with 6-dentate incisor, minutely dentate lacinia mobilis, and three raker setae on right mandible; molar well developed, triturative, with seven setae along the distal margin of right mandible; palp asymmetrical, composed of three articles, 3rd article distally rounded, 0.8 × as long as 2nd article, with setae extending along most of posteriodistal margin.

Maxilla 1 ( Fig. 14G, H ) outer lobe with nine dentate robust setae on apical margin; palp biarticulated, distal article curved, a little swollen, with five setae on apical margin.

Maxilla 2 ( Fig. 14I ) inner lobe with an oblique row of plumose setae on surface; outer lobe longer and slightly dilated distally than inner lobe.

Maxilliped ( Fig. 15A ) inner lobe subrectangular, slightly expanded distally, with three nodular setae apically and one medial nodular seta subdistally; outer lobe exceeding half of palp 2nd article, lined with eight robust setae along apex to medial margin; palp composed of four articles, 3rd article slightly expanded distally, half as long as 2nd article, 4th article 0.6 × as long as 3rd article, with elongate seta apically (1.1 × as long as 4th article).

Gnathopod 1 ( Fig. 15B, C ) elongate; coxa subtriangular, half as wide as long, tapering and produced anterioventrally; ventral margin evenly rounded with six setae; basis subtrapezoidal, 1.2 × as long as coxa, anterior margin lateral border lobate distally, with three plumose setae subproximally, posterior margin convex, more swollen at the middle, with six elongate setae; merus half as long as basis; carpus elongate, 0.9 × as long as basis, 0.3 × as wide as long, slightly widened distally, carpal lobe not developed; propodus half as long as carpus, rounded anteriorly, palm half as long as posterior margin, serrated irregularly, slightly concave, defined by one robust seta medially; dactylus half as long as propodus, with five teeth (proximal three minute) on inner margin.

Gnathopod 2 ( Fig. 15D ) stout, 0.7 × as long as gnathopod 1; coxa subtrapezoidal, 1.4 × as long as that of gnathopod 1, 0.4 × as wide as long, produced anterioventrally; basis 0.7 × as long as coxa, 0.4 × as wide as long, anterior margin lateral borders forming developed lobe (but not sac-like) distally bearing oblique stridulated ridges on surface, posterior margin convex, with three elongate setae at the middle; merus 0.6 × as long as basis; carpus slightly elongate but shorter than that of gnathopod 1, 0.6 × as long as basis, with moderate carpal lobe posteriorly; propodus stout, subovoid, 1.2 × as long as carpus, anterior margin evenly rounded, posterior margin 0.7 × as long as anterior margin, palm oblique, half as long as posterior margin, defined by one acute spine; dactylus 0.4 × as long as propodus, with two teeth on inner margin.

Pereopod 3 ( Fig. 15E ) coxa widened ventrally, somewhat curved, 0.9 × as long as that of gnathopod 2, 0.7 × as wide as long, with stridulated ridges on surface along ventral margin laterally; basis expanded posteriorly, 0.4 × as wide as long, posterior margin convex, with four plumose setae in the middle; merus 0.7 × as long and 0.6 × as wide as basis, anterior margin weakly expanded, with twelve plumose setae submarginally, distal corner weakly produced; posterior margin not expanded, with four plumose setae; carpus half as long as merus; propodus diminished distally, half as long as basis; dactylus half as long as propodus.

Pereopod 4 ( Fig. 16A ) coxa not widened distally, slightly curved, half as wide as long, without stridulated ridges; other articles similar to those of pereopod 3 in shape, but plumose setae different in position.

Pereopod 5 ( Fig. 16B ) coxa 0.9 × as long as that of pereopod 4, bilobed, anterior lobe subovoid, expanded ventrally, posterior lobe small, extended backwards; basis subovoid, broad, more expanded proximally, as long as wide, with four plumose setae on medial surface anterioproximally; merus subrectangular, a little lobate anteriodistally, 0.4 × as long as basis, half as wide as long; carpus rectangular, as long and 0.9 × as wide as merus; propodus 0.9 × as long as carpus, with a pair of distal locking setae unequal in length (longer seta reaching end of dactylus), with a group of three setae (longest seta 0.9 × as long as propodus) at anteriodistal corner; dactylus short, armed with one accessory cusp on outer margin.

Pereopod 6 ( Fig. 16C ) as long as, but slender than pereopod 5; coxa bilobed, anterior lobe small, posterior lobe dilated posterioventrally; basis subovoid, 0.7 × as wide and as that of pereopod 5, anterior margin convex, slightly dilated distally, posterior margin convex, with four notches irregularly; merus rectangular, weakly widened distally, half as long as basis, 0.3 × as wide as long; carpus as long as merus; propodus as long as carpus, with a pair of distal locking setae unequal in length, with a group of five setae (longest seta 0.8 × as long as propodus) at anteriodistal corner; dactylus half as long as propodus, without accessory cusp on outer margin.

Pereopod 7 ( Fig. 16D ) as long as pereopod 6; coxa unilobed; basis subovoid, as long and 0.8 × as wide as that of pereopod 6, 0.6 × as wide as long, anterior margin rather convex, posterior margin weakly dilated distally; posterior margin proximal extension weak, with five notches irregularly; merus rectangular, linear, 0.2 × as wide as long, half as long as basis; carpus as long as merus; propodus 1.1 × as long as carpus, with a pair of distal locking setae unequal in length shorter than that of pereopods 5-6, with a group of more than five setae at posteriodistal corner; dactylus half as long as propodus, armed with one accessory cusp on outer margin.

Epimera 2 and 3 ( Fig. 16E ) each posterioventral corner produced backwards.

Uropod 1 ( Fig. 16F ) peduncle without distoventral spine, with seven robust setae on dorsolateral margin and one robust seta distally on dorsomedial margin; both rami 0.7 × as long as peduncle, with three and two robust setae on dorsal margin of outer and inner rami, each apex with one stout seta and two robust setae.

Uropod 2 ( Fig. 16G ) 0.6 × as long as uropod 1; peduncle half as long as that of uropod 1, with three robust setae on dorsolateral margin and one robust seta distally on dorsomedial margin; inner ramus 1.2 × as long as peduncle, with three robust setae on dorsal margin and with one stout seta and two robust setae at apex; outer ramus 0.8 × as long as inner ramus, with two robust setae on dorsal margin and with one stout seta and two robust setae at apex.

Uropod 3 ( Fig. 16H ) as long as uropod 2; peduncle 1.4 × as long as that of uropod 2; outer ramus biarticulated, 0.6 × as long as peduncle, 2nd article vestigial, with two elongate setae subapically; inner ramus scale-like, 0.2 × as long as outer ramus.

Telson ( Fig. 16I ) triangular in dorsal view, with a pair of simple setae and a pair of sensory setae on each side.

Paratype female. Gnathopod 1 ( Fig. 17B, C ) not elongate; coxa similar to that of male; basis subtrapezoidal, posterior margin flatter than that of male; carpus not elongate, 0.6 × as long and 1.1 × as wide as basis, carpal lobe blunt; propodus as long as carpus, posterior margin convex, palm serrated, slightly convex proximally and bearing weak cavity distally, defined by one robust seta medially; dactylus 0.6 × as long as propodus, inner margin serrated, with one tooth.

Gnathopod 2 ( Fig. 17D, E ) as long as but stouter than gnathopod 1; coxa subrectangular, 1.2 × as long as that of gnathopod 1, half as wide as long, anterioventral production weaker than that of male, oostegite 1.3 × as long as basis, 0.4 × as wide as long; basis anterior margin lateral borders forming well-developed lobe distally bearing oblique stridulated ridges on surface; merus 0.4 × as long as basis; carpus 0.4 × as long as basis, with developed carpal lobe posteriorly; propodus stout, 0.6 × as long as basis, posterior margin 0.6 × as long as anterior margin, palm oblique, 0.9 × as long as posterior margin, without defining spine, but bearing defining robust seta medially; dactylus 0.4 × as long as propodus, inner margin serrated, with one tooth.

Pereopod 3 ( Fig. 17F ) coxa widened distally, 0.6 × as wide as long, slightly produced posterioventrally, with stridulated ridges on surface along ventral margin, oostegite as long and as wide as that of gnathopod 2; basis 0.4 × as wide as long, anterior margin slightly expanded proximally, posterior margin evenly rounded; merus half as wide as long, anterior margin expanded, with eleven plumose setae submarginally, distal corner weakly produced; posterior margin not expanded, with four plumose setae; carpus rectangular, half as long as merus; propodus diminished distally, 0.4 × as long as basis; dactylus half as long as propodus.

Oostegites on gnathopod 2 as long as that of pereopod 3. That of pereopod 5 0.7 × as long as that of pereopod 4 ( Fig. 17D, F–H ).

Remarks.

This species is closely related to Photis japonica Hirayama, 1984 in sharing a significantly elongate gnathopod 1 in mature males, but differs in having stridulated ridges on the lateral surface of gnathopod 1 basis and pereopod 3 coxa, which are arranged along the ventral margin in both sexes. Also, Photis longicarpus sp. nov. has a defining spine on gnathopod 2 palm in males only, but P. japonica has it in both sexes. Moreover, the uropod 3 outer ramus of P. longicarpus sp. nov. is biarticulated (distal article is vestigial), but that of P. japonica is uniarticulated ( Hirayama 1984).

Figures

Figure 14. Photis longicarpus sp. nov., holotype, NIBRIV 0000753910, male, 4.9 mm, Geomeunyeo, Jeju-do, South Korea. A habitus B antenna 1 C antenna 2 D upper lip E left mandible F right mandible G, H maxilla 1 I maxilla 2. Scale bars: 0.05 mm (D, G-I), 0.1 mm (E, F), 0.2 mm (B, C), 0.5 mm (A).

Figure 15. Photis longicarpus sp. nov., holotype, NIBRIV 0000753910, male, 4.9 mm, Geomeunyeo, Jeju-do, South Korea. A maxilliped B, C gnathopod 1 D gnathopod 2 E pereopod 3. Scale bars: 0.05 mm (A, C), 0.2 mm (B, D, E).

Figure 16. Photis longicarpus sp. nov., holotype, NIBRIV 0000753910, male, 4.9 mm, Geomeunyeo, Jeju-do, South Korea. A pereopod 4 B pereopod 5 C pereopod 6 D pereopod 7 E pleonal epimera F uropod 1 G uropod 2 H uropod 3 I telson. Scale bars: 0.1 mm (F-I), 0.2 mm (A-E).

Figure 17. Photis longicarpus sp. nov., paratype, NIBRIV 0000848928, female, 3.1 mm, Geomeunyeo, Jeju-do, South Korea. A habitus B, C gnathopod 1 D, E gnathopod 2 F pereopod 3 G, H oostegites of pereopods 4 and 5. Scale bars: 0.05 mm (C, E), 0.2 mm (A, B, D, F-H).