Photis bronca, 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 bronca sp. nov. Figs 8 , 9 , 10 , 11

Photis longicaudata : Nagata 1965: 310, fig. 35; Hirayama 1984: 42, fig. 71; Kim et al. 2005: 3, figs 1, 2; Ren 1992: 259, fig. 28; 2000: 141, fig. 4; 2006: 398, fig. 171 [non P. longicaudata (Spence Bate & Westwood, 1862)].

Etymology.

The epithet of the specific name, bronca, has its origin from the Latin word broncus. This name refers to the bearing of a quadrate tooth medially on the gnathopod 2 palmar margin in both sexes.

Material examined.

Holotype: ♂ (5.8 mm), NIBRIV0000848472; Daryeo-do Island, Bukchon, Jeju-do, South Korea (34°33'27"N, 126°41'49"E); 30 Nov, 2012; grab sampler (about 20 m depth), by Prof. HY Soh. Paratypes: 2 ♂♂ (2.3 and 2.5 mm), 3 ♀♀ (ovigerous; 3.2-5.3 mm), NIBRIV0000848473; same data as holotype.

Additional materials: 3 ♂♂ 2 ♀♀, NIBRIV0000848930, Saekkiseom, Ae-do Island, Mijo-myeon, Gyeongsangnam-do, South Korea (34°41'31"N, 128°02'00"E), 1 May 2009, Scuba diving (about 20 m depth), by TW Jung; 2 ♂♂, NIBRIV0000848931, Jeolmyeongyeo, Chuja-do Island, Jeju-do, South Korea (33°52'04"N, 126°18'43"E), 12 Jul, 2016, Scuba diving (about 16 m depth), by CH Yi; 3 ♂♂ 2 ♀♀, NIBRIV0000848932, Yenae-ri, Goheung-gun, Jeollanam-do, South Korea (34°27'24"N, 127°31'16"E), 28 Mar 2017, washing macro-algae, by SH Kim.

Diagnosis.

In both sexes, gnathopod 2 propodus palmar margin with subrectangular cavity bearing one rectangular tooth medially. Male gnathopod 2 basis lateral margin forming a well-developed sac-like lobe. Stridulated ridges only present on male gnathopod 2 basis and coxae 3 and 4 (absent in females).

Description.

Holotype male. Head ( Fig. 8A ) as long as pereonites 1 and 2 combined; lateral cephalic lobe rounded; eye circular, moderate in size, located in the middle of lateral lobe; antennal sinus deep.

Antenna 1 ( Fig. 8B ) 0.4 × as long as body; peduncle 1st article stout, 0.7 × as long as head; 2nd article slender, 1.3 × as long as 1st article; 3rd article 0.6 × as long as 2nd article; accessory flagellum absent; flagellum 0.8 × as long as peduncle 1 st– 3rd articles combined, composed of ten articles (terminal article rudimentary).

Antenna 2 ( Fig. 8C ) 1.1 × as long as antenna 1; peduncle 3th article reaching end of lateral cephalic lobe; 4th article as long as 2nd article of antenna 1; 5th article as long as 4th article; flagellum 0.7 × as long as peduncle 3 rd– 5th articles combined, composed of ten articles (terminal article rudimentary).

Upper lip ( Fig. 8D ) convex anteriorly, with notch in the middle, covered with minute setae.

Lower lip ( Fig. 8E ) inner lobe subovoid, outer lobe apex rounded, covered with minute setae, with one robust seta at mediodistal corner; mandibular process well developed.

Mandibles ( Fig. 8F, G ) with 4-dentate incisor, 4-dentate lacinia mobilis, and four raker setae on left mandible; with 5-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. 8H ) inner lobe small, without minute setae; outer lobe with eight dentate robust setae on apical margin; palp biarticulated, distal article curved, with four dentate setae on apical margin.

Maxilla 2 ( Fig. 8I ) inner lobe with an oblique row of plumose setae on surface; outer lobe longer and slightly dilated distally than inner lobe.

Maxilliped ( Fig. 9A ) inner lobe subrectangular, a little expanded distally, with three nodular setae apically and one medial nodular seta subdistally; outer lobe exceeding half of palp 2nd article, lined with seven 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 0.8 × as long as 3rd article, with elongate seta apically (as long as 4th article).

Gnathopod 1 ( Fig. 9B ) coxa subtrapezoidal, slightly extended distally, 0.7 × as wide as long; basis as long as coxa, anterior margin lateral border forming weak lobe distally, with three elongate setae subproximally, posterior margin with three elongate setae at the middle; carpus subtrapezoidal, 0.7 × as long as basis, half as wide as long, posterior lobe blunt; propodus as long and wide as carpus, rounded anteriorly, with minute serrations irregularly along palm and posterior margin, palm 0.6 × as long as posterior margin, defined by one robust seta medially; dactylus 0.7 × as long as propodus, exceeding palm, inner margin serrated, with two teeth.

Gnathopod 2 ( Fig. 9C ) stout, coxa subrectangular, 0.6 × as wide as long, slightly extended and rounded anterioventrally; basis anterior margin lateral borders forming well-developed lobe distally (sac-like lobe reaching middle of merus) bearing oblique stridulated ridges on surface; ischium with small anterior lobe only; merus subrectangular, 0.4 × as long as basis; carpus stout, anterior margin convex, carpal lobe well developed; propodus stout, as long as basis, 0.7 × as wide as long, slightly widened distally, palmar margin defined by one large blunt spine, with small obtuse spine near dactylus base and robust seta near defining spine, concave subrectangularly, bearing quadrate tooth medially; dactylus half as long as propodus, with two teeth on inner margin.

Pereopod 3 ( Fig. 9D, E ) coxa widened distally, produced anterioventrally, 0.8 × as wide as long, with stridulated ridges on medial surface and short stridulated ridges near the posterioventral corner on lateral surface submarginally; basis 0.4 × as wide as long, with three plumose setae along distal half of anterior margin, posterior margin expanded, evenly rounded, with two elongate setae at the middle, with a pair of plumose and minute setae at distal corner; merus 0.7 × as long as basis, anterior margin weakly expanded, with two plumose setae submarginally, distal corner somewhat produced, with one plumose seta subapically; carpus subrectangular, half as long as and 0.7 × as wide as merus; propodus slender, diminished distally, 0.6 × as long as basis; dactylus 0.4 × as long as propodus.

Pereopod 4 ( Fig. 9F ) coxa slightly widened distally, as long as that of pereopod 3, with stridulated ridges along anterioventral corner more oblique than that of female; basis 0.4 × as wide as long, with one plumose seta at the middle of anterior margin, posterior margin expanded, evenly rounded, with three elongate setae at the middle, with three plumose setae distally; merus 0.7 × as long as basis, anterior margin weakly expanded, distal corner somewhat produced; carpus half as long as and 0.7 × as wide as merus, propodus slender, diminished distally, 0.6 × as long as basis; dactylus 0.4 × as long as propodus.

Pereopod 5 ( Fig. 10A ) coxa bilobed, large, anterior lobe subovoid, 0.7 × as wide, expanded ventrally, posterior lobe small, expanded backwards; basis subovoid, broad, more expanded proximally, 0.8 × as wide as long; merus subrectangular, half as long as basis, half as wide as long; carpus subrectangular, as long and wide as merus; propodus 1.1 × as long as carpus, with a pair of distal locking setae unequal in length (longer seta 0.8 × as long as dactylus), with a group of four setae (longest seta 0.6 × as long as propodus) at anteriodistal corner; dactylus 0.4 × as long as propodus, armed with one accessory cusp on outer margin.

Pereopod 6 ( Fig. 10B, C ) 1.2 × as long as pereopod 5; coxa bilobed, anterior lobe small, posterior lobe weakly dilated posterioventrally; basis subovoid, 0.8 × as wide as long, anterior margin convex, posterior margin slightly dilated proximally; merus half as long as basis, 0.4 × as wide as long; carpus as long and 0.9 × as wide as merus; propodus 1.3 × as long as carpus, with one pair of distal locking setae unequal in length (longer seta 0.6 × as long as dactylus), with one group of five setae (longest seta half as long as propodus) at anteriodistal corner; dactylus 0.4 × as long as propodus, armed with one accessory cusp on outer margin.

Pereopod 7 ( Fig. 10D, E ) 1.2 × as long as pereopod 6; coxa unilobed, dilated posterioventrally; basis subovoid, 0.8 × as wide as that of pereopod 6, 0.7 × as wide as long, anterior margin rather convex, posterior margin with one blunt extension proximally; merus subrectangular, a little extended posteriodistally, 0.6 × as long as basis; carpus rectangular, 0.9 × as long as merus, 0.4 × as long as wide; propodus 1.6 × as long as carpus, with one pair of distal locking setae subequal (smaller than those of pereopods 5 and 6); dactylus 0.4 × as long as propodus, armed with one accessory cusp on outer margin.

Epimeron 1 slightly extended anterioventrally. Epimera 2 and 3 with each posterioventral corner produced backwards, but not acute ( Fig. 10F ).

Uropod 1 ( Fig. 10G ) peduncle without distoventral spine, but bearing small acute extension, with six dorsolateral and three dorsomedial robust setae; inner ramus 0.6 × as long as peduncle, with one subapical seta only; outer ramus 0.9 × as long as inner ramus, with three dorsolateral setae and one subapical seta.

Uropod 2 ( Fig. 10H ) 0.7 × as long as uropod 1; peduncle 0.6 × as long as that of uropod 1, with small acute extension distoventrally; inner ramus 0.9 × as long as peduncle, with two dorsomedial setae and one subapical seta; outer ramus 0.8 × as long as inner ramus, with two dorsolateral setae and one subapical seta.

Uropod 3 ( Fig. 10I ) 0.7 × as long as uropod 2; peduncle 0.8 × as long as that of uropod 2; outer ramus biarticular, 0.6 × as long as peduncle, last article vestigial, with two elongate setae subapically; inner ramus scale-like, 0.3 × as long as outer ramus.

Telson ( Fig. 10I ) subtriangular in dorsal view, with a pair of simple setae, a pair of sensory setae, and one nodular robust seta on each side.

Paratype female. Gnathopod 1 ( Fig. 11A ) not sexually dimorphic.

Gnathopod 2 ( Fig. 11B ) stouter than female gnathopod 1, slightly smaller than that of male; coxa subrectangular, 1.5 × as long as wide, evenly rounded anterioventrally, oostegite 1.2 × as long as basis, 2.9 × as long as wide; basis anterior margin lateral borders forming lobe distally, but smaller than that of male (not exceeding ischium), without stridulated ridges on surface; ischium with small anterior lobe only; merus rectangular, 0.4 × as long as basis; carpus stout, anterior margin convex, carpal lobe well developed; propodus stout, 0.8 × as long as basis, 0.7 × as wide as long, not widened distally, palmar margin cavity subquadrate, bearing one quadrate tooth medially, proximal and defining spines weaker than those of male, with one robust defining seta medially; dactylus half as long as propodus, inner margin minutely serrated, with three teeth.

Pereopod 3 ( Fig. 11C ) not sexually dimorphic except for the absence of both medial and lateral stridulated ridges on coxa; oostegite 1.5 × as long as that of gnathopod 2.

Pereopod 4 ( Fig. 11D ) coxa without stridulated ridges at anterioventral corner, basis posterior margin more expanded distally, with twelve plumose setae along distal half.

Pereopod 5 oostegite ( Fig. 11E ) half as long as that of pereopod 4.

Remarks.

Photis bronca sp. nov. has been misidentified as Photis longicaudata (Spence Bate & Westwood, 1862) in the Far East including Korea ( Kim et al. 2005), Japan ( Nagata 1965; Hirayama 1984), and China ( Ren 1992, 2000, 2006). The authors re-examined the syntype series of P. longicaudata deposited at the Natural History Museum, London (NHMUK 1911.20899-20906; Figs 12 , 13 ) and several specimens, which were collected from the North Sea, at the Museum für Naturkunde Berlin (ZMB 11656) to confirm the validity of P. longicaudata in Korean waters. As a result, the material formerly identified as P. longicaudata from Japan and China, as well as the Korean material, is herein described as a new species based on the following differences when compared with the newly designated P. longicaudata lectotype (NHMUK 1911.20899; Fig. 12 ): gnathopod 1 palmar margin has a robust defining seta medially in both sexes (absent in the P. longicaudata lectotype); gnathopod 2 palmar margin has a quadrate tooth medially in both sexes (obviously absent in the P. longicaudata lectotype); the sac-like lobe of male gnathopod 2 basis is much larger than that of P. longicaudata (slightly exceeding the ischium in the P. longicaudata lectotype); the anterior margin of male gnathopod 2 propodus is a little rounded (slightly shorter and more swollen in the P. longicaudata lectotype); the palmar margin of male gnathopod 2 propodus has more produced spines (slightly produced in the P. longicaudata lectotype); male pereopod 3 coxa has a different pattern of stridulated ridges; the male pereopod 4 coxa has stridulated ridges on the anterior half of the ventral margin (absent in the P. longicaudata lectotype); and female gnathopod 2 palmar margin is concave subrectangularly (more oblique and recessed in the P. longicaudata lectotype) ( Bate and Westwood 1863; Sars 1895; Nagata 1965; Hirayama 1984; Ren 1992, 2000, 2006; Kim et al. 2005; see Figs 12 , 13 ).

It is well known that both Photis aina JL Barnard, 1970 and Photis kapapa JL Barnard, 1970 from the Hawaiian Islands have affinities with P. longicaudata in that gnathopod 2 has very well-developed (sac-like) anterior lobe of the basis (JL Barnard 1970). Among them, Photis bronca sp. nov. differs from P. aina , regarding the eyes being in the middle of the cephalic lobe (occupying the end of the cephalic lobe in P. aina ), lacking the defining seta on the palmar margin of male gnathopod 1 (with one robust seta medially in P. aina ), lacking posterioventral notches of epimera 2 and 3, and a shorter inner ramus of uropod 2 (about half length in P. aina ) ( Barnard 1970; Myers 1985, 2009). Photis bronca sp. nov. can be distinguished from P. kapapa by the following differences: the eyes occupying at the middle of the cephalic lobe (at the end of the cephalic lobe in P. kapapa ), lacking stridulated ridges in both posterior margins of the coxae of gnathopods 1 and 2, 0.7 times as wide as long male gnathopod 2 (0.8 times in P. kapapa ), the female palmar margin of gnathopod 2 with a small obtuse spine near the dactylus base (without spine in P. kapapa ), the presence of one accessory cusp on pereopod 5 dactylus (two accessory cusps in P. kapapa ), subacutely produced posterior margin of epimeron 3 (rounded in P. kapapa ), and uropod 3 outer ramus with the length of 0.6 times as long as the peduncle (0.9 times in P. kapapa ) ( Barnard 1970; Ren 2006).

Photis bronca sp. nov. resembles Photis davei Myers, 2009 in the shapes of elongate propodus of pereopods 3 and 4 as well as the outlines of gnathopods in both sexes, but the former differs from the latter in the presence of a well-developed sac-like lateral lobe on the basis of male gnathopod 2 (present but very weak in P. davei ) and not-elongate rami of uropods 1 and 2 ( Myers 2009).

Photis fischmanni Gurjanova, 1951 also has a similar gnathopod 2 shape in both sexes, but P. bronca sp. nov. is clearly different from this species by elongate antenna 1 and 2 (0.4 times as long as the body in P. bronca sp. nov., but less than 0.3 times in P. fischmanni ), less expanded carpus and propodus of gnathopod 1, and less setose appendages than P. fischmanni ( Gurjanova 1951, 1955; Conlan 1983).

This new species differs from Photis paeowai Myers, 1995 and Photis pirloti Myers, 1985 by bearing a well-developed sac-like lateral lobe on the basis of male gnathopod 2 (present but rather weak in P. paeowai and P. pirloti ) and a quadrate medial tooth on the palmar margin of gnathopod 2 in both sexes (absent in P. paeowai and P. pirloti ) ( Myers 1985, 1995).

Figures

Figure 8. Photis bronca sp. nov., holotype, NIBRIV 0000848472, male, 5.8 mm, Daryeo-do Island, South Korea. A habitus B antenna 1 C antenna 2 D upper lip E lower lip F left mandible G right mandible H maxilla 1 I maxilla 2. Scale bars: 0.1 mm (D-I), 0.2 mm (B, C), 0.5 mm (A).

Figure 9. Photis bronca sp. nov., holotype, NIBRIV 0000848472, male, 5.8 mm, Daryeo-do Island, South Korea. A maxilliped B gnathopod 1 C gnathopod 2 D pereopod 3 E coxa of pereopod 3 F pereopod 4. Scale bars: 0.1 mm (A), 0.2 mm (B-F).

Figure 10. Photis bronca sp. nov., holotype, NIBRIV 0000848472, male, 5.8 mm, Daryeo-do Island, South Korea. A pereopod 5 B, pereopod 6 C dactylus of pereopod 6 D coxa of pereopod 7 E pereopod 7 F uropod 1 G uropod 2 H uropod 3 and telson. Scale bars: 0.1 mm (C, E, G-I), 0.2 mm (A, B, D, F).

Figure 11. Photis bronca sp. nov., paratype, NIBRIV 0000848473, female, 5.3 mm, Daryeo-do Island, South Korea. A gnathopod 1 B gnathopod 2 C coxa and oostegite of pereopod 3 D pereopod 4 E oostegite of pereopod 5. Scale bars: 0.2 mm.

Figure 12. Photis longicaudata (Spence Bate & Westwood, 1862), lectotype, NHMUK 1911.20899, male. 3.2 mm, Shetland Islands, UK. A gnathopod 1 B gnathopod 2 C coxa of pereopod 3 D coxa of pereopod 4. Scale bars: 0.1 mm.

Figure 13. Photis longicaudata (Spence Bate & Westwood, 1862), paralectotype, NHMUK 1911.20890 - 20896, females. 5.3 mm (A, B) and 3.4 mm (C, D), Shetland Islands, UK A gnathopod 1 B gnathopod 2 C gnathopod 1 D gnathopod 2. Scale bars: 0.1 mm.