Exiliphotis petila, 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

Exiliphotis petila sp. nov. Figs 1 , 2 , 3

Etymology.

The epithet of the specific name, petila, is originated from the Latin word petilus. This name refers to the shape of pereopod 5 coxa and basis, and pereopods 6 and 7 basis, which are slenderer than those of other photid amphipods.

Material examined.

Holotype: ♂ (3.7 mm), NIBRIV0000806532. Daegwantal-do Island, Jeju-do, South Korea (33°43'38"N, 126°20'13"E), 21 Nov 2012, grab sampler (about 36 m depth), by Prof. HY Soh.

Description.

Holotype male. Head ( Fig. 1A ) 0.9 × as long as pereonites 1-3 combined; lateral cephalic lobe produced anteriorly, apex rounded; eye circular, large, occupying most of lateral cephalic lobe; antennal sinus deep.

Antenna 1 ( Fig. 1B, C ) 0.7 × as long as body; peduncle 1st article stout, 0.7 × as long as head; without robust seta posteriodistally; 2nd article 2.0 × as long as 1st article; 3rd article 0.8 × as long as 2nd article; accessory flagellum uniarticulated, vestigial; flagellum 2.0 × as long as peduncle 3rd article, composed of nine articles (terminal article rudimentary).

Antenna 2 ( Fig. 1D ) 1.1 × as long as antenna 1; peduncle 4th article 0.7 × as long as 2nd article of antenna 1; 5th article as long as 4th article; flagellum 1.9 × as long as peduncle 5th article, composed of ten articles (terminal article rudimentary).

Upper lip ( Fig. 1E ) convex anteriorly, with notch in the middle, covered with minute setae.

Lower lip ( Fig. 1F ) inner lobe subovoid, outer lobe apex rounded, covered with minute setae; mandibular process well developed.

Mandibles ( Fig. 1 G–I ) with 1/2 and 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. 2A ) inner lobe small, without seta; outer lobe with ten dentate setae on apical margin; palp biarticulated, 2nd article slightly dilated distally, with five dentate setae apically and five simple setae subapically.

Maxilla 2 ( Fig. 2B ) inner lobe with an oblique row of five weakly plumose setae on surface; outer lobe lager than inner lobe, expanded distally.

Maxilliped ( Fig. 2C ) inner lobe subrectangular, with three nodular setae apically and one medial nodular seta subdistally; outer lobe semiovoid, apex beyond half of 2nd palp article, lined with ten stout setae on medial to apical margins; palp composed of four articles, 3rd article a little 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. 2D ) coxa subtrapezoidal, 0.7 × as wide as long, slightly produced anterioventrally; basis subtrapezoidal, anterior margin distal lobe weakly developed, with four elongate setae in the middle, posterior margin convex subproximally, with seven setae; carpus broad, 2.0 × as long as wide, 0.8 × as long as basis, with carpal lobe broad and blunt; propodus as long and as wide as carpus, anterior margin evenly rounded, with five oblique rows of elongate setae submarginally, posterior margin more convex than anterior margin, free form carpal lobe proximally, palmar margin convex, finely serrated on distal 3/4 margin, not defined distinctively, with one robust seta medially at 1/3 length distally; dactylus elongate, 0.8 × as long as propodus, inner margin finely serrated, with four teeth.

Gnathopod 2 ( Fig. 2E, F ) subequal to gnathopod 1; coxa subtrapezoidal, 1.1 × as wide as that of gnathopod 1, 0.7 × as wide as long, rounded ventrally, not produced anterioventrally; coxal gill subovoid, 0.9 × as long as coxa; basis similar to that of gnathopod 1, without setae on anterior margin; carpus 0.7 × as long as basis and that of gnathopod 1, carpal lobe also shorter than that of gnathopod 1, blunt posteriorly; propodus as long as basis, 1.6 × as long as carpus, anterior margin evenly rounded, posterior margin convex, not free from carpal lobe proximally, finely serrated on distal half margin, palmar margin oblique, strongly bisinuated, finely serrated, defined by one robust seta medially; dactylus 0.7 × as long as propodus, exceeding palm, inner margin finely serrated, with three teeth.

Pereopod 3 ( Fig. 2G ) coxa as wide but 0.9 × as long as that of gnathopod 2, rounded ventrally, weakly produced anterioventrally, coxal gill subovoid, 1.1 × as long as that of gnathopod 2; basis 1.4 × as long as coxa, 0.3 × as wide as long, posterior margin convex, with elongate setae; merus 0.6 × as long as basis, 0.5 × as wide as long, slightly lobate anteriodistally; carpus subrectangular, 0.9 × as long as merus, slightly convex anteriorly; propodus tapering distally, 0.8 × as long as basis; dactylus 0.4 × as long as propodus.

Pereopod 4 ( Fig. 3A ) similar to pereopod 3.

Pereopod 5 ( Fig. 3B ) slender; coxa bilobed, as long and 1.5 × as wide as that of pereopod 4, anterior lobe expanded downward, 0.9 × as wide as basis, rounded ventrally, posterior lobe expanded backwards, slightly smaller than anterior lobe; basis subovoid, 1.3 × as wide as that of pereopod 4, half as wide as long, slightly wider proximally, posterior margin with one elongate seta and notched distally; merus and carpus not lobate, half as long as basis, with elongate setae at posteriodistal corners; propodus 1.5 × as long as carpus, anterior margin with two robust setae and one pair of locking setae unequal in length; dactylus 0.4 × as long as propodus, armed with one accessory cusp on outer margin.

Pereopod 6 ( Fig. 3C ) subequal to pereopod 5 except for coxa; coxa bilobed, anterior lobe small, posterior lobe as large as that of pereopod 4; basis subrectangular, as long and wide as that of pereopod 5, slightly wider proximally; merus and carpus not lobate, each 0.6 × and 0.9 × as long as basis, with elongate setae at posteriodistal corners; propodus 1.6 × as long as carpus, anterior margin with simple setae and a pair of locking setae unequal in length; dactylus 0.4 × as long as propodus, armed with one accessory cusp on outer margin.

Pereopod 7 ( Fig. 3D ) 1.3 × as long as pereopod 6, slender; coxa unilobed, rounded ventrally, slightly dilated posterioventrally; basis subrectangular, as wide and 1.2 × as long as that of pereopod 6, 0.4 × as wide as long; merus slender, 0.8 × as long as basis slightly lobate posteriodistally; carpus not lobate, 0.7 × as long as merus; propodus 1.9 × as long as carpus, slightly curved, anterior margin with simple setae and a pair of locking setae unequal in length; dactylus 0.4 × as long as propodus, armed with one accessory cusp on outer margin.

Epimera 2-3 ( Fig. 1A ) subrectangular, rounded ventrally.

Uropod 1 ( Fig. 3E ) peduncle without distoventral spine, with five dorsolateral and three dorsomedial robust setae; outer ramus 0.6 × as long as peduncle, with five dorsolateral robust setae, terminated by rounded apex bearing one robust seta; inner ramus as long as outer ramus, without marginal setae, terminated by rounded apex bearing one robust and one simple seta.

Uropod 2 ( Fig. 3F ) 0.7 × as long as uropod 1; peduncle without distoventral spine, 0.6 × as long as that of uropod 1, with one dorsomedial and two dorsolateral robust setae; outer ramus 0.9 × as long as peduncle, with four dorsolateral robust setae, terminated by rounded apex bearing one robust and one simple seta; inner ramus as long as outer ramus, without marginal setae, terminated by rounded apex bearing one robust seta.

Uropod 3 ( Fig. 3G, H ) 0.7 × as long as uropod 2; peduncle 0.7 × as long as that of uropod 2; inner ramus half as long as outer ramus, diminished distally, with minute apical seta; outer ramus as long as peduncle, biarticulated, 2nd article vestigial, with two elongate setae subapically.

Telson ( Fig. 3G, H ) trapezoidal in dorsal view, 2.1 × as wide as long, distal margin not acute, with one terminal spine, one simple seta, and two sensory setae on each side.

Remarks.

See the remarks section under the genus.

Figures

Figure 1. Exiliphotis petila sp. nov., holotype, NIBRIV 0000806532, male, 3.7 mm, Daegwantal-do Island, South Korea. A habitus B, C antenna 1 D antenna 2 E upper lip F lower lip G, H left mandible I right mandible. Scale bars: 0.05 mm (G-I), 0.1 mm (C, E, F), 0.2 mm (B, D), 0.5 mm (A).

Figure 2. Exiliphotis petila sp. nov., holotype, NIBRIV 0000806532, male, 3.7 mm, Daegwantal-do Island, South Korea. A maxilla 1 B maxilla 2 C maxilliped D gnathopod 1 E, F gnathopod 2 G pereopod 3. Scale bars: 0.05 mm (A, B), 0.1 mm (C-G).

Figure 3. Exiliphotis petila sp. nov., holotype, NIBRIV 0000806532, male. 3.7 mm, Daegwantal-do Island, South Korea. A pereopod 4 B pereopod 5 C pereopod 6 D pereopod 7 E uropod 1 F uropod 2 G, H uropod 3 and telson, dorsal (G) and lateral (H). Scale bars: 0.1 mm (E-H), 0.2 mm (A-D).