Podoceropsis pseudoclavapes, 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

Podoceropsis pseudoclavapes sp. nov. Figs 24 , 25 , 26 , 27

Etymology.

The composite epithet of the specific name, pseudoclavapes, is a combination of the Greek word pseudos, and the specific name of Podoceropsis clavapes Jung, Choi, Kim & Yoon, 2017. This name refers to the similarity of this new species to P. clavapes .

Material examined.

Holotype: ♂ (3.2 mm), NIBRIV0000806530. Bigin-do Island, Gyeongsangnam-do, South Korea (34°42'52"N, 128°27'04"E), 18 Oct 2014, Scuba diving (about 20 m depth), by TW Jung. Paratypes: 1 ♂ (2.0 mm) and 3 ♀♀ (ovigerous; 2.1-2.7 mm), NIBRIV0000807157. Same data as holotype.

Diagnosis.

Gnathopod 1 carpus elongate, 0.9 × as long as basis; dactylus as long as propodus. Gnathopod 2 propodus extremely stout, elongate ovoid, 1.2 × as long as basis, half as wide as long, posterior margin with short undulate border distally, palm defined by rounded protrusion, with excavation successively posteriodistally and subquadrate protrusion bearing minutely serrated margin near dactyl base; dactylus stout, 0.4 × as long as propodus, falcate, but apex quite obtuse. Pereopods 3 and 4 merus expanded, half as wide as long. Pereopod 5 basis posterior margin sinuated distally. Pereopod 5 basis posterior margin with additional lobe, but not produced distally. Uropod 3 rami subequal in length, 0.8 × as long as peduncle.

Description.

Holotype male. Head ( Fig. 24A ) lateral cephalic lobe subtriangular; eye subcircular, large, occupying most of lateral cephalic lobe; antennal sinus deep.

Antenna 1 ( Fig. 24 B–D ) peduncle 1st article stout, with one robust seta at posteriodistal corner; 2nd article 1.3 × as long as 1st article; 3rd article 0.7 × as long as 2nd article; accessory flagellum uniarticulated, vestigial; flagellum as long as peduncle 1 st– 3rd articles combined, composed of ten articles (terminal article rudimentary).

Antenna 2 ( Fig. 24E ) 1.1 × as long as antenna 1; peduncle 4th, 5th articles 0.9 × as long as 2nd article of antenna; flagellum as long as peduncle 3 rd– 5th articles combined, composed of twelve articles (terminal article rudimentary).

Upper lip ( Fig. 24F ) convex anteriorly, with notch in the middle, covered with minute setae.

Lower lip ( Fig. 24G ) inner lobe subovoid, outer lobe apex rounded, covered with minute setae; mandibular process well developed.

Mandibles ( Fig. 24H, I ) with 4-dentate incisor, 4-dentate lacinia mobilis, and four raker setae on left mandible; with 5-dentate incisor, 5-dentate lacinia mobilis, and five raker setae on right mandible; molar well developed, triturative; 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. 24J ) inner lobe small, produced distally, without setae; outer lobe with ten dentate robust setae on apical margin; palp biarticulated, distal article curved, a little swollen, with five setae on apical margin.

Maxilliped ( Fig. 24K, L ) inner lobe subrectangular, expanded distally, with three nodular setae apically and one medial nodular seta subdistally; outer lobe reaching 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, 0.4 × as long as 2nd article, 4th article 0.8 × as long as 3rd article, with elongate seta apically (1.1 × as long as 4th article).

Gnathopod 1 ( Fig. 25A ) coxa rhomboid, produced anterioventrally, as long as wide, without setae on ventral margin; basis subtrapezoidal, 1.8 × as long as coxa, scarcely setose, anterior margin lateral border lobate distally, posterior margin rather convex; carpus elongate, 0.9 × as long as basis, 0.3 × as wide as long, weakly widened distally, carpal lobe not developed; propodus 0.6 × as long as carpus, rounded anteriorly, palm indistinct; dactylus elongate, as long as propodus, with three teeth on inner margin.

Gnathopod 2 ( Fig. 25B, C ) extremely stout, coxa subrhomboid, 1.4 × as wide as long, convex anterioventrally, ventral margin slightly sinuous, with six setae; basis subtrapezoidal, 2.2 × as long as coxa, anterior margin both lateral and medial borders forming lobes distally, but that of lateral obliquely truncated and more produced distally; ischium anterior margin with both lateral and medial lobes, medial lobe more developed; carpal lobe weakly developed; propodus extremely stout, elongate ovoid, 1.2 × as long as basis, half as wide as long, anterior margin convex, slightly widened in proximal 2/3 margin, remaining distal 1/3 margin and dactylus forming smooth ellipse together, posterior margin with short undulate border distally, palm defined by rounded protrusion, with excavation successively posteriodistally and subquadrate protrusion bearing minutely serrated margin near dactylus base; dactylus stout, 0.4 × as long as propodus, falcate, but apex quite obtuse.

Pereopod 3 ( Fig. 25D, E ) coxa subquadrate, with rounded corners; basis subtrapezoidal, somewhat expanded posteriorly, 0.4 × as wide as long; merus as wide as basis, anterior margin extremely expanded, produced distal corner exceeding half of carpus; carpus short, 0.2 × as long as basis; propodus diminished distally, half as long as basis; dactylus half as long as propodus.

Pereopod 4 ( Fig. 25F, G ) coxa 1.2 × wider proximally than that of pereopod 3; other articles subequal to those of pereopod 3.

Pereopod 5 ( Fig. 26A, B ) coxa bilobed, anterior lobe rounded and expanded ventrally, 0.9 × as wide as basis, posterior lobe narrow, extended backwards, with one robust and one simple seta; basis subovoid, 0.6 × as wide as long, anterior margin more swollen proximally, posterior margin crenulated, lined with simple setae only, sinuated (notched) distally; merus widened distally, twisted, half as long as basis; carpus subrectangular, 0.7 × as wide as long; propodus slightly plump, 1.3 × as long as carpus, a pair of distal locking setae unequal in length (longer seta exceeding dactylus); dactylus falcate.

Pereopod 6 ( Fig. 26C ) 1.5 × as long as pereopod 5; coxa bilobed, anterior lobe expanded ventrally, smaller than that of pereopod 5, with two simple setae anteriorly, posterior lobe slightly larger than anterior lobe, weakly dilated posterioventrally; basis subovoid, half as wide as long, with simple setae only, anterior margin convex, posterior margin scarcely crenulated, slightly expanded but flatter than anterior margin, bearing small notch distally; merus 0.6 × as long as basis, 0.4 × as wide as long, posterior margin expanded distally, with elongate robust setae (longest seta 0.3 × as long as merus); carpus subrectangular, slightly widened distally, 0.7 × as long as merus, half as wide as long; propodus linear, 2.0 × as long as carpus, with a pair of unequal locking setae; dactylus stout, falcate, 0.3 × as long as propodus.

Epimera 1-3 ( Fig. 26D ) each with a notch bearing minute seta on posterioventral corner, convex ventrally.

Uropod 1 ( Fig. 26F ) peduncle with distoventral spine 0.2 × as long as peduncle, with four dorsomedial and nine dorsolateral robust setae; inner ramus 0.7 × as long as peduncle, with two dorsomedial robust setae and one group of four robust setae on apex; outer ramus 0.9 × as long as inner ramus, with two dorsolateral robust setae and one group of four robust setae on apex.

Uropod 2 ( Fig. 26G ) 0.7 × as long as uropod 1; peduncle 0.6 × as long as that of uropod 1, both dorsal margins with distal robust seta only; inner ramus 1.2 × as long as peduncle, with 3 dorsomedial robust setae and one group of four robust setae on apex; outer ramus 0.7 × as long as inner ramus, diminished distally, terminated by subacute-end bearing one robust seta.

Uropod 3 ( Fig. 26H ) 0.4 × as long as uropod 1; peduncle 0.8 × as long as that of uropod 2; inner ramus 0.8 × as long as peduncle, diminished distally, with one robust seta on dorsomedial margin, terminated by one robust seta; outer ramus as long as inner ramus.

Telson ( Fig. 26I, J ) subtrapezoidal in dorsal view, slightly produced in apex, margins rounded, with a pair of robust setae on each side.

Paratype female. Maxilla 2 ( Fig. 27B ) inner lobe with an oblique row of plumose setae on surface; outer lobe slightly longer than inner lobe.

Gnathopod 1 ( Fig. 27C ) not sexually dimorphic between both sexes.

Gnathopod 2 ( Fig. 27D ) as long as but stouter than female gnathopod 1, coxa subrhomboid, slightly produced anterioventrally, as long as wide, evenly rounded ventrally, oostegite broad, 1.3 × as long as basis; basis anterior margin lateral borders forming lobe distally, but less produced distally than that of male; ischium with small anterior lobe only; merus rectangular, 0.4 × as long as basis; carpus stout, anterior margin convex, carpal lobe weak; propodus stout, slightly elongate, 0.8 × as long as basis, half as wide as long, palmar obliquely excavated, margin irregularly wrinkly, bearing one blunt spine medially,; dactylus half as long as propodus, inner margin minutely serrated, with one tooth.

Pereopod 5 ( Fig. 27E ) basis posterior margin not sinuated and without excavation distally.

Remarks.

Podoceropsis clavapes Jung, Choi, Kim & Yoon, 2017, which is the only known Podoceropsis species from Korean waters, is characterized by its peculiarly shaped gnathopod 2 in mature males: the propodus is markedly stout and enlarged (1.4 times as long as basis), the palmar margin has one proximal cavity and two distal protrusions, and the dactylus is stout and 0.8 times as long as the propodus ( Jung et al. 2017). Podoceropsis pseudoclavapes sp. nov. has a similar shape of gnathopod 2 propodus in males to that of P. clavapes , but notably differs by gnathopod 1 propodus, which is half as long as the carpus (0.8 times as long as carpus in P. clavapes ), the palmar margin of gnathopod 2, which has one rectangular protrusion and one distal cavity (one proximal cavity and two distal protrusions in P. clavapes ), gnathopod 2 dactylus, which is 0.4 times as long as the propodus (0.8 times as long as propodus in P. clavapes ), the merus of pereopods 3 and 4, which are half as wide as long (0.4 times as wide as long in P. clavapes ), the posterior margin of pereopod 5 basis, which has an additional lobe, but it is not produced distally (also with lobes but differently produced distally in P. clavapes ), and both rami of uropod 3, which are subequal in length and 0.9 times as long as the peduncle (inner ramus is 0.9 times as long as outer ramus and 0.7 times as long as peduncle in P. clavapes ) ( Jung et al. 2017).

Podoceropsis angustimana Conlan, 1983 also has a markedly stout and enlarged propodus and a similar excavation of the palmar margin of male gnathopod 2, but P. pseudoclavapes sp. nov. can be distinguished by the following differences: the propodus is half as long as the carpus (exceeding half the length in P. angustimana ); pereopods 3 and 4 are widened; the posterior margin of pereopod 5 basis is lobed but not distally produced (posterior margin is slightly oblique and distally produced in P. angustimana ); and uropod 3 rami are shorter than the peduncle (1.3 times as long as peduncle in P. angustimana ) ( Conlan 1983).

Figures

Figure 24. Podoceropsis pseudoclavapes sp. nov., holotype, NIBRIV 0000806530, male, 3.2 mm, Bigin-do Island, South Korea. A head B-D antenna 1 E antenna 2 F upper lip G lower lip H right mandible I left mandible J maxilla 1 K, L maxilliped. Scale bars: 0.02 mm (D), 0.05 mm (F-L), 0.1 mm (A-C, E).

Figure 25. Podoceropsis pseudoclavapes sp. nov., holotype, NIBRIV 0000806530, male, 3.2 mm, Bigin-do Island, South Korea. A gnathopod 1 B gnathopod 2 C palmer margin of gnathopod 2 D coxa 3 E pereopod 3 F coxa 4 G pereopod 4. Scale bars: 0.01 mm (C) 0.1 mm (A, B, D-G).

Figure 26. Podoceropsis pseudoclavapes sp. nov., holotype, NIBRIV 0000806530, male, 3.2 mm, Bigin-do Island, South Korea. A coxa 5 B pereopod 5 C pereopod 6 D pleonal epimera E pleopod 2 F uropod 1 G uropod 2 H uropod 3 I telson J uropod 3 and telson, lateral. Scale bars: 0.05 mm (F-J), 0.1 mm (A-C, E), 0.2 mm (D).

Figure 27. Podoceropsis pseudoclavapes sp. nov., paratype, NIBRIV 0000807157, female, 2.5 mm, Bigin-do Island, South Korea. A habitus B maxilla 2 C gnathopod 1 D gnathopod 2 E pereopod 5. Scale bars: 0.05 mm (B), 0.5 mm (A, C-E).