Latigammaropsis careocavata, 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

Latigammaropsis careocavata sp. nov. Figs 4 , 5 , 6 , 7

Etymology.

The composite epithet of the specific name, careocavata, is a combination of the Latin words careo and cavatus, meaning lacking excavation. This name refers to the shape of the palmar margin of gnathopod 2 in both sexes.

Material examined.

Holotype: ♂ (7.5 mm), NIBRIV0000806529. Sogueulbi-do Island, Gyeongsangnam-do, South Korea (34°34.571'N, 128°32.566'E), 7 May 2012, grab sampler (about 60 m depth), by Prof. HY Soh. Paratypes: 2 ♂♂ (4.5 and 4.8 mm), 3 ♀♀ (5.5-6.7 mm), NIBRIV0000848929. Same data as holotype.

Diagnosis.

Gnathopod 2 stout in both sexes (similar in shape), but basis and propodus less setose anteriorly in females; propodus palmar margin oblique, slightly convex, serrated, without excavations, defined by a single stout spine and defining seta elongate, longer in males.

Description.

Holotype male. Head ( Fig. 4B ) lateral cephalic lobe weakly produced anteriorly; eye lageniform, large; antennal sinus deep.

Antenna 1 ( Fig. 4C, D ) 0.6 × as long as body; peduncle 1st article stout, 0.7 × as long as head, with one robust seta posteriodistally; 2nd article 1.3 × as long as 1st article; 3rd article 0.7 × as long as 2nd article; accessory flagellum as long as peduncle 3rd article, composed of five articles (terminal article rudimentary); flagellum 0.9 × as long as peduncle 1 st– 3rd articles combined, composed of twelve articles (terminal article rudimentary).

Antenna 2 ( Fig. 4E, F ) as long as antenna 1; peduncle 4th, 5th articles 0.9 × as long as 2nd article of antenna 1; flagellum 1.4 × as long as peduncle 5th article, composed of ten articles (terminal article rudimentary).

Upper lip ( Fig. 4G ) convex anteriorly, covered with minute setae.

Lower lip ( Fig. 4H ) inner lobe subovoid, outer lobe apex rounded, covered with minute setae; mandibular process well developed.

Mandibles ( Fig. 4I, J ) with 4-dentate incisor, 4-dentate lacinia mobilis, and eight raker setae on left mandible; with 5-dentate incisor and minutely dentate lacinia mobilis 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. 4K, L ) inner lobe small, subrectangular, produced laterodistally, with seven plumose setae; outer lobe nine dentate robust setae on apical margin; palp 2nd article slightly swollen laterally, apex with six dentate robust setae.

Maxilla 2 ( Fig. 4M ) inner lobe with an oblique row of plumose setae on surface; outer lobe slightly larger than inner lobe.

Maxilliped ( Fig. 5A, B ) inner lobe subrectangular, with three dentate robust setae apically and one medial robust seta subdistally; outer lobe semiovoid, apex beyond half of 2nd palp article, lined with eight robust 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 0.4 × as long as 3rd article, with elongate seta apically (1.3 × as long as 4th article).

Gnathopod 1 ( Fig. 5C ) setose with elongate setae; coxa subrhomboid, 0.9 × as wide as long, weakly produced anterioventrally, rounded ventrally; basis subtrapezoidal, swollen posteriodistally; carpus subtrapezoidal, 0.9 × as long as basis, half as wide as long, with carpal lobe blunt; propodus subovoid, as long and wide as carpus, palm oblique, slightly convex, minutely serrated, not defined distinctively, with one robust seta medially; dactylus elongate, 0.7 × as long as propodus, inner margin minutely serrated, with five teeth.

Gnathopod 2 ( Fig. 5D ) stout, 1.3 × as long gnathopod 1, densely setose with elongate setae; coxa subrhomboid, as long as wide; basis subtrapezoidal, half as wide as long, anterior margin with lateral and medial borders forming weak lobes distally, posterior margin swollen; carpus 0.7 × as long as basis, with carpal lobe not free from propodus posterior margin; propodus 1.3 × as long as basis, 0.6 × as wide as long, anterior and posterior margins subparallel, palmar margin oblique, half as long as posterior margin, slightly convex, weakly serrated, without excavation, defined by one stout spine, with one elongate robust seta medially; dactylus fitting palm.

Pereopod 3 ( Fig. 5E ) rarely setose than gnathopods; coxa subquadrate, 0.9 × as long as that of gnathopod 2; basis expanded, 0.7 × as wide as coxa, posterior margin more swollen in the middle, along with elongate setae; merus 0.4 × as long as basis, expanded anteriodistally, half as wide as long; carpus as long as merus, not expanded; propodus half as long as basis, diminished distally; dactylus falcate, 1.2 × as long as propodus.

Pereopod 4 ( Fig. 5F ) similar to pereopod 3, except for longer merus (half as long as basis).

Pereopod 5 ( Fig. 6A ) coxa bilobed, anterior lobe larger than posterior lobe, expanded and rounded ventrally; basis as wide as coxa anterior lobe, 0.8 × as wide as long, anterior margin convex, posterior margin extremely expanded proximally, merus 0.6 × as long as basis, slightly expanded anteriodistally; carpus subrectangular, 0.9 × as long as merus, half as wide as long; propodus 1.3 × as long as carpus, with three robust setae on posterior margin, with one pair of distal locking setae extremely unequal in length; dactylus 0.4 × as long as propodus.

Pereopod 6 ( Fig. 6B, C ) 1.3 × as long as pereopod 5; coxa 0.7 × as wide as that of pereopod 5; bilobed, anterior lobe expanded downwards, posterior lobe as large as anterior lobe, expanded posterioventrally; basis subovoid, anterior margin evenly rounded, posterior margin expanded proximally, 0.6 × as wide as long; merus slightly expanded distally, 0.4 × as wide as long, 0.6 × as long as basis; carpus rectangular, 0.9 × as long as merus, 0.3 × as wide as long; propodus 1.5 × as long as carpus, with a pair of distal locking setae unequal in length, with a group of five setae (longest seta 0.7 × as long as propodus) at anteriodistal corner; dactylus falcate, 0.4 × as long as propodus.

Pereopod 7 ( Fig. 6D ) similar and 1.2 × as long as pereopod 6; coxa unilobed, as wide as that of pereopod 6; slightly expanded posterioventrally; basis subovoid, as wide and 1.1 × as long as that of pereopod 6, anterior margin evenly rounded, posterior margin expanded proximally; merus slightly expanded distally, 0.3 × as wide as long, 0.6 × as long as basis; carpus rectangular, as long as merus, 0.3 × as wide as long; propodus 1.4 × as long as carpus, with a pair of distal locking setae unequal in length at anteriodistal corner; dactylus falcate, 0.4 × as long as propodus.

Epimera 1-3 each with a small notch bearing minute seta at posterioventral corner. Epimeron 1 rounded ventrally. Epimera 2 and 3 subrectangular ( Fig. 6E ).

Uropod 1 ( Fig. 6F ) peduncle with a well-developed distoventral spine, 0.7 × as long as peduncle, with four dorsomedial and four dorsolateral robust setae on distal half margin; outer ramus 0.8 × as long as peduncle, with three dorsolateral and two dorsomedial robust setae, apex blunt bearing one group of robust setae; inner ramus 0.9 × as long as peduncle, with two dorsolateral and six dorsomedial robust setae, apex blunt bearing one group of robust setae.

Uropod 2 ( Fig. 6G ) 0.7 × as long as uropod 1; peduncle 0.6 × as long as that of uropod 1, without distoventral spine, with one dorsomedial and two dorsolateral robust setae distally; outer ramus 1.1 × as long as peduncle, with three dorsolateral and four dorsomedial robust setae, apex blunt bearing one group of robust setae; inner ramus 1.3 × as long as peduncle, with five dorsolateral and eight dorsomedial robust setae, apex blunt bearing one group of robust setae.

Uropod 3 ( Fig. 6H ) 0.7 × as long as uropod 2; peduncle 0.8 × as long as that of uropod 2, with two robust setae distally; outer ramus as long as peduncle, biarticulated, 2nd article vestigial, with two elongate setae subdistally; inner ramus 0.9 × as long as peduncle, plump proximally but tapering distally.

Telson ( Fig. 6I ) subtrapezoidal in dorsal view, apex acute, with one robust seta on each side.

Paratype female. Gnathopod 1 ( Fig. 7A ) not sexually dimorphic between both sexes.

Gnathopod 2 ( Fig. 7B ) similar to that of holotype male in size, less setose anteriorly; basis posterior margin less swollen; palm defining robust seta smaller than that of holotype male.

Oostegites ( Fig. 7 C–F ) those of gnathopod 2 and pereopod 3 elongate; that of pereopod 4 ovoid, widest; that of pereopod 5 small, half as long as that of pereopod 4, linear.

Remarks.

The genus Latigammaropsis was established by Myers (2009) based on the ' atlantica ' group of Gammaropsis sensu lato, and has been diagnosed by having a different shape of uropod 3: peduncle is shorter and broader; outer ramus is blunt-ended with a vestigial 2nd article bearing two fine setae; and inner ramus is subequal to or shorter than outer ramus, narrowing distally and with a single small robust seta inserted at its tip ( Barnard 1965, 1970; Myers 1995, 2009). The Korean material examined in this study also shows these diagnostic characters and could be readily assigned to the genus Latigammaropsis . Moreover, this material was identified as a new species, with specimens notably characterized by the absence of excavations on the palmar margin of gnathopod 2 in both sexes. Usually, mature males of the genus Latigammaropsis have an excavated gnathopod 2 palmar margin and a smooth margin has been considered a feature of immature specimens ( Barnard 1970). Unfortunately, the authors of this study only described one holotype male and one paratype female, so it is unknown if intraspecific variations are related to maturity in both sexes. However, we certainly confirmed their maturity based on the presence of lageniform eyes in both sexes as a sign of adulthood ( Barnard 1965), and the ovigerous paratype female having a similar shaped gnathopod 2.

The shape of gnathopod 2 between both sexes is quite similar to each other, except for the more setose basis and propodus in males. A lack of strong sexual dimorphism in gnathopod 2 was described in Latigammaropsis gemina (Myers, 1995) and Latigammaropsis christenseni (Myers, 1995). However, Latigammaropsis careocavata sp. nov. differs from these species by the absence of an excavated palmar margin and the strongly setose basis and propodus of gnathopod 2 in males ( Myers 1995).

Until now, all known species of this genus have been recorded from tropical regions ( Stebbing 1888; Schellenberg 1925, 1938; Barnard 1965, 1970; Ruffo 1969; Ledoyer 1978; Myers 1995, 2009, 2014; Myers and Nithyanandan 2016). This is the first record of the genus Latigammaropsis from Korean waters as well as from outside of the tropics.

Figures

Figure 4. Latigammaropsis careocavata sp. nov., holotype, NIBRIV 0000806529, male, 7.5 mm, Sogueulbi-do Island, South Korea. A habitus B head C, D antenna 1 E, F antenna 2 G upper lip H lower lip I left mandible J incisor and lacinia mobilis of right mandible K, L maxilla 1 M maxilla 2. Scale bars: 0.05 mm (J-M), 0.1 mm (G-I), 0.2 mm (C-F), 0.5 mm (B), 1.0 mm (A).

Figure 5. Latigammaropsis careocavata sp. nov., holotype, NIBRIV 0000806529, male, 7.5 mm, Sogueulbi-do Island, South Korea. A, B maxilliped C gnathopod 1 D gnathopod 2 E pereopod 3 F pereopod 4. Scale bars: 0.05 mm (B), 0.1 mm (A), 0.2 mm (C-F).

Figure 6. Latigammaropsis careocavata sp. nov., holotype, NIBRIV 0000806529, male, 7.5 mm, Sogueulbi-do Island, South Korea. A pereopod 5 B, C pereopod 6 D pereopod 7 E pleonites and urosomites, lateral F uropod 1 G uropod 2 H uropod 3 I telson. Scale bars: 0.2 mm (A-D, F-I), 0.5 mm (E).

Figure 7. Latigammaropsis careocavata sp. nov., paratype, NIBRIV 0000848929, female, 6.7 mm, Sogueulbi-do Island, South Korea. A gnathopod 1 B gnathopod 2 C-F oostegites of gnathopod 2 - pereopod 5. Scale bars: 0.2 mm.