Jassakimi, Conlan & Desiderato & Beermann, 2021

Conlan, Kathleen E., Desiderato, Andrea & Beermann, Jan, 2021, Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus, Zootaxa 4939 (1), pp. 1-191 : 102-108

Jassakimi n. sp.

( Table 12 , Figs 60–61 )

Diagnosis.

Male:

Mandibular palp: article 2, dorsal margin without a fringe of setae.

Maxilla 1: without a seta or setal cluster at the base of the palp article 1.

Gnathopod 1: basis, anterolateral margin with a few minute setae along its length; carpus with a single short medial seta at the anterodistal junction of the propodus.

Gnathopod 2: basis without a row of long setae along the anterolateral margin (setae minute, << basis width); carpus and propodus, setae on the anterior margin minute (setal length << basis width).

Pereopods 5–7: propodus not expanded anteriorly.

Uropod 1: ventral peduncular spinous process underlying about 1/3 of the longest ramus.

Uropod 3: inner ramus without spines mid-dorsally (with only the single apical spine).

Telson: tip without apical setae in addition to the usual short setae at each dorsolateral cusp.

Thumbed male:

Antenna 2: without plumose setae on the flagellum and peduncular article 5.

Gnathopod 2: propodus, palmar defining spines not produced on a ledge, minute in large thumbed male (state for small thumbed males unknown). Minor male unknown. Major male, thumb distally rounded with posterior corner more acute than the anterior corner, incised well into the proximal half of the propodus. Dactyl expanded close to the junction with the propodus but not centrally toothed.

TABLE 12. (Continued)

Adult female: Unknown.

Description.

Male, holotype. Length 3.5 mm.

Antenna 1: each article with long filter setae on the posterior margin; accessory flagellum 2 articles, the second minute; flagellum 5 articles, the last minute, bearing aesthetascs.

Antenna 2: stouter than antenna 1 and overlapped by antenna 1 to 2/3 the length of article 5; without plumose setae on the posterior margin of the peduncle and flagellum; flagellum 3 articles, article 1 65% of flagellum length, article 3, 45% as long as article 3, flagellum articles 2 and 3 bearing curved spines posterodistally.

Mandible: palp articles 2 and 3 without dorsal fringe of setae; raker spines 2 right, 3 left.

Maxilla 1: palp without setae at the base of article 1, article 2 with 1 row of facial setae; inner plate without setae apparent.

Gnathopod 1: coxa produced forward and creased laterally, coxal margins, anterior 60% of dorsal length, ventral margin straight; basis flanged anteriorly, anterior margin without a fringe of long setae (all setae minute), posterior margin without setae; carpus, posterior lobe 40% of anterior margin length, with a single short medial seta at the anterodistal margin; propodus, palm shallowly concave, defined by 2 medial spines, these mid-distant along the palm; dactyl not facially striated.

Gnathopod 2: coxa rectangular, coxal margins, anterior 50% and posterior 40% of ventral length, ventral margin slightly wavy; gill present; carpus, posterior lobe without a cluster of setae; propodus, anterior margin without setae proximally, palm with a few plumose setae at the dactyl hinge, defined by a long, slightly sinuous thumb that is rounded at the anterior tip and more squared at the posterior tip, with 1 short palmar defining spine, thumb length 37% of propodus length.

Pereopod 3: coxa deepest posteriorly; basis, margins shallowly convex; merus, central setae 45% of article width, article width maximally 75% of length; carpus nearly 100% overlapped by the merus; propodus not posteriorly spinose.

Pereopod 4: coxa nearly square; other articles as for pereopod 3.

Pereopod 5–7: distal articles slender, propodus not distally expanded, with small spines only anterodistally at the junction of the dactyl; dactyl, posterior (outer) margin not cusped distally, anterior (inner) margin bearing a seta only at the unguis.

Pleopods: with 2 peduncular coupling hooks.

Uropod 1: peduncle, posteroventral spinous process underlying 37% of the inner ramus, inner and outer rami with 2 and 4 mid-dorsal spines respectively, not terminating in a fringe of cusps ventral to apical spine group.

Uropod 2: peduncle, posteroventral spinous process absent.

Uropod 3: outer ramus with 1 larger cusp proximal to the basally immersed, dorsally recurved spine and minute cusps around it; inner ramus without a spine mid-dorsally.

Telson: tip without apical setae in addition to the single long seta and pair of short plumose setae at each dorsolateral cusp.

Condition. Mouthparts, left antenna 1, right antenna 2, left gnathopod 1, right gnathopod 2, pereopods 3–7, pleopods 1–3 and uropods 1–3, left uropod 3 and telson slide mounted. Right antenna 1 article 1, left antenna 2, right gnathopod 1 coxa-ischium, left gnathopod 2, pereopod 5, pleopods and uropods 1 and 2 with the whole body. Missing remainder of right antenna 1 and gnathopod 1 and left pereopods 4, 6 and 7.

Type material examined. Holotype, male, 3.5 mm, from a light trap at 4–6 m depth near a breakwater at Impo Port, Yeosu-Si, The Republic of Korea, 34°35′47″N, 127°48′17″E, S.-S. Hong, collector, 23 June 2011. catalogue number: MARBK-115; deposit institution: Marine Amphipoda Resources Bank of Korea ( MARBK), Cheonan, South Korea.

Etymology. Named in honour of Young-Hyo Kim, who has considerably expanded our knowledge of the biodiversity of Korean amphipods.

Remarks. Numerous combinations of non-sexually dimorphic characters serve to distinguish J. kimi from all other species of Jassa . Jassa kimi lacks the fringe of setae on the anterior margin of the gnathopod 2 basis which is distinctive in numerous North Pacific species of Jassa ( J. borowskyae , J. carltoni , J. oclairi , J. staudei , J. marmorata , J. slatteryi , and J. morinoi ). From the other North Pacific species that also lack this fringe ( J. myersi and J. shawi ), it can be distinguished by having only a very short seta on the carpus of gnathopod 1 at the anterodistal junction of the propodus (long seta in J. myersi but short in J. shawi ). From J. shawi it can be distinguished by the length of the peduncular process underlying the rami of uropod 1. In J. kimi , this process is about one third the length of the longer inner ramus, which is typical of most species of Jassa . In J. shawi , this process is extremely short, appearing absent unless viewed microscopically.

When compared with Northern Hemisphere species that are restricted to the Atlantic and adjoining seas ( J. falcata , J. herdmani , J. laurieae , J. monodon and J. pusilla ), the absence of a setal fringe on gnathopod 2 can be readily used as a distinguishing character as all lack this fringe. These species bear other character states that are not shared with J. kimi . Jassa falcata and J. herdmani possess an extra fringe of setae on the second article of the mandibular palp which is directed dorsally, which J. kimi does not possess. Jassa monodon has a distinctive cluster of setae at the apex of the telson, which J. kimi lacks. Jassa laurieae and J. pusilla lack the carpal seta on gnathopod 1 that J. kimi possesses. The male dimorphism also differs. Jassa kimi does not bear plumose setae on antenna 2 while J. laurieae does. The thumb shape of the major male distinguishes J. kimi from J. pusilla : very long and slightly sinous in J. kimi with a squared end, while in J. pusilla the thumb is shorter and the tip incised.

For Southern Hemisphere species, the fringe of spine-like setae along the anterior margin of the basis of gnathopod 1, long carpal seta(e) on gnathopod 1 and/or the prehensile pereopods 5–7 will separate J. kimi from J. alonsoae , J. fenwicki , J. hartmannae , J. ingens , J. justi , J. kjetilanna and J. thurstoni . That leaves J. gruneri , which is less easy to compare as the thumbed male is unknown for J. gruneri but known for J. kimi and the female and juvenile are known for J. gruneri but unknown for J. kimi . When the female and juvenile male of J. kimi are found, it is likely that the palm of the gnathopod 2 will be concave, which is a characteristic of most Northern Hemisphere species of Jassa , while females and juvenile males of Southern Hemisphere species typically have sinuous palms (as does J. gruneri ). Other characteristics may also distinguish these species: e.g., fewer articles in the antenna 2 flagellum in J. kimi than J. gruneri and generally more slender and elongated mouthparts in J. kimi than J. gruneri .

Figures

FIGURE 60. Jassa kimi n. sp. Holotype, adult male, major form, 3.5 mm, DKU-115 (MARBK). Impo Port, Yeosu-Si, The Republic of Korea, 23 June 2011, S.-S. Hong, coll. (MARBK). Lateral view: whole body; dorsal view: telson; medial view: gnathopod 1 and uropod 3. Scale 0.1 mm.

FIGURE 61. Jassa kimi n. sp. Holotype, adult male, major form, 3.5 mm, DKU-115 (MARBK). Impo Port, Yeosu-Si, The Republic of Korea, 23 June 2011, S.-S. Hong, coll. (MARBK). Mouthparts. Frontal view: upper lip; lateral view: maxilla 1 and right mandible; other views medial. Scale 0.1 mm.