Anonyx exilipes, Jung, Tae Won, Coleman, Charles Oliver, Kim, Ji Hyung & Yoon, Seong Myeong, 2018

Jung, Tae Won, Coleman, Charles Oliver, Kim, Ji Hyung & Yoon, Seong Myeong, 2018, First records of the uristid lysianassoids from Korean waters: redescription of Anonyxabei Takekawa & Ishimaru, 2001 and description of Anonyxexilipes sp. n. (Crustacea, Amphipoda, Uristidae), ZooKeys 733, pp. 99-117 : 102-106

Anonyx exilipes sp. n. Figs 5, 6, 7, 8

Type locality.

Near Daejin Port, Daejin-ri Hyeonnae-myeon Goseong-gun Gangwon-do South Korea. The specimens were collected from fishery nets of this port. According to the statements of fishermen, these nets were brought out within a 5 km radius from Daejin Port and the nets were deployed in about 1-2 km depth (The precise coordinates were uncertain).

Material examined.

Holotype: Male (23.0 mm), NIBRIV0000806537, paratypes: two males and two females (18.5 mm– 24.9 mm), NIBRIV0000807160; 11 Mar 2016, by TW Jung.

Etymology.

The composite epithet of the specific name, exilipes, is a combination of the Latin exilis and pes. This name means 'slender foot’ referring to the slender shapes of pereopods 6 and 7 compared to those of other species of the Anonyx laticoxae group.

Diagnosis.

Gnathopod 1 basis with setae along entire anterior margin; palm serrated; dactylus without protrusion. Gnathopod 2 propodus half as long as carpus, posterodistal corner produced distally, palm short, with small cavity; dactylus short, apex not exceeding corner of palm. Pereopods 3-4 each propodus with single locking setae posterodistally. Pereopod 6 carpus and propodus elongate, slender. Pereopod 7 merus not lobate. Epimeron 2 posteroventral corner acutely produced backwards. Epimeron 3 regularly rounded posteroventrally, posterior margin produced backwards. Uropod 2 both rami without constrictions. Uropod 3 inner ramus as long as proximal article of outer ramus.

Description of holotype male.

Head (Fig. 5B). Lateral cephalic lobes expanded anteriorly, subtriangular, apex rounded; eye large, pyriform, occupying most of anterior part of head, composed of numerous small ommatidia.

Antenna 1 (Fig. 5C, D) distinctly shorter than antenna 2; peduncle 1st article ovoid, expanded; 2nd and 3rd articles reduced; accessory flagellum composed of eight articles, 1st article longest, dilated distally, lined with several clusters of minute setae on posterior margin; flagellum 1st article distinctly elongate, calceoli present from 7th article.

Antenna 2 (Fig. 5A, E) elongate, 0.4 × as long as body; peduncle 4th, 5th articles convex posteriorly; 4th article setose on anterior margin; flagellum composed of 63 articles; calceoli present anterodistally.

Lower lip (Fig. 5F) densely pubescent; inner lobe distinct.

Mandible (Fig. 5G, H) incisor smooth but bearing blunt denticles on both sides; lacinia mobilis absent on both sides; nine and eight small raker setae on left and right mandibles respectively; molar process not triturative, flap-shaped, densely pubescent, lateral setigerous crest present; palp composed of three articles, attached nearly at level of molar process, 2nd article longest, setose anterodistally, 3rd article falcate 0.8 × as long as 2nd article, lined with setae on inner margin and apex.

Maxilla 1 (Fig. 6B, C) inner lobe short, subquadrate distally, with two plumose setae on blunt apex; outer lobe with eleven toothed setae in 7/4 arrangement; palp composed of two articles, distal article slightly dilated and curved distally, with eight robust setae on apical margin.

Maxilla 2 (Fig. 6D) inner lobe reduced, half as long as outer lobe, narrowing distally, with two rows of simple and plumose setae on mediodistal margin (proximal plumose seta longest); outer lobe also narrowing distally and with two setal rows on mediodistal margin.

Maxilliped (Fig. 6A) inner lobe with mediodistal row of plumose setae, apex rounded with three nodular setae; outer lobe well developed, subovoid, not beyond the palp 3rd article lined with many nodular setae from medial to distal half of lateral margins (all nodular setae small); palp composed of four articles, 2nd article 1.1 × as long as 1st article, with setae medially, 3rd article slightly dilated distally, 0.7 × as long as 2nd article, covered with minute setae distally and with many elongate setae, 4th article 0.7 × as long as 3rd article, apical seta robust, short.

Pereon.Gnathopod 1 (Fig. 6E, F) subchelate; coxa large, subtrapezoidal, expanded anteroventrally, posteroventral notch nearly weak; basis stout, as long as coxa, anterior margin straight, with setae along entire margin, posterior margin expanded distally, smooth, only with one cluster of setae at distal corner; ischium moderate in size, with one small anterior lobe; merus triangular, 0.3 × as long as basis, covered with minute setae posteriorly; carpus half as long as basis, convex anteroproximally, carpal lobe weak, apex rounded and covered with minute setae; propodus as long as carpus, gradually diminished distally but forming weak lobe together palm posterodistally, palm distinct, convex, serrated, defined by one pair of elongate robust setae; dactylus falcate, exceeding palm, without protrusion on inner margin, unguis developed.

Gnathopod 2 (Fig. 7 A–B) slender, minutely chelate; coxa subrectangular, slightly divergent ventrally, posteroventral notch nearly weak; basis 1.1 × as long as coxa, curved at distal 2/3 length; ischium elongate, half as long as basis; merus 0.8 × as long as ischium, with numerous short setae posteriorly, posterodistal corner angulate with many elongate setae; carpus 0.6 × as long as basis, anterior margin with three clusters of elongate setae on distal half (longest seta of distal cluster exceeding propodus), carpal lobe flattened, distal half margin also with elongate setae and covered with minute setae; propodus subrectangular, half as long as carpus, margins convex, lateral surface densely covered with setae, posterodistal corner produced distally, palm short, with small cavity; dactylus short, anchored at middle of distal margin on propodus, apex not exceeding corner of palm.

Pereopod 3 (Fig. 7C, D) coxa subrectangular, half as wide as long, posteroventral notch rather weak; basis 0.6 × as long as coxa, anterior margin straight, with eleven setae regularly, posterior margin expanded distally; ischium moderate in size, with one small anterior lobe; merus 0.8 × as long as basis, expanded anteriorly, slightly produced anterodistally; carpus 0.6 × as long as merus, not expanded; propodus 1.7 × as long as carpus, lined with paired setae on posterior margin, with one locking seta posterodistally; dactylus falcate, elongate, 0.4 × as long as propodus, unguis weak.

Pereopod 4 (Fig. 7E) coxa deeper than wide, expanded posteroventrally; other articles nearly similar with those of pereopod 3.

Pereopod 5 (Fig. 8A) coxa large, subrectangular, 1.2 × as wider as long, equilobate; basis subovoid, anterior margin rounded, lined with robust setae, with one pair of robust setae anterodistally (one seta elongate), posterior lobe well developed, more expanded proximally, margin somewhat flattened, crenulate, expanded posterodistal corner not exceeding ischium; ischium to carpus lined with elongate slender setae and short setae anteriorly; merus posterior lobe expanded distally; carpus subrectangular, 1.3 × as long as merus, posterior margin slightly swollen in midway; propodus linear, 1.1 × as long as carpus, lined with robust setae anteriorly, with one pair of locking setae; dactylus falcate, elongate, 0.4 × as long as propodus, unguis weak.

Pereopod 6 (Fig. 8B) longest; coxa subrectangular, smaller than that of pereopod 5, bilobate, anterior lobe small, posterior lobe more expanded posteroventrally; basis subovoid, as wide and 1.3 × as long as that of pereopod 5, anterior margin lined with robust setae regularly, posterior lobe well developed, margin somewhat flattened, crenulate, expanded posterodistal corner not angulate, not reaching distal end of ischium; elongate slender setae present from ischium to merus anteriorly; merus subrectangular, 0.4 × as long as basis, slightly expanded posteriorly, weakly produced posterodistally; carpus rectangular, not lobate, 1.6 × as long as merus, a little curved and slightly diminished distally; propodus slender, linear, as long as carpus, lined with robust setae anteriorly, with one pair of locking setae; dactylus falcate, elongate, 0.4 × as long as propodus, unguis weak.

Pereopod 7 (Fig. 8C) 0.9 × as long as pereopod 6; coxa unilobate, as large as that of pereopod 6, expanded posteroventrally; basis 1.1 × as wide and 1.1 × as long as that of pereopod 6, anterior margin slightly concaved at the middle, lined with robust setae, posterior lobe well developed, margin rounded, not flattened than those of pereopods 6-7; slender setae absent in ischium and merus; merus rectangular, not lobate, 0.3 × as long as basis, weakly produced posterodistally; carpus also not lobate, 1.6 × as long as merus; propodus slender, linear, 1.1 × as long as carpus, lined with robust setae anteriorly, with one pair of locking setae; dactylus falcate, elongate, 0.4 × as long as propodus, unguis weak.

Pleon.Epimeron 1 (Fig. 8D) weakly produced anteroventrally, rounded posteroventrally. Epimeron 2 (Fig. 8E) slightly larger than epimeron 1, also produced anteroventrally, slightly convex ventrally, posteroventral corner acutely produced backwards. Epimeron 3 (Fig. 8F) largest, regularly rounded posteroventrally, posterior margin produced backwards. Urosomite 1 with deep dorsal depression and distal carina weak (Fig. 5A).

Uropod 1 (Fig. 8G) longest; peduncle 1.3 × as long as inner ramus, with twelve robust setae on dorsolateral margin and six elongate robust setae on dorsomedial margin; rami subequal to each other; inner ramus with five dorsomedial and four dorsolateral robust setae; outer ramus with five dorsolateral setae and one dorsomedial seta.

Uropod 2 (Fig. 8H) 0.8 × as long as uropod 1; peduncle as long as inner ramus, with eight robust setae on dorsolateral margin and three robust setae on dorsomedial margin; both rami without constriction; inner ramus with two dorsolateral and five dorsomedial setae; outer ramus as long as inner ramus, with five dorsolateral robust setae.

Uropod 3 (Fig. 8I) 0.9 × as long as uropod 2; peduncle half as long as inner ramus; both rami with plumose setae on medial margin; outer ramus bi-articulate, distal article 0.2 × as long as proximal article; inner ramus 0.9 × as long as proximal article of outer ramus.

Telson (Fig. 8J) longer than broad, cleft to about 80%, each lobe with apical notch bearing one pair of robust seta and sensory seta, three or four robust setae and one pair of sensory setae dorsolaterally.

Remarks.

Steele (1986) divided the genus Anonyx into five subgroups according to the shapes of uropod 2. Among them, the Anonyx laticoxae group is characterized by sharing of the following features: uropod 2 is narrow, its inner ramus unconstricted, and with the distal seta equal to or only slightly longer than the proximal setae. This new species also has this character states and can be included in the A. laticoxae group. Moreover, Anonyx exilipes sp. n. shares several characteristic features with Anonyx laticoxae Gurjanova, 1962 such as similarly produced pleonal epimera, the similar expansions of coxae 1-4, and pereopods 3-4 having single locking setae on their propodus. However, Anonyx exilipes sp. n. differs from A. laticoxae by the different character states of the carpus and propodus of pereopod 6, which are longer and more slender, and the merus of pereopod 7, which is not lobate in the new species.