Melita panda Tomikawa, Yamato & Ariyama, 2024, sp. nov.
Creators: name: Tomikawa, Ko
name: Yamato, Shigeyuki
name: Ariyama, Hiroyuki
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Melitidae
Melita
Melita panda

description: Melita panda sp. nov.
Figs 1, 2, 3, 4, 5, 6 New Japanese name: Panda-melita-yokoebi
Melita sp. 1: Ariyama, 2022: 119.
Material examined.
Holotype: • male 6.0 mm (NSMT - Cr 32141); Tagurazaki, Wakayama, Japan; (34.264603 ° N, 135.060835 ° E); collected by Hiroyuki Ariyama and Ko Tomikawa; on 25 March 2019. Paratypes: • male 7.6 mm (NSMT - Cr 32142); female 4.8 mm (NSMT - Cr 32143); female 4.5 mm (SEM, NSMT - Cr 32144); data same as for the holotype • male 5.0 mm (NSMT - Cr 32145, G 1491); locality same as for the holotype; collected by Hiroyuki Ariyama; on 12 July 2018 • male 5.8 mm (NSMT - Cr 32146, G 1489); male 4.5 mm (NSMT - Cr 32147, G 1492); Jogasaki, Wakayama, Japan; (34.2850 ° N, 135.0680 ° E); collected by Hiroyuki Ariyama; on 14 July 2018 • male 5.2 mm (NSMT - Cr 32148); female 4.3 mm (NSMT - Cr 32149); Shirahama, Wakayama, Japan; (33.691826 ° N, 135.336172 ° E); collected by Hiroki Yamada and Ko Tomikawa; on 12 November 2023.
Diagnosis.
Head with eyes; antennal sinus incised. Pleonites and urosomites lacking dorsal teeth. Epimeral plate 3 with weakly pointed posterodistal corner. Urosomite 2 with 3 dorsolateral robust setae on each side without distinct teeth. Antenna 1 with 4 - articulate accessory flagellum. Maxilla 1 with inner plate bearing 7 plumose setae. Gnathopod 1 with basis and ischium bearing small palmate setae. Male gnathopod 1 with anterodistal projection on propodus forming rounded hood, covering almost all of dactylus, propodus with 3 and 1 robust setae on posterior margin and at the base of anterodistal projection, respectively. Male gnathopod 2 with subquadrate propodus setaceous on medial surface, angle between posterior and palmar margins of propodus being approximately 140 °. Female coxa 6 hooked with anterior lobe 1.2 times deeper than width of coxa. Uropod 3 with 1 - articulate outer ramus. Telson longer than its width.
Description.
Holotype, male, NSMT - Cr 32141. Head (Fig. 1) almost as long as pereonites 1 and 2 combined; rostrum short; eyes developed, oval; lateral cephalic lobe rounded; antennal sinus incised. Pereonites 1–7 (Fig. 1) dorsally smooth. Epimeral plates 1–3 (Fig. 2 A – C) with 2, 2 and 3 short setae on posterior margin; epimeral plate 3 posterodistal corner weakly produced, ventral margin with 5 robust setae. Pleonites 1–3 dorsal margins without teeth, each with 4 short setae and that of urosomite 1 with 2 short setae (Fig. 2 D); dorsal margin of urosomite 2 with 3 robust setae on each side (Fig. 2 D).
Antenna 1 (Fig. 2 E) length 0.7 times that of body; length ratio of peduncular articles 1–3 as 1.0: 1.3: 0.5; ventral margin of peduncular article 1 with 3 robust setae, posterodistal corner with robust seta; primary flagellum 23 - articulate with a few setae; accessory flagellum 4 - articulare, terminal article short. Antenna 2 (Fig. 2 F) length 0.6 times that of antenna 1; peduncular article 2 with robust seta on anterodistal corner; peduncular article 3 with robust setae on medial surface and posterodistal corner; peduncular articles 4 and 5 with 4 clusters of setae on posterior margins, peduncular article 5 1.1 times as long as article 4; flagellum 8 - articulate, article 1 2.3 times as long as article 2; calceoli absent.
Upper lip (Fig. 2 G) with convex, rounded ventral margin bearing minute setae. Left and right mandible with 5 - dentate incisor (Fig. 2 H – J); left lacinia mobilis (Fig. 2 I) 4 - dentate, right lacinia mobilis (Fig. 2 J) with 2 large and several small teeth; left and right accessory setal rows each with five-bladed setae and plumose seta; molar process triturative with plumose seta; palp tri-articulate, length ratio of articles 1–3 1.0: 2.3: 2.3, article 1 marginally bare, article 2 with 10 setae on ventral margin, article 3 with 12 and 3 setae on ventral and dorsal margins, respectively. Lower lip (Fig. 2 K) with broad outer lobes bearing minute setae, mandibular lobes narrow; inner lobes indistinct. Maxilla 1 (Fig. 2 L, M) with inner plate bearing 7 plumose setae; outer plate rectangular with 9 serrate robust setae; palp 2 - articulate; article 1 with 3 long setae on laterodistal corner; article 2 arched, outer margin bare, apical margin with robust and slender setae. Maxilla 2 (Fig. 2 N) with inner plate lacking oblique inner row of setae; outer plate slightly longer than inner plate. Maxilliped (Fig. 2 O) with inner plate not reaching half of palp article 2, bearing 3 robust setae distally; outer plate ovate, exceeding half of palp article 2, apical margin with plumose setae, inner submargin with robust setae; palp 4 - articulate, medial margin of article 2 lined with setae, article 3 weakly expanded medially, article 4 with fine facial setae and nail.
Gnathopod 1 (Fig. 3 A, B) smaller than gnathopod 2; coxa weakly expanded ventrally, ventral margin with setae; basis, anterior and posterior margins with long setae, posterodistal submargin with tiny palmate setae; ischium with tiny palmate setae; merus ventral margin with small setae; carpus not lobate, length 1.2 times that of propodus, anterodistal corner with palmate setae, posterior margin with clusters of setae; propodus 1.9 times as long as wide, anterodistal projection forming hood, covering almost all of dactylus (Figs 3 B, 6 A), robust seta at the base of anterodistal projection, posterior margin with 3 robust setae, palmar margin with slender setae; dactylus short, not exceeding palmar margin. Gnathopod 2 (Fig. 3 C, D) with subrectangular coxa, bearing setae on ventral margin; basis with long setae at anterodistal corner and on posterior margin, posterodistal submargin without palmate setae; ischium without palmate setae; carpus not lobate, length 0.4 times of that of propodus; propodus large, subquadrate, length 1.5 times as long as wide, angle between posterior and palmar margins being approximately 140 °, medial surface setaceous, palmar margin oblique with robust setae becoming thinner toward end; dactylus not exceeding palmar margin.
Pereopod 3 (Fig. 3 E) with subrectangular coxa, ventral margin with setae; basis arched, anterior margin with short setae, posterior margin with long and short setae; length ratio of merus, carpus, propodus and dactylus 1.0: 0.9: 0.9: 0.3; merus with robust setae on anterior margin, carpus and propodus with robust setae on posterior margins. Pereopod 4 (Fig. 3 F) with expanded coxa bearing posterior concavity, with ventral setae; basis weakly arched, anterior and posterior margins with long and short setae; length ratio of merus, carpus, propodus and dactylus 1.0: 0.8: 0.9: 0.3; carpus and propodus with robust setae on posterior margins. Pereopod 5 (Fig. 4 A) with bilobate coxa, anterior lobe large with small seta on anterior margin, posterior lobe with small setae on posterior margin; basis ovate with posterodistal lobe, anterior margin with robust setae, posterior margin with short setae; merus weakly expanded, length 2.2 times as long as wide. Pereopod 6 (Fig. 4 B) with bilobate coxa, anterior lobe marginally bare, posterior lobe with small seta on ventral margin and posterodistal corner; basis slender, ovate, anterior margin with robust setae, posterior margin with short setae, posterodistal corner lobate; merus length 2.4 times as long as wide. Pereopod 7 (Fig. 4 C) with coxa, bearing seta on posterior margin; basis subovate, anterior margin with robust setae, posterior margin weakly serrate with short setae, posterodistal corner lobate; merus length 2.1 times as long as wide.
Coxal gills present on gnathopod 2, and pereopods 3–6.
Pleopods 1–3 (Fig. 4 D) peduncles with paired retinacula on inner distal margin and facial setae; inner ramus with bifid plumose setae (clothes-pin setae) on inner basal margin.
Uropod 1 (Fig. 5 A) extending beyond uropod 2; peduncle length 1.3 times longer than inner ramus, with basofacial robust seta; inner ramus almost as long as outer ramus, with 3 inner and 2 outer marginal robust setae; outer ramus with 3 robust setae on inner and outer margins, respectively. Uropod 2 (Fig. 5 B) not extending beyond peduncle of uropod 3; peduncle length 1.1 times longer than inner ramus; inner ramus almost as long as outer ramus, with 2 and 1 robust setae on inner and outer margins, respectively; outer ramus with 2 inner and 4 outer marginal robust setae. Uropod 3 (Fig. 5 C) with peduncle not extending beyond telson, 0.4 times as long as outer ramus; inner ramus length 0.2 times that of outer ramus, with subdistal robust seta; outer ramus with single article, straight, length 5.4 times that of outer ramus width, inner and outer margins each with 5 clusters of robust setae, distal part with robust and slender setae, longest distal slender seta shorter than longest distal robust seta.
Telson (Fig. 5 E) length 1.1 times longer than wide, almost completely cleft, each lobe with 1 medial, 4–5 subdistal and 3 lateral robust setae.
Female (paratype, NSMT - Cr 32143), sexually dimorphic characters. Gnathopod 1 (Fig. 5 F, G) with carpus length 1.2 times that of propodus; propodus palmar margin vertical, with 2 rows of slender setae, palmar angle with robust seta. Gnathopod 2 (Fig. 5 H, I) with elongate coxa; carpus length 0.8 times that of propodus; propodus 1.7 times as long as wide, palmar margin oblique, with 4 robust setae along palmar margin and 2 robust setae on palmar corner.
Coxa of pereopod 6 (Figs 5 K, 6 B, C) with anterior lobe 1.2 times deeper than width of coxa, strongly hooked, bearing slit-like shallow “ pocket ” at base, trailing edge near tip of anterior lobe loosely turned up.
Oostegites (Fig. 5 J) present on gnathopod 2 and pereopods 3–5, narrow with setae.
Coloration in life.
Black pattern on white background. The black pattern is found in the following areas: antennae 1 and 2 peduncular articles; part of head, pereonites 1, 2, 3 (part), 5–7; coxae 1, 2, 3 (part), 5 (part), 6, 7; distal part of gnathopod 2 propodus; posterior half of bases of pereopods 5–7; dorsal part of pleonites 1 and 2, urosomite 1 posterior half, urosomites 2 and 3; and uropods 1 and 2 peduncles, uropod 3. Coloration is almost identical between males and females, but females lack the black area on gnathopod 2. Colors remain largely unchanged after ethanol fixation.
Etymology.
The species name “ panda ” is derived from its black-and-white body coloration, which resembles that of the giant panda Ailuropoda melanoleuca.
Molecular phylogeny.
The obtained ML tree exhibited a topology almost identical to that of the BI tree (Fig. 7). Melitidae formed a monophyletic group with high statistical support (USB = 99 %, BPP = 0.99). The monophyly of Melita was supported by the BI tree (BPP = 0.93) but less so by the ML tree (USB = 0.68). Melita panda sp. nov. was the sister taxon of M. nagatai and M. koreana among the 14 species of Melita used in the analyses (USB = 98 %, BPP = 1.0). These three species formed a monophyletic group with M. hoshinoi (USB = 99 %; BPP = 0.99).
description: Published as part of Tomikawa, Ko, Yamato, Shigeyuki & Ariyama, Hiroyuki, 2024, Melita panda, a new species of Melitidae (Crustacea, Amphipoda) from Japan, pp. 267-283 in ZooKeys 1212 on pages 267-283, DOI: 10.3897/zookeys.1212.128858