Paraniphargus shiosai, Ariyama, 2016

Ariyama, Hiroyuki, 2016, Two new species of eyeless amphipods from a coastal area in Japan (Crustacea: Amphipoda: Hadziidae, Melitidae), with reinstatement of the genus Paraniphargus Tattersall, 1925, Journal of Natural History 50, pp. 2277-2297 : 2289-2294

Paraniphargus shiosai sp. nov.

( Figures 6 – 9 )

Material examined

Holotype: male (OMNH-Ar-9986), 1.7 mm, southeastern coast of Kamishima Island, Toba City , Mie Prefecture, 34°32 ʹ 36 ″ N, 136°59 ʹ 00 ″ E, 2.5 m depth, coarse sand, 26 July 2014, coll. H. Ariyama. Paratypes: 2 males, 1 ovigerous female and 1 juvenile (OMNH-Ar-9987 – 9990), 1.9, 1.8, 1.8, 1.4 mm, same data as holotype.

Description

Male [based on holotype, 1.7 mm (OMNH-Ar-9986), and paratype, 1.9 mm (OMNH- Ar-9987) for uropod 1 and telson]. Body ( Figure 6 ) very flattened laterally; head small, antennal sinus absent; pereonite 7 wider than anterior pereonites; pleonites wide, dorsodistal margins with 1, 3 and 3 small teeth in pleonites 1 – 3, respectively; pleonal epimera 1 – 2 slightly produced, epimeron 3 acutely produced on each posteroventral corner, each ventral margin bare; urosomite 1 wide, urosomites 2 – 3 narrow, dorsodistal margin of urosomite 2 with pair of robust setae.

Antenna 1 ( Figure 7 (a)) with ratio of lengths of peduncular articles 1 – 3 1: 0.8: 0.6, peduncular article 1 with 3 long and 1 short robust setae on posterior margin; accessory flagellum with 2 short and 1 minute articles, longer than article 1 of primary flagellum, tip setose; primary flagellum with 6 articles, last article minute, tip with several long setae. Antenna 2 ( Figure 7 (b)) about 0.8 times as long as antenna 1; ratio of lengths of peduncular articles 3 – 5 1: 2.5: 2.2, article 3 with robust seta each on anterior and posterior surfaces; flagellum with 4 articles, last article minute, tip with several long setae.

Upper lip ( Figure 7 (c)), ventral margin a little hollowed, bare. Mandible ( Figure 7 (d,d1, d2,e,e1)), both incisors bearing 4 cusps, lacinia mobilis slender, 4-dentate on left side, 2-dentate on right side, both accessory blades 6 in number, right second blade thick; molar medium-sized; palp article length ratio 1: 2.0: 1.5 in right, articles 2 – 3 with 1 and 4 setae, respectively. Lower lip ( Figure 7 (f)), mediodistal corners of outer lobes each with small notch and 1 thick and 1 thin seta, mandibular processes small. Maxilla 1 ( Figure 7 (g, g1)), inner plate with 3 setae distally; outer plate with 7 robust setae, some of them bearing acute spine; palp with 6 distal setae. Maxilla 2 ( Figure 7 (h)), outer plate longer than inner, terminal ends of both plates bearing many setae. Maxilliped ( Figure 7 (i)), inner plate truncate, distal margin with several normal setae; outer plate small, distal margin with 4 long thick setae, medial margin with robust seta; palp large, article 2 long, articles 2 – 3 poorly setose, article 4 with nail, covered with short setae on ventromedial surface.

Gnathopod 1 ( Figure 8 (a)), coxa longish rhomboid, anterior margin with short seta, ventral margin with 1 medium and 2 short setae; basis almost straight, anterior margin with 2 long setae; ischium setose on posterodistal margin; merus setose on posterior margin and posteromedial surface; carpus bearing several long setae on anterodistal corner and posterior margin, anterodistal surface with many short setae medially; propodus about 0.9 times as long as carpus, anterodistal corner and posterior margin setose, posterodistal corner with several short setae (not robust), anteroproximal surface with many short setae medially; dactylus short, curved. Gnathopod 2 ( Figure 8 (b)), coxa longish rhomboid, anterior margin with short seta, ventral margin with 1 medium and 2 short setae, posterior margin bearing medium seta, gill small; basis relatively stout, anterior and posterior margins with 4 and 1 short setae, respectively; merus slightly projected posterodistally; propodus long, about 2.1 times as long as carpus, posterior margin gradually curved, distal half of anterior margin bearing several setae, palm defined by 1 long and 1 short robust seta, with many short setae, posterior margin except palm bearing sparse setae; dactylus slender, with several short setae.

Pereopods 3 ( Figure 8 (c)), coxa longish rhomboid, posterior margin slightly excavated, ventral and posterior margins with 2 and 1 setae, respectively, gill large; basis slender, slightly curved anteriorly, posterior margin without long setae (lost?), merus – propodus slender, poorly setose; dactylus short, distal one-third curved. Pereopods 4 ( Figure 8 (d)) same length as pereopod 3; coxa subquadrate, posterior margin excavated, ventral and posterior margins with 4 and 1 setae, respectively, gill large; basis slender, slightly curved anteriorly, posterior margin with 2 long setae, merus – dactylus similar to pereopod 3. Pereopod 5 ( Figure 8 (e)), coxa lobate, anterior half longer than posterior half, ventral and posterior margins with 2 and 1 short setae, respectively, gill medium-sized; basis relatively wide, anterior margin with 3 short robust setae, anterodistal corner bearing 1 robust and 2 normal setae, posterior margin with 6 serrations each accompanied by short seta; merus, anterodistal and posterodistal corners each with robust seta. Pereopod 6 ( Figure 8 (f)), coxa lobate, anterior lobe longer than posterior, ventral and posterior margins each with short seta, gill small; basis relatively wide, anterior margin with 3 short robust setae, anterodistal corner bearing robust seta, posterior margin with 9 serrations each accompanied by short seta; merus bearing posterior robust seta, anterodistal and posterodistal corners each with robust seta. Pereopod 7 ( Figure 8 (g,g1)) long; coxa slightly lobate, margins bare; basis wide, anterior margin with 3 short robust setae, anterodistal corner bearing robust seta, posterior margin with 6 serrations each accompanied by short seta; merus with posterior robust seta, anterodistal and posterodistal corners with 2 and 1 robust setae, respectively; carpus bearing 1 + 2 robust setae on anterior margin, anterodistal and posterodistal corners with 2 and 1 robust setae, respectively; propodus, anterior and posterior margins with 1 + 2 and 2 + 2 robust setae, respectively, anterodistal corner bearing robust seta; dactylus short, almost straight, tip slightly curved.

Pleopods ( Figure 9 (a – c)) subequal, slender; peduncles long, each with 2 coupling hooks, peduncle of pleopod 3 with medial seta; both rami almost same length, outer and inner rami both with 5 articles in pleopod 1, 5 and 4 articles in pleopods 2 – 3, respectively. Uropod 1 ( Figure 9 (d)) stout; peduncle with 1 basofacial, 2 dorsolateral and 2 dorsomedial robust setae, laterodistal end bearing 1 large and 1 small robust seta; outer ramus about 0.6 times as long as peduncle, with 4 terminal setae, inner ramus a little longer than outer, about 0.7 times as long as peduncle, with 1 marginal and 5 terminal setae. Uropod 2 ( Figure 9 (e)) short; peduncle with 3 dorsal robust setae; outer ramus about 0.9 times as long as peduncle, with 2 marginal and 5 terminal robust setae, inner ramus longer than outer, almost same length as peduncle, with 1 marginal and 5 terminal robust setae. Uropod 3 ( Figure 9 (f)) slender; dorsolateral surface of peduncle with 2 robust setae; outer ramus long, about 2.4 times as long as peduncle, lateral and medial margins with 2 + 2 + 2 and 1 + 2 + 2 robust setae, respectively, distal margin with 4 robust setae; inner ramus rounded, 13% as long as outer ramus, with robust seta on tip. Telson ( Figure 9 (g,g1)) short, wider than long, cleft to base, both halves narrowed distally, each with 2 short sensory setae on dorsal surface, 2 robust setae on tip, and 1 small seta on ventral surface.

Female [paratype, 1.8 mm (OMNH-Ar-9989)]. Gnathopod 1 ( Figure 9 (i)) subequal to that of male, but coxa larger, posterior margin of basis with 4 long setae. Gnathopod 2 ( Figure 9 (j)) almost the same as for male, but narrow oostegite present. Coxa 6 ( Figure 9 (k)) without hook often occurring in Melita females, anterior lobe narrower than that of male. Other parts generally similar to male except for oostegites.

Coloration in fixed specimen

Whole body white.

Etymology

Shiosai is the name of a famous Japanese novel by Yukio Mishima. The setting for the novel is Kamishima Island, the type locality of this new species.

Remarks

Paraniphargus shiosai sp. nov. differs from P. annandalei and P. ruttneri in (1) the dorsal teeth on pleonites, (2) the smaller coxa 4 with shallow excavation, (3) the 3-articulated accessory flagellum, and (4) in having a shorter antenna 1 flagellum. Paraniphargus shiosai can also be distinguished from P. annandalei by the smooth posteroventral margins of pleonal epimera. In addition, P. shiosai was collected from marine habitats whereas P. annandalei and P. ruttneri are freshwater species.

Distribution

Only Kamishima Island in Mie Prefecture, Japan.

Habitat

In coarse sand, interstitial; 2.5 m depth. This species occurs together with Dulzura projecta sp. nov.

Figures

Figure 6. Paraniphargus shiosai sp. nov. Holotype, male (OMNH-Ar-9986), 1.7 mm. Habitus, lateral view. Scale: whole body, 0.25 mm; magnified parts, 0.08 mm.

Figure 7. Paraniphargus shiosai sp. nov. Holotype, male (OMNH-Ar-9986), 1.7 mm. (a) Right antenna 1, medial view; (b) left antenna 2, lateral view; (c) upper lip, anterior view; (d) right mandible, medial view; (d1) palp of right mandible, medial view; (d2) incisor, lacinia mobilis and accessory blades of right mandible, medial view; (e) left mandible, lateral view; (e1) incisor, lacinia mobilis and accessory blades of left mandible, lateral view; (f) lower lip, dorsal view; (g) left maxilla 1, ventral view; (g1), distal part of left maxilla 1, ventral view; (h) left maxilla 2, ventral view; (i) right maxilliped, dorsal view. Scale: a, b, 0.10 mm; c–i, d1, 0.05 mm; d2, e1, g1, 0.025 mm.

Figure 8. Paraniphargus shiosai sp. nov. Holotype, male (OMNH-Ar-9986), 1.7 mm. (a, b) Left gnathopods 1–2, lateral views; (c) left pereopod 3, lateral view; (d) right pereopod 4, lateral view; (e–g), right pereopods 5–7, lateral views; (g1), left coxa 7, lateral view.

Figure 9. Paraniphargus shiosai sp. nov. (a–c, e–g) holotype, male (OMNH-Ar-9986), 1.7 mm; (d, h) paratype, male (OMNH-Ar-9987), 1.9 mm; (i–k) paratype, female (OMNH-Ar-9989), 1.8 mm. (a) Right pleopod 1, lateral view; (b) left pleopod 2, posterior view; (c) left pleopod 3, anterior view; (d) left uropod 1, dorsolateral view; (e, f) right uropods 2–3, dorsal views; (g) telson, lateral view; (h) telson, dorsal view; (i, j) left gnathopods 1–2, lateral views; (k) left coxa 6, lateral view, gill omitted. Scale: d– h, 0.125 mm; a–c, i–k, 0.10 mm.