Dulzura projecta, 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 : 2279-2287

Dulzura projecta sp. nov.

( Figures 1 – 5 )

Material examined

Holotype: male (OMNH-Ar-9974), 6.6 mm, Jogasaki coast, Wakayama City , Wakayama Prefecture, 34°17 ʹ 06 ″ N, 135°04 ʹ 08 ″ E, lower intertidal zone, reverse surface of large stone, 11 June 2006, coll. H. Ariyama. Paratypes: 2 males and 1 ovigerous female (OMNH-Ar-9975 – 9977), 5.2, 3.9, 4.4 mm, same data as holotype; 4 males and 1 ovigerous female (OMNH-Ar-9978 – 9982), 4.0, 3.5, 2.9, 2.9, 3.1 mm, Nagasaki coast, Misaki Town , Osaka Prefecture, 34°19 ʹ 49 ″ N, 135°09 ʹ 08 ″ E, 4 m depth, coarse sand, 9 October 2003, coll . H . Ariyama; 2 males and 1 ovigerous female (OMNH-Ar-9983 – 9985), 3.7, 2.7, 3.6 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.

Description

Male [based on holotype, 6.6 mm (OMNH-Ar-9974), paratype, 5.2 mm (OMNH-Ar- 9975) for pleopod 3, and paratype, 4.0 mm (OMNH-Ar-9978) for antenna 1 and lower lip]. Body ( Figure 1 ) slender; head small, antennal sinus present; pereonite 7 wider than anterior pereonites; pleonites wide; urosomites narrow, without dorsal robust setae.

Antenna 1 ( Figure 2 (a)) long, with ratio of lengths of peduncular articles 1 – 3 1: 0.9: 0.3, peduncular article 1 with strong robust seta posterodistally, laterodistal surface setose; accessory flagellum short, with 4 setae; primary flagellum with 19 articles (probably regenerated), tip of flagellum with short article and long setae ( Figure 2 (a1)). Antenna 2 ( Figure 2 (b)) relatively short, with ratio of lengths of peduncular articles 3 – 5 1: 2.8: 2.6; flagellum with 15 articles.

Upper lip ( Figure 2 (c)), ventral margin rounded, setose. Mandible ( Figure 2 (d,d1,d2,e, e1)), incisor bearing 5 and 4 cusps in left and right, respectively, left lacinia mobilis long, 4-dentated, right lacinia mobilis with wide denticulate and narrow triangular lobes, number of accessory blades 8 on left side and 6 (2 thick and 4 thin) on right side; molar developed; palp article length ratio 1: 3.2: 3.3 in right, article 2 with 1 short and 1 long seta, article 3 bearing many setae on ventral margin and 1 thick and 2 thin long setae on tip, distal two-thirds of lateral surface covered with many tiny setae. Lower lip ( Figure 2 (f)), medial margins of outer lobes setose, mandibular processes small. Maxilla 1 ( Figure 2 (g,g1 – g3)), inner plate with 12 plumose setae medially; distal margin of outer

plate with 11 robust setae; palp article 2 narrow (left) or wide (right), distal end with 7 thin (left) or thick (right) robust setae. Maxilla 2 ( Figure 2 (h)), both plates about same length, terminal ends bearing many setae. Maxilliped ( Figure 2 (i,i1,i2)), inner plate truncate, distal margin with 4 robust setae; outer plate small, distal margin with 4 long thick setae, medial margin with 8 robust setae; palp stout, ventral surface of article 3 covered with short setae, article 4 with nail.

Gnathopod 1 ( Figure 3 (a,a1)), coxa rhomboid, anterior and ventral margins with several short setae; basis stout, middle of posterior margin swollen, with 3 setae; ischium bearing 3 setae on posterodistal margin; merus short, posterodistal margin with 1 long and many short setae; carpus very long, straight, posterolateral surface with numerous long setae, medial surface sparsely setose; propodus short, about 0.4 times as long as carpus, anterodistal corner setose, posterodistal corner with 3 short robust setae, otherwise poorly setose; dactylus very short, tip slightly curved. Gnathopod 2 ( Figure 3 (b,b1)) large; coxa roundish trapezoidal, produced posterodorsally, anterior and ventral margins with several short setae, gill large, subquadrate; basis relatively slender, middle of posterior margin slightly swollen, with 4 setae; merus short, posterodistal margin bearing 2 setae; carpus pyriform, posterior margin heavily setose; propodus very long, about 2.3 times as long as carpus, posterior margin slightly excavated at a point two-thirds, posterior and medial margins bearing numerous long setae, palm with 2 marginal and 4 + 2 medial small robust setae; dactylus robust, strongly curved, posterior margin lined with tiny curved setae.

Pereopods 3 – 4 ( Figure 3 (c,d)) subequal; coxae roundish trapezoidal, ventral margins with several short setae, gills very large; bases straight, anterior margins with robust seta distally, posterior margins with 1 – 2 long setae and 3 – 4 short robust setae; meri anterior margins bearing 2 short robust setae; carpi with robust seta posterodistally; propodi bearing 4 pairs of short robust setae on posterior margins; dactyli short, almost straight. Pereopod 5 ( Figure 3 (e)) longer than pereopods 3 – 4; coxa lobate, anterior half longer than posterior half, ventral margin with several short setae, posterior margin with seta, gill large; basis expanded, a little lobate posterodistally, with slightly serrate margin, anterior margin with 3 small robust setae, anterodistal corner setose; merus bearing long and short setae on anterodistal corner, posterior margin with 3 robust setae, posterodistal corner with 4 robust setae; carpus bearing 3 groups of setae on anterior margin, posterior margin with pair of short robust setae, posterodistal corner with several robust setae; propodus with seta and 3 groups of setae on anterior margin, posterior margin with 4 groups of robust setae; dactylus short, almost straight. Pereopod 6 ( Figure 3 (f)) about 1.3 times as long as pereopod 5; coxa with small anteroventral lobe, posterior margin with seta, gill relatively small; basis expanded, posterodistal corner lobate, with slightly serrate margin, anterior margin with 7 small robust setae, anterodistal corner setose; merus bearing robust seta on middle anterior margin, anterodistal corner setose, posterior margin with 1 + 1 + 2 robust setae, posterodistal corner with 4 robust setae; carpus bearing seta and 3 groups of setae on anterior margin, posterior margin with 1 + 3 short robust setae, posterodistal corner with many robust setae; propodus, anterior and posterior margins with 5 and 4 groups of setae, respectively; dactylus short, almost straight. Pereopod 7 ( Figure 3 (g)) slightly longer than pereopod 6; coxa flattenedtriangular, posterior margin with 3 setae; basis expanded, posterodistal corner lobate, with serrate margin, anterior margin with 6 small robust setae, anterodistal corner setose; merus without robust seta on anterior margin, anterodistal corner setose, posterior margin with 1 + 2 + 2 robust setae, posterodistal corner with 4 robust setae; carpus bearing 3 groups of setae on anterior margin, posterior margin with 1 + 3 short robust setae, posterodistal corner with many robust setae; propodus, anterior and posterior margins each with 5 groups of setae; dactylus short, almost straight.

Pleonal epimera ( Figure 4 (a)), epimeron 1 slightly produced on posteroventral corner, ventral margin bare; epimeron 2 produced posteroventrally, ventral margin with 2 robust setae; epimeron 3 rounded on posteroventral corner, but posterodorsal corner sharply projected, ventral margin bearing many robust setae. Pleopods 1 – 2 ( Figure 4 (b, c)) subequal, slender; peduncles long, each with 2 coupling hooks and posterodistal projection; outer rami shorter than inner, outer and inner rami with 12 and 11 articles in pleopod 1 and both with 10 articles in pleopod 2, respectively. Pleopod 3 ( Figure 4 (d,e)), peduncle bearing lateral robust seta and anterodistal projection, medial surface with 2 coupling hooks and short seta; outer and inner rami each with 9 articles, outer ramus broad, article 1 with vertical ridge posteriorly, article 1 of inner ramus curved, with large outward projection distally. Uropod 1 ( Figure 4 (f)) stout; peduncle with 1 basofacial, 4 dorsolateral and 3 dorsomedial robust setae, laterodistal end bearing extremely large robust seta; both rami almost same length, about 0.7 times as long as peduncle, outer ramus with 4 marginal and 5 terminal setae, inner ramus with 5 marginal and 5 terminal setae. Uropod 2 ( Figure 4 (g,g1)) short, about 0.6 times length of uropod 1; peduncle bearing 4 dorsolateral and 1 dorsodistal robust setae, mediodistal corner with robust seta and comb of short setae; outer ramus about 0.9 times as long as peduncle, inner ramus longer than outer, about 1.1 times as long as peduncle, both rami with 5 marginal and 5 terminal robust setae. Uropod 3 ( Figure 4 (h)) very large, about 1.6 times length of uropod 1; peduncle short, dorsal surface, lateral margin, dorsodistal margin and ventrodistal margin with 3, 2, 3 and 10 robust setae, respectively; outer ramus long, about 3.2 times as long as peduncle, article 1 broad, lateral and medial margins each with 4 groups of robust setae, distal margin with many robust setae, article 2 narrow, dirkshaped, 15% length of article 1, tip with 3 minute setae; inner ramus short, 28% as long as outer ramus, bearing 1 lateral and 2 medial robust setae, tip acutely projected. Telson ( Figure 4 (i)) wider than long, deeply cleft, tips of both halves produced triangularly, both sides of projections each with 2 robust setae, lateral robust setae lacking.

Female [paratype, 3.1 mm (OMNH-Ar-9982)]. Gnathopod 1 ( Figure 5 (a,a1)), coxa produced posterodorsally, anterior margin with several short setae, ventral margin with 2 long and 2 short setae; basis swollen on middle posterior margin, with 5 long setae; ischium bearing 3 setae on posterodistal margin; merus short, posterodistal margin with 1 long and several short setae; carpus not long, straight, posterior margin and mediodistal surface setose; propodus short, about 0.8 times as long as carpus, anterodistal corner setose, posterodistal corner with 2 short robust setae; dactylus very short, tip slightly curved. Gnathopod 2 ( Figure 5 (b,b1)) smaller than that of male; coxa produced posterodorsally, anterior margin with 2 short setae, ventral margin with 2 long and 2 short setae, gill very large, ovoid, oostegite narrow, with 4 setae; basis slightly swollen on middle posterior margin, with 4 setae; merus short, posterodistal margin bearing 3 setae; carpus longish pyriform, posterior margin with many bundles of setae; propodus slightly long, about 1.1 times as long as carpus, posterior margin with 4 bundles of setae, anterodistal corner setose, palm bearing 2 robust setae medially; dactylus slender, weakly curved. Pleonal epimera ( Figure 5 (c)), epimera 1 – 2 slightly produced posteroventrally, ventral margin bare in epimeron 1 and with robust seta in epimeron 2; epimeron 3 acutely projected on posteroventral corner, ventral margin bearing 2 robust setae. Pleopod 3 ( Figure 5 (d)), lateral margin of peduncle with robust seta, mediodistal corner with 2 coupling hooks and short seta; outer and inner rami each with 7 articles, both rami slender, article 1 of inner ramus without projection. Other parts generally similar to male except for oostegites.

Small males. Paratype, 4.0 mm (OMNH-Ar-9978): gnathopod 1 ( Figure 5 (e)), propodus about half length of carpus; gnathopod 2 ( Figure 5 (f)), excavation and robust setae on palm almost same as holotype. Paratype, 2.9 mm (OMNH-Ar-9981): gnathopod 1 ( Figure 5 (g)), propodus about 0.7 times as long as carpus; gnathopod 2 ( Figure 5 (h)), excavation on palm absent, number of robust setae same as holotype, but proximal 2 setae larger.

Coloration in life

Whole body faintly yellowish white.

Etymology

From the Latin projecta (= projected), referring to the shape of male pleopod 3.

Remarks

In Dulzura projecta sp. nov. the inner ramus of male pleopod 3 has a projection on article 1 which differentiates it from other species in the genus. Such sexual dimorphism in pleopod 3 is also known for D. lobata , where the male pleopod 3 has a swelling on articles 1 in both rami ( Stock and Vonk 1991). The very long carpus of male gnathopod 1 is also unique to D. projecta with other species of Dulzura having a shorter carpus. In D. projecta the bases of pereopods 5 to 7 are lobate, which is also seen in D. lobata , and the male epimeron 3 has a sharp projection on the posterodorsal corner which is shared with D. hamakua and D. paucispinosa .

Distribution

From Osaka Prefecture to Mie Prefecture in Japan .

Habitat

Under large stones and in coarse sand, probably interstitial; from the lower intertidal zone to 4 m depth.

Figures

Figure 1. Dulzura projecta sp. nov. Holotype, male (OMNH-Ar-9974), 6.6 mm. Habitus, lateral view.

Figure 3. Dulzura projecta sp. nov. Holotype, male (OMNH-Ar-9974), 6.6 mm. (a, b) Left gnathopods 1–2, lateral views; (a1) propodus and dactylus of left gnathopod 1, lateral view, normal setae omitted; (b1), proximal part of palm on left gnathopod 2, lateral view, normal setae omitted; (c–g) left pereopods 3–7, lateral views. Scale: a–g, 0.50 mm; a1, b1, 0.25 mm.

Figure 4. Dulzura projecta sp. nov. All but (e), holotype, male (OMNH-Ar-9974), 6.6 mm; (e) paratype, male (OMNH-Ar-9975), 5.2 mm. (a) Right pleonal epimera 1–3, lateral view; (b) left pleopod 1, anterior view; (c) left pleopod 2, posterior view; (d) left pleopod 3, posterolateral view; (e) left pleopod 3, posterior view; (f) left uropod 1, dorsolateral view; (g) left uropod 2, lateral view; (g1) mediodistal corner of left uropod 2 peduncle, medial view; (h) right uropod 3, dorsal view; (i) telson, dorsal view. Scale: a–d, 0.50 mm; e–i, 0.41 mm, g1, 0.25 mm.

Figure 5. Dulzura projecta sp. nov. All except for (e–h), paratype, female (OMNH-Ar-9982), 3.1 mm; (e–f) paratype, male (OMNH-Ar-9978), 4.0 mm; (g–h) paratype, male (OMNH-Ar-9981), 2.9 mm. (a, b) Left gnathopods 1–2, lateral views: (a1, b1) propodi and dactyli of left gnathopods 1–2, lateral views, normal setae omitted; (c) right pleonal epimera 1–3, lateral view; (d) left pleopod 3, posterior view; (e, g) carpi–dactyli of left gnathopods 1, lateral views, normal setae omitted; (f, h) propodi and dactyli of left gnathopods 2, lateral views, normal setae omitted. Scale: e, f, 0.20 mm; a, b, d, 0.16 mm; c, g, h, 0.133 mm; a1, b1, 0.08 mm.