Parafoxiphalus longicarpus Alonso de Pina,

Senna, Luiz F. Andrade André R., 2021, Phoxocephalidae G. O. Sars, 1891 (Crustacea: Amphipoda) collected by the R / V Almirante Saldanha off the coast of Uruguay and Argentina, Nauplius (e 2021025) 29, pp. 1-42 : 32-39

Parafoxiphalus longicarpus Alonso de Pina,

2001

( Figs. 20–24 )

Parafoxiphalus longicarpus Alonso de Pina, 2001: 517 , figs. 1–6. — Chiesa et al., 2005: 171, 172. — Chiesa and Alonso, 2007: 108. — De Broyer et al., 2007: 191. — Alonso de Pina et al., 2008: 20, 21, 33, 34. — Calgagno et al., 2012: 941. — Alonso and Chiesa, 2014: 206–209, fig. 2L–N.

Material examined. 1 female, dissected and illustrated, st. 2886, 38°06’S 55°13’W, Argentina, 440–480 m depth, February 1972 ( UERJ 472 ) ; 1 female, in 70 % ethanol, same sampling data ( MNRJ 29883 ) .

Diagnosis. Head with rostrum developed, not constricted. Mandible left lacinia mobilis with 5 teeth, right with 4 teeth; palp article 1 short, article 2 weakly setose, article 3 strongly oblique and setose. Maxilla 1 outer plate with 11 stout setae apically. Maxilliped outer plate slender and short. Coxae 1–3 progressively increasing in size. Coxa 4 large, margins divergent. Pereopods 3–4 propodus with medium stout setae widely spread in distal two-thirds of article and bearing mid-apical shorter seta. Uropod 1 peduncle dorsolateral margin with stout setae confined medially and distally. Uropods 1–2 rami with articulate apical nail. Telson with pair of dorsal plumose setules on each lobe.

Redescription (based on female, UERJ 472). Habitus as in Fig. 20 . Head with ventrolateral line present. Antenna 1 peduncle article 1 ventral margin with simple and brush setae; article 2 ventral margin with 12 setae, facially with 2 slender and 2 brush setae; article 3 ventral margin with 2 setae, dorsal apex with 1 brush seta, with 2 facial brush setae distally; primary flagellum 13-articulate; accessory flagellum 9-articulate. Antenna 2 peduncle article 2 short; article 3 with 1 pectinate and 3 short setae facially; article 4 facial stout setae formula: 4-4-2-2, ventral margin with medium to long setae, dorsal margin with 3 long setae medially and tuft of setae distally; article 5 ventral and dorsal margins weakly setose, with 4 facial stout setae medially and 2 distally; flagellum 12-articulate. Mandible incisor with 4 (left) and 3 (right) teeth; lacinia mobilis with 5 (left) and 4 (right) teeth; molar as hump with 6 setae (left and right); accessory setal row with 10 (left) and 11 (right) multicuspidate stout setae; palp article 2 medial margin with 4 (left) and 5 (right) setae, article 3 about 1.4 × longer than article 2, apex oblique, with 10 (left) and 11 (right) medium to long setae. Maxilla 1 inner plate with 2 short and 2 plumose setae apically, lateral margin setulose; outer plate with 11 stout setae (5 multicuspidate, 3 bifid); palp article 2 setulose medially and facially, apical margin with 3 stout and 5 slender setae, lateral margin with setules distally. Maxilla 2 inner plate setulose proximally, medial margin with 7 plumose and 5 slender setae extending to apical margin, lateral margin setulose; outer plate setose apically, lateral margin setulose. Maxilliped inner plate with 6 plumose setae and 2 stout setae, medial and lateral margins with setules; outer plate medial margin with 7 stout setae, apical margin with 2 stout setae, lateral margin with 5 plumose setae; palp article 2 medial margin moderately setose, article 3 weakly setose, lateral margin with 1 long seta medially, weakly produced distally, article 4 elongate, bearing 1 long apical nail.

Gnathopod 1 weakly setose; coxa subrectangular, ventral margin with 7 setae; basis elongate, about 4.2 × longer than wide; carpus slightly longer than propodus; propodus anterior margin with 2 tufts of setae distally, posterior margin with 1 stout seta defining palm; palm acute, palmar hump medium; dactylus reaching palmar angle, proximally with 1 short seta. Gnathopod 2 weakly setose; coxa subrectangular, ventral margin with 8 setae; carpus posterior margin with 9 setae; propodus slightly longer than carpus, anterior margin with tuft of setae distally, posterior margin with 1 stout seta defining palm; palm acute, palmar hump medium; dactylus reaching the palmar angle, proximally with 1 short seta. Pereopod 3 weak to moderately setose; coxa subrectangular, ventral margin with 8 setae; carpus posterior margin moderately setose, distally with 1 long stout seta extending to apex of propodus, with facial row of 7 setae; propodus with medium posterior and facial stout setae extending to apex; dactylus about 20 % length of propodus, with acute spine distally. Pereopod 4 similar to pereopod 3; coxa produced posteriorly, posterodorsal margin excavate, ventral margin with 7 setae; carpus posterior margin moderately setose, distally with 1 long stout seta extending to apex of propodus, with facial row of 7 setae; propodus anterior margin with 1 short seta distally, posterior margin with 7 stout setae, with 8 facial stout setae extending to apex; dactylus about 20 % length of propodus, with acute spine distally. Pereopod 5 coxa bilobate, posteroventral margin with 3 setae; basis about 1.5 × longer than wide, anterior margin with 7 setae, anterodistal corner with 4 setae; merus anterior margin moderately setose, posterior margin with 5 pappose setae, with 4 facial rows of stout setae: 4-5-4-7; carpus anterior margin with slender and plumose setae, posterior margin with 10 pappose setae, with 5 facial rows of stout setae: 3-3-3-4-5; propodus anterior margin with slender setae medially and 4 stout setae distally, posterior margin with 8 plumose setae medially and 1 stout and 1 slender seta distally; dactylus about 50 % length of propodus, with minute acute spine distally. Pereopod 6 coxa posterior margin with 5 setae; basis about 1.2 × longer than wide, anterior margin with 13 setae, anterodistal corner with 7 setae; ischium short and subrectangular, anterodistal corner with 6 setae; merus anterior margin with 5 sets of stout setae: 5-4- 4-3-3, posterior margin with 6 pappose setae and 3 sets of stout setae:2-3-3; carpus anterior margin with 4 sets of stout setae: 3-4-4-6; propodus anterior margin with sparse stout setae, posterior margin with 3 stout and 5 long setae; dactylus about 35 % length of propodus, with minute acute spine distally. Pereopod 7 weak to moderately setose; coxa subtriangular, posterior margin with 5 setae; basis about 1.2 × longer than wide, expanded posteroventrally, slightly exceeding apex of merus, anterodistal corner with 2 stout setae, posterior margin weakly crenulate, ventral margin smooth; ischium, merus, carpus and propodus moderately setose anteriorly and weakly posteriorly; dactylus about 50 % length of propodus, with 1 short projection distally.

Epimeral plate 1 anterior margin with 3 setae, ventral margin and posteroventral corner convex, posterior margin weakly concave, with 3 setae. Epimeral plate 2 with 5 facial plumose setae, posterior margin weakly concave, with 3 setae. Epimeral plate 3 anterior margin convex, ventral margin almost straight, with 4 setae, posteroventral corner produced, posterior margin convex, with 5 setae. Urosomite 1 with ventral tuft of setae. Uropod 1 peduncle with 2 basofacial setae, distally with 1 displaced stout seta, dorsomedial margin with 4 stout setae, dorsolateral margin with 5 setae; outer ramus dorsal margin with 8 stout setae, bearing 1 subapical nail; inner ramus subequal to outer, dorsal margin with 4 stout setae, bearing 1 subapical nail. Uropod 2 peduncle dorsomedial margin with 6 stout setae, dorsolateral margin with 1 stout seta; outer ramus about 1.2 × longer than inner, dorsal margin with 5 stout setae, bearing 1 subapical nail; inner ramus dorsal margin with 3 stout setae, bearing 1 subapical nail. Uropod 3 peduncle dorsolateral margin with 1 stout and 2 short setae, ventro-apical margin with row of 7 stout setae; outer ramus about 1.3 × longer than inner, article 1 ventral margin with 6 sets of 2 stout setae each, dorsal margin with 9 long plumose setae, article 2 with 2 plumose setae apically; inner ramus dorsal margin with 6 plumose setae, apically with 2 plumose setae. Telson about 85 % cleft, each lobe with 2 stout setae and 1 short plumose seta apically, apex weakly excavate, dorsal margin with 2 long stout setae medially and 2 short plumose setae proximally.

Type locality. Argentina, Punta Pardelas , Golfo

Nuevo (42°37’S 64°16’W).

Remarks: This species was originally described with type material from off Chubut Province in Argentina ( Alonso de Pina, 2001). Parafoxiphalus is a monotypic genus and resembles Foxiphalus J.L. Barnard, 1979 in the general aspect of the body, the unconstricted rostrum, and the shape of the appendages; however, Alonso de Pina (2001) presented many remarkable characters to justify the erection of this genus. Besides some expected variation, such as the number of stout setae on appendages, the specimens examined here show some noteworthy differences distinguishing them from the original diagnosis established by Alonso de Pina. The author has stated that the propodus is longer than carpus on both gnathopods 1–2; however, in our specimens this is true only for the gnathopod 2, whilst the propodus of gnathopod 1 is about 80–85 % the length of carpus. Another variation can be observed in uropod 2, while in the original diagnosis the peduncle is longer than both rami, in our specimens the peduncle is shorter than rami. Due to these differences, we provide an amended diagnosis for the species, including two new important characters: mandible palp article 2 shorter than article 3 and carpus of gnathopod 2 shorter than in gnathopod 1.

Previously, the species has only been recorded in southern South America around the Magellanic region and Tierra del Fuego, but herein, we report Pa. longicarpus in the north of Buenos Aires Province in Argentina ( Fig. 25 ); extending its distribution limit further north .

Geographic distribution. Argentina: off Buenos Aires Province (38°06’S 55°13’W); Rio Grande, Tierra del Fuego; Magellanic region (see Alonso de Pina et al., 2008) .

Bathymetric range. The species was previously reported from 2–35 meters depth. In this study, Pa. longicarpus was collected at 440–480 meters depth.

Figures

Figure 20. Parafoxiphalus longicarpusAlonso de Pina, 2001, female (UERJ 472), Argentina (38°06’S 55°13’W).Hb, habitus,lateral view. Scale bar: 2.0 mm.

Figure 21. Parafoxiphalus longicarpus Alonso de Pina, 2001, female (UERJ 472), Argentina (38°06’S 55°13’W). Hd lateral view, head, lateral view; Hd dorsal view, head, dorsal view; A1, antenna 1, lateral view; A2, antenna 2, lateral view; L,Md, left mandible, mesial view; R,Md, right mandible, mesial view; Mp, left maxilliped, dorsal view; Mx1, left maxilla 1, dorsal view; Mx2, left maxilla 2, dorsal view. Scale bars: 0.1 mm for Mx1–2; 0.5 mm for Hd; 0.3 mm for the remaining.

Figure 22. Parafoxiphalus longicarpus Alonso de Pina, 2001, female (UERJ 472), Argentina (38°06’S 55°13’W). G1, gnathopod 1, lateral view; G2, gnathopod 2, lateral view; P3, pereopod 3, lateral view; P4, pereopod 4, lateral view. Scale bars: 0.5 mm.

Figure 23. Parafoxiphalus longicarpus Alonso de Pina, 2001, female (UERJ 472), Argentina (38°06’S 55°13’W). P5, pereopod 5, lateral view; P6, pereopod 6, lateral view; P7, pereopod 7, lateral view. Scale bars: 1.0 mm.

Figure 24. Parafoxiphalus longicarpus Alonso de Pina,2001, female (UERJ 472), Argentina (38°06’S 55°13’W).Ep1, epimeral plate 1, lateralview; Ep2, epimeral plate 2, lateralview;Ep3, epimeral plate 3, lateralview;U1,uropod 1, lateralview; U2, uropod 2, lateral view; U3, uropod 3, lateral view; T, telson, dorsal view. Scale bars: 0.5 mm for Ep1–3; 0.2 mm for T; 0.5 mm for the remaining.

Figure 25. Distribution of the phoxocephalids collected by the R/V Almirante Saldanha. Square: record for Pseudharpinia jonesyi (st. 2865). Triangle: record for Metharpinia dentiurosoma (st. 2868). Diamond: record for M. dentiurosoma (st. 2861). Star: records for M. dentiurosoma and Metharpinia grandirama (st. 2888). Plus sign: records for Pseudharpinia tupinamba, Fuegiphoxus abjectus, Fuegiphoxus fuegiensis, Metharpinia protuberantis, and Parafoxiphalus longicarpus (st. 2886).