Microphoxus cornutus ( Schellenberg, 1931 )

Andrade, Luiz F. & Senna, André R., 2020, New and additional records of Metharpinia Schellenberg, 1931 and Microphoxus Barnard, 1960 (Crustacea: Amphipoda: Phoxocephalidae) from Brazilian waters, Papéis Avulsos de Zoologia 60, pp. 1-37 : 22-29

Microphoxus cornutus ( Schellenberg, 1931) ( Figs. 18‑22 )

Metharpinia cornuta Schellenberg, 1931: 68 , 269, 273, fig. 35. Dahl, 1952: 18. Barnard & Drummond, 1976: 522, 528. Barnard & Drummond, 1978: 24, 32, 145, 416. Barnard, 1979: 370.

Paraphoxus cornuta Barnard, 1958: 117 .

Paraphoxus cornutus Barnard, 1960: 186 , 194, 224, 271, 290. Lowry & Bullock, 1976: 126.

Microphoxus cornutus Barnard, 1980: 106 , 110. Wakabara et al., 1982: 68. Barnard & Karaman, 1991: 623. González, 1991: 50, 61. Wakabara et al., 1991: 74. Valério‑Berardo, 1992: 23. De Broyer & Jazdzewski, 1993: 84. Jarrett & Bousfield, 1994: 64. Wakabara & Serejo, 1998: 578. Pires‑Vanin et al., 1997: 36, 38. De Broyer & Rauschert, 1999: 286. Valério‑Berardo et al., 2000: 65. Alonso de Pina, 2001: 535. Bustamante, 2002: 62, 70, 76, 77. Scelzo et al., 2002: 48, 51, 53. Alonso de Pina, 2003a: 1029, 1030, 1045, 1055, 1057, figs. 10‑12, 16. Arasaki et al., 2004: 258. Chiesa et al., 2005: 171, fig. 2B. Muniz & Pires‑Vanin, 2005: 16. López‑Gappa et al., 2006: 17, 52. Chiesa & Alonso, 2007: 108. De Broyer et al., 2007: 190. Alonso de Pina et al., 2008: 19. González et al., 2008: 167. Ferrando et al., 2010: 348. Mendez et al., 2010: 431. Senna, 2010: 2077, 2116. Alonso, 2012: 1884. Pires‑Vanin et al., 2013: 47. Pires‑Vanin et al., 2014: 802. Andrade et al., 2015: 33. Soto et al., 2017: 437. Serejo & Siqueira,

2018: 36. Material examined: 3 ♀♀, in ethanol 70%, MBT 152,

23°03′S, 41°10′W, 98 m depth, Rio de Janeiro state, 04 September 1970 ( UERJ 429 ) ; 1 ♀, dissected and drawn, MBT 37, 23°51′S, 45°40′W, 22 m depth, São Paulo state, 06 May 1970 ( UERJ 426 ) ; 1 ♂, dissected and drawn, MBT 37, 23°51′S, 45°40′W, 22 m depth, São Paulo state, 06 May 1970 ( UERJ 427 ) ; 3 ♀♀ and 2 ♂♂, in 70% ethanol, MBT 37, 23°51′S, 45°40′W, 22 m depth, São Paulo state, 06 May 1970 ( UERJ 428 ) ; 4 ♀♀ and 2 ♂♂, in 70% ethanol, MBT 37, 23°51′S, 45°40′W, 22 m depth, São Paulo state, 06 May 1970 ( MZUSP 41108 ) .

Diagnosis: Head, eyes rounded and medium‑sized; rostrum narrow and short, reaching apex of article 1 of antenna 1. Antenna 1, article 2, with ventral setae widely spread. Antenna 2, article 4, with 3‑4 rows of facial stout setae. Mandible, molar as a small hump with stout setae. Maxilliped, inner plate with 1 stout seta apically; palp, article 4 elongate with medium apical nail, partially embedded. Gnathopods 1‑2, weakly setose, palm almost transverse, palpar hump small. Pereopods 5‑6 stout and setose. Pereopod 7, basis expanded posteroventrally, almost reaching apex of carpus. Epimeral plate 2, ventral margin with long plumose setae. Epimeral plate 3, posteroventral corner rounded,posterior margin weakly serrate, with long setae. Urosomite 1, with a tuft of ventral setae. Urosomite 3, produced as a large acute hook dorsally. Uropods 1‑2, rami not continuously setose to apex. Uropod 3, outer ramus, article 2 elongate, with 2 setae apically. Telson, deeply cleft, with 2 stout setae and variable simple setae on each lobe.

Description: Based on female (UERJ 426). Habitus as in Fig. 18A . Head ( Fig. 19A, B ), eyes rounded and medium‑sized; rostrum narrow and short, reaching apex of article 1 of antenna 1. Antenna 1 ( Fig. 19C ), peduncle article 1 about 1.3× longer than wide, ventral margin with 4 brush setae distally, dorsal apex with 1 seta; article 2, ventral margin with 5 long setae medially, dorsal margin with 1 short seta distally; article 3, short, ventral margin with 2 setae; primary flagellum 6‑articulate; accessory flagellum 5‑articulate. Antenna 2 ( Fig. 19D ), peduncle article 3, short and rounded, dorsal margin with 1 seta; article 4, stout setae formula:1‑3‑2‑3, ventral margin with long setae and 1 brush seta proximally, dorsal margin with 1 stout and 1 long seta medially; article 5, ventral margin with 3 long setae,facial margin with 2 stout setae medially and 5 long setae distally; flagellum 7‑articulate. Right mandible ( Fig. 19J ), molar as a small hump with 4 stout setae, incisor with 3 teeth, lacinia mobilis bifid, accessory setal row with 5 stout setae, palpar hump small; palp 3‑articulate, article 1 short, article 2 ordinary, article 3 slightly longer than article 2, apex oblique, with 7 medium to long setae. Maxilliped ( Fig. 19I ), inner plate with 1 stout seta apically and 4 setae; outer plate with 6 stout setae; palp, article 1 with 1 apicolateral setae, article 2, medial margin moderately setose, article 3, weakly setose, article 4, elongate, with medium apical nail, partially embedded.

Gnathopod 1 ( Fig. 20A ), coxa subrectangular, ventral margin with 10 setae; basis elongated, anterior margin with few short to long setae, posterior margin with 2 setae medially and 3 distally; ischium, small and subrectangular, posterior margin with 2 setae; merus, posterior margin with 5 setae; carpus, anterior margin with 1 seta distally; posterior margin moderately setose; propodus, anterior margin weakly setose, with a tuft of setae distally, posterior margin weakly setose; palm almost transverse, with setules, palmar hump small; dactylus reaching the palmar corner. Gnathopod 2 ( Fig. 20B ), coxa subrectangular,ventral margin with 9 setae; basis elongated, about 5× longer than wide, anterior margin with 2 setae, posterior margin with 2 setae medially and 3 distally; ischium, small and subrectangular, posterior margin with 2 setae; merus, posterior margin with 3 setae; carpus, anterior margin with 1 seta distally, posterior margin moderately setose; propodus, anterior margin setose distally, posterior margin weakly setose; palm almost transverse, with setules, palmar hump small, dactylus reaching the palmar corner. Pereopod 3 ( Fig. 21A ), coxa subrectangular, ventral margin with 6 setae; basis, posterior margin with 2 setae medially and distally; ischium, small and subrectangular, posterodistal corner with 2 setae; merus, anterior margin with 1 seta distally, posterior margin with long setae medially and distally, facial margin with a distal row of 6 setae; carpus, posterior margin with 7 long setae, facial margin with a medial row of 5 long setae; propodus, anterior margin with 1 short seta distally, posterior margin with 5 stout setae; dactylus, about 30% the length of propodus. Pereopod 4 ( Fig. 21B ), coxa subtriangular, ventral margin with 4 setae, posterodorsal margin weakly excavate; remaining articles are very similar to pereopod 3, differing only by some arrangements of setae. Pereopod 5 ( Fig. 21C ), coxa bilobate, posterior lobe with 6 setae; basis, anterior margin with some long and 2 stout setae, anterodistal corner with a row of 5 setae, posterior margin naked; ischium, small and subrectangular, anterodistal corner with a row of 6 setae; merus stout, slightly longer than wide, margins with medium to long setae, facial stout setae formula: 5‑3‑8‑4‑7‑4‑7; carpus stout, slightly longer than wide, margins with medium to long setae, facial stout setae formula:4‑1‑4‑5‑5‑5‑3; propodus, margins weakly setose, facial margin with 5 stout setae; dactylus, about 55% the length of propodus. Pereopod 6 ( Fig. 21D ), coxa, weak‑ ly expanded posteroventrally, with 2 setae; basis, anterior margin moderately setose, anterodistal corner with a row of 5 setae, posterior margin naked; ischium, small and subrectangular, anterodistal corner with 2 long setae; merus stout, slightly longer than wide, anterior margin moderately setose, posterior margin weakly setose, facial stout setae formula: 4‑6‑2‑4‑9; carpus stout, about 1.2× longer than wide, margins weakly setose, facial stout setae formula:4‑5‑4‑3‑3; propodus,margins weakly setose, facial margin with 6 stout setae; dactylus, about 25% the length of propodus. Pereopod 7 ( Fig. 21E ), coxa subtriangular, posteroventral margin with 2 setae; basis, about 1.3× longer than wide, posteroventrally expand‑ ed, reaching the half of carpus, anterior margin with 2 setae proximally and 1 distally, posterior margin serrate; ischium, small and subquadrate,anterodistal corner with 1 long seta; merus, anterodistal corner with 1 long seta; carpus, anterior margin with 1 seta distally, posterodistal corner with 2 long setae; propodus, posterior margin with 1 long seta distally; dactylus, about 60% the length of propodus.

Epimeral plate 1 ( Fig. 22A ), anterior margin weakly concave, anteroventral corner with 2 long plumose setae, ventral margin with 1 long plumose seta, posterior margin rounded, with 1 seta. Epimeral plate 2 ( Fig. 22B ), anterior margin concave, ventral margin with 5 long plumose setae, posterior margin with 2 setae. Epimeral plate 3 ( Fig. 22C ), anterior margin concave, ventral margin with 3 setae extending to facial margin, posteroventral corner subquadrate, posterior margin nearly smooth, with 3long setae. Urosomite 3, produced as a large acute hook dorsally. Uropod 1 ( Fig. 22D ), peduncle, about 2.3× longer than wide, dorsomedial and lateral margins with 1 distal stout seta each; outer ramus, slightly longer than inner, dorsal margin with 2 stout setae, bearing 1 subapical nail; inner ramus, dorsal margin with 1 stout seta, bearing 1 subapical nail. Uropod 2 ( Fig. 22E ), peduncle, about 2.5× longer than wide, dorsomedial margin with 2 stout setae, ventrolateral margin with 3 long stout setae; outer ramus slightly longer than inner, dorsal margin with 2 stout setae, bearing 1 apical nail; inner ramus, dorsal margin with 1 stout seta, bearing 1 apical nail. Uropod 3 ( Fig. 22F ), peduncle, about 1.6× longer than wide, ventroapical margin with 4 stout setae, dorsoapical corner with 1 short stout seta; outer ramus, 1.5× longer than inner, article 1, ventral margin with 2 acclivities and 2 stout setae on each, ventroapical corner with 2 stout setae, article 2, elongate, with 2 plumose setae apically; inner ramus, with 1 long plumose seta apically. Telson ( Fig. 22G ), about 85% cleft, apex rounded, apical margin with 1 brush and 2 stout setae on each lobe.

Sexual dimorphism: Based on male (UERJ 427). Body ( Fig. 18B ), smaller in size. Head ( Fig. 19G, H ) eyes, larg‑ er and more pigmented, rostrum narrow and short.

Antenna 1 ( Fig. 19E ), peduncle article 1, about 1.3× longer than wide, ventral margin with a row of setules and 1 brush seta distally, dorsal apex with 1 seta; article 2, ventral margin with 4 setae; article 3 short; primary flagellum 6‑articulate, with calceoli on articles 1‑2; accessory flagellum 6‑articulate. Antenna 2 ( Fig. 19F ), peduncle article 3, short, dorsal margin covered with setules; article 4, facial stout setae formula: 1‑3‑4‑3, ventral margin with medium to long setae, dorsal margin covered with setules, com 1 long seta medially; article 5, facial margin with 2 stout setae, ventral margin weakly setose, dorsal margin with 3 tufts of setules and 1 calceolous; flagellum 29‑articulate and 6 calceoli.

Gnathopods 1‑2 ( Fig. 20C, D ), subequal in size; basis shorter than in female.

Uropod 3 ( Fig. 22H ), peduncle, about 1.6× longer than wide,ventroapical margin with 6 stout setae, dorsoapical corner with 1 seta; outer ramus, slightly longer than inner, article 1, ventral margin with 2 acclivities and 2 stout setae on each, ventroapical corner with 2 stout setae, article 2, elongate, with 2 plumose setae apically; inner ramus, margins covered with long plumose setae.

Type locality: Punta Arenas, Chile (53°10′S, 70°54′W).

Remarks: Microphoxus cornutus is distributed along south and southeastern coast of South America.The species is already known from Brazilian waters, being record‑ ed for the state of São Paulo (Wakabara et al., 1991; Pires‑ Vanin et al., 1997; Valério‑Berardo et al., 2000; Arasaki et al., 2004; Muniz & Pires‑Vanin, 2005; Pires‑Vanin et al., 2014). This is the first record of the species for the Rio de Janeiro state coast. As reported by Alonso de Pina (2003a), it was possible to notice morphological variations among the collected individuals of Mi. cornutus in relation to characters such as: facial stout setae formula on articles 4‑5 of antenna 2; number of stout setae on peduncle and rami of uropods 1‑3; setation of epimeral plates 1‑3; number of lateral setae on telson.These variations may reflect the maturation stage of the individuals, being the juveniles with fewer groups and weak armaments of setae, and the adults with stronger armaments of stout setae.

Geographic distribution: Argentina: Ushuaia Bay ; Mar del Plata ; Golfo Nuevo; Golfo San José; El Rincón; Chubut; Río Negro ; Isla Monte León; Magellanic strait; and Beagle Channel. Brazil: municipalities of São Sebastião and Ubatuba, coast of São Paulo state ; and Rio de Janeiro state. Chile: Valparaíso Bay ; Puerto Montt; and Punta Arenas. Uruguay: north area (lat. aprox. 35°55′S) .

Bathymetric range: Shallow waters to 98 m depth.

Figures

Figure 18. Microphoxus cornutus (Schellenberg,1931): (A) Habitus of female (UERJ 426);(B) Habitus of male (UERJ 427).Scale bars:1.0 mm.

Figure 19. Microphoxuscornutus (Schellenberg,1931):(A) Female head inlateral view;(B)Female head indorsal view;(C) Female rightantenna 1; (D)Female right antenna2;(I) Left maxilliped;(J)Right mandible(UERJ 426);(E)Male rightantenna 1; (F) Male rightantenna2;(G) Male headindorsalview;(H)Male headinlateral view (UERJ 427).Scale bars:0.1 mm for I-J;0.2 mm for the remaining.

Figure 20. Microphoxus cornutus (Schellenberg, 1931): (A) Female right gnathopod 1; (B) Female right gnathopod 2 (UERJ 426); (C) Male right gnathopod 1; (D) Male rightgnathopod 2 (UERJ 427).Scale bars:0.2 mm.

Figure 21. Microphoxuscornutus (Schellenberg,1931),female (UERJ 426):(A) Right pereopod 3; (B) Right pereopod 4; (C) Right pereopod 5;(D) Right pereopod 6; (E) Right pereopod 7.Scale bars:0.2 mm.

Figure 22.Microphoxuscornutus(Schellenberg,1931):(A) Rightepimeralplate 1;(B)Right epimeralplate 2;(C) Rightepimeralplate 3;(D)Right uropod1; (E)Right uropod 2; (F) Female righturopod 3; (G) Telson (UERJ 426); (H) Male right uropod 3 (UERJ 427).Scale bars:0.2 mm for A-C;0.1 mm for the remaining.