Cymadusa rasae, Andrade, Luiz F. & Senna, André R., 2017

Andrade, Luiz F. & Senna, André R., 2017, Four new species of Cymadusa Savigny, 1816 (Amphipoda: Ampithoidae) and new records of C. filosa Savigny, 1816 from Brazilian coast, Zootaxa 4226 (3), pp. 359-389 : 367-373

Cymadusa rasae sp. nov.

( Figs 5–8 )

Etymology. The specific epithet was given after the Rasa Beach, which is located the type-locality of the new species.

Material examined. Holotype, male, dissected and drawn, 7.7 mm, 16 January 2000, Rasa Beach, municipality of Armação dos Búzios, Rio de Janeiro state, Brazil, P.S. Young, C. Serejo, col., without depth and substrate information, UFBA 1616 . Paratypes: 1 female, dissected and drawn, 10.2 mm, 16 January 2000, Rasa Beach, municipality of Armação dos Búzios, Rio de Janeiro state, Brazil, P.S. Young, C. Serejo, col.,without depth and substrate information, MNRJ 13549 .

Diagnosis. Antenna 1, accessory flagellum 1-articulate. Antenna 2 weakly setose.Lower lip setose. Mandible, palp 3-articulate. Maxilla 1, inner plate with 5 setae.Gnathopod 1, merus small and subacute; carpus elongated and subrectangular. Gnathopod 2 with setose margins; merus elongated and subrectangular; carpus subtriangular; palm with a small and subacute posterodistal spine. Uropod 3, peduncle with 4 distal stout setae and 6 simple setae, lateral margin with 1 pectinated long seta.

Description. Based on holotype, male, 7.7 mm, UFBA 1616.Head, eyes rounded and well developed. Antenna 1 weakly setose; flagellum 28-articulate; accessory flagellum 1-articulate. Antenna 2 weakly setose; flagellum 20- articulate; article 4 with row of long plumose setae ventrally. Upper lip rounded, setose apically and laterally. Lower lip notched, inner and outer lobes setose apically and marginally. Right mandible, molar triturative with 2 long setae; incisor and lacinia mobilis multicuspidate; accessory setal row with 5 stout multicuspidate setae. Left mandible, molar triturative with 1 long setae and few short setae; incisor and lacinia mobilis multicuspidate, accessory setal row with 5 stout multicuspidate setae; palp 3-articulate, article 1 about 2.4 × longer than wide, article 2 about 3.5 × longer than wide, article 3 about 4.6 × longer than wide with 8 long plumose setae apically. Maxilla 1, inner plate small and subrectangular, inner margin with 5 long plumose setae; outer plate with 6 stout multicuspidate setae apically; palp 2-articulate, inner margin with 1 long setae, facial margin with 2 long setae, outer margin with 2 long pectinate setae, apical margin with 7 stout setae. Maxilla 2, inner plate about 3 × longer than wide, inner and apical margin with row of long setae; outer plate longer than inner plate, about 2.6 × longer than wide, inner margin with 4 long setae, outer margin with row of tiny setae, apical margin covered with tiny setae and twelve long setae. Maxilliped, inner plate about 3.5 × longer than wide, inner and facial margins with long plumose setae, apical margin with 2 stout setae and 8 long plumose setae; outer plate about 1.9 × longer than wide, inner margin with eleven stout setae, outer margin with 2 long plumose setae and partially covered with tiny setae, apical margin with 3 stout setae, 2 long plumose setae and 2 long setae; palp 4-articulate, about 1.7 × longer than outer plate, article 1 subtriangular, article 2 subrectangular, inner margin with 11 long setae, apical margin with 3 long setae, article 3 subrectangular, inner margin with 7 long plumose setae and 2 long pectinate setae, outer margin with 1 long setae, facial margin with 4 long plumose setae, apical margin with 3 long plumose setae and 1 long pectinate setae, article 4 with both short and tiny setae, nail present.

Gnathopod 1, smaller than gnathopod 2; coxa produced anteriorly, ventral margin with simple setae and plumose setae; basis 2.9 × longer than wide, margins with few setae; ischium small and subrectangular, 1.3 × longer than wide, posteroventral angle with 2 setae; merus 1.9 × longer than wide, posterior margin with 10 setae; carpus 1.8 × longer than wide, anterodistal angle with 3 setae, posterior and lateral margins with long setae; propodus 1.8 × longer than wide, all margins bearing both short and long setae; palm acute; dactylus 1.4 ×longer than palm, serrated. Gnathopod 2, strongly setose on carpus and propodus; coxa subrectangular, ventral margin setose with long plumose setae; basis 2.7 × longer than wide, anterior margin with row of long plumose setae, posterior margin with few setae, lateral margin with eleven long plumose setae; ischium small and subrectangular, 1.1 × longer than wide, posterior margin with 2 short setae; merus 2.3 × longer than wide, posterior margin with 2 setae and 8 long pectinate setae, lateral margin with 5 long setae; carpus 1.1 × longer than wide, anterior and lateral margins setose with long plumose setae, posterior margin setose with long pectinate setae; propodus 1.4 × longer than wide, anterior margin setose with long plumose setae, posterior margin setose with long setae and 1 stout setae; palm acute, slightly concave; dactylus 1.4 ×longer than palm, serrated. Pereopod 3, coxa subrectangular, ventral margin with plumose setae; basis 2.3 × longer than wide, anterior margin with 9 long setae, posterior margin with 13 setae, posteroventral angle with 2 short setae, lateral margin with 4 setae; ischium small and subrectangular, 1.2 × wider than long, posteroventral angle with 3 setae; merus 1.5 × longer than wide anterior and posterior margins with few setae; carpus 1.7 × longer than wide, anterior margin with 3 setae, posterior margin with thirteen setae; propodus 3.1 × longer than wide, anterior and posterior margins with few setae; dactylus slightly curved, posterior margin with 3 setae. Pereopod 4, coxa subrectangular, ventral margin with long plumose setae; basis 2.1 × longer than wide, anterior margin with 3 long setae, posterior margin with long setae; ischium small and subrectangular, slightly wider than long, posteroventral margin with 3 setae; merus 1.3 × longer than wide, anterodistal angle with 4 setae, posterior margin with long setae; carpus 1.8 × longer than wide, anterior margin with 3 setae, posterior margin with 9 long setae; propodus 2.7 × longer than wide, anterior margin with 8 setae, posterior margin with 9 long setae; dactylus slightly curved. Pereopod 5 coxa, ventral margin with long plumose setae. Pereopod 6, coxa small and subrectangular, ventral margin with 5 short setae; basis 1.5 × longer than wide, anterior margin with 3 short setae and 3 stout setae, posterior margin with 7 short setae and 2 stout setae with accessory setae; ischium small and subrectangular, 1.1 × wider than long, anterior margin with 3 setae; merus 2.6 × longer than wide, anterior and posterior margins with setae; carpus 2.6 × longer than wide, anterior margin with setae, anterodistal angle with 1 stout setae and 9 long setae, posterior margin with 3 setae, posteroventral angle with 6 setae; propodus 5.5 × longer than wide, anterior margin with 4 stout setae with accessory setae, 2 stout setae and fourteen long setae, posterior margin with fourteen long setae; dactylus curved. Pereopod 7, basis 1.5 × longer than wide, anterior margin with 3 stout setae with accessory setae and 4 short setae, posterior margin with 3 stout setae and eleven short setae; ischium small and subrectangular, 1.2 × wider than long, anterior margin with 3 setae; merus 2.3 × longer than wide, anterior margin with 4 setae, anterodistal angle with 7 setae, posterior margin and posteroventral angle with 4 setae each; carpus 2.3 × longer than wide, anterior margin with 6 setae, anterodistal angle with 7 setae, posterior margin with 3 setae, posteroventral margin with 4 setae; propodus 5 × longer than wide, anterior margin with 6 stout setae with accessory setae and twelve long setae, posterior margin with setose with long setae, posteroventral angle with a tuft of long setae; dactylus curved.

Epimeral plate 1 rounded, ventral margin with a short and acute projection. Epimeral plate 2, ventral margin rounded, posteroventral corner with a short and blunt projection. Epimeral plate 3, ventral margin rounded, posteroventral corner with a short and acute projection. Uropod 1, peduncle with long and acute distoventral spine (spur); peduncle 2.6 × longer than wide, dorsal margin with 5 stout setae with accessory setae, dorsolateral margin with 4 stout setae with accessory setae and 2 stout setae; inner ramus 1.1 × longer than outer ramus, dorsal margin with 3 stout setae, dorsolateral margin with 2 stout setae with accessory setae, apical margin with 2 stout setae with accessory setae and 2 stout setae; outer ramus, dorsal margin with 1 stout setae with accessory setae and 1 stout setae, dorsolateral margin with 4 stout setae with accessory setae, apical margin with 2 stout setae with accessory setae and 3 stout setae. Uropod 2, peduncle 2.5 × longer than wide, dorsal and dorsolateral margin with 2 stout setae each; inner ramus 1.1 × longer than outer ramus, dorsal margin with 3 stout setae, apical margin with 2 stout setae with accessory setae and 3 stout setae; outer ramus, dorsal and dorsolateral margin with 3 stout setae each, apical margin with 1 stout setae with accessory setae and 4 stout setae. Uropod 3, peduncle 1.9 × longer than wide, with 3 stout setae, 1 stout setae with accessory seta and 5 long setae distally, dorsal margin with 1 stout setae, dorsolateral margin with 1 long pectinate seta, 1 stout setae and 2 long setae; inner ramus 1.3 × longer than outer ramus, dorsal margin with 1 stout setae, apical margin with 1 stout setae with accessory setae, 2 stout setae and 4 long setae; outer ramus, dorsolateral margin with 1 stout seta with accessory seta and 1 long seta, apical margin with 2 curved stout setae. Telson suboval,apical margin with 6 setae and 2 short setae, dorsolateral margins with 2 setae each.

Sexual dimorphic characters. Based on paratype, female, 10.2 mm, MNRJ 13549. Gnathopod 1, smaller than gnathopod 2; coxa subrectangular, slightly produced anteriorly, ventral margin setose; basis 2.9 × longer than wide, margins with few setae; ischium small and subrectangular, 1.1 × longer than wide, posteroventral angle with 4 setae; merus 1.6 × longer than wide, posterior margin with 10 long pectinate setae; carpus 1.9 × longer than wide, anterodistal angle with 4 pectinate setae, posterior margin setose with pectinate setae, facial margin with long setae; propodus 1.8 × longer than wide, anterior margin with few setae, posterior margin setose with 1 robust setae with accessory setae; palm acute; dactylus 1.2 × longer than palm, serrated. Gnathopod 2, weakly setose; coxa subrectangular, ventral margin with long setae; basis 2.8 × longer than wide, with few setae; ischium small and subrectangular, slightly longer than wide, posteroventral angle with 3 setae; merus 2.2 × longer than wide, posterior margin with long setae; carpus 1.1 × longer than wide, anterodistal angle with 6 setae, posterior margin setose with long pectinate setae; propodus 1.5 × longer than wide, anterior and posterior margins setose; palm acute, slightly concave, palmar spine present; dactylus 1.4 × longer than palm, serrated, with a tiny plumose setae anteriorly.

Remarks. We have only 2 specimen of the new species and the pereopod 5 on both individuals are missing. Cymadusa rasae sp. nov. presents more shortened and robust articles of pereopods 3–4 than in other species of the genus. The new species resembles C. wistari by the following characters: weakly setose articles in appendages; gnathopod 2, margins covered with long plumose setae, carpus longer than propodus. However, C. rasae sp. nov. can be distinguished from C. wistari by the following characters ( C. wistari characters in parenthesis): epimeral plate 3 posteroventral corner with a short and acute projection (broadly rounded); uropod 3, peduncle, dorsolateral margin with long setae (long setae present only distally).

Cymadusa rasae sp. nov. presents the following distinct and unique combination of characters in the genus: gnathopod 1 merus small and subacute, carpus elongated and subrectangular; gnathopod 2 merus elongated and subrectangular, carpus subtriangular, palm with a small and subacute posterodistal spine; uropod 3, peduncle, dorsolateral margin with 1 long pectinated setae.

Distribution. Known only to the type-locality, Rasa Beach, municipality of Armação dos Búzios, Rio de Janeiro state, Brazil.

Figures

FIGURE 5. Cymadusa rasae sp. nov. Holotype, male, 7.7 mm, UFBA 1616, Rasa Beach, municipality of Armação dos Búzios, Rio de Janeiro state, Brazil. Scale bars: 0.5 mm for A 1 – 2 and Hd; 0.1 mm for UL and Mx 1; 0.2 mm for the remainder.

FIGURE 6. Cymadusa rasae sp. nov. Holotype, male, 7.7 mm, UFBA 1616, Rasa Beach, municipality of Armação dos Búzios, Rio de Janeiro state, Brazil; paratype, female, 10.2 mm, MNRJ 13549, Rasa Beach, municipality of Armação dos Búzios, Rio de Janeiro state, Brazil. Scale bars: 1.0 mm for fGn 1; 0.5 mm for the remainder.

FIGURE 7. Cymadusa rasae sp. nov. Holotype, male, 7.7 mm, UFBA 1616, Rasa Beach, municipality of Armação dos Búzios, Rio de Janeiro state, Brazil. Scale bars: 1.0 mm for P 6 – 7; 0.5 mm for the remainder.

FIGURE 8. Cymadusa rasae sp. nov. Holotype, male, 7.7 mm, UFBA 1616, Rasa Beach, municipality of Armação dos Búzios, Rio de Janeiro state, Brazil. Scale bars: 0.1 mm for T; 0.2 mm for the remainder.