Elasmopus helenae, Pereira & Andrade & Senna, 2022

Pereira, C. S. M., Andrade, L. F. & Senna, A. R., 2022, A new species of Elasmopus Costa (Amphipoda: Maeridae) from the coast of Rio de Janeiro state, southeastern Brazil, Invertebrate Zoology 19 (1), pp. 42-56 : 44-54

Elasmopus helenae sp.n.

urn:lsid:zoobank.org:act:E79A11D2-315A-476C-8C50-2A52E541B8C7

Figs 1–9 .

MATERIAL EXAMINED. Holotype:male, 10.5 mm length, dissected and drawn, Itaipu Beach , municipality of Niterói, Rio de Janeiro state, Brazil, 2– 3 m depth, 22°58′26″S 43°02′47″W, A. R . Senna and R. Sorrentino coll., 9 March 2018 , on algae ( UERJ 579 ) . Paratypes: 1 female, dissected and drawn, same sampling data ( UERJ 581 ); 2 males in 93% ethanol, same sampling data ( UERJ 580 ); 15 females and 2 males, in 93% ethanol, same sampling data ( UERJ 582 ); 11 females, in ethanol 93%, same sampling data ( UERJ 583 ); 1 male, in 93% ethanol, same sampling data ( UERJ 584 ); 1 female, in 93% ethanol, same sampling data ( UERJ 585 ); 58 individuals, in ethanol 93%, Boa Viagem Beach , municipality of Niterói, Rio de Janeiro state, Brazil, 1–2 m depth, 22°54′31″S 43°07′50″W, V . M. Cummings and R. Sorrentino coll., 18 July 2019 , on algae ( UERJ 1282 ); 29 individuals, in ethanol 93%, Boa Viagem Beach , municipality of Niterói, Rio de Janeiro state, Brazil, 1–2 m depth, 22°54′31″S 43°07′ 50″W, V . M. Cummings and R. Sorrentino coll., 18 July 2019 , on algae ( UERJ 1283 ) .

DIAGNOSIS. Antenna I with accessory flagellum of 2–3 articles. Gnathopod II palm bearing a dense fringe of plumose setae, with two processes, medial being almost subquadrate whereas subdistal being subtriangular but apically rounded. Pereopod VI basis posterior margin deeply castelloserrate along distal half. Pereopod VII basis posterior margin weakly serrate proximally and castelloserrate along distal half. Uropod I peduncle with two basofacial stout setae. Telson about 85% cleft, each lobe apically truncate with an apicolateral and an apicomesial cusp.

DESCRIPTION OF MALE. Based on male holotype ( UERJ 579 ) .

Habitus as in Fig 1 . Head ( Fig. 2A ) with reniform eyes, lateral cephalic lobe broad, rounded, distally truncated, with anteroventral notch and slit, anteroventral corner rounded.

Antenna I ( Fig. 2B ) about 1.8× longer than antenna II, moderately setose; peduncle segment 1 about 2.9× longer than wide, dorsal margin with one proximal stout seta and two distal slender setae, ventral margin setose, distally with two stout setae with accessory seta; peduncle segment 2 about 4.3× longer than wide, slightly longer than segment 1; peduncle segment 3 about 4× longer than wide, about 0.6× length of segment 2; primary flagellum 21- articulate; accessory flagellum ( Fig. 2C ) 2-articulate.

Antenna II ( Fig. 2D ) moderately setose; peduncle segment 1 ordinary (not drawn); peduncle segment 2 short, dorsal margin with two setae; peduncle segment 3 short, with two facial short stout setae; peduncle segment 4 dorsal margin with three sets of medium to long setae, ventral margin moderately setose; peduncle segment 5 dorsal margin with five sets of slender setae, ventral margin moderately setose; flagellum 7-articulate.

Upper lip ( Fig. 2H ) rounded, apically setulose. Lower lip ( Fig. 2G ) inner and outer lobes apically and facially setulose.

Right mandible ( Fig. 2E ) incisor apically bifid; lacinia mobilis apically bifid, with lateral margin multi-cuspidate; molar expanded, triturative, with a long plumose seta; accessory setal row with three stout multi-cuspidate setae; palp, segment 1 short, segment 2 about 2.2× longer than wide, ventral margin setose, bearing eight proximal slender setae and seven distal pectinate long setae, segment 3 falciform, about 2.8 × longer than wide, ventral margin setose, with a proximal row of minute setules, a medial row of pectinate setae and six slender long setae distally.

Left mandible ( Fig. 2F ) incisor with three apical spines; lacinia mobilis with four spines; molar triturative, with a long plumose seta; accessory setal row with four multi-cuspidate setae; palp segment 1 short, segment 2 about 2.7× longer than wide, ventral margin setose, bearing five proximal slender setae and 10 distal pectinate setae, segment 3 about 2.9× longer than wide, ventral margin setose.

Maxilla I ( Fig. 2J ) inner plate with two apical plumose setae, lateral and mesial margins slightly setulose; outer plate with eight apical stout setae, three of them multi-cuspidate, three bifid and two serrate; palp 2-segmented, segment 1 short, segment 2 about 1.9 × longer than wide, with 12 slender setae distally.

Maxilla II ( Fig. 2I ) inner plate mesial margin slightly setulose and with a row of 12 plumose setae extending apically, lateral margin with distal setules; outer plate slightly longer than inner plate, with 10 plumose apical setae, lateral margin distally setulose.

Maxilliped ( Fig. 2K ) inner plate bearing a facial row of nine plumose setae, mesial margin with five plumose setae; outer plate about twice longer than inner plate, mesial margin bearing nine stout setae, apical margin with six plumose setae; palp segment 2 about 3.5× longer than wide, mesial margin moderately setose, segment 3 weakly setose, 2.5× longer than wide, with a facial row of five slender setae, distal lobe produced and setulose, segment 4 narrow, with three apical slender setae; nail present, partially immersed.

Gnathopod I ( Fig. 3A ) coxa produced anteroventrally, ventral margin bearing nine slender setae. Carpus about 1.8× longer than wide, with 10 facial rows of plumose setae, posterior margin moderately setose, with plumose setae. Propodus with stout facial seta near dactylus insertion, with three facial rows of long plumose setae and four rows of pectinate setae; palm about 0.4× length of posterior margin, acute, with short pectinate setae on its margin. Dactylus inner margin with four short setae; nail present. Rest of limb as figured.

Gnathopod II ( Fig. 3B ) coxa ventral margin rounded with five setules and four setae. Carpus about 1.3× wider than long, posterior corner weakly produced, with eight setae. Propodus subovoid, tapering, with eight facial rows of slender setae laterally ( Fig. 3C ) and nine rows placed mesially ( Fig. 3D ); palm about 1.8× longer than posterior margin of propodus, densely setose with plumose setae, with two processes: medial is subquadrate, subdistal is subtriangular with rounded apex bearing three short stout setae decreasing in length. Dactylus elongated and curved. Rest of limb as figured.

Pereopod III ( Fig. 4A ) coxa subrectangular, ventral margin with 15 setae. Carpus 2.8× longer than wide, about 0.7× as the length of propodus, posterior margin with five setae. Propodus 4.9× longer than wide, posterior margin with six setae. Dactylus about 45% of the length of propodus, posterior margin with one short seta distally; nail present. Rest of limb as figured.

Pereopod IV ( Fig. 4B ) coxa ventral margin with 18 short setae, posterior margin weakly excavate. Carpus 2.3× longer than wide, about 0.6× as long as propodus, posterior margin with six setae. Propodus 4.4× longer than wide, posterior margin with eight setae. Dactylus about 40% of the length of propodus, anterior and posterior margins with one short seta each; nail present. Rest of limb as figured.

Pereopod V ( Fig. 4C ) coxa bilobated, posterior lobe with nine setae. Basis 1.2× longer than wide, posteriormarginweaklyserrate.propodus4.8×longer than wide, with five facial sets of stout setae (3-3-4- 4-2). Dactylus about 30% of the length of propodus, posterior margin finely combed, with a distal short seta; nail present. Rest of limb as figured.

Pereopod VI ( Fig. 5A ) coxa excavate ventrally, anterior margin with two setae, posteroventral margin bearing six setae. Basis 1.5× longer than wide, posterior margin castelloserrate on distal half, with weak posterodistal lobe bearing three slender setae. Propodus 5.5× longer than wide, with six facial sets of stout setae (2-3-4-4-3-3). Dactylus about 30% of the length of propodus, finely combed anteriorly and facially, anterior margin with four short setae, posterior margin with one plumose seta. Rest of limb as figured.

Pereopod VII ( Fig. 5B ) coxa ventral margin convex, weakly expanded posteriorly, posterior margin with four short setae. Basis 1.2× longer than wide, posterior margin castelloserrate along distal half. Propodus 5.1× longer than wide, with six facial sets of stout setae (2-3-3-4-4-2). Dactylus about 35% of the length of propodus, finely combed anteriorly and facially, anterior margin with three setules, posterior margin one plumose and one short slender seta. Rest of limb as figured.

Epimeral plate I ( Fig.6A ) ventral margin smooth, with three setae; posteroventral corner rounded; posterior margin slightly convex, with two setae.

Epimeral plate II ( Fig.6B ) anterior margin slightly concave; ventral margin smooth, with two sets of three setae; posteroventral corner subquadrate; posterior margin weakly crenulate.

Epimeral plate III ( Fig. 6C ) ventral margin with three sets of two setae each; posteroventral corner subquadrate; posterior margin weakly crenulate.

Uropod I ( Fig. 6D ) peduncle 3.9× longer than wide, with two stout basofacial setae, dorsolateral margin with six stout setae, dorsomedial margin with eight stout setae; outer ramus subequal in length to inner counterpart, with three marginal stout setae and four disposed apically; inner ramus with seven marginal and five apical stout setae.

Uropod II ( Fig. 6E ) peduncle 1.8× longer than wide, dorsolateral margin with 3 stout setae, dorsomedial margin with 3 serrate stout setae; outer ramus about 0.8× as long as inner ramus, with seven marginal stout setae and four disposed apically; inner ramus with six marginal and five apical stout setae.

Uropod III ( Fig. 6F ) peduncle 1.4× longer than wide, with one stout seta ventrally, dorsolateral margin with apical three stout setae, distoventral corner and dorsomedial margin with three stout setae each; outer ramus about 1.5× longer than inner ramus, apically truncated with ten stout setae, marginally with two sets of six and seven stout setae, respectively; inner ramus with two marginal stout setae and four disposed apically.

Telson ( Fig. 6G ) slightly wider than long, cleft to about 83% of the length, each lobe apically truncate with a lateral and a mesial cusp, bearing two long and two short stout setae, and a subapical short seta; dorsolateral margin with two short plumose setae on each side.

FEMALE ( Figs 7–9 ). Based on female paratype (UERJ 581). Mainly as male except for the following features: antenna I accessory flagellum ( Fig. 7B ) 3- articulate, being the last segment minute. Gnathopod II ( Fig. 7E ) propodus with palm margin devoid of outgrowths and much less setose than male counterpart. Oostegites ( Fig. 7B ) narrow with subparallel margins.

ETYMOLOGY. This species is named after the first author’s daughter, Helena.

TYPE LOCALITY. Itaipu Beach , municipality of Niterói, Rio de Janeiro state, Brazil .

Figures

Fig. 1. Elasmopus helenae sp.n., male holotype (UERJ 579): habitus. Scale bar: 2.0 mm. Рис. 1. Elasmopus helenae sp.n., голотип самец (UERJ 579): габитус. МасШтаб: 2,0 мм.

Fig. 2. Elasmopus helenae sp.n., male holotype (UERJ 579): A — head; B — antenna I; C — accessory flagellum of antenna I; D — antenna II; E — right mandible; F — left mandible; G — lower lip; H — upper lip; I — maxilla II; J — maxilla I; K — maxilliped. Scale bars: A, B, D — 0.5 mm; E, F — 0.2 mm; G, H, I, J — 0.1 mm; K — 0.3 mm. Рис. 2. Elasmopus helenae sp.n., голотип самец (UERJ 579): А — головной отдел; B — антенна I; C — добавочный жгутик антенны I; D — антенна II; Е — праваЯ нижнЯЯ челюсть; F — леваЯ нижнЯЯ челюсть; G — нижнЯЯ губа; Н — верхнЯЯ губа; I — максилла II; J —максилла I; К — максиллипед. МасШтаб: A, B, D — 0,5 мм; Е, F — 0,2 мм; G, Н, I, К, J— 0,1 мм; К — 0,3 мм.

Fig. 3. Elasmopus helenae sp.n., male holotype (UERJ 579): A — gnathopod I; B — gnathopod II; C — propodus of gnathopod II without setal fringe, lateral view; D — propodus of gnathopod II without setal fringe, mesial view. Scale bars: 0.5 mm. Рис. 3. Elasmopus helenae sp.n., голотип самец (UERJ 579): А — гнатопод I; B— гнатопод II; C — проподус гнатопода II беЗ краевых Щетинок, вид сбоку; D — проподус гнатопода II беЗ краевых Щетинок. МасШтаб: 0,5 мм.

Fig. 4. Elasmopus helenae sp.n., male holotype (UERJ 579): A — pereopod III; B — pereopod IV; C — pereopod V. Scale bars: 0.5 mm. Рис. 4. Elasmopus helenae sp.n., голотип самец (UERJ 579): А — переопод III; B — переопод IV; C — переопод V. МасШтаб: 0,5 мм.

Fig. 5. Elasmopus helenae sp.n., male holotype (UERJ 579): A — pereopod VI; B — pereopod VII. Scale bars: 0.5 mm. Рис. 5. Elasmopus helenae sp.n., голотип самец (UERJ 579): А — переопод VI; B — переопод VII. МасШтаб: 0,5 мм.

Fig. 6. Elasmopus helenae sp.n., male holotype (UERJ 579): A — epimeral plate I; B — epimeral plate II; C — epimeral plate III; D — uropod I; E — uropod II; F — uropod III; G — telson. Scale bars: A, B, C — 0.5 mm; D, E, F — 0.3 mm; G — 0.1 mm. Рис. 6. Elasmopus helenae sp.n., голотип самец (UERJ 579): А — ЭпимеральнаЯ пластинка I; B — ЭпимеральнаЯ пластинка II; C — ЭпимеральнаЯ пластинка III; D — уропод I; Е — уропод II; F — уропод III; G — тельсон. МасШтаб: А, В, С — 0,5 мм; D, E, F — 0,3 мм; G — 0,1 мм.

Fig. 7. Elasmopus helenae sp.n., female paratype (UERJ 581): A — antenna I; B — accessory flagellum of antenna I; C — antenna II; D — gnathopod I; E — gnathopod II. Scale bars: A, C — 0.5 mm; D, E — 0.3 mm. Рис. 7. Elasmopus helenae sp.n., паратип самка (UERJ 581): А — антенна I; B — добавочный жгутик антенны I; С — антенна II; D — гнатопод I; E — гнатопод II. МасШтаб: А, В — 0,5 мм; D, Е — 0,3 мм.

Fig. 8. Elasmopus helenae sp.n., female paratype (UERJ 581): A — Pereopod III; B — oostegite III; C — pereopod V; D — pereopod VII; E — pereopod VI. Scale bars: A, C, D, E — 0.5 mm; B — 0.2 mm. Рис. 8. Elasmopus helenae sp.n., паратип самка (UERJ 581): А — переопод III; B — оостегит III; С — переопод V; D — VII переопод; Е — переопод VI. МасШтаб: A, C, D, E — 0,5 мм; B — 0,2 мм.

Fig. 9. Elasmopus helenae sp.n., female paratype (UERJ 581): A — uropod I; B — uropod II; C — uropod III; D — telson. Scale bars: A, B, C — 0.2 mm; D — 0.1 mm. Рис. 9. Elasmopus helenae sp.n., паратип самка (UERJ 581): А — уропод I; B — уропод II; С — уропод III; D — тельсон. МасШтаб: А, В, С — 0,2 мм; D — 0,1 мм.