Segesta riograndensis Siegloch & Polegatto

Siegloch, Ana E., Polegatto, Cleber M. & Froehlich, Claudio G., 2006, Segesta riograndensis, new genus and species of an Atalophlebiinae (Ephemeroptera: Leptophlebiidae) mayfly from southern Brazil, Zootaxa 1299, pp. 35-43 : 38-41

Segesta riograndensis Siegloch & Polegatto n. sp.

Nymph, mature, female (in alcohol). Body length: 6mm; terminal filament: 7mm, cerci: about 6/7 of length of terminal filament; general coloration gray spotted.

Head. Dorsum of head orange­brown, with a narrow transverse dark brown band between ocelli extending to anterior base of eyes. Mouthparts: orange­brown, lighter in ventral surface; cardo and base of mandibles darker. Labrum ( Fig. 1 ): dorsal row of about 50 long fine setae, very close to anterior margin; a group of about 9 dorsal curved setae on each half. Mandibles as in figures 3–6. Maxillae ( Figs. 7–9 ): Cardo with about 6 short setae; stipes with minute basal posterior prominence on outer margin; anterior margin of galealacinia completely occupied by hard brush of setae; in ventral anteromedian area, about 15 pectinate setae, with apical comb, and one large pectinate setae with complete comb ( Fig. 9 ). Hypopharynx as in Fig. 10 . Labium as in Fig. 11 .

Thorax. Dorsum of thorax orange­brown with dark spots at anterior and posterolateral margins of pronotum, and at the base of fore wingpad. Pronotum with row of about 8 spine­like setae on anterolateral margin. Legs: Orange­brown, dorsal surface of coxae with small dark spots; ventral surface of fore femora with two basal gray spots and two other apical; ventral surface of middle and hind femora with an apical gray spot. Forelegs ( Fig. 13 ) with long fine setae on posterior margin of femora, and hard spatulate setae of various sizes, ca. 6 long, and ca. 14 short; short setae on anterior margin of femora and short spatulate setae on dorsal surface; long fine setae on posterior margin of tibiae and tarsi, and short spine­like setae on anterior margin of tibiae and tarsi; midlegs ( Fig. 14 ) similar to forelegs, but femora with ca. 8 long and ca. 3 short spatulate setae on femora; hindlegs ( Fig. 15 ) similar to those described before, but femora with ca. 8 long and ca. 14 short spatulate setae, and spatulate setae also on tibiae, ca. 6 long and 8 short. Tarsal claws ( Fig. 16 ) with small subequal denticles, about 6 apical and 6 basal; a big subapical denticle absent; apical denticle curved.

Abdomen. Gray spotted, as in Fig. 17 . Margin of tergum 5 as in Fig. 19 . Shape of caudal filaments as in Fig. 18 .

Nymph, mature, male. Eye. Lower portion black, upper portion orange­brown. Body length 6,3mm.

Adults: unknown.

Material examined: Holotype, female nymph, Brazil, State of Rio Grande do Sul, Independência, Santa Rosa River, A.E. Siegloch, I.2005, deposited at MZSP. Paratypes, 7 nymphs; 2 nymphs same data as holotype, but 1 male and 4 female, XIII.2005; 1 male and 2 female deposited in MZSP, and 4 female at MSNZRS.

Geographical distribution: The type­species was collected in northwestern Rio Grande do Sul, southern Brazil. There is also a record of a similar nymph (undescribed) for Nova Xavantina, State of Mato Grosso, western Brazil.

Habitat: The nymphs were found on rocks and stones in the river, at an altitude of about 300 m.

Etymology: The epithet riograndensis refers to State of Rio Grande do Sul, where the species was collected.

Figures

FIGURES 1 – 12. Segesta riograndensis n. sp.: 1, labrum, left dorsal view, right ventral view. 2, anteromedian emargination of labrum; 3, left mandible, dorsal view. 4, right mandible, dorsal view. 5, right mandible, partial, ventral view. 6, mandibles details; left and right incisors and prostheca. 7, maxillae, ventral view. 8, maxillary palp, detail, dorsal view. 9, pectinate setae of galealacinia, ventral view. 10, hypopharynx, left ventral view, right dorsal view. 11, labium, left ventral view, right dorsal view, some setae omitted. 12, segment 3 of labial palp.

FIGURES 13 – 16. Segesta riograndensis n. sp.; 13, foreleg. 14, midleg. 15, hindleg. Legs in dorsal view. 16, Tarsal claw.

FIGURES 17 – 20. Segesta riograndensis n. sp.; 17, abdomen with color pattern. 18, base of caudal filaments. 19, posterior margin of tergum 5. 20, gill of first abdominal segment.