(Ephemeroptera: Baetidae) in Brazil

Zootaxa 2560: 16–28 (2010) www.mapress.com / zootaxa/

ISSN 1175-5326 (print edition)

Article

Copyright © 2010 · Magnolia Press

ZOOTAXA ISSN 1175-5334 (online edition)

The genus Americabaetis Kluge (Ephemeroptera: Baetidae) in Brazil: new species, stage description, and key to nymphs F.F. SALLES1,5, E.A. RAIMUNDI2, R. BOLDRINI3 & G. M. SOUZA-FRANCO4 1

Depto. de Ciências Agrárias e Biológicas, Centro Universitário Norte do Espírito Santo, Universidade Federal do Espírito Santo, CEP 29.932–540, São Mateus, ES, Brazil. E-mail: [email protected] 2 Programa de Pós-Graduação em Ciências Ambientais, Laboratório de Pesquisa em Ecologia e Química, Área de Ciências Exatas e Ambientais, Universidade Comunitária da Região de Chapecó, CEP 89.809–000, Chapecó, SC, Brazil. E-mail: [email protected] 3 Divisão de Curso de Entomologia (DCEN), Instituto Nacional de Pesquisas da Amazônia (INPA), CEP 69011-970 Manaus, AM, Brazil. E-mail: [email protected] 4 Programa de Pós-Graduação em Ciências Ambientais, Área de Ciências Exatas e Ambientais, Universidade Comunitária da Região de Chapecó, CEP 89.809-000, Chapecó, SC, Brazil. E-mail: [email protected] 5 Corresponding author

Abstract In the present work based on material from several areas in Brazil, the species of Americabaetis represented in the country are revised. A new species, A. mecistognathus, sp. nov., is described based on nymphs from Santa Catarina, the male adult of A. labiosus Lugo-Ortiz & McCafferty is described, a key to the nymphs of the South American species is provided, whereas comments regarding the taxonomy and habitat distribution of the Brazilian species are presented. Key words: mayfly, taxonomy, Neotropics, South America, macroinvertebrate

Introduction When originally described, Americabaetis Kluge, 1992 was erected as a subgenus of Baetis Leach, 1815 and included a single species from Cuba (Kluge 1992). Later Lugo-Ortiz and McCafferty (1996) revised the genus; they transferred a few species previously assigned to Acerpenna Waltz and McCafferty, 1987 to Americabaetis, and described several new species from South America. Studies such as Hoffman et al. (1999), Lugo-Ortiz and McCafferty (1999), Waltz and McCafferty (1999), Wiersema and McCafferty (1999), Salles et al. (2004), and Salles and Boldrini (2008) increased considerably the knowledge of the genus; to date 18 species are recognized. A key to the Neotropical and South American species known at the nymphal stage has been proposed respectively by Waltz and McCafferty (1999) and Domínguez et al. (2006), whereas a key to the adults has been proposed by Salles and Boldrini (2008). In the present paper, based on material mainly from Eastern Brazil, we present a review from the species encountered in the country. A distinctive new species, A. mecistognathus, sp. nov., is described based on nymphs from the state of Santa Catarina; the male adult of A. labiosus Lugo-Ortiz and McCafferty is described; a key to the nymphs of the South American species is provided; whereas comments regarding the taxonomy and habitat distribution of the Brazilian species are presented.

Material and methods The taxonomic descriptions presented herein were generated from a DELTA (Dallwitz 1980) database of South American baetid genera and species under development in order to propose a standard description for members of the family.

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Accepted by M. Hubbard: 12 Jul. 2010; published: 6 Aug. 2010

Pictures were taken using an OPTON Q719K-AC microscope with a TA-0124S digital camera, or a Zeiss STEMI 2000-C stereomicroscope with a Nikon ED digital camera. In the case of pictures taken at the stereomicroscope, a series of partially focused images were processed with the program Combine Z to produce final images with enhanced quality. The material examined is housed in the following institutions: Invertebrate Collection of the Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Brazil, Entomological Collection of the Universidade Federal do Espírito Santo (UFES), Vitória, Brazil, and Collection of the Laboratório de Diversidade de Insetos Aquáticos of the Universidade Federal do Espírito Santo (CEUNES), São Mateus, Brazil. Abbreviations for the name of the collectors are given as follows: CNF, Cesar N. Francischetti; EAR, Erikcsen A. Raimundi; FFS, Frederico F. Salles; NH, Neusa Hamada; RB, Rafael Boldrini. Except when noted, the material examined is based on nymphs.

Results Americabaetis Kluge, 1992 Baetis (Americabaetis) Kluge, 1992: 18. Genus 1 nr Pseudocloeon Roback, 1966: 134. Acerpenna Waltz & McCafferty, in part: Lugo-Ortiz & McCafferty, 1994: 66. Americabaetis Lugo-Ortiz & McCafferty, 1996: 157; Lugo-Ortiz & McCafferty, 1999: 260; Domínguez et al., 2006: 66.

Diagnoses. The genus was adequately characterized by Lugo-Ortiz and McCafferty (1996) and later by Domínguez et al. (2006). Herein we add one important character regarding the nymphal stage which has been observed in all Brazilian species as well as in an unidentified species from Central America: the shape of the lateral branch of the epicranial suture. In most baetids they are straight or curved, while in Americabaetis they are sinuous, somewhat similar to those of the genus Baetodes Needham & Murphy, and can be very useful when identifying nymphs of the family (see Figs. 2, 18 and 19). Other characteristic that can be emended to the nymphal diagnoses is the presence of scales and/or scale bases over body. Nymphs (modified from Domínguez et al. 2006): 1) Lateral branch of epicranial suture sinuous; 2) mandibles with setae between prostheca and mola, incisors fused apically, and prostheca robust with denticles apically; 3) maxillary palp two-segmented; 4) glossa with a row of long spine-like setae, paraglossae rectangular with 3 rows of long spine-like setae, segment II of labial palp with a distomedial projection; 5) tarsal claws with a single row of denticles; 6) hind wing pads absent; 7) abdominal gills present on segment II–VII; 8) scales and/or scale bases over body. Male imagos (modified from Domínguez et al. 2006): 1) Dorsal portion of turbinate eyes ellipsoidal; 2) forewings with paired (seldom single) marginal intercalary veins; 3) hind wings absent; 4) genitalia with forceps three-segmented, segment III elongate.

Americabaetis mecistognathus Salles & Raimundi, sp. nov. (Figs. 1a, 2–13, 27) Diagnoses. Nymphs: 1) frontal keel absent (Fig. 2); 2) lingua broadly pointed apically (Fig. 6); 3) glossa 0.6x length of paraglossa (Fig. 8); 4) apex of paraglossa with rows of pectinate setae (Fig. 8); 5) segment II of labial palp with a moderate distomedial projection (Fig. 8); 6) posterior margin of abdominal terga with rounded spines (Fig. 11); 7) mouthparts unusually elongate (Fig. 2). Adults: unknown. Description. Nymph. Length of body: 4.0 mm; cerci, terminal filament, and antennae: broken-off in mature nymphs.

THE GENUS AMERICABAETIS IN BRAZIL

Zootaxa 2560 © 2010 Magnolia Press ·

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FIGURE 1. Distribution of the species of Americabaetis in Brazil. Fig. 1b, map of Brazil; Figs. 1a, c–e, partial map of Brazil. a) A. mecistognathus, sp. nov.; b) A. alphus; c) A. labiosus; d) A. longetron; e) A. titthion. (Question mark indicates that a species is reported to a state, but the exact location is unknown; grey mark indicates record based on literature, white mark indicates new record. AL, Alagoas; BA, Bahia; ES, Espírito Santo; GO, Goiás; MG, Minas Gerais; MT, Mato Grosso; PR, Paraná; RJ, Rio de Janeiro; RS, Rio Grande do Sul; SC, Santa Catarina; SE, Sergipe; SP, São Paulo).

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· Zootaxa 2560 © 2010 Magnolia Press

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FIGURES 2–8. Americabaetis mecistognathus, sp. nov. Nymph. 2. Head (f.v.); 3. Labrum (left d.v., right v.v.); 4a. Left mandible (d.v.); 4b. Left mandible, detail of incisors and prostheca; 5a. Right mandible (d.v.); 5b. Right mandible, detail of incisors and prostheca. 6. Hypopharynx (d.v.); 7. Maxilla (v.v.); 8. Labium (left d.v, right v.v.).



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FIGURES 9–13. Americabaetis mecistognathus, sp. nov. Nymph. 9. Fore leg: a, posterior surface; b, detail of tarsal claw; 10. Abdominal color pattern; 11. Posterior margin of terga IV; 12. Gill IV: a, dorsal surface, b, detail of outer margin; 13. Paraproct (d.v.).

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Head. Coloration brown. Antenna light brown, scape and pedicel darker. Lateral branch of epicranial suture curved. Frontal keel absent. Antenna with scape and pedicel subcilindrical. Labrum (Fig. 3). Rectangular, longer than broad; length about 1.4x maximum width. Distal margin with medial emargination and small process; dorsally with few short, fine, simple setae scattered over surface. Dorsolateral arc of setae composed of 3 + 2 + 1 long, spine-like setae. Submarginal dorsal row of setae absent. Antero-lateral margin with long, pectinate setae. Ventrally with submarginal row of setae composed of row of short, bifid setae. Ventral surface with short, spine-like setae near anterolateral margin. Left mandible (Fig. 4). Incisors fused; inner and outer set of incisors respectively with 4 + 3 denticles; prostheca robust, apically denticulate and with comb-shape structure at apex. Margin between prostheca and mola straight, with crenulations on distal half, tuft of setae present. Subtriangular process wide, above level of area between prostheca and mola. Denticles of mola not constricted. Tuft of setae at apex of mola present, reduced to a single setae. Right mandible (Fig. 5). Incisors fused; inner and outer set of incisors respectively with 4 + 4 denticles. Prostheca robust, apically denticulate. Margin between prostheca and mola straight; tuft of setae present. Tuft of spine-like setae at base of mola present. Denticles of mola not constricted. Tuft of setae at apex of mola present, reduced to a single setae. Hypopharynx (Fig. 6). Lingua longer than superlingua; apex of lingua broadly acute. Superlingua not expanded; short, fine, simple setae scattered over lateral and distal margin. Maxilla (Fig. 7). Crown of galea-lacinia with 4 denticles; inner dorsal row of setae with 3 denti-setae. Medial protuberance of galea with 4 + 1 simple setae. Maxillary palp 3/4 length of galea-lacinia, with long, fine, simple setae scattered over surface. Palp segment II 1.2x length of segment I. Labium (Fig. 8). Glossa basally broad, narrowing apically and shorter than paraglossa; 0.6x length of paraglossa; inner margin with 7 spine-like setae, outer margin with 6 long spine-like setae increasing in length distally. Paraglossa sub-rectangular; apex with 3 rows of apically pectinate setae. Labial palp with segment I 0,6x length of segments II and III combined; segment I covered with short, simple setae on outer and inner margins and micropores basally; segment II with small distomedial protuberance (distomedial protuberance 0.4x width of base of segment III); inner margin with short simple setae, more numerous at apex; outer margin with few, short, simple setae; dorsally with row of 5 fine and simple setae; segment III conical; length 1,4x width; covered with spine-like and fine, simple setae. Thorax. General coloration brown with light brown marks. Foreleg (Fig. 9). Coloration brown. Ratio of foreleg 1.4:1.0:0.7:0.3. Forefemur. Length about 3x maximum width; dorsally with row of long blunt setae (in lateral view they look like spine-like setae); (length of setae about 0.1x maximum width of femur). Apex rounded and with blunt setae. Ventrally with short spinelike setae and micropores. Tibia. Dorsally with a row of scarce, short, fine, simple setae; ventrally with one row of spine-like setae. Tibio-patelar suture present. Tarsus. Dorsally with scarce short simple setae; ventrally with one row of spine-like setae. Tarsal claw with one row of 15 denticles. Mid and hind legs similar to foreleg. Abdomen. General coloration brown. Segments I and IV with posterior medial white mark; distal 2/3 of segment VII and segment X white; segments II to VII with lateral white longitudinal marks; segments II to VI, VIII and IX sublaterally washed with reddish brown (Fig. 10). Terga (Fig. 11). Surface with abundant scales or scale-bases. Posterior margin with rounded spines. Gills (Fig. 12). On segments II – VII. Margin with narrow spines intercalating short, fine, simple setae; tracheae extending from main trunk to inner and outer margins. Paraproct (Fig. 13). With 8 marginal spines; surface with scale or scale-bases; postero-lateral extension with minute marginal spines. Caudal filaments. Coloration brown. Terminal filament 0.7–0.8x length of cerci. Posterior margin of segments with short spines on each segment. Inner margin of cercus and inner and outer margin of terminal filament with tufts of long, simple setae. Comments. Nymphs of the new species were found exclusively at the Rio Chapecozinho (Fig. 26), a relatively wide river (around 60 meters) with a riverbed formed by a flat basaltic slab covered in most areas by algae and hydrophytes (Podostemaceae) and few allochthonous vegetation. The nymphs were found inhabiting the vertical surface of the riverbed, always associated to hydrophytes and moderate to fast current. The altitude at the type locality is 1031 meters above the sea level (m.a.s.l.). THE GENUS AMERICABAETIS IN BRAZIL


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The new species shares several characteristics with A. titthion and A. labiosus, as the absence of a frontal keel, setae at the apex of paraglossa pectinate, legs robust, spines at the posterior margin of terga blunt to rounded, poorly developed distomedial process of labial palp segment II, and, in the case of A. mecistognathus, sp. nov. and A. labiosus, elongate labium. Nevertheless, in the new species all mouthparts are distinctly elongate. In a general aspect, the mouthparts are nearly as long as the head capsule, which clearly distinguishes A. mecistognathus, sp. nov. from its congeners. Etymology. From the Greek words mecist, longest, and gnathus, jaws. An allusion to the unusual elongate mouthparts. Distribution. BRAZIL: Santa Catarina (Fig. 1a). Material examined. HOLOTYPE: Nymph, SANTA CATARINA, Passos Maia, Rio Chapecozinho, S 26°46'1.66" / W 51°49'49.79", 1031 m.a.s.l., 13/iii/2009, pedra em remanso, FFS, EAR cols. (UFES). PARATYPES: same data as holotype [4 nymphs, 2 at CEUNES (one mounted on slides), 2 at INPA].

Americabaetis alphus Lugo-Ortiz & McCafferty, 1996 (Figs. 1b, 20, 23, 24, 28) Americabaetis alphus Lugo-Ortiz & McCafferty, 1996: 163; Francischetti et al., 2003: 69; Salles et al., 2004: 2; Domínguez et al., 2006: 69; Salles et al., 2010: 302.

Diagnoses. Nymphs: 1) frontal keel present; 2) lingua pointed apically; 3) glossa 0.8x length of paraglossa; 4) apex of paraglossa with rows of simple setae; 5) segment II of labial palp with a strong distomedial projection; 6) posterior margin of abdominal terga with pointed spines. Male imago: 1) turbinate eyes uniformly and widely separated from each other, upper surface ellipsoidal; 2) forceps with first segment not constricted medioapically; 3) posterior margin of subgenital plate without a small rounded projection; 4) length of body relatively small (less than 5.0 mm). Distribution. ARGENTINA, BOLIVIA, CHILE, PARAGUAY, BRAZIL: Rio Grande do Sul, Santa Catarina, Paraná, Minas Gerais, São Paulo, Rio de Janeiro, Espírito Santo, Mato Grosso, Bahia. NEW RECORDS: Pernambuco, Sergipe, Goiás, Amazonas (Fig. 1a). Comments. Americabaetis alphus is probably the species of Ephemeroptera with the widest distributional range in South America, as well as one of the most abundant, at least in Brazil. Their nymphs are found in several biomes and on small streams to large rivers, often associated with marginal vegetation and leaf litter in areas with slow to moderate current (Fig. 28). The altitudinal range of this species is also highly variable, specimens were found from the sea level to 1900 m.a.s.l. They were also encountered in pristine to moderately impacted streams, demonstrating that the species is somewhat tolerant, what, in turn, would explain its wide distribution. Material examined. ALAGOAS, Rio Largo, Afluente do Rio Mandaú, "Lajeiro", S 09°28.496'/W 35°52.303', Vegetação marginal, 15/iii/2004, CNF COL. (UFVB); SERGIPE, Japaratuba, Rio da Prata, S 10°37.764'/W 36° 55.451', Vegetação marginal, 18/iii/2004, muitos, CNF COL. (UFVB); GOIÁS, Corumbá de Goiás. Corredeira da Igreja Presbiteriana, acima da calheira, S 15°49’37.1’’/W 48°46’34.8’’, 26/vi/2003, NH COL. (INPA); BAHIA, Correntina. Rio do Mucambo, S 13°16’45.4’’/W 44°33’52.0’’, pedras roladas em correnteza, 03/viii/2003, NH & FFS COL. (DZRJ); AMAZONAS, Presidente Figueiredo, Ig. Santa Cruz, hidrófitas submersas em correnteza, 08/x/03, FFS (CEUNES); AMAZONAS, Presidente Figueiredo, Ig. do Km 20, vegetação marginal em correnteza fraca, 07/x/03, F.F.Salles (CEUNES); ESPÍRITO SANTO, Santa Teresa, Nova Lombardia, Sítio Capitel de Santo Antônio, S 19°52’16.0”/ W 40°31’43.3”, 718 m.a.s.l., 19/i/ 2008, FFS col. (CEUNES); ESPÍRITO SANTO, Santa Teresa, Nova Lombardia, Sítio Capitel de Santo Antônio, Córrego Grande, S 19°52’31.0”/ W 40°31’49.1”, 768 m.a.s.l., 20/i/2008, vegetação marginal, FFS col. (CEUNES); ESPÍRITO SANTO, Caparaó, córrego na estrada, S 20°24’05,5’’/ W 41°453.45,9’’, 1015 m.a.s.l., 21/iv/2008, vegetação marginal, FFS col. (CEUNES).

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Americabaetis labiosus Lugo-Ortiz & McCafferty, 1996 (Figs. 1c, 14–17, 18, 21, 25, 29) Americabaetis labiosus Lugo-Ortiz & McCafferty, 1996: 164; Francischetti et al., 2003: 69; Domínguez et al., 2006: 70; Salles et al., 2010: 302.

Diagnoses. Nymphs: 1) Frontal keel absent; 2) lingua broadly pointed apically; 3) glossa 0.6x length of paraglossa, 4) apex of paraglossa with rows of pectinate setae; 5) segment II of labial palp with a small distomedial projection; 6) posterior margin of abdominal terga with rounded spines. Male imago: 1) turbinate eyes anteriorly divergent and widely separated from each other, upper surface ellipsoidal (Fig. 14); 2) terga light whitish brown, lateral margins darker (Figs. 14, 15); 3) forceps with first segment constricted medioapically (Fig. 17); 4) posterior margin of subgenital plate with a small rounded projection (Fig. 17); 5) length of body relatively small (4.0 mm). Description (Male imago). Measurements. Body 4.0 mm; forewing 4.0–4.3 mm; antenna 0.7 mm; tibia I: 1.31 mm; tibia II: 0.88 mm; tibia III: 0.89 mm. Head (Figs. 14–15). Coloration light brown with V shaped brown mark between compound eyes. Turbinate portion of compound eyes orangish; basal half of stalk brown, paler toward apex. Antenna light brown. Dorsal portion of turbinate eyes ellipsoidal; length 1.5x width; stalk height 0.5x width of dorsal portion; inner margins widely separated, divergent anteriorly. Thorax (Figs. 14–15). Pro, meso and metanotum brown; submedioscutum light brown; scutellum dark brown. Sternum brown. Anteronotal protuberance rounded. Metascutellar protuberance pointed dorsally. Legs whitish. Leg I: tibia 1.7x length of femur; tarsi 1.6x length of femur; and with 4 segments decreasing on length apically. Leg II and III: tibia 1.4x length of femur; tarsi 0.4x length of femur. Forewing (Figs. 16) hyaline, posterior region of costal and subcostal veins grayish; veins Costal and subcostal light brown; stigmatic area with 6 cross veins not touching subcostal vein; marginal intercalary paired, except single between veins ICu1 and A; length of intercalary vein between IMA and IMA2 1.7x distance between adjacent longitudinal veins; length of forewing about 2.4x width. Abdomen (Figs. 14–15). Terga light whitish brown, lateral margins darker; tracheation blackish. Sterna light whitish brown. Genitalia (Figs. 17) segment I whitish washed with brown, segments II and III whitish. Forceps segment I distinctly constricted medioapically; 0,5x length of segment II; distance between base of forceps 0,2x distance between lateral margins of forceps. Forceps segment II narrow submedially. Forceps segment III elongate, 2.7x as long as wide; 0.17x length of segment II. Posterior margin of subgenital plate with a small rounded projection. Comments. In Brazil A. labiosus is apparently restricted to the southern area of the country. Their nymphs, as those of A. titthion and A. mecistognathus, sp. nov., inhabit shallow areas with moderate to fast current (Fig. 29). However, unlike these species, they are often associated with dead leaves above rocks. The altitudinal range of this species varies from 700 to 1900 m.a.s.l. Distribution. PARAGUAY, URUGUAY, BRAZIL: Rio Grande do Sul, Paraná, Santa Catarina; Rio de Janeiro, Espírito Santo, São Paulo. NEW RECORDS: Minas Gerais (Fig. 1b). Material examined. MINAS GERAIS, Chácara, Cachoeira Menezes, 16/i/2000, CNF & R. F. Rocha; ESPÍRITO SANTO, Santa Teresa, Nova Lombardia, Sítio Capitel de Santo Antônio, Córrego Grande, S 19°52’31.0” / W 40°31’49.1”, 768 m.a.s.l., 19-20/i/2008, 20/ii/2009, FFS col. (CEUNES). One male imago (reared), Brazil, ESPÍRITO SANTO, Alfredo Chaves Country, Nova Estrela, waterfall Petralonga, 20°39'76.6"S/ 40°50'72.6"W, 23.v.2008, RB col. One male imago and one male subimago (reared), Brazil, ESPÍRITO SANTO, Alfredo Chaves Country, Nova Estrela, waterfall Petralonga, 20°39'76.6"S/ 40°50'72.6"W, 20.ii.2009, RB col.



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FIGURES 14–17. Americabaetis labiosus. Male imago. 14. Lateral view; 15. Dorsal view; 16. Forewing; 17. Genitalia.

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FIGURES 18–26. Americabaetis spp. Nymph. 18. Head of A. labiosus (frontal view); 19. Head of A. longetron (f.v.); 20. Labial palp of A. alphus; 21. Labial palp of A. labiosus; 22. Abdomen in dorsal view of A. longetron; 23. Abdomen in dorsal view of A. alphus (male); 24. Abdomen in dorsal view of A. alphus (female); 25. Posterior margin of terga IV of A. labiosus; 26. Posterior margin of terga IV of A. longetron.

Americabaetis longetron Lugo-Ortiz & McCafferty, 1996 (Figs. 1d, 19, 22, 26, 28) Americabaetis longetron Lugo-Ortiz & McCafferty, 1996: 165; Francischetti et al., 2003: 69; Domínguez et al., 2006: 70; Salles & Boldrini, 2008: 565; Salles et al., 2010: 302.

Diagnoses. Nymphs: 1) frontal keel present; 2) lingua rounded apically; 3) glossa 0.8x length of paraglossa; 4) apex of paraglossa with rows of simple setae; 5) segment II of labial palp with a strong distomedial projection; 6) posterior margin of abdominal terga with pointed spines; 7) abdomen elongate. Male imago: 1) turbinate eyes uniformly separated from each other, upper surface ellipsoidal ; 2) terga with a light yellowish brown band along midline ; 3) forceps with first segment distinctly constricted medioapically; 4) posterior margin of subgenital plate without a small rounded projection; 5) length of body relatively long (6.3 mm). Distribution. PARAGUAY, URUGUAY, BRAZIL : Rio Grande do Sul, Paraná, Santa Catarina; Rio de Janeiro, Espírito Santo, Minas Gerais, São Paulo (Fig. 1c). Comments. Nymphs of A. longetron are present almost exclusively in banks with marginal vegetation in areas with slow to moderate current; they resemble A. alphus in several aspects, as mouthpart morphology and



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somewhat similar habitat (Fig. 28). However, the distribution of A. longetron is far restricted when compared to that of A. alphus. The altitudinal range of this species varies from 371 to 1063 m.a.s.l. Material examined. ESPÍRITO SANTO, Santa Teresa, Nova Lombardia, Sítio Capitel de Santo Antônio, Pinguela, S 19°52’16.0” / W 40°31’43.3”, 718 m.a.s.l., 18/ii/2009, pedra em remanso, FFS col. (CEUNES); ESPÍRITO SANTO, Caparaó, Sítio Sonho Meu, S 20°28’08,8’’ / W 41°43’32,5’’, 1063 m.a.s.l., 21/iv/2008, vegetação marginal, FFS col. (CEUNES).

FIGURES 27–30. General aspect of Americabaetis nymphs’ habitat. 27. A. mecistognathus, sp. nov.; 28. A. alphus and A. longetron; 29. A. labiosus; 30. A. titthion.

Americabaetis titthion Lugo-Ortiz & McCafferty, 1996 (Figs. 1e, 30) Americabaetis titthion Lugo-Ortiz & McCafferty, 1996: 167; Francischetti et al., 2003: 69; Salles et al., 2004: 23; Domínguez et al., 2006: 72; Salles et al., 2010: 302.

Diagnoses. Nymphs: 1) frontal keel absent; 2) lingua broadly pointed apically; 3) glossa 0.8x length of paraglossa; 4) apex of paraglossa with rows of pectinate setae; 5) segment II of labial palp with a moderate distomedial projection; 6) posterior margin of abdominal terga with rounded spines; 7) meso and metasternum with a setose paired protuberance. Female imago: 1) forewing with costal area reddish-brown; 2) posterior margin of head dorsally projected; 3) meso and metasterna with small, setose paired protuberance. Male imago: unknown, see comments bellow.

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Distribution. BRAZIL: Rio Grande do Sul, Paraná, Santa Catarina; Rio de Janeiro, Espírito Santo, Minas Gerais (Fig. 1d). Comments. Americabaetis titthion is until now endemic to southeastern Brazil. Nymphs are present in shallow areas above rocks, in moderate to fast current (Fig. 30). The meso and metasternal projections, typical of this species [see Fig. 51 of Lugo-Ortiz & McCafferty (1996)], probably aids the nymph to withstand in this kind of habitat. At the Parque Nacional do Caparaó, where it is abundant, this is the only species of mayfly found above 2250 m.a.s.l. Although only females of this species have been described (Salles et al. 2003), the vestiges of the meso and metaesternal projections should also be encountered in male adults once these protuberances are found in nymphs of both sexes. This characteristic would be enough to distinguish male imagos of A. titthion from other members of Americabaetis. Lugo-Ortiz and McCafferty (1996), as well as Domínguez et al. (2006), described the setae at the apex of the paraglossa of this species as simple. However, we examined nymphs of A. titthion from different localities and concluded that these setae are pectinate, just as in the other species of the genus that live in areas with moderate to fast current above rocks (i.e., A. labiosus and A. mecistognathus, sp. nov.). At least in South America, species that live in a similar habitat, such as those of the genera Baetodes and Camelobaetidius Demoulin, exhibit the same kind of setae at the same place. According to Batista et al. (2006), these mayflies should be assigned to the grazer functional feeding group, once they use the tip of its mouthparts, as collectors, to remove periphyton. The presence of that kind of setae at the apex of the paraglossa should be regarded as a convergence among these genera, and a possible sinapomorphy among these three species of Americabaetis. Material examined. ESPÍRITO SANTO/MINAS GERAIS, Parque Nacional do Caparaó, Queda d’água acima da Casa Queimada, S 20°27’21,4’’/ W 41°48’32,1’’, 2250 m.a.s.l., 23/iv/2008, 26/iii/2009, FFS col. (CEUNES); ESPÍRITO SANTO, Parque Nacional do Caparaó, Rio São Domingos, Cachoeira da Farofa, S 20°28’19,3’’/ W 4149’41,3’’, 1956 m.a.s.l., 23/iv/2008, 26/iii/2009, FFS col. (CEUNES); MINAS GERAIS, Parque Nacional do Caparaó, Vale Encantado, S 20°24’38,7’’/ W 41°50’03,6’’, 1976 m.a.s.l., 24/iii/2009, FFS col. (CEUNES).

Key to South American Nymphs 1. Frontal keel absent (Figs. 2, 18) ............................................................................................................................. 2 1`. Frontal keel present (Fig. 19)................................................................................................................................... 5 2(1’). Distomedial projection of segment II of labial palp poorly developed (Figs. 8, 21); posterior margin of terga with blunt or rounded spines (Figs. 11, 25) .................................................................................................................... 3 2’. Distomedial projection of segment II of labial palp well developed, thumblike (as in Fig. 20); posterior margin of terga with pointed spines (as in Fig. 26) ...................................................... A. robacki Lugo-Ortiz and McCafferty 3(2’). Meso and metasterna with paired setose projections................................................................................. A. titthion 3’. Meso and metasterna without paired setose projections.......................................................................................... 4 4(3’). Mouthparts, including labrum, mandibles and maxillae distinctly elongate (Fig. 2); paraprocts with 8–9 spines (Fig. 13) ........................................................................................................................ A. mecistognathus, sp. nov. 4’. Only labium elongate; paraprocts with 16–18 spines ............................................................................ A. labiosus 5(1’). Gills large, as long as two and one-half or three abdominal segments combined (Fig. 43 of Lugo-Ortiz and McCafferty 1996) ................................................................................... A. maxifolium Lugo-Ortiz and McCafferty 5’. Gills not as above (Figs. 22–24) .............................................................................................................................. 6 6(5’). Body not elongate; paraprocts with 6–7 spines; gills poorly tracheated (Figs. 23–24); abdominal color pattern as in Figs. 23–24, without distinct medial band.............................................................................................. A. alphus 6’. Body distinctly elongate; paraprocts with 11–13 spines; gills well tracheated (Fig. 22); abdominal color pattern as in Fig. 22, with distinct medial band ..................................................................................................... A. longetron



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Acknowledgments The authors wish to express their gratitude to Angela Brunner da Rocha, for logistic support and for allowing us to work on her property; the staff from Reserva Biológica de Sooretama, Parque Nacional do Caparaó, and Parque Nacional das Araucárias; ICMBio (Instituto Chico Mendes de Conservação da Biodiversidade) and IBAMA (Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis) for collection permission (number 16719-1) and logistic support; Fundação de Apoio a Ciência e Tecnologia do Espírito Santo (FAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), for financial support (processes number 36327263/07, 45429502/09, 313117/2009-8, 470731/2009-5). We are also grateful to APREMAVI (Associação de Preservação do Meio Ambiente e da Vida) for logistic support; to Dr. C. Nieto for valuable suggestions; to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for providing a scholarship to EAR, to Universidade Comunitária da Região de Chapecó (Unochapecó) for logistical and financial support, and yet to Bruna Laís Turra and João Carlos Marocco for assistance during field works.

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