Americabaetis titthion Lugo-Ortiz & McCafferty, 1996

Salles, F. F., Raimundi, E. A., Boldrini, R. & Souza-Franco, G. M., 2010, The genus Americabaetis Kluge (Ephemeroptera: Baetidae) in Brazil: new species, stage description, and key to nymphs, Zootaxa 2560 (1), pp. 16-28 : 26-27

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.

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) .

Figures

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).

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.