Caenis tenella Navas, comb. nov.
Creators: name: Molineri, Carlos
name: Malzacher, Peter
Publisher: name: Zenodo
Year: 2007
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Ephemeroptera
Caenidae
Caenis
Caenis tenella

description: Caenis tenella (Navas) comb. nov. (Figs. 123–138, 147–148, 162, 168, 176, 182)
Eurycaenis tenella Navas, 1932a: 112 (male, female)
Brachycercus tenella; Thew, 1960: 202; Domínguez et al., 2006: 197 Brachycercus tenellus; Soldán, 1986: 294
Caenis grimi Malzacher, 2001: 15 (male, female, eggs) syn. nov.
Type material. Eurycaenis tenella: holotype male imago and allotype female imago (MUNSA) from ARGENTINA: Buenos Aires, San Miguel, 9-XII-1932 and 3-XI-1931, Williner S. J. col. Caenis grimi: holotype male imago (IFML) from ARGENTINA: Formosa, Laguna Yema, S 24° 22' – W 61° 09', 11-XI-1985, E. Domínguez col.; 50 paratypes imagos of both sexes, data as holotype.
Additional material. One reared male subimago and nymphal exuviae from ARGENTINA: Misiones, P.P. Urugua-í, arroyo Uruzú, S 25º 51' – W 54º 10', 322 m, 7-11-XII-1999, C. Molineri col.; 3 male imagos and 1 nymph Misiones, San Pedro, confluencia ríos Alegría y Pirai-Guazu, 22-23-XI-1998, E. Domínguez et al. cols.; 11 female imagos Misiones, 25 km S El Soberbio, 21-XI-1998, E. Domínguez et al. cols.; 1 nymph, 1 male and 2 female imagos Misiones, Candelaria, 2 km E Bonpland, río del Camping, 15-II-1985, E. Domínguez col.; 1 male and 7 female imagos Misiones, Mado, 16-II-1985, E. Domínguez col.; 5 male and 5 female imagos Misiones, 10 km NE de San Vicente, INTA Cuartel Victoria, 30-XI-1986, E. Domínguez col.; 1 nymph Misiones, Puerto Mado, arroyo Yacutinga, 19-20-XI-1998, E. Domínguez et al. cols.; 11 male and 3 female imagos Misiones, P.N. Iguazú, 26-XI-1998, río Iguazú, Puerto Canoas, Domínguez, Molineri & Nieto cols.; 9 male and 15 female imagos Misiones, 10 km NE de San Vicente, INTA Cuartel Victoria, 20-XI-1998, E. Domínguez et al. cols.; 6 male and 20 female imagos URUGUAY: Salto Arapey, 4 km de Las Termas, Carbonell col.; 2 male and 2 female imagos Cerro Largo, arroyo Quebracho (curso superior), 4-8-III-1959, Carbonell col.; 30 male and 30 female imagos Tacuarembó, arroyo Laureles, 10-XI-1954, Carbonell col.; 50 female adults Salto, Paso Yacaré, arroyo Itapebi, Zolessi et al. cols. BRAZIL: 3 nymphs, Nova Teutonia, 100 km E. Cacado, S 27° 11' – W 52° 23', III-1962; 1 nymph, Seara, S 27° 09' – W 52° 15', 18-IV-1962; 2 nymphs, Tupitinga, Santa Cruz Riv., S 27° 30' – W 51° 12', XII-1962; Rio Grande do Sul, Arroio do Hilario, S 30° 43' – W 53° 30', XI-1964. All the material in IFML, except 20 male and 50 female imagos in MCFU and nymphs from Brazil in col. Malzacher.
Imagos. Navas (1932a) descriptions are uninformative, but Malzacher (2001) give a complete treatment of male and female imagos (as C. grimi).
Mature nymph (Fig. 162). Length of female: body, 3.8 mm; caudal filaments, 2.5–2.8 mm; length of male: body, 2.7 mm; caudal filaments, 2.0 mm. General coloration yellowish to brownish. Head shaded gray on occiput and between antennae (Fig. 168), stronger on a transverse band behind lateral ocelli; venter of head paler than dorsum; antennae whitish, with strong setae on scape and pedicel; hind margin of the head with short bifid setules. Mouthparts: clypeus (Fig. 123) with strong setae directed posteriorly, labrum as in Fig. 123, sometimes with small bifid setae; labium (Fig. 124) with short and conic distal segment on palpi (segment II of labial palp 1.80–2.43 times the length of segment III), and large subquadrate glossae. Thorax. Pro- and mesonotum brownish-yellow with pale blotches, with very few grayish markings. Anterolateral margin of pronotum rounded and with setae (Fig. 125). Wingbuds shaded with gray on posterior half. Metanotum whitish. Legs (Figs. 130–132): forelegs yellowish, middle and hind legs whitish; shaded with gray on coxae; coxal projections rounded with serrated margin (Figs. 127–128); fore femora with subdistal transverse row of dorsal
setae (Figs. 129–130), middle and hind femora with few dorsal setae, mainly along posterior margin (Figs. 131–132); fore tarsus with one row of robust simple setae; middle tarsus with one row of serrated setae; hind tarsus with one row of simple setae and one row of serrated setae; tarsal claws with small denticles, more numerous on hind claws (Figs. 136–138), apex moderately to strongly curved. Abdomen whitish with yellowish zones on median projection of tergum II, lateral zones of terga VII–IX, and on tergum X (Fig. 176); median projection of abdominal tergum II small (Fig. 126). Abdominal sterna whitish without marks (Fig. 182). Posterolateral pointed projections on abdominal segments III–IX. Abdominal gill II (Fig. 134) yellowish translucent very slightly shaded with gray, dorsum only with simple setae, stout setae (Fig. 133) present on the ventral submarginal row; gills III–VI shaded completely with grayish, with a blackish spot at the base (visible through operculate gills, Fig. 176). Sternum IX apically with a deep V-shaped notch (Fig. 135) and with bifid setules on hind margin. Cerci whitish.
Diagnosis. Caenis tenella can be distinguished from the other species of Caenis by the following combination of characters. In the imago: 1) general coloration whitish-yellow; 2) prosternal triangle anteriorly elongated, pointed to slightly rounded in males, somewhat wider and rounded apically in females; 3) median filament on abdominal tergum II absent; 4) fore legs 0.5–0.6 times length of body; 5) forceps apically rounded; 6) central sclerite of styliger dome-shaped; 7) apophyses of styliger sclerite bent inwards; 8) penes with projected and pointed lateral lobes; 9) color of katepisternum similar to the rest of thoracic sclerites. In the nymph: 1) head color pattern as in Fig. 168, hind margin with short bifid setules; 2) meso- and metacoxal processes present but small (Figs. 127–128); 3) middle tarsus generally with one row of serrated setae; 4) tarsal claws with small denticles, apex curved (Figs. 136–138); 5) labrum with slightly rounded lateral margins, clypeus with strong setae (Fig. 123); 6) labial glossae large and subquadrate (Fig. 124), segment II of labial palp 1.80–2.43 times the length of segment III (Fig. 124); 7) lingua of hypopharynx relatively large and with concave fore margin (Fig. 157); 8) IX sternum apically with a deep V-shaped notch and with bifid setules on hind margin.
Discussion. Navas (1932) described this species from a pair of imagos of both sexes. As the types have been lost, serious doubts about the identity of the species existed (Thew 1960, Soldán 1986, Domínguez et al. 2006), but the pinned holotype and allotype of Eurycaenis tenella Navas (1932) were recently discovered in Salta (Argentina). The examination of these types and those of Caenis grimi Malzacher (2001), showed that both species are the same, and are here proposed as subjective synonyms. Thus the new combination Caenis tenella (Navás) is created to accommodate this species.
Distribution (Fig. 186). Argentina (Formosa, Misiones, Buenos Aires), Uruguay, Brazil (Rio Grande do Sul).
description: Published as part of Molineri, Carlos & Malzacher, Peter, 2007, South American Caenis Stephens (Ephemeroptera, Caenidae), new species and stage descriptions, pp. 1-31 in Zootaxa 1660 on pages 21-24, DOI: 10.5281/zenodo.179923