Caenis argentina Navas

Molineri, Carlos & Malzacher, Peter, 2007, South American Caenis Stephens (Ephemeroptera, Caenidae), new species and stage descriptions, Zootaxa 1660, pp. 1-31 : 7-9

Caenis argentina Navas ( Figs. 1–14 , 139–140 , 158 , 165 , 172 , 179 )

Caenis argentina Navas, 1915: 12 (male); Hubbard, 1982: 261; Malzacher, 2001: 2 (male, female, nymph, egg).

Type material ( IFML): Lectotype male imago and seven male imagos paralectotypes from ARGENTINA : Buenos Aires, Tandil, arroyo Quequén Chico, 7-I-1983, E. Domínguez col.

Additional material ( IFML): Two nymphs, 1 female subimago and 1 nymphal exuviae, same data as lectotype; 9 nymphs from ARGENTINA : Buenos Aires, Tandil, arroyo Chapaleofú, 9-I-1983, E. Domínguez; 6 nymphs from Buenos Aires, Pueyrredón, Laguna de los Padres, 10-II-2002, M. A. González-Sagrario col.; 3 nymphs and 1 female subimago from Santiago del Estero, Termas de Río Hondo, La Olla, Río Dulce, 15-VIII- 2004, C. Molineri col.; 2 male and 3 female adults, reared from nymphs, from Tucumán, Dpto. Burruyacu, Timbó Viejo, Río Salí, 27-IV-2004, C. Molineri & C. Nieto cols.; 12 nymphs from Tucumán, Ranchillos, canal DP2, 6-V-2006, C. Molineri col.; 1 nymph from Tucumán, Acheral, Laguna sobre arroyo Hollinado, cruce RP 38, 28-VII-2006, C. Molineri col.; 1 nymph from Catamarca, Bañado de Ovanta, S 28° 08' – W 65° 19', 24-VIII-2004, M. Peralta col.

Male imagos of C. argentina were thoroughly described by Malzacher (2001). Female imagos, as reported by Malzacher (2001) are similar to males, except that prosternal triangle is anteriorly truncated. Malzacher (2001) also described the nymphs of C. argentina . A list of characters useful to distinguish female imagos and nymphs follows.

Female imago. Occiput with a pair of paramedian grayish marks forming two concentric semicircles; pronotum with a pair of submedian black spots; all femora with preapical blackish bands; coloration of mesothoracic katepisternum (largest sclerite on the anteroventral corners of mesothorax) similar to rest of mesothorax; thoracic and abdominal sterna with well marked median grayish spots; abdominal sterna also with paramedian spots and with wide whitish zones medially and laterally; posterolateral filaments of abdominal segments long.

Mature nymph ( Fig. 158 ). General coloration yellowish-brown, pale blotches present on head (along median line and in sublateral zone of occiput), pronotum (posteromedian triangular zone), and mesonotum (irregular blotches near anterior margin, and three well marked pairs of lateral to sublateral circular blotches between wing bud bases). Head with paramedian gray marks on occiput ( Fig. 165 ), similar to those of female; hind margin of the head with long laterally directed setae and frayed microtrichia. Mandibles as in Figs. 139– 140 ; segment II of labial palp 1.36–1.63 times the length of segment III. Thorax. Pronotum with a pair of paramedian black dots. Meso and metasternum with a gray elongated median mark. Legs ( Figs. 12–14 ) whitish to yellowish, coxae II and III with broadly rounded projections ( Figs. 1–2 ); all femora with preapical blackish bands ( Figs. 12–14 ), dorsum of femora with few and weak setae, transversal row of setae on dorsum of fore femora reduced, only with 2–5 setae ( Figs. 10, 12 ); tibiae and tarsi of all legs with basal dark-yellow bands; tarsi with longitudinal row of long and slender spine-like setae at medial margin ( Fig. 11 ), tarsi II and III ( Figs. 13–14 ) with an additional submarginal row of serrated setae ( Fig. 9 ); tarsal claws strongly curved apically ( Figs. 3–5 ), tarsal claws I–II with 4–8 denticles, tarsal claw III with 10–20 denticles. Abdomen. Terga with broad pale zones laterally and medially ( Fig. 172 ), abdominal sterna with distinct median and paramedian gray spots ( Fig. 179 ). Operculate gills dorsally with small maculae slightly darker than the rest ( Figs. 158 , 172 ); dorsal microtrichia bifid and relatively slender ( Fig. 6 ), microtrichia on ventral submarginal row elongated ( Figs. 7–8 ). Posterolateral spines on abdominal segments very well developed. Caudal filaments whitish with dark joinings. Sternum IX apically rounded, setae on hind margin strong and apically bent inwards.

Diagnosis. Caenis argentina can be distinguished from all other species of Caenis by the following combination of characters. In the imago: 1) general coloration yellowish-brown; 2) prosternal triangle anteriorly pointed in males, with concave sides, truncated in females; 3) median filament on abdominal tergum II long; 4) fore legs 0.8–1 times length of body; 5) forceps apically rounded; 6) central sclerite of styliger elongated; 7) apophyses of styliger long and straight; 8) penes with rounded lobes and straight or slightly convex posterior margin; 9) coloration of mesothoracic katepisternum similar to rest of mesothorax. In the nymph: 1) head color pattern as in Fig. 165 , hind margin with long laterally directed setae and frayed microtrichia; 2) meso- and metacoxal processes present but relatively small ( Figs. 1–2 ); 3) tarsi with relatively slender setae, many of them serrated; 4) tarsal claws curved apically, tarsal claws I–II with 4–8 denticles, tarsal claw III with 10–20 denticles ( Figs. 3–5 ); 5) abdominal color pattern as in Fig. 172 ; 6) labrum with slightly rounded lateral margins (similar to Fig. 31 ); 7) segment II of labial palp 1.36–1.63 times the length of segment III; 8) lingua of hypopharynx with concave fore margin (similar to Fig. 156 ); 9) sternum IX apically rounded, setae on hind margin strong and apically bent inwards (similar to Fig. 7 b in Malzacher 2001).

Distribution ( Fig. 185). Argentina (Buenos Aires, Santiago del Estero, Catamarca, Tucumán).

Figures

FIGURES 1 – 14. Caenis argentina, nymph. 1, middle coxa, d. v.; 2, hind coxa, d. v; 3, foreclaw; 4, middle claw; 5, hind claw; 6, microtrichia on dorsum of gill II; 7 – 8, microtrichia on ventral submarginal row of gill II; 9, setae on longitudinal row of middle and hind tarsi; 10, setae on subapical dorsal row of fore femora; 11, setae on longitudinal row of foretarsi; 12, foreleg; 13, middle leg; 14, hind leg.

FIGURES 139 – 157. Left and right mandibles, d. v.: 139 – 140, C. argentina; 141 – 142, C. burmeisteri; 143 – 144, C. dominguezi; 145 – 146, C. gonseri; 147 – 148, C. tenella; 149 – 150, C. ludicra; 151 – 152, C. plaumanni; 153 – 154, C. uruzu. Hypopharynx, v. v.: 155, C. burmeisteri; 156, C. dominguezi; 157, C. tenella.

FIGURES 158 – 161. Nymph, general view: 158, C. argentina; 159, C. burmeisteri; 160, C. dominguezi; 161, C. ludicra.

FIGURES 165 – 166. Nymph, head color pattern: 165, C. argentina; 166, C. burmeisteri; 167, C. dominguezi; 168, C. tenella; 169, C. ludicra; 170, C. plaumanni; 171, C. uruzu.

FIGURES 172 – 178. Nymph, abdominal terga: 172, C. argentina; 173, C. burmeisteri; 174, C. dominguezi; 175, C. ludicra; 176, C. tenella; 177, C. plaumanni; 178, C. uruzu.

FIGURES 179 – 184. Nymph, abdominal sterna: 179, C. argentina; 180, C. burmeisteri; 181, C. dominguezi; 182, C. tenella; 183, C. plaumanni; 184, C. uruzu.

FIGURES 31 – 49. Caenis dominguezi, nymph. 31, labrum and detail of anteromedian emargination, d. v.; 32, setae on dorsum of hind femora; 33, seta on hind tibiae; 34, setae of fore femoral dorso-transversal row; 35, pronotum, d. v.; 36, fore leg; 37, middle leg; 38, hind leg; 39, middle coxa; 40, hind coxa; 41, foreclaw; 42, middle claw; 43, hind claw; 44, operculate gill and detail of dorsal surface; 45 – 46, microtrichia of submarginal ventral row of operculate gill; 47, abdominal gill III; 48, abdominal segment II and operculate gill, l. v.; 49, sternum IX of a male nymph. Abrevviations: OG = operculate gill; T 2 = second abdominal tergum.