Caenis

Molineri, Carlos & Malzacher, Peter, 2007, South American Caenis Stephens (Ephemeroptera, Caenidae), new species and stage descriptions, Zootaxa 1660, pp. 1-31 : 3

Key to Caenis species from Argentina

Mature nymphs

1. Dark pigments on head present on mediolongitudinal line of occiput ( Fig. 166 ); coxal processes narrow, with smooth margins ( Figs. 21–22 ); tarsal claws I–II with 5–7 very large denticles ( Figs. 28–29 ); operculate gills heavily maculated ( Figs. 27 , 159 , 173 ) [PA, ARG (Corrientes, Formosa)] ............. C. burmeisteri

1´. Dark pigments on head variable but never present on medial line of occiput ( Figs. 165 , 167–171); coxal processes more or less elongated, with serrated margins (e.g., Figs. 1–2 , 39–40 , 127–128 ); tarsal claws I– II with small denticles or without (e.g., Figs. 3–4 ); operculate gills not maculated ( Figs. 44 , 134 , 110 ) or slightly maculated ( Figs. 158 , 172 ) ............................................................................................................. 2

2. Small species (body length of male <3.0 mm, female <3.8 mm); general coloration very pale, whitish or yellowish almost without grayish shading ( Fig. 162 ); foretibia with a medial row of long setae, as long or longer than width of tibia ( Fig. 130 ); posteromedian projection of abdominal tergum II short and very broad ( Figs. 126 , 162 ); IX sternum with a deep V-shaped notch at hind margin and with very short lateral spines ( Fig. 135 a–b) [URU, ARG ( Formosa, Misiones, Buenos Aires)] ................................... C. tenella

2´. Medium to large species (male length> 3.5 mm, female> 4.1 mm); general coloration darker, yellowish brown to dark brown with grayish markings ( Figs. 158, 160–161 , 163–164 ); foretibia only with short setae ( Fig. 83 ); posteromedian projection of abdominal tergum II longer and narrower (e.g., Fig. 48 ); hind margin of IX sternum rounded, truncate or with an U-shaped indentation, lateral spines longer and stronger (e.g., Fig. 49 ) ......................................................................................................................................... 3

3. Occiput without submedian marks (Fig. 167); operculate gills only with simple setae dorsally ( Fig. 44 ). 4

3´. Occiput at least with a pair of submedian star-like dark markings ( Figs. 165 , 168–171); operculate gills with simple setae and plumose or scale-shaped microtrichia1 dorsally (e.g., Figs. 6 , 74 )........................... 5

4. Abdominal sternum IX with a median U-shaped indentation on posterior margin ( Fig. 49 ) [BO, ARG (Córdoba, Catamarca, Santiago, Salta)] ................................................................................ C. dominguezi

4´Abdominal sternum IX with straight or slightly rounded posterior margin [CHI, ARG (Neuquén, Río Negro)] ........................................................................................................................................... C. gonseri

5. Dorsal surface of body and operculate gills with large, scale-shaped microtrichia ( Figs. 8 i-j in Malzacher 2001); lateral margin of segment IX, besides short and apically frayed spines, with small teeth ( Fig. 8 l in Malzacher 2001) [BRA, ARG (Misiones)] .............................................................................. C. plaumanni

5’. Dorsal surface of body and operculate gills without or with small ramified or bifurcate microtrichia ( Figs. 6 , 74 , 116 ); lateral margin of segment IX without small teeth .................................................................... 6

1. Microtrichia can only be seen under high magnification (e.g., x100–x400) 6. Hind margin of the head with relatively long, laterally directed setae; abdominal sterna with blackish sublateral spots and other distinct marks ( Fig. 179 ); coxal processes short, semicircular or semielliptical ( Figs. 1–2 ) [ARG (Buenos Aires, Santiago, Catamarca, Tucumán)] ........................................ C. argentina

Figures

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 15 – 30. Caenis burmeisteri. Male imago: 15, genitalia, v. v.; 16 – 18, detail of forceps, v. v. Nymph: 19, detail of anteromedian emargination of labrum; 20, labrum, d. v.; 21, hind coxa; 22, middle coxa; 23, foreleg; 24, middle leg; 25, hind leg; 26, microtrichia on submarginal ventral row of gill II; 27, gill II, d. v.; 28, foreclaw; 29, middle claw; 30, hind claw.

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

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 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 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.

FIGURES 123 – 138. Caenis tenella, nymph. 123, labrum, d. v.; 124, labium, v. v. (palpus and setae at the right, omitted); 125, pronotum, left half; 126, detail of posteromedian projection of abdominal tergum II; 127, middle coxa; 128, hind coxa; 129, setae on dorsal transverse row of fore femora; 130, foreleg; 131, middle leg; 132, hind leg; 133, microtrichia of submarginal ventral row of operculate gill; 134, operculate gill; 135, IX sternum, v. v. (a, female; b, male); 136, foreclaw; 137, middle claw; 138, hind claw.

FIGURES 96 – 122. Caenis uruzu. Male imago: 96, genitalia, v. v.; 97 – 98, details of forceps, v. v.; 99, lateral filaments of abdomen; 100, preesternal triangle; 101, detail of finger-like projection of abdominal tergum II, l. v. Nymph: 102, detail of anteromedian emargination of labrum; 103, labrum, d. v.; 104, detail of posteromedian projection of tergum II; 105, labium, v. v. (setae omitted on right side); 106 – 107, pronotal lateral margin; 108, middle coxa; 109, hind coxa; 110, operculate gill; 111, microtrichia on submarginal ventral row of operculate gill; 112, foreclaw; 113, middle claw; 114, hind claw; 115, setae on dorsum of middle and hind femora; 116, microtrichia on dorsum of operculate gill; 117, seta on posterior margin of hind tibia; 118, seta on hind tarsi; 119, setae on transverse dorsal row on fore femora; 120, fore leg; 121, middle leg; 122, hind leg.

FIGURES 162 – 164. Nymph, general view: 162, C. tenella; 163, C. plaumanni; 164, C. uruzu.

FIGURES 66 – 85. Caenis ludicra, nymph. 66, middle coxa; 67, hind coxa; 68, hind claw; 69, middle claw; 70, foreclaw; 71, hind claw; 72, middle claw; 73, foreclaw; 74, microtrichia on dorsum of operculate gill; 75 – 76, microtrichia on submarginal ventral row of operculate gill; 77, seta on posterior margin of hind tibia; 78, seta on posterior margin of hind tarsi; 79, setae on dorsal transverse row of fore femora; 80, microtrichia on dorsum of hind femora; 81, seta on hind tarsi; 82, seta of posterior margin of hind femora; 83, foreleg; 84, middle leg; 85, hind leg.

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