Caenis uruzu, Molineri, Carlos & Malzacher, Peter, 2007

Molineri, Carlos & Malzacher, Peter, 2007, South American Caenis Stephens (Ephemeroptera, Caenidae), new species and stage descriptions, Zootaxa 1660, pp. 1-31 : 24-29

Caenis uruzu new species ( Figs. 96–122 , 153–154 , 164 , 171, 178, 184)

Type material: Holotype male imago (reared) with nymphal exuviae (genitalia and nymphal parts in slides) from ARGENTINA : Misiones, P.P. Urugua-í, arroyo Uruzú , 7-11-XII-1999, C. Molineri col. Paratypes: 13 male imagos from URUGUAY: Piraraja, Orilla Cebollati, 9-XII-1952, Carbonell col.; 11 nymphs same data as holotype; 1 nymph ARGENTINA : Misiones, 10 km NE de San Vicente, INTA Cuartel Victoria, 20-XI-1998, E. Domínguez, C. Molineri, C. Nieto cols.; 6 nymphs idem except date 30-XI-1986, E. Domínguez col; 2 nymphs Misiones, Bonpland, arroyo del Tigre, 26-XI-1986, E. Domínguez col.; 3 nymphs from Misiones, 25 km S El Soberbio, 21-XI-1998, E. Domínguez, C. Molineri, C. Nieto cols.; and 1 nymph from Misiones, Puerto Mado, arroyo Yacutinga, 19-20-XI-1998, E. Domínguez, C. Molineri, C. Nieto cols. Holotype and paratypes deposited at IFML, except 7 male imagos in MFCU, and 3 male imagos and 2 nymphs in FAMU.

Etymology. The name, noun in apposition, alludes to one of the rivers where the species was collected.

Male imago. Length: forewings, 2.7–3.1 mm; body, 2.5–3.4 mm. General coloration yellowish-brown. Head dorsally brownish shaded with gray, occiput behind eyes blackish; head ventrally paler; antennae yellowish. Thorax. Prothorax with yellowish-brown sclerites and whitish-yellow membranes; pronotum with gray markings; prosternum shaded with black on prosternal triangle and fore margin; prosternal triangle with concave sides, anteriorly blunt ( Fig. 100 ). Mesonotum chestnut, mesoscutellum dark brown; metanotum and pterothoracic pleurae and sterna yellowish-brown. Legs. Coxae and trochanters yellowish, femora whitish with yellow margins, tibiae yellowish, tarsi whitish. Foreleg of subequal length to body. Forewings hyaline slightly shaded with gray on C and Sc areas, longitudinal veins grayish-yellow, cross veins translucent. Abdomen yellowish-white extensively shaded with gray, tergum I slightly darker than the rest, pleural membranes whitish, tergum X yellowish with medial line blackish; finger-like projection on abdominal terga II long ( Fig. 101 ). Genitalia ( Fig. 96 ): styliger with yellowish sclerites, shaded with gray laterally; central sclerite large and elongated, apophyses of styliger sclerites wide at base and becoming thinner toward apex, hind margin of styliger plate convex ( Fig. 96 ); forceps yellowish, apically rounded ( Figs. 96–98 ); penes whitish with rounded lateral lobes ( Fig. 96 ). Caudal filaments whitish shaded with light gray.

Female imago. Unknown.

Mature nymph ( Fig. 164 ). Length of female: body, 4.1–5.5 mm; caudal filaments, 3.5–4.5 mm. Length of male: body, 3.5–3.8 mm, caudal filaments, 3.0 mm. Head yellowish shaded with blackish among ocelli and posterolateral corners (Fig. 171), occiput with a pair of submedian grayish star-like marks; hind margin with frayed microtrichia. Antennae yellowish-white. Mouthparts yellowish shaded with grayish on labrum and mandibles; labrum with rounded lateral margins and shallow anteromedian emargination ( Fig. 102–103 ); distal segment of labial palpi short, segment II of labial palp 1.67–1.90 times the length of segment III ( Fig. 105 ). Thorax. Pro- and mesonotum yellowish light brown with paler zones; with irregular gray markings; anterolateral corners of pronotum lightly to moderately projected ( Figs. 106–107 ). Thoracic sterna paler widely shaded with gray. Wingbuds grayish-black except on Cu area, whitish. Legs yellowish-white; coxae II–III with large, tapering, and distally rounded projections ( Figs. 108–109 ); femora with a grayish subapical mark, dorsum of femora with numerous setae ( Figs. 115, 120–122 ), transverse row at dorsum of femora I with 9 setae; basal and distal portions of tibiae and tarsi paler than the rest; all tarsi with a longitudinal row of robust simple setae, middle and hind tarsi with an additional row of serrated setae; tarsal claws yellowish translucent, very slightly curved, claws I–II with 3–5 small denticles ( Figs. 112–113 ), claw III with 23–25 denticles, increasing in size toward apex ( Fig. 114 ). Abdomen dorsally yellowish light brown with paler lateral margins and intersegmental membranes ( Fig. 178 ); terga I–II slightly darker than the rest, lateral zones of tergum II (at gill bases) whitish; median projection of tergum II well developed ( Fig. 104 ). Abdominal sterna ( Fig. 184 ) paler than terga, shaded with grayish almost completely except on a pair of submedian and sublateral whitish marks. Posterolateral spines whitish translucent. Operculate gills ( Fig. 110 ) yellowish-brown, remaining gills grayish; microtrichia on dorsum of gill II as in Fig. 116 ; microtrichia from the submarginal ventral row as in Fig. 111 . Sternum IX rounded apically, setae on hind margin strong and apically bent inwards. Caudal filaments whitish-yellow.

Diagnosis. Caenis uruzu new species can be distinguished from the other species of Caenis by the following combination of characters. In the imago: 1) general coloration yellowish brown; 2) prosternal triangle with concave sides, anteriorly blunt ( Fig. 100 ); 3) median filament on abdominal tergum II long ( Fig. 101 ); 4) fore legs as long as body; 5) forceps apically rounded ( Figs. 96-98 ); 6) central sclerite of styliger elongated ( Fig. 96 ); 7) apophyses of styliger sclerite broad and short ( Fig. 96 ). In the nymph: 1) head color pattern as in Fig. 171, hind margin with frayed microtrichia; 2) coxae II–III with well-developed and apically rounded projections ( Figs. 108–109 ); 3) fore tarsi with a longitudinal row of robust simple setae, middle and hind tarsi with a similar row and an additional row of serrated setae; 4) tarsal claws not strongly curved apically ( Figs. 112– 114 ), apical denticle of tarsal claw III much larger than the others; 5) abdominal color pattern as in Figs. 178 and 184 ; 6) labrum with slightly rounded lateral margins ( Fig. 103 ); 7) distal segment of labial palpi relatively short, segment II of labial palp 1.67–1.90 times the length of segment III ( Fig. 105 ); 8) lingua of hypopharynx with concave fore margin (similar to Fig. 156 ); 9) IX sternum rounded apically, setae on hind margin strong and apically bent inwards; 10) microtrichia from dorsum and operculate gills bifurcate and frayed ( Fig. 116 ).

Discussion. Caenis uruzu new species belongs to the argentina -group proposed by Malzacher (2001), because male imagos show a finger-like projection on abdominal tergum II, forelegs are subequal in length to body, and genitalic sclerites are well marked. Nymphs of C. uruzu were treated as C. ludicra by Malzacher (2001). However C. ludicra shows a marked western distribution, and it is not expected to be found in sympatry with C. uruzu .Distribution ( Fig. 185). Argentina (Misiones) , Brazil (Santa Catarina, Rio Grande do Sul), Uruguay.

Figures

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