Caenis gonseri Malzacher

Molineri, Carlos & Malzacher, Peter, 2007, South American Caenis Stephens (Ephemeroptera, Caenidae), new species and stage descriptions, Zootaxa 1660, pp. 1-31 : 14-16

Caenis gonseri Malzacher ( Figs. 50–65 , 145–146 )

Caenis gonseri Malzacher, 2001: 11 (male).

Type material. Paratypes 10 male imagos from CHILE, río Choapa, 13-VI-1986, T. Gonser col. ( IFML).

Additional material ( IFML). Four male and 1 female imagos, 2 female subimagos, and 2 nymphal exuviae from ARGENTINA : Neuquén, Bajada del Agrio, RN 40, 70 km N de Zapala, Río Agrio, 12-XII-1997, C. Molineri col.

Male imago. Length: body, 3.6–3.8 mm; foreleg, 3.2–3.5 mm; fore wing, 3.7–4.0 mm. As Malzacher (2001: 11) had thoroughly described the male imago, a redescription will not be included here. Only one difference was found when checking the four males from Neuquén with Malzacher´s description: the finger-like process on abdominal tergum II is not visible, probably because it is pressed against the abdomen. This feature is assumed to be present in males, since it is well visible in the females collected with them.

Female (imago and subimago). Length: body, 5.7–6.0 mm; fore wing, 4.2–4.6 mm. Antennae yellowish; occiput with a transverse blackish line connecting lateral ocelli. Thorax. Pronotum with relatively acute anterolateral projections, gray shading forming a quadrangular empty mark medially; prosternal triangle ( Fig. 50 ) anteriorly blunt, as in males. Katepisternum as dark as the remaining thoracic sclerites. Abdomen shaded with gray on broad transverse bands, mediolongitudinal line paler, bordered by a pair of submedian darker lines; abdomen ventrally paler, very lightly shaded gray, somewhat stronger laterally. Posterolateral filaments of abdomen present on segments IV–IX ( Figs. 53–54 ), longer than in male, those of segments IV–VII are longer than the rest. Finger-like process of abdominal tergum II present, short ( Fig. 55 ). Ninth sternum broadly rounded posteriorly ( Fig. 52 ). Egg mass yellowish.

Nymphal exuviae. Length of male: body, 5.0 mm; caudal filaments, 3.5 mm. Length of female: body, 6.0 mm; caudal filaments, 4.0 mm. Head: with a pair of pale blotches on sublateral zones of occiput; hind margin of head with small simple setules. Mouthparts: labrum with broad and smooth anteromedian emargination, mandibles as in Figs. 145–146 ; segment II of labial palp 1.44 times the length of segment III. Thorax. Pronotum anteriorly projected as in Fig. 56 . Pale blotches present on mesonotum: 1 small circular blotch in the median zone of anteronotal projection, and 4 paired blotches on anterior half of mesonotum (the larger pair near the base of wingpads, the other three much smaller and located between the others). Legs as in Figs. 63– 65 . Coxal processes very short and rounded. All tarsi with one row of simple setae, hind tarsi with an additional row of serrated setae. Tarsal claws ( Figs. 57–59 ) relatively straight, fore and middle claws with 4–5 weakly marked denticles, hind claws with about 20 denticles. Abdomen. Dorsal projection of tergum II short ( Fig. 55 ). Operculate gills with simple setae dorsally, microtrichia on ventral submarginal row elongated to subtriangular. Ninth sternum apically rounded, hind margin with simple setae, few setae apically bent inwards.

Diagnosis. Caenis gonseri can be distinguished from the other species of the genus by the following combination of characters. In the imago: 1) general coloration yellowish-brown; 2) prosternal triangle anteriorly blunt ( Fig. 50 ); 3) median filament on abdominal tergum II short ( Fig. 51 ); 4) fore legs 0.9 times length of body; 5) forceps apically rounded, with small projections apically; 6) central sclerite of styliger circular; 7) apophyses of styliger sclerite, long and broad; 8) lobes of penes generally with straight hind margin, lateral lobes rounded and slightly projected; 9) color of katepisternum similar to the rest of thoracic sclerites; 10) posterolateral filaments present on abdominal segments IV–IX, longer on IV–VII ( Figs. 53–54 ).

In the nymph: 1) as only the nymphal exuvia is known, the epidermic coloration of the head was not available, a pair of pale blotches is present on sublateral zones of occiput, hind margin of head with small simple setules; 2) meso- and metacoxal processes present but narrow; 3) serrated setae only in hind tarsi ( Fig. 62 ); 4) tarsal claws relatively slender (denticles apparently worn out) ( Figs. 57–59 ); 5) abdominal color pattern unknown, posteromedian projection of abdominal tergum II relatively short ( Fig. 55 ); 6) labrum with shallow and smooth anteromedian emargination; 7) segment II of labial palp 1.44 times the length of segment III; 8) lingua of hypopharynx with concave fore margin (similar to Fig. 156 ); 9) IX sternum apically rounded, hind margin with simple setae, few setae apically bent inwards; 10) dorsum of gill II only with simple setae; 11) dorsum of all femora with numerous long spines ( Figs. 63–65 ).

Distribution ( Fig. 188). Argentina (Neuquén, Río Negro), Chile.

Figures

FIGURES 50 – 65. Caenis gonseri. Female imago: 50, prosternal triangle; 51, abdominal segment II, l. v.; 52, IX sternum; 53, lateral filaments of abdomen (female subimago); 54, idem (female imago). Nymph: 55, abdominal tergum II; 56, left half of nymphal pronotum, d. v.; 57, foreclaw; 58, middle claw; 59, hind claw; 60, setae on dorsal transverse row of fore femora; 61, seta on middle tarsi; 62, seta on hind tarsi; 63, foreleg; 64, middle leg; 65, 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.