Corinnella thomasi, Boldrini, R., Salles, F. F. & Pes, A. M. O., 2013

Boldrini, R., Salles, F. F. & Pes, A. M. O., 2013, A new species of Corinnella Thomas & Dominique, 2006 (Ephemeroptera: Baetidae), Zootaxa 3608 (1), pp. 75-80 : 76-80

Corinnella thomasi sp. nov. Boldrini & Salles

( Figs. 1–13 )

Diagnoses. 1) Labrum with shallow distomedial emargination and small process ( Fig. 4 a); 2) basal half of mandible with fine, simple setae ( Figs. 7, 8 ); 3) posterior margin of terga with rounded spines ( Fig. 11 ); 4) tarsal claw with seven to nine denticles ( Figs. 10 a, 10c, 10d); 5) inner and outer denticles of tarsal claw distinctly longer than the others ( Figs. 10 a, 10c, 10d).

Description

Nymph. Length: 4.3 mm; length of antennae: broken; length of cerci: 1.8 mm; length of terminal filament: 1.6 mm; tibia I: 0.8 mm; tibia II: 0.9 mm; tibia III: 0.8 mm. Head ( Figs 1, 2 ). Light brown. Antennae light brown, with scape and pedicel subcylindrical. Labrum ( Fig. 4 a). Subrectangular, broader than long. Length about 0.6× maximum width. Distal margin with shallow medial emargination and small process. Ventrally with short, fine, simple setae scattered over area; anterolateral and distal margin with bifid setae ( Figs. 4 a, 4b). Dorsally with few long, fine, simple setae over basal area; lateral and anterolateral margin with 11 long, fine, simple setae. Hypopharynx ( Fig. 5 ). Lingua little shorter than superlingua, apex rounded and slightly convex, with tuft of short, fine, simple setae. Superlingua with outer margin concave, with fine, simple setae on distal margin. Maxilla ( Fig. 6 ). Crown of galea-lacinia with three denticles; inner dorsal and inner ventral row of setae with three setae at the same orientation of denticles, one simple seta and two pectinate denti-setae. Medial protuberance of galea with 1 + 2 long, fine, simple setae. Maxillary palp II bifid, 1.3× length of galea-lacinia. Left mandible ( Fig. 7 ). Incisors fused, curved inward, with nine denticles. Prostheca robust, apically denticulate. Margin between prostheca and mola straight without row of setae; tuft of setae at apex of mola absent. Basal half with fine, simple setae over dorsal area. Mola reduced. Right mandible ( Fig. 8 ). Incisors fused, curved inward, with 11 denticles. Prostheca slender, apically denticulate; margin between prostheca and mola without setae; crown of setae present at base of mola present; tuft of setae at apex of mola absent. Basal half with fine, simple setae over dorsal area. Mola reduced. Labium ( Fig. 9 ). Glossa narrow and subequal in length to paraglossa; inner margin with eight fine, simple setae; apex with three long, fine pectinate setae; outer margin with six long, fine setae; ventral surface with a row of eight short, fine, simple setae. Paraglossa sub-rectangular, curved inward; apex with three rows of long, fine, pectinate setae; ventral surface bare; dorsal surface with two fine, simple setae near apex. Labial palp with ventral surface with many, long, fine simple setae. Segment II with distomedial protuberance robust and rounded; dorsally without a row of setae. Segment III conical, length 0.8× width, scattered with fine, simple setae.

Thorax ( Figs. 1, 2 ). Brown with marks light brown. Legs light brown. Hind wing pad present. Tibia I, II and III subequal in length of the respective femur; tarsi I, II and III 0.4× length of respective femur. Foreleg ( Fig. 10 a). Femur. Length about 3.5× maximum width; dorsally with row of ca. 40 long, spine-like setae; ventrally with seven short, spine-like setae. Tibia. Dorsally with few, short, fine, simple setae; ventrally with short, spine-like setae; anterior surface with row of short, spine-like setae near to patella-tibial suture ( Fig. 10 b); posterior surface with a row of short, spine-like setae near inner margin and 15 robust, spine-like setae at apex, increasing in length toward apex; patellatibial suture present, 0.3× in length of tibia. Tarsi. Dorsally with short, fine, simple setae; ventrally with 14 short, spine-like setae, and one long fine spine-like setae near apex; posterior surface with short, fine simple setae. Tarsal claws ( Fig. 10 c, 10d) with seven to nine denticles, inner and outer denticles distinctly longer than the others.

Abdomen ( Figs. 2, 3 ). Light brown; segments II – VI and segments IX – X washed with brown. Terga IV ( Fig. 11 ). Surface with fine, simple setae over area; posterior margin with rounded spines. Gills IV ( Fig. 12 a). Light brown; margins with narrow spine intercalating short, fine, simple setae ( Fig. 12 b); tracheae not pigmented. Paraproct ( Fig. 13 ). With three spines near inner margin; surface bare, without shagreened area; postero-lateral extension smooth. Cerci light brown; outer and inner margin of the terminal filament and inner margin of the cerci with tufts of long, simple setae; outer margin of the cerci with short, fine spine-like setae in each segment.

Etymology: The name of the species is in honor of Dr. Alain Thomas, for his significant contributions to the knowledge of Ephemeroptera .

Distribution. BRAZIL: Rondônia.

Material examined. Holotype: Female nymph (antennae broken), BRAZIL, Rondônia, Ribeirão, Rio Madeira, 10°13'54.5"S / 65°17'08"W, 6.vi.2004, Hamada, N. leg (INPA). Paratype: One male imature nymph mounted on slides, BRAZIL, Rondônia, Iata, Rio Madeira, 10°35'46.58''S / 65°23'00.96''W, 22.viii.2012, Boldrini, R., Fernandes, A.S. leg (PPGBT).

Comments. Corinnella thomasi sp. nov. is easily distinguished from C. eximia by the shape of the labrum, with the distomedial emargination clearly discernible in C. eximia versus shallow in C. thomasi sp. nov.; by the shape of tarsal claws, with only the first denticle distinctly longer in C. eximia versus the first and last denticles distinctly longer in C. thomasi sp. nov.; by the shape of spines on the posterior margins of terga, being pointed in C. eximia and rounded in C. thomasi sp. nov. The rounded spines found on the posterior margins of terga can be visualized using a microscope with phase contrast.When Dominique et al. (2005) described the genus Corinnella (as Corinna ), they stated that the tarsal claws were unique among Baetidae . Later, Nieto (2010), while performing a phylogenetic analysis of South American Baetidae , considered that the tarsal claws of Corinnella were spatulate, such as in the genus Camelobaetidius . Based on the new species, we agree with Nieto (2010) regarding the type of tarsal claws. Despite this similarity, Corinnella presents a series of characteristics that distinguishes it from the genus Camelobaetidius , such as: absence of the dorsal arc of setae on the labrum; presence of many long, fine, simple setae on outer margin of labial palp; and presence of a row of few spine-like setae along patella-tibial suture.

Figures

FIGURES 1 – 3. Corinnella thomasi sp. nov., nymph. 1 (lateral view). 2. (dorsal view). 3. detail of abdomen and cerci.

FIGURES 4 – 9. Corinnella thomasi sp. nov., nymph. 4 a, labrum (left ventral view, right dorsal view). 4 b; detail of setae of the apical margin of labrum. 5, hypopharynx; 6, maxilla. 7, left mandible. 8, right mandible. 9, labium (left dorsal view, right ventral view).

FIGURES 10 – 13. Corinnella thomasi sp. nov., nymph. 10 a, foreleg. 10 b, detail of patella-tibial suture. 10 c, photo in detail of the tarsal claw. 10 d, detail of the tarsal claw. 11, posterior margin of terga IV. 12 a, gill IV. 12 b, detail of margin of the gill IV. 13, paraproct.