Pseudochironomus ariquemis, Trivinho-Strixino & Shimabukuro, 2018

Trivinho-Strixino, Susana & Shimabukuro, Erika Mayumi, 2018, Brazilian Pseudochironomini (Diptera: Chironomidae) Part 2. New Pseudochironomus and Riethia species, Zootaxa 4403 (2), pp. 245-260 : 249-250

Pseudochironomus ariquemis sp. n.

( Figs 3–5 )

Type material. Holotype: Pupa with pharate male and larval exuviae, slide mounted in Euparal, Brazil, Bela Vista, RO, Ariquemis river, 08.viii.2001, leg. G.P.S. Dantas (I1-05, LEIA-UFSCar).

Derivatio nominis. The name ariquemis refers to the locality where the species was collected, Ariquemis River. The name is treated as a noun in apposition.

Diagnostic characters. Adult male of Pseudochironomus ariquemis sp. n. differs from all other species of the genus by the combination of the following characters. Adult male: thorax with acrosticals; anal point absent in hypopygium; superior volsella hook-shaped, with three simple setae; median volsella short with two setae; pars ventralis completely divided; inferior volsella with microtrichia and several marginal large setae; transverse sternapodeme without oral projections. Pupa: sternite I with two short anterior pair of fine spines; comb of segment VIII with one large tooth and 4–6 marginal teeth. Larva: AR = 1.42; mentum 169 µm long, with eleven brown teeth; median tooth longer than laterals.

Description. Male (n = 1). Head, wings and legs not discernible inside the pupal exuviae.

Thorax. Ac 7; Dc 14; Pa 3; Scts 17.

Hypopygium ( Fig. 3a, b ). Tergite IX without anal point. Laterosternite with four setae. Transverse sternapodeme 70 µm long, without oral projections. Phallapodeme 169 µm long. Pars ventralis narrow, 45 µm long. Gonocoxite 123 µm long. Superior volsella hooklike, with three preapical simple setae. Median volsella rounded with two simple setae. Inferior volsella pubescent with 10 ventro-marginal large setae. Gonostylus 146 µm long. HR 0.84.

Pupa ( Fig. 4 ). Cephalotorax. Frontal apotome strongly granulose. Cephalic tubercles short; frontal setae absent. Thorax strongly granulose; two antepronotals, longest setae 181 µm long; three precorneals and four dorsocentrals. Distance Dc1-Dc2 75 µm; Dc2-Dc3 390 µm; Dc3-Dc4 31 µm.

Abdomen. Length 3.7 mm. Sternite I with two anterior pair of fine spines ( Fig. 4a ). Tergite I bare. Tergite II-VI with variable patterns of shagreen usually forming an anterior band of stronger spines ( Fig. 4b ). Tergite IV with a median-anterior band 194 µm long of fine spines. Tergite VII and VIII with weaker shagreenation ( Fig. 4c ). Hooklets row extending nearly on 1/3 the width of tergite II. Pedes spurii B short on segment II. Pedes spurii A present in segment IV. Conjunctives III/IV to IV/V with continuous bands of spinules. Tergite VIII with posterolateral comb, with one large tooth and 4–6 marginal teeth ( Fig. 4d ). Segments I-IV with 0, 3, 3, 3 L setae, respectively; segments V-VI with three taeniae; segments VII- VIII with four taeniae. Anal lobe 310 µm long, with anterior weak shagreenation and complete fringe of taeniae. Genital sac 440 µm long.

4th instar larva exuviae ( Fig. 5 ). Antenna ( Fig. 5a ) 126 µm, basal segment 74 µm long, AR 1.42. Large Lauterborn organs on apex of 2nd segment. Blade 64 µm, surpassing 5th segment. Dorsal sclerites of head as in figure 5b. Pecten epipharyngis composed by 3 plates. Labral lamella and SI as in figure 5c. Premandible ( Fig. 5d ) 120 µm long with two large teeth; brush present. Mandible ( Fig. 5e ) 208 µm long, with one strong clear apical tooth and four brown inner teeth. Seta subdentalis slender, 58 µm long, not surpasses apical tooth. Mentum ( Fig. 5f ) 169 µm wide with eleven brown teeth; median tooth longer than first laterals; 2nd laterals recessive and fused to first laterals. Ventramental plates 125 µm long, with very distinct striations and touching at the midline.

Figures

FIGURE 3. Pseudochironomus ariquemis sp. n. male. (a) Hypopygium. (b) Hypopygium, right ventral view,left dorsal view.

FIGURE 4. Pseudochironomus ariquemis sp. n. pupa. (a) Sternite I. (b, c) Abdominal tergite. (d) Posterolateral spurs of segment VIII.

FIGURE 5. Pseudochironomus ariquemis sp. n. larva.(a) Antenna. (b) Dorsal sclerites of head.(c) Labral lamella and SI. (d) Premandible.(e) Mandible.(f) Mentum and ventromental plate.