Disersus otongachi, Čiampor & Kodada & Bozáňová & Čiamporová-Zaťovičová, 2021

Čiampor, Fedor, Kodada, Ján, Bozáňová, Jana & Čiamporová-Zaťovičová, Zuzana, 2021, Disersus otongachi a new species of Larainae riffle beetles from Ecuador (Coleoptera: Elmidae), Zootaxa 4963 (1), pp. 193-199 : 194-197

Disersus otongachi sp.nov.

Type locality: Rio Toachi, which is small river ca 20 m wide, has fast flowing white water, is slightly eutrophied, and has riffles and large boulders ( Fig. 9 ).

Type material: Holotype ♂ ( PUCE): „ Ecuador, Santo Domingo de los Tsachilas prov., Otongachi env., Río Toachi , 00˚19’14.8” S, 78˚57’08.4” W, 861m a.s.l., 10.8.2013, light, Čiampor & Čiamporová-Zaťovičová lgt.“ , Paratypes 11♂, 15 ♀ ( PUCE, CCB) with the same locality data as holotype .

Description. Body elongate ( Figs 1, 3 ), CL: males ca 9.5 (8.89–10.46) mm, females ca 10.2 (9–10.91) mm, ca 3.2 times as long as wide (CL/EW), dorsum convex, surface hairy. Body dark brown to black; scape, pedicel yellowish, trochanters paler; mesotibiae pale brown and ventral side lighter due to pale pubescence.

Head partly retractable into thorax, densely setose, HW: males 1.56 (1.44–1.65 mm), female 1.66 (1.63–1.77) mm, ID: males 0.93 (0.84–1) mm, females 0.97 (0.93–1.05) mm. Labrum wider and longer than clypeus, densely covered with long yellow setae, anterior margin only very feebly emarginate in the middle, lateral angles broadly rounded; clypeuswithlongersetaealong anterior margin; frontoclypeal suture straight. Eyes large, protruding beyond outline of head, suboval in lateral view, bordered by long black setae from inner side; frons simple, without grooves or sutures. Maxillary palpus distinct, terminal palpomere longest and widest, truncate apically with microreticulate distal, flat surface. Labium membranous apically; labial palpus distinctly smaller than maxillary palpus, terminal segment robust, rounded apically, segments 1-2 with long yellow setae. Antennae with 11 antennomeres, setose, long, almost reaching base of pronotum; scape ca twice as long as pedicel or other segments, almost straight; segments 3–11 subequal in size, subtriangular, not forming elongated club.

Thorax. Pronotum ( Figs 1, 3 ) widest at base, anterior margin straight, PW: males 2.52 (2.41-2.74) mm, females 2.64 (2.36–2.91) mm, PL: males 1.7 (1.62–1.92) mm, females 1.66 (1.45–1.82) mm; base broadly sinuate on each side and narrowly so in front of scutellum; posterolateral angles strongly produced, acute; two short prescutellar pits; disc convex, without median groove and sublateral carinae, sublateral grooves very finely indicated at base; sides convex, lateral margins very narrowly explanate; admedian prebasal pits shallow, slightly elongated. Hypomeron sinuate, wider at base and anterior end, constricted around procoxa. Prosternal process ( Figs 2, 4 ) triangular, about as long as wide at base, sides slightly constricted before rounded apex; prosternum in front of coxae extremely short; surface of prosternum densely setose. Mesoventrite ( Figs 2, 4 ) short and wide, with deep narrow mesal depression; sides around coxae rised; basal margin bisinuate. Metaventrite ( Figs 2, 4 ) smooth, discrimen distinct, reaching anterior and posterior margin. Elytra ( Figs 1, 3 ) with 10 rows of punctures largest on disc, sides parallel in anterior ca ¾, then more or less sharply tapering toward apices, which are spinose, around 2.2 times as long as wide; EL: males 6.54 (6.08–7.31) mm, females 7.09 (6.18–7.45) mm; EW: males 2.93 (2.81–3.15 mm, females 3.18 (2.82–3.45) mm; disc without tubercles or accessory rows; epipleuron wider along metaventrite, than narrow, setose. Scutellum subtriangular, all three sides arcuate. Legs long and slender; coxae moderately widely separated; femora and tibiae flattened; profemora widest; mesotibiae pale, metatibiae longest, with pale curved setae in males ( Fig. 9 ); tarsal claws large and acuminate.

Abdomen ( Figs 2, 4 ) setose; intercoxal process of first ventrite triangular, carinae of ventrite 1 behind coxae absent; ventrites transverse, ventrites 3 and 4 with posterolateral angles slightly produced, ventrite 5 about as long as ventrite 2, triangular, with apical tuft of dense yellowish setae. Aedeagus ( Figs 5–7 ) elongate, fibula absent, corona membranous in basal 1/3 of penis; parameres ca. 0.4 times as long as median lobe, widest at middle, narrowed toward rounded apex (lateral view); median lobe slender, in dorsal / ventral view asymmetrical, constricted behind middle, narrowed behind constriction, distal ca 0.6 parallel-sided, apex acuminate; in lateral view median lobe bisinuate, narrow in distal half, basal half wider; phallobase long, ca 1.3 times longer than median lobe, straight, parallel-sided in dorsal / ventral view, narrowed distally in lateral view. Ovipositor ( Fig. 8 ) with terminal segment (stylus) short, straight, slightly widened towards base; preterminal segment stout, abruptly widened basally, apically densely setose, ca 2.7 times as long as terminal segment; distal segment produced medio-basally; basal segment ca. twice as long as preterminal and distal segments combined, spurs curved.

Sexual dimorphism: Males differ from females by slightly smaller size, longer antennae, depressed disc of metaventrite, protibia much more widened, metatibia with stout pale setae, abdominal intercoxal process depressed in males (convex in females) and excised apex of ventrite 5.

Distribution: D. otongachi is known only from the type locality ( Fig. 10 ), Rio Toachi in the Otongachi reserve.

Differential diagnosis. D. otongachi can be easily distinguished from congeners by its long antennae and the unique asymetrical median lobe in the male genitalia.

Etymology: The new species was named after Reserva Otongachi, where it was collected.

Note: Of the three specimens used for molecular analysis, DNA was successfully extracted from two, the sequences of the barcoding fragment are freely available in www.boldsystems.org, records ELMSA049-16 and ELMSA398-19. Besides D. otongachi DNA barcodes, five Disersus barcoding fragment (5 ‘COI) sequences are currently published and freely available in databases. However, according to the voucher photo (www.boldsystems. org), two represent other taxa (MZCRI3369-13 is a larva of Psephenidae and MZCRI3368-13 is an unspecified larva of Elmidae , but it is certainly not a Disersus larva). The remaining three sequences represent 2 Disersus species , D. inca from Ecuador (ELMSA045-16) and Disersus sp. from Costa Rica (MZCRI570-13, MZCRI577-13). D. inca is significantly phylogenetically distant from D. otongachi (~ 13% K2P distance). Disersus sp. from Costa Rica is clearly more related (2.3-3.6%), but still sufficiently genetically different at the species level.

Figures

FIGURE 10. Type locality of Disersus otongachi sp.nov., Toachi River, Otongachi Reserve, province Santo Domingo de los Tsachilas, Ecuador.

FIGURES 5–9. Disersus otongachi sp.nov.: 5) aedeagus dorsal view, 6) aedeagus ventral view, 7) aedeagus lateral view, 8) ovipositor ventral view, 9) male metatibia lateral view. Scale bars: 5–8: 0.1mm, 9: 1mm.

FIGURES 1–4. Habitus of Disersus otongachi sp.nov.: 1) male, dorsal, 2) male, ventral, 3) female, dorsal, 4) female, ventral. Scale bar: 1mm.