Ictelmis, Čiampor & Linský & Čiamporová-Zaťovičová, 2019

Čiampor, Fedor, Linský, Marek & Čiamporová-Zaťovičová, Zuzana, 2019, Ictelmis, a new riffle beetle genus from Ecuador (Coleoptera: Elmidae), Zootaxa 4695 (5), pp. 483-491 : 484-489

Ictelmis gen. nov.

Type species: Ictelmis martae sp. nov.

Description: Body obovate ( Figs 2–3 ), 0.99–1.21 mm long, 0.47–0.57 mm wide; dorsum convex. Surface shiny with sparse, pale setae. Colour: head and body dorsally black, antennae, coxae, trochanters, femora (with darkened apices), tibiae, tarsi and tarsal claws yellowish. Hairy or scale-like tomentum distributed on following areas: genae, lateral margin of proventrite and mesoventrite, epipleura, femora except apex, partly on meso- and metacoxae, laterally on metaventrite and abdominal ventrites.

Head narrower than pronotum, retractile, rounded, dorsally microreticulate. Clypeus shorter and wider than labrum, finely grooved, sparsely setose; frontoclypeal suture visible. Labrum ( Fig. 5 ) slightly wider than long, anterior margin almost straight, anterior angles wide, densely setose, tormal processes narrow. Mandible ( Fig. 7 ) short, moderately broad, symmetrical; external outline entire, only very feebly incised subapically, apex curved with three obtuse teeth, molar part with pores. Prostheca large, entirely membranous with numerous apical finger-like outgrowths. Maxilla ( Fig. 6 ) with cardo and stipes moderately short. Maxillary palp 4-segmented, segments 1–3 short and wide, terminal segment almost twice as long as segments 1–3 combined. Galea elongate, slightly curved, sub-equally long and as wide as maxillary palp. Lacinia about twice as wide as galea, longer than wide, subrectangular. Apex and inner side with dense, long, curved setae. Labium ( Fig. 8 ): submentum broad subpentagonal; mentum transverse, as wide as submentum, very short, apical angles with long setae; prementum elongate, anterior half widened, lateral angles membranous with blunt setae, anterior margin densely setigerous. Labial palp 3-segmented, first segment short and wide. Second segment more than twice as long as first, distally widened. Third segment suboval, equally wide as segments 1–2, about twice longer than the second segment. Antennae filiform, 11-segmented ( Fig. 9 ); pedicel about twice as long as scape, remaining segments about four times longer than scape and pedicel combined, segments 3–10 short, subequal in length; terminal segment longer, suboval, with apex pointed and feebly darkened, with subapical sensory field. Eyes well developed, hemispherical, with around 30 ocelli.

Pronotum subparallel, widest in middle; surface finely microreticulate; disc convex; with broad transverse impression in anterior half, interrupted by medially raised line; sublateral carinae well developed from base to middle; two feebly impressed prescutellar foveae; anterior margin shallowly sinuate; anterior angles slightly produced; lateral margins narrowly rimmed; basal margin almost straight, feebly produced medially in front of scutellum; posterior angles orthogonal. Hypomeron shiny, microreticulate, subparallel, slightly constricted anteriorly. Proventrite ( Fig. 4 ) coarse, elongate; portion in front of procoxae slightly longer than basal portion; prosternal process parallel-sided, lateral margins raised, anteriorly extending to carinae on sides of disc almost reaching anterior margin; posterior margin of process truncate with medial protuberance. Mesoventrite short and wide, coarse, with oblique carinae and deep narrow groove for reception of prosternal process. Metaventrite slightly wider than long, coarse; discrimen in basal 2/3; sides of disc with carinae extending from posterior margin of mesocoxae, reaching almost anterior margin of metacoxae. Elytra convex, widest in anterior 2/3; sides strongly declivous; surface wrinkled, partly shiny, with dense tiny punctures; elytral margin narrowly rimmed; humeri indistinct; epipleuron thin, tapering posteriorly. Prominent carina on fifth interval reaching 4/5 of elytron length. Elytra with seven visible rows of punctures. Scutellum subovate. Legs moderately long; femora clavate, markedly widened in middle. Hind wings reduced. Tarsi 5-segmented, first four segments each with one fine pale seta, fifth segment slightly shorter than remaining segments combined; claws with distinct basal and subbasal teeth.

Abdomen with 5 ventrites. First ventrite with basal margin broadly rounded, ventrites 3, 4 with slightly produced distal angles, ventrite 5 simple with lateral spines ( Figs 10–11 ). Aedeagus ( Figs 12–13 ) elongate; penis parallel-sided, with evenly narrowed rounded apex in lateral view, evenly curved in lateral view; fibula indistinct or absent; corona well developed; parameres absent; phallobase about 0.6 times as long as penis, parallel-sided. Ovipositor ( Fig. 14 ) with terminal segment (stylus) short, curved with wide base and acute apex; preterminal segment stout, subparallel, ca 3.3 times as long as terminal segment, bearing numerous small spines and sensilla, apex produced laterad, with sensory field; basal segment ca. 1.7 times as long as preterminal and distal segments combined, straight.

Sexual dimorphism. Female externally very similar to male, in average slightly larger ( Fig. 3 ), ventrite 5 shorter in male ( Fig. 10 ).

Habitat and Distribution: smaller or larger, relatively fast-flowing streams in forest with organic matter, stones, gravel and sand. So far known only from few localities in Ecuador ( Fig 15 ).

Etymology. The generic name Ictelmis is derived from generic name of the Yellow-tailed oriole ( Icterus mesomelas ), a beautiful yellow-black bird common in Ecuador and “ elmis ”, from the nominate genus of the family, Elmis . Gender: feminine.

Differential diagnosis. Ictelmis gen. nov. is the fourth Neotropical genus of small sized Elmidae with distinctly clavate femora (other three are Onychelmis , Notelmis and Neolimnius Hinton, 1939 ). From the latter two it can be easily distinguished by the presence of basal and subbasal teeth on claws and from all three genera by possessing longitudinal carinae only on fourth elytral interval, instead of none or one on sixth ( Onychelmis ), on sixth and eighth ( Notelmis ) or on third and fifth ( Neolimnius ). The presence of well developed sublateral carinae on pronotum clearly distinguishes Ictelmis gen. nov. from Notelmis and Onychelmis (few species of the latter genus have feeble short remnants, but never fully developed carinae). From Onychelmis , with which Ictelmis gen. nov. is obviously most closely related, it can be easily distinguished by the combination of the following characters: 1) microreticulate pronotum; 2) pronotal sublateral carinae extending from base to middle; 3) absence of admedian prebasal setal tufts on metaventrite in males; 4) elytra with seven visible rows of punctures; 5) carinae on lateral sides of metaventrite disc; 6) rugose surface of ventral side.

Ictelmis martae sp. nov.

Figs 1–13

Material examined: Holotype ( PUCE) ♂ „ Ecuador, Morona-Santiago prov., tributary of Río Crusado , 03˚02’57.0” S, 78˚30’03.2” W, 979m a.s.l., 24.8.2013, stream ca 2m wide, in forest, with gravel, stones, leaf debris, submerged wood with moss, Čiampor & Čiamporová-Zaťovičová lgt .“ Paratypes ( PUCE, CCB, NMW) 13 ♂♂, 12 ♀♀ with the same data as holotype ; 1 ♂: „ Ecuador, Morona-Santiago prov., Indanza env., Río Crusado, 03˚02’55.0” S, 78˚30’03.5” W, 972m a.s.l., 24.8.2013, stream ca 5m wide, fast flowing with rapids, in forest, with gravel, boulders, Čiampor & Čiamporová-Zaťovičová lgt.“; 1 ♀: „ Ecuador, Morona-Santiago prov., San José env., Río Esperanza , 03˚06’10.9” S, 78˚28’19.2” W, 1236m a.s.l., 28.8.2013, stream ca 4m wide, shaded, with boulders, stones, gravel, wood, leaf debris, Čiampor & Čiamporová-Zaťovičová lgt .“

Description. Body obovate ( Fig. 2 ), convex dorsally, dark brown to black dorsally, ventral side paler, appendages yellowish. Length (CL) in males 0.99–1.08 mm (Ø 1.03 mm), in females 1.05–1.21 mm (Ø 1.15 mm); greatest width (EW) in males 0.48–0.52 mm (Ø 0.50 mm), in females 0.52–0.57 mm (Ø 0.54 mm); Surface shiny with sparse, pale setae. Tomentum distributed on genae, lateral margin of proventrite and mesoventrite, epipleura, femora except apex, partly on meso- and metacoxae, laterally on metaventrite and abdominal ventrites.

Head partly retractile into pronotum, dorsally microreticulate, width (HW) in males 0.22–0.25 mm (Ø 0.23 mm), in females 0.24–0.27 mm (Ø 0.25 mm). Clypeus shorter and wider than labrum, finely grooved, sparsely setose; frontoclypeal suture visible. Labrum ( Fig. 3 ) wider than long, anterior angles wide, densely setose, tormal processes narrow. Mouth parts ( Figs 3–6 ). Antennae filiform ( Fig. 7 ), pedicel about twice as long as scape, remaining segments about four times longer than scape and pedicel combined; segments 3–10 short, subequal in length; terminal segment longer, suboval with apex pointed and feebly darkened, with subapical sensory field. Eyes well developed, hemispherical.

Pronotum subparallel, length (PL) in males 0.33–0.39 mm (Ø 0.37 mm), in females 0.36–0.42 mm (Ø 0.39 mm), widest in middle, PW in males 0.31–0.37 mm (Ø 0.34 mm), in females 0.36–0.37 mm (Ø 0.37 mm), finely microreticulate, with broad transverse impression before middle interrupted by medially raised line, sublateral carinae from base to middle, two feebly impressed prescutellar foveae; anterior margin shallowly sinuate; anterior angles finely produced; lateral margins narrowly rimmed; basal margin almost straight, feebly produced medially in front of scutellum; posterior angles orthogonal. Hypomeron shiny, microreticulate, subparallel, slightly constricted anteriorly. Proventrite ( Fig. 4 ) coarse, elongate; prosternal process parallel-sided, lateral margins raised, anteriorly extending to carinae on sides of disc almost reaching anterior margin; posterior margin of process truncate with medial protuberance. Mesoventrite short and wide, coarse, with oblique carinae and deep narrow groove. Metaventrite slightly wider than long, coarse; discrimen in basal 2/3; sides of disc with carinae extending from posterior margin of mesocoxae, reaching almost anterior margin of metacoxae. Elytra convex, widest in anterior 2/3; surface wrinkled, with dense tiny punctures; elytral margin narrowly rimmed; humeri indistinct; epipleuron thin, tapering posteriorly. Prominent carina on fifth interval reaching 4/5 of elytron. Elytra with seven visible rows of punctures. Scutellum subovate. Legs moderately long; tarsal segments 1–4 each with one fine pale seta, fifth segment slightly shorter than segments 1–4 combined; claws with distinct basal and subbasal teeth.

Abdomen. First ventrite with basal margin broadly rounded between coxae, ventrites 3, 4 with slightly produced distal angles, ventrite 5 with lateral spines ( Figs 10–11 ). Aedeagus ( Figs 12–13 ) elongate; penis parallel-sided, with evenly narrowed rounded apex in lateral view, evenly curved in lateral view; fibula absent; corona well developed; parameres absent; phallobase about 0.6 times as long as penis, parallel-sided. Ovipositor ( Fig. 14 ) with terminal segment (stylus) short, curved with wide base and acute apex; preterminal segment stout, subparallel, ca 3.3 times as long as terminal segment, bearing numerous small spines and sensilla, apex produced laterad, with sensory field; basal segment ca. 1.7 times as long as preterminal and distal segments combined, straight.

Sexual dimorphism: Ventrite 5 in females longer than in males ( Figs 10–12 ).

Habitat: So far, the only species of the new genus has been recorded in several small, relatively fast-flowing streams in forest with organic matter, stones, gravel and sand ( Fig 15 ).

Etymology. This species is dedicated to our amazing colleague, friend, positive person and very good freshwater plankton expert Marta Illýová, who unfortunately untimely passed away, and we are still missing her.

Figures

FIGURE 1. Maximum likelihood tree of Ictelmis and related genera, produced based on COI barcoding fragment.

FIGURES 2–3. Habitus of Ictelmis martae gen. et sp. nov.: 2) holotype male, 3) female. Scale: 0.5 mm.

FIGURE 4. Venter of Ictelmis martae gen. et sp. nov. (holotype male). Scale: 0.5 mm.

FIGURES 5–9. Ictelmis martae gen. et sp. nov.: 5) labrum, dorsal view; 6) right maxilla, dorsal view 6a) galea, lateral view; 7) left mandible, dorsal view; 8) labium, ventral view; 9) antenna. Scale: 0.1 mm.

FIGURES 10–11. Ictelmis martae gen. et sp. nov. ventrite V, ventral view: 10) male; 11) female.

FIGURES 12–14. Ictelmis martae gen. et sp. nov. genital segments: 12) aedeagus, ventral view; 13) aedeagus, lateral view; 14) ovipositor, ventral view. Scale: 0.1 mm.

FIGURE 15. Distribution map and examples of typical localities of Ictelmis martae gen. et sp. nov.