Heleniella helvetica, J. Moubayed-Breil & B. Lods-Crozet, 2016

J. Moubayed-Breil & B. Lods-Crozet, 2016, Heleniella helvetica sp. n., a cold stenothermic species inhabiting the upper Rhône catchment in central Switzerland [Diptera, Chironomidae, Orthocladiinae], Journal of Entomological and Acarological Research 48 (6026), pp. 339-344 : 340-341

Heleniella helvetica sp. n.

Material examined: Holotype. Switzerland. Upper catchment of the Rhône River, springfed stream (tributary of the Mutt stream), crenal, altitude 2600 m, 1 male adult, leg. B. Lods-Crozet, 17.09.1997.

Paratypes (all leg. B. L-C). Switzerland. Same locality as holotype and Mutt stream, 6 male adults, leg. B. Lods-Crozet, 19.09.1997.

Holotype (on 1 slide) (GBIFCH 00190363) and 2 male paratypes (mounted on 2 slides)) (GBIFCH 0 0 190364 + GBIFCH00190365) are deposited in the collections of the ‘Musée cantonal de Zoologie, Palais de Rumine , 6 place de la Riponne, CH-1014 Lausanne, Switzerland. Remaining paratypes are deposited in the collection of the senior author’s. Type material was preserved in 75% alcohol, and later mount- ed in polyvinyl lactophenol. For each adult, the head, thorax and abdomen were cleared in 90% lactic acid before mounting on slides.

Etymology: the new species is named heloetica after the name of ‘Swiss confederation’ given in Italian of the country of Switzerland, where the type material was collected.

Diagnostic characters

Adult male: Small sized species with a brownish general colouration. H. heloetica sp. n. closely resembles H. extrema . They are considered as sister species, which can be easily distinguished from all other members of the Heleniella genus in having an unusual twisted gonostylus, which is bearing a median prominence where is inserted the megaseta. However, the new species is separated from H. extrema and from the remaining Heleniella species by the following characters found in the male adult: - AR 0.50-0.51; thorax with 33-35 antepronotals, 40-45 dorsocentrals, 24-26 prealars, 16-17 episternals, 45-50 preepisternals and 42-44 scutellars; wing length 1.65-1.85; low value of the BR (PI, 1.83; PII, 1.50; PIII, 1.60); - virga very long (145-150 µm long), consisting of 2 long filaments; - tergite IX with semicircular margin, which is bearing 10-12 setae (5-6 on each side of the anal point); anal point conical, broad at base and paralle-sided medially; - inferior volsella long nose-like, projecting and bent downwards; - gonostylus unusually twisted and contorted, truncate proximally, broader and sub-rectangular distally with a truncate apex, magaseta placed medially on a cylindrical to cup-like projecting prominence, crista dorsalis absent.

Male imago

(n = 5; Figures 1-3 , 5-8 , 11-15 )

Small sized species. Total length 2.10-2.20 mm. Wing length 1.65- 1.85 mm. General colouration brown to dark brown with blackish head; antenna brown to dark brown; thorax brown to dark brown; mesonotal stripes distinct; legs light brown to brown, tarsomere of PI, PII and PIII darker than remaining tarsomeres; abdomen brown to dark brown, anal segment dark brown.

Head ( Figure 1 ). Eyes pubescent, inner eye margin bare; proximal part of eye enlarged, distal part narrowed downwards. Temporals consist of about 33-35 setae including 21-22 inner verticals and 10-11postorbitals; distal area of the eye bare. Palp 5-segmented; first palpomere weakly developed; length (µm) of palpomeres 20, 50, 75, 85, 115; sensilla clavata present on distal part of third segment. Antenna 13-segmented, 750-760 µm long; sensilla chaetica present on segments 2-3 and 13; antennal groove indistinct, beginning on segments 4-5 and reaching ultimate flagellomere; last flagellomere nearly clubbed apically, 250-260 µm long, remaining segments 500-510 µm long; AR 0.50-0.51. Thorax ( Figures 2-3 ). All thoracic setae are decumbent except for the dorcentrals, which are arising from distinct pale spots. Acrostichals absent. Humeral pit as in Figure 2 . Antepronotum densely covered with setae (33-35), antepronotal lobes in close contact; dorsocentral area densely covered with setae (about 55 setae in 1-3 rows), prealars 24-27 in 2-3 rows, episternals about 45-50, preepisternals about 40-45. Scutellum with 44 setae placed in 3-4 rows rows. Wing. Brachiolum with 2 setae. Distribution of setae on veins: R, 13-14; R1, 6-7; remaining veins bare. Squama bare. Legs. The low value of the BR ratio (1.50-1.83) apparently represents a consistent distinguishing character (PI, 1.83; PII, 1.50; PIII, 1.6). Tarsomere 5 of PI weakly shorter than tarsomere 4. Pulvilli apparently absent. Average length (µm) and proportions of legs:

Abdomen. Hypopygium in dorsal, ventral and lateral view ( Figures 5-8 ). Tergite IX broad and circular, anteromedian area bare, posterior area with 8-10 setae (4-5 placed on each side of the base of the anal point), posterior margin broadly expanded and bearing 10-12 setae (5- 6 on each side of the anal point). Anal point ( Figures 5, 7, 8 , 11 ) 23-25 µm long, maximum width 20-21 µm at base, minimum width 9-11 µm at apex, broad at base and narrowed distally, apex rounded in both dorsal ( Figures 5 , 11 ) and lateral view ( Figures 7-8 ); presence of 3 setae on dorsal side and 6 on lateral side (3 on each side). Phallapodeme and sternapodeme as in Figure 6 . Sternapodeme arc-like orally produced, lateral sternapodeme nearly vertical; phallapodeme 90-95 µm long, broadly linear basally and medially, hammer-like at base. Virga ( Figures 5 , 12 ) 145-150 µm long, consists of 2 fused long filaments elongated vertically. Gonocoxite 180-185 µm long, 45-50 µm wide, apex rounded to nearly truncate; basal margin sinuous, inferior volsella 7 5-80 µm long, maximum width 75 µm, minimum width 9 µm; long nose-like lobe shaped, rounded apically, bearing 5-7 setae dorsally and ventrally on distal part. Gonostylus ( Figures 5, 8 , 13-15 ) 75 µm long, maximum width 30 µm, unusually shaped, twisted and contorted; crista dorsalis absent. Megaseta 18 µm long, inserted medially on a cylindrical to cuplike prominence projecting on the anteromedian part of the gonostylus; the prominence is about 23 µm high and probably retractable.

Larva: known but not described.

Taxonomic remarks

Male imaginal characters of H. heloetica sp. n. are nearly similar to those of H. extrema . These two species can be considered as sister species based on the following common characters: - both species are bearing an unusual gonostylus, which is twisted and characterized by the placement of the megaseta on its median part ( Figures 5, 8 13-15 for H. heloetica sp.n.; Figures 10 , 22 for H. extrema ); - both species are confined to cold stenothermic high mountain streams (crystalline water for H. heloetica sp. n.; karstic water for H. extrema ).

The extrema -group is emended here as well as in Moubayed-Breil (unpublished data, 2016) according to the unusual shape of the gonostylus, which is contorted and bearing the megaseta medially. This group currently includes H. extrema , H. heloetica sp. n. and two additional new undescribed species known from glaciers located in C- Switzerland (H. sp. 1) and the Eastern Pyrenees, France (H. sp. A). However, H. heloetica sp. n. is easily distinguished from other members of the Heleniella genus and in particular from H. extrema by a combination of differentiating characters including: - AR 0.50-0.51; wing length 1.65-1.85; - distribution pattern of setae on tergite IX and anal point ( Figures 5 , 11 ), otherwise figured in H. extrema ( Figure 9 ; Albu 1972, Figure 2 ); - anal point broadly rectangular at base and parallelsided medially ( Figures 5 , 11 ), while it is triangular and narrowed in H. extrema ( Figure 9 ) and absent in H. sp. 1 ( Figure 16 ); - phallapodeme broadly linear proximally and medially ( Figure 16 ), thicker in H. extrema ( Figure 10 , 21 ) and sickle-like in H. sp. 1 ( Figure 19 ); - virga composed of 2 fused long filaments ( Figures 5 , 12 ), differently shaped in H. sp. 1 ( Figures 17-18 ); - inferior volsella long nose-like shaped and projecting downwards ( Figures 5, 8 , 15 ), broader and sub-rectangular in H. extrema ( Figure 9 ); - gonostylus distinctly twisted ( Figures 5, 8 , 13-15 ) and bearing a cylindrical median prominence, differently figured in H. extrema ( Figures 10 , 22 ) and H. sp. 1 ( Figure 20 ).

Figures

Figures 1 - 4. Male imago of Heleniella spp. Heleniella helvetica sp. n.: head, temporals (1); humeral pit with prealars and some episternals (2); thorax (3). H. extrema, thorax with dorsocentrals and scutellars, after Albu (1972, Figure 1) (4).

Figures 5 - 10. Male imago of Heleniella spp. Heleniella helvetica sp. n.: hypopygium, dorsal (5) and ventral (6); anal point in lateral view (7); anal point and gonocoxite in lateral view (8). H. extrema: anal point and inferior volsella, dorsal, after Albu (1972, Figure 2) (9); gonocoxite with sternapodeme, phallapodeme and right gonostylus, ventral, after Albu (1972, Figure 2) (10).

Figures 11 - 22. Male imago of Heleniella spp. Heleniella helvetica sp. n.: anal point and distribution pattern of setae on tergite IX (11); virga (12); right gonostylus, dorsal (13); left gonostylus, ventral (14); inferior volsella and gonostylus, dorsal (15). H. sp. 1 (central Switzerland): tergite IX lacking anal point (16); virga, two aspects (17 - 18); phallapodeme (19); right gonostylus (20). H. extrema: p hallapodeme, after Albu (1972, Figure 2) (21); left gonostylus, dorsal, after Albu (1972, Figure 2) (22).