Heleniella, Gowin, 1943

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 : 342-344

Key to male adults of known Heleniella species from Europe

The following key on the male adults of known Heleniella species from Europe ( H. extrema , H. dorieri , H. ornaticollis , H. serratosioi ) is reproduced with more additional morphological details provided based on other new described species from continental France, Corsica and Lebanon (Moubayed-Breil, unpublished data, 2016).

1. Gonostylus of usual Heleniella type, linear, triangular or broadened distally; apex projecting, nearly right angle-like or rounded; megaseta inserted apically...........................................................................................

- Gonostylus unusually shaped, not of Heleniella type, distinctly twisted and contorted ( Figures 5, 8, 10 , 13-15, 22 -23), bearing a distinct or indistinct cylindrical median prominence; megaseta inserted medially.........4

2. Inferior volsella triangular, narrowed apically and projecting downwards ( Brundin, 1956, Fig. 107; Albu, 1966, Fig. 6 ; Reiss, 1968, Fig. 14 ; Ringe, 1976, Fig. 4 ; Langton & Pinder, 2007, Fig. 161A)........................3

- Inferior volsella rectangular, rounded apically and not projecting downwards; gonostylus linear with slender apex and not projecting; virga consists of 2 fused filaments extended vertically ( Ringe, 1976, Fig. 1 ) ................................................................ H. serratosioi Ringe, 1976

3. Gonostylus triangular, weakly projecting apically with a right angle to rounded apex; virga consists of 3 separated long filaments (Moubayed-Breil, unpublished data, 2016)............................................... .................................................................. H. ornaticollis (Edwards, 1929)

- Gonostylus not triangular, distinctly broadened distally, not projecting apically and ending with a rounded apex; virga unknown....................... ........................................................................ H. dorieri Serra-Tosio, 1966

4. Inferior volsella triangular and weakly projecting ( Figure 9 ); anal point triangular, narrowed distally with a nearly pointed apex ( Figure 9 ); phallapodeme rounded and turned over at base ( Figures 10 , 21 ); virga unknown...................................................................... H. extrema Albu, 1972

- Inferior volsella nose-like shaped, strongly projecting and distinctly bent downwards ( Figures 5, 8 , 15 ); anal point not triangular, broad at base, slightly narrowed distally with rounded apex ( Figures 5, 7-8 , 11 ); phallapodeme hammer-like at base ( Figure 6 ); virga 150 µm long, consists of 2 fused long filaments ( Figures 5 , 12 )........... H. heloetica sp. n.

Ecology and geographical distribution

Larvae of all members of the Heleniella genus are exclusively rheophilic and commonly encountered in lotic habitats delimited by the crenal and rhithral of cold streams. Male adults of H. heloetica sp. n. were collected in small groundwater resurgences and a springfed stream located in the upper basin of the Rhône River, Mutt stream catchment (central Switzerland, altitude 1800-2600 m). Localities where material was collected consist of moderate to weakly shaded pristine stenothermic stretches with cold mountain helocrenes and streams, including small waterfalls and riffles on rocky or sandy to gravely substrata. Bryocolous, hygropetric and madicolous habitats including waterfalls probably represent the most common and favoured aquatic areas for larval populations. Abiotic and biotic factors recorded along the crenal and rhithral waters are provided in Lods-Crozet (2012) as: - crystalline water characterized by a low value of the water conductivity (18-60 µS/cm); - cold stenothermic water temperature (4-10°C); - weakly shaded lotic habitats (waterfalls and riffles). The discovery of H. heloetica sp. n. in such preserved lotic habitats highlights the position of the headwaters in the upper Rhône catchment as a remarkable microrefugia, which is considered as an extremely important hotspot of diversity. The new species is typically rheophilic and representative of helocrenes and cold stenothermic streams. It belongs to the crenobiontic and crenophilous community of species as documented by Lindegaard (1995).

All members of the extrema -group including H. extrema , H. heloetica sp. n. and two additional new undescribed species (H. sp. 1, Switzerland; H. sp. A, France) are apparently confined to cold and stenothermic helocrenes and rhithral located in the vicinity of glaciers such those of the Mutt stream (crystalline water, C-Switzerland), Retezat Massif (karstic water, Carpathian Mountains, Rumania) and Carlit Massif (crystalline water, E-Pyrenees, France). The new described species is rare and sparsely distributed in the helocrenes and rhithral of some cold streams delimited by the upper Rhône catchment. In addition, the geographical distribution of H. heloetica sp. n. is apparently restricted to this area and therefore can be expected to occur in other similar geographic areas of the alpine mountains of Italy, Austria and France. This indicates and highlights the importance of pristine headwaters in the Alps (cold enclaves) in the preservation and persistence of autochthonous cold crenal relic species, which can be considered, in one hand as a relevant biogeographic representative and in another hand, as an eventual biological indicators of the global warming and climate change.

Chironomid species encountered in the same streams, and listed by Lods-Crozet (2012) include: Krenopelopia binotata (Wiedemann, 1817) ; Boreoheptagyia alpicola Serra-Tosio, 1989 ; Diamesa aberrata Lundbeck, 1898 ; D. bohemani Goetghebuer, 1932 ; D. cinerella Meigen, 1835 ; D. goetghebueri Pagast, 1947 , D. noaeickiana Kownacki & Kownacka, 1975 , D. oaillanti Serra-Tosio, 1972 ; Pseudodiamesa branickii (Nowicki 1873) , Syndiamesa edaeardsi Pagast, 1947 , Bryophaenocladius femineus (Edwards, 1929) ; B. suboernalis (Edwards 1929) , Chaetocladius laminatus Brundin, 1947 ; C. suecicus (Kieffer 1916) , C. cf. longioirgatus Stur & Spies, 2011; Cricotopus lygropis Edwards, 1929 ; Eukiefferiella fittkaui Lehmann, 1972 ; H. ornaticollis (Edwards, 1929) ; H. serratosioi Ringe, 1976 ; Krenosmittia boreoalpina (Goetghebuer, 1944) ; K. camptophleps (Edwards, 1929) ; Parametriocnemus boreoalpinus Gowin & Thienemann 1942 ; Stilocladius montanus Rossaro, 1979 ; Thienemannia gracilis Kieffer 1909 ; Thienemanniella caspersi Saether, 2003 ; Tokunagaia rectangularis (Goetghebuer, 1940) ; etc.

Figures

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).

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).