Chaetocladius lodscrozetae Moubayed-Breil

Moubayed-Breil, Joel & Lods-Crozet, Brigitte, 2018, On the genus Chaetocladius s. str. Kieffer, 1911 from Switzerland with descriptions of five new relic species occurring in glacial alpine springs and streams (Diptera, Chironomidae), Alpine Entomology 2, pp. 15-34 : 19-21

Chaetocladius lodscrozetae Moubayed-Breil sp. n.

Material examined.

Holotype. Switzerland: Gletschboden alluvial plain, streamlet and springs located close to the upper catchment of the Rhône River, upstream of the Mutt stream confluence (station U2), altitude 1800 m, 08.IX.1998, 46°34'15.466"N, 8°22'47.054", 1 male adult, leg. B. Lods-Crozet. Environmental data of Rhône water are: crystalline water, conductivity 3.3-17.8 µS /cm; temperature 2-4 °C during late spring to late summer (June-September).

Paratypes (all leg. B. Lods-Crozet). Switzerland. 1 male adult, same locality and data as for holotype. 2 male adults, Gletschboden, upstream, altitude 1800 m, 30.IX.1999. 1 male adult, Mutt stream (station M4), altitude 2100 m, 07.VIII.1997, Swiss coordinates: 2 ’674’ 059, 1 ’157’ 904. Environmental data of Mutt stream water are: crystalline/calcareous water; conductivity: 61-183 µS /cm; temperature: 1-8 °C during late spring to late summer (June-September). In the streamlet and rheocrenes located near the station M4, conductivity ranged between 103 to 253 µS /cm; temperature 4.4. to 14.8 °C ( Ilg et al. 2001).

Holotype (mounted on 1 slide; GBIFCH 00460693) and 1 male paratype (on 1 slide; GBIFCH 00460694) 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.

Diagnosis.

The nearest species to C. lodscrozetae sp. n. are C. dissipatus , C. holmgreni , C. egorych and C. aedeagolobatus Rossaro, Magoga & Montagna, 2017 from which it can be separated in having: clypeus half diamond-like, with V-shaped posterior side, bearing 6 setae placed in 2 rows; palpomere 4 distinctly truncate apically, sensilla clavata present on segment 3 including 5 sparsely distributed and 3 (tubule-like) grouped on a ring placed distally; ultimate flagellomere 465-475 µm long, distinctly clubbed, AR about 1; tergite IX broad and semi-circular with 16-22 dorsal setae placed on its posterior part; anal point long, triangle-like, nearly parallel-sided and distinctly thin between base and apex, dorsally bearing a characteristic massive lamella-like orally directed structure which is markedly visible in lateral view, lamella is cup-like in dorsal view, composed of 2 well separate margins, inner margin linear and bare, outer margin markedly undulated and bearing 7-8 dorsolateral setae, inside area bare; virga typical inversed V-shaped, composed of 6-7 posteriorly directed spines; gonocoxite broad basally and narrowed distally, abruptly tapering before apex; inferior volsella extending from base of gonocoxite to its distal part, consist of 2 lobes (dorsal lobe markedly projecting medially and beak-like in shape, distal part distinctly swollen and pouch-like in shape; ventral lobe swollen basally and tapering distally, ending nearly at tip of gonocoxite, inner ventral margin bearing about 11 strong setae; gonostylus half bulb-shaped ending with a distinct hyaline rounded distal area, anterior side with orally directed small setae, posterior margin markedly rounded bearing a double inner apical margin, anterior margin varies from straight to convex, crista dorsalis low and indistinct.

Description.

Male imago (n = 4 male adults; Figs 32-44). Medium sized species. Total length 3.80-3.90 mm. Wing length 2.00-2.13 mm. General colouration contrasting brown to dark brown. Head dark brown, antennae pale brown, thorax brown to dark brown, mesonotal stripes distinctly dark brown; wing pale; legs contrasting brown to dark brown. Tergites I-VI/VII brown, tergites VII-VIII and anal segment entirely dark brown.

Head. Eyes bare, hairs present anterior part of inner eye margin. Temporals consist of 11-12 setae including 7-8 uniserial inner and 4 outer verticals. Antenna 915-920 µm long, 13-segmented; ultimate flagellomere 465-475 µm long, distinctly clubbed distally and bearing a dense brush of curved sensilla chaetica apically, apex (Fig. 34) lacking pre-apical setae; antennal groove beginning on segments 3-4 and reaching ultimate flagellomere; AR 1.02. Clypeus (Fig. 35) about 105 µm maximum height and 120 maximum width, half diamond-like, with V-shaped posterior side, which is rounded apically, bearing 6 setae placed in 2 rows: 4 near the basal margin, 2 on median part. Palp 5-segmented, first and second palpomeres fused; palpomere 4 distinctly truncate apically; length (µm) of segments: 38, 75, 150, 130, 175-180; palpomere 3 (Figs 32-33) with sensilla clavata including 5 sparsely distributed and 3 grouped on a characteristic ring placed distally. Thorax. Antepronotum well developed, with fused lobes. Lateral antepronotals 5 grouped close together apically; acrostichals 10-11 uniserial; dorsocentrals 8-9 in 1 row, prealars 3; humeral pit ovoid, lacking contrasting spots. Scutellum with 8 setae in 1 row (4 placed on each side of median area). Wing. Brachiolum with 1 seta. Membrane densely covered with coarse punctuation. Distribution of setae on veins: R, 10-11; R1, 0-1; remaining veins bare. Squama with 5-10 uniserial setae. Legs. Tibial spurs of PII and PIII are Chaetocladius -type, with projecting apicolateral denticles. Sensilla chaetica present on: tibia and tarsomere ta1 of PI and PII; tarsomeres ta1-ta3 of PIII. Length (µm) and proportions of legs as in Table 3.

Hypopygium in dorsal, ventral and lateral view as in Figs 36-44; ventral view (Fig. 37) with tergite IX and anal point removed. Tergite IX broad and semi-circular with 16-22 dorsal setae placed on the posterior part (7-8 setae on each side of base of anal point); presence of a characteristic massive rounded prominence extending from the median area to base of anal point; prominence is cup-like in shape in dorsal view (Fig. 36) and orally directed in lateral view (Fig. 40), outer margin is markedly undulated and bearing 8-10 dorsolateral setae (4-5 placed on each side), inside area bare. Anal point (Figs 36, 40) about 80-85 µm long, maximum width 40-45 µm at base, markedly elongated and reaching inner lobe of inferior volsella; in dorsal view (Fig. 36), median and distal part linear to parallel-sided with an average of 3-5 µm wide; in lateral view (Fig. 40), distinctly thicker on proximal half, becoming thinner on its distal half, often bent downwards, apex slightly curved upwards. Laterosternite IX with 5 setae on each side. Transverse sternapodeme arc-like, with distinct rounded oral projections; lateral sternapodeme slender and distinctly short; phallapodeme sinuous medially at joint with lateral sternapodeme. Virga (Fig. 38) inversed V-shaped, composed of 6-7 posteriorly to laterally directed spines. Gonocoxite 280-285 µm long, markedly broad basally, maximum width 85-90 µm, narrowed and abruptly tapering distally, apex rounded and bearing 4-5 apical setae; inner ventral margin with about 11 strong setae; apical margin with 2-3 stout setae. Inferior volsella 120 µm long, maximum width 45 µm, extending from base of gonocoxite to its distal part (about 65 µm distance from apex of gonocoxite); similarly shaped in both dorsal, ventral and lateral view (Figs 36-37, 39, 41); median inner margin terminating in a nose-like lobe which is hyaline, bare and bent downwards; distal part pouch-like in shape. Gonostylus (Figs 41-44) 100-110 µm long, 40-45 µm maximum width, nearly semi-circular, distal part of posterior margin bare and hyaline; anterior side smooth in general, varies from straight (Figs 42-43) to convex (Fig. 44), bearing numerous orally directed small setae; crista dorsalis low and indistinct; megaseta 18-20 µm long, conspicuous, occasionally with pointed apex, slightly bent inwards.

Taxonomic position.

C. lodscrozetae sp. n. keys close to C. dissipatus , C. holmgreni , C. egorych and C. aedeagolobatus from which it can be separated in having: sensilla clavata present on palpomere 3 including 5 sparsely distributed and 3 grouped on a characteristic ring placed distally; tergite IX broad and nearly semi-circular with 10-11 setae on its posterior area, presence of a characteristic massive rounded prominence extending from the median area to base of anal point; anal point elongated and parallel-sided which is distinctly thicker on its proximal half; virga inversed V-shaped, composed of 6-7 posteriorly directed spines; gonocoxite broad basally and narrowed distally, abruptly tapering before apex; inferior volsella extending from base of gonocoxite to its distal part, consist of a large lobe which is pouch-like in shape, inner margin terminating in a hyaline nose-like lobe which is bare and bent downwards; gonostylus nearly semi-circular, distal part of posterior margin hyaline and bare, anterior side with orally directed small setae, anterior margin varies from straight to convex.

Etymology.

The new species is named lodscrozetae in honour of Dr. Brigitte Lods-Crozet from the Cantonal Museum of Zoology of Lausanne (Switzerland), who is still active as researcher and hydrobiologist in contributing to preserve the biological and ecological quality of water and environment in Switzerland.

Ecology.

Glacial springs and cold mountain streams with crystalline to calcareous water. Emergence: from July to early September.

Geographical distribution.

C. lodscrozetae sp. n. is only known from rheocrenes and lotic habitats delimited by the Gletschboden floodplain, the Mutt stream and streamlet, Swiss Alps, altitude 1800-2100 m.