Chaetocladius lencioniae 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 : 17-19

Chaetocladius lencioniae Moubayed-Breil sp. n.

Material examined.

Holotype. Switzerland: Mutt stream (station M4), altitude 2100 m, 09.VIII.1997; 46°34'04.946"N, 8°24'17.159"E, 1 male adult, leg. B. Lods-Crozet. 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 station M4, conductivity ranged between 103 to 253 µS /cm; temperature 4.4. to 14.8 °C ( Ilg et al. 2001).

Paratype. 1 male adult, same locality and data as for holotype.

Holotype (mounted on 1 slide; GBIFCH 00460691) is deposited in the collections of the ‘Musée cantonal de Zoologie, Palais de Rumine, 6 place de la Riponne, CH-1014 Lausanne, Switzerland. The single paratype is deposited in the collection of the senior author.

Diagnosis.

C. lencioniae sp. n. keys near the following two species: C. gracilis , based on the shape of both tergite IX and the anal point; C. antipovae , based on the shape of the inferior volsella. However, C. lencioniae sp. n. can be distinguished in having: tergite IX semi-circular; sternite IX typically circle-like in shape; anal point markedly pointed apically and bearing setae on proximal part; virga faint, consists of 2 long teeth; gonostylus massively spherical to bulb-shaped, anterior margin swollen medially, ending in 3 characteristic small teeth comb-like placed close to the base of megaseta, posterior margin rounded, projecting downwards and terminating in a pointed sclerotized apical tooth; crista dorsalis large tooth-like, sclerotized and spherical, smooth with rounded apex, placed pre-apically close to megaseta (clearly visible in dorsal and ventral view).

Description.

Male imago (n = 2 male adults; Figs 22-31). Small sized species. Total length 3.75 mm. Wing length 2.15 mm. General colouration contrasting pale brown to dark brown except for the mesonotal stripes, which are reddish dark brown. Head brownish, antennae pale brown, thorax brown with dark brown mesonotal stripes. Wing transparent. Legs brown with dark brown tarsus. Tergites I-V brownish, tergites VI-VIII yellowish, anal segment hyaline to yellowish; gonostylus dark brown in its proximal and median part, dark brown to blackish in its distal part, megaseta and surrounding area dark brown.

Head. Eyes bare, hairs on inner eye margin absent. Temporals consist of 9-10 uniserial setae including 7-8 inner and 2 outer verticals. Antenna 1370 µm long, 12-segmented; last flagellomere (Fig. 22) 820 µm long, preceding segment 85 µm long; last flagellomere distinctly clubbed, lacking pre-apical seta and bearing a brush of curved sensilla chaetica apically; antennal groove extending from segments 3 to the ultimate flagellomere, becoming broader on last flagellomere; AR 1.50. Clypeus (Fig. 23) trapezoidal to cup-like in shape with rounded posterior margin, bearing 10 setae placed in 3 rows. Palp 5-segmented; first and second palpomeres faintly fused; length (µm) of segments: 65, 75, 205, 215, 325; 5-6 sensilla clavata are present on third palpomere. Thorax. Lateral antepronotals 3 uniserial, acrostichals 10-11 uni-biserial, dorsocentrals 14-16 uniserial, prealars 3-4 in 1 row, supraalars absent; humeral pit ovoid, nearly indistinct and lacking contrasting spots. Scutellum (Fig. 24) with 14 setae placed in 1 row along an arc line (7 on each side of the median area). Wing. Brachiolum with 1 seta. Membrane densely covered with coarse punctuation. Distribution of setae on veins: R, 13; R1, R2+3, R4+5 and remaining veins bare. Squama with 12 uniserial setae. Legs. Tibial spurs of PII and PIII are Chaetocladius -type, with prominent apicolateral denticles. Tarsomere ta4 of PII and PIII distinctly shorter than ta5; sensilla chaetica present only on tarsomeres ta1-ta3 of PI, PII and PIII (well represented on hind leg). Length (µm) and proportions of legs as in Table 2.

Hypopygium in dorsal, ventral and lateral view as in Figs 25-31; ventral view (Fig. 26) with tergite IX and anal point removed. Tergite IX semi-circular and broad with 10-11 setae placed posteriorly between base of anal point and the posterior margin (5-6 on each side). Anal point about 85-90 µm long, 65-70 µm maximum width at base, overreaching notch of inferior volsella; triangular and uniformly narrowed and sharply pointed in both dorsal (Figs 25) and lateral view (Fig. 28); base with 11-12 setae including 5-6 inserted dorsally and 6 placed on the lateral margin (3 on each side, occasionally 1 seta is inserted near the median area). Laterosternite IX typically circle-like in shape with 6-7 setae on each side. Transverse sternapodeme rounded with distinct oral projections; phallapodeme strongly broadened distally at joint with lateral sternapodeme. Virga (Figs 25, 27) faintly visible, consists of 2 long teeth about 23 µm long and fused at base. Gonocoxite 250 µm long, maximum width 95-105 µm, markedly swollen at base; inferior volsella (dorsal, Fig. 25; lateral, Fig. 31) 90-95 µm long, 30-35 µm maximum width, entirely hyaline, consists of 3 lobes; distal lobe smooth and rounded, the 2 basal lobes are strongly dented and separated by a distinct notch; posterior inner margin markedly swollen. Gonostylus (Figs 29-31) 105 µm long, maximum width 40-45 µm; massively spherical to bulb-shaped; anterior margin swollen medially, ending in 3 small characteristic pre-apical teeth, which are comb-like and pointed (clearly visible: dorsally, Fig. 29; ventrally, Fig. 30; laterally, Fig. 31); posterior margin markedly swollen distally and terminating in a pointed sclerotized apical tooth, bearing 2-3 stout orally directed setae; crista dorsalis (Figs 29-30) large tooth-like, smooth and located pre-apically close to megaseta; megaseta 20-22 µm long, 9 µm wide, conspicuous and slightly bent inwards.

Taxonomic position.

C. lencioniae sp. n. keys near C. gracilis , based on the shape of both tergite IX and the anal point ( Brundin 1956, fig. 87) and C. antipovae , based on the shape of the inferior volsella (Makarchenko and Makarchenko, Figs 3-4). However, the new species can easily be separated from other members of the Chaetocladius genus in having: tergite IX semi-circular; sternite IX typically circle-like in shape; anal point markedly pointed apically and bearing setae on proximal part; virga with 2 distinct long teeth; gonostylus spherical to bulbous; anterior margin ending with 3 characteristic pointed teeth (Figs 29-31), comb-like and placed close to megaseta area (clearly visible in both dorsal, ventral and lateral view); posterior margin markedly swollen distally and terminating in a pointed sclerotized apical tooth; crista dorsalis strong tooth shaped, smooth and placed pre-apically close to megaseta.

Etymology.

The new species is named lencioniae in honour of our colleague Dr. Valeria Lencioni from the Museum of Trento (Italy), who is active as curator ‘Conservatore’ and hydrobiologist in contributing to preserve the biological and ecological quality of water and environment in Trento and surrounding areas.

Ecology.

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

Geographical distribution.

C. lencioniae sp. n. is only known from its type locality. It can be considered as a typical biogeographic representative of high mountain rheocrenes and cold streams delimited by some Swiss Alpine glaciers.