Micropsectra schrankelae, Stur & Ekrem, 2006

Stur, Elisabeth & Ekrem, Torbjørn, 2006, A revision of West Palaearctic species of the Micropsectra atrofasciata species group (Diptera: Chironomidae), Zoological Journal of the Linnean Society 146 (4), pp. 165-225 : 206-208

MICROPSECTRA SCHRANKELAE SP. NOV.

Holotype LP£ ( ZSM), Germany, Bavaria, Berchtesgaden National Park , Herrenroint, spring no.312, 12°58′30E, 47°34′50 N, 15.V. 2001 –15.VI., 2001, E. Stur. 115 paratypes: 10££ & 1 LP(£) as holotype, except 6.vi.2001, 14.vi.2001 & 22.vi.2001; 1 P($) as holotype, except 10.vi.1996, R. Gerecke; 2££ as holotype, except 29.vi.1996, I. Schrankel; 2 P££, 1 P($) & 1£ ( ZSM), Germany, Hessen, Fulda, Wasserkuppe, 24.iv.1953, 28.iv.1953 & 20.v.1953, E. J. Fittkau; 2££ ( ZSM), Switzerland, Schwägalp, Säntis, 31.vii.1966, F. Reiss; 3££ ( ZMBN) Norway, Sogn og Fjordane, Aurland, Aurdalsvatnet, 813 m a.s.l., 21.vii.2001, T. Ekrem; 36££ ( MGDL), Luxembourg, Gutland, SW Kopstal, rheocrene, spring no. LUXqu25, emergence trap (E7), 1.vi.1999, 15.vi.1999, 29.vi.1999, 13.vii.1999 & 27.vii.1999, I. Schrankel; 9££ ( ZMBN) as previous except netted, 25.vi.2002, T. Ekrem; 48££ ( MGDL), Luxembourg, Diekirch, N Haerebierg, rheocrene spring at Schmittenhaff, no. LUXqu19, emergence trap (E1), 4.v.1999, 18.v.1999, 1.vi.1999, 15.vi.1999 & 29.vi.1999, I. Schrankel; 1£ ( ZMBN) as previous except netted, 27.vi.2002, T. Ekrem; 1 P(£) ( ZSM) Italy, Central Sardinia, Nuoro, Su Cologoni, 14.vii.1977, B. Rossaro.

Etymology

The species is named after our friend and colleague, Isabel Schrankel, who also collected the majority of the paratypes.

Diagnostic characters

Micropsectra schrankelae can be separated from other species in the atrofasciata group by the following combination of characters: adult male with frontal tubercles minute to absent; AR 0.5–0.7; small pulvilli; anal point well developed, broadly triangular, apically blunt, well developed knob between crests present; superior volsella with large field of microtrichia on stem, setiger large without ‘nose’, several long microtrichia in small field ventrally on setiger anterior to base of digitus, few wrinkles ventroapically on setiger; digitus thin, moderately long, sometimes reaching median margin of superior volsella; median volsella long, thin, broadest at base, reaching well beyond superior volsella, apically pointed. Pupa with cephalic tubercles low or moderately developed mounds; thoracic horn relatively short with comparatively long chaetae on at distal 3/4; prealar tubercle well developed, rounded; small dorsal field of granulation on mid thorax; large rectangular, dorsal, unpigmented area in middle of thorax; strong spines in patches on tergites III–V (in the longitudinal, lateral extensions on TIV–V); shagreen in patches on tergite VI; patches on tergite VI of smaller size than patches on tergites IV–V; microtrichia often present between spine patches on tergite III. Larva with small, pointed triangular spur on antennal pedestal; antennal pedestal c. 100 µm long; antennal segment 1 c. 160–180 µm long; seta SII and some chaetae pectinate; clypeal seta S3 simple; MVR about 0.85.

Description

Adult male. Measurements and ratios in Table 1.

Coloration: Body completely light greenish, with brown eyes.

Head. Antenna with 13 flagellomeres. Frontal tubercles present as minute dots or absent; temporal setae in one row; palpomere 3 with 4–5 sensilla clavata in row.

Wing. Subcosta and media bare, brachiolum with 2 setae, squama bare.

Legs. Pulvilli small, reaching base of claws. Fore tibia with small scale, small spur 10–20, 16 µm long; middle and hind tibial combs 18–20 µm long; middle tarsomere Ta 1 with 3 sensilla chaetica.

Hypopygium ( Fig. 17A, B ). Anal tergite with tergite bands separate, posteriorly directed, reaching crests of anal point; 6–8 median tergite setae placed on an elevated hump anterior to anal point base; 8–12, 10 ventral apical setae. Anal point broadly triangular, with high slightly curved anal crests, apex blunt; large knob between crests present; large microtrichia free area around base. Setiger of superior volsella large, roundish with 5–8, 7 dorsal and 2 median setae on setiger, 1 strong seta on stem; large field of dorsal microtrichia on stem and several long microtrichiae ventrally on setiger, anterior to base of digitus; few wrinkles ventroapically on setiger. Digitus thin, medium long, sometimes reaching median margin of superior volsella. Median volsella comparatively long, thin, pointed, broader at base, with medially directed setiform and spoon-shaped lamellae, spoon-shaped lamellae on distal 1/3; stem reaching well beyond superior volsella. Inferior volsella with small dorsoapical swelling, quite straight, bearing numerous distal setae. Inner margin of gonocoxite with 3–4 strong setae.

Pupa. Coloration: pupal exuviae brownish with dark brown apodemes; cephalothorax, TVIII and anal lobe darker; large, rectangular pigment-free area dorsally in middle of thorax. Measurements in Table 2.

Cephalothorax ( Fig. 17C, D ). Cephalic tubercle present, low to moderately developed mound; pedicel sheath tubercle weakly developed. Thoracic horn fairly short with numerous comparatively long chaetae on distal 3/4; precorneals arranged in triangular pattern, the 2 anteriormost setae situated closer to each other than to the third, median precorneal shorter than other two; 1 median antepronotal, 2 lateral antepronotals (1 sensillum basiconicum); 2 pairs of dorsocentrals, anterior pair shorter and weaker than posterior pair, setae of each pair equally strong. Some granulation present along median suture line and in small dorsal field on mid thorax. Prealar tubercle present, well developed mound; nose of wing sheath well developed.

Abdomen ( Fig. 17E, F ). TII almost covered by shagreen except for 2–3 lateral round patches and 1 posteromedian oval patch; pedes spurii B on TII obvious; hook row less than half as long as segment width. Spines of TIII in large, laterally curved patches in posterior half of tergite, shagreen extensively distributed lateral and anterior to spine patches, often a few points between patches. Patches of TIV consisting of spinules in anterior, oval patches with spines in longitudinal, lateral extensions which are slightly laterally curved posteriorly; few points present laterally to longitudinal patches. Patches of TV similar to those of TIV in shape and construction, somewhat shorter, patches not laterally curved posteriorly. Patches of TVI consisting only of shagreen, similar to patches on TV in shape, but often distinctly shorter. TVII with anterolateral patches of shagreen; TVIII with small anterolateral patches of shagreen (very reduced in specimens from Berchtesgaden). Segment I with 3 D and 1 V setae; segment II with 3 D, 4 V, 3 L; segment III with 5 D, 4 V, 2 L, 1 lateral semitaeniate seta; segment IV with 5 D, 4 V, 1 L, 2 lateral taeniae; segment V with 5 D, 4 V, 3 lateral taeniae; segment VI with 5 D, 4 V, 4 lateral taeniae; segment VII with 5 D, 4 V, 4 lateral taeniae; segment VIII with 1 dorsal taenia, 1 ventral taenia, 5 lateral taeniae; anal tergite with 1 dorsal taenia. Two pairs of small sensorial setae medially on TII–VII; 1 pair of O-setae present anteriorly on sternites II–VII. Anal lobe with evenly convex lateral margins, fringe with about 570 µm long taeniae in 1 row. Posterolateral comb of segment VIII ( Fig. 17G ) usually with 2–4 marginal teeth longer than rest.

Larva (n = 2). Head capsule well sclerotized and light brown. Live individuals were not available for examination. Total length not observable. Measurements and ratios in Table 3.

Head ( Fig. 17H–K ). Antennal pedestal with short, triangular, pointed spur; antenna with segment 1 well sclerotized, antennal seta placed at about 2/3 length of antennal segment 1; antennal segments 2–5 and Lauterborn organs missing on examined specimens; SII and inner chaetae pectinate; outer chaetae, chaetulae and S3 all simple; mentum with well developed lateral notches on somewhat pale median tooth; ventromental plates evenly curved with obvious striation along whole length; premandible with 2 robust teeth, inner tooth broader, well developed brush; mandible with pecten mandibularis slightly convex; seta subdentalis extending well beyond apical mandibular teeth; postoccipital plate well developed, subtriangular.

Body. Anterior prolegs with long, simple spines; hind prolegs with c. 40 simple hooks in two rows; L2 apparently simple; supraanal seta c. 110 µm long; procercus with one short and one long (c. 150 µm) dorsal seta, with 4 short and 3 long anal setae.

Remarks

Only two larvae, both without complete antennae, were available for examination.

Micropsectra schrankelae has been netted along the shores of the Aurdalsvatn, Norway (813 m a.s.l), and collected with emergence traps from cold-water springs in the German Alps (1100–1300 m a.s.l) and in Luxemburg (c. 300 m a.s.l). It is uncertain whether the specimens from Norway emerged from the lake or from one of the many nearby streams, but all waters in the area are oligotrophic and cold throughout the year at this elevation. Water temperature varied between 6 and 9 °C in the studied springs, and several of the latter clearly are influenced by limestone bedrock (e.g. Herrenroint, LUXqu25). Cytochrome c oxidase subunit II ( COII) has been sequenced from the German holotype as well as paratype specimens from Luxemburg and Norway; the composition of nucleotides is almost identical, with a minimum of 98.5% pairwise similarity for 539 base pairs .

Micropsectra schrankelae became the sister species to M. sofiae (described below) in the all the phylogenetic analyses we carried out, and their relationship was in most cases very well supported. The two species are found in similar habitats, but can relatively easily be separated by both morphology (see keys below) and COII gene sequences (maximum of 92.5% pairwise similarity for 539 base pairs).

Figures

Figure 17. Micropsectra schrankelae sp. nov. A, hypopygium. B, superior, median and inferior volsellae. C, pupal thorax. D, pupal frontal apotome. E, pupal abdominal segments II–VI, dorsal. F, pupal abdominal segments VIII–IX. G, variation in posterolateral comb of pupal segment VIII. H, larval antenna. I, larval premandible. J, postoccipital plate of larval head capsule. K, larval mentum, ventomental plates and setae submenti.