Micropsectra insignilobus Kieffer, 1924

Stur, Elisabeth & Ekrem, Torbjørn, 2011, Exploring unknown life stages of Arctic Tanytarsini (Diptera: Chironomidae) with DNA barcoding, Zootaxa 2743, pp. 27-39 : 30-32

Micropsectra insignilobus Kieffer, 1924

Material examined: 7 larvae, Norway, Svalbard, Nordenskioldland, Kapp Linné, Søndre Borgdam, N78.07055° E13.79345°, 35m, 08.viii.2008, K. Hårsaker, G. Velle & T. Ekrem.

Diagnostic characters. Micropsectra insignilobus can be separated from other described Micropsectra larvae by having a moderately long antennal pedestal (c. 120 µm) including a minute spur (8 µm); antennal segment 2 about 1/3 length of segment 1; labral seta SII simple; posterior parapod with about 90–100 claws in 2–3 rows.

Description (n = 7). Head capsule ( Fig. 10 ) light yellowish-brown with dark brown posterior margins and mandibular teeth; mentum brown. Live individuals light red. Total length c. 9 mm.

Head capsule length c. 400 µm, width c. 360 µm; AR 2.0–2.2, 2.1; AHR 0.27–0.36, 0.31; AAR 0.52–0.72, 0.62; antennal pedestal 108–143, 127 µm long with 8 µm long triangular spur ( Fig. 17 ); antenna with segments 1– 2 well sclerotized, segments 3–5 pigmented, antennal seta placed at about 2/3 length of antennal segment 1 ( Fig. 18 ); lengths of antennal segments (in µm): 190–211, 203; 70–75, 73; 8–10, 9; 8; 6; Lauterborn organs small, on 125–135, 130 µm long pedicels; LOR 5.0–6.0, 5.6; SII simple; chaetae plumose, pectinate; chaetulae simple; S3 simple. Pecten epipharyngis consisting of three scales with tapered, sharp teeth ( Fig. 19 ); premandible with 2 robust teeth, inner tooth broader, brush well developed. Mentum ( Fig. 20 ) about 135 µm wide, median tooth with obvious notches laterally, about equally strong in colour as lateral teeth; ventromental plates 145 µm wide, evenly curved, with obvious striation along whole length; MVR c. 0.93. Mandible ( Fig. 21 ) with 3 inner teeth, one apical tooth, one dorsal tooth; pecten mandibularis slightly convex; postoccipital arch narrow making the well developed, hyaline plate almost triangular in shape ( Fig. 10 ).

Body. Anterior parapods with long, simple spines; posterior parapods with 70–100 simple hooks in two–three rows ( Fig. 15 ); Second lateral seta of abdominal segments 2–7 fan-shaped with c. 20 branches; anal segment with 4 anal tubules, c. 175 µm long; procercus with one short and one long dorsal seta, with 4–5 short (c. 600 µm) and 3 long (c. 1000 µm) anal setae.

Figures

FIGURES 2 – 16. Tanytarsini of Svalbard, association of adult male hypopygia with larval head capsules and posterior parapods. Columns from left to right: Tanytarsus heliomesonyctios (2, 7, 12), Paratanytarsus austriacus (3, 8, 13), Micropsectra radialis (2, 9, 14), Micropsectra insignilobus (5, 10, 15) and Micropsectra logani (6, 11, 16). Scale bar for hypopygia = 300 µm, for head capsules and parapods = 100 µm.

FIGURES 17 – 26. Larvae. 17 – 21: Micropsectra insignilobus. 17: spur of antennal pedestal, 18: antenna, 19: pecten epipharyngis, 20: mentum, 21: mandible. 22 – 26: Micropsectra radialis. 22: antennal pedestal, 23 – 24: premandible, 25: mentum, 26: mandible.