Tanytarsus heliomesonyctios Langton, 1999

Stur, Elisabeth & Ekrem, Torbjørn, 2011, Exploring unknown life stages of Arctic Tanytarsini (Diptera: Chironomidae) with DNA barcoding, Zootaxa 2743, pp. 27-39 : 32-33

Tanytarsus heliomesonyctios Langton, 1999

Material examined: 1 larva, Norway, Svalbard, Nordenskioldland, Kapp Linné, Søndre Borgdam, N78.07055° E13.79345°, 35m, 08.viii.2008, K. Hårsaker, G. Velle.

Diagnostic characters. Tanytarsus heliomesonyctios can be separated from other known Tanytarsus larvae by having the three median teeth on mentum offset and more ventral to rest of mentum; premento-pharyngeal complex normally developed and not heavily sclerotized; mandible with one accessory dorsal teeth and a well developed accessory dorsal plate.

Description (n = 1). Head capsule ( Fig. 7 ) light yellowish-brown with darker posterior margins, mandibular teeth and mentum. Total length c. 4.2 mm.

Head capsule length c. 225 µm, width c. 200 µm; AR1.71; AHR 0.34; AAR 1.0; antennal pedestal 76 µm long without spur ( Fig. 27 ); antenna with segments 1–2 well sclerotized, segments 3–5 hyaline, antennal seta placed at about 1/2 length of antennal segment 1; lengths of antennal segments (in µm): 76; 24; 10; 6; 5; Lauterborn organs small, on 35 µm long pedicels, slightly longer than apex of antenna ( Fig. 27 ); LOR 1.70. SII pectinate; chaetae plumose, pectinate; chaetulae simple; S3 simple. Pecten epipharyngis consisting of three serrate scales; premandible with 4 narrow teeth, brush well developed ( Fig. 28 ). Mentum ( Figs 29–31 ) about 59 µm wide, median tooth without notches closely set with first lateral teeth, together with these offset ventrally to rest of mentum; median tooth about same colour as first lateral teeth, slightly paler than remaining teeth; ventromental plates 75 µm wide, slightly more curved laterally, with obvious striation along whole length; MVR c. 0.79. Mandible ( Figs 31–32 ) with 3 inner teeth, one apical tooth, two dorsal teeth and one robust dorsal plate; pecten mandibularis slightly convex; postoccipital plate moderately developed, rounded.

Body. Anterior parapods with long, simple spines; second lateral seta of abdominal segments not visible; posterior parapods with about 14 simple hooks in single row ( Fig. 12 ); anal segment with 4 anal tubules, c. 75 µm long; procercus with one short and one long dorsal seta, with 3 short (c. 125 µm) and 5 long (c. 400 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 27 – 32. Tanytarsus heliomesonyctios. 28: premandible, 29 – 30: mentum, 31: mouthparts ventral view, 32: mandible.