Stempellinella edwardsi Spies and Saether

Ekrem, Torbjørn, 2007, A taxonomic revision of the genus Stempellinella (Diptera: Chironomidae), Journal of Natural History 41 (21 - 24), pp. 1367-1465 : 1405-1411

Stempellinella edwardsi Spies and Saether

Tanytarsus (Stempellina) minor Edwards 1929, p 420 . Lectotype „ ( BMNH 236372 ) England, Manchester, Levenshulme , 11 July 1929, H. Britton. Paralectotypes: 2 „„ ( BMNH 235923 , 235924 ) Wales, Newtown, 30 August 1893, G. Richardo [examined], 2 „, 1♀ ( BMNH) [not examined] . Lectotype here designated.

Tanytarsus (Stempellina) minusculus Edwards 1929, p 417 . Variant spelling of T. (S.) minor , preoccupied by Tanytarsus minusculus Kieffer, 1922 .

Stempellina minor (Edwards) . Goetghebuer (1937 –54) description, key.

Stempellinella minor (Edwards) . Brundin (1947, 1948); Langton (1991); Langton and Visser (2003); Klink and Moller Pillot (2003); Guo and Wang (2005) descriptions, keys.

Stempellinella edwardsi Spies and Saether 2004, p 65 . Replacement name due to junior homonymy with Tanytarsus curtimanus var. minor Kieffer in Thienemann and Kieffer, 1916 ( Spies and Saether 2004).

Additional material examined

Finland ( ZMUH): 2 „„ Lake Kuusijärvi, 21–27 May 1965, P. D. Armitage; 4 „„, 6 Pex as previous except 4 June 1966; 1 P „, 4 „„ Lake Puruvesi, 14–15 July 1962, 25–28 August 1961, B. Lindeberg; 1 „, Punkasalmi, Akonniemi, Kortteenoja, 5 June 1973, B. Lindeberg; 2 „„ Lake Inari, Tsuolisjärvi, 17 July 1971, P. Virtanen. Germany: 1 Pex ( JES) Ost-Holstein, Selenter See, 4 June 1968, F. Reiss; 1 „ ( ZSM) as previous; 2 „„ ( ZSM) Ost-Holstein, Unterer Schierenseebach, 15 August 1984, 22 August 1984, U. Holm; 1 „, 1 P „, 6 Pex ( ZSM) Bavaria, Roding, Kammerweiher, 23 April 1998, 11 May 1998, W. Schacht; 1 „ (VM) as previous except 14 May 2005, E. Stur and T. Ekrem; Pex (2 ZSM) Bavaria, München, Feldmochinger See, 4 May 1991, S. Michiels; 2 Pex (1 SM, 1 VM) as previous except 7 October 1990; 2 Pex ( SM) Bavaria, Burghausen, Wöhrsee, 1 May 1996, S. Michiels; 1 Pex ( ZSM) Bavaria, Tegernsee, St. Quirin, 31 May 1990, N. Reiff; 1 LP ♀ ( ZSM) Bavaria, München, Nymphenburger Park, Kleiner See, 7 August 1998, W. Schacht; 1 Pex ( ZSM) Bavaria, Grosser Ostersee, 16 May 1980, F. Reiss; 1 Pex ( ZSM) Bavaria, Chiemsee, Alzausfluss, 8 September 1987, N. Reiff; 2 Pex ( ZSM) Bavaria, Rosenheim, Pelhamer See, 18 May 1990, N. Reiff; 1 P „ ( ZSM) Fürstenfeldbrück, Puchheim, Baggersee, 11 May 1990, F. Reiss; 4 L ( ZSM) Bavaria, lower Inn, 25 July 1978, 14 August 1978, 12 September 1978, F. Kohmann. Mongolia ( ZSM): 1 „ Lake Char-Nur, 5 June 1975, Piechocki; 1 „ Acit-nur, 27 July 1977, M. Stubbe. The Netherlands (VM): 1 Pex, Limbourg Prov. Maasplassen, Mook, 51 ° 559270N, 51 ° 439560E, 25 July 1995, R. Geene. Norway (VM): 1 „ Oppland, Øystre Sildre, Øvre Heimdalsvatn, 28 July 1972, K. Aagaard. Scotland ( PHL): 1 P „ Glenfalterach, 29 July 1984, P. H. Langton. Sweden ( ZMUH): 5 „„ Jämtland, Strömsund, Ankarvattnet, 15 August 1957, Grimis. Switzerland ( JES): 1 „, Vierwaldstätter See, 6 August 1965, F. Reiss. USA: 1 „ ( JES) AK, Lake Nerka, 12 August 1974; 1 „ ( ZSM) 16 miles W, 1 mile S Buffalo, 44 ° 209N, 107 ° 059W, 6 August 1969, D. Hansen; 1 „, 1 L ( PLH) MI, Mackinac Co., Lake Michigan, Sta. 490, 1997, D. Schoellser; 1 „ ( PLH) OH, Clermont Co., East fork Little Miami R, Proctor & Gamble Experimental Channels, 15 September 1998, P. L. Hudson; 1 L ( PLH) WI, Bayfield Co., Lake Superior off Stockton Island, 15 m depth, 21 July 1973, J. Selgeby.

Diagnostic characters

Stempellinella edwardsi can be separated from other Stempellinella species by the following combination of characters: adult male with wing length ca 1.2 mm; AR about 1.1; frontal tubercles large, conical; T-shaped anal tergite band; anal point with numerous (26–50) small spinulae at base; small median tergite setae close to anal point; median volsella without microtrichiae, with fan of simple lamellae. Adult female with AR 0.40; two or three setae on large vaginal floor; spermathecal ducts longer than notum; rami longer than notum. Pupa with well-developed, tubular cephalic tubercles; thoracic horn long and thick with numerous small chaetae; median antepronotal long, taeniate, situated on tubercle; thorax with large field of fine granulation anteriorly. Larva with moderate (ca 22 Mm long), digitiform spur on antennal pedestal; AR 0.77–0.83; S3 simple; premandible with three teeth; both Lauterborn organs on short pedicels.

Redescription

Adult male (n 5 5, unless otherwise stated). Total length 1.6–1.7, 1.65 (n 53) mm; wing length 1.10–1.36, 1.20 mm.

Colour: pale brown with dark brown scutal stripes, postnotum, preepisternum, median anepisternum, and antennal pedicels, eyes uniformly dark brown.

Head ( Figure 13A, B ): eyes without dorsomedian elongation; frontal tubercle large, conical, 18 Mm long; antenna with 13 flagellomeres of which only 10 are easily discernible; AR (on 10 flagellomeres) 1.06–1.27, 1.16; lengths of palpomeres (in Mm): 19–25, 23; 24– 34, 29; 72–91, 82; 83–101, 92; 90–119, 109. Clypeus about 55 Mm long with 10–11 setae; tentorium ca 95 Mm long, 16 Mm wide; one or two inner verticals, two outer verticals, two or three postorbitals.

Thorax: scutal tubercle absent; acrostichals 10–11; dorsocentrals 7–8; humerals absent; prealars 1; scutellars 5–7; halterals 5.

Wing ( Figure 13C ): cuneiform, 3.5 times longer than broad; VR 1.42–1.50, 1.47; wing setation as in Figure 13C .

Legs ( Figure 13D ): fore tibia with 11–19, 16 Mm long spur; mid and hind tibiae with well-separated, 7–11, 10 Mm long tibial combs, mid tibial combs with 18–30, 21 Mm and 10–17, 14 Mm long spurs, hind tibial combs both with 18–19 Mm long spurs; mid tarsus 1 with none or one sensilla chaetica; pulvilli absent. Lengths and ratios of leg segments in Table III.

Hypopygium ( Figure 13E–G ): anal tergite 96–111, 101 Mm long with transverse, Tshaped anal tergite band; two to five, four short median setae at anal point base, one lateral seta, 16–20, 19 apical setae; anal point ( Figure 13F ) 34–39, 36 Mm long, basally 15 Mm broad with variably developed crests, distally thin and pointed; 26–50, 42 small spinulae at anal point base; microtrichia present at base of anal point, but small microtrichia-free areas present on each side of anal point base. Gonocoxite 94–108, 101 Mm long; gonostylus 61– 72, 67 Mm long; HR 1.46–1.64, 1.52. Setiger of superior volsella oval with apical lip, posteromedially directed, with three or four dorsal and three median setae, anteromedian seta on low tubercle, superior volsella otherwise bare; digitus absent; median volsella ca 30 Mm long, strongly curved posteriorly, stem simple, bare, with fan of simple 35 Mm long lamellae ( Figure 13G ); inferior volsella ca 70 Mm long, strongly club-shaped, with several distal setae, dorsal surface without microtrichia.

Adult female (n 5 1). Total length 1.7 mm; wing length not measurable.

Colour: as male.

Head: as male, except cephalic tubercles ca 6 Mm long; antenna ( Figure 13H ) with five flagellomeres, ultimate flagellomere 63 Mm long, AR 0.40; palpomeres not measurable. Clypeus with 13 setae.

Thorax: acrostichals 13; dorsocentrals 6; humerals 3; prealars 1; scutellars 6; halterals not visible.

Wing: not measurable.

Legs: as male.

Genitalia ( Figure 13I ): tergite IX slightly triangular, about 45 Mm long; sternite VIII with 18 setae, of which two to four are placed on vaginal floor; vaginal floor large, covering one- half of vaginal opening ventrally; gonapophysis VIII single lobe with long posteromedially directed microtrichia; gonocoxite IX with one seta; gonocoxapodeme slightly curved; coxosternapodeme well developed with obvious anterior and posterior lobes. Notum including rami 129 Mm long, notum alone ca 60 Mm long. Seminal capsules ovoid, diameter 48 Mm with 165 Mm long spermathecal ducts. Postgenital plate triangular. Cercus 39 Mm long.

Pupa (n 5 5, unless otherwise stated). Total length 2.3–2.7, 2.5 mm; abdomen 1.8–2.0, 1.9 mm long. Colour of pupal exuviae pale brown with somewhat darker lateral margins on abdomen, transverse brown pigmented posteriorly on segment VIII.

Cephalothorax ( Figure 14A, B ): cephalic tubercle ( Figure 14A ) well developed, narrow, tubular, 39–51, 46 Mm long; frontal setae taeniate, 175–240, 193 Mm long; pedicel sheath tubercle absent. Thoracic horn 360–510, 460 Mm long, 33–45, 40 Mm wide with numerous 6 Mm long chaetae scattered on distal three-quarters; precorneals taeniate, 150–280, 240 Mm long, arranged in a row on small tubercles; median antepronotal taeniate on obvious tubercle, ca 230 Mm long, two lateral antepronotals: one taeniate, ca 230 Mm long, one sensillum basiconicum; two pairs of fine dorsocentrals, Dc 1 about twice as long as rest. Large area of fine granulation anteriorly on thorax ( Figure 14B ), a few stronger granules present along median suture line. Prealar tubercle well developed, wide; nose of wing sheath strong.

Abdomen ( Figure 14C ): TII with minute, semicircular posteromedian point patch; hook row 125–180, 150 Mm wide with 39–56, 48 hooks. TIII – VI with parallel point patches which are partly or completely transversely divided in middle; TVI –IX with anterolateral patches of shagreen. Segment II with pedes spurii B; segment IV with pedes spurii A. Segment II with 2 D, 2 V, 3 L setae; segment III with 3 D, 2 V, 2 L, 1 taeniate L setae; segment IV with 3 D, 3 V, 2 L, 1 taeniate L setae; segment V with 3 D, 3 V, 3 taeniate L setae; segment VI – VII with 3 D, 3 V, 4 taeniate L setae, segment VIII with 1 D, 1 semitaeniate V, 4 taeniate L setae; segment IX with 1 D seta on anal lobe, 20–26, 23 taeniate setae in anal fringe. One pair of O-setae present anteriorly on tergites II – VII and anterolaterally on sternites II – VII. Pleurae without shagreen. Posterolateral spur on segment VIII well developed.

Larva (n 5 5, unless otherwise stated). Total length ca 2.5 mm, case ca 3 mm. Head capsule brown, somewhat darker postoccipital rim and teeth on mandible and mentum. Live individuals with light yellow and green body.

Head ( Figure 14D, H ): AR 0.77–0.83, 0.82; antennal pedestal 45–51, 49 Mm long with well-developed, 15–30, 22 Mm digitiform spur; antenna ( Figure 14D ) with all segments well sclerotized, segment lengths (in Mm): 48–60, 54; 36–48, 43; 9–12, 11; 8–9; 3–4; segment 3 inserted subapically on segment 2; AAR 0.75–1.00, 0.89. Antennal seta placed at base just above ring organ; antennal blade ca 40 Mm long, pale, variably long, reaching from slightly beyond tip of antennal segment 2 to slightly beyond distal Lauterborn organ; peg of antennal segment 2 placed subapically on segment. Lauterborn organs large, bulbous, 15 Mm long; proximal organ placed close to base of segment 2 on 5 Mm long pedicel, apical organ on 7 Mm long pedicel; SII slightly pectinate, chaetae and chaetulae simple; S3 simple; pecten epipharyngis consist of three well-developed chaetae; labral lamella with ca 20 teeth. Mentum ( Figure 14E ) with 13 teeth, median tooth without lateral notches, somewhat paler, first lateral teeth set close to median tooth; ventromental plate medially barely reaching first lateral tooth of mentum, MVR ca 1.1; premandible ( Figure 14F ) with three teeth, well-developed brush; mandible ( Figure 14G ) with pecten mandibularis slightly convex, seta subdentalis 69 Mm long; postoccipital plate ( Figure 14H ) well developed, not split.

Body: anterior parapods with long, simple spines; hind parapods with 14 simple hooks; L2 apparently simple; anal segment with four narrow anal tubules; supraanal seta strong, ca 225 Mm long; procercus ca 30 Mm long with two short (ca 150 Mm long) and four long (ca 550 Mm long) anal setae, the short setae situated individually, and not on the common base of the long setae.

Remarks

Lectotype designation here to promote future nomenclatural stability.

The larvae of Stempellinella edwardsi , early instars in particular, can be difficult or impossible to separate from those of S. leptocelloides , and the characters used in the key below overlapped in material of S. edwardsi and S. leptocelloides from Canada and Norway examined by G. A. Halvorsen (personal communication).

Stempellinella edwardsi is a common species in clean lakes, dams, and slow-flowing parts of rivers and streams in Europe. The species has been recorded also in the East Palaearctic and Nearctic regions ( Makarchenko et al. 2005; Saether and Spies 2004; above). The larvae and pupae of S. edwardsi live in sand and silt where they build their small houses of fine sand and silt particles. Typically the building material is much finer that that used by the other European members of this genus.

Figures

Figure 13. Stempellinella edwardsi Spies and Saether, imagines. (A–G) Male: (A) head; (B) antennal flagellum; (C) wing; (D) fore, mid, and hind tibiae; (E) hypopygium; (F) anal point variation; (G) superior and median volsellae. (H, I) Female: (H) antennal flagellum; (I) genitalia.

Figure 14. Stempellinella edwardsi Spies and Saether, immatures. (A–C) Pupa: (A) frontal apotome; (B) thorax; (C) abdomen, dorsal view. (D–H) Larva: (D) antenna; (E) mentum and ventromental plates; (F) premandible; (G) mandible; (H) postoccipital plate.