Chironomus (Chironomus) entis Shobanov

Saether, Ole A., 2012, The Chironomus group (Diptera: Chironomidae) in Lake Winnipeg, Canada, Zootaxa 3275, pp. 1-19 : 9-10

Chironomus (Chironomus) entis Shobanov

( Figs 3 A–C, 6 A–E, 7, 9)

Chironomus (Chironomus) entis Shobanov, 1989a, 1989b: 341 .

Chironomus plumosus f. semireductus auct. pro parte

Chironomus muratensis Chang et al. 1993, 1994 , not Ryser, Sholl et Wülker.

Material examined. Lake Winnipeg light traps: Matheson Island Government Wharf, 5 males, 3 females, 5.vi. & 26.vii. 1969; 4 km off Grand Rapids, 22 males, 8.vi. 1969; Victoria Beach, 110 males, 9.vii. & 25.vii. 1969; Pine Dock, 9 males, 10.vii. 1969; 0.5 km off George Island, 131 males, 11.vii. & 12.vii. 1969; 3 km off Grand Rapids, 1755 males, 13.vii. & 4.ix. 1969; 10 km off (Sturgeonskin point) Long Point, 4471 males, 14.vii. 1969; 3 km off McCreary Island, 344 males, 15.vii. 1969; Gull Harbour, 28 males, 5 females, 16.vii. 1969; Gimli Government Wharf, 197 males, 24.vii. 1969; 3 km off George Island, 1578 males, 1 female, 27.vii. 1969; Grand Rapids Government Wharf, 728 males, 28.vii. & 5.ix. 1969; 5 km off Selkirk (Horse) Island, 487 males, 29.vii. 1969; McBeth Harbour, 202 males, 30.vii. & 7.ix. 1969; Pine Dock, 5 males, 31.vii. 1969; 15 km E off Long Point, 6 males, 6.ix. 1969; Beaver Point, 413 males, 18.vi. –27.viii. 1971; 20 Mile Creek, 2 males, 5.viii. 1971; Old Fishing Dock, 839 males, 9.vi. –5.viii. 1971; Calder's Dock, 373 males, 11.vi. –8.ix. 1971; Hecla Island, 12 males, 27.vii. & 11.viii. 1971. Emergence traps: Beaver Creek, 6 males, 22.vii. –11.viii. 1971. Rearing specimens: NNE of Reindeer Island, 4 males, 11.vi. 1969; NW Disbrowe Point, 1 male, 11.vii. 1969; Saskatchewan River Buoy, 1 male, 13.vii. 1969; East of Selkirk Island, 1male, 29.vii. 1969; West of Selkirk Island, 3 males, 29.vii. 1969; East McCreary Island, 3 males, 31.vii. 1969; Anama Bay, 1 male, 31.vii. 1969; 13 km SE Bigstone Point, 1 male, 1 female, 3.ix. 1969. South Basin, 55 larvae, 9.vii. –31.x. 1969; Narrows, 302 larvae, 1 pupa, 4.vi. –31.x. 1969; North Basin, 356 larvae, 8 pupae, 4.vi. –31.x. 1969.

Normal unparasitized males from Lake Winnipeg have an AR of 4.80–6.61, 5.46 (115); 30–55, 36 (10) sensilla chaetica on p2; 20–36, 24 (10) sensilla chaetica on p3; and fall completely within the redescription of C. plumosus (L.) by Strenzke (1959: 19). The females have 130–220, 178 (10) sensilla chaetica on p2; 140–252, 217 (10) sensilla chaetica on p3. Genitalia of normal male and female, gynandromorphs and intersexes are illustrated in Saether & Galloway (1980 figs. 5–6). The female genitalia are also illustrated in Saether (1977 fig. 81 D–E).

The immatures ( Figs 3 A–C, 6 A–E) are also typical C. plumosus except that the larva has blood-gills of semireductus type ( Lenz 1954 –62: 161; Shobanov 1989). Although the blood-gills overlap in length between C. entis and C. plumosus the head capsule measurements show that only one is species involved. The head capsule lengths of different instars is shown in Fig. 9 .

Distribution and ecology. C. entis in North America (as C. f. semireductus) is known from British Columbia and Manitoba, and from Washington, Colorado, North and South Dakota, Minnesota, Wisconsin and Indiana ( Saether 1970: 8, 1975: 3130; Saether & McLean 1972: 11; Wiederholm 1976: 27; Kiknadze et al. 2000: 859; Martin 2012). In the Palaearctic region C. entis is known from freshwater in Norway, Finland, Estonia, Chech Republic, Russia and Switzerland ( Kiknadze et al. 2000: 859, Saether & Spies 2011).

In Lake Winnipeg C. entis is the most common Chironomus species in the benthos of the narrows and the north basin ( Figs 1 , 7 ). Although many adult specimens were caught in the light traps from 1971 ( Fig. 5 ) even more were caught on the light traps set on the ship in 1969. There apparently are two generations a year.

Figures

FIGURE 1. Distribution of Chironomus spp. in the benthic samples of Lake Winnipeg.

FIGURE 3. Chironomus (Chironomus) spp, pupa. A, D: frontal apotome. B, E, G: tergites. C, F, H: anal spur. A – C: Chironomus (Chironomus) entis Shobanov. D – F: Chironomus (C.) bifurcatus Wülker, Martin, Kiknadze, Sublette et Michiels. G, H: Chironomus sp.

FIGURE 5. Chironomus (Chironomus) bifurcatus Wülker, Martin, Kiknadze, Sublette et Michiels. Numbers of adults caught in light traps and emergence traps in 1969 and 1971, and numbers of immatures in benthic samples from June to November 1969 and in March 1970. (LT = light traps, ET = emergence traps, short vertical lines = 1 – 25 specimens, second shortest lines = 26 – 50 specimens, medium long lines = 50 – 200 specimens; second longest vertical lines = 201 – 400 specimens, longest vertical lines = more than 400 specimens, 1 = first instar larvae, 2 = second instar larvae, 3 = third instar larvae, 4 = fourth instar larvae, P = pupae.)

FIGURE 7. Chironomus (Chironomus) entis Shobanov. Numbers of adults caught in light traps and emergence traps in 1969 and 1971, and numbers of immatures in benthic samples from June to November 1969 and in March 1970. (LT = light traps, ET = emergence traps, short vertical lines = 1 – 25 specimens, second shortest lines = 26 – 50 specimens, medium long lines = 50 – 200 specimens; second longest vertical lines = 201 – 400 specimens, longest vertical lines = more than 400 specimens, 1 = first instar larvae, 2 = second instar larvae, 3 = third instar larvae, 4 = fourth instar larvae, P = pupae.)

FIGURE 9. Head capsule lengths of different instars of Chironomus (Chironomus) entis Shobanov and Chironomus bifurcatus Wülker, Martin, Kiknadze, Sublette et Michiels in Lake Winnipeg.