Thalassosmittia christinae, Saether, Ole A. & Andersen, Trond, 2011

Saether, Ole A. & Andersen, Trond, 2011, Chironomidae from Gough, Nightingale and Tristan da Cunha islands, Zootaxa 2915, pp. 1-19 : 10-13

Thalassosmittia christinae sp. n.

( Figs 17–22 )

Type material. Holotype female, GOUGH ISLAND: Site SG1 at Snoek Gat, 40o20'439"S, 0 9o 52'927"W, supralittoral, 5 m a.s.l., 2000, Malaise trap, C. Hänel & A.G. Jones ( ZMBN). Paratypes: 3 females, as holotype; as holotype except: 4 females, SB1 at Seal Beach, 40o20'667"S, 0 9o 53'199"W; 2 females, SB4 at Seal Beach penguin colony, 40o20'711"S, 0 9o 53'232"W, tussock-grassland, 25 m a.s.l.; 2 females, SG2b at Snoek Gat in upper region, 40o320' 437"S, 0 9o 52'943"W; 11 females, SB3 at Seal Beach, 40o20'659"S, 0 9o 53'215"W, tussock-fernbush, 50 m a.s.l.; 1 female, AD1 at Admirals, 40o20'293"S, 0 9o 53'008"W; 3 females, BA1 at Base (weather station), 40o20'516"S, 0 9o 53'028"W, fernbush, 50–100 m a.s.l.; 4 females, BR1 at the bridge over the stream (behind the weather station), 40o20'407"S, 0 9o 53'228"W; 3 females, FS1 at ‘First Stop’ by the stream (along transect from the weather station towards Tafelkop), 40o20'227"S, 0 9o 53'367"W; 5 females, PC1 at Prion Cave, 40o20'724"S, 0 9o 53'354"W; 2 females, WA1 on the west side of Admirals, 40o20'380"S, 0 9o 53'980"W; 2 females, TK1 at Tafelkop in the presence of a stream and some tussock grasses, 40o19'960"S, 0 9o 53'806"W, fernbush, 350–400 m a.s.l.; 2 females, GD 1 in Gonydale with stream and peat bog present, 40o19' 933"S, 0 9o 55'311"W, wet heath, 450–500 m a.s.l.; 3 females, WC1 at Waterfall Camp, by the waterfall, 40o18' 356"S, 0 9o 56'542"W, wet heath, 650–700 m a.s.l. ( BMNH, TDC, ZMBN).

Etymology. Named in honor of Ms. Christine Hänel who collected some of the chironomid material and sent it to us for identification.

Diagnostic characters. The species differs from Thalassosmittia thalassophila (Bequaert et Goetghebuer, 1913) by having hairy eyes, antenna with subapical seta and 14–28 dorsocentrals.

Description. Female (n = 10). Total length 1.61–1.99, 1.79 mm. Wing length 1.06–1.34, 1.18 mm. Total length / wing length 1.45–1.63, 1.52. Wing length / length of profemur 3.29–3.69, 3.50.

Coloration. Nearly completely dark brown.

Head. AR 0.31–0.42, 0.38. Lengths (in µm) of flagellomeres: 60–75, 65; 41–56, 49; 45–56, 51; 45–54, 50; 68– 90, 81. Sensilla chaetica simple, conspicuous; 34–41, 37 µm long. Subapical seta present; 34–53, 40 µm long.

Temporal setae 5–8, 7 including 1–3, 2 weak inner verticals; 2–3, 2 outer verticals; and 1–3, 2 postorbitals. Clypeus with 8–12, 10 setae. Tentorium 94–135, 110 µm long; 8–17, 13 µm wide; tentorium of 3 specimens conspicuously more narrow, only 8–11 µm wide; 15–17 µm in remaining 7 specimens. Stipes 90–113, 99 µm long; 34–41, 37 µm wide at plate. Palpomere lengths (in µm): 23–26, 24; 34–45, 38; 60–86, 71; 56–79, 67; 75–56, 81. Third palpomere with 1 weak lanceolate sensillum clavatum; 15–19, 16 µm long. Coronal suture 34–68, 51 µm long.

Thorax. Median antepronotal lobes well developed, no lateral setae on antepronotum. Dorsocentrals 14–28, 20 uni- to biserial; acrostichals 3–5, 4, all anterior; prealars 6–9, 8; supraalar 1. Scutellum with 6–10, 8 setae.

Wing ( Fig. 17 ). VR 1.23–1.38, 1.29. Anal lobe weak. Costal extension 86–150, 118 µm long. R4+5 ending distal to apex of M3+4; Cu1 sinuate. Brachiolum with 1 seta; costal extension with 6–16, 11 non-marginal setae; R with 7– 11, 9 setae; R1 with 3–5, 4; R4+5 with 11–15, 13 setae; other veins bare. Squama bare.

Legs. Spur of fore tibia 30–34, 32 µm long; spurs of mid tibia 19–26, 21 µm and 15–23, 17 µm long; of hind tibia 38–45, 43 µm and 17–23, 20 µm long. Width at apex of fore tibia 30–34, 31 µm; of mid tibia 26–34, 31 µm; of hind tibia 38–41, 39 µm. Comb of 11–14, 12 setae; longest seta 30–38, 33 µm long; shortest 19–26, 22 µm long. Lengths and proportions of legs as in Table 4.

fe ti ta1 ta2

p1 313–387, 337 397–473, 428 184–226, 207 113–146, 121

p2 387–444, 412 397–501, 440 166–198, 179 90–113, 99

p3 387–482, 423 473–552, 494 236–288, 252 123–151, 133

ta3 ta4 ta5 LR

p1 76–95, 84 47–57, 54 38–52, 45 0.46–0.50, 0.48

p2 66–85, 75 43–57, 47 38–47, 46 0.40–0.42, 0.41

p3 104–146, 119 38–61, 51 38–52, 44 0.50–0.54, 0.52

BV SV BR

p1 3.58–3.85, 3.65 3.58–3.85, 3.65 2.2–2.9, 2.5

p2 3.78–4.02, 3.93 4.59–4.86, 4.78 2.0–2.7, 2.4

p3 3.16–3.57, 3.32 3.32–3.68, 3.57 2.8–4.0, 3.2 Abdomen. Number of setae on tergites I–VIII as: 4–16, 10; 17–30, 24; 17–32, 26; 14–32, 24; 17–34, 26; 14–32, 24; 18–30, 24; 12–21, 17. Number of setae on sternites I–VIII as: 0; 0–4, 0; 0–9, 3; 3–9, 5; 6–13, 9; 8–15, 11; 10– 15, 11; 7–17, 11.

Genitalia ( Figs 18–22 ). Tergite IX undivided, large and curved making cerci and gonocoxites placed ventrally, tergite with altogether 11–15, 13 setae. Gonocoxite low, with 3–8, 6 strong setae and mostly a few strong microtrichia. Cercus 41–53, 49 µm long. Seminal capsule 90–113, 101 µm long; 56–75, 68 µm wide; microtrichia not observed; spermathecal ducts with long loop extending nearly to anterior apex of the large seminal capsules, apparently without bulbs before separate openings. Notum 90–113, 100 µm long.

Pupa and larva. Unknown.

Remarks. The presence of hairy eyes and of a subapical antennal seta would key this species out to Smittia Holmgren, 1869 rather than to Thalassosmittia Strenzke et Remmert, 1957 . However, in most other details the species conforms to the female of T. thalassophila (Bequaert et Goetghebuer, 1913) as redescribed by Strenzke & Remmert (1957). Especially the limitation of acrostichals to the anteriormost part of the scutum (dorsomedian setae as opposed to the more posterior acrostichals in the terminology of Strenzke) combined with how tergite IX covers the cerci in dorsal view. The large seminal capsule is more in accordance with that of Thalassosmittia as illustrated for instance by Saunders (1928 fig. 1I) for T. marina ( Saunders, 1928) than with the typical Smittia as illustrated in Fig. 12 . The genus Thalassosmittia includes species with hairy or pubescent eyes. However, no species is known to have a subapical seta on the antenna ( Saunders 1928; Strenzke & Remmert 1957; Sublette 1967; Cranston et al. 1989; Wang & Saether 1993). Because of this, the assignment of this parthenogenetic female to Thalassosmittia remains tentative until the immature stages are found.

Distribution and ecology. The species was caught from sea level up to 700 m altitude on Gough Island indicating that it not is restricted to the intertidal zone, but may also live in freshwater as does the Tibetan species T. montana Wang et Saether, 1993 . Sea spray gives the freshwater on these islands a relatively high salinity. Several species of Pseudosmittia Edwards, 1932 occurring in the marine intertidal zone also are semiterrestrial and semiaquatic.

Figures

FIGURES 17 – 22. Thalassosmittia christinae sp. n., female. 17 — wing; 18 — genitalia, ventral view; 19 — genitalia, dorsal view; 20 — ventrolateral lobe; 21 — dorsomesal lobe; 22 — apodeme lobe.

FIGURES 11 – 16. Smittia sp., female. 11 — wing; 12 — genitalia, ventral view; 13 — genitalia, dorsal view; 14 — ventrolateral lobe; 15 — dorsomesal lobe; 16 — apodeme lobe.