Diamesa longipes Goetghebuer

Lods-Crozet, Brigitte, Semenchenko, Alexander A. & Makarchenko, Eugenyi A., 2025, Morphological redescription and DNA barcoding of Diamesa longipes Goetghebuer, 1941 (Diptera: Chironomidae: Diamesinae) from the Swiss Alps, Zootaxa 5723 (1), pp. 93-104 : 96-101

Diamesa longipes Goetghebuer

( Figs 4–10 , 16, 20, 24 )

Diamesa ( Brachydiamesa) longipes Goetghebuer, 1941: 1 .

Diamesa longipes Goetghebuer ; Kownacka & Kownacki 1975: 39; Ashe & O’Connor 2009: 281; Montagna et al. 2016: 322 . [non] Diamesa longipes Tshernovskij, 1949: 105 (described by larva from Georgia).

Type material. Syntype: adult male, Ötztal Alps ( Tyrol), altitude 2400 m above sea level, 1940, leg. Heinz Janetschek. Deposited in Royal Belgian Institute of Natural Sciences, Brussels; N 18.073 ( Figs 1–3 ) .

Other material examined. 1 adult male, 2 pupal exuviae, Switzerland, canton of Valais, Matter Vispa catchment, Gornera stream, upstream of Zermatt village ( GOR 2 ), altitude 1625 m a.s.l., 23.X.2024, 46.010092 N 7.739994 E, leg R. Bernard ; 1 pupa ( GBIFCH01217113 ) and 1 pupal exuvia, Gornera stream ( GOR 1 ), 3 km upstream, altitude 2040 m a.s.l., 28.IX.2023 and 12.VIII.2024, 45.987456 N 7.733289 E, leg R. Bernard .

Description

Adult male (n = 1). Total length ca 2.2 mm. Total length/wing length 0.89.

Coloration. Dark brown to black. Head, thorax, and abdomen dark brown. Legs light brown to brown. Wings dark grey, with brownish veins.

Head ( Fig. 4 ). Eyes hairy, reniform. Temporal setae including 8 frontals and orbitals, 12 verticals, and 8–9 postorbitals. Clypeus with 8 setae. Antenna with 8 flagellomeres and reduced plume of setae ( Fig. 5 ); number and length of these setae on 1–7 flagellomeres respectively: 3 (20–24 μm), 2 (40 μm long), 2 (40–44 μm), 0, 2 (28–36 μm), 0, 0; terminal flagellomere with 5 setae, 72–88 μm long in basal part and with 1 subapical setae, 20 μm long. Length of 1–8 flagellomeres (μm): 84, 40, 40, 28, 28, 20, 16, 136; AR 0.53. Palpomere length (μm): 28, 64, 92, 84, 108. Palpomere 3 in distal part with sensilla capitata with diameter 20 μm. Head width/palpal length 1.09. Antennal length/palpal length 1.04.

Thorax. Antepronotum with 10 ventrolateral setae, 64 μm long. Dorsocentrals 11, 84–92 μm long; prealars 5, 72–84 μm long. Scutellum with ca 11 setae.

Wing ( Fig. 7 ). Length 2.4 mm, width 0.72 mm. Anal lobe slightly reduced and angular. Squama with 7 setae, 40–60 μm long. R and R 1 with 20 setae, R 4+5 with 3 setae (in distal part). RM /MCu 2.0–2.5.

Legs. Spur of front tibia 32 µm long. Spurs of mid tibia 28 µm long. Spurs of hind tibia 64 µm and 44 µm long. Hind tibial comb with 10 spines. Length (μm) and proportions of leg segments are as in Table 1.

Hypopygium ( Figs 6 , 16, 20, 24 ). Tergite IX densely covered with strong macrotrichia apices of which are directed anteriorly, with 5–6 setae, 12 µm long (laterally setae longer) and with narrow (8 µm), weakly chitinized and naked anal point, 108 µm long ( Fig. 6 ). Laterosternite IX with 5 setae, 12–16 µm long. Transverse sternapodeme ( TSA) regular triangular, 76 µm high, 128 µm wide at the base ( Fig. 20 ); TSA height/ TSA width 0.59. Aedeagal lobe 140 µm long; phallapodeme sclerotized, 80–84 µm long. Gonocoxite 296 µm long; inferior volsellae rounded, along margin with 4–5 setae, 16–28 µm long ( Fig. 24 ). Gonostylus 136 µm long, weakly curved, not expanded in distal half along the outer edge ( Fig. 16 ); in apical part with megaseta in form of wide terminal spine, 8 μm long and tooth the same size, next to it there is two setae approximately of the same length. HR 2.18.

Pupa (n=2), exuviae brownish. Total length ca 3.6 mm.

Cephalothorax. Frontal tubercles reduced, frontal apotome with 2 setae 200–232 μm long. Thorax slightly scaly in anterior part. Thoracic horn filiform, 168–224 µm long, brown at base, yellowish distally, approximately same width (12–14 µm) up to the middle, then gradually narrows and at top with some small teeth ( Fig. 8 ). Three brown or dark brown precorneal setae anterior to thoracic horn: Pc 1 76–84 μm, Pc 2 124–126 µm, Pc 3 40–48 µm. Antepronotum with 2 median setae and 1 lateral antepronotal.

Abdomen. Length 2.5–2.6 mm. Tergite I without shagreen or teeth. Tergites II–VIII with shagreen in anterior third or half. Sternites I–II without shagreen, sternites III–VIII with sparse shagreen and IX without shagreen. Tergite I and sternites I–III without posterior transverse row of spines. Tergites II—VIII with posterior transverse row spines, number of these spines on these tergites: 12–14, 10–12, 9–11, 9–13, 8–10, 7–9, 8–9 ( Figs 9–10 ). Number of posterior transverse row spines of sternites IV–VIII: 13–16, 11–12, 8–11, 9–11, 20–22 ( Figs 9–10 ). The total number of spines of the anal rows of tergites 54–65 and sternites 61–72. Segment I with 2 pairs of lateral setae, 50–56 μm long; segments III–VIII with 4 pairs of lateral setae, 60–76 μm long (L 1 –L 3) and 40–48 μm long (L 4). Segments II –VIII with spine-like process on posterolateral corners. Anal lobe with 3 yellowish anal macrosetae, 200–242 μm long, slightly curved in distal part and pointed. Male genital sac extended far beyond anal lobe ( Fig. 10 ).

Remarks. The adult male of D. longipes is closely related to three species in the subgroup – D. sakartvella sakartvella and D. sakartvella gidanica from Caucasus, D. zagrosica from Iran, and D. moubayedi from Lebanon. All of these species have a similar hypopygium structure, namely the shape of the gonostylus, TSA, and IVo, but the male of D. longipes has the lowest AR (0.49–0.53), smaller number of dorsocentral setae of the mesonotum (8–11), a short anal point on tergite IX (108 µm), shorter gonostylus length (136 µm), and higher ratio of the length of the gonostylus to its width is 3.1. By comparing the morphological characters of these species ( Table 2 and Figs. 11–15, 17–19, 21–23 ), as well as the results of DNA barcoding, we conclude that D. longipes is most closely related to D. zagrosica .

Of the species listed above, the pupa is described only for D. sakartvella (Kownacki & Kovnacka 1973) but this description is uninformative and does not allow a detailed comparison with D. longipes . However, the pupa of D. sakartvella is larger, its length is 5 mm, and there are 2 precorneal setae at the thoracic horn, whrease the length of the pupa of D. longipes is 2.2–3.0 mm and it has 3 precorneal setae.

Distribution and ecology. According to the data given in the catalogue of Ashe & O’Conner (2009), D. longipes is known from Austria, Italy, Moldova, and Switzerland. In our opinion, the distributional records of this species outside the Alps are unlikely. The indication of the species' location outside the Alps apparently is connected with the identification of D. longipes Tshernovskij described from a larva collected in a mountain stream near Bakuriani, Georgia ( Tshernovskij 1949). This species is a junior primary homonym of D. longipes Goetghebuer. D. longipes Tshernovskij was included in his key to chironomid larvae ( Tshernovskij 1949) and later it was included in a key to larvae by Pankratova (1970). Both books were then widely used for identifying chironomid larvae in faunistic and ecological studies, especially in the former Soviet Union and Eastern Europe. Hence, all identifications of larvae as “ D. longipes ” should be referred to D. longipes Tshernovskij nec Goetghebuer.

The location of D. longipes is also indicated for Iran ( Namayandeh et al. 2021). However, the record is most likely to belong to D. zagrosica , which was discovered from the same region ( Makarchenko et al. 2022).

The chironomid community in the Gornera stream, the collection habitat, is almost entirely composed and dominated by the following Diamesa species: D. latitarsis (Goetghebuer) , D. wuelkeri Serra-Tosio , D. bohemani Goetghebuer , D. zernyi Edwards , D. cinerella Meigen , and D. tonsa (Haliday) . In the upstream site at 2040 m a.s.l. (GOR 1) ( Figs 27–29 ), the flow is naturally occurring (glacial hydrological regime) and the stream flows over serpentinite bedrock with most terrestrial vegetation typical of an alpine floodplain with larch ( Larix decidua ) and alpine grassland. During the time of sampling, the water was turbid, with conductivity of 293 µS/cm, a temperature of 2.2 °C, and flow rate of 0.75–1.50 m /s ( 23.X.2024), and. Environmental data of Gornera downstream sampling station at 1640 m a.s.l. (GOR 2) ( Fig. 30 ) are: section subjected to water fluctuations due to upstream water abstraction (hydroelectric installation), crystalline water, conductivity 216 µS/cm; temperature 5.8 °C, flow rate 0.25 – 0.75 m /s, and surrounding vegetation consisting of coniferous forest with mainly larch, birch ( Betula pendula ), and pine ( Picea abies ).

The adult male of D. longipes was collected from stones and boulders in Gornera downstream (GOR2) with a driftnet. However, it could come from upstream sites where the pupae were collected. As a result of extensive spatio-temporal sampling efforts over the past 30 years in Swiss Alpine streams ( Lods-Crozet et al. 2001; Alther et al. 2019; Robinson et al. 2024), D. longipes can now be considered rare and endemic to glacial rivers in the Alpine region. As indicated by Montagna et al. (2016), D. longipes is one of the rare species in the Alps and it is categorized as a cold-stenothermal species and threatened by global warming. The morphological and molecular study of the extended populations of the rare species, such that of D. longipes can greatly improve our understanding of their distribution and ecology, and efforts to conserve them.

Figures

FIGURES 4–10. Adult male (4–7) and pupa (8–10) of Diamesa longipes Goetghebuer. 4, head; 5, antenna; 6, hypopygium in dorsal view; 7, wing; 8, thoracic horn and precorneals; 9, tergite III; 10, tergites VII–VIII and anal segment. Scale bar: 50 μm.

FIGURES 11–26. Some details of hypopygium of Diamesa sakartvella sakartvella Kownacki et Kownacka (11, 17, 21), D. sakartvella gidanica Makarchenko, Semenchenko et Palatov (25–26), D. moubayedi Makarchenko et Semenchenko (12–13, 19, 22), D. zagrosica Makarchenko et Semenchenko (14–15, 18, 23) and D. longipes Goetghebuer (16, 20, 24). 11, 13–16, gonostylus; 12, apex of gonostylus; 17–20, transverse sternapodeme; 21–26, inferior volsellae. Scale bar: 50 μm. Figs 11–15, 17–19, 21–23 after Makarchenko et al. 2022, Figs 25–26 after Makarchenko et al. 2023.

FIGURES 1–3. Syntype of Diamesa longipes Goetghebuer, 1941. 1, label; 2, total view of adult male; 3, hypopygium in dorsal view (photos by Tim Laebens and Camille Locatelli).

FIGURES 27–30. Type localities of pupae (27–29) and adult male (3) of Diamesa longipes Goetghebuer. 27–29, site GOR 1 upstream; 30, site GOR 2 (photos by Régine Bernard.