Palpomyia schmidti (Goetghebuer, 1934)

Szadziewski, Ryszard, Golovatyuk, Larisa V., Sontag, Elżbieta, Urbanek, Aleksandra & Zinchenko, Tatiana D., 2016, All stages of the Palaearctic predaceous midge Palpomyia schmidti Goetghebuer, 1934 (Diptera: Ceratopogonidae), Zootaxa 4137 (1), pp. 85-94 : 86-92

Palpomyia schmidti (Goetghebuer, 1934)

Palpomyia schmidti Goetghebuer, 1934a: 36 ( Iraq, female) (5 March 1934); Szadziewski et al. 2009: 195 ( Iraq, female redescribed, male diagnosed, figs, syn. P. miki ).

Palpomyia miki Goetghebuer, 1934b: 91 ( Hungary, female, fig. total habitus) (20 April 1934); Remm 1976: 175 ( Russia, female, male, figs); Delécolle et al. 1997: 342 ( Spain, female, figs).

Diagnosis. The only species in the genus with a triangular gonocoxite and totally separated parameres in the male genitalia, femora and tibiae armed with dark spine-like bristles. Females can be separated from other Palaearctic congeners in that they have simple claws, all femora armed with ventral spines, mid and hind tibiae with dorsal spine-like bristles, basitarsus of midleg with some median spines. Larvae: head relatively broad; collar of the head capsule with a triangular ventral expansion; a long epicranial suture (ES), reaching the level of seta q; a dorsal paired comb of the epipharynx with long, slender teeth. Pupae: dorsal apotome with 1 pair of setae and 1 pair of sensory pits (sensilla campaniformia); numerous spiracles arranged in a horseshoe shape, occupying the distal half of the respiratory horn.

Description. Female. Head yellowish. Eyes broadly separate, vertex with strong setae ( Fig. 2 A). Antennal flagellum 0.90 mm long, AR 0.84–0.86. Proximal flagellomeres subcylindrical, distal cylindrical ( Fig. 2 B). Palpus 5-segmented, third palpal segment stout, 0.11 mm long. Mandible with 7 stout teeth ( Fig. 2 A). Scutum yellowish with brown longitudinal stripes, scutellum yellow, postscutellum dark brown ( Fig. 2 C). Scutum without anterior tubercle, with numerous simple setae. Scutellum bearing 9–10 bristles and numerous small setae. Paratergite broad, bare. Anterior anepisternum with a group of 7–8 setae. Katepisternum dark and bare. Wing without pattern ( Fig. 2 D), length 2.10–2.90 mm, CR 0.71–0.78. Second radial cell about twice as long as first one. Base of vein M2 proximal to vein M1. Legs yellow with darker coxae and distal tarsomeres. Lateral surface of coxae with some setae. All femora armed with ventral spines ( Fig. 2 C). Fore femur enlarged with 6–18 ventral spines, mid femur slender with 1–4 spines and hind femur with 1–3 ventral spines. All tibiae armed with strong dark dorsal bristlelike spines. Fore tibia with 1 anterior spine, mid tibia with 4–10 spines and hind tibia with 12–16 dark spines. Tibial comb with 6–7 pale spines. First tarsal segment of foreleg armed with 2 apical spines, that of midleg with 2 basal, 5–6 median and 2 apical spines, hindleg with 5 dark spines, palisade setae in one row. Fourth tarsomere subcylindrical. Tarsal ratio of foreleg TR (I) 1.6–1.8, midleg TR (II) 1.9–2.2, hindleg TR (III) 1.8–2.0. Claws almost equal, simple, without internal basal tooth. Abdomen yellow with brownish triangles on tergites. Two pairs of apodemes of eversible sacs present. Seminal capsules ovoid, unequal, with distinct necks, length 0.08–0.11 mm, and 0.06–0.08 mm ( Fig. 2 E).

Male. Similar to female with the usual sexual differences. Eyes broadly separate. Flagellum 0.765 mm long, with greatly reduced plume, all flagellomeres cylindrical, terminal three slightly elongate ( Fig. 3 A). Proportions of flagellomeres as follows: 40-15-15-15-16-15-15-14-16-16-20-25-35. Third palpal segment stout, 0.037-0.045 mm long, with some sensilla capitata on surface.

Wing length 1.60–1.75 mm, CR 0.73–0.75. Tibial comb with 7–8 spines, hind tibial spur short. Tarsal ratio TR (I) 1.9, TR (II) 2.5–2.6, TR (III) 1.8–2.0.

Genitalia as in Fig. 3 . Sternite 9 with broad caudomedian excavation. Tergite 9 elongate, with broad cerci. Gonocoxite stout, as long as broad, with long triangular internal extension Fig. 3 C). Gonostylus stout, evenly bent, with pointed dark apical portion Fig. 3 D). Aedeagus stout, scutiform and covered with short spiculae; basal arch high; apex with evenly rounded cap ( Fig. 3 E). Parameres separate, apex distinctly expanded, bulbous ( Fig. 3 F).

Pupa. Body pale brown ( Fig. 4 ). Length: female 4.3–6.6 mm; male 4.9–5.5 mm. Respiratory horn ( Fig. 5 C) slender, about 3.8–4.1 times longer than broad, surface bare, distal half with about 40 spiracles in one horseshoelike row, length 0.40–0.46 mm in male, 0.460– 0.510 mm in female. Dorsal apotome (operculum) ( Fig. 5 B) 1.0–1.3 times as long as greatest width, covered with small tubercles, posterior margin pointed; anterolateral tubercle bearing single long seta and single sensory pit (campaniform sensillum). Antennae short, ventrally wings separated by legs ( Fig. 5 A). Caudomedian expansion of mesothorax indistinct, evenly rounded ( Fig. 4 B). Metathorax slender, distinctly emarginated, with single pair of sensilla campaniformia (M-3-T) ( Fig. 5 D). Abdominal segments with scattered small spinules. Tergites 1–7 with medial area displaying 1 longitudinal stripe and 2 darker spots ( Fig. 4 B). First abdominal tergite with 3 groups of setae on lateral surface ( Fig. 5 D); anterodorsal group including 2 setae and 1 sensory pit (campaniform sensillum), posterodorsal group with 2 setae and 1 sensory pit; lateral group composed of 3 setae. Dorsal surface of fourth abdominal segment with setae and sensory pits as in Fig. 5 E. Dorsal seta D-2 on rounded pale spot. Ventral surface only with two groups of 3 small setae (V-5,6,7). Abdominal segment 9 without setae, but with 2 dorsal sensilla campaniformia (D-5, 6) on apicolateral processus. Apicolateral processes of terminal abdominal segment 9 highly variable, long or short, covered with spinules or bare, slightly to greatly divergent ( Figs. 5 F,G). In females apicolateral processes ( Fig. 5 F) more divergent than in males ( Fig. 5 G).

Larva. IV instar ( Figs. 6 , 7 ). Body slender ( Fig. 6 A), total length to 11–12 mm. Head capsule pale brown, slightly conical, 1.925 as long as broad (HR), subgenal ratio (SGR) 1.951. Collar narrow, brownish; on ventral surface with distinct triangular extension ( Fig. 7 ). Epicranial suture moderately long, reaching level of seta q ( Fig. 7 A, C). Sensory pits (sensilla campaniformia) r, k, z, j indistinct. Setae s, u, o, x forked. Labrum slightly elongate, almost square with sensory organs typical of the subfamily; messors slightly sclerotized, hook-shaped. Mandible slender, hook-like, with double hook at midlength; fossa mandibularis distinct ( Fig. 6 G, H). Labium triangular with distinctly pointed apex ( Fig. 6 E). Hypostoma broad, slightly arched, smooth ( Fig. 6 E). Hypopharynx elongate, slightly sclerotized, hypopharyngeal fringe indistinct ( Fig. 6 E, F). Epipharynx with single, dorsal comb armed with 24–26 teeth on its posterior margin ( Fig. 6 H), 0.068–0.075 mm wide.

Neck or cervix distinct, about 7 times shorter than prothorax ( Fig. 6 B). Body segments moderately elongate, second thoracic segments 1.0–1.4 times longer than broad, abdominal segments about 1.5 times longer than broad. Anal segment slender, 3.3 times longer than broad; apex with group of 2 short outer and 2 long inner setae on dorsal and ventral surfaces ( Fig. 6 C, D); 2 dorsal and 2 ventral short caudal setae, in addition 2 lateral setae at level of shorter dorsal/ventral setae and 2 before mid-length of segment present ( Fig. 6 C).

Distribution and ecology. The species is halobiontic and represents the meridional faunal element in the Palaearctic Region ( Szadziewski 1985) or the Saharo-Arabian element ( Alwin-Kownacka et al. 2016). It was usually collected on rivers in steppes and deserts ( Remm 1976). It has been reported from Iraq ( Goetghebuer 1934a), Hungary ( Goetghebuer, 1934b), Spain ( Delécolle et al. 1997), Slovakia ( Tothova & Knoz 2006), Ukraine (Crimea), Russia (Rostov, southern Siberia), Azerbaijan, Tadjikistan, Kazakhstan, Iran, southern Siberia and Mongolia ( Remm 1976, 1988). We are unable to confirm Remm’s (1976, 1988) reports of the species from northern China.

Larvae of P. schmidti were observed in black and grey sandy mud, often with plant debris in the Rivers Chernavka, Solyanka, Lantsug, Khara and Bolshaya Samoroda, which flow into Lake Elton ( Figs 1 B, C). They were also observed among dense filamentous algae and Enteromorpha intestinalis . Larvae were collected at depths of 0.03–0.8 m, where the water was flowing at 0.01–0.4 m s -1. They live in riverine waters with salinities of 5.8– 31.7 g l -1, dissolved oxygen concentrations of 2.3–35.0 mg l -1 and pH levels of 6.5–9.4. These larvae were also found at the bottom of Lake Elton, where the salinity was 112.5 g l -1. In the Chernavka, larvae of P. schmidti occurred together with Cricotopus (Cricotopus) salinophilus Zinchenko, Makarchenko & Makarchenko, 2009 and Chironomus salinarius Kieffer, 1915 .

Under laboratory conditions, mature larvae pupated within 1–2 days. The pupal stage lasted 3 days. In the aquarium pupae floated on the water surface. Among the emerging adults, females were distinctly predominant over males, with a percentage ratio of 85: 15 in favour of the former. Larval and pupal mortality in the laboratory was less than 5%, a very low figure.

The abundance of 48 0 0 0 ind./m -2 recorded in the Chernavka (28 May 2015) is probably a maximum value for populations of larvae of this species in saline rivers. The average abundance and biomass were much higher in the highly saline Chernavka and Solyanka (17.17–31.7 g l -1) than in the less saline Khara, Lantsug and B. Samoroda (3.97–21.6 g l -1). The theoretical ecological salinity optimum for the halobiontic larvae of P. schmidti is 31.7 g l -1, with the tolerance interval varying from 20.76 to 33.14 g l -1 (unpublished data).

Figures

FIGURE 1. Breeding sites of Palpomyia schmidti. A—Map showing the geographical position of Lake Elton; B—The River Chernavka, which flows into Lake Elton; C—The bottom of the Chernavka covered with algae. On the map: Caspian Sea; River Volga.

FIGURE 2. Female of Palpomyia schmidti. A—frontal view of head; B—flagellum; C—lateral view of thorax; D—wing; Eventral view of abdomen.

FIGURE 3. Male of Palpomyia schmidti. A—flagellum; B – F—genitalia, ventral aspect: B—complete, only one gonostylus removed; C—gonocoxites, sternite and tergite 9; D—gonostyli; E—aedeagus; F—parameres.

FIGURE 4. Habitus of female pupa of Palpomyia schmidti. A—ventral aspect; B—dorsal aspect.

FIGURE 5. Pupa of Palpomyia schmidti. A—lateroventral aspect of female thorax; B—dorsal apotome; C—respiratory horn; D—chaetotaxy of metathorax and abdominal tergite 1; E—chaetotaxy of abdominal segment 4, dorsal view; F—female abdominal segment 9; G—male abdominal segment 9. Abbreviations: s. ca—campaniform sensillum, s. t—sensillum trichoideum. Names of other sensilla as proposed by Borkent (2014).

FIGURE 6. Larvae of Palpomyia schmidti. A—total habitus; B—head and prothoracic segment; C—anal segment, dorsal view; D—apex of anal segment, dorsal view; E—pharyngeal apparatus, ventral view; F—pharyngeal apparatus, ventral view; G—mandible; H—drawing of mandible; dorsal comb of epipharynx. Abbreviations: epi—epipharynx. hy—hypostoma, hyphypopharynx, lb—labium, i—inner seta, o—outer seta.

FIGURE 7. Head capsule of larvae of Palpomyia schmidti. A—dorsal view; B—ventral view; C—lateral view. Abbreviations: ant—antenna; CO—collar; DA—dorsal apotome; frontoclypeus; hy—hypostoma; md—mandible; j, k, m, n, r, z—sensory pits, sensilla campaniformia; o, p, q, s, t, u, v, w, x—setae, sensilla trichoidea.