Simulium arminii, Seitz, Gunther & Adler, Peter H., 2017

Seitz, Gunther & Adler, Peter H., 2017, A new species in the Simulium vernum group from the Alps of southern Germany: Simulium arminii (Diptera: Simuliidae), Zootaxa 4226 (3), pp. 390-404 : 391-401

Simulium arminii new species

( Figs. 1–16 )

Simulium carthusiense: Seitz & Adler 2009 , not Grenier & Dorier [misidentification]

Holotype. Male with associated pupal exuviae and cocoon in ethanol; left hind leg and abdominal tip with genitalia parts in four microvials with glycerine, Germany, Höllental , near Garmisch-Partenkirchen, spring to Hammersbach, 47°26´09”N 11°01´23”E, orographically from the left (western) side, 1460 m elevation, collected 17 August, emerged 19 August 2014, leg. Gunther Seitz (deposited in the ZSM).

Paratypes. Data as in Table 1 : 1 female allotype with associated pupal exuviae and cocoon in ethanol (head, labellum, and abdominal tip in separate microvial with glycerine, left maxillary palp slide-mounted in Euparal; ZSM); 2 females with pupal exuviae, 5 pupae (in ethanol), 3 microscope slides with larval mandibles, labral fan rays, hypostoma, and postgenal cleft (in Euparal; ZSM); 1 male and 1 female with exuviae (in ethanol), 1 male larva and 14 female larvae (Carnoy’s fixative, transferred to ethanol after chromosome extraction; CUAC); 1 male and 2 females with pupal exuviae, 10 pupae (in ethanol; Collection G. Seitz).

Etymology. The species is named in honor of the first author’s son Armin (original Latin name = “Arminius”; genitive = “ Arminii ”) for companionship and collecting on the occasion of the discovery of the new species in the Sittersbach area.

Male. Body length 3.7 mm; wing length 3.7 mm. Scutum black; thoracic hair golden. Radius with hair dorsobasally. Stem vein and basicosta with long, golden hair. Mesepimeral tuft, basal fringe, and abdominal hair golden. Legs brown, base and tip of femora and tibiae darker; recumbent pilosity golden yellow in reflected light, shining. Hind leg with basitarsus 4.5 times longer than wide at widest point; calcipala less than ½ width of apex of basitarsus; pedisulcus distinctly developed ( Fig. 1 ). Male genitalia: Ventral surface of gonocoxite with long brown hairs, shorter dorsally. Gonostylus at base about ½ as wide as entire length, shorter than coxite, nearly parallel sided, distally with medially directed, subtriangular flange bearing 1 apical spinule ( Fig. 2 ). Ventral plate in terminal view with lip slightly protruded ( Fig. 3 ), in ventral view with body trapezoidal, posterolaterally rounded, anterior margin convex, posterior margin concave; lip with hairs originating from small cuticular nodules; basal arms slender, slightly shorter than length of body of ventral plate, and with apical ½ of each arm directed slightly inward ( Fig. 4 ). Parameres each with 1 strong spine; dorsal plate subquadrate with rounded corners beyond flangelike collar; median sclerite elongated, slender, apically bifurcated ( Fig. 5 ).

Female. Body length 3.4 mm; wing length 3.9 mm. Scutum, humeral angles, and scutellum brown; thoracic hair golden. Postnotum brown, without hair. Frons at narrowest width about 1/7 width of head; frons and clypeus with golden hair. Mandible with about 39 serrations (13 outer and 26 inner); lacinia with 21 (left) and 24 (right) retrorse teeth. Palpomere V about 1.9 times longer than palpomere IV and about 1.5 times longer than palpomere III. Sensory vesicle in lateral view elliptical, nearly ½ as long as palpomere III. Stem vein and basicosta with golden hair. Basal fringe and mesepimeral tuft golden. Precoxal bridge complete. Legs light brown, darker on tarsi and apices of femora and tibiae; hair on tarsi light brown, golden on other segments. Hind leg with basitarsus 7.5 times longer than wide at widest point; calcipala about ½ width of apex of basitarsus; pedisulcus distinctly developed. Claws each with basal, thumblike lobe. Terminalia: Cercus strongly haired on both sides. Anal lobe sclerotized at edges, medioventrally bulged, beset with hairs on both sides ( Fig. 6 ). Cercus in lateral view rectangular, broader than long, with upper corner more or less at right angle and lower corner rounded; anal lobe slightly extended ventrally, covered with strong hairs ( Fig. 7 ). Hypogynial valves almost transparent, each with few small hairs on basal half, otherwise unhaired ( Fig. 8 ). Genital fork ( Fig. 8 ) with stem long, well pigmented, 1.2 times longer than each comparatively long, straight arm. Arms distinctly divergent, extended posterolaterally beyond lateral plates, enclosing wide U-shaped space. Lateral plates each with dark brown cuticle and short, blunt, anteriorly directed apodeme ( Fig. 8 ). Spermatheca slightly longer than broad, longer than half length of stem of genital fork, with polygonal surface pattern; area surrounding junction with spermathecal duct unpigmented ( Fig. 8 ).

Pupa and cocoon. Body length (without gill) up to 4.5 mm. Gill of 4 closely spaced filaments directed anteriorly, longer than pupa if straight and fully extended; lower pair of filaments branched in vertical plane, upper pair of filaments branched inward in diagonal plane; filaments branching at acute angle from common basal trunk, which is up to 3.5 times longer than wide. Upper trunk up to ¼ thicker and 1.5–3.0 times longer than lower trunk; filaments with transverse furrows ( Fig. 9 ). Head plate and anterior thoracic dorsum densely covered with circular microtubercles (diameter up to 12.5 µm) bearing microgranules ( Fig.10 ); thoracic trichomes unbranched, dichotomous, or trichotomous, up to 250 µm long. Lower part of frontoclypeal shield with 1 short seta per side (often broken). Terminal spines small, pointed. Cocoon slipper shaped, décolleté, exposing much of thoracic area, overall weakly woven and transparent, covered with small chalk particles, with thickened rim, anteromedially with small, more or less protruding extension of woven strands, reduced in many cases ( Fig. 11 ).

Larva. Length of last instar up to 7.4 mm. Ground colour of body whitish yellow; dorsally with more or less distinctly pigmented brownish areas. Head yellowish brown, with washed-out positive, brown head spots; frontoclypeal apotome paler than postgenae; posteromedial head spot in form of isosceles triangle ( Fig. 12 ). Postgenal cleft longer than wide, about 200 µm long and up to 150 µm wide, rounded or slightly mitre shaped, extended about ½ distance to hypostomal groove ( Fig. 13 ); subesophageal ganglion unpigmented. Hypostoma with median tooth longer than 2 smaller lateral teeth that each arise from broadly rounded base; 3 small sublateral teeth per side ( Fig. 14 ). Paralateral teeth composed of 1 tooth on each side followed by 3 smaller saw teeth; 3–5 weakly expressed lateral serrations per side; 4 sublateral hypostomal setae, arranged one behind another per side, decreasing in length, with anteriormost seta about 100 µm long, trifid, deeply divided. Antenna longer than stem of labral fan, transparent, up to 0.55 (0.51) mm long, with articles 1 and 2 brownish; proportion of articles proximal to distal (excluding apical sensillum) 1.7:2.0:1.0 (1.5:2.1:1.0). Mandible with typically developed apical and preapical teeth, followed by 8 spinous comb teeth; inner preapical ridge of mandible with 1 sensillum and 3 serrations ( Fig. 15 ). Labral fan (n = 4) with 39–43 primary rays. Abdomen with conical ventral tubercle on each side of last segment. Anal sclerite X-shaped, with sclerotized areas alongside arms and between 2 halves; anterodorsal arms shorter than posterodorsal arms. Cuticle beside sclerite with numerous hairs, up to 40 µm long; no rectal scales. Rectal papillae with 3 compound lobes, each with 12–14 lobules. Posterior proleg with up to 12 hooks in each of 74–78 rows.

Polytene chromosomes. Chromosome arms IS and IIL had the standard banding sequence of Brockhouse (1985) for the Simulium vernum group, whereas IL-2, IIS-1, IIIS-4, and IIIP-1 ( Fig. 16 ) of Hunter (1987) were fixed ( Table 2 ). A chromocenter, ectopic pairing, and supernumerary (B) chromosomes were absent. The sex chromosomes, based on 14 females and only 1 male, were undifferentiated (X0Y0). Polymorphisms included IIIL- 19.1 (= q sequence of Hunter 1987), IIIL-2,(19'.1') (= w sequence of Hunter 1987), and three unique polymorphisms: IIIL-1ar, IIIL-2ar, and IIIL heteroband Hb-85B3 ( Table 2 ; Fig. 16 ). Section 41/42 was homozygously puffed in at least some nuclei in about half of the larvae. The difficulty of ascertaining whether IIIL- 19.1 and IIIL-19'.1' are the same or different (mimic) inversions persists ( Hunter 1987). Here, we recognize the ‘w’ sequence of Hunter (1987) without distinguishing IIIL-19.1 and IIIL-19'.1'. If the inversions are equivalent, then IIIL-19 and IIIL-1 are fixed in S. arminii n. sp. and IIIL-2 is floating (i.e., polymorphic).

Sittersbach Hammersbach a Italicized inversions indicate they are fixed.

b Polymorphism was on top of the w sequence.

c Novel polymorphism, known only in this species.

d Autosomal polymorphic inversions are named with a two-letter abbreviation of the species name (i.e., ‘ar’), following the practice of Hunter (1987).

Diagnosis and taxonomic remarks. Males of S. arminii n. sp. can be distinguished from those of other European members of the S. vernum group by the broad trapezoidal ventral plate with small cuticular nodules on the lip and short basal arms directed slightly inward. In comparison with other alpine species in the S. vernum group in Europe ( Rivosecchi 1978, fig. 68), the new species has the broadest ventral plate, except for that of Simulium dolomitense (Rivosecchi) . The length to width ratio of the hind basitarsus of the male, aside from that of Simulium bavaricum Seitz & Adler and Simulium vernum Macquart (sub S. (Cnetha) latipes ), also is greater than that of other alpine species of the S. vernum group illustrated (fig. 104) or measured by Rivosecchi (1978). For females, the upper rather right-angled corner and the lower roundly elongated corner of the cercus are striking, as are the long, straight arms of the genital fork. The pupa is characterized by the weakly woven cocoon with a poorly developed or absent anterodorsal projection, and the gill with the lower pair of filaments branched in the vertical plane and the upper pair of filaments branched obliquely inward. Larvae can be distinguished by the shape of the postgenal cleft and the hypostoma with its long median tooth and shorter lateral teeth arising from a rounded base on each side. The high number of primary fan rays in S. arminii n. sp. is not seen in other alpine species of the S. vernum group reported by Rivosecchi (1978). In comparison with other members of this group, the larva resembles that of S. beltukovae (Rubtsov) (formerly S. carpathicum (Knoz)) , based on the elongated median tooth of the hypostoma and the shape of the postgenal cleft. The pupa resembles that of Simulium carthusiense Grenier & Dorier , based on the microtubercles bearing microgranules.

Chromosomally, the new species is most similar to S. beltukovae , but differs most conspicuously by the absence of a chromocenter and a high frequency of the IIIL q sequence; three polymorphisms are novel. Simulium arminii n. sp. is a member of the Palearctic IIIP-1 subgroup of the S. vernum group, as defined by Adler et al. (2016).

Distribution and bionomics. Simulium arminii n. sp. is known from only two small rheocrenes (discharge 1– 2 l/sec) above the timber line, surrounded by steep meadows and rocks in the northern limestone Alps of southern Germany (cf. Seitz & Adler 2009, p. 9). In addition to our new species, the springs harboured Prosimulium latimucro (Enderlein) at both sites and S. bavaricum in the Sittersbach catchment area. Based on our current knowledge, these are the only species that colonize the hypocrenal sections of the northern limestone Alps up to 2000 m a.s.l. ( Seitz 2004, S. bavaricum sub nom. S. (N.) sp. 1). Like P. latimucro and S. bavaricum , the new species probably is univoltine, with larvae hatching chiefly in August. Although the feeding habits of the females are unknown, the fully toothed mouthparts and basal, thumblike lobe on each tarsal claw suggest ornithophily. With the discovery of S. arminii n. sp., 56 species of Simuliidae are now known from Germany ( Seitz et al. 2015).

Figures

FIGURE 1. Simulium arminii, male left hind basitarsus; inset with tarsomeres showing the pedisulcus (scale bars = 200 µm).

FIGURE 2. Simulium arminii, male gonocoxite and gonostylus; dorsal view (scale bar: 200 µm).

FIGURE 3. Simulium arminii, male ventral plate, left and right parameral spines, and dorsal plate with aedeagal membrane; terminal view (scale bar = 100 µm).

FIGURE 4. Simulium arminii, male ventral plate; ventral view (scale bar = 100 µm).

FIGURE 5. Simulium arminii, male dorsal plate with parameres; median sclerite in left inset (scale bar = 100 µm).

FIGURE 6. Simulium arminii, female terminalia; ventral view (scale bar = 100 µm).

FIGURE 7. Simulium arminii, female anal lobe and cercus; left diagonal lateral view (scale bar = 50 µm).

FIGURE 8. Simulium arminii, female genital fork, hypogynial valves, and spermatheca. Left: ventral view. Right: dorsal view (scale bar = 100 µm).

FIGURE 9. Simulium arminii. Left: pupal exuviae and cocoon showing short anterodorsal projection; anterior half in dorsal view (scale bar = 0.5 mm). Right: schematic depiction of branching pattern of pupal gill (viewed from anterior).

FIGURE 10. Simulium arminii, pupal microtubercles with microgranules; white specks represent chalk particles from habitat substratum (scale bar = 50 µm).

FIGURE 11. Simulium arminii, transparent cocoon of pupa, with weakly developed anterodorsal extension of thickened rim (scale bar = 1.0 mm).

FIGURE 12. Simulium arminii, larval head; dorsal view (scale bar = 100 µm).

FIGURE 13. Simulium arminii, larval head showing postgenal cleft; ventral view (scale bar = 100 µm).

FIGURE 14. Simulium arminii, larval hypostoma (scale bar = 10 µm).

FIGURE 15. Simulium arminii, apex of larval mandible, showing apical and preapical teeth, spinous comb teeth, sensillum and three serrations, and convex blade region (scale bar = 10 µm).

FIGURE 16. Chromosome arm IIIL of Simulium arminii; C = centromere. A. Basal half of arm, showing the heterozygous q / w sequence (sensu Hunter 1987); the outer breakpoints of the q and w sequences, as well as IIIP- 1, are shown by brackets. The heteroband Hb- 85 B 3 is shown in the homozygous enhanced condition (++). B, C. Basal three-quarters of arm, showing the IIIP- 1 and w sequence. Breakpoints of polymorphic inversions IIIL- 1 ar and IIIL- 2 ar are indicated by brackets. Small letters ‘ a’ through ‘ f’, when alphabetized, produce the standard sequence of Brockhouse (1985).

Tables

TABLE 2. Frequency of chromosomal rearrangements in larvae of Simulium arminii n. sp. from the German Alps.

	13 August 2007	15 August 2009	17 August 2014
No. of females: males	2:0	7:0	5:1
IL-2 a	1.00	1.00	1.00
IIS-1	1.00	1.00	1.00
IIIS-4	1.00	1.00	1.00
IIIL-19.1 (= q)	0.75	0.64	0.42
IIIL-2,(19'.1') (= w)	0.25	0.36	0.58
IIIL-1ar b,c d			0.17
IIIL-2ar b,c,d			0.08
IIIL Hb-85B3c		0.21	0.33
IIIP-1	1.00	1.00	1.00