Dannella daurica Tiunova 2023, sp. nov.

Dannella daurica sp. nov.

Figures 1–31

Material. HOLOTYPE: male larva, RUSSIAN FEDERATION, Amurskaya Oblast, Amur River basin, Talali River, tributary Belaya River, 51.541111° N 127.271944° E, 21.VII.2006, T. Tiunova. Paratypes: one larva, same data as holotype; 3 larvae, middle age, Khabarovskiy Kray, Bureinskiy district, Sinel’ River, bridge, 7 km lower Talakan village, 50.241405° N 130.181227° E, 4.VII.2014, T. Tiunova.

Description. Mature larva. Length (mm): body 5.6–5.7; cerci and paracercus 2.5–3.3. General body color light brown to brown with slightly pronounced maculation (Figs 1–2).

Head: brown with dark marking on vertex; frons and lateral margins with long hairlike setae; antennae brownish (Figs1–2).

Mouthparts. Labrum wide, rectangular (width/length ratio of 1.9 – 2.0), anterior margin with shallow emargination medially and with cilialike setae; dorsal surface with long, stout and fine hairlike setae and pores; lateral margins with long setae (Fig. 3). Incisor of right mandible with two blunt and rounded teeth, one about two times wider than other (Figs 4–5); group of long setae under mola (Fig. 4); incisor of left mandible with five rounded teeth, third one largest (Figs 6–7); basal area of mandibles with long, fine, hairlike setae and pores; area near mola serrated (Figs 7–8). Maxillary palp 3-segmented, well developed; first and third segments relatively equal length; second segment 2.5 times shorter than first and third segments (Figs 9 – 10); tip of third segment with short apical spine (Fig. 11); group of 9 – 10 long setae situated on inner side of maxilla (Fig. 9); lateral margins of maxilla with long fine hairlike setae. Paraglossae slightly shorter than glossae; surface of segments I and II of labial palps with long hairlike setae (Fig. 12); third segment smallest, conical, rounded apically, with short stout blunt setae more numerous on apex (Fig. 13).

Thorax. Pronotum brown or light brown with lighter lateral margins. Mesonotum brown or light brown (Figs 1 –2). Surface of thorax densely covered with pores (Figs 19 – 20). All legs yellowish (Figs 1 – 2). Femora of legs broadened slightly. Fore femur with transverse row of long, stout and pointed setae in mid-region; length of these setae ½ of width of femur (Fig. 14); inner margin of femur with row of long hairlike setae and small pointed setae; outer margin with long hairlike setae, length equal to width of femur; basal area with group of setae of various types and sizes: elongated setae widening and blunt apically, and short pointed setae (Fig. 15). Tibiae and tarsi with regular rows of stout, pointed setae on inner margins and with hairlike setae on outer margins (Fig 14). Femur of middle leg with small, spatulate setae and long hairlike setae on inner margin; regular row of pointed setae along margin; mid-region with regular row of 5 – 6 spatulate setae (Fig. 16). Tibia and tarsi with hairlike setae on outer margins; on inner margins setae not numerous; distal margins of tarsi with 4 – 5 blunt setae. Dorsal surface all legs densely covered small with scale-like setae (Fig. 15). Claws without denticles (Fig. 17).

Lengths (mm) of leg segments. Fore leg: femur 0.8–0.9; tibia 0.55–0.6; and tarsus 0.55–0.6. Middle leg: femur 0.9; tibia 0.5–0.6; and tarsus 0.55–0.6. Hind leg: femur 0.9–1.0; tibia 0.6; and tarsus 0.5–0.55. Ratio of width to length of fore femur 0.38–0.39; middle femur—0.33–0.34, hind femur—0.30.

Abdomen. Tergites brown or light brown without maculation, lateral margins lighter. Tergum X lighter than others; tergites IV–VI with dark brown stripe at gills attachment (Figs 1, 18). All surfaces of tergites covered by small, stout, pointed setae (Fig. 19); posterior margins of tergites IV–IX with sparse row of spatulate setae (Fig. 20); tergites II–III without posterolateral projection (Figs 1–2, 18); posterolateral projection of tergites IV–IX well developed (Figs 1–2, 25); densely covered with strong, long and middle hairlike and spatulate setae of various sizes (Figs 21–22). Sternites yellowish without maculation; surfaces covered with scattered spatulate setae (Fig. 26). Gill I filament-like (Figs 1, 18); gill IV wide, slightly tapering distally; distal margin with shallow notch in middle part and rounded protrusion on outer side (Fig. 28); gills V and VI of same shape with strongly attenuated, rounded distal margin (Figs 29–30); gill VII subtriangular, with rounded distal margin (Fig.31); gills IV and VI subequal in length; gill V smaller then gills IV and VI; gill VII very small, covered by gill VI. Cerci and paracercus yellowish, of same length; brownish bands present on basal part of filaments (Fig. 27).

Diagnosis. Larva. Maxillary palp 3-segmented, well developed; first and third segments relatively equal length; second segment of maxillary palp 2.5 times shorter than first and third segments (Figs 9–10); third segment of labial palps smallest, conical, rounded apically, with short stout blunt setae more numerous on apex (Figs 12–13); fore femora with transverse row of long, stout and pointed setae in mid-femora; the length of the setae is ½ of the width of the femora (Fig. 14); claws without denticles (Fig. 17); tergites II–III without posterolateral projection (Figs 1–2, 18); posterolateral projection of tergites IV–IX well developed (Figs 18, 25); gills on segment I consist-ing of a single filament (Fig. 1, 18); gill IV wide, slightly tapering by distally; distal margin with a shallow notch in middle part and rounded protrusion on the outer side (Fig. 28).

Distribution. Dannella daurica sp. nov. is known from two habitats in the Far East of Russia: Amurskaya oblast’ and Khabarovskiy Kray (Figs 32 –33). The larvae of the new species were found in relatively slow flow and in gravel-sand substrate. Water temperature was 17.8 – 22.0°C, depth 50 – 70 cm. The width of the rivers in the places of collection of larvae does not exceed 10 m; the length of these rivers is up to 50 km.

Etymology. The name of the new species is associated with its habitat (Amur River basin, the Bureya River basin), located in the Daurian botanical-geographical region.

Discussion. Among species of Dannella with available larvae description, Dannella daurica sp. nov. differs from the Nearctic species Dannella lita and D. provonshai by the absence of posterolateral processes on abdominal segment III (Figs 1 – 2, 18). In D. lita, posterolateral processes of segment III are well-developed (McCafferty 1977: Fig. 17); in D. provonshai segment III has small, rounded posterolateral processes (McCafferty 1977: Fig. 18). By the absence of posterolateral processes on the third abdominal segment, Dannella daurica sp. nov. is similar to D. simplex, but can be distinguished by the following features: (1) General body color light brown without visible maculation (Figs 1 – 2); in D. simplex general color tan to brown with dark brown marks on abdominal dorsum (Burks 1953). (2) Fore femora broadened slightly; the ratio of width to length is 0.38–0.39 (Fig. 14); in D. simplex the ratio of width to length is 0.42–0.44 (David Funk, unpublished).