Epeorus (Caucasiron) lanceolatus Hrivniak & Sroka, 2025

Hrivniak, Ľuboš, Sroka, Pavel, Godunko, Roman J., Martynov, Alexander V., Palatov, Dmitry M. & Bojková, Jindřiška, 2025, Discovering diversity of Central Asian and Himalayan Epeorus (Caucasiron) mayflies (Ephemeroptera, Heptageniidae) using DNA barcoding and morphology, ZooKeys 1234, pp. 89-125 : 89-125

Epeorus (Caucasiron) lanceolatus Hrivniak & Sroka sp. nov.

Figs 7 , 8 , 9

Type material.

Holotype: • female larva (barcoded specimen: IN 6 - labrum, leg and tergum VII mounted on slide): India Uttarakhand Pradesh, vicinity of Lambagad village, Alaknanda River , 1998 m a. s. l.; 30°38.64198'N, 79°32.02500'E (codes: IND 2018 / 8; 40 Gang); 9–11.05. 2018, Martynov A. V., Palatov D. M. leg. Paratypes: • 1 larva (barcoded specimen: IN 2 - labrum, mandibular incisors and tergum VII mounted on slide), 1 female imago (reared from larva; barcoded specimen: L 38 - larval exuvium mounted on slide): same data as holotype .

Etymology.

The species name lanceolatus (Latin) refers to lanceolate setae on abdominal terga and dorsal surface of femora characteristic for larvae.

Description of larva.

General coloration yellowish brown with dark brown to blackish maculation (Fig. 7 ). BL of late-instar larva 13.87 mm (female; n = 1); male unknown. Length of cerci unknown.

Head. Shape oval to trapezoidal (Fig. 7 A ). Head dimensions of late-instar larva: length 3.5 mm, width 5.7 mm (female; n = 1), male unknown. Head width / length ratio: 1.53 (female; n = 1), male unknown. Coloration pattern of dorsal surface consists of: i) paired stripe-like and rounded maculae along epicranial suture, ii) pair of triangular (or blurred) maculae near inner edges of eyes, iii) pair of rounded maculae ventrally to lateral ocelli, iv) pale stripes extending from lateral ocelli to lateral edges of head, v) blurred or rectangular maculae between ocelli, vi) scattered maculae ventrally to median ocellus. Antennae yellowish brown, scapus and pedicellus darkened. Dorsal surface of head densely covered with elongated lanceolate setae (as on abdominal terga; Fig. 8 E, F ), fine hair-like setae and stick-like setae. Sparse longer and fine hair-like setae located posteriorly to eyes.

Mouthparts. Labrum (Fig. 8 A ) widened anteriorly; anterior margin slightly rounded or straight. Lateral angles rounded. Dorsal surface sparsely covered with setae of different size, five or six longer bristle-like setae located antero-medially, and two bristles antero-laterally (Fig. 8 A , left half). Epipharynx with longer, slightly plumose bristles situated along lateral to anterior margin, cluster of fine, hair-like setae medially (not figured), and group of 4–6 setae of various size (Fig. 8 A , right half). Outer incisors of both mandibles with three apical teeth; outer tooth blunt in both mandibles. Inner incisor of left mandible with three apical teeth (Fig. 8 B ), right inner incisor bifurcated (Fig. 8 C ).

Thorax. Prothorax anteriorly narrowed, lateral edges slightly rounded. Metanotum with small blunt posteromedian projection. Dorsal surface covered with hair-like setae, stick-like setae, and lanceolate setae (as on abdominal terga and head, Fig. 8 E, F ); sparse longer, hair-like setae along pro-, meso- and metanotal suture.

Legs. Coloration on Fig. 7 B . Femora with medial hypodermal spot, often transversely extended. Base and apex of femora darkened; patella-tibial suture darkened; tarsi proximally and distally darkened. Dorsal surface of femora covered by lanceolate setae, hair-like setae, and sparsely distributed stick-like setae (Fig. 8 E ; drawn from late-instar larvae and last instar larval exuvium). Dorsal edge of femora with blade-like setae. Dorsal margin of tibiae and tarsi with row of dense hair-like setae; ventral margin with irregular row of distally accumulated spines. Tarsal claws with 3–4 denticles.

Abdominal terga. Colour pattern of abdominal terga consists of transversal stripe along anterior margin of terga I – IX (X) medially extending to: i) triangular macula on terga II – IV, ii) T-shaped macula on terga V – VI (VII), and iii) triangular macula on terga (VII) VIII – IX (Fig. 7 C ). Pair of short stripes sometimes present antero-laterally to median macula. Lateral margins with oblique stripe-like maculae on terga I – IX. Denticles along posterior margin on terga dense, relatively narrow, irregular, and pointed (Fig. 8 F ). Surface of terga covered with hair-like setae, stick-like setae, and lanceolate (sporadically narrow spatulate) setae (Fig. 8 E, F ; drawn from late-instar larvae and last instar larval exuvium). Tergum X with well-developed posterolateral projections (Fig. 8 L, M , arrow). Terga with longitudinal median row of hair-like setae. Tergal spines not observed in late-instar larvae and larval exuvium from reared adult.

Abdominal sterna. Yellowish, with fine oblique stripes (slightly curved in late-instar larvae; Fig. 7 E, F ). Nerve ganglia darkened. Sternum IX of female with V-shaped median emargination and numerous hair-like setae (Fig. 8 N ).

Gills. Dorsal surface of gill plate I yellowish; of gill plates II – VII brownish on anterior half, greyish to brownish on posterior half. Ventral margin of all gill plates yellowish. Projection of gill plate III well developed (Fig. 8 H , arrow). Gill plate VII narrow (in natural position of ventral view, Figs 7 D , 8 K ). Dorsal margin of gill plates IV – VII with more or less developed papillae; best expressed on gill plates VI and VII (Fig. 8 I ).

Cerci. Yellowish brown, basally darkened.

Description of female imago.

General coloration yellowish brown with dark brown to blackish maculation (Fig. 9 A – F ). Body length 14.0 mm (n = 1); length of cerci unknown. Length of fore wings 17.5 mm, length of hind wings unknown (broken).

Head. Frons brownish; frontal fold dark brown (Fig. 9 B, C ). Antennae yellowish brown; scapus and pedicellus darkened. Eyes greyish, ocelli basally blackish, apically whitish.

Thorax. Prothorax dark brown. Mesothorax yellowish brown; median longitudinal suture darkened. Metathorax with short posterior-median blunt projection. Furcasternum dark brown. Wing membrane of fore wings in subimago cloudy, cross veins darkened (Fig. 9 A ); hind wings unknown. Femora apically and basally darkened; median spot present (Fig. 9 G ). Tibiae apically and basally darkened, tarsi brownish. One claw blunt, one claw pointed.

Abdomen. Coloration pattern of abdominal terga similar as in late-instar larvae (Fig. 9 D – F ). Tergum X with medial macula. Lateral margins with oblique stripe-like maculae on terga I – IX extending dorso-posteriorly, forming transversal stripe-like macula along posterior margin of terga (Fig. 9 D, E ). Abdominal sterna with fine, slightly curved oblique stripes (Fig. 9 F ). Nerve ganglia darkened. Subgenital plate posteriorly narrowed, posterior margin slightly rounded. Subanal plate posteriorly narrowed; posterior margin straight (Fig. 9 I ).

Cerci. Unknown.

Description of eggs.

Oval shaped, dimensions approximately 186 × 110 μm (average values from 7 eggs). Chorionic surface with texture as on Fig. 9 L . One to three visible micropyle shallow and rounded, located in subequatorial position (~ 12.5 μm in width) (Fig. 9 J, K ).

Male imago. Unknown.

Main morphological diagnostics of larva.

i) abdominal sterna with fine oblique stripes (slightly curved in late-instar larvae; Fig. 7 E, F ), ii) coloration of abdominal terga as on Fig. 7 C, iii ) femora with femur spot (Fig. 7 B ), iv) dorsal surface of femora with lanceolate setae (Fig. 8 D ), v) abdominal terga with lanceolate (sporadically narrow spatulate) setae (Fig. 8 E, F ), vi) tergum X with well-developed posterolateral projections (Fig. 8 L, M , arrow), vii) gill plates VII narrow (in natural position from ventral view; Figs 7 D , 8 K ), viii) denticles along posterior margin of abdominal terga dense, relatively narrow, irregular and pointed (Fig. 8 F ).

Main morphological diagnostics of imago

(female). i) abdominal sterna with fine, slightly curved oblique stripes (Fig. 9 F ), ii) femora with a median spot (Fig. 9 G ), iii) wing membrane colourless, iv) subgenital plate posteriorly slightly rounded, iv) subanal plate posteriorly straight (Fig. 9 H, I ).

Morphological affinities.

Larva. Epeorus (C.) lanceolatus sp. nov. is characterised by lanceolate setae on the dorsal surface of femora and abdominal terga (Fig. 8 D, E ). This trait, together with the remaining seven traits, given above distinguishes the species from all E. (Caucasiron) species described so far and also from E. suspicatus , whose attribution to the subgenus Caucasiron is uncertain (Figs 15 , 16 ). Similar lanceolate setae on the dorsal surface of femora are present in E. psi (Fig. 18 D ). Epeorus (C.) lanceolatus sp. nov. differs from this species by dense, relatively narrow, irregular, and pointed denticles along the posterior margin of abdominal terga (Fig. 8 F ) and by a short dorso-apical projection of femora (Fig. 7 B ), in contrast to E. psi with basally denticulate spines and shorter denticles along abdominal terga (Fig. 18 F ) and an elongated pointed dorso-apical projection of femora (Figs 17 F , 18 M ). The characters distinguishing E. kapurkripalanorum from E. (C.) lanceolatus sp. nov. are given in the section “ Remarks on Iron paraguttatus (Braasch, 1983) and E. kapurkripalanorum (Braasch, 1983) ”.

Female imago. The presence of the fine, slightly curved oblique stripes on abdominal sterna (Fig. 9 F ) separates E. (C.) lanceolatus sp. nov. from E. (C.) guttatus , with a pair of oblique stripes and a large median macula on abdominal sterna ( Kluge 2015), E. (C.) extraordinarius , with an longitudinal reddish brown median macula on abdominal sterna ( Chen et al. 2010), E. (C.) himalayensis sp. nov., with narrow triangular maculae (Fig. 6 F ) and E. psi , with a fine longitudinal median line (sometimes reduced anteriorly) and a pair of oblique stripes on abdominal sterna ( Eaton 1883–1888). In addition, E. (C.) lanceolatus sp. nov. can be distinguished from E. (C.) himalayensis sp. nov. by the straight posterior margin of subanal plate (Fig. 9 H, I ), in contrast to E. (C.) himalayensis sp. nov. with a shallow emargination (Fig. 6 G – I ).

Among the extralimital species, E. (C.) caucasicus and E. (C.) nigripilosus show similar coloration pattern on abdominal sterna ( Braasch 1979). However, the female imagoes of both species have not been described, thus female genitalia cannot be compared with E. (C.) lanceolatus sp. nov. Epeorus (C.) lanceolatus sp. nov. can be separated by fine and slightly curved oblique stripes on abdominal sterna (Fig. 9 F ), in contrast to E. (C.) caucasicus and E. (C.) nigripilosus with well pigmented pattern ( Braasch 1979). Moreover, both species are geographically restricted to the western part of the E. (Caucasiron) range ( Hrivniak et al. 2020 b).

Figures

Figure 6. Epeorus (Caucasiron) himalayensis sp. nov., female imago and egg A habitus in lateral view B head in dorsal view C head in lateral view D abdomen in dorsal view E abdomen in lateral view F abdomen in ventral view G – I subgenital and subanal plates J egg K detail of micropyle. Scale bars: 5 μm (K); 50 μm (J).

Figure 7. Epeorus (Caucasiron) lanceolatus sp. nov., larva A head of female in dorsal view (holotype) B fore leg in dorsal view C coloration of abdominal terga D distal part of abdomen in ventral view E, F coloration of abdominal sterna II – VI (E holotype).

Figure 8. Epeorus (Caucasiron) lanceolatus sp. nov., larva A labrum, left half in dorsal view, right half in ventral view (black dots correspond to setae along antero-lateral margin) B incisors of left mandible C incisors of right mandible (both flattened on slide; dashed polygons correspond to area covered by setae) D setae on dorsal surface of femora E setae on surface of tergum VII F surface and posterior margin of abdominal tergum VII (holotype) G gill I H gill III (arrow shows projection on costal margin) I gill plate VI in dorsal view J gill VII (flattened on slide) K gill plate VII in ventral view L, M abdominal segments VIII – X in lateral view (arrow shows posterolateral projection of tergum X) N sternum IX of female. Drawn from late instar larva and last instar larval exuvium.

Figure 9. Epeorus (Caucasiron) lanceolatus sp. nov., female imago (wing and head not fully molted from subimago) A habitus in dorsal view B head in dorsal view C head in lateral view D abdomen in dorsal view E abdomen in lateral view F abdomen in ventral view G middle leg H, I subgenital and subanal plates J egg K detail of micropyle L texture on the surface of egg. Scale bars: 50 μm (J); 5 μm (K, L).

Figure 15. Epeorus (Caucasiron?) suspicatus, larva A habitus in dorsal view B habitus in ventral view C habitus in lateral view D head of male in dorsal view (holotype) E head of female in dorsal view F middle leg in dorsal view G, H coloration of abdominal terga (G holotype) I – J coloration of abdominal sterna II – VI (I holotype) K, L distal part of abdomen in ventral view (K holotype).

Figure 16. Epeorus (Caucasiron?) suspicatus, larva A labrum, left half in dorsal view, right half in ventral view (black dots correspond to setae along antero-lateral margin) B incisors of left mandible C incisors of right mandible (both flattened on slide; dashed polygons correspond to area covered by setae) D setae on dorsal surface of femora E setae on surface of tergum VII F surface and posterior margin of abdominal tergum VII G gill I H gill III (arrow shows projection on costal margin) I gill plate VI in dorsal view J gill plate VII (flattened on slide) K gill plate VII in ventral view L abdominal segments VIII – X in lateral view (arrow shows indistinct posterolateral projection of tergum X) M sternum IX of female. Drawn from late instar larvae.

Figure 17. Epeorus (Caucasiron?) psi, larva A habitus in dorsal view B habitus in ventral view C habitus in lateral view D head of male in dorsal view E head of female in dorsal view F legs in dorsal view (arrows point to elongated and pointed dorso-apical projections) G coloration of abdominal terga H coloration of abdominal sterna II – VI I distal part of abdomen in ventral view.

Figure 18. Epeorus (Caucasiron?) psi, larva A labrum, left half in dorsal view, right half in ventral view (black dots correspond to setae along antero-lateral margin) B incisors of left mandible C incisors of right mandible (both flattened on slide; dashed polygons correspond to area covered by setae) D setae on dorsal surface of femora E setae on surface of tergum VII F surface and posterior margin of abdominal tergum VII G gill I H gill III (arrow shows projection on costal margin) I gill plate VI in dorsal view J gill plate VII in ventral view K gill plate VII (flattened on slide) L abdominal segments VIII – X in lateral view (arrow shows posterolateral projection of tergum X) M detail of dorso-apical projection of femora (middle leg) N sternum IX of female. Drawn from late instar larvae.