Epeorus (Caucasiron) hyrcanicus Hrivniak & Sroka, 2021

Hrivniak, Ľubos, Sroka, Pavel, Bojkova, Jindriska, Godunko, Roman J. & Manko, Peter, 2021, A new species of Epeorus (Caucasiron) (Ephemeroptera, Heptageniidae) from Azerbaijan and Iran, ZooKeys 1068, pp. 13-26 : 13

publication ID	https://dx.doi.org/10.3897/zookeys.1068.70717
persistent identifier	https://treatment.plazi.org/id/3CAFD9C5-F391-5B42-9029-14E2B529FA07
treatment provided by	ZooKeys by Pensoft
scientific name	Epeorus (Caucasiron) hyrcanicus Hrivniak & Sroka
status	sp. nov.

Treatment

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

Figures 4 View Figure 4 , 5 View Figure 5

Caucasiron sp. 3 of Hrivniak et al. 2020c

Notes.

Epeorus (Caucasiron) hyrcanicus sp. nov. is attributed to the subgenus Caucasiron within the genus Epeorus s.l. based on the following larval morphological characters: i) projections on the costal rib of gill plates II-VII, ii) presence of medio-dorsally directed hair-like setae located on the anterior margin of the head (see Kluge 2015 for a revision of the subgenus Caucasiron ).

Type material.

Holotype: female larva: Azerbaijan, Lənkəran Province, NW of Azaru village, unnamed brook (left tributary (LT) of Vasharu River); 38.5873689N, 48.5870392E (locality AZE5/2018); 1028 m a.s.l.; Ľ. Hrivniak, M. Žiak leg., 21.9.2018. Paratypes: 5 larvae (2 barcoded and mounted on slide; labelled CFC1, CFC2): same data as holotype.

1 larva (mounted on slide): Azerbaijan, Lənkəran Province, SW of Sim village, unnamed brook (tributary of Digo River); 38.4824842N, 48.6243081E (locality AZE6/2018); 734 m a.s.l.; Ľ. Hrivniak, P. Manko leg., 21.9.2018.

4 larvae (one barcoded and mounted on slide; labelled N4): Iran: Gilan Province, NW of Sangdeh village, unnamed brook (LT of Shafa-rud River); 37.5294444N, 48.7552778 E (locality no. 12); 1345 m a.s.l.; J. Bojková, T. Soldán, J. Imanpour Namin leg., 15.5.2016.

1 larva (barcoded; labelled N2): Iran, Gilan Province, S of Tushi village (S of Siahkal village), Shamrud River (RT of Sefid-rud River); 37.0500000N, 49.8983333E (locality no. 17); 314 m a.s.l.; J. Bojková, T. Soldán, J. Imanpour Namin leg., 16.5.2016.

Other material (damaged larvae).

4 larvae (2 barcoded and mounted on slide; labelled CFC4, CFC3): same data as holotype .

1 larva (barcoded; labelled N3): Iran, Gilan Province, W Chelvand village (S of Lavandvil village), Chelavand River (about 2.5 km from its mouth); 38.2888889N, 48.8597222E (locality no. 27); - 4 m a.s.l.; J. Bojková, T. Soldán, J. Imanpour Namin leg., 19.5.2016 GoogleMaps .

Etymology.

The name refers to the distribution of the species in the Hyrcanian forest.

Distribution and habitat preferences of larvae.

The species is distributed in northwestern Iran and southeastern Azerbaijan (Fig. 1 View Figure 1 ) at -4 to 1345 m a.s.l. Larvae were found in streams and rivers flowing to the Caspian Sea in the humid forested slopes of western Alborz. They likely inhabit only cold and clear streams and rivers with stony bed substrate and turbulent flow. The species was not found in urban and agricultural areas in this region where many localities were investigated. Larvae were not abundant in either locality and co-occurred with the more abundant E. (C.) znojkoi .

Description of larva.

General coloration of larvae yellowish-brown, with dark brown to reddish maculation. Body length of male mature larva 8.25 mm (n = 1); cerci broken. Body length of female mature larvae unknown.

Head. Shape oval to trapezoidal (Fig. 4D, E View Figure 4 ). Anterior margin with shallow concavity medially. Head dimensions: length 2.20 mm, width 3.04 mm (male); dimensions of female mature larva unknown. Head width/length ratio 1.36-1.41 (male), 1.40-1.44 (female). Coloration pattern as in Figure 4D, E View Figure 4 . Dorsal surface of head covered with fine hair-like setae and sparsely distributed stick-like setae. Sparse longer hair-like setae located posteriorly to eyes.

Mouthparts. Labrum (Fig. 5A View Figure 5 ) widened anteriorly, with anterior margin slightly rounded (in dorsal view). Lateral angles rounded (shape of labrum may vary among specimens). Dorsal surface (Fig. 5A View Figure 5 , right half) sparsely covered with setae of different size; four longer bristle-like setae located antero-medially and two antero-laterally. Epipharynx with longer, slightly plumose bristles situated along lateral to anterior margin (Fig. 5A View Figure 5 , left half; range of setation figured as large black dots), and cluster of fine, hair-like setae medially (not figured). Posterior margin of labrum irregularly concave; group of 11-13 setae of various sizes located on ventral surface close to posterior margin. Outer incisors of both mandibles (Fig. 5B, C View Figure 5 ) with three apical teeth; outer tooth blunt in both mandibles. Inner incisor of left mandible with three apical teeth (Fig. 5B View Figure 5 ), right inner incisor bifurcated (Fig. 5C View Figure 5 ).

Thorax. Pronotum anteriorly narrowed, lateral edges nearly straight. Metanotum with slight postero-medial projection. Dorsal surface covered with fine, hair-like setae (as on abdominal terga and head); sparse longer hair-like setae along pro-, meso- and metanotal suture.

Legs. Colour pattern of femora as in Figure 4F, G View Figure 4 . Femora with medial hypodermal spot; often distally blurred (Fig. 4F View Figure 4 ) or poorly expressed (Fig. 4G View Figure 4 ). Patella-tibial suture darkened; tarsi proximally and distally darkened. Coxal projections of fore- and hind legs pointed or bluntly pointed; in middle legs blunt. Spatulate setae on dorsal surface of femora short, sporadically elongated (Fig. 5D View Figure 5 ). Tarsal claws with 3-4 denticles.

Abdominal terga. Colour pattern of abdominal terga (Fig. 4A, H-I View Figure 4 ) consisting of transversal stripe along anterior margin of terga I-IX (X), medially extending, forming rectangular or triangular macula on terga II-IV (sometimes blurred), triangular macula on terga V-VII, and triangular or rectangular macula on terga VIII-IX (X). Lateral margins with oblique maculae on terga I-VIII (IX). Denticles on posterior margin of terga relatively dense, of various sizes, pointed and sometimes curved (Fig. 5E View Figure 5 ). Surface of terga covered with hair-like setae and sparsely with stick-like setae. Tergum X with short or without postero-lateral projections (Fig. 5L, M View Figure 5 ; arrow). Medial longitudinal row of hair-like setae along abdominal terga present.

Abdominal sterna. Yellowish, with dark brown to blackish pattern. Sterna II-VI with a pair of oblique stripes (medio-anterior sigilla) and a pair of stripe-like (or elongated triangular) medio-lateral maculae joined to medio-anterior sigilla (Fig. 4L-N View Figure 4 ; arrows). Intensity of colouration varies among individuals; stripe-like (or elongated triangular) medio-lateral stripes sometimes poorly developed (Fig. 4O View Figure 4 ). Nerve ganglia darkened. Sternum IX with V-shaped medial emargination; surface covered by irregularly distributed hair-like setae (Fig. 5N View Figure 5 ).

Gills. Dorsal surface of gill plates I yellowish; of gill plates II-VII yellowish on anterior half, brownish to reddish on posterior half. Ventral margin of all gill plates yellowish to greyish. Projection of gill plates III poorly developed (Fig. 5G View Figure 5 ; arrow). Gill plates VII relatively wide (in natural position of ventral view; Fig. 4J, K View Figure 4 ; 5H-K View Figure 5 ).

Cerci . Yellowish brown, basally darkened.

Subimago, imago and eggs.

Unknown.

Morphological diagnostics of larvae.

The main larval diagnostic characters of E. (C.) hyrcanicus sp. nov. are as follows: (i) abdominal sterna II-VI with pair of oblique stripes (Fig. 4L-O View Figure 4 ) and stripe-like (or elongated triangular) medio-lateral maculae (Fig. 4L-N View Figure 4 ; arrows), (ii) terga V-VII with triangular medial maculae (Fig. 4H, I View Figure 4 ), iii) femora with medial hypodermal spot, sporadically absent, reduced, or distally blurred (Fig. 4F, G View Figure 4 ), (vi) fine hair-like setae on surface of abdominal terga (Fig. 5E View Figure 5 ), (v) poorly developed projection on gill plates III (Fig. 5G View Figure 5 ; arrow), and (vi) relatively wide shape of gill plates VII (in natural position from ventral view; Fig. 4J, K View Figure 4 ; 5H-K View Figure 5 ).

Results from molecular species delimitation.

The GMYC species delimitation model applied to COI gene tree provided significantly better fit for a speciation branching than null model suggesting uniform coalescent branching across the entire tree (likelihood ratio test = 6.258895e-07***). The GMYC estimated 16 species (CI = 11-18) consisting of 15 ML clusters and one singleton ( E. (C.) insularis ). Morphologically defined E. (C.) hyrcanicus sp. nov. was delimited as a distinct species based on both GMYC and ABGD species molecular delimitation analyses. All species clusters were highly supported (PP = 1; Fig. 3 View Figure 3 ).

The intraspecific pairwise genetic distances between specimens of E. (C.) hyrcanicus sp. nov. reached up to 1.75%. The minimum (and mean) interspecific distances between E. (C.) hyrcanicus sp. nov. and other Caucasiron species ranged between 8.11% (8.84%; E. (C.) nigripilosus ) and 15.52% (15.88%; E. (C.) alpestris ).

Morphological affinities.

Although the combination of larval morphological diagnostic characters listed above clearly determine E. (C.) hyrcanicus sp. nov. from all Caucasiron species known so far, some of the species distributed in the Caucasus and adjacent areas possess nearly identical states of some characters. Distinguishing of E. (C.) hyrcanicus sp. nov. from these species is described in detail below.

Coloration pattern of abdominal sterna II-VI makes E. (C.) hyrcanicus sp. nov. the most similar to E. (C.) caucasicus (widely distributed in the Caucasus), E. (C.) iranicus (distributed in Alborz Mountains), and E. (C.) zagrosicus (distributed in Zagros Mountains). The pattern of all these species consists of a pair of oblique stripes (medio-anterior sigilla). E. (C.) hyrcanicus sp. nov. usually exhibits oblique stripes together with a pair of stripe-like (or elongated triangular) medio-lateral maculae (Fig. 4L-N View Figure 4 ; arrows), in contrast to E. (C.) caucasicus and E. (C.) iranicus without such maculation ( Hrivniak et al. 2020a: figs 4J, 22I, J).

Weakly pigmented specimens of E. (C.) hyrcanicus sp. nov., i.e. without distinctly pigmented medio-lateral maculae on abdominal sterna II-VI (Fig. 4O View Figure 4 ) possess the same coloration pattern as in E. (C.) caucasicus and E. (C.) iranicus . Such specimens are identifiable by the triangular shape of medial maculae on abdominal terga V-VII (Fig. 4H, I View Figure 4 ). In contrast to E. (C.) hyrcanicus sp. nov., E. (C.) caucasicus bears crown-like medial maculae on terga V-VII ( Hrivniak et al. 2020a: fig. 4I), and E. (C.) iranicus stripe-like medial maculae with distinct antero-lateral stripes ( Hrivniak et al. 2020a: fig. 22G).

The oblique stripes on abdominal sterna II-VI in E. (C.) zagrosicus are anteriorly widened ( Hrivniak et al. 2020a: fig. 46I). This feature separates this species from E. (C.) hyrcanicus sp. nov.

In E. (C.) hyrcanicus sp. nov., the coloration pattern of abdominal terga V-VII, legs, and shape of gill plates VII (in natural position from ventral view) is similar to E. (C.) shargi (distributed in the eastern Alborz Mountains) ( Hrivniak et al. 2020a: fig. 43). From this species, E. (C.) hyrcanicus can be distinguished by the presence of the coloration pattern on abdominal sterna II-VI (Fig. 4L-O View Figure 4 ), in contrast to E. (C.) shargi , where the pattern is missing ( Hrivniak et al. 2020a: fig. 43L). The poorly developed projection on gill plates III in E. (C.) hyrcanicus sp. nov. (Fig. 5G View Figure 5 ; arrow) also differs from E. (C.) shargi with well-developed projection ( Hrivniak et al. 2020a: figs 44G). Additionally, E. (C.) hyrcanicus usually bears short postero-lateral projection on tergum X (Fig. 5M View Figure 5 ; arrow), in contrast to E. (C.) shargi without such projection ( Hrivniak et al. 2020a: fig. 44J).

Well-defined triangular medial maculae on abdominal terga V-VII are characteristic also for E. (C.) soldani (distributed in the western and central Greater Caucasus Mountains). Epeorus (C.) hyrcanicus sp. nov. can be separated from E. (C.) soldani by hair-like setae on abdominal terga (Fig. 5E View Figure 5 ), in contrast to the wide setae in E. (C.) soldani ( Hrivniak et al. 2020a: fig. 20E). Additionally, the gill plates VII (in natural position from ventral view) are wider in E. (C.) hyrcanicus sp. nov., in contrast to E. (C.) soldani with narrow shape ( Hrivniak et al. 2020a: fig 19L), and the projection on gill plates III is poorly developed in E. (C.) hyrcanicus sp. nov., in contrast to E. (C.) soldani with well-developed projection ( Hrivniak et al. 2020a: fig. 20G).