Baetis (Rhodobaetis) molecularis Tiunova & Semenchenko 2020, sp. nov.

Baetis (Rhodobaetis) molecularis sp. nov.

urn:lsid:zoobank.org:act: FAB4B007-959E-41E3-AB7C-07B5AA1D15C3

(Figs 1–44)

Baetis bicaudatus Tshernova et al. 1986:133, figs 3–4.

Baetis bicaudatus: Ishiwata et al. 2000:71, fig. 4A–H.

Baetis (Baetis) bicaudatus: Tiunova 2007:185.

Baetis (Baetis) bicaudatus: Tiunova 2009:678.

Baetis bicaudatus: Tiunova & Gorovaya 2015:230.

Baetis bicaudatus: Khamenkova et al. 2017: http://biosoil.ru/doclib/article_188.doc

Material. Holotype male imago (reared from larva), RUSSIAN FEDERATION: KAMCHATSKAYA OBLAST’: Kamchatka Peninsula: Paratunka River Basin: Bistraya River, a turn on the Paratunka village, N 53°58.019 E 157°44.495, 04.IX.2018, I. Tiunov. Paratypes: collected the same date and place as holotype: 17 larvae, 1 male, 2 female, female (MT 027023) imagines (reared from larva); same place, 30.VII. 2015, 3 male, 4 female imagines, I. Tiunov; Trezubez River, at the Paratunka Fish hatchery, 26.VII.2015, 13 larvae, larva (MT 027021), I. Tiunov; Avacha River Basin: Topolovaya River, tributary of Koryakskaya River, N 53°07. 037 E 156°51.474, 28.VII.2015, 1 larvae; same place, 30.VII.2015, 9 larva; same place, 04.IX.2018, 7 larvae, I. Tiunov; Koryakskaya River, mouth, duct Svetlaya, 28.VII.2015, 8 larvae, I. Tiunov; Ozernaya River, tributary of Koryakskaya River, 28.VII.2015, 6 larvae, I. Tiunov; Poperechnaya River, tributary of Koryakskaya River, 31.VII.2015, 40 larvae, I. Tiunov; Karymshina River Basin, Serebryannyi Stream, N 52°54. 372; E 158°12.034, 29.VII.2018, 19 larvae, larva (MT 027028), I. Tiunov; Bistraya River Basin: highway to the Ust’ - Kamchatsk city: Vatkan Malkinskiy River, bridge, N 53°29.176; E 157°35.219, 04.IX.2018, 8 larvae, larva (MT 027027), larvae (MT 027019), I. Tiunov; Tumkhan River, bridge, N 53°36.019; E 157°38.217, 04.IX.2018, 11 larvae, larva (MT 027021), T. Tiunov; Watkan Ganalsky River, N 53°31.599; E 157°36.311, 04.IX.2018, 14 larvae, larva (MT 027025), I. Tiunov; Poperechnaya River, N 53°25. 499 E 157°32.230, 04.IX.2018, 22 larvae, larva (MT 027022), I. Tiunov; Kizhichonok River, bridge, N 53° 48.11.0 E 157°40.205, 04.IX.2018, 4 larvae, I. Tiunov; Milkovskiy district, Malaya Klukvennaya River, N 54°19.560 E 158°15.387, 04.IX.2018, 5 larvae, I. Tiunov; Denohonok River, bridge, N 54°15.564 E 158°07.206, 04.IX.2018, 12 larvae, I. Tiunov; Kashkan River, N 54°10.162 E 157°58.101, 04.IX.2018, 18 larvae, 3 female, female imag-ines (MT 027026), I. Tiunov; Kamchatka River Basin: highway to the Ust’ - Kamchatsk city: Pravaya Kamchatka River, N 54°01.240 E 157°51.130, 04.IX.2018, 11 larvae, larva (MT 027020), I. Tiunov; Bersh River Basin: Gresh-naya River, N 54°15.046 E 158°06.348, 04.IX.2018, 31 larvae, larva (MT 027025), I. Tiunov; Kirgurop River, N 53°45.355 E 157°39.249; 05.IX.2018, 11 larvae, I. Tiunov; Mumoch River, bridge, N 53°15.354 E 157°27.115; 05.IX.2018, 7 larvae, I. Tiunov; Bacostits Stream, N 53°43.052 E 157°38.153, 05.IX.2018; Krutaya River, tributary of the Tumkhan River, N 53°35.122 E 157°38.073, 05.IX.2018, 13 larvae, I. Tiunov; stream between Kirgurop Riv-er and Bacostits Stream, N 53°43.526 E 157°39.007, 05.IX.2018, 9 larvae, I. Tiunov; Elezovskiy district, Plotnikova River Basin, Nachilova River, N 53°07. 038 E 156°51.474, 31.VII.2018; 11 larvae, larva (MT 027029), I. Tiunov; CHUKOTKA AUTONOMOUS DISTRICT, Elgygytgyn Lake Basin, nameless stream, N 67°43.565 E 172°08.972, 13.VIII.2017, 7 larvae, larva (MT 027018), A. Semenchenko; MAGADANSKAYA OBLAST’, Khasynskiy urban district, Ola River, below the bridge, 130-137 km, N 60°28.522 E 151°26.531, 29.IV.2014, 3 larvae, larva (MT 027015), E. Khamenkova; KHABAROVSKIY KRAY, Ulban Bay, stream in the southeastern part of the bay, N 53°37.565 E 138°02.549, 20.VIII.2016, 5 larvae, larva (MT 027017), I. Tiunov; AMURSKAYA OBLAST’: Zeyskii Reserve, Zeya Reservoir Basin, Bolshoi Garmakan River, about 300 m above mouth, N 53°53.148 E 127°11.626, 07.VII.2015, 9 larvae, larva (MT 027014), T. Tiunova; JEWISH AUTONOMOUS OBLAST’, Bastak Nature Reserve, Ikura River, Ryabinovii Cordon, 4.VIII.2019, 3 larvae, larva (MT 027030), T. Vshivkova

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Description. Male imago (in alcohol) (Fig. 1). Length (mm): body 7.6–8.0; forewings 7.8–8.0; cerci 16.3. Head: brown or brownish; antennae brownish. Turbinate eyes moderately high (Fig. 2); faceted surface oval in dorsal view, approximately 1.4 times longer than wide (Fig. 3); faceted surface brownish or yellowish; the shaft lighter, grayish or dirty yellow without rings. Thorax: Anterior phragma, anteronotal protuberance, medioscutum and submedioscutum brown or dark brown; median longitudinal and medioparapsidal sutures blackish; scuto-scutellar impression and scutellum pale; lateroparapsidal suture light brown (Fig. 1). Forelegs brownish or yellowish, middle and hind legs whitish with brownish distal spot on femora. Lengths ratio of individual foreleg segments: 1.6:2.5:1.1:1.0:0.6:0.25. Forewing transparent, all veins brownish; pterostigma milky on a dark background (Fig. 1). Hind wing hyaline, transparent, and approximately 2.7 times longer than wide, rounded apex and three simple longitudinal veins; third vein ending at approximately half of wing length; cross veins absent; costal projection well developed (Fig. 5). Abdomen: Terga I–V pale with brownish lateral sides; terga VI–X light brown, posterior margins darker. Sternum I brownish; sterna VII–IX light brown. Styliger with white middle area and brown anterior and lateral sides (Fig. 6). Unistyliger brown with whitish inner lateral area; nearly as long as wide with rounded bulge on the inside apex of the corner. Segment I of forceps brown with subparallel margins; segments II and III pale; segment II elongated and relatively narrow; inner margin of segment II noticeably concave; segment III widened in the distal part and truncated. Caudal filaments brownish or whitish.

Female imago. Length (mm): body 5.8–7.8; forewings 7.1–9.0; cerci 11.3–13.2. General color of body yellow to yellow-brown (Fig. 4). Head yellowish, antennae with brownish flagellum, darker than head. Eyes and base of ocelli black; apical part of ocelli whitish. Thorax yellow-brown, with brown median longitudinal and medioparapsidal sutures; submedioscutum darker than medioscutum. Wings transparent, all veins brownish; hind wing approximately 2.6 times longer than wide. Legs whitish, tarsal joints brownish. Abdominal terga yellow to yellow-brown. Terga VIII–X whitish in the middle area. Sterna from yellowish to whitish, lighter than terga. Cerci whitish.

Mature larvae (in alcohol). Length (mm): body 4.2–7.7; cerci 3.4–6.0. General body color brown or light brown (Figs 7–8). Head: brown, light between compound eyes and ocelli (Fig. 7). Antennae brownish, slightly shorter than ½ of body length; antennal pedicel no more than with three robust and small setae and fine hairs (Figs 10–11). Scape with long narrow distinctly pointed robust setae located on the side at the base (Figs 12–13). Labrum distinctly wider than long (width/length ratio of 1.74); dorsal surface with 1+9–10 long submarginal setae, arranged in one irregular row, and row of long pointed setae laterally on both margins; posterior area with thick long hair-like setae (Fig. 16). Canines of right mandible with 8 teeth divided into two groups. Incisor (outer group) with three teeth; outermost tooth broadened and almost straight apically; kinetodontium (inner group) with five teeth; the second largest; inner margin with row of short thin setae; prostheca elongated and slender with few not sharp teeth (Figs 14, 17). Left mandible canines with 8 teeth. Incisor with three teeth, first tooth widened and almost straight apically; kinetodontium with five teeth, from which first smallest and second largest; prostheca toothbrush-like (Fig. 18). Nymphs often with worn canines and not divided into groups; teeth are practically not expressed; left and right prostheca with short and rounded teeth (Figs 19–20). Maxillary palp two-segmented; tip of second segment rounded, with a single small spine situated at apex (Fig. 15); surface of both segments covered with hair-like setae; second segment longer than first segment (1.3 times) (Fig. 23). Labium with paraglossae concave in middle, approximately two times wider than glossae; apical part of paraglossae with two regular rows of long setae; 5–6 long bristles located along outer margin and one rounded stout subapical seta near top (Fig. 21). Glossae triangular with broad base, with row of 11–12 of long stout setae located near apex (Fig. 21). Second segment of labial palp with rounded apicomedial projection, its width 1.2 times wider than the base of third segment; third segment symmetrically rounded; ventral surface covered with numerous stout setae accompanied by hair-like setae; surface of second segment covered with hair-like setae only (Fig. 22). Thorax: brown with light brown diffuse spots (Fig. 7). Anterior margins of pro- and mesonotum darker, sometimes pronotum slightly darker than mesonotum. Mesonotum with pair of light spots near base of protoptera and between them. Legs brownish, joints of leg segments dark brown (Fig. 24). Femora with brownish medial area and diffuse light spot near basal and distal margin; outer edge with dense row of long pointed bristles, which are more densely located at the base; inner margin with a regular row of small pointed setae; dorsal surface of femora covered with hairs and small short bluntly pointed setae (Figs 24, 31–32); femoral villopore present. Tibiae brownish or yellowish; small stout setae rare, located evenly along the inner and outer margins (Figs 31, 33); surface covered with bristles and hairs similar in size and shape. Patella-tibial present. Tarsus brownish, distal third and base dark brown; inner margin with small setae and hairs; outer margin with a row of pointed setae (Figs 24, 34); claws brown, with row of 13–14 teeth increasing in length toward the apex and a pair of subapical setae (Figs 25, 34). Lengths (mm) of the leg segments as follows: Foreleg: femur 0.9–1.3; tibia 0.7–1.1; and tarsus 0.5–0.7. Middle leg: femur 1.1–1.2; tibia 0.8–1.0; and tarsus 0.5–0.6. Hind leg: femur 1.1–1.2; tibia 0.8–1.1; and tarsus 0.5. Abdomen: Terga II–III brown, terga VI–VIII darker, lateral area light brown; anterior and posterior margins darker; terga I and IX brownish, posterior margin darker; tergum X brown (Fig. 7); posterior margin of tergum VI with almost regular row of pentagonal bluntly pointed teeth (Figs 28, 36); lateral margins of segments with a row of small pointed setae and sparse hairs (Fig. 27); surface of terga densely covered with numerous semilunar impressions, hairs and rare conical scales (Figs 28, 36). Sterna brownish; sterna V–VII darker; sterna I–VII with pair of small diffuse brown spots near anterior area; sternum IX pale (Fig. 9); along lateral margins with pointed setae and posteriorly more density near tergalii insertions (Fig. 26). Tergalii (abdominal gills) almost oval-shaped; all tergalii white with dark brown margins, without apparent tracheation; margins without spines, with numerous hairs inserted at the base of small teeths. Tergalius I smallest and 1/3 times shorter than corresponding segment (Fig. 37); tergalius II longer than tergalius I, and 1.9 times longer than wide (Fig. 38); tergalii III–V almost equal in length, 1.8 times longer than wide (Fig. 39); tergalius VI smaller than V one (Fig. 40); tergalius VII small, slightly more than tergalius I, and two times longer than wide (Fig. 41). Paraproct with 17–19 marginal pointed teeth like spines of different size; surface of paraproct with a few robust pointed scales (Fig. 30). Cerci brownish at the base and lighter distally; paracercus reduced, with two, three or four segments (Fig. 35). Of the 70 specimens studied, 54 individuals had a three-segmented paracercus, 13 had two, and 3 had four-segmented.

Eggs. General form oval 131–142 μm length and 76–81 μm width (Fig. 42). Chorion wrinkled and shagreened, with small fossae (Fig. 43). One or two small round micropyles located on tops (Fig. 44).

Diagnosis. The imagoes of Baetis (Rhodobaetis) molecularis sp. nov. are distinguishable from the other representatives of the subgenus by the following combination of characters: unistyliger nearly as long as wide and with a rounded bulge on the inside apex of the corner; segment III widened in the distal part and truncated (Fig. 6). The larva of Baetis (Rhodobaetis) molecularis sp. nov. can be distinguished by the following combination of characters: the presence of rare robust setae on pedicel (Figs 10–11); the presence of a row of long narrow distinctly pointed robust setae on scape (Figs 12–13); the absence of spines of external margin of tergalius (Figs 37–41); the presence of a pair of subapical setae on claws (Figs 24, 34); the mean width/length ratio of labrum (1.74); tergalius not elongated, less than twice as long as wide (Fig. 16); canines of both mandibles with outer tooth broadened and almost straight apically (Figs 17–18); posterior margin of terga with almost regular row of pentagonal bluntly pointed teeth (Figs 28, 36); paracercus reduced, with two to four segments.

Distribution. Russian Far East: Chukotka Autonomous District, Kamchatskiy and Khabarovskiy Kray, Magadanskaya, Amurskaya and Jewish Autonomous Oblast’.

Baetis (Rhodobaetis) molecularis sp. nov. is a common species in rivers, streams, and springs of the Kamchatka Peninsula (Figs 45–50). Typical substrate in its habitats is composed mainly of pebbles and rocks of various sizes. Water temperature in the collection periods of larvae and reared imagoes did not exceed 15°С. According to our data, adult emergence period is from late July to mid September.

Etymology. Since the foremost basis for the species delimitation was based on molecular studies, we considered it more correct to name it as molecularis.

Results of DNA barcoding. The final alignment of the COI gene yielded 658 bp for 17 specimens of Baetis (Rhodobaetis) molecularis sp. nov. with 7 haplotypes, one of which was detected in 10 specimens. Total pairwise intraspecific sequence divergence ranged from 0.0000 to 0.0123 (avg 0.0036), which is based on eleven synonymous substitutions.

Interspecific pairwise distances (K2P) between Baetis (Rhodobaetis) molecularis sp. nov. and other 12 GeneBank available species of Rhodobaetis (Fig. 51) ranged from 0.114 to 0.246 (the average value is 0.201). Genetically the closest species to Baetis (Rhodobaetis) molecularis sp. nov. was Baetis foemina (K2P distances – 0.114) from northeastern Canada whereas the Palaearctic species showed higher distances.

The phylogenetic trees reconstructed using Bayesian Inference and Maximum likelihood had varied topology. We use Baetis pentaphyllus Tiunova as outgroup. The BI phylogeny revealed three well-supported clades. The earliest branching clade includes three sequences of B. bicaudatus each of which relates to a different BOLD BIN number (PP = 1, Maximum likelihood bootstrap value percent, ML = 100). The second clade includes two sister species, Baetis foemina and Baetis (Rhodobaetis) molecularis sp. nov. (PP = 0.99, ML = 73). The remaining species of Rhodobaetis were placed to the third clade (PP = 0.97, ML = 68). Baetis silvaticus was sister to Baetis tricaudatus and also placed to the third clade. In Maximum Likelihood tree (not shown) B. bicaudatus was sister to B. foemina and Baetis (Rhodobaetis) molecularis sp. nov. but support of this node was low (ML = 49).