Leuctra abkhaziae Teslenko, 2019

Teslenko, Valentina A. & Palatov, Dmitry M., 2019, A new micropterous winter species of Leuctra (Plecoptera: Leuctridae) and little known endemic stoneflies from the Greater Caucasus, Zootaxa 4613 (2), pp. 342-354 : 343-347

Leuctra abkhaziae Teslenko sp. n.

( Figs 1–11 )

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Material examined. Holotype male. Western Georgia. Samegrelo, Zemo-Svaneti, Chkhorotsku municipality, Egris Ridge, Khobi River, upstream, near the Shurubumi cave, 42°38.587 N 42°12.193 E, 0 4.0 2.2017, coll. D. Palatov (FSC EATB FEB RAS). Paratypes: 1 male, 6 females (1 mounted). Abkhazia. Gagra Ridge, Lashipse River, 250 m upstream from the entry into Ritsa Lake, 43°28.529 N 40°33.469 E, 0 8.0 2.2018, coll. D. Palatov.

Description. Body length of males 5.6 mm, females 5.0–7.2 mm. Micropterous, with minute immobile vesti- gial wings, in the form of dark plates on meso and metathorax ( Fig. 9 ). General color brown, sclerotization heavy, body covered with dense pilosity ( Figs. 1–3 , 5–8). Palpi, head, pronotum, meso- and metanotum and legs uniformly brown ( Fig. 1 ). Ocelli vestigial. Prothoracic sternum of the male with sclerites typical of Leuctra; postfurcasternum reduced to a small round sclerite surrounded by pleurae, spinasternum a transverse triangular, semi-oval sclerite, separated from basisternite II ( Fig. 4 ) Male. Terga I–VII simple, darkly sclerotized, except posterior margin on terga V–VII ( Fig. 5 ).

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Tergum VIII anteriorly concave, with a pair of posteromedial darkly sclerotized and widely spaced horn-shaped processes, directed inward and extending to the posterior margin of tergum VIII, posterior margin membranous ( Figs. 5, 7, 8 ). Tergum IX membranous, with distinct antecosta, divided medially for ⅓ of segment width, postero- medial sclerites are paired but separate triangular pigmented spots covered with black setae ( Figs. 5, 7 ). Tergum X with wavy, anteromedian margin, posteromedian margin bears a trapezoid process with bluntly rounded corners ( Figs 6, 8 ). Epiproct small, simple and membranous ( Figs. 5, 6 ). Cerci tear-shaped in dorsal view, each cercus gently bent inward, slightly sclerotized on outer edge and covered with setae; the inner part membranous, apices truncated in lateral view, with vestigial terminal segment ( Figs. 2, 3 5–8 ). Paraprocts strong, heavily sclerotized ( Fig. 3 ); styles slightly shorter than specilla ( Fig. 7 ). Specilla gently narrowed to the apex and ending in a round point in dorsal view ( Figs. 6–8 ). Sternum IX with U-shaped unsclerotized area, vesicle absent ( Figs. 2, 3 , 8) Female. Terga II–X completely sclerotized ( Fig. 9 ). Sternum VII convex, large, ventral sclerite almost rectan- gular with weakly rounded posteromedial margin, sometimes overlapping the anterior margin of sternum VIII covering the base of subgenital plate ( Fig. 10 ). Sternum VIII with a triangular subgenital plate, ending slightly before the posterior margin of sternite.Anterolaterally from the wide unpigmented base of the subgenital plate stands a pair of small sclerotized spots. The convergent sides of the plate bear a pair of elongate-oval sclerites together forming a V-shape. Caudally from the plate the pleurites reach far to the ventral side, the extension anteriorly with an elongate swelling, caudally it is drawn out into a sharp point ( Fig. 10 ). Sternum IX with concave anterior margin ( Fig. 10 ). Seminal receptacle spheroid with a ring- shaped spermathecal sclerite which ends in a pair of lateral arms joined to each other by a sclerotized arch ( Fig. 11 ).

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Diagnosis. Micropterous in both sexes. Terga I–VII of male simple; tergum VIII with a pair of posteromedial heavily sclerotized widely spaced horn-shaped processes, directed inward; tergum X wavy along anteromedian margin, posteromedian margin trapezoid with bluntly rounded corners. Epiproct membranous, small and oval; cerci tear-shaped; styles slightly shorter than specilla. Ventral vesicle absent. Female subgenital plate triangular with unpigmented base delimited anterolaterally by a pair of small sclerotized spots and laterally by paired of elongateoval sclerites; a pair of sclerites extending anteriorly with an elongate swelling armed the subgenital plate laterally. Seminal receptacle spheroid enclosing a ring-shaped spermathecal sclerite with a pair of lateral arms Affinities. The extent of sclerotization of the male abdominal terga, the shape of tergal processes, and structure of epiproct, L. abkhaziae may be assigned to the prima species subgroup within the hippopus species group according to Ravizza & Vin ҫon (1998) and Ravizza (2002). Males of the Balkanian species, L. olympia Aubert, 1956 and L. istenicae have similar horn-shaped and widely spaced processes on tergum VIII. In L. olympia , the processes are short, curved laterally, directed perpendicular to the body axis, and between the tergal processes is a rounded bulbous protrusion. In L. istenicae the tergal processes are long, extended to the middle of tergum IX, whereas in L. abkhaziae , the tergal processes reach the posterior margin of tergum VIII and both species lack a protrusion between the tergal processes. The posteromedial sclerite on tergum IX is semi-oval with diffuse apex in L. olympia , the same sclerite of L. abkhaziae and L. istenicae appears as a pair of pigmented triangular spots, which are disconnected at their base and covered with black setae. Leuctra abkhazica differs from both above mentioned and other species in the specific shape of tergum X, which is trapezoid posteromedially with bluntly rounded corners. The females of the three species are only a generally similar in having triangular subgenital plates with a bilobed posterior margin but the internal genitalia differ in the details. The spermatheca of L. abkhaziae has a strongly sclerotized central arch and caudally connected arms, similar to some members of the prima sub-group. The seminal receptacle of L. istenicae has not yet been described.

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Adults of L. olympia are active in early to mid-spring, whereas L. istenicae and L. abkhaziae adults emerge in autumn and winter. The three species are geographically distributed within a relatively small area in different mountain ranges. Leuctra olympia is endemic to the western and southern regions of the Balkans ( Muranyi et al. 2014); L. istenica is relatively common in springs in the Pohorje Mountains of the Alps of Slovenia ( Sivec 1982); and L. abkhaziae is associated with the Egris and Gagra Ridges of the Greater Caucasus Mountain Range in Abkhazia and western Georgia.

Distribution. One male of L. abkhaziae was collected with adults of Brachyptera transcaucasica Zhiltzova, 1956 and a female of L. fusca ( Linnaeus, 1758) in the Khobi River near the Shurubumi Cave, Samegrelo, Zemo- Svaneti, Chkhorotsku, western Georgia, in February 2017 ( Figs. 12, 13 ). The Khobi River drains the southern portion of the Egris Ridge (Greater Caucasus), the Colchis Lowland into the Black Sea. At the type locality, the Khobi River flows into a low mountain valley at an altitude 330 m. a.s.l., in a sharp, but low canyon ( Fig. 13 ), width of river is 30 m, water current 0.3–1.0 m/s. On February 2018, one male and six females of L. abkhaziae were collected 250 m upstream from the mouth of the Lashipse River, Gagra Ridge (Greater Caucasus), Abkhazia ( Fig. 12 ). The Lashipse River is about 10 m wide, speed of flow 0.6–0.7 m /s. The river flows into a lake, Ritsa Lake of glacialtectonic origin, where the average water temperature is + 3.8 °C in February ( Figs. 14, 15 ). Ritza Lake is located at an altitude of 950 m above sea level in a deep mountain fir valley of the Lashipse River. Adults of L. abkhaziae were walking on the snow with adults of Capnia nigra ( Pictet, 1833) . A larva of Capnopsis shilleri archaica Zwick, 1984 was also collected from the Lashipse River.

Leuctra abkhaziae appears to be a rare, rheophilic species that inhabits cold water streams at an altitude not exceeding 1,000 m.a.s.l. on the southern edge of the Greater Caucasus Mountain Range in Abkhazia and western Georgia.

Etymology. This species is named after the Autonomous Republic of Abkhazia. The specific name is considered feminine.

Two other rare stonefly species on different stages of larval development were found in streams of Abkhazia and on the Black Sea coast during winter and spring 2018. The description of larvae of two Caucasian endemics species is given below.

Figures

FIGURES 1–4. Male of Leuctra abkhaziae sp. n. 1. Habitus, lateral. 2. Abdominal tip, lateral. 3. Abdominal tip, ventral. 4. Pro-, meso- and metathorax.

FIGURES 5–8. Male of Leuctra abkhaziae sp. n. 5. Abdominal tip, III–X terga, dorsal. 6. Abdominal tip, IX–X terga, epi- proct, styles, cerci, dorsal. 7. Abdominal tip, tergum VIII with horn-shaped processes; tergum IX with posteromedial sclerite; tergum X, cerci, dorsal, styles and specilla, ventral. 8. Abdominal tip, VIII–X terga, lateral.

FIGURES 9–11. Female of Leuctra abkhaziae sp. n. 9. Habitus, dorsal. 10. Subgenital plate, ventral. 11. Spermatheca, cleared, mounted ventral.

FIGURES 12–15. 12. Map of the collecting sites of Leuctra abkhaziae sp. n. in Abkhazia and Western Georgia (black dot). 13. Collecting site of Leuctra abkhaziae sp. n., in the Khobi River (the West Georgia). 14, 15. Collecting sites of Leuctra abkhaziae sp. n., in the Lashipse River (Abkhazia, Ritza Lake Basin). Photo by D. Palatov.