Isoperla vjosae, Graf & Pauls & Vitecek, 2018

Graf, Wolfram, Pauls, Steffen U. & Vitecek, Simon, 2018, Isoperla vjosae sp. n., a new species of the Isoperla tripartita group from Albania (Plecoptera: Perlodidae), Zootaxa 4370 (2), pp. 171-179 : 174-178

Isoperla vjosae sp. nov. Graf & Vitecek

Figures 2–14

Type material. Holotype male: ALBANIA, Vjosa River near the village of Kutë; 40.4726°N 19.749°E; 25.iv.2017, leg. Graf (specimen identifier: Itri 0301M [ SMF]) . Paratypes: 21 males, 7 females, 11 larvae, 2 exuviae; same collection data (1 female, 1 larva, SMF; all other specimens currently in coll. Graf – 2 males, 2 females and 2 larvae will be transferred to the Biologiezentrum Linz , Linz, Austria) .

Additional material: 1 male; ALBANIA, Vjosa River near the village of Kutë; 40.4726°N 19.749°E; 14.vi.2017, leg. Graf, in coll. Graf.

DiagnoSiS. Ventral lobe of the penis with partitioned medial penial armature comprising a distal and a proximal part, both subdivided into diverging, elongated left and right portions. Scales of the penial armature spike-like. Lateral penial armatures small.

In all other species of the tripartita group either the distal or the proximal part of the medial ventral lobe penial armature forms a continuous band of scales.

DeSCription. Medium to large species, macropterous. Body length: holotype male 9.5 mm, paratype female 11.0 mm; forewing length: holotype male 11.0 mm, paratype female 14.0 mm.

Adult habituS: General colour yellowish but head and pronotum mostly yellow with dark brown markings; body and legs pilose. Ground colour of the head yellow, with rectangular brown marking connecting the three ocelli, leaving a pale subrhombic area between them; with brownish band extending rostrally from the M-line; M-line rather distinct, yellowish ( Figs. 2, 3 ); tentorial callosities inconspicuous, yellow; occiput with even surface, in some specimens with two dark brown semicircular areas meeting at the coronal suture. Eyes as large as the area delimited by the three ocelli. Scape dorsally dark brown; pedicel and the following ten antennomeres dorsally creamy; scape, pedicel and basal antennomeres ventrally yellowish; distal part of the antenna brown. Palpi cream-coloured. Pronotum yellow, rectangular, with angled edges; areas with textured surface dark brown, the surrounding area smooth and cream-coloured, anterior and posterior lines located distally and anteriorly of areas with textured surface dark brown. Mesonotum dark brown but yellow anteriorly, metanotum dark brown. Wings translucent yellowish; venation dark brown. Ventral surface of thorax pale, meso- and metabasisternum off-whitish, furcasternites pale, furcal pits inconspicuous ( Fig. 4 ). Femora brown dorsally and ventrally. Tibiae uniformly brown; tarsi dark brown.

Male abdomen: Tergites I-IX dorsally with prominent broad dark posterior margin; tergite X uniformly yellow. Tergite I-IV dorsally entirely brown; tergites IV-IX subsequently getting more yellowish mediolaterally; tergites VIII to IX dorsally with brown longitudinal band ( Fig. 5 ). Tergites I–IX dorsally with transverse row of four pigmented spots; laterally with two to three spots; all spots with pale centre. Ventral surface of abdomen pale. Sternite VIII vesicle brownish, slightly longer than wide, its posterior margin evenly rounded; nearly as long as half the segment’s length; posterior margin of sternite VIII with additional spines ( Fig. 6 ). Sternite IX yellowish, paraprocts yellowish; cerci yellowish with brown ring at terminal end of each segment ( Fig. 5 ).

PeniS (everted): Medial penial armature on ventral surface of penis divided into a distal and a proximal part, both coloured; distal armature located on medial lobe adjacent to ventral lobe, divided into suboval left and right portions, length of each portion 290-300 µm, width 100-110 µm; proximal armature located on central part of ventral lobe, divided by 85-93 µm gap lacking large coloured scales into left and right portions, length of each portion 250-260 µm, width 100-125 µm; both distal and proximal armatures proximally diverging, usually forming an upturned ‘V’ ( Fig. 7, 8 ). Scales of medial penial armature spike-like and straight, scales of proximal part usually longer: length of distal part scales 44-58 µm, width 4-7µm; length of proximal part scales 97-138 µm, width comparable to distal part scales. Lateral penial armatures small and indistinct.

Female abdomen: All tergites uniformly dark brown. Sternites and cerci pale yellow. Subgenital plate evenly rounded, covering half of sternite VIII and the anterior third of sternite IX ( Fig. 9 ).

Egg: unknown. No mature eggs were available for study.

Mature larva: Body length 10.5-11.2 mm. General colour pale yellow with dark markings on head and abdomen ( Fig. 10 ); body and legs pilose, pilosity as typical for the genus; pronotal, posterior tergal and cercal fringes relatively long and acute; swimming hairs present on femora, tibiae and tarsi, cerci without dorsal hair fringe. Ground colour of the head pale yellow with dark brown transversal mask connecting eyes and ocelli and extending rostrally ( Fig. 11 ); M-line indistinct; occiput with row of lateral occipital setae, lateral occipital setae medially thinning. Eyes well-developed, not reduced. Scape, pedicel and antennomeres light brown, mouthparts light brown. Lacinia bidentate, triangular, inner lacinial margin with seven to eight stout setae and a row of short thin setae below subapical tooth ( Fig. 14 ). Pronotum rounded, pale with obscure darker patterns laterally; pronotal anterior and posterior margin slightly darker, interrupted medially; pronotal setal fringe with predominantly short bristles at anterior and lateral margin, at posterior margin with additional large setae. Prosternum inconspicuous. Mesonotum and metanotum both pale with a brownish line anteriorly and posteriorly; wingpads whitish, with brown spots proximally. Meso- and metasternum pale, furcasternites and furcal pits slightly darker. Legs pale. Abdominal tergites I and II dorsally pale yellow with three longitudinal brown bands, abdominal tergites III to VI dorsally entirely brown, abdominal tergites VII to X dorsally with expanding pale areas leaving some brown markings medially and laterally. Ventral surface of abdomen pale yellow proximally, continually darkens distally. Paraprocts and cerci uniform pale; setation on distal section of cercal segments consisting of rather uniform setae with larger single dorsomedial and ventromedial setae, from cercal segment XIV with dense lateral fringe of swimming hairs.

Etymology. Named after the Vjosa River; Latinised Shqip (Albanian) “Vjosë” to genitive “ vjosae ” — «belonging to the river Vjosa».

AffinitieS. The new species is a member of the I. tripartita group based on characters defined by Consiglio (1967) and Murányi (2011). The aedeagus of the new species possesses the typical divided medial penial armature located on the ventral lobe of the penis; this armature may be divided into a distal and proximal portion where usually one of these is at least partly divided into a left and a right half. Lateral penial armatures are usually present. The following species are currently considered members of this group: Isoperla tripartita tripartita ; I. tripartita recta Zwick, 1978 ; I. autumnalis , I. illyrica Tabacaru, 1971 ; I. obliqua Zwick, 1978 ; and I. pesici ( Zwick 1978, Murányi 2011).

Following Murányi (2011) and Zwick (1978, fig. 72), I. vjosae can be easily separated from all taxa of this group except I. illyrica by the distinct medial gap between the proximal medial armatures ( Figs. 7, 8 ) that are fused in I. tripartita tripartita (Fig. 15), I. tripartita recta , I. obliqua , I. pesici and I. autumnalis . In I. pesici , the medial section of the proximal medial armature can be constricted in some populations, but is never as clearly separated as in I. vjosae sp. n. (pers. comm. D. Murányi). In I. illyrica the distal medial armatures are not divided while in I. vjosae sp. n. left and right portions of both distal and proximal parts are well separated ( Zwick 1978; Abb. 72a).

Additionally the new species differs from I. tripartita recta by having divergent left and right portions of the distal medial penial armature ( Figs. 7, 8 ) instead of parallel ones. Isoperla obliqua and I. pesici have teardropshaped or rounded distal medial penial armatures, respectively (Fig. 18), which are elongated in I. vjosae Sp. nov. ( Fig. 8 ). Additionally, I. autumnalis has an uncoloured and undivided proximal medial penial armature.

The colour patterns of both adults and larvae of the new species seem to deviate from colour patterns of other species of the tripartita group. However, colouration may vary specifically (e.g., as observed in I. tripartita tripartita ( Illies 1955, Murányi et al. 2011), and we observed some variation in both larvae and adults although we did not extensively study this character set. Yet, overlapping colouration patterns within species might be indicative of on-going speciation processes, and could potentially be used as additional character to discern lineages within the tripartita group.

ECology and diStribution. Adults of I. vjosae were collected along the banks of the Vjosa River ( Fig. 19 ), a large, wide, shifting gravel, low altitude (50 m a.s.l) river, a habitat atypical for other tripartita group species. Usually, taxa of this group occur in smaller submontane and montane streams and brooks ( Murányi 2011, Murányi et al. 2016). Possibly, the high river-bedload dynamics of the Vjosa River create habitat conditions that are similar to conditions prevalent at higher elevations in regard to dissolved oxygen, sediment particle size distribution and bedload. As other members of the genus Isoperla , larvae of I. vjosae are likely predaceous. At the type locality, I.

vjosae occurred sympatrically with the plecopterans Marthamea vitripennis (Burmeister) , Eoperla ochracea (Kolbe) , Xanthoperla apicalis (Newman) , Chloroperla tripunctata (Scopoli) , Perlodes cf. floridus, Leuctra cf. leptogaster and Leuctra fusca (Linnaeus) , the Trichoptera species Rhyacophila diakoftensis Malicky, Agapetus laniger Pictet, Allotrichia vilnensis Raciecka , Oxyethira falcata Morton , Hydroptila simulans Mosely , H. angustata Mosely , H. brissaga Malicky , Stactobiella risi Felber , Adicella syriaca Ulmer and among others, the ephemeropteran, Prosopistoma pennigerum Müller - a community that clearly reflects a highly dynamic habitat. Many of these species are endangered or extirpated in Central Europe due to their reliance on no longer existing highly dynamic gravel reaches of large rivers. Despite repeated sampling efforts, the species could not be collected in July, September or October, indicating a short flight period in early summer.

RemarKS on ConServation. The type locality of this species has been selected as a site for a dam and large hydropower plant. Construction of this hydropower plant will likely extirpate the characteristic benthic community currently inhabiting the river.

Figures

FIGURE 14. Isoperla vjosae sp. nov., lacinia; FIGURES 15–17. Isoperla tripartita tripartita; 15: medial penial armatUres; 16: male meso- and metasternUm; 17: vesicle of sternite VIII; FIGURE 18. Isoperla pesici, medial penial armatUres.Scale bar represents 500 µm.

FIGURE 19. Sampling locality of the type material series at the river Vjosa near KUtë.Copyrighted image byGregor ŠUbic.

FIGURES 2–13: Isoperla vjosae sp. nov.; 2: male habitUs; 3: male head and pronotUm, dorsal; 4: male meso- and metasternUm; 5: male abdominal tergites; 6: vesicle of sternite VIII; 7: everted male copUlatory organ with medial penial armatUres; 8: distal and proximal medial armatUres, arrow=lateral penial armatUres; 9: female sUbgenital plate; 10: larval habitUs; 11: larval headand pronotUm; 12:larval meso-and metathorax; 13: larval abdominal tergites.Scale bar represents 500 µm.