Perla caucasica Guerin-Meneville 1843
Creators: name: Teslenko, Valentina A.
name: Palatov, Dmitry M.
name: Semenchenko, Alexander A.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Plecoptera
Perlidae
Perla
Perla caucasica

description: Perla caucasica Guérin-Méneville, 1843   
Figs. 1‒23  
Guérin-Méneville, 1843:394;  
Pictet, 1841:206−207;  
Klapálek, 1923: 49−50;  
Zhiltzova, 1961:873 (distribution in the Caucasus);  
Zhiltzova, 1964:43 (list of species);  
Zwick, 1978:236 (synonymy proposed);  
 Sivec & Stark, 2002:13, figs. 22−24 (egg illustration, assignation to P. caucasica group, Perla abbreviata Klapálek, 1921 syn. nov., Perla persica Zwick, 1975 syn. nov.);   
Zhiltzova & Cherchesova, 2003:321, figs. 1−2, 5−6 (nymph description and illustration);  
Kazanci, 2008:43 (new records for Turkey);  
Teslenko & Zhiltzova, 2009:126 (key with illustrations copied from Zhiltzova 1961);  
Cherchesova & Zhiltzova, 2013:11, 42, 82, fig. 302 (key imago and larva, with larva illustrations copied from Zhiltzova & Cherchesova, 2003, phenology and distribution);  
 Darilmaz et al., 2016:52 (distribution map in Turkey);   
 Murányi et al., 2021:74 (new records for Azerbaijan);   
 Cherchesova et al., 2023:85 (distribution in North Ossetia).   
 Diagnosis. The male is distinguished by a long mesal field on tergum 9 (Fig. 2). The field expands anteriorly, with lateral longitudinal serrated ridges that are longer than the central ridges of teeth and an anterior part and posterior margin of the mesal field devoid of serrated ridges (Figs. 2, 5). The hemitergal hook is triangular, without projections, narrowed towards the top, apex rounded (Figs. 2, 5‒6). The sac of the penis bears a narrow apical brush, ending in triangles ventrally and dorsally (Figs. 9‒10, C). Ventrally, on the sac, there is an additional barely noticeable ventral brush in the form of a short and narrow stripe, consisting of tiny spines (Figs. 10, D). The female is recognized by the distinctive subgenital plate, with a small rectangular projection with rounded corners posteriorly (Fig. 4). The egg is oval-elongated; collar short, with irregular ribs; rim apex smooth with very slight irregular incisions; chorion is rough with numerous funnel-shaped punctations throughout; micropylar orifices with thin raised rims set in pits (Figs. 11‒15). The larva is distinguished by a wide, V-shaped pale spot on the head without serrations laterally, reaching the clypeus; by the narrow semi-oval pale bands on the pronotum; and by the pilosity of the cerci (Figs. 16‒17, 21‒23).   
 Complimentary description. The color pattern of the head, abdomen, legs, and wings generally corresponds to the original description of Guérin-Méneville (1843), supplemented by Pictet (1841) and Klapálek (1923).   
 Adult habitus. The general body color is brownish-yellow (Fig. 1). The M-line on the head is slightly darkened and clearly defined (Fig. 3). A pair of thin, longitudinal, narrow light spots parallel to the lateral clypeal edges reach the anterior edge of the clypeus; the clypeus has dark lateral margins. The anterior and lateral ocelli are outlined by a black band; lateral margins of the head darkened. The interocellar area is yellow-orange, extending to M-line and compound eyes; the tentorial pits dorsal to the lateral ocelli are light brown; the occiput is darkened (Figs. 1, 3). Pronotum brown; rugosities are pale-grayish, forming an X-shaped pattern (Figs. 1, 3); anterolateral and posterolateral margins darkened; medial stripe brownish, widened to anterior and posterior margins; lateral margins of pronotum bordered by brown stripe, widening posterolaterally; sometimes the lateral edges are bent down and not visible dorsally. The legs and cerci are yellow-brown (Fig. 1). The femur bears a narrow, darkish band close to the outer edge and a black band distally. Tibia darkened basally with an additional narrow brownish band at the base (Fig. 1); tarsi also darkened.Anal gills small and visible only in newly molted females. Each cercal segment slightly darkened distally (Fig. 1).   
 Male. Tergum 8 medially has a membranous furrow and posterolateral humps covered with dense and thick setae (Fig. 2). Tergum 9 with a depressed sclerotized mesal field reaching the end of the posterior margin; the length of the field exceeds its width, expanded anteriorly, covered with longitudinal ridges (10–11) of sclerotized pointed teeth; lateral longitudinal serrated ridges longer than central rows of teeth; devoid of serrated ridges in the anterior part and posterior margin (Figs. 2, 5). Tergum 10 bears hemitergites; the paired triangular hooks narrowed towards the tip, apices rounded, the base of the hook distended, and covered with long setae (Figs. 2, 5‒6). Hemitergites without projections, with an inner edge covered with sensilla basiconica, which is extended at the tip to the front and outer edges (Figs. 2, 5‒6). The artificially everted penis has a tube that is 1.8 times the length of the sac (Fig. 7); the base of the tube is membranous with patches of rounded spine bases laterally; the dorsal tube is covered with densely arranged longitudinal rows of heavy sclerotized serrate sclerites, sometimes changed into scales with small spines (Figs. 7, 9, A‒B); ventrally, the tube at the basal half is weakly sclerotized; in the distal 1/3 there are longitudinal rows of leaf-shaped scales with small spines (Figs. 8, 10). The sac is bulbous, membranous, at the base with lobes (Figs. 7–8); thin pointed brown spines, forming a relatively narrow apical brush, noticeable in the form of a triangle ventrally and dorsally (Figs. 9‒10, D). Ventrally between membranous lobes, closer to the sac base, there is also a barely noticeable ventral brush in the form of a short and narrow stripe consisting of tiny spines; the spine size in the ventral brush is half the size of the apical brush spines (Figs. 10, C).   
 Female. Color and pigmentation are similar for males. The lateral margins of the subgenital plate are weakly pronounced. The subgenital plate has medially a small rectangular projection with rounded corners (Fig. 4).   
 Egg. Oval-elongate, with mean dimensions of 509 x 270 µm (n = 3), and a mushroom-shaped anchor (Fig. 11). Collar short, with irregular ribs extending from rim to shoulders; rim apex smooth with very slight irregular incisions (Figs. 12–13). The chorion is pitted, with numerous funnel-shaped punctations throughout (Fig. 14). Micropylar row is approximately 1/3 length from the anterior pole; orifices with thin raised rims are set in pits (Figs. 12, 15). The shape and the chorion structure agree well with the original description (Sivec & Stark 2002).   
 Larva. Mature larvae were associated with adults and corroborated the results of DNA barcoding. GenBank accession numbers are PP216466 and PP216467 (Table 1). In appearance and color, our specimens generally correspond to the original description of the P. caucasica larva by Zhiltzova & Cherchesova (2003), except for the predominance of brown color and the pattern of the abdomen. Color yellow-brown (Figs. 16–17) with a distinct dark pattern on the head, pronotum, mesonotum, metanotum, and abdomen. Body covered with numerous short dark clothing hairs; bands of erect silky white hairs upward of the epicranial suture on the head and along the median body line, sometimes well pronounced (Fig. 16). Antennae and cerci are yellow-brown. M-line is pale, a wide V-shaped spot expanding to the clypeus is also pale, and the lateral clypeal margins are brown (Figs. 16–17). Head with a large transverse brown band, bounded above by the M-line and below by pale posterior tentorial pits and branches of the epicranial suture; a small triangular spot between the ocelli is pale; epicranial stem and base of the occiput brownish (Figs. 16–17). The transverse occipital fold and the fold running around the eye merge in a regularly curved line. Setation along the occipital fold extends only to behind the eye but not forward along the edge of the flat, expanded side of the head. Mesothoracic supracoxal gills with double trunks. Mandibles (Fig. 18) are heavily sclerotized along a rounded outer margin. The number of teeth and the form of the molar region are asymmetrical between the right and left mandibles. Left mandible ventrally with five pointed heavy sclerotized teeth; bearing three rows of setae; the marginal brush extends from the base of the 4th tooth to the basal third of the mandible; the submarginal setal row stretches from the base of the 3rd tooth to the mandible basal third; the last submarginal setal row prolongs from the base of the first tooth to the mandible base (Fig. 18). Right mandible ventrally with six teeth, the last tooth being small, obtuse-angled, sometimes not developed or poorly visible; marginal brush extending from the base of the 4th tooth to the basal 1/3 of the mandible; the submarginal setal row prolongs from the base of the first tooth to the mandible base (Fig. 18). Lacinia bidentate (Fig. 19) has a large, curved, and strongly sclerotized apical tooth; the subapical tooth is shorter, extending 2/3 of the apical tooth length. The marginal fringe of setae along the inner margin is complete; short median setae are present in a sparse patch; basal setae are sporadic. Galea length reaches half of apical tooth length (Fig. 19).   
Pronotum transverse, approximately the same width as the head, with obtusely rounded anterior corners; lateral margins and posterior angles are evenly rounded (Figs. 16–17). The pronotal fringe is complete with mixed short and relatively long setae. Pronotum with a thin brown stripe along the edges; paired narrow semi-oval pale bands from the anterior corners to the middle of the posterior margin outline an oval brown band; lateral pronotal fields pale (Figs. 16–17). Medial pronotal band brown, widening anteriorly and posteriorly; band surrounded by pale rugosites of an X-shaped pattern; a paired vague S-shaped dark spot extends from the anterior margin to the middle of the pronotum (Figs. 16–17). Mesonotum and metanotum with identical Ψ-shaped brown pattern medially; posteriorly darkly margined; two wide brown bands limiting the wing pad bases; a brown stripe runs along the lateral edge of the wing pads (Figs. 16–17). Legs are yellow; the femur and tibia bear stout, short, acute bristles along the inner and outer edges, and a very dense fringe of long, silky hairs along the outer margins. Hind femur ca. 3.5–3.9 times as long as wide. The femur surface is covered with sparse, short, and irregular red bristles; there is a diffuse brownish spot in the distal half closer to the outer edge, and the distal edge of the femur is also darkened (Figs. 16–17, 20). Tibia with a diffuse, narrow brownish band basally (Figs. 20). Abdomen brown, each tergum with two median and two lateral oval pale spots forming longitudinal rows (Figs. 16–17). The two last terga of the female larvae are somewhat darker than the previous ones (Fig. 16), the posterior margin of sternum 7 is incomplete for female larvae. Anal gills are small. Cerci brown; each cercal circlet with rings of stout brown spines and fine pilosity between spines, tightly pressed to the segment surface (Figs. 21‒23); short fine hairs are the same length as the basal cercal segment length (Fig. 21); towards the middle of the cerci, fine pilosity length decreases (Fig. 22), and on the apical cercal segments, the length of the fine pilosity is about a quarter of the apical segment length (Fig. 23). Long silky colorless hairs are included in the circlet in tufts and form a dorsal longitudinal swimming fringe, well visible especially on the basal cercal segments (Fig. 21); the length and density of long silky hairs also decrease towards the apex (Fig. 21–23). Additionally, a few fine intercalary setae are present on each cercal segment, and their density and length increase from the basal to apical cercal segments (Figs. 21‒23).  
 Material examined. Caucasus. Russia: Republic North Ossetia-Alania: 1♂, 3♀, 1 larva, Prigorodny District, Mairamadag River, Terek R. Basin, altitude 703 m above sea level, 42.993308 N, 44.498150 E, 17.VII.2021, coll. D. Palatov; Krasnodar Kray, 1 larva, District of the City of Sochi, Estosadok, Mzymta River, altitude 622 m above sea level, 43.670007 N, 40.319902 E, 22.VIII.2020, coll. A. Semenchenko; 11♂, 2 larvae, Republic Adygea, Maikop District, Belaya River, vicinities of Guzeripl village, altitude 677 m above sea level, 43.995139 N, 40.135472 E, 7.VII.2023, coll. D. Palatov. Georgia: 3♂, 2♀, 7 larvae, Sukhum District, Kelasuri River, altitude 10 m above sea level, 42.972042 N, 41.067392 E, coll. D. Palatov.   
 DNA barcoding. GenBank accession numbers are PP216462, PP216465‒PP216467, and PP504704.   
 Distribution. Northern slopes of the Greater Caucasus: Adygea, Caucasus Nature Reserve, KarachayCherkessia (Teberda River), North Ossetia-Alania (Terek River Basin); the Black Sea coast and the southern slopes of the Greater Caucasus (the Shakhe, Sochi, Mzymta, Bzyb, Avadhara, and Rioni Rivers); Georgia, Lagodekhi River (Zhiltzova 1964) (Fig. 159). Abkhazia, Kalasuri River. The question of whether P. caucasica is distributed in Turkey, Iran, and Cyprus or whether its range is limited to the watercourses of the Caucasus remains open.   
 Comments. Perla caucasica was originally described by Guérin-Méneville (1843) from the Caucasus without indicating the type locality, data, or sex. The original description was soon supplemented by Pictet (1841). Later, the species was redescribed by Klapálek (1923) from Krasnaya Polyana on the Caucasus, collected in July, which belonged to the German Entomological Museum. The holotype of P. caucasica is lost (Sivec & Stark 2002), but the concept of the species was corrected by Zhiltzova (1964). This species is thought to be widely distributed throughout the Caucasian region, the whole of Anatolia, Cyprus, and the Alborz of Iran (Sivec & Stark 2002; Darilmaz et al. 2016). This is contrary to Teslenko & Zhiltzova (2009) and Cherchesova & Zhiltzova (2013), who considered it an endemic of the Greater Caucasus. This disagreement stems from the contentious synonymy of P. persica and Perla abbreviata. Because of their similar eggs, these species were synonymized under P. caucasica (Sivec & Stark 2002). However, the external and internal male genitalia of P. caucasica and P. persica are distinct (see below).
description: Published as part of Teslenko, Valentina A., Palatov, Dmitry M. & Semenchenko, Alexander A., 2024, Overview of the Caucasian Perla Geoffroy, 1762 (Plecoptera: Perlidae) based on morphological and molecular data with description of two new species, pp. 1-56 in Zootaxa 5507 (1) on pages 3-10, DOI: 10.11646/zootaxa.5507.1.1, http://zenodo.org/record/13747718