Perla palatovi sp. nov. Teslenko & Semenchenko

Figs. 128−156

Diagnosis. Tergum 9 of males is distinguished by the arrangement of serrated ridges on the mesal field that are relatively short and do not reach the posterior margin (Figs. 133, 137). The hemitergal hooks are strong, with a weak notch in the apical third along the inner edge; the apex is rectangular and rounded (Figs. 132−133, 137). The tube of the penis is 1.8 times longer than the sac. The membranous sac is rough, covered with tufts of tiny setae associated with patches, and arranged in concentric lines following the shape of the lobes (Figs. 139−140, B, D). The apical brush is narrow and pointed ventrally (Figs. 138, 140, D). The egg has a short, slightly ribbed collar (Fig. 144). The chorion surface is rough and pitted with follicle hexagonal cell impressions, weakly separated from each other; the cell floor is without a central depression; and the number of central pores ranges from one to four (Fig. 146). Micropylar orifices lack rims (Fig. 147). The larva is distinguished by pale bands along the lateral margins of the pronotum; the width of the pale bands is wider than the semi-oval dark band; a paired dark S-shaped spot extends from the anterior margin to the middle of the pronotum (Figs. 148−149).

Adult habitus. Body length: males 13.0−14.0 mm (n=6), females 17.3−22.7 mm (n=7); length of forewing: males 12.8−13.7 mm; females 17.4−20.5 mm; wingspan: males 27.4−29.3 mm; females 37.5−43.5 mm. Head and pronotum are dorsally grayish-yellow with dark brown spots; mesonotum and metanotum are dark brown, especially in females; the three small, pale spots on the prescutum and scutum form a triangle; the abdomen is grayish-yellow (Figs. 128−129). The wings are yellowish with dark brown veins (Figs. 128−129). Antennae and palpi are yellowgrey. The M-line on the head is brownish, connected with a triangular brownish spot on the clypeus; the anterior margin and lateral edges of the clypeus are dark brown, clearly contrasting with a pair of transverse small oval pale spots between the clypeal edges and the triangular spot on the clypeus (Figs. 128−131). Frontal tentorial pits are brownish (Fig. 130). The interocellar area has an X-shaped dark brown spot; the upper branches reach the base of the M-line; the lower branches attain the lateral ocelli; and between the lateral ocelli is a triangular yellowish blurred spot limited basally by a brown stripe of the epicranial suture (Figs. 130−131). A pair of drop-shaped, bright yellow spots are located between the posterior ocelli and the compound eyes; the tentorial pits are brownish (Fig. 131). The posterior occipital fold is indicated by a thin light stripe, limited above and below by a narrowdarkened band interrupted in the area of the epicranial stem; the epicranial stem darkened (Figs. 130−131). A pair of transversely oblique dark bands extends from the base of the occiput to the posterior edge of the compound eyes. Pronotum as wide as head with eyes, slightly narrowing posteriorly, posterolateral margins rounded; anterior margin arcuate, darkened; medial stripe dark brown, widened to anterior and posterior margins, wider at the anterior margin than at the posterior one; pronotal posterior margin darkened; lateral pronotal margins bordered by a dark brown stripe, widening posterolaterally; sometimes the lateral edges are bent down and not visible dorsally (Figs. 117−118). Pronotal rugosities are grayish-yellow, darkly contoured, and form an X-shaped pattern (Figs. 130‒131); in the posterior third, dark rugosities in the form of narrow paired transverse short stripes reach the lateral pronotal margins (Figs. 130−131). The legs and cerci are grayish-brown. Femur with a dark spot basally and a narrow light stripe dorsally; the distal part darkened; tibia darkened at base with a narrow brownish band in the basal ⅕ (Figs. 115−117); cowl also darkened.Anal gills are very small, noticeable in newly molted specimens. Cerci are bicolored, each segment with a narrow yellowish ring basally and a thick grayish-yellow band apically (Fig. 128).

Male. Tergum 8 is medially depressed with a central membranous furrow; posterolateral humps are covered with dense and thick setae; along the posterior margin of the furrow, setae are short and sparse (Fig. 132). Tergum 9 has a sclerotized mesal field; the width is slightly greater than or equal to the length (Figs. 132−133, 137). The mesal field bears sharp, heavy sclerotized teeth that merge into long and short longitudinal serrated ridges (8−14), located in the middle of the mesal field, and do not reach the posterior margin (Figs. 133, 137). Tergum 10 has strong hemitergal hooks (cleared) with a weak notch in the distal third of the inner edge laterally (Figs. 134, 137); in dorsal view, the notch on the hook corresponds to a shallow depression in the side (Fig. 132). The apex of the hook is rectangular and rounded (Fig. 134); in its natural state, dorsally, the tip is slightly slanted (Fig. 132). Sensilla basiconica covers the inner side of the hook from top to outer edge; the base of the hook is rounded and covered with long setae (Figs. 132−134, 137). The artificially everted penis has a tube that is 1.8 times the length of the sac; the dorsal tube is covered with densely arranged longitudinal rows of serrate sclerites, sometimes with small spines; the shape of sclerites in different parts of the tube varies from polygonal to oval elongated; the tube is membranous basally with paired patches of rounded spine bases laterally (Figs. 137−140, A, C). The sac is bulbous and membranous at the base, with two lateral lobes and folds that increase its width (Figs. 139−140); thin pointed brown spines are present, forming a relatively narrow apical brush that is pointed ventrally (Figs. 139−140, B). The membranous sac is rough and covered with tufts of tiny setae arranged in concentric lines following the shape of the lobes (Figs 139−140, B, D).

Female. Sternum 8 has a subgenital plate, occupying almost half of the sternum width, with two small triangular lobes posteromedially. The lobes projecting slightly beyond the anterior margin of sternum 9 are covered with rufous setae (Figs. 135−136).

Egg. Elongate and oval, with mean dimensions of 435 × 272 μm (n = 6), with a short collar with the same diameter at the rim and the base; the rim is weakly ribbed (Figs. 141−144). The neck is not constricted.A mushroom-shaped anchor plate is present on some eggs and covered with globular bodies concentrated in small groups (Figs. 142, 145). The chorion surface is rough and pitted; the chorion is covered throughout with follicle hexagonal cell impressions; hexagonal cells with differences in cell widths; cells separated from adjacent ones by poorly expressed boundaries; the cell floor without a central depression with one or four pores (Figs. 144, 146). A ring of micropyles is located ca. 1/3 of the egg length from the anterior pole, the micropylar orifices are without rims (Figs. 141−142, 147).

Larva. Mature males of medium size, length 12.2−12.4 mm (n=3), antennae 9.5 mm, and cerci greater than 8.8 mm contain more than 36 segments. The color is generally pale, yellow-brown in dorsal view (Figs. 148−149), with a distinct dark pattern on the head, pronotum, mesonotum, and metanotum, but with a less distinct pattern on the abdomen. The ventral body side is yellow-brownish. Body covered with short dark clothing hairs, with a dorsomesal band of erect silky white setae more pronounced on the last abdominal terga (Figs. 148−149). Antennae and cerci are yellow-brown. Clypeus on head basally with paired dark and wide V-shaped spots, outlining branches of yellow M-line from above. Head with a large transverse dark spot, vaguely resembling a pilot's badge with truncated “wings” not extending beyond epicranial arms; the spot limits the pale M-line from below extending from the anterior ocellus to the posterior ocelli; a small triangular spot between the ocelli darkened; epicranial stem and occiput edge also darkened (Figs. 148−149). The occipital ridge is distinct and complete; short spines are arranged in the medial part of the fold; along the postocular crest, spines are noticeably longer and pointed. Mandibles (Fig. 153) are typical for Perla: heavily sclerotized, with a rounded outer margin; left mandible with five pointed teeth and two medial rows of setae on the molar area; the marginal row of setae extends from the base of the 4th tooth to the basal third of the mandible; right mandible with six pointed teeth; single medial setal row extends from the base of the first tooth to the base of the mandible; the configuration of the marginal setal row is the same as that of the left mandible. Lacinia bidentate with a large, heavily sclerotized, and strongly curved apical tooth (Fig. 152). The subapical tooth is shorter; the length does not exceed 2/3 of the apical tooth length. The marginal fringe of setae along the inner margin is complete; a tuft of long and dense setae of marginal fringe is clearly visible below the subapical tooth. Galea length reaches 1/2 of subapical tooth length (Fig. 152).

Pronotum transverse, not wider than the head, with obtusely rounded anterior corners; lateral margins and posterior angles are evenly rounded (Figs. 148−149). The pronotal fringe is complete with mixed short and relatively long setae. The pronotum has a thin brown stripe along the edge; paired semi-oval pale bands outline a full (or incomplete, open anterolaterally) oval brown band on the lateral pronotal fields (Figs. 148−149). An oval brown band is narrower than semi-oval pale bands, especially in the anterior 1/3. The central pronotal field is yellow with a brown median band narrowed anteriorly and markedly widened posteriorly; a paired vague S-shaped dark spot extends from the anterior margin to the middle of the pronotum (Figs. 148−149). Mesonotum and metanotum with an identical Ψ-shaped dark pattern medially, posterior margin darkly margined; two wide dark bands limiting the wing pads; a narrow dark stripe runs along the lateral edge of the wing pads. Legs are yellow and covered with dark closing hairs (Figs. 148−149). 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 (Fig. 150). The femur is covered with sparse, short, and irregular red bristles; in the distal half closer to the outer edge, with a darkened small and almost oval spot, the distal edge of the femur is also darkened (Fig. 150). Hind femur ca. 3.3−3.6 times as long as wide. Tibia has a diffuse, narrow brownish band basally. The pattern on the abdomen is indistinct; the dark closing hairs are well-marked; the terga are mainly yellowish with a dark median and two lateral longitudinal bands; the lateral dark bands on terga 4−10 are triangular, extending to the anterior margin (Figs. 148−149). The posterior terga margins bear acute bristles that are mostly short, with one or two relatively long setae (Fig. 151). Anal gills are small (Figs. 148−149). Cerci are yellow, and no less than 36 segmented with striking rings of dark spines (Figs. 148−149). Fine pilosity between dark spines is tightly pressed to the segment surface (Figs. 154−156); short fine hairs have the same length as the length of the basal cercal segment; towards the middle of the cerci, fine pilosity length decreases; and on the apical cercal segments, the length of the fine pilosity is slightly>1/3 of the segment length (Fig. 156). Long silky fine colorless hairs are included in the circlet in tufts (no more than 8 in each) and form a dorsal longitudinal fringe, especially on the basal segments (Fig. 154); the length and density of long silky hairs also decrease towards the apex (Figs. 155‒156).

DNA barcoding. GenBank accession numbers are PP216454‒PP216456 and PP236723.

Material examined. Holotype male (FSC EATB FEB RAS). Caucasus. Russia, Krasnodar Kray: Gelendzhik District, Papay River, 2.5 km below Novosadovy farm, Pshada River Basin, collected by a light trap, 44.569305 N, 38.42889 E, 08.06.2021, coll. D. Palatov ; Paratypes: 3♂, 5♀, 2 larvae (FSC EATB FEB RAS), same place and data; 2♂, 2♀, 1 larva, 3 exuvia, Tuapse District, Shapsukho River, downstream, 3 km from the confluence with the Black Sea, near Tenginka village, altitude 22 m above sea level, 44.337647, N 38.786211 E, 22.06.2022, coll. D. Palatov.

Distribution. North Caucasus. North-eastern coast of the Black Sea. Russia. Krasnodar Kray. Gelendzhik and Tuapse Districts. The species was found in small foothill rivers along the Black Sea coast (Figs. 157−158), flowing through low-mountain forest valleys 10−12 m wide with a pebble and rocky bottom and a current up to 0.7 m /s.

Etymology. The species is named in honor of Dr. Dmitry M. Palatov, who collected type material for a new species in the Caucasus as well as other very interesting stonefly material in the Caucasus, Central Asia, and the Middle East.

Remarks. Perla palatovi sp. nov. bears some similarity to the P. pallida species complex. The most noticeable resemblance between the eggs of P. palatovi sp. nov. was observed with Type 2 and Type 3 in the shape of the collar (Sivec & Stark 2002). The collar is short, with the same diameter at the rim and base; the neck is not constricted but slightly ribbed. The main differences between P. palatovi sp. nov. and any type of egg consist of punctured hexagonal chorion cells, the boundaries between which are poorly expressed. The P. palatovi sp. nov. hexagonal floors lack depressions and have four pores; the pores and punctuation of the hexagonal floors are uniform. The larvae of P. palatovi sp. nov. are very similar to the patterning of P. caucasica larvae described by Zhiltzova & Cherchesova (2003). There are differences in the dark closing hairs, which are denser and more pronounced in P. caucasica; in P. palatovi sp. nov., the pronotal and especially abdominal patterns are lighter and less distinct. For the pronotum of P. palatovi sp. nov. larvae, the width of the oval dark bands is narrower than the width of the semi-oval pale bands, and vice versa in P. caucasica, where a paired S-shaped dark spot extends from the anterior margin to the middle of the pronotum. On P. caucasica, the S-shaped dark spot sometimes continues to the posterior margin. The darkish spot on the P. palatovi sp. nov. femur is fuzzy, small, and almost oval.