Petrobiellus iturupiensis Kaplin, 2025

Petrobiellus iturupiensis Kaplin , sp. n.

https://zoobank.org/NomenclaturalActs/ 30FB6761-0D7F-42E5-B0E8-8F71462BDF5B

Figs 1–17 View Figs 1–8 View Figs 9–15 View Figs 16–20

MATERIAL. Holotype – ♂, Russia: Kuril Islands , Iturup, 45°02′ N, 147°37′ E, coast of the island, under the stones, 31.VII 1997, leg. A. S. Lelej ( ARIPP) (in slides). Paratypes – 2 ♀, same locality, data and collector as for holotype (in slides) GoogleMaps .

DESCRIPTION. Body length (not including antennae and caudal filament): male and female 9.5–10 mm. Body width: male and female 3.0– 3.4 mm. Antennae are damaged. Cerci length: female 5.0– 5.2 mm, male 6.0 mm. Ovipositor length: 3.5–4.4 mm.

General body color (in ethanol) whitish. Frons, gena, occiput, most part of clypeus, with the exception of its apex, scapus and pedicellus of antennae, labrum, mandibles, maxillae, first palpomere, bases and apices of 2nd–4th, bases of 5th and 6th palpomeres of maxillary palps; labium, with the exception of labial palps; legs, base of caudal filament with violetbrown pigment. Head is most pigmented. Antennae, maxillary and labial palps, legs, styli of legs and abdominal coxites without scales. Scales on body dorsal side, caudal filament and cerci are dark brown; on ventral side they are brown and uniformly colored.

All annuli of antennal flagellum with one row of setae. Distal chains of flagellum are divided into 12–13 annuli. Clypeus of male and female with numerous thin long and mediumlength setae.

Cercus approximately 0.50–0.53 (female), or about 0.63 (male) body length, including about 20–22 articles. Apex of cerci with one relatively long and other short lateral spikes ( Fig. 1 View Figs 1–8 ). About 16 distal articles of cerci with four rows of scales. All articles of cerci, excluding their apical article, also with 2–4 supporting hyaline spines. Epiproct at the base of caudal filament in male and female is triangular, its length is almost equal to its width ( Fig. 2 View Figs 1–8 ).

Compound eyes dark (in ethanol). Ratio of length to width of compound eye in male and females 1.09–1.10; ratio of length of contact line to length of eye about 0.43–0.45 in both sexes. Paired ocelli pistil-shaped, dark brown with inconspicuous white bordering; ratio of width to length of ocellus in male about 3.5, in female 2.9–3.0 ( Fig. 3 View Figs 1–8 ). Frons slightly swollen between the paired ocelli. Inner parts of the paired ocelli noticeably protruding forward. The distance between the inner margins of the paired ocelli is about 0.19–0.21, and between their outer margins 0.93–0.96 the total width of the compound eyes in both sexes.

Apical palpomere of maxillary palp 0.58–0.59 (male) or 0.80–0.81 (female) times as long as preceding one; ratio of lengths of 5th and 4th palpomeres 1.06–1.09 and 1.10–1.13, respectively ( Figs 4, 5 View Figs 1–8 ). Dorsal surface of 7th, 6th and 5th palpomeres of maxillary palp with 18–21, 14–16 and 3–4 (female) or 12, 9–10 and 2 (male) hyaline spines, respectively; relatively short and thickened in male. Ventral surface of 2nd–7th palpomeres of male maxillary palp with numerous dark, shortened setae, absent on female palps. Apex of 7th palpomere of maxillary palp rounded in male and pointed in female.

Apical palpomere of the labial palp noticeable (male) or slightly (female) curved inside. Ratio of its length to width about 3.7 (male) or 3.0 (female) ( Figs 6, 7 View Figs 1–8 ). Distal surface of this palpomere with 15–16 large sensory cones in both sexes. Mandibles with two (female) or three (male) distal teeth ( Figs 8 View Figs 1–8 , 9 View Figs 9–15 ).

Table 1

Ratios of length to width of main leg segments of Petrobiellus iturupiensis sp. n.

Femora of male and female slightly widened. Ratios of length to width of femur, tibia and tarsus as shown in Table 1. Fore legs, including tarsus, tibia, femur, trochanter and coxa, shorter than middle and hind legs, respectively, 1.05 and 1.16 times in male and 1.07 and 1.20 times in female. Ventral surface of tarsi of all legs in female, middle and hind legs in male; middle and hind tibiae and femora with thickened hyaline spine-like chaetae of medium length in both sexes (Table 2, Figs 10, 11 View Figs 9–15 ). Ventral surface of fore tarsi and tibiae in male with numerous specialized, short and perpendicular to the surface needle-shaped setae ( Fig. 12 View Figs 9–15 ). Coxae of middle and hind legs with styli without apical supporting bristles ( Fig. 13 View Figs 9–15 ). Ratio of length of coxal styli to width of middle and hind coxae about 1.2–1.3 in both sexes. Ratio of length to width of basal article of antennae in male and females about 1.7 ( Fig. 14 View Figs 9–15 ).

Table 2 Number of hyaline spines on the legs of Petrobiellus iturupiensis sp. n.

In both sexes, urocoxites I and VI–VII with 1 + 1 eversible vesicles, but urocoxites II– V with 2 + 2 eversible vesicles. Posterior angle of urosternites II–VI approximately 116– 118°, VII about 125–130°. Ratios of lengths of urosternites and urocoxites II–VIII in male and II–VII in female; urostyli (without apical spine) and urocoxites, also apical spines and urocoxites II–IX in both sexes as shown in Table 3. Inner posterior lobes of coxites VII of female protruding between eversible vesicles; ratio of length to width of these lobes about 1.1 ( Fig. 15 View Figs 9–15 ). Distal part on inside of apical spines saw-shaped in male and especially in female. Abdominal coxites IX of female with 1 + 1 outer and 5–7 + 5–7 inner sublateral hyaline macrochaetae. In both sexes, coxites of abdominal segments I–VIII, as well as abdominal and thoracic tergites without macrochaetes.

Styli IX in male curved inward, significantly thickened and shortened, with elongated apical spines. On the surface of stylus there are about 70–75 evenly spaced, short and thickened, pigmented brown spines, the smallest in the basal inner part. Coxites IX of the male are narrowed, almost rectangular in the distal half, and widened bottle-shaped in the basal half. In the anterior part of the coxite near the stylus, they have 30–35 internally and externally 15–18 pigmented spines. In both the sexes, apices of stylus IX with 3–4 thickened and relatively long macrochaetes near the supporting spine. Male genitalia with one pair of large parameres on abdominal segment IX. Parameres with 1 + 5 divisions, slightly surpassing the apex of the penis ( Figs 16, 17 View Figs 16–20 ). The penis and parameres protrude significantly beyond the apices of abdominal coxites IX and reach the apices of their styli. The terminal article of the penis is short, curved downwards and then inward, near the apex is chitinized. A similar structure of coxites and styli of abdominal segment IX, as well as parameres, are described in the male Petrobiellus takunagae Silvestri 1943 (Sturm, Buch de Roca, 1993).

Table 3 Ratios of lengths of abdominal sternites, coxites, styli and apical spines in Petrobiellus iturupiensis sp. n.

Ovipositor slender, elongate, visibly surpassing apex of styli IX by about 1.5–2.5 mm, and is adapted for laying eggs in cracks on rocky surfaces. Anterior and posterior gonapophyses with approximately 60 and 62 divisions, respectively. Apical spines of gonapophyses as long as about 4 apical divisions combined. One and about four basal divisions of anterior and posterior gonapophyses, respectively, glabrous ( Fig. 18 View Figs 16–20 ). Distal divisions of anterior and posterior gonapophyses with 6–11 and 3–8 chaetae, respectively (not counting sensory setae and apical spines) ( Figs 19, 20 View Figs 16–20 ). Among them, the longest lateral setae are on the anterior gonapophyses.

DIFFERENTIAL DIAGNOSIS. Among the described species of the genus Petrobiellus , P. iturupiensis sp. n. most similar to P. takunagae . The main morphological differences between these species are given in Table 4.

Among the described species of the genus Petrobiellus , males are known only in P. takunagae . First of all, these species differ in the ratio of the length to width of compound eye; ratio of the width between paired ocelli and the total width of compound eyes; the width to the length of the paired ocellus; lengths of apical and preceding palpomeres of the maxillary palps, urosternites and urocoxites; posterior angle of urosternites; number of divisions in male parameres.

Table 4 Main differences between Petrobiellus takunagae Silvestri, 1943 and P. iturupiensis sp. n. ETYMOLOGY. The species name is derived from the toponym of Iturup Island where new species was collected.