Lapidisma paposanum, Molero-Baltanás & Zúñiga-Reinoso & Gaju-Ricart & Predel, 2025

Molero-Baltanás, Rafael, Zúñiga-Reinoso, Álvaro, Gaju-Ricart, Miquel & Predel, Reinhard, 2025, Morphological and molecular revision of the subfamily Heterolepismatinae (Zygentoma, Lepismatidae), with descriptions of two new genera from the Atacama Desert, Chile, ZooKeys 1260, pp. 233-278 : 233-278

Lapidisma paposanum sp. nov.

Figs 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9

Type material.

Holotype: Chile • Antofagasta Region, Paposo, La Rinconada , under stones; 24°56.644'S, 70°29.70'W; 60 m a. s. l.; 01. IX. 2023. Leg. A. Zúñiga. 1 ♀ * mounted on slide [ MNNC] . Paratypes: Same collection data as for the holotype. Two specimens mounted on slide: 1 ♂ * [ MZUC], 1 ♂ [ UCO], two specimens mounted on disc and gold coated: 1 ♂ [ MZUC], 1 ♂ [ MNNC] and two specimens preserved in ethanol 70 %: 2 ♀ [ UCO] . Chile • Antofagasta Region, Paposo, El Gaucho , under stones; 24°57.589'S, 70°28.489'W; 65 m a. s. l.; 29. IX. 2024. Leg. A. Zúñiga. Four specimens, preserved in ethanol 70 %: 1 ♂ * [ MNNC], 1 ♂ / 1 ♀ [ MZUC], 1 ♂ [ UCO] .

Diagnosis.

As indicated for the genus. Infralateral combs with 6–8 macrochaetae ( L. annectens has 5 macrochaetae on each infralateral comb). Ovipositor surpassing the apex of coxites IX by ~ 3.6 × their length (~ 5 × in L. annectens ).

Description.

Habitus as in Fig. 1 . Body length of holotype: 8 mm. Maximum body length observed in type series: 8.5 mm. Maximum preserved length of antennae in type specimens is 5 mm, but in live specimens antennae are as long as the body or slightly longer. Epidermal pigment present, brownish or brownish-violet, more intense on head, antennae (where it is uniform), legs (especially on tibiae, first tarsomere and apex of femora), lateral margins of dorsal plates, hind margins of urotergites, darker on the posterior segments and caudal filaments; ventrally, the pigment is more intense on the outer margins of coxites IX in both sexes and on the apex of parameres in males. Macrochaetae smooth, bifid, hyaline or yellowish. Body covered with orbicular scales (i. e., with lateral expansions surrounding the socket), their shapes are rounded or ovoid to subquadrangular (Fig. 2 A, B ); rounded ones are ~ 75 µm long, but some large subquadrangular can reach 170 × 100 µm; they show very dense parallel ribs, which are sometimes slightly convergent in the middle of the distal margin. Scales are also present on scape and pedicel, on the basal part of the maxillary palp, on legs (except tarsi) and on caudal filaments; the shape and size of these scales on appendages are modified compared to those covering the body, except for those on coxae.

Compound eyes with 12 ommatidia (Fig. 2 C ). Cephalic capsule with rounded scales, except on labrum. Frontal chaetotaxy extending from the periocular areas to the middle, where there is a median gap without setae (Fig. 3 A ). This marginal field of macrochaetae has two or three rows, including the periocular areas; only in the area close to the insertion of antennae there is a group of macrochaetae where additional macrochaetae can be observed. There are 1 + 1 lateral tufts of macrochaetae covering the clypeus; they can be clearly separated in the middle or relatively close together, without a wide median gap; the distal area of the clypeus bears two or three rows of rounded scales similar to those covering the head. Labrum with a continuous field of setae on its basal part and a row of five or six small setae of heterogeneous length in its distal part; the labrum is more or less folded backwards (Fig. 3 B ).

Scape longer than pedicel, both with subtriangular scales, smaller than those covering the body (~ 50 × 20 µm), frequently showing a median indentation at their truncated apex, and in this case, they can be described as bifid (Fig. 3 C, D ). Antennal flagellum with chaetic, trichoid, and basiconic sensilla, as well as trichobothria. The latter are visible on all annuli, at least two per flagellomere in the basal area of the flagellum (Fig. 3 D ), more widely spaced in the distal part. Chaetic sensilla arranged in a row (ring) around each flagellomere, similar to setae of the body, but not bifid apically and slightly flattened. Trichoid sensilla present on most flagellomeres; similar to chaetic sensilla but thinner and shorter. Two types of basiconic sensilla visible in SEM images, attributed to types A and C described by Adel (1984); in addition, coeloconic sensilla have been detected (Fig. 4 A ).

Mandibles with an incisive and a molar area, with an outer field of ~ 75–90 macrochaetae; below the molar area there is a small tuft of seven short macrochaetae (Fig. 4 B ). Galea with a small apical tubercle (Fig. 4 C ). Lacinia with ~ 7 lamellate processes and a row of six setae, at least one of them apically bifid. Maxillary palp with its apical article ~ 4.3–5.4 × longer than wide and shorter or longer than the penultimate (ratio length of the last article / length of the penultimate ~ 0.75–1.27). In the basal part of the palp, the second article has some bifid setae and several subtriangular scales, very small (~ 30 µm long) and narrow, with truncated apical margin (Fig. 4 D ). The apical article has a longitudinal row of three styloconic sensilla with a very slender cylindrical style and five or six apical cones (Fig. 5 A, B ), a distal basiconic sensillum type C and at least four basiconic sensilla type B (Fig. 5 A ).

Labium as in Fig. 5 C , with mentum clearly wider than long, the labial palp with a widened apical article (maximum width 1.1 × wider than its length and 1.6 × the maximum width of the penultimate article) which bears five papillae arranged in a jagged line; they could be described as arranged in two lines of 3 + 2 papillae, but these rows are very close together (Fig. 5 C, D ). In one specimen, an apical article has only four papillae (3 + 1). A single basiconic sensillum type C and four or five basiconic sensilla type B in the outer lateral part of the apical article (Fig. 5 D-F ).

Pronotum with a setal collar consisting of three or four rows of macrochaetae that are gradually reduced to a single row in the middle and at the anterolateral corners (Fig. 6 A ). The three thoracic nota with several marginal macrochaetae on their lateral margins and lacking setae on the posterior margins. Apart from marginal macrochaetae, some submarginal macrochaetae on lateral margins, arranged in small combs. On the pronotum, three combs of two macrochaetae on the anterior part of the lateral margin, and another one on the posterolateral corner bearing two macrochaetae; this latter comb cannot be considered as a posterior comb. Between the anterior combs and the posterolateral one, there is a section of the lateral margin with only some isolated submarginal macrochaetae; several of these (two to five on each side) can be interpreted as combs formed by one macrochaeta. Some small setae and curved trichoid sensilla are associated with these combs. Trichobothrial areas difficult to see because trichobothrial hairs are mostly detached, but one trichobothrium confirmed at ~ 0.55 of the length of the lateral side, which can be interpreted as an anterior trichobothrial area (Fig. 6 A ); in other specimen a trichobothrium was detected in a more posterior position, at ~ 0.64 the length of the notum, corresponding to a posterior trichobothrial area (Fig. 6 B ).

Mesonotum with 9 + 9 combs of macrochaetae, those on the anterior part of the lateral margin with two or three macrochaetae, and the most posterior ones with one or two macrochaetae (the one at the posterolateral edge has two). One trichobothrium, apparently not associated with a comb, on the lateral margin at ~ 0.6 of its length, and another one of another specimen at a more posterior position, associated with the penultimate lateral comb, at ~ 0.8 of the length of the mesonotum (Fig. 6 C ).

The metanotum (Fig. 6 D ) has 10 + 10 combs of one or three macrochaetae, the number of combs with three macrochaetae is lower than on the mesonotum and these are present in the anterior part of the lateral margin. A lateral trichobothrium on the posterior part of the lateral margin at ~ 0.8 of the length of the metanotum; the position of the anterior trichobothrium has not been clearly discerned.

Presternum of prothorax with two transverse rows of macrochaetae. Prosternum subquadrangular to cordiform, slightly longer than its maximum width (ratio L / W ~ 1.1), with 1 + 1 antedistal combs of two or three macrochaetae, its hind margin truncate or slightly rounded (Fig. 6 E, F ); lateral margins with several thin and long setae. Mesosternum with a similar ratio L / W and shape; the 1 + 1 antedistal combs with three or four macrochaetae, and with a lower number of thin and long setae in its lateral margin (Fig. 6 G ). Metasternum wider than long; ratio L / W ~ 0.81; 1 + 1 combs of two or three macrochaetae; thin and long setae less abundant and limited to the posterior part of the lateral margin. The hind margin of this sternite widely rounded (Fig. 6 H ).

Anterior margin of coxae with a dense row of macrochaetae, usually arranged in oblique combs of two or three macrochaetae; the posterior margin with one row of few macrochaetae, mainly inserted on the distal part of the article (Fig. 6 I ).

Femora covered with scales, more numerous on the inner (ventral) side, where they are oval to rounded, smaller than those covering the body (~ 60–70 µm long), with the apical margin truncated, with some shallow indentations (Fig. 7 A ); on the outer (dorsal) side, scales are limited to the antero-apical area and their shape is more heterogeneous, some of them are narrower and / or are bifurcated on their apical margin (Fig. 7 B ). The inner side of tibiae is covered with rounded to oval scales, similar in shape to those of femora, but smaller (most of them are <50 µm long; see Fig. 7 A ); the outer side of this article is apparently devoid of scales, only covered with setae (Fig. 7 B ). Most setae of femora and tibiae detached and only their insertions are visible; some insertions are larger, suggesting that they correspond to small macrochaetae. When preserved, macrochaetae are shorter than the diameter of tibiae; on protibiae one macrochaeta is present on the median part of the anterior (dorsal) margin and three are visible on the hind margin (one basal, one median and one subapical; see Fig. 7 C ); on metatibiae two insertions are visible on the anterior margin and the number of macrochaetae is higher at the posterior margin, but variable in the available specimens; in SEM images insertions of setae with an intermediate size are visible, smaller than insertions of macrochaetae and larger than those of normal setae (Fig. 7 A ). Protibiae ~ 3.4–3.9 × longer than wide; metatibiae ~ 4.1–4.7 × longer than wide and ~ 1.25 × longer than protibiae. Tarsomeres lacking scales; tarsomere 1 of the third leg ~ 0.57 × the length of the metatibiae, 2.25 × longer than the tarsomere 2, ~ 4 × longer than the tarsomere 3 and 2.2 × longer than the fourth tarsomere; these proportions in the first leg are 0.55, 2.4, 3, and 2, respectively. Pretarsal claws smooth, as in Fig. 7 C ; the medial empodial claw ~ 1 / 2 the length of lateral claws.

Urotergites I-VIII with 3 + 3 combs of macrochaetae. The infralateral combs bear 6–8 macrochaetae and the lateral combs 3–5. At a submedian position there are one or two macrochaetae on each side (Fig. 8 A, E ) which are interpreted as reduced submedian combs. When the submedian comb consists of two macrochaetae, they are either of equal size or the more posterior one is smaller (Fig. 8 A, D, E ). In several cases (for example, on the urotergite VII of the holotype), the smaller macrochaeta is absent (Fig. 8 C ) or even the entire comb disappears (for example, the holotype has an asymmetric chaetotaxy on urotergite VI, with 2 + 3 combs, lacking the submedian one on one side and, on the other side, there is only one macrochaeta). Some small setae are inserted posteriorly to the combs, close to the hind margin of the tergite.

Urotergite IX reduced in length and lacking setae. Urotergite X short, with hind margin convex, almost straight or rounded, in some specimens forming an ill-defined obtuse subtriangular area in the middle (Fig. 8 E ) and in some others slightly concave (Fig. 8 F ); it has only some setae on their lateral margins but lacks combs of macrochaetae.

Urosternite I devoid of setae, its median part is broken in the holotype (but visible in another specimen; see Fig. 7 A ). Urosternites II-VIII with 1 + 1 isolated lateral macrochaetae (Figs 7 A , 9 A ). Each of these macrochaetae is accompanied by some smaller setae; frequently, one or two of these can be identified as trichoid sensilla surrounding the larger macrochaetae posteriorly. In males, the urosternites VIII entire (not divided into two lateral coxites), with a straight hind margin between the styli (Fig. 9 B, C ); in females, each coxite VIII has, apart from the isolated macrochaeta inserted on the hind margin outwards to the stylus, another macrochaeta inserted inwards, accompanied by two smaller setae (Fig. 9 D ).

Four pairs of abdominal styli in both sexes, inserted on segments VI-IX (Fig. 9 ). Coxites IX of males as in Fig. 9 H, I , with the inner process ~ 1.15 × longer than wide at its base and 4 × longer than the outer process. In females, the inner process of the ninth coxite is ~ 1.4–1.5 × longer than wide at its base and 3.5 × longer than the outer process (Fig. 9 D ). The margins of the processes of coxites IX are covered by numerous long and thin setae. Males bear ovoid parameres, divided into a basal portion and an apical segment, this one bearing two small groups of glandular setae (Fig. 9 I ); the size of parameres is small to medium, not reaching the apex of inner process of coxite IX (the larger ones only slightly shorter in larger specimens, as in Fig. 9 I , some others only with a length ~ 1 / 2 the length of coxite IX, as in Fig. 9 H ). The ovipositor has ~ 34 or 35 divisions and surpasses the apex of coxites IX by ~ 3.6 × their length (Fig. 9 D ). Apex of gonapophyses VIII as in Fig. 9 J . Epiproct well developed and pigmented, covering the base of the paracercus and almost as long or even longer than the urotergite X, when this tergite has a straight or slightly concave hind margin (Fig. 8 F, G ), flanked by two similarly large paraprocts. Terminal filaments pigmented, with at least one ring of macrochaetae on each division; in addition to chaetic and trichoid sensilla, trichobothria, and narrow lanceolate scales with acute or slightly truncated apex (Fig. 9 K ; one can be seen in Fig. 9 C ).

Habitat and behaviour.

The habitat is on a coastal terrace close to the beach dominated by cacti of the species Copiapoa gigantea Backeb. The sandy clay soil is covered by many medium to small stones (Fig. 10 ). Scarce perennial vegetation is supported by the strong fogs typical of the area ( camanchaca ), in addition the area receives irregular rainfall, occasionally resulting in a short-lived herbaceous layer of annuals. Lapidisma paposanum sp. nov. has been found under stones, clinging like Thermobia to the raised stones (Fig. 1 ).

Etymology.

The specific name refers to the village of Paposo, where the new silverfish species has been found.

Figures

Figure 1. Lapidisma paposanum sp. nov., living specimen from La Rinconada (type locality) near Paposo (Atacama Desert, Chile), with the typical behaviour of clinging to the lifted stone Photo: RP.

Figure 2. Lapidisma paposanum sp. nov., SEM images of scales. A. Scales on anterolateral margin of the pronotum; B. Scales on urotergite I; C. Scales on periocular region.

Figure 3. Lapidisma paposanum sp. nov. A. Schematic overview of the head (frontal view) showing frontal and clypeal chaetotaxy; B. Scapus and pedicel with some triangular scales; C. Pedicel with triangular scales and basal annuli of the flagellum with chaetic sensilla and trichobothria; D. Head in fronto-ventral view; 1: clypeus, showing transverse fringe of macrochaetae and small rounded scales, 2: labrum, with a proximal transverse fringe of macrochaetae and a short row of five median setae distally, 3: mandible, 4: scape with triangular scales, 5: mentum (labium), 6: prothoracic presternum, 7: antepenultimate article of maxillary palp with very small triangular scales on its basal part, 8: lateral fringes of frontal macrochaetae, median part of the frons without setae, 9: apical article of the labial palp; E. Head in fronto-ventral view, specimen cleaned by ultrasonic treatment.

Figure 4. Lapidisma paposanum sp. nov. A. Different types of sensilla on the antennal flagellum; ba: basiconic sensillum type A, bc: basiconic sensillum type C, ch: chaetic sensilla, co: coelonocic sensillum, d: basiconic sensilla (diad), i: insertion of a chaetic sensillum, T: trichobothrium, tr: trichoid sensillum; B. Schematic drawing of the mandible; C. Micrography of the apex of galea and lacinia, with apex of the galea showing a small tubercle (arrow); D. Maxillary palp with some small triangular scales on the base of its antepenultimate article (one of them marked with an arrow).

Figure 5. Lapidisma paposanum sp. nov. A. Apical part of distal article of the maxillary palp with styloconic sensilla (arrows), basiconic sensilla type B (arrowheads), and basiconic sensillum type C (asterisk); B. Micrograph of the distal article of the maxillary palp of the holotype with three styloconic sensilla (arrows); C. Schematic drawing of ventral overview of labium and presternum; D. Apical article of the labial palp with five papillae arranged in two very closely spaced rows; basiconic sensilla type B marked with arrowheads, basiconic sensillum type C marked with an arrow; E. Enlarged section of (D) with basiconic sensillum type C; F. Idem, with three basiconic sensilla type B.

Figure 6. Lapidisma paposanum sp. nov., thorax. A. Pronotum with chaetotaxy of the anterior margin (collar), left lateral margin (one trichobothrium is preserved) and the posterior margin lacking setae; B. SEM image of pronotum, showing the position of a posterior trichobothrium (T); C. Mesonotum, left margin; D. Metanotum, right margin (insertions of most setae and position of the anterior trichobothrium visible); E. Prosternum of the holotype, on the posterior apical part combs of macrochaetae are visible; F. Prosternum of another specimen; G. Mesosternum, right margin and posterior apical part with combs of macrochaetae; H. Metasternum with combs of macrochaetae barely visible on the posterior margin. I .. Metacoxa with chaetotaxy. Scale bars: 0.2 mm (A, C – I); 0.1 mm (B).

Figure 7. Lapidisma paposanum sp. nov., SEM images of legs. A. Ventral view of the third leg showing scales with special shape on femur and tibia; B. Outer side of the third leg (the side observed dorsally, except for coxa and trochanter), scales with special shape can be observed on the femur; C. Ventral view on apical part of protibia with tibial spur and tarsus with pretarsal claws. Abbreviations: Cx: coxa, E: empodial claw, Fe: femur, Ltc: lateral claws, Mt: metasternum, Mulc: lateral comb of urosternite III consisting of two macrochaetae of different length, T: trochanter, Ti: tibia, Tr 1: first tarsomere, Tr 4: fourth tarsomere, UI / II: first / second abdominal sternite (urosternite I / II).

Figure 8. Lapidisma paposanum sp. nov., abdomen, dorsal. A. Urotergites I and II with insertions of macrochaetae (combs); B. Micrograph showing in detail the combs on urotergite I marked in A; C. Urotergite V; D. Urotergite VI; E. SEM image of the posterior urotergites IV – X (marked as U 4 – U 10), Lm: macrochaetae of lateral comb, Sm: macrochaetae of submedian comb; F. Hind margin of urotergite X and position of epiproct and paraprocts; G. Micrograph showing the area marked in F. Scale bars: 0.1 mm. Abbreviations: Im: macrochaetae of infralateral comb, Lm: macrochaetae of lateral comb, Sm: macrochaetae of submedian comb.

Figure 9. Lapidisma paposanum sp. nov., abdomen, ventral. A. Urosternite IV with insertions of lateral macrochaetae, the micrograph showing the details of one insertion, surrounded by additional insertions of smaller setae; B. Urosternite VIII with insertions of lateral macrochaetae and styli on the posterior margin; C. SEM image of the posterior abdominal segments of a male specimen, the straight margin of urosternite VIII is clearly visible, while that of the urosternite VII is mostly covered by scales; D. Coxites VIII and IX of the female holotype with ovipositor, styli IX are detached and only their insertions are visible; E. Detail of the left stylus on coxite VIII; F. Urosternite VI with insertions of styli; G. Urosternite VII with a single stylus preserved; H. Coxites IX of a male showing the penis and parameres; I. Detail of paramere next to the inner process of the coxite IX of another male specimen; J. Apex of gonapophysis VIII; K. Detail of some cercal divisions showing insertions of diverse types of setae, trichobothria and narrow lanceolate scales. Abbreviations: C: cercus, Cs: cercal scale, Cx 9: coxite IX (parameres and penis hardly visible below its inner margin), I: insertions of styli, Inf 7: infralateral comb of macrochaetae of urotergite VII (part of the dorsal tergite bent ventrally), Lm 6 / 8: lateral macrochaetae on posterior margin of urosternites VI / VIII, Us 7 / 8: discs of urosternites VII / VIII.

Figure 10. Habitat typical of Lapidisma paposanum sp. nov. in La Rinconada, Paposo (Atacama Desert, Chile), specimens were collected under the medium sized rocks.