Ctenolepisma phantasma Molero-Baltanás, Raphel, Mitchell & Jose, 2025

Ctenolepisma phantasma Molero-Baltanás, Raphel, Mitchell & Jose , n. sp.

( Figs 12-22 View FIG View FIG View FIG View FIG View FIG View FIG View FIG View FIG View FIG View FIG View FIG )

urn:lsid:zoobank.org:act:

Ctenolepisma calvum (non C. calvum Ritter, 1910 ) – Querner et al. 2022: 5. — Kulma et al. 2022: 112. — Shimada et al. 2023: 4. — Bednár et al. 2023: 3. — Molero-Baltanás et al. 2024a: 14.

TYPE MATERIAL. — Holotype. Spain • 1 ♀; Córdoba, basement of a house in the city of Córdoba; 7.XI.2021; M. Gaju leg.; mounted on slide; MNCN _ Ent 283578 .

Paratypes. Spain • 1♀; same locality as for the holotype; 31.X.2023; mounted on slide; UCO, Ref. Z2764b • 2 ♀; same locality and date than the first paratype; preserved in alcohol; UCO, Refs. Z2764c and Z2764d • 2 ♀; preserved in alcohol; MNHN-EA-EA110321 ; same locality as for the holotype, resulting from parthenogenetic reproduction of one of the aforementioned paratypes .

OTHER MATERIAL STUDIED. — Spain • 3 ♀; Córdoba, basement of a house in the city of Córdoba; 31.XI.2023; M. Gaju leg., UCO Ref. Z2764. Czechia • 6 ♀; Prage; 2021; M. Kulma leg., UCO, Ref. 2868). These specimens were referenced in Molero-Baltanás et al. (2024a); the Czechian specimens were previously examined for the descriptive remarks given in Kulma et al. (2022). Additional specimens have been reared in the laboratory of the Department of Zoology of UCO (Córdoba, Spain) and some of them will be deposited in the near future in the collection of MNCN, Madrid, Spain.

DIAGNOSIS. — Body length up to 12 mm. Macrosetae pectinate plumose. Epidermic pigment whitish to light yellowish. Dorsal scales transparent or light grey, heterogeneous but the most abundant widely spaced ribs. Coxae with scales similar to those covering the body. Inner side of femora with subtriangular elongated scales, with apex truncated or bifid; all the remaining articles of legs and appendages without scales. Antennae slightly shorter than body length. Cephalic chaetotaxy typical of Ctenolepisma , with a gap without macrosetae on the frontal margin and 1 + 1 tufts on clypeus and labrum. Last article of labial palp with three sensory papillae. Setal collar of pronotum with 2-3 rows of macrosetae. Lateral margins of thoracic nota bearing 5-8 pairs of lateral bristle-combs; posterior margins with 1 + 1 posterior small combs of 1-3 macrosetae each. Anterior trichobothrial areas of pronotum associated to the N-3 lateral combs; those of mesonotum associated to the antepenultimate (N-2) combs and those of metanotum associated to positions occupied by the penultimate comb. Posterior trichobothria inserted on the last lateral comb of each notum, although on metanotum the position of the last comb can lack insertions of macrosetae. All thoracic sterna with 1 + 1 subapical bristle-combs. Abdominal tergite I with 1 + 1 infralateral combs of 2 macrosetae. Urotergites II-V with 3 + 3 combs, urotergites VI-VIII with 2 + 2 combs and urotergite IX glabrous; infralateral combs consisting of 3-4 macrosetae; remaining dorsal combs of abdomen only with 1-3 macrosetae. Urotergite X trapezoidal, short; its posterior margin straight or slightly concave. Urosternites I and II bare; urosternites III-VIII with 1 + 1 lateral combs of 4-8 macrosetae. Only one pair of styli inserted on abdominal segment IX. Inner process of coxite IX about 1.2 times longer than wide at its base and about four times longer than the outer process. Ovipositor short, with about 20 divisions; its apex not clearly surpassing the tip of styli. Maximum length of cerci up to 7 mm. Male unknown (all populations studied parthenogenetic). Ctenolepisma phantasma Molero-Baltanás, Raphel, Mitchell & Jose , n. sp. is the only European Ctenolepisma with 3 + 3 urotergal combs on abdominal segments II-V (the remaining species bear 3 + 3 combs on urotergites II-VI or II-VII) and the species with a lowest number of macrosetae per comb and shorter ovipositor. The presence of only three labial papillae and the pattern of scales of legs (truncate subtriangular scales on femora combined with absence of scales on tibiae) are other exclusive characteristics of this species in the European continent. It can be distinguished from other synanthropic species following the characters indicated for C. calvum in the key presented by Molero-Baltanás et al. (2024a). Ctenolepisma calvum ( Ritter, 1910) from Kerala and Sri Lanka and C. rothschildi Silvestri, 1907 are the closest species, but both species show five papillae in labial palp, a greater number of macrosetae on most combs, and two pairs of abdominal styli; for a more detailed comparison with C. calvum from Kerala, see discussion and Tables 4 View TABLE and 5. View TABLE

ETYMOLOGY. — The specific name “phantasma ” is taken from the Latin word that derives from the Ancient Greek ΦΆντασµα (phántasma), which means phantom or ghost, and is used to follow the common name used in some previous publications (for example, Querner et al. (2022)) for records of this insect in Europe (ghost silverfish).

TYPE LOCALITY. — Spain, Córdoba, basement of a house in the city of Córdoba.

DESCRIPTION

Male unknown.Body length of holotype: 9 mm; some Japanese specimens up to 12 mm, but the maximum body length of studied European specimens not surpassing 10 mm. Habitus as in Figure 12 View FIG (see also figures in Kulma et al. 2022; Querner et al. 2022; Shimada et al. 2022). Epidermic pigment whitish to light yellowish, more intense on head and last abdominal segments; scales and appendages almost hyaline, except for dorsal scales of some specimens that can be light greyish.Head width up to 1.2 mm, thorax width up to 2.1 mm. Antennae shorter than body, reaching 7.5 mm when intact. Caudal filaments shorter than antennae, frequently broken; maximum length preserved in a paracercus about 7 mm. Macrosetae plumose, hyaline to yellowish.

Scales

Scales hardly visible even with stereomicroscope. Dorsal scales ovoid to quadrangular, with several widely spaced parallel ribs ( Fig. 13 View FIG ); most of them with a low number of ribs, about 12- 15, and a waxy sheen when observed by SEM. Ventral scales similar in shape but with more dense and numerous parallel ribs (up to 40 ribs per scale; see Figure 14 View FIG ). Appendages without scales except for antennal scape, coxae and femora (see below); clypeus and labrum also without scales.

Head

Frons with 1 + 1 tuft of about 40 macrosetae separated by a distance similar to the width of a tuft. Inner margin of each eye surrounded by one row of 8-10 macrosetae; lateral areas of head bearing 1 + 1 frontolateral tufts of about 20 macrosetae between these periocular tufts and the frontal ones, and 1 + 1 small group of 2-3 macrosetae above the frontolateral tufts ( Fig. 15 View FIG ). Clypeus with 1 + 1 lateral tufts bearing about 35 macrosetae and some thin acute setae on the median area between these tufts. Labrum with 1 + 1 small tufts of macrosetae and an irregular transverse fringe of thin acute setae connecting the tufts.

Antennal scape about twice longer than the pedicel, with a subapical ring of setae. Pedicel with a similar ring, and some additional setae forming two lateral groups. Scape covered with scales and pedicel without scales ( Fig. 16 View FIG ). Scales of scape rounded, orbicular, with dense parallel ribs. Flagellomeres with one or two rows of chaetic sensilla. Basal flagellomeres with trichobothria; only some annuli of the distal part of the flagellum bearing trichobothria.Apart of these types of sensorial setae, other types of sensilla present on the flagellum: trichoid sensilla, coeloconic sensilla, campaniform sensilla and three types of basiconic sensilla; these latter belonging to types A, B and C according to the classification presented by Adel (1984).

Mandibles typical, bearing a subapical group of about 10 strong short setae that are pigmented and apically bifurcated, and a large outer tuft of about 55-60 macrosetae. Galea of the maxilla with 5-6 smooth acute setae in its basal half and some apical cilia; lacinia with two strong teeth, 6-7 lamellate processes and a row of five thin setae. Apical article of maxillary palps slender, about seven times longer than wide and similar in length to the penultimate article; distal part of the article with several basiconic sensilla of types B and C. Antepenultimate article of the maxillary palp slightly longer than the apical one. Labium wider than long; distal part of the prementum with a transverse row of setae. Glossae and paraglossae with some groups of setae forming an oblique fringe. Apical article of labial palp oval, about 1.1-1.2 times longer than wide and as long as the penultimate article or slightly shorter; bearing only three papillae arranged in a row ( Fig. 17 View FIG ).

Thorax

Pronotum ( Fig. 18A View FIG ) with a setal collar consisting of 2-3 irregular combs of pectinate macrosetae. Between this collar and the anterolateral corners of the pronotum, an anterolateral row with some smooth and bifid setae. Lateral margins of the pronotum bearing about eight combs of 1-4 macrosetae; some of these combs difficult to identify because consisting of only one macroseta and, as a consequence of this reduction, interpretable as isolated marginal macrosetae. Anterior trichobothrial areas associated to the comb N-3, i.e., the anterior to the antepenultimate lateral comb; posterior trichobothrial areas associated to the last lateral comb or, if the comb in this position is not clearly distinguishable, posterior trichobothria located at about 0.72 the total length of the lateral margin. Trichobothria inserted on the inner part of the trichobothrial area.

Mesonotum ( Fig. 18B View FIG ) with 7-8 combs of 1-3 macrosetae on each lateral margin and usually two additional isolated setae on the anterolateral corner. Anterior trichobothrial areas on the antepenultimate lateral comb (N-2). Posterior trichobothrial areas associated with the last lateral comb or, when this comb is not clearly visible, to the position 0.77 of the lateral margin of this mesothoracic dorsal plate.

Metanotum ( Fig. 18C View FIG ) with 5-8 lateral combs on each lateral margin and usually 1-3 additional isolated setae on each anterolateral corner. Lateral combs very reduced, consisting of 1-3 macrosetae; the two posterior ones of each side reduced to one marginal macroseta; if combs are visible, anterior and posterior trichobothria associated to these two lateral combs; if not visible, inserted about 0.65 and 0.84 along the length of the lateral margin, respectively.

Posterior margin of the thoracic nota with 1 + 1 small lateral combs consisting of one or two macrosetae (in some specimens, those of the pronotum bear three macrosetae). When there are two macrosetae, one of them usually larger than the other (thicker, longer and with a larger insertion).

Prosternum ( Fig. 19A View FIG ) subtriangular, its posterior margin rounded; apical part sub-elliptical whith 1 + 1 subapical groups of 3-4 macrosetae that are not arranged in a clearly straight row; anterolateral corners and apical part of the sternite with some thin marginal setae. Mesosternum ( Fig. 19B View FIG ) with a similar shape, but larger than the prosternum, bearing 1 + 1 subapical oblique combs of 4-5 macrosetae. Metasternum ( Fig. 19C View FIG ) heart-shaped, with its posterior margin broadly convex to slightly truncate; 1 + 1 subapical combs of of 4-6 macrosetae; the distance separating these combs about four times longer than the width of a comb. Prosternum and mesosternum slightly longer than wide (ratio length/width about 1.1-1.15), metasternum clearly wider than long (ratio length/width about 0.87).

Legs

Size of legs increasing from the first to the third thoracic segment; metatibiae about 1.3-1.4 times longer than mesotibiae and 1.6 times longer than protibiae. Coxae with some marginal macrosetae, covered by rounded scales similar to the ventral scales covering the body. Femora covered with setae on the ventral/inner part of their outer side (visible dorsally); rest of the surface of this outer side of femora without scales or setae; inner side (visible ventrally) with modified scales and setae; scales triangular, usually longer than wide and truncate or concave apically, with slightly marked ribs ( Fig. 20 View FIG ), present only on the dorsal/external part of the article. Protibiae about 3.3-3.4 times longer than wide, mesotibiae about 3.8- 3.9 and metatibiae about 4.4-4.5 longer than wide. Tibiae lacking scales, only covered with setae and bearing two robust macrosetae on the dorsal (anterior) margin and 3-5 on the ventral (posterior) margin; these macrosetae about as long as the width of tibiae, or slightly shorter on metatibiae. Tarsi about 1.2 times longer than the corresponding tibia; basal tarsal article (tarsomere 1) about 0.7- 0.8 times longer than the tibia. Tarsomere 1 of first and second legs with two rows of slender spines that are absent in the third legs. Pretarsus with two claws and a small empodium.

Abdomen

Urotergite I with 1 + 1 lateral combs. Urotergites II- V with 3 + 3 combs of macrosetae ( Fig. 21A View FIG ). Urotergites VI- VIII with 2 + 2 combs, and urotergite IX lacking setae. Infralateral combs usually consisting of 3-4 macrosetae, except for those on urotergite I, that have two macrosetae. Lateral combs consisting of 2-3 macrosetae, and the submedian combs usually consisting of one or two macrosetae. Urotergite X ( Fig. 21B View FIG ) short trapezoidal, with a ratio length/width of the posterior trapezoidal part about 0.25-0.3; posterior margin straight or slightly concave and lateral margins with several setae in their posterior part and 1 + 1 subapical combs of two macrosetae. Urosternites I and II devoid of setae; urosternites III- VII with 1 + 1 lateral combs of 4-8 macrosetae each (usually five or six). Distance between lateral urosternal combs 8-18 times higher than the width of a comb ( Fig. 21C View FIG ). Each coxite VIII with a comb of 4-5 macrosetae. Inner process of coxites IX about 1.2 times longer than wide at the base and about four times longer than the outer process. Only one pair of abdominal styli that are about 2.5 times longer than the length of the inner process of the coxite IX. Ovipositor short, with 19- 21 divisions, far surpassing the apex of the inner processes of coxites IX but hardly exceeding the apex of styli ( Fig. 22 View FIG ). Caudal filaments with large plumose macrosetae, smooth chaetic sensilla, trichoid sensilla and trichobothria.

REMARKS

The abdominal chaetotaxy of this species is difficult to discern using stereomicroscope and even light microscope for dissected and mounted specimens, because most macrosetae are usually detached and only their insertions are visible, and examining these insertions is difficult in some slide-mounted specimens because of the presence of numerous drops of fat coming from the gut contents, probably related to the diet of the silverfish. In some cases, using SEM microscope helps to clarify several characters; Shimada et al. (2022) provided dorsal and ventral views of the abdomen that are very useful; moreover, appropriate micrographs such as those shown in this work and in Kulma et al. (2022) are also useful.

A complete description of this species was given by Molero-Baltanás et al. (2024a) with the name Ctenolepisma calvum . The present description does not provide additional information and only some figures are new. The morphological differences with other synanthropic silverfish were discussed in that work, together with molecular data and some comments regarding mistakes on previous papers where this species was recorded in Europe. Differences with the authentic C. calvum described here are given in the Discussion section and summarized in Tables 4 View TABLE and 5 View TABLE .

Apart from those indicated in “ Type material” and “Other material studied”, no additional specimens have been reexamined. The remaining specimens referenced in other papers ( Querner et al. 2022; Shimada et al. 2023; Bednar et al. 2023) are not examined, but the morphological details given in these papers, together with the DNA sequences of some of them, confirm that the specimens studied in all these papers are not C. calvum , but conspecific with C. phantasma Molero-Baltanás, Raphel, Mitchell & Jose , n. sp.