Hemitelsella luismendesi, Smith & Mitchell & Mesaglio, 2022

Smith, Graeme B., Mitchell, Andrew & Mesaglio, Thomas, 2022, Two New Australian Silverfish (Zygentoma: Lepismatidae: Ctenolepismatinae and Nicoletiidae: Subnicoletiinae), Records of the Australian Museum (Rec. Aust. Mus.) 74 (2), pp. 59-74 : 61-68

Hemitelsella luismendesi sp. nov. Smith & Mitchell urn:lsid:zoobank.org:act:A5C74ADC-80EB-4BDD-9908-86D3AE9C706D

Figs 2–32

Holotype ♀ ( HW 0.78) SOUTH AUSTRALIA: North of Marla 26.9724°S 133.4000°E 378m asl, 7.vii.2020, Graeme Smith , hand collected in deep dry leaf litter, SAMA 21-000419 & 21-000419A (on two slides) . Paratypes 1♂ ( HW 0.79) same data as holotype, SAMA 21-000420 & 21-000420A (on two slides) ; 1♀ ( HW 0.73) same data as holotype, AMS K.377943 (in alcohol) ; 1♂ ( HW 0.63) same data as holotype, AMS K.377942 (in alcohol) .

Diagnosis. This species is quite distinct from all other described Hemitelsella species and can be distinguished by a combination of characters including its much smaller size (less than 5 mm versus 7–8 mm), the apparent lack of a striking scale pattern, the arrangement of the macrochaetae in the anterior bushes on the frons into distinct rows, the posterior combs of the pro and metanota each consisting of 1–3 macrochaetae (versus one or rarely two in all other described species) and located some distance from the lateral chaetotaxy (almost contiguous in other species), the presence of 1+1 submedial combs on urosternite II, the pointed tips of the larger setae of the tarsal articles (versus rounded tips), the square inner corners of coxites VIII and the presence of three short transverse combs on coxites IX, the most posterior of which may consist of just one or two pectinate macrochaetae.

Description

Appearance: Small silverfish, with narrow body, thorax not much wider than abdomen which only tapers slightly posteriorly from about the fifth abdominal segment ( Fig. 1 ). Appearance when live unrecorded. In alcohol, quite blotchy overall in appearance but with more darker scales on urotergite IX, lateral margins of nota light in appearance, without dark scales possibly hyaline or absent, dark scales on dorsal end of femora and top of tibia, urotergite X with light coloured scales and little pigment, styli IX light coloured with slightly orange apex. Terminal filaments light coloured, slightly more orange distally.

Body size: 4.46 mm; head width 0.79 mm; thorax: length 1.28 mm or 0.31 times H+B; width up to 1.09 mm with no great difference between the pro-, meso- and metanota although the pronotum is the narrowest; antenna incomplete> 0.93 mm or>0.23 times H+B; terminal filaments all incomplete, maximum length of cercus remaining 1.88 mm or>0.47 H+B; maximum length of median dorsal appendage remaining 1.78 mm or>0.5 H+B.

shown above the branches

Pigmentation: Pigment generally quite orange in colour. Frons with light brown even pigment, clypeus, labrum without pigment, scape and pedicel with moderate orange pigment, the intervals of the flagellum initially with light orange pigment but becoming increasingly darker distally. Maxillae palp with fairly even and moderately dense orangebrown pigment which is darker at the distal end of each article. Labium with orange-brown pigment, the palp also well pigmented overall and darker along the outer margin of all articles. Legs with light to medium orange-brown pigment overall, with darker areas on shoulders of coxa, the distal end of the femora, most of tibia especially dorsally and distally, all tarsal articles with pigment which is darkest at the distal end of each article. Nota and abdominal tergites without obvious pigment but cuticle closer to lateral margins of more granular appearance, thoracic sterna without pigment. Urotergites and urosternites I–VII (VIII in ♂) unpigmented, urotergite X without pigment distally but some around base above cerci. Coxites VIII of female somewhat orange overall, coxites IX of female with quite dark brown around the stylus insertion and along the medial margin. Penis with light pigment overall, styli mostly without pigment slightly more orange at tip, cerci and median filament without obvious pigment basally but becoming more orange-brown distally without annulations. Ovipositor quite dark orange-brown with sutures slightly darker than the surface.

Macrochaetae: pectinate and of variable form ( Figs 3–6 ), mostly light to brown, but hyaline or straw coloured in some cases. The macrochaetae along the edges of the nota only have minute apical bifurcations and are tapered with very subtle pectinations along the shaft and quite different to the submarginal macrochaetae which are obviously pectinate especially apically. The larger setae of the tarsi are not strikingly sclerotized and lack the rounded tips seen is other species of Hemitelsella .

Scales: with numerous subparallel ribs that only just surpass the margin of the scale, with ribs mostly close together or even very close together in the darker scales ( Fig. 7 ), these ribs are sometimes diverging from each other distally giving an open fan appearance rather than being almost parallel; shape of scales generally round, although the posterior margin can be quite straight for those scales overhanging the posterior margins of the tergites and others are shaped to fit around setae or combs. Scales found on top of head, on clypeus, scape, the second article of the maxillary palp, all nota, all thoracic sterna, legs but absent from trochanter and tarsi (except the basal article of all tarsi), present on all urotergites and urosternites, styli and on the terminal filaments, even the more distal divisions. Scales of the terminal filaments seem to be of just one type ( Fig. 8 ) which appear somewhat similar to those of the Nicoletiidae with the “ribs” or folds appearing to converge at the attachment point however the detailed structure of the scales is uncertain; lanceolate scales were not seen.

Head: wider than long ( Fig. 9 ), with 1+1 moderately strong bushes of pectinate macrochaetae on the antero-lateral corners, the macrochaetae aligned in distinct sublongitudinal rows. A small gap in the chaetotaxy of only about one macrochaeta wide is present along the margin above the antennae and the macrochaetae continue along the margin about three wide for a short distance behind the antennae then another abrupt change occurs with the row only one or two wide until another gap before the supraocular macrochaetae. The 1+1 peri-antennal groups are slightly isolated from marginal rows and consist of only four macrochaetae as well as a cilium or long thin setae. Eyes reddish brown with each ommatidium somewhat isolated from the adjacent ommatidia. Clypeus with 1+1 bushes of about 40 macrochaetae closely packed together, 1+1 setae between the larger bushes close to the dorsal margin. Labrum also with 1+1 bushes of about 20 smaller pectinate macrochaetae as well as a few setae between these groups and two transverse lines of smaller setae, one about midway along the labrum which may be of only four simple setae, the other ¾ behind the anterior end of the labrum. — Scape of antenna ( Fig. 10 ) of medium length, with scales over surface and short robust simple subapical setae, pedicel with a subapical ring of stout setae and another small group of setae ventrally about one third the way along the pedicel, first annulus (interval) of flagellum glabrous, intervals two to four of flagellum each of a single annulus with a single ring of setae, and one or probably two trichobothria; interval five beginning to subdivide into two annuli; sixth interval with two annuli, the basal with setae and cilia, the distal with setae and trichobothria, each interval divided into four annuli by the ninth interval with the trichobothrium only present in the most distal ring. More distal intervals lost in both slide mounted specimens. — Mandibles ( Fig. 11 ) typical for Ctenolepismatinae ; a group of about 6–9 strong and short and thinner and longer, apically bifurcated setae distally adjacent to the molar area and two bushes of about 25 and 30 macrochaetae externally. — Maxilla ( Fig. 12 ) with three thick apically bifurcate macrochaetae externally proximal to the palp, the lacinia with three strong teeth, one set further back than the other two, followed by about seven lamellate processes and a row of 2–3 thin simple setae, galea with 3–4 strong, smooth, pointed setae externally in its basal half and a few cilia distally; apical article of maxillary palp ( Fig. 13 ) 3.3–4.0 times longer than wide and 1.2–1.4 times longer than the penultimate article, the ultimate article with a sensillum (probably poculiform) about one quarter back from the apex, rod-like basiconic sensilla were not seen, last three articles of palp with simple setae only although some thicker than others, second article with a subapical ring of stronger setae and scales on the outer face, basal article with a few slightly thicker short setae. — Labium ( Fig. 14 ) much wider than long; prementum with a transverse row of strong setae, the most laterad showing pectinations; glossae and paraglossae with oblique and irregular transverse groups of strong apically bifurcated setae and with short curved setulae distally; labial palp with oval/subrectangular apical article, slightly widened medially, 0.8–1.2 times longer than wide with row of 8–10 papillae arranged in a single curved row, other sensilla not observed, covered with numerous fine short, sometimes pigmented, setae as well as longer fine setae on along the distal end; penultimate article as long as the ultimate article.

Thorax: pronotum ( Fig. 15 ) with setal collar about two macrochaetae wide of both longer and fairly short, strongly pectinate macrochaetae, and a few cilia; lateral margins with many strong smooth or subtly pectinate short macrochaetae as well as some submarginal setulae and cilia, with 7–8 submarginal combs of 1–3 strongly pectinate macrochaetae, the anterior trichobothrial area about 0.42–0.48 along the margin associated with comb N-2 (terminology of MoleroBaltanás, 2010) the trichobothrium located between the comb of one or two macrochaetae and the margin ( Fig. 16 ), the posterior trichobothrium located at the mediad end of a comb of two macrochaetae located about 0.71 distance along the margin ( Fig. 16 ). Posterior margin with 1+1 combs each of 1–2 pectinate macrochaetae each associated with a marginal seta and a cilium, the posterior combs being positioned somewhat laterally but quite separate from the chaetotaxy of the lateral margin. — Mesonotum ( Fig. 17 ) with lateral chaetotaxy similar to pronotum with eight submarginal combs of 1–3 pectinate macrochaetae, the anterior trichobothrial area located about 0.65–0.66 along the lateral margin, associated with comb N-2 with the trichobothrium located between the single macrochaeta and the margin and with a cilium between the trichobothrium and the seta on the margin. Posterior trichobothrial area 0.84–0.86 along margin, the trichobothrium located mediad to a group of 2–3 macrochaetae (= N) arranged in a line not in a triangle, (which was an unusual arrangement reported in the description of the single known specimen of H. clarksonorum Smith, 2016 ). Posterior margin with quite laterad 1+1 combs each of three macrochaetae with a cilium at the outer end and a marginal seta. — Metanotum ( Fig. 18 ) similar to mesonotum with eight combs of 1–2 macrochaetae, the anterior trichobothrial area associated with the comb (N-1) with the trichobothrium located between the single macrochaeta and the margin about 0.73 along the margin, the posterior trichobothrial area associated with the most posterior comb (N) of a single macrochaeta about 0.84 along the margin and the posterior 1+1 combs each of 1–3 macrochaetae, a laterad cilium and a marginal seta ( Fig. 19 ), also quite distant from the lateral chaetotaxy.

Presternum fairly wide, with transverse row of setae (all lost in holotype) and some small setulae or cilia ( Fig. 20 ). All thoracic sterna with hyaline scales. — Prothoracic sternum ( Fig. 20 ) quite broad, wider at base than long, (L/ W 0.88 –0.89) subtriangular but broadly rounded on all corners, antero-lateral corners with one or two small setae, posterior two thirds of lateral margins with long simple setae as well as 5+5 irregular combs of 3–4, 3–5, 1–4, 1–4 and 1–2 strongly pectinate thin macrochaetae and sometimes with additional submarginal macrochaetae between the two most posterior combs. — Mesosternum ( Fig. 21 ) a little longer than wide (L/ W 1.09) and 1.2 times as long as the prosternum, with long, thin simple marginal setae around the distal third of the margin, 3+3 combs in its distal third, with 4–5, 4 and 1–2 pectinate macrochaetae per comb (anterior to posterior). — Metasternum ( Fig. 22 ) wider than long (L/ W 0.74) apically rounded, quite short only 0.93 times as long as the prothoracic sternum, and with long marginal setae along distal ⅓ of lateral margins and 3+3 combs of longer and shorter pectinate macrochaetae, the more proximal with 4–5, the middle with 4–5 and the most posterior with 1–2 macrochaetae.

Legs ( Figs 20–22 ) becoming progressively longer and more slender, tibia L/W ratio of legs PI 2.6–3.2, PII 2.4–2.7, PIII 3.1–3.8; tarsi L/W ratio PI 4.5–7.2, PII 5.4–7.5, PIII 6.0–7.9. PI ( Fig. 20 ) with comb of three macrochaetae laterally on precoxa. Coxa with scales and a comb of about five macrochaetae on the anterolateral corners followed by scattered strong pectinate macrochaetae along the external margin, never grouped into combs of two macrochaetae, the more marginal macrochaetae being much less pectinate, curved and tapering; inner margin with three strong macrochaetae spaced along the margin and about six setae of varying thickness distally over the articulation. Trochanter with several curved setae and one small pectinate seta. Femur ventrally with two strong, pectinate macrochaetae between the trochanter and the posterior bulge, two strong pectinate carrot-shaped macrochaetae on the bulge and another a small distance distally plus some small curved setae towards the distal end and a cluster of three strong pectinate carrotshaped macrochaetae over the articulation; anterior margin without macrochaetae. Tibia of PI with two pectinate carrotshaped macrochaetae about one quarter from the end, and two stronger pectinate carrot-shaped macrochaetae on the ventral margin as well as other setae, setae absent from much of the ventral surface except for the distal end, usual tibial spur with a few setae. Tarsi of four articles, the basal tarsal article of PI about 40% of the total length of the tarsus, its join with the next article not particularly oblique, the ventral face of all tarsal articles with setae that are only slightly more robust than the other setae and not as strongly rounded as in other species of the genus. Pretarsus with two long curved lateral claws and a much shorter curved medial claw. PII and PIII ( Figs 21 , 22 ) similar to PI with only a single seta on the precoxa, lacking the antero-lateral comb on the coxae; the pectinate carrot-shaped macrochaetae on the outer margin of the tibia are progressively more proximal than on PI; legs not dramatically progressively longer anterior to posterior with the tibia of PII being only 1.0–1.1 times longer than that of PI and the tibia of PIII being 1.3–1.5 times longer than that of PI, the relative length of the basal tarsal article is progressively longer, being about 55% of the total length on PIII.

Abdomen: urotergite I with 1+1 lateral combs of 2–3 macrochaetae each comb associated with one or two marginal setae and 0–2 cilia, urotergites II–VII ( Figs 23, 24 ) with 3+3 combs of macrochaetae as in table 2, the lateral combs also associated with 0–3 small marginal setae and 0–2 cilia, the sublateral combs sometimes associated with a cilium and/or a marginal seta, the submedial combs sometimes associated with a cilium at the laterad end of the comb and 0–2 cilia; urotergite VIII with 2+2 combs, lacking the sublateral comb. Urotergite IX glabrous although a marginal setula insertion is visible on one side in the holotype in the infralateral position. Urotergite X ( Fig. 25 ) triangular with pointed apex (85–88°), wider than long (L/W at base about 0.50–0.53) with strong curved tapered slightly pectinate macrochaetae as well as shorter more obviously pectinate macrochaetae along the lateral margins; with 3+4 combs of 1–4 stout and strongly pectinate macrochaetae.

Urosternite I glabrous, urosternites II–VII with 1+1 lateral combs of 6–9 pectinate macrochaetae ( Figs 26, 27 ) each sometimes associated with 1–2 marginal setae but without a cilium; the combs on the male occasionally interrupted by a space. Styli present on coxites IX only in both sexes. The distance between the combs relative to the average length of each comb is 3.8–8.1.

Genital region of female ( Fig. 28 ) with coxites VIII having quite square inner corners with very little rounding, each coxite bearing a comb of 9–12 pectinate macrochaetae as well as 2–3 small marginal setae. Internal process of coxites IX short, 1.07–1.12 longer than wide at the base and only 2.8–3.0 times longer than the pointed external process, not quite reaching to the end of the ovipositor. Each internal process with a basal smooth macrochaeta mediad of each stylus insertion. Each process with two short transverse combs of pectinate macrochaetae as well as 1–2 additional pectinate macrochaetae near the apex; the more anterior comb of 3–4 macrochaetae, the more posterior of 5–7 macrochaetae; both margins of the inner process with several long rounded, more carrot-shaped and subtly pectinate macrochaetae. — Ovipositor short (1.35 HW) of secondary type, not surpassing the apex of the short internal processes of coxites IX, both pairs of gonapophyses consisting of a long basal division (about one third to one half the length of the ovipositor), and eight or nine smaller divisions; anterior gonapophyses ( Fig. 29 ) with five modified spines (conules) on the last division, plus one modified spine on each of the next four divisions which also have several long fine setae, posterior gonapophyses with four very robust conules and 2–6 smaller narrower conules as well as a few small setae, following division with two medium and three smaller conules, following division with a single narrow conule and two thin setae, subsequent divisions with small thin setae only ( Fig. 30 ).

Cerci ( Fig. 31 ) basal division almost as long as wide with a partial ring of setae on outer side; following three divisions much wider than long, each with a single ring of setae and macrochaetae as well as some trichobothria; division five about as long as wide, with a sub-basal ring of trichobothria and scales and a antedistal ring of setae, macrochaetae, trichobothria and cilia; sixth division similar except sub-basal ring also with some setae; seventh division with four rings, the sub-basal of scales only, the next of setae and trichobothria, the next with scales and trichobothria and the antedistal as in the previous division; division eight similar except also some trichobothria in the sub-basal ring; division nine with seven rings, the sub-basal of scales and trichobothria, the next with setae and trichobothria, the third with setae and cilia, the next with setae and trichobothria, the fifth ring of scales only, the sixth of setae and cilia and the ultimate as in previous divisions. Median dorsal appendage ( Fig. 31 ) similar, basal division with two incomplete rings of setae; second division with single ring of setae only; the third division with a sub-basal ring of scales and an antedistal ring of setae, macrochaetae and cilia; the next division similar but with some setae in the sub-basal ring; the fifth division of four rings with the sub-basal and third rings of scales only, the second of setae and the most distal as for the cerci; the sixth division similar except a trichobothrium in the second most apical ring of scales; the seventh similar but also with some setae in the second most distal ring.

Male: Urosternite VIII with slightly concave posterior margin. Each coxite IX ( Fig. 32 ) with 3+3 transverse combs of 1–5 macrochaetae across medial half of the inner process and a single macrochaeta on the face posterior to the transverse comb adjacent to the stylus insertion; the internal process not acute nor elongated, about twice as long as the external process but only 0.67–0.76 as long as broad at its base; external and internal margins of internal process with several long, often pectinate setae. Outer process small, acute triangular with a few robust setae along the outer margin. Only one pair of styli present (IX) (lost in slide mounted allotype). Penis typical with numerous glandular setae apically, each set on a protuberance. Parameres absent.

Habitat. Hand collected using trowel in deep dry leaf litter.

Etymology. The species is named luismendesi in gratitude for the advice I obtained during a few days spent in 2008 and 2009 with Dr Luis Mendes, a very dedicated and talented entomologist. Twenty years of accumulated questions were answered with practical examples and advice. His willingness to share his knowledge and offer encouragement took my work to a higher level and is much appreciated.

Discussion

Molecular data

In contrast to the results obtained for the Heterolepismatinae (Smith et al., 2019) where we failed to identify morphological differences between clades with comparatively large differences in base pairs of 0.9–1.8% for 28S and 7.2% for COI, we find quite pronounced differences in morphology between species that have almost identical 28S sequences and only 5.2% difference in COI. Based on characters usually considered as stable within the Ctenolepismatinae (the shape of the ultimate article of the labial palp, the arrangements of combs on the thoracic sternites) as well as the greatly different scale pattern there seems little doubt that all four species are distinct. Heterolepisma clarksonorum and H. hortorum have, however, only been described from single specimens, so we have no knowledge of morphological variability in these species. It would appear however, that the molecular differences between morphologically quite distinct species, are considerably smaller than observed in the Heterolepismatinae and more in line with that observed in other more recent insect orders. In our experience the present situation is more common in insects, where the more slowly evolving 28S rDNA gene sequences are useful for phylogeny but often are identical among related species (e.g., Wilson et al., 2014).

Morphology

The molecular data place Hemitelsella luismendesi sp. nov. in a clade distinct from the other described species of the genus and closer to Qantelsella louisae Smith. While having several characters that distinguish it from the other species of Hemitelsella , none of these are characters that would indicate a closer relationship with Qantelsella . It has 3+3 combs on urotergites II–VII not 2+2 combs of Qantelsella and it has the transverse combs on coxites IX which are typical of species of Hemitelsella but are lacking in Qantelsella spp.

The genus Hemitelsella appears to be widely distributed in southern Australia with three species described from Western Australia, one from Tasmania and now another from South Australia. Further undescribed species are known from Western Australia. It does not appear to be common. All species so far described have transverse combs on coxites IX and only a single pair of abdominal styli. The ovipositor is short and armed apically with modified spines.

The presence of 1+1 submedial combs on urosternite II was surprising. Mendes (1982) reviewed the various patterns of urosternal chaetotaxy showing that this character is very uncommon within the Lepismatidae being reported only for Panlepisma (unplaced) and all genera of the Heterolepismatinae ( Heterolepisma , Maritisma and Visma ). The presence of 1+1+1 combs on urosternite II is more common, occurring in some species of Allacrotelsa (Lepismatinae) , Hyperlepisma (Ctenolepismatinae) and Mirolepisma (Mirolepismatinae) . The occurrence of medial combs only on urosternites is also quite common. The occurrence of 1+1 submedial combs in this new species is probably an incidental expression of a primitive condition and of no particular phylogenetic relevance.

Figures

Figure 1. ML tree for concatenated COI and 28S genes with ML bootstrap values and BI posterior probabilities

Figure 2. Hemitelsella luismendesi sp. nov. holotype ♀ habitus

Figures 3–14. Hemitelsella luismendesi sp. nov. holotype ♀ (3) pectinate macrochaeta of peri-ocular group; (4) pectinate macrochaeta of prosternum; (5) pectinate macrochaetae of pronotum; (6) carrot-shaped pectinate macrochaeta from femur of PI; (7) darker scale of pronotum; (8) scale of terminal filaments; (9) head (left side missing, cross-hatched area obscured by eye pigment); (10) antenna, scape, pedicel and basal articles of flagellum; (11) mandible; (12) maxilla; (13) ultimate article of maxillary palp showing possible poculiform sensilla (ps?); (14) labium, prementum and mentum, setae of right palp largely omitted. Scale bars = 0.1 mm.

Figures 15–21. Hemitelsella luismendesi sp. nov. holotype ♀ (15) pronotum, right half; (16) idem, right trichobothrial areas; (17) mesonotum, right side; (18) metanotum, right side; (19) idem, left posterior comb; (20) presternum, prothoracic sternum and PI; (21) mesosternum and PII. Scale bars = 0.1 mm.

Figures 22–27. Hemitelsella luismendesi sp. nov. holotype ♀ (22) metasternum and PIII; (23) urotergite IV; (24) detail of left combs of urotergite III; (25) urotergite X; (26) urosternite II; (27) idem, detail of left comb. Scale bars = 0.1 mm.

Figures 28–32. Hemitelsella luismendesi sp. nov. holotype ♀ unless otherwise indicated by specimen number (28) left coxite VIII, coxites IX and apex of ovipositor, setae of left stylus not shown; (29) apical divisions of anterior gonapophyses; (30) apical divisions of posterior gonapophyses; (31) base of cercus and median dorsal appendage; (32) ♂ (SAMA 21-000420A), coxites IX and penis, styli lost. Scale bars = 0.1 mm.