Acrotelsella tanni, Smith & Mitchell, 2022

Smith, Graeme B. & Mitchell, Andrew, 2022, On some Silverfish Taxa from the Mildura Region (Inland South-eastern Australia) (Zygentoma: Lepismatidae: Ctenolepismatinae), Records of the Australian Museum (Rec. Aust. Mus.) 74 (5), pp. 151-199 : 188-195

Acrotelsella tanni sp. nov.

urn:lsid:zoobank.org:pub:5AE074A3-1922-4BF9-88D6-2DFF2B6AA557

Figs 124–156

Holotype ♀ ( HW 1.73 ) NEW SOUTH WALES: Mungo National Park 33.491°S 143.101°E 26.viii.2017, J. Tann, bark spray, AMS K.377775 (on two slides) . Paratypes 1♀ ( HW 1.54 ) same data as holotype, AMS K.377776 (in alcohol) ; ♂ ( HW 1.40 ) same data as holotype, K.377777 (on two slides) ; 10 specimens ( HW not recorded) same data as holotype, K.377778 (in alcohol) ; 78 specimens, mostly subadult and juvenile ( HW not recorded), same data as holotype, AMS K.377779 (in alcohol) ; 1♂ ( HW 1.43 ) Mungo National Park , Mungo National Park, Garnpang House 33.490°S 143.101°E, 31.viii.2017, J. Tann, bark spray, AMS K.377780 (on two slides) ; 1♂ ( HW 1.55 ) same data as previous, AMS K.377781 (in alcohol) ; 27 specimens ( HW not recorded) same data as previous, AMS K.377782 (in alcohol) ; 1♀ ( HW 1.60 ) Mungo National Park 33.355°S 143.139°E, 31.viii.2017, J. Tann, bark spray, AMS K.377784 (on two slides) ; 1♂ 1♀ ( HW not recorded), same data as previous, AMS K.377785 (in alcohol) ; 1♂ ( HW 1.50 ) Mungo National Park , Leaghur Tank 33.618°S 143.034°E, viii.2017, J. Tann, bark spray, AMS K.377788 (on two slides) ; six specimens ( HW not recorded) same data as previous,AMS K.377789 (in alcohol) ; 1♂ ( HW 1.28 ) Mungo National Park , SS1 33.632°S 143.031°E, 28.viii.2017, J. Tann, bark spray, AMS K.377790 (in alcohol) .

Additional material examined but not included in type series. 1 juvenile ♀ ( HW 0.75) NEW SOUTH WALES: Jerilderie 35.34730°S 145.60062°E 104m asl, 5.xi.2014, Graeme Smith, leaf litter,AMS K.377977 (in alcohol) ; six juvenile specimens ( HW not recorded) same data as previous, AMS K.377978 (in alcohol) ; 1 subadult ♂ ( HW 0.81) Jerilderie , 35.34721°S 145.60028°E 107m asl, 5.xi.2014, Graeme Smith, bark spray to old Eucalypt, AMS K.541638 (on slide) ; 1♂ ( HW 1.13 ) ca. 40km east of Hay 34.50587°S 145.23440°E 97m asl, 22.ix.2013, Graeme Smith, bark spray to River Red Gum ,AMS K.261259 (on two slides) ; 1♂ ( HW 1.18 ) same data as previous,AMS K.377975 (in alcohol) ; 2♂♂ 1♀ 2 juvenile ♀♀ specimens ( HW not recorded) same data as previous, AMS K.377976 (in alcohol) .

Diagnosis. This species can be distinguished from other described Acrotelsella with a simple ovipositor by a combination of characters including, the number of papillae on the apical article of the labial palp (five), the presence of two macrochaetae mediad of the anterior trichobothrium and three laterad of the posterior trichobothrium of the pronotum (at least in mature specimens) versus only one and two respectively, the parabolic shape of the thoracic sternites with 5–8 combs along about ⅔ of the margin of the prosternum each of which is more or less in a single line (versus complex overlapping lines in A. parlevar ), (2–3)+(2–3) in the mesosternum and (1–2)+(1–2) on the metasternum and the sexual dichotomy of the angle of the quite pointed urotergite X (40° in females and 50–58° in the males).

Description

Appearance: Medium to large silverfish, with narrow body, thorax not much wider than the abdomen which only tapers slightly posteriorly. Scale pattern when live see Figure 125 , in alcohol mottled brown.

Body length: H+B up to 10.8 mm, HW 1.73 mm; thorax: length 3.5 mm or 0.27–0.33 H+B; width 2.73 mm with the mesonotum being slightly wider than the pronotum and metanotum, the metanotum being slightly shorter than the pro- and mesonota. Antennae incomplete, maximum preserved length 9.6 mm or>0.9 H+B; terminal filaments all broken, maximum length of terminal filaments 7.9 mm or>0.79 H+B.

Pigmentation: Flagellum of antennae without annulations, light brown pigment evenly distributed; pedicel with patch of pigment on anterior face, scape without pigment. Frons with pigment around the eyes and among the macrochaetae anterior to the eyes, labrum and clypeus without pigment, mandibles and maxillae without pigment among bushes of macrochaetae, ultimate article of maxillary palp with very slight pigment except basally, penultimate article with some pigment evenly distributed, third article with slightly more pigment, second article with a little pigment above; labial palp without pigment. Nota and thoracic sterna without obvious pigment. Coxae of legs without pigment. Trochanter with faint pigment along posterior margin especially distally. Femora with slight pigment along posterior bulge and distally on the outer margin. Tibia with light pigment over much of outer face, more so distally. First tarsal article with a little blotchy pigment above, remaining articles without pigment. Abdominal segments without obvious pigment except for light pigment on coxites IX. Ovipositor largely without pigment except for a light scattering of pigment distally. Cerci and median filament with moderate brown pigment overall, except lighter around the distal most annulus of each division bearing the large macrochaetae, this lighter area can be less prominent in some individuals. Abdominal styli with light pigment. Some males (e.g., K.377777 and K.377780) with more pigment, especially noticeable in posterior abdominal sternites and edges of tergites.

Macrochaetae: Variable, pectinate ( Fig. 126 ) or smooth, straw coloured.

Scales: Variable in shape, with numerous sub-parallel ribs that do not surpass the margin of the scale ( Fig. 127 ), those dorsal brown, those ventral hyaline. Scales found on top of head, on scape, on second and third articles of maxillary palp, on mentum of labium, all nota, all thoracic sterna, legs (except for trochanter and last three articles of tarsi), all urotergites and urosternites, styli and terminal filaments.

Head: ( Fig. 128 ) wider than long, with 1+1 not very dense bushes of macrochaetae aligned in subparallel rows on the antero-lateral corners. Eyes dark brown in alcohol preserved material. There is a small gap in the row of macrochaetae along the margin above the antennal bases behind which is another row of macrochaetae 2–3 wide which extends to and above the eyes; the peri-antennal group is almost connected with the lateral rows. Clypeus with 1+1 very dense bushes of strongly pectinate macrochaetae as well as a few curved setae laterally. Labrum also with 1+1 dense bushes of pectinate macrochaetae as well as many simple setae, some longer than others. — Antennae fairly long, scape ( Fig. 129 ) quite long with scales over surface and a preapical ring of numerous setae; pedicel with preapical ring of strong simple setae and cilia as well as smaller setae in a ring about half way along the face and an incomplete ring in the distal third as well as some small scattered setae over face; first annulus/interval of flagellum with an incomplete subapical ring of simple setae and about two trichobothria; next annulus with two rings of simple setae each with about two trichobothria which probably represents an annuli in the process of dividing; subsequent intervals with single ring of setae and cilia across the middle of the annulus and two short trichobothria per annulus. Intervals of flagellum subdivided into two from the ninth interval and further into three then four from the 13th interval. Distally it is difficult to decide how many annuli per interval ( Fig. 130 ), trichobothria are seen every 11th of 12 annuli but circular sensilla are seen on the eighth and on other specimens there appears to be two circular sensilla on adjacent annuli around the middle of the interval, the more distal being larger than the more proximal with the most distal annulus bearing a proximal ring of setae and a subapical ring of cilia and a trichobothrium. — Mandibles ( Figs 131, 132 ) typical for Acrotelsella with prominent molar and large incisor areas; a group of about nine strong apically bifurcated but simple setae distally adjacent to the pectinate molar area and a bush of extremely numerous and densely packed pectinate macrochaetae externally as well as scattered simple setae. — Maxilla ( Fig. 133 ) with two thicker, smooth or slightly pectinate 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 4–9 smooth setae, those nearest the lamellate processes shorter and conical in shape, galea longer than the lacinia with 4–6 strong, smooth, simple or apically bifurcate setae externally in its basal half and several cilia distally ( Fig. 134 ); maxillary palp very long and thin, apical article 6.1–7.4 times longer than wide and 0.86–1.07 times as long as the penultimate article which is 0.87 times as long as the third and longest article, the ultimate article with a circular sensillum subapically appearing like a “sensillum of Silvestri” (sensu Mendes, 1986a) with a protruding lobe or sometimes could not be seen; last two articles of palp with fine setae only, third article with one slightly stronger seta subapically, first and second articles with subapical ring of slightly thicker setae, the ring incomplete on the basal article. — Labium ( Fig. 136 ) very short and broad, postmentum with transverse row of simple and truncate, apically bifurcate macrochaetae, prementum with transverse and oblique rows of short strong apically bifurcated setae, apically with long curved setulae; labial palp short, the second article quite slender with several strong setae; apical article expanded medially, a little shorter than long (0.77–1.04) with row of five papillae of compact type arranged in a single row near the outer margin, with a single (?) circular walled basiconic sensillum and at least one rod-like basiconic sensillum (type B) on the outer margin, covered with numerous fine setae as well as longer fine setae.

Thorax: Pronotum ( Fig. 137 ) with dense setal collar about three macrochaetae wide, with very slight gap medially, some macrochaetae very long and strongly pectinate in outer quarter, others shorter with subtle pectinations; lateral margins with a few setae along the margin, those still present with very subtle pectinations or even appearing completely smooth (especially posteriorly), with 7–8 combs of 1–3 strongly pectinate macrochaetae along each margin. Two open trichobothrial areas; the anterior trichobothrial area ( Fig. 138 ) about 0.28–0.37 of the distance along the margin, associated with comb N-3, the trichobothrium being placed between the comb of 1–2 macrochaetae and the margin; posterior trichobothrial area is located about 0.70–0.75 of the distance along the margin and is associated with the last comb which is composed of three macrochaetae with the short trichobothrium at the mediad end and a cilium at the laterad end, all combs associated with a several setulae. Posterior margin with 1+1 combs of 3–8 insertion points associated with a few small setae between the comb and the margin and a cilium at each end; on K.377780 and K.377777, the outermost insertion on the comb is occupied by a long thin trichobothria-like seta (about as long as ⅔ the length of the nota), presumably this is the case in all other specimens where the combs have been lost (also the case with K.377788 on the metanotum). Distance between the posterior combs 41–49% of the width of the pronotum. — Mesonotum ( Fig. 139 ) with lateral chaetotaxy similar to pronotum but with 9–12 combs each of 2–5 macrochaetae (rarely 1, in a juvenile specimen), the anterior trichobothrial area located 0.56–0.61 along the lateral margin associated with comb N-2 composed of 2–3 macrochaetae with the trichobothrium located between the macrochaetae and the margin, with several setulae posterior to the comb and a cilium at the mediad end. Posterior trichobothrial area slightly more posterior than that on the pronotum (0.81–0.83), the trichobothrium located mediad to the comb of 2–3 macrochaetae and with several setulae posterior to the comb. Posterior margin with 1+1 combs of 4–9 insertions usually with a cilium at the mediad end, the most lateral macrochaeta most likely a long, thin, trichobothrium-like seta, with a few setulae between the comb and the margin. — Metanotum ( Fig. 140 ) similar to mesonotum with 8–10 combs of 2–4 macrochaetae (rarely 1–3), the anterior trichobothrial area associated with comb N-1 of two macrochaetae about 0.70–0.72 along the margin, the posterior trichobothrial area associated with the most posterior comb and the posterior 1+1 combs each of 6–8 insertions the most lateral macrochaeta being a long, thin, trichobothrium-like, with a few setulae between the comb and the margin ( Fig. 141 ).

Presternum very narrow, with transverse row of cilia and setulae ( Fig. 142 ). — Prothoracic sternum ( Fig. 142 ) large, almost as long as the coxa, 0.98–1.05 times as long as wide at its base, parabolic, rounded/sometimes slightly flattened apically, antero-lateral corners with about 20 simple small setae, posterior two thirds of lateral margins with fringe of setae and some cilia as well as 5–8 combs each composed of 2–11 pectinate macrochaetae arranged in curved combs in a single line, although an occasional macrochaeta can be found slightly off-set from the rest. — Mesosternum ( Figs 143, 144 ) a little larger than prosternum (1.1–1.2 times as long) but similar in shape, about a long as wide at its base (L/ W 0.90 –1.02), with or without fine setae in the anterolateral corners, with long, thin simple marginal setae and cilia along the posterior quarter of the lateral margins and 2+2 or 2+3 combs distally, the more anterior composed of 6–11 strongly pectinate macrochaetae, the next of 2–7 macrochaetae and the most distal of 1–3 pectinate or smooth macrochaetae, the more anterior combs with several setulae spread over the region distal to each comb. — Metasternum ( Figs 145, 146 ) shorter and wider than the mesosternum (L/ W 0.75 –0.81) apically rounded, the margins may be slightly concave adjacent to the posterior combs, with marginal setae and cilia along distal margins adjacent to the combs as well as several setulae between the combs and the margin; 1+1, 1+2 or 2+2 subdistal combs of 6–14 strongly pectinate macrochaetae.

Legs of average dimensions, neither long and slender nor short and stout, tibia L/W ratio of PI 2.8 (range 2.5–3.1), PII 3.3 (range 3.0–3.5), PIII 4.0 (range 3.5–4.5); tarsi L/W ratio PI 6.5 (range 5.9–7.0), PII 7.1 (range 6.7–7.2), PIII 8.9 (range 8.1–9.6). PI ( Fig. 142 ) with a row of about seven macrochaetae laterally on the precoxa. Coxa with scales and a group of about ten macrochaetae on the anterolateral corners followed by a field of pectinate macrochaetae along the external margin about three macrochaetae wide; inner margin with a four lightly pectinate macrochaetae and several smooth and pectinate setae of varying thickness distally over the articulation; distal end with distinct cleft, with a row of small setae insertions along the mediad margin. Trochanter with a few strong smooth setae. Femur posteriorly with three slender pectinate macrochaetae, in addition to many robust smooth setae along the margin to the posterior bulge then a row of about 12 setae along the margin to the articulation; anterior edge with one strong macrochaeta about ⅔ along the margin and at least three pectinate macrochaetae over the articulation. Tibia of PI with three stout, carrot-shaped, pectinate macrochaetae along the posterior margin as well as several longer, thinner, pectinate or smooth setae and a row of shorter stout setae near the distal margin; anterior margin with two pectinate macrochaetae as well several subdistal setae over the articulation, dorsal surface with a subdistal row of setae; apex of tibia with the usual apical spur which is covered in numerous setae. Tarsi with four articles, the basal article of PI about half the total length of the tarsus, its join with the next article not particularly oblique, whereas the distal margin of the second article is more oblique, the surface of all tarsal articles with very numerous simple setae. Pretarsus with two long curved lateral claws and a shorter curved medial claw. PII ( Fig. 143 ) and PIII ( Fig. 145 ) similar to PI except the macrochaetae laterally on the coxae are much reduced in the anterior half; the tibia of PIII appears to have more pectinate carrot-shaped macrochaetae than the other legs, tibia of PIII with a long trichobothria-like seta about ¼ the distance along the outer margin: legs progressively longer from PI to PIII and the relative length of the basal tarsal article is progressively longer, being about 60% of the total length of the tarsus of PIII.

Abdomen: Urotergite I with 1+1 lateral combs of 4–7 macrochaetae each associated with a cilium at each end and several setulae between the comb and the margin, usually but not always more numerous than the macrochaetae, urotergites II–VII with 3+3 combs of 4–13 macrochaetae as in Table 7 ( Fig. 148 ), the smallest mounted specimen having the least, urotergite VIII with 2+2 combs (lacking the sublateral), urotergite IX glabrous, rarely with a small marginal seta in the infralateral position (e.g., K.377780); all combs with a cilium at each end and usually but not always more setulae than macrochaetae between the comb and the margin. — Urotergite X ( Fig. 149 ) acutely triangular (40° in females, 50–58° in males), slightly wider at base than long (L/ W 0.61 –0.87) with many smooth setae along entire margin both above and 4–5 combs on each side, the combs composed of 1–7 macrochaetae per comb usually with a cilium at the mediad end of each comb, as well as several setulae posterior to each comb.

Urosternite I and II glabrous, urosternites III–VII with 1+1 lateral combs of 9–18 pectinate macrochaetae ( Figs 150, 151 ) each with a similar number of setulae between the comb and the margin as well as a cilium at the lateral end of every comb; the smallest mounted specimen always at the lower end of the range. The distance between the lateral combs 2.7–8.4 times the average width of these combs, the ratio being largest on urosternite III and decreasing posteriorly; the ratios are largest on smaller specimens because the number of setae in the combs is less than in mature specimens.

Genital region of ♀ as in Figure 152 . Two pairs of styli, those on IX about one third longer than those on VIII, with some robust setae apically, stylus lost or deformed in holotype. Coxites VIII with long combs of 5–16 macrochaetae (deformed on right side of holotype with only six insertions) and a similar number of setulae between the comb and the margin, the coxites with rounded inner corners. Coxites IX with long rounded internal process, about 3.9–4.8 times longer than wide at its base and 8.3–11.9 times longer than the short pointed external process, the inner processes just surpassing the apex of styli IX including macrochaetae, reaching to about the end of the ovipositor; outer process with several strong setae externally, inner process with strong smooth macrochaetae along the margins, being very dense on the outer margin where many scales also exist. — Ovipositor ( Figs 152, 153 ) not very long (1.45–1.60 HW), reaching to the apex of the long internal processes of coxites IX, both pairs of gonapophyses consisting of long basal division followed by smaller divisions that do not differ greatly in their length along the ovipositor, 19–21 divisions in total; of primary type with rows of fine setae on each article.

Cerci ( Figs 154, 155 ) first division almost glabrous, with just a couple of minute setae near the lateral margin; following four basal divisions about as long as wide with three or four rings of setae, macrochaetae and trichobothria, the middle and also most basal ring with some small scales; divisions then progressively longer with four annuli per division each with one or two rings of setae and macrochaetae, trichobothria absent from the two rings of the most distal annuli and very small in the basal annulus; scales present up until the 13th division, at least on some specimens, in the penultimate ring of each division; most distal surviving division with about eight ill-defined annuli with a total of 12 rings of chaetotaxy, the most basal with two very small trichobothria, the sixth and seventh with long trichobothria, larger pectinate macrochaetae restricted to the most distal ring. — Median dorsal appendage ( Fig. 154 ) first division glabrous; second division very short with only a couple of small setae laterally on each side; following three divisions with 2–3 rings of setae and trichobothria, scales present on basal and middle rings, scales present some basal divisions. Epiproct and paraprocts very darkly sclerotized.

Urosternite VIII in ♂ entire ( Fig. 156 ) with 1+1 combs of 13–14 macrochaetae as well as 2–5 thin marginal setae and several setulae. Coxites IX in ♂ separated each side with a long macrochaeta (about ⅔ the length of the internal process) mediad to the base of the stylus. The internal process very acute apically about 3.1–4.0 times longer than the external process and 1.2–1.6 times as long as broad at its base. External and internal margins of internal process and external margin of outer process with many moderately strong setae and macrochaetae. Outer process small triangular with several stout pectinate setae along the outer margin. Penis typical with numerous glandular setae apically, each set on a protuberance. Parameres absent.

Habitat. This species was mostly collected by spraying the bark of trees, usually the bottom 1.5 m. At Jerilderie, the species was collected from leaf litter.

Etymology. The species is named for the collector John Tann, formerly of the Australian Museum.

Remarks

The molecular data places this species close to A. thommoi sp. nov. and A. parlevar . It is easily distinguished from both of these by the presence of five papillae on the ultimate article of the labial palp versus three in the other two species. Due to the poor descriptions of other species such as A. silvestri Womersley from Kangaroo Island and A. sinensis Silvestri from China, which also have five papillae and simple ovipositors, it is difficult to make conclusive comments. Acrotelsella silvestri appears to have more combs of fewer macrochaetae on the metathoracic sternum (2+3 of 3–6 versus 1+2 of 6–14 macrochaetae) and A sinensis appears to have fewer lateral combs on the nota (6–8 versus 8–11) however these species need to be redescribed in more detail to complete the character set used here and to understand the intraspecific variability.

Figures

Figure 124. Known distribution of Acrotelsella tanni sp. nov.

Figure 125. Acrotelsella tanni sp. nov., Hay

Figures 126–136. Acrotelsellatanni sp. nov.holotype ♀ (126) long pectinate macrochaeta of head; (127) darker dorsal scale of mesonotum; (128) head (cross-hatched area obscured by eye pigment); (129) antenna, scape, pedicel and basal intervals of flagellum; (130) idem, most distal surviving complete interval; (131) mandible; (132) idem, molar and incisor region; (133) maxilla; (134) idem, lacinia and galea; (135) idem, apex of ultimate article of palp; (136) labium. cs = circular sensillum. Scale bars = 0.1 mm.

Figures 137–144. Acrotelsella tanni sp. nov. holotype ♀ unless otherwise indicated by specimen number (137) pronotum; (138) idem, right anterior trichobothrial area; (139) mesonotum; (140) metanotum; (141) idem, right posterior comb (K.377788); (142) presternum, prothoracic sternum; (143) mesothoracic sternum; (144) combs of mesosternum. Scale bars = 0.1 mm.

Figures 145–151. Acrotelsella tanni sp. nov. holotype ♀ (145) metathoracic sternum and PIII; (146) combs of metasternum; (147) urotergite VII; (148) idem, right combs; (149) urotergite X; (150) urosternite VII; (151) left comb of urosternite IV. Scale bars = 0.1 mm.

Figures 152–156. Acrotelsella tanni sp. nov. holotype ♀ unless otherwise indicated by specimen number (152) left coxites VIII and IX with ovipositor; (153) apex of gonapophyses; (154) base of cerci and medial filament; (155) cercus, most distal surviving divisions; (156) urosternite VIII, coxites IX and penis of male (K.377777). Scale bars = 0.1 mm.