Acrotelsella auricoronata, 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 : 173-180

Acrotelsella auricoronata sp. nov.

urn:lsid:zoobank.org:pub:63665A69-2C2D-4CA5-8D42-12135EF442FD

Figs 67–97

Holotype ♀ ( HW 1.40 ) NEW SOUTH WALES: rest area about 15km west of Balranald 34.62276°S 143.40124°E 58m asl, 9.vii.2016, Graeme Smith, bark spray,AMS K.541640 (on two slides) . Paratypes 1♀ ( HW 1.31 ) same data as holotype,AMS K.541641 (on two slides) ; 1♀ ( HW 1.38 ) same data as holotype, AMS K.261337 (on two slides) ; 1♀ ( HW 1.25 ) same data as holotype, AMS K.261338 (on two slides) ; 1♀ ( HW 1.20 ) same data as holotype, AMS K.541642 (on two slides) ; 3♀♀ 1 juvenile ♀ 4 juveniles ( HW not recorded), same data as holotype, AMS K.377979 (in alcohol) .

Other material not included in type series. 1♀ ( HW 1.35 ) NEW SOUTH WALES: Mungo National Park, Garnpang House 33.490°S 143.101°E, 31.viii.2017, John Tann, bark spray, AMS K.377783 (on two slides) ; 1♀ ( HW 1.28 ) Mungo National Park 33.355°S 143.139°E, 31.viii.2017, John Tann, bark spray, AMS K.377786 (on two slides) ; 1♀ ( HW 1.15 ) same data as previous, AMS K.377787 (in alcohol) ; 1♀ ( HW 1.10 ) Mungo National Park SS2 33.6541°S 143.197°E, 28.viii.2017, John Tann, bark spray, AMS K.377791 (in alcohol) ; 1♀ ( HW 1.18 ) ca 15km south of Balranald 34.76588°S 143.53964°E 72m asl, 23.ix.2013, Graeme Smith, bark spray to flaky bark mallee, K.377984 (in alcohol) ; 1 juvenile ♀ ( HW not recorded), same data as previous K.261261 (on two slides) ; 1♀ ( HW 1.25 ) QUEENSLAND: ca 2km east of Old Cork Homestead , 22.92163°S 141.91291°E 142m asl, 10.viii.2013, Graeme & Louise Smith, bark spray to rough bark tree, AMS K.377981 (in alcohol) ; 1 juvenile ♀ ( HW 0.90), same data as previous, AMS K.261297 (on two slides) ; 2 juveniles ( HW not recorded), same data as previous, AMS K.377982 (in alcohol) ; 1 juvenile ♀ ( HW 0.83) 1km east of Tambo 24.87411°S 146.25423°E 395m asl, 13.viii.2013, Graeme Smith, bark spray to gidgee, AMS K.261326 (on slide) ; 1 juvenile ♀ ( HW 0.95) 2 juveniles ( HW not recorded), same data as previous, AMS K.377983 (in alcohol) ; 1♀ ( HW 1.33 ) SOUTH AUSTRALIA: Arkaroola , near spring track 30.28783°S 139.34311°E 300m asl, 16.v.2012, Graeme Smith, under bark of paper bark, AMS K.377980 (in alcohol) ; 1♀ ( HW 1.13 ) VICTORIA: Hattah-Kulkyne N.P. gate in kangaroo fence 34.68028°S 142.34957°E 57m asl, 24.ix.2013, Graeme Smith, bark spray to mallee/ Eucalypt,AMS K.377985 (in alcohol) ; 1♀ ( HW 1.13 ) same data as previous ; NMV gbs004034 (in alcohol); 1♀ ( HW 1.35 ) Hattah 34.75319°S 142.26925°E 46m asl, 25.ix.2013, Graeme Smith, bark spray to Eucalypt,AMS K.377986 (in alcohol) ; 1♀ ( HW 1.15 ) same data as previous, AMS K.261278 (on slide) ; 1♀ ( HW 1.13 ) Walpeup 35.14048°S 142.01538°E 110m asl, 25.ix.2013, Graeme Smith, bark spray to rough bark mallee, NMV gbs004044 (in alcohol) ; 1♀ ( HW 1.25 ) Murray-Sunset N.P. start of Mt Crosby track 35.03393°S 141.75685°E 47m asl, 26.ix.2013, Graeme Smith, bark spray to woollybutt mallee, AMS K. 377987 (in alcohol) ; 1♀ ( HW 1.10 ) Wyperfeld N.P.Casuarina campground 35.44543°S 141.99451°E 63m asl, 27.ix.2013, Graeme Smith, bark spray to Casuarina, AMS K.377988 (in alcohol) .

Diagnosis. This species can easily be distinguished in the field from other described Acrotelsella by the ring of golden coloured scales on the frons ( Fig. 68 ). Preserved specimens are distinguished by the trapezoidal shape of the thoracic sterna with the combs restricted to the posterior half of the prosternum and the presence of only 1+1 combs on the mesosternum, by the presence of only three papillae on the last article of the labial palp, the elongate processes of coxites IX of the female, the curved shape of the medial posterior margin of coxites VIII in the female, the presence of a trichobothrium in the most laterad insertion socket of the posterior combs of the nota and from Acrotelsella escherichi by the primary type ovipositor (versus secondary).

Description

Appearance: Medium to large silverfish, with narrow body, thorax not much wider than the abdomen which only tapers slightly posteriorly ( Fig. 68 ). Scale pattern when live overall dark grey or mottled when scales are lost, conspicuous circle of golden scales on frons in specimens with little wear and tear and a light margin to urotergite X, legs dark above, antennae distinctly banded especially in basal half, terminal filaments overall dark brown with small lighter regions at the distal end of each division. In alcohol mottled brown.

Body length: H+B up to 10.4 mm (♀), HW up to 1.40 mm; thorax: length 2.8 mm or 0.26–0.32 H+B; width 2.2 mm with the pro- and meso-nota being slightly narrower and shorter than the mesonotum; antennae incomplete, maximum preserved length 5.8 mm or>0.6 H+B; terminal filaments all broken, maximum length of cercus 6.8 mm or>0.7 H+B; median dorsal appendage maximum length 7.9 mm (>0.8 H+B).

Pigmentation: Antennae distinctly banded, orange-brown pigment in distal half of each interval, annulations becoming less distinct distally as the lighter regions become progressively darker; pigment absent from pedicel and scape. Frons without pigment, even around the eyes, clypeus and frons with strong brown pigment among and below the sublateral groups of macrochaetae, mandibles and maxillae with strong pigment among bushes of macrochaetae, maxillary palp with moderate dark pigment on apical article except lighter at base, penultimate article dark in the distal ½–¾, 2nd and 3rd articles with medium pigment along sides; labial palp ultimate article with light to strong pigment around the margins, penultimate article with light to strong pigment on sides, strongest distally, 2nd article with dark patch of pigment on inner apical corner and sometimes a little around the whole distal region. Nota and thoracic sterna without obvious pigment. Precoxa of legs sometimes with blotchy brown pigment but sometimes without, coxae with some pigment in the antero-lateral “shoulders” weakly extending along outer margin but sometimes very faint of absent. Trochanter with patch of dark pigment along outer margin especially distally. Femora with dark patch over posterior bulge and distally on outer margin. Tibia with dark pigment distally on outer half. Tarsi with some blotchy pigment on all articles the basal article with quite dark patch.Abdominal segments without obvious pigment except for light pigment over urotergite X except along its margins. Styli with light orange-brown pigment. Ovipositor largely without pigment except for a light scattering of pigment distally. Cerci and median filament distinctly banded in K.377783 with only the basal and distal annuli of each division lacking pigment, K.377786 and holotype almost completely dark except for lighter pigment around distal macrochaetae of each division.

Macrochaetae: Variable, pectinate but not strongly so, some smooth ( Figs 69–71 ), hyaline to dark brown.

Scales: With numerous sub-parallel ribs that do not surpass the margin of the scale ( Fig. 72 ), those dorsal are brown, those ventral hyaline. Scales found on top of head, on scape, on second and third articles of maxillary palp, all nota, all thoracic sterna, legs (except for trochanter and distal three articles of tarsi), all urotergites and urosternites, styli IX, medial filament and cerci.

Head: ( Fig. 73 ) wider than long, with 1+1 moderately 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 after which there is another bush of pectinate macrochaetae, three or four macrochaetae wide extending along the sides and above the eye; the peri-antennal group is small, of only five to six sockets, but more or less isolated by a small gap from the marginal chaetotaxy. Clypeus with 1+1 very dense bushes of strongly pectinate macrochaetae as well as a few curved setae. Labrum also with 1+1 distinct but less dense bushes of pectinate macrochaetae as well as two or three longer thin setae between the groups. — Antennae fairly long, scape ( Fig. 74 ) quite long with scales over surface laterally and a preapical ring of numerous setae; pedicel with preapical ring of simple setae and cilia as well as setae scattered over face; all subsequent annuli of flagellum similar with single ring of simple setae, cilia and trichobothria; obvious subdivision into annuli and intervals is very difficult to interpret in all dissected specimens. Distal intervals insufficiently preserved. — Mandibles ( Fig. 75 ) typical for Acrotelsella with well-developed molar and incisor areas; a group of about ten stout apically bifurcated but simple setae distally adjacent to the pectinate molar area and a bush of about 90 pectinate macrochaetae externally. — Maxilla ( Fig. 76 ) with two thick minutely apically bifurcated and faintly pectinate macrochaetae externally proximal to the palp, the lacinia with three strong teeth, one set further back than the other two, followed by several lamellate processes and a row of ten thin simple setae, those nearest the lamellate processes only slightly smaller than the others, galea slightly longer than lacinia with about six strong, smooth, simple or apically bifurcate setae externally in its basal half and several cilia distally; maxillary palp not very long and thin, apical article ( Fig. 77 ) four times longer than wide (range 3.9–4.6) and 1.3 times as long as the penultimate article (range 1.0–1.5), and 0.9 times as long as the third and longest article, the ultimate article possibly with a very small sausage-shaped sensilla subapically (thin-walled basiconic sensillum type C), basal article with a field of strong setae, second and third articles with subapical ring of slightly stronger setae subdistally, penultimate article with one stronger seta. — Labium ( Fig. 78 ) short and broad, postmentum with transverse row of apically bifurcate setae, prementum with transverse and oblique rows of short strong mostly apically bifurcated setae, apically with long curved cilia and setulae; labial palp short, apical article expanded subrectangular, a little shorter than long (0.82–1.06) with row of only three papillae of compact type arranged in a single row near the outer margin, no other sensilla seen, covered with numerous fine setae as well as longer fine setae.

Thorax: Pronotum ( Fig. 79 ) with setal collar about one to three pectinate macrochaetae wide, without gap medially; lateral margins with strong, only vaguely pectinate setae along the margin, with eight combs of one to three pectinate macrochaetae along each margin. Two open trichobothrial areas; the anterior trichobothrial area ( Fig. 80 ) located 0.34–0.42 along the margin associated with comb N-3, the comb composed of only a single macrochaeta with the trichobothrium between the macrochaeta and the margin and a cilium at the mediad side of the macrochaeta; the posterior trichobothrial area ( Fig. 81 ) is located 0.77 of the distance along the margin (range 0.75–0.81) and is associated with the last comb (N), this comb composed of just a single macrochaeta with the trichobothrium at the mediad end and a cilium at the laterad end; all combs associated with a few setulae. Posterior margin of all nota with 1+1 combs of 3–5 macrochaetae and a long trichobothrium-like hair in the insertion at the lateral end and contiguous with the comb of macrochaetae, with a cilium at each end of the comb and a few setae between the comb and the margin ( Fig. 82 ). Gap between the posterior combs 50–55% of the width of the pronotum. — Mesonotum ( Fig. 83 ) with lateral chaetotaxy similar to pronotum with 9–10 combs of 1–3 macrochaetae each associated with a few setulae and a cilium, the anterior trichobothrial area located 0.65 along the lateral margin associated with comb N-2 composed of a single macrochaeta with the trichobothrium located between the macrochaeta and the margin. Posterior trichobothrial area located 0.87 along the margin, the trichobothrium located mediad to the comb of a single macrochaeta. — Metanotum ( Fig. 84 ) similar to mesonotum with 8–10 combs of 1–3 macrochaetae, the anterior trichobothrial area is located 0.76 the distance along the margin associated with comb N-1 (rarely N-2) which has just a single macrochaeta, the posterior trichobothrial area associated with the most posterior comb 0.88 along the margin.

Presternum with transverse row of setae ( Fig. 85 ). — Prothoracic sternum ( Fig. 85 ) large, reaching to about ⅔ the length of the coxa, 0.93 times as long as wide at its base (range 0.87–1.02), trapezoidal with concave posterior margin, antero-lateral corners with about 12 simple but robust marginal setae, posterior ⅓ to ½ of lateral margins with marginal setae, posterior margin glabrous; each side with 3–4 short combs of 1–5 pectinate macrochaetae not much longer than the marginal setae. — Mesosternum ( Fig. 86 ) a little larger than prosternum (1.2 times as long), 0.93 times as long as wide at its base (range 0.84–0.94), with a few fine setae in the anterolateral corners and long, thin simple marginal setae only in the postero-lateral corners near the 1+1, 1+2 or 2+2 combs close together, whose 1–6 pectinate macrochaetae are generally shorter than the smooth marginal setae. — Metasternum ( Fig. 87 ) of similar length and shape to prosternum but much wider (about 1.3 times wider than long (L/W range 0.71–0.79) with 0–1 strong setae in anterior corners and long marginal setae adjacent to 1+1 combs only, these setae can be longer than the macrochaetae of the combs, combs of 2–5 pectinate macrochaetae.

Legs strong, tibia L/W ratio of legs PI 2.6 (range 2.4–2.9), PII 3.0 (range 2.9–3.1), PIII 4.0 (range 3.6–4.2); tarsi L/W ratio PI 5.7 (range 4.8–6.6), PII 7.2 (range 6.5–7.9), PIII 8.5 (range 7.7–10.1). PI ( Fig. 85 ) with a row of six macrochaetae laterally on the margin of the precoxa. Coxa with scales and a group of about seven macrochaetae on the anterolateral corners followed by a field of strong pectinate macrochaetae along the external margin about 2–3 macrochaetae wide; inner margin with a four or five long lightly pectinate macrochaetae and about ten setae of varying thickness distally over the articulation and along the distal margin. Trochanter with a few long setae. Femur posteriorly with about five long but not thick, pectinate macrochaetae, in addition to simple setae along the margin and just a single macrochaeta on the dorsal or anterior margin. Tibia of PI quite short with just two carrot-shaped, slightly pectinate macrochaetae along the posterior margin (one near each end of the margin) as well as several longer, thinner, pectinate or smooth setae and a row of shorter setae near the distal margin; anterior margin with one or two macrochaetae as well as 3–4 subdistal macrochaetae over the articulation; apex of tibia with robust 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, the surface of all tarsal articles with numerous simple setae, the second article on both PI legs appearing to have a raised oval area basally (sensilla?). Pretarsus with two long curved lateral claws and a shorter curved medial claw. PII and PIII ( Fig. 87 ) similar to PI except the antero-lateral groups of macrochaetae on the coxa reduced to a single macrochaeta on PII, with six strong macrochaetae on the internal margin of the coxa of PII; legs progressively longer from PI to PIII and the relative length of the basal tarsal article is progressively longer, being about two thirds of the total length on PIII. Tibia of PIII with long thin trichobothrium-like seta about 40% along the outer side, twice as long as tibia is wide; second article of tarsi without raised oval area.

Abdomen: Urotergite I with 1+1 lateral combs of 5–6 macrochaetae each associated with a cilium at either end and several setulae between the comb and the margin, urotergites II–VII with 3+3 combs of macrochaetae as in Table 5 ( Figs 88–91 ), urotergite VIII with 2+2 combs (lacking the sublateral), urotergite IX glabrous; all combs usually with a cilium at either end and a similar or slightly larger number of setulae as macrochaetae between the comb and the margin. — Urotergite X ( Fig. 92 ) equilaterally triangular (56–68°), wider at base than long (L/ W 0.49 –0.64) with many pectinate setae along entire margin both above and below, and (4–5)+(4–6) combs of 1–4 macrochaetae per comb (all lost) without obvious setulae posterior to each comb, and most combs with a cilium at the mediad end.

Urosternite I and II glabrous, urosternites III–VII with 1+1 sublateral combs of 5–11 pectinate macrochaetae ( Figs 93, 94 ) each with 4–8 setae or setulae between the comb and the margin as well as a cilium at the laterad end of each comb only. The distance between the lateral combs 7.4–21.2 times the average width of these combs, the ratio being largest on urosternite III and decreasing posteriorly.

Genital region of ♀ as in Figure 95 . Two pairs of styli. Coxites VIII with combs of 8–9 macrochaetae 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 2.8–4.7 times longer than wide at its base and about 7–10 times longer than the short pointed external process, the inner processes reaching to the apex of the ovipositor; outer process with setulae along the inner margin and several strong finely pectinate setae externally, inner process with numerous long finely pectinate macrochaetae along the outer margins as well as many scales, inner margin of process with setae insertions and many small setae basally. — Ovipositor ( Figs 95, 96 ) not very long, (1.9 HW range 1.7–2.2), only just surpassing the apex of the long internal processes of coxites IX, about 25–30 divisions in total; of primary type with long and fine short setae only.

Cerci ( Fig. 97 ) first division with two partial rings of small setae, following two basal divisions shorter than wide with a single ring of small setae, cilia and several trichobothria, division four with two rings, the most basal of probably of scales only, the more distal of trichobothria, stronger setae, cilia and small macrochaetae; divisions five and six with three rings, the most basal of scales and trichobothria, the middle with scales only and the most distal as on the previous division; division seven with four rings, the most basal and third rings of scales with perhaps some trichobothria, the second of setae, trichobothria and cilia but smaller than those of the most distal ring; division eight with six rings with the basal, third, fourth and fifth of scales and perhaps some trichobothria, the second with stronger seta, trichobothria and some macrochaetae, the most distal with strong macrochaetae, cilia and setae, possibly without trichobothria. — Median dorsal appendage ( Fig. 97 ), first division short and glabrous, following three divisions each with single ring of setae and trichobothria, fifth and sixth divisions each with two rings, the most basal of scales only, the more distal of long setae trichobothria and cilia, seventh division with three rings of which the middle ring is scales only, the basal of setae and scales, the most distal of macrochaetae, stronger setae, cilia and trichobothria.

Male: Unknown.

Juveniles: K.261261 juv. ♀ of unrecorded head width. Ovipositor not developed, still with two pair of styli, inner processes not elongated (ca. 1.5 L/W), fewer combs on lateral nota, fewer macrochaetae per comb of abdomen, urotergite X not as long (L/ W 0.40) and less acute (95°) but no other difference could be distinguished but the trapezoidal thoracic sterna with combs only in the posterior half of the prosternum. — K.261297 juvenile ♀ (HW 0.90) ovipositor just starting, inner processes of coxite IX beginning to elongate (L/ W 2.0). — K.261326 juvenile ♀ (HW 0.83), ovipositor not developed, thoracic sternites with same comb arrangement but posterior margin not concave, perhaps even slightly convex but still wide.

Habitat. Although a total of 34 specimens have been collected during 15 collection events over four states, surprisingly no males have yet been collected. Specimens have been collected from bark of a variety of trees including Eucalyptus , Allocasuarina and Melaleuca (paperbark).

Etymology. The species is named auricoronata , referring to the “crown” of golden scales on the frons.

Remarks

The species appears to be close to Acrotelsella escherichi from Kangaroo Island (and reportedly Central Australia) which also has trapezoidal thoracic sternites. It differs from Womersley’s illustrated species by the reduced number of papillae in the labial palps (three versus 11), the absence of thicker spines on the apical articles of the ovipositor, the long processes of coxites IX which surpass the apex of the styli by about half the length of the stylus, and the shape of the internal process of coxites VIII which is broadly curved in the new species but somewhat rounded acute in A. escherichi .

The trapezoidal shape of the thoracic sternites may however be less phylogenetically relevant if the molecular data to hand is to be believed. This data seems to separate the Acrotelsella sensu lato species into two branches, one of which appears to have secondary type of ovipositor and the other with a simple primary type.

Acrotelsella giubana from Somalia and A. procedens Silvestri sensu Mendes, 1989 from Sri Lanka and Thailand, seem to be the closest species based on morphology as they both also have trapezoidal sternites and a primary type ovipositor. Acrotelsella auricoronata differs from A. giubana in having 25–30 divisions in the ovipositor versus 20–21, a less pointed urotergite X (56–69° versus 50°), longer posterior combs on the nota (3–5 versus 2 macrochaetae) and stronger bushes on the frons.

Acrotelsella procedens differs from both in having five labial papillae and a much smaller gap between the urosternal combs relative to the average length of their combs. Mendes (1989) comments that this species is quite variable. However, given the understanding now emerging with the Australian fauna, where molecular data is available to aid in species delimitation, it is quite likely that the three described populations of A. procedens probably represent distinct but related species.

Figures

Figure 67. Known distribution of Acrotelsella auricoronata sp. nov.

Figure 68. Acrotelsella auricoronata sp. nov., Balranald, NSW.

Figures 69–78. Acrotelsella auricoronata sp. nov. holotype ♀ (69) long pectinate macrochaeta of side of head; (70) finely pectinate macrochaeta of anal region; (71) pectinate macrochaeta of cerci; (72) darker dorsal scale; (73) head (cross-hatched area obscured by eye pigment); (74) antenna, scape, pedicel and basal intervals of flagellum; (75) mandible; (76) maxilla and part of palp; (77) maxillary palp, arrow showing location of basiconic sensillum; (78) labium (left side of submentum damaged, right palp missing). Scale bars = 0.1 mm.

Figures 79–85. Acrotelsella auricoronata sp. nov. holotype ♀ (79) pronotum, right half; (80) idem, left anterior trichobothrial area (with fine line delineating extent of scale coverage); (81) idem, left posterior trichobothrial area; (82) idem, left posterior comb; (83) mesonotum; (84) metanotum; (85) part of presternum,prothoracic sternum and PI (arrow indicates position of raised oval region).Scale bars = 0.1 mm.

Figures 86–87. Acrotelsella auricoronata sp. nov. holotype ♀ (86) mesothoracic sternum and coxae of PII; (87) metathoracic sternum and PIII. Scale bars = 0.1 mm.

Figures 88–96. Acrotelsella auricoronata sp. nov. holotype ♀ (88) urotergite V; (89) urotergite VII, left lateral comb; (90) idem, left sublateral comb; (91) idem, left submedial comb; (92) urotergite X; (93) urosternite V; (94) urosternite VII, left sublateral comb; (95) coxites VIII and IX with ovipositor; (96) apex of gonapophyses. Scale bars = 0.1 mm.

Figure 97. Acrotelsella auricoronatasp. nov. holotype ♀ (97) base of cerci and medial filament. Scale bars = 0.1 mm.