Visma, Smith & Mitchell & Molero-Baltanás, 2021

Smith, Graeme B., Mitchell, Andrew & Molero-Baltanás, Rafael, 2021, Molecular and morphological studies identify a new genus within the Heterolepismatinae (Zygentoma: Lepismatidae), Zootaxa 5030 (1), pp. 1-118 : 25-32

publication ID

https://doi.org/ 10.11646/zootaxa.5030.1.1

publication LSID

lsid:zoobank.org:pub:5D0206C0-65F7-4EAB-BAE7-986B63D06D07

persistent identifier

https://treatment.plazi.org/id/03B56C29-050C-FFD5-FF4D-F24AFE3D13A9

treatment provided by

Plazi

scientific name

Visma
status

gen. nov.

Visma View in CoL new genus

Type species: Visma brigalowsum n. sp.

Diagnosis. Medium to large silverfish (up to 13 mm H+B). Body shape typical of the slender Heterolepismatinae as in Figs. 1–9 View FIGURES 1–4 View FIGURES 5–9 . Pigment present. Macrochaetae smooth, apically bifurcate. Round scales multi-radiate of variable shape with sub-parallel ribs that do not, or only very slightly, surpass the margins, the number of ribs per round scale quite variable but two or more distinct rib-spacing arrangements present on some species; some scales have ribs close together, some quite widely spaced (see range in Fig. 16 View FIGURES 16–20 ). Triangular ( Fig. 21 View FIGURES 21–26 ) or rounded subrectangular ( Fig. 24 View FIGURES 21–26 ) scales with sub-parallel ribs, present on femora and tibia and sometimes also the basal article of the tarsus, those on the tibia may approach lanceolate in shape but with an indentation at the distal end. Triangular scales and sometimes lanceolate scales also present on the clypeus, scape, sometimes pedicel ( Fig. 39 View FIGURE 39 ), sometimes the maxillary palp and on some styli (especially IX) ( Fig. 40 View FIGURE 40 ). Terminal filaments with lanceolate scales on basal divisions and in some cases possibly also triangular scales ( Figs. 33–37 View FIGURES 33–37 ). Antennae with trichobothria and basiconic sensilla ( Figs. 15 View FIGURE 15 , 41 View FIGURE 41 ). Chaetotaxy of frons consisting of macrochaetae along all or most of the lateral margins as well as above the eyes, the anterior margin totally glabrous; peri-antennal groups not large, tenuously contiguous with the marginal macrochaetae. The clypeus is folded backwards from the anterior margin of the frons so that the mouthparts are quite posterior on the head (hypognathous). Eyes of 12 ommatidia. Labrum always with apically bifurcate macrochaetae (but reduced to just 1+1 inconspicuous, very short antero-lateral macrochaetae in Visma pallidum n. sp.).

Apical article of maxillary palp in both sexes with three slender branched papillae ( Fig. 14 View FIGURE 14 ). Apical article of labial palp with typical five sensory papillae of the compact type of variable arrangement, sometimes aligned in a straight or almost straight line, other times in two distinct lines ( Fig. 42 View FIGURE 42 ), sometimes, especially in juvenile specimens, with the distal three in a line curving around the posterior two (cluster arrangement). Pronotum with setal collar. Thoracic nota each with several short lateral bristle combs of just 1–2 (rarely three) macrochaetae and 1+1 posterior combs ( Fig. 43 View FIGURE 43 ) of 1–2 insertions positioned quite laterad, the more antero-lateral of which, when present, appears to be occupied by a long, thin trichobothrium-like seta; all trichobothrial areas open (type 1 of Mendes, 1986) the anterior trichobothrial areas on the pro- and metanota not associated with a submarginal macrochaeta, the anterior trichobothrium of the mesonotum with a macrochaeta mediad of the trichobothrium in some species and not in others (e.g. V. pallidum n. sp.). Thoracic sternites large and generally trapezoidal (see comments under Visma stilivarians regarding Western Australian fauna) and fringed laterally with subequally-spaced fine setae, posterolateral corners with small bristle combs of one to three macrochaetae. Femora and tibia with specialised triangular or rounded subrectangular scales (often narrower on tibia than on femur); tibia of PIII with a long, trichobothrium like seta (probably always present but often lost during collection or dissection). Tarsi with four articles, the second article of all legs usually bearing a trichobothrium-like hair ( Fig. 44 View FIGURE 44 ) (probably lacking in V. pallidum n. sp. but observed on at least one leg of one specimen in all other species examined), pretarsus with two claws and a medial empodial claw. Urotergite I with either 2+2 combs (lacking the submedial) or 3+3 combs, urotergites II–VII each with 3+3 bristle combs, VIII with 2+2 (lacking the sublateral), urotergite IX with infralateral groups of cilia and setulae. Urotergite X rounded and not very long, with many marginal macrochaetae, lacking 1+1 posterolateral submarginal macrochaetae. Urosternite I glabrous, urosternites II–VIII with 1+1 single macrochaetae. Coxites IX in both sexes not very elongate, although longer in the female. Three, four, five or six pairs of styli (on segments IV–IX, V–IX, VI–IX or VII–IX). Parameres short to long, conical, sometimes faintly divided into two segments. Penis typical for family; large, two segmented, apically with many short glandular setae each set on a protuberance. Female with a long primary type ovipositor with fine setae with some short rod-like setae apically ( Fig. 45 View FIGURE 45 ).

Etymology. The genus name is derived by using the first letter of the English word “visor” meaning a protection over the face referring to the scales that protrude in front of the frons, like the sunshield on a baseball cap, but in this case shielding the clypeus rather than the eyes. It is combined with the suffix -isma from Lepisma and is treated as grammatically neuter.

Remarks. The new genus is very distinct from other Heterolepismatinae in both its sequence data and morphology. Key characters include the presence of apically bifurcate macrochaetae on the labrum (but reduced to only 1+1 short macrochaetae in Visma pallidum n. sp.), and a character shared with Maritisma, triangular or rounded subrectangular scales on the femora, tibia and clypeus, the absence of macrochaetae along the anterior margin of the frons (also shared with some species of Heterolepisma ), the trapezoidal thoracic sternites fringed with fine setae, the presence of a trichobothrium on the second tarsal article of all legs (except probably V. pallidum n. sp.), the presence of scales on the terminal filaments and the larger number of abdominal styli (at least three pairs versus a maximum of three pairs), the sometimes subdivided parameres, and often the alignment of the five papillae of the labial palp in a linear or almost linear arrangement in fully grown specimens.

Four morphologically distinct groups of species have been identified, with closely related species within each group. These groupings are also supported to a limited extent by the molecular data. The species within each group are sometimes only subtly different to each other, which might, in the past, without the support of molecular data, been considered as “normal” variability within a species.

These groups include:

Visma pallidum n. sp. from Girringung National Park in north Queensland ( Fig. 46 View FIGURE 46 ), which has many unique characters including rounded, subrectangular scales on the femora and a gap in the lateral chaetotaxy of the frons .

• An inland northern group including V. brigalowsum n. sp. which extends in distribution from central Queensland to southern NSW ( Fig. 47 View FIGURE 47 ), V. tenebrosum n. sp. and the V. capricornia species group in central Queensland which have wide triangular scales on the femora, 2+2 combs on urotergite I, and several combs of two macrochaetae on the lateral meso and metanota and 1+1 posterior combs of only a single macrochaeta on these nota.

• An eastern NSW group ( Fig. 48 View FIGURE 48 ) including V. advenum n. sp., V. bingara n. sp., V. bundjalung n. sp. and V. brayi n. sp. which also have wide triangular scales on the femora, 2+2 combs on urotergite I, and several combs of two macrochaetae on the lateral meso and metanota but have two insertion points in each of the posterior combs of the nota.

• A southern group ( Fig. 49 View FIGURE 49 ) including V. stilivarians (Silvestri) from Western Australia, V. xanthorrhoea n. sp. and V. powellheueri n. sp. from South Australia, which differ in having narrow triangular scales on the femora, some lanceolate-like scales on the clypeus, 3+3 combs on urotergite I, no combs of two macrochaetae on the meso and metanota, and posterior combs of only a single insertion.

Further examples of specimens belonging to Visma are present in various Australian museum collections and the location of all known collection events is summarised in Fig. 50 View FIGURE 50 ; some of this material has not yet been sorted to species. The genus appears to be widespread on the Australian mainland but has not yet been collected from Victoria nor Tasmania, in spite of several days collection efforts in these states by the first author. Specimens clearly belonging to Visma n. g. have been collected in areas of very high rainfall (e.g. Julatten, Qld with 2122 mm rainfall per year on average) to much lower rainfall (Yanga near Balranald, NSW with 366 mm per year) but not yet in very dry areas of less than 300 mm rain per year (see discussion of type series of Heterolepisma stilivarians Silvestri ). It has been collected from the bark of trees or within cavities of fallen timber. The names applied to the groups above may prove to be inappropriate once the additional material is fully understood.

Heterolepisma annectens ( Silvestri, 1924) from the Chilean Juan Fernandez Islands may also belong to Visma although the published description is inadequate to make a decision. It has four pairs of styli and the lateral margins of the metathoracic sternum is fringed with setae, both characters of note in species of Visma n. g.

Key to the described species of Visma View in CoL n. g.

1. Distinct gap in lateral chaetotaxy of the frons at the level of the antennae ( Fig. 55 View FIGURES 51–62 ); specialised scales of both femora and tibiae broad rounded subrectangular ( Fig. 30 View FIGURES 27–32 ); labrum with only 1+1 very small macrochaetae ( Fig. 55 View FIGURES 51–62 ); anterior trichobothrial area of mesonotum without macrochaeta mediad of the trichobothrium............................... Visma pallidum n. sp.

- Lateral chaetotaxy of frons continuous between antero-lateral corners and the eyes (except for possible very small gap just before the eyes) ( Fig. 98 View FIGURES 94–106 ); specialised scales of femora triangular or narrow triangular ( Figs. 21–23, 25, 26 View FIGURES 21–26 ); labrum with several long macrochaetae ( Fig. 98 View FIGURES 94–106 ); anterior trichobothrial area of mesonotum with macrochaeta mediad of the trichobothrium... 2

2. Submedial posterior combs of nota with two insertions (a trichobothrium-like seta and macrochaeta) ( Fig. 43 View FIGURE 43 ); rib spacing on scales of nota always narrow (about 40 ribs per scale) Eastern NSW group....................................... 3

- Submedial posterior combs of nota with only a single insertion ( Fig. 110 View FIGURES 107–115 ); rib spacing on scales of nota narrow or wide (about 25 ribs per scale)...................................................................................... 6

3. Five pairs of abdominal styli............................................................................ 4

- Six pairs of abdominal styli............................................................................. 5

4. Only one to three combs on metanotum composed of two macrochaetae, no gap between macrochaetae around the eyes and lateral chaetotaxy of head.............................................................. Visma bingara n. sp.

- Three to five combs on metanotum composed of two macrochaetae, gap 1–2 macrochaetae wide between the macrochaetae around the eyes and lateral chaetotaxy of head............................................ Visma bundjalung n. sp.

5. Anterior trichobothrial area of pronotum located almost halfway along the margin................. Visma advenum n. sp.

- Anterior trichobothrial area of pronotum 0.36–0.42 along margin.................................. Visma brayi n. sp.

6. Urotergite I with 3+3 combs; meso and meta nota with lateral combs each of a single macrochaeta, never in combs of two macrochaetae Southern group........................................................................... 7

- Urotergite I with 2+2 combs (lacking submedial); meso and metanota with 1–5 combs composed of two macrochaetae Inland northern group....................................................................................... 9

7. Ribs of most scales of nota closely spaced, about 30–40+ per scale ( Fig. 18 View FIGURES 16–20 ); more than three pairs of abdominal styli..... 8

- Ribs of most scales of nota more widely spaced, about 25 per scale; three pairs of styli only in both sexes............................................................................................... Visma powellheueri n. sp.

8. Four pairs of abdominal styli; triangular scales of tibia with distal triangular incision, the distal corners acute............................................................................................ Visma xanthorrhoea n. sp.

- Five pairs of abdominal styli; triangular scales of tibia with distal triangular incision, the distal corners rounded (at least in Visma aff. stilivarians )............ Visma stilivarians ( Silvestri, 1908) (as well as V. aff. stilivarians populations from SA)

9. Metanotum with five or six combs of two macrochaetae along each of both lateral margins; antennae in alcohol evenly pigmented........................................ Visma capricornia n. sp. (as well as V. aff. capricornia populations)

- Metanotum with one to four (rarely five but on just one side) combs of two macrochaetae along each lateral margin; antennae in alcohol distinctly banded in adult specimens............................................................ 10

10. Anterior trichobothrial area of pronotum 0.35–0.42 along the lateral margin; five pairs of abdominal styli; the vast majority of scales of pronotum with narrow gaps between the ribs and about 30–40 ribs or more per scale, although some with somewhat wider spacings may be found in the antero-lateral regions.................................. Visma tenebrosum n. sp.

- Anterior trichobothrial area of pronotum 0.44–0.49 along the lateral margin; four pairs of abdominal styli (sometimes five); scales of nota with great variety of rib spacings including many with wide rib spacing and only about 25 ribs per scale ( Fig. 16 View FIGURES 16–20 ).......................................... Visma brigalowsum n. sp. including V. aff. brigalowsum populations.

Character stability

Pigmentation was found to vary too much from specimen to specimen, especially with longer time in alcohol and maturity of the specimen. Visma tenebrosum n. sp. appears to stand out to some extent by the exceptionally dark posterior pigmentation, especially of the epiproct and paraprocts. The absence of distinct banding of both the antennae and terminal filaments was used mostly successfully to distinguish specimens in alcohol of V. capricornia n. sp. from V. brigalowsum n. sp. and V. tenebrosum n. sp. It failed to identify one juvenile specimen, later confirmed by dissection to belong to V. brigalowsum n. sp. It also proved ineffective to distinguish slide material as the bands of pigmented versus unpigmented areas had become indistinct over time in the Tendeiro mounting medium. Given the variability observed and the poor persistence in storage, pigment related characters may only be useful when examining freshly collected adult material in alcohol.

Scale type, including those of the nota, femora and clypeus, appear to be important although not easy to use. Scales are difficult to see on slide mounted specimens (hyaline or with several over-lapping layers) and many or most can be lost during collection and handling. However, electron microscopy gives excellent images and shows quite strong differences, at least between species groups. Visma pallidum n. sp. has unique, somewhat rounded subrectangular scales on the femora ( Fig. 24 View FIGURES 21–26 ). Most northern species have mostly wide triangular scales on the femora, while the southern species have mostly narrower triangular scales. There appear to be consistent differences in the shape of the distal margin of these triangular femoral scales ( Figs. 21–26 View FIGURES 21–26 ). The width of the triangular scales of the femora can vary across the surface of the femora as well as from PI to PIII, with the triangular scales seemingly wider anteriorly in both cases .

The round scales of the nota can be of several types ( Fig. 16 View FIGURES 16–20 ), some with ribs close together, others more widely spaced and some with very wide rib spacing. This character has proven useful for separating V. tenebrosum n. sp. (where just a few moderately wide-spaced scales were seen) from V. brigalowsum n. sp. which always has more numerous and even wider ribbed scales, sometimes in very large numbers. The same character was useful separating V. xanthorrhoea n. sp. from V. powellheueri n. sp., the latter having many more scales of the wide-spaced rib variety. Some experience with different species and specimens is required to use the rib-spacing character with confidence and a better means of quantification is required given the variability in scale size and shape.

The shape of the scales on the tibia ( Figs. 27–32 View FIGURES 27–32 ) has proven useful to separate specimens of Visma xanthorrhoea n. sp. from those of Visma aff. stilivarians (acute versus rounded corners either side of the distal triangular incision).

The narrow triangular scales of the clypeus may have serrated ( Fig. 38 View FIGURE 38 ) or rounded ( Fig. 269 View FIGURES 267–274 ) distal margins and the lateral margins may converge distally, almost approaching lanceolate in shape (also see Fig. 18 View FIGURES 16–20 ). Some species appear to have very few scales on the clypeus with most insertion points occupied by small setae, others have many and of varying shape. We believe that there is much scope to further develop scale type, shape and distribution as a reliable taxonomic character for this genus, however this would require more extensive material with reasonably intact scale coverage, which presents a significant challenge. It may be necessary to collect material alive and maintain it until after a moult.

Trichobothrial areas of the pronotum were located noticeably more anterior on some species compared to other Heterolepismatinae and there appears to be reliable differences between species. The position of the anterior trichobothrium of the pronotum may be useful for separating species within each of the species groups although more data would be useful for increasing confidence. There was no indication that the sex or age of the specimen affected the position of the trichobothria. In general, the trichobothria were either around 0.35–0.42 along the margin or 0.42–0.51 but one specimen (K.541551) of V. aff. stilivarians from Para Wirra Rd, had the anterior trichobothrial areas at 0.38 whereas the other six specimens of this morphospecies had trichobothria 0.43–0.51 along the margins. Similarly, one specimen of V. xanthorrhoea (SAMA 05-000005) from Mt Remarkable had the trichobothrial area at 0.37 while the other four specimens in the series all lay between 0.43–0.46. It is possible that the position of the trichobothrial areas is less consistent in species of the southern group, or perhaps even overall. In two cases the position of the trichobothria were different on each side and in one case there was a supernumerary trichobothrium, but in general it appears to be a reasonably consistent character if a few specimens can be measured. On the basis of this character Visma advenum n. sp. may be distinguished from the other three species in the group ( V. bundjalung n. sp., V. brayi n. sp. and V. bingara n. sp.) and V. brigalowsum n. sp. can also be distinguished from the other two species in its species group ( V. tenebrosum n. sp. and V. capricornia n. sp.). The position of the anterior trichobothria on the meso and meta nota were not found to be diagnostically useful with all trichobothria located 0.64–0.74 and 0.70–0.84 respectively, at least partly due to the difficulty of defining the anterior margin of these nota.

The number of combs of two macrochaetae on the lateral margins of the meso and meta nota has also been used to separate some species. Such combs are not found in the Visma pallidum n. sp. nor in any species of the southern group. Three to six combs can be found on the eastern NSW group. This character is therefore only useful in separating species within the northern inland group. The Visma capricornia group generally displays more combs of two macrochaetae than either Visma brigalowsum n. sp. and V. aff. brigalowsum. Usually five or six such combs are present on both the meso- and meta-nota. One specimen (K.541596) from Redcliffe Tableland had just four combs of two macrochaetae on the mesonotum but five pairs on each side of the metanotum. One specimen of V. aff. brigalowsum from Yanga (K.261270) had five combs on each side of the mesonotum but only three and four on the sides of the metanotum. There is also some overlap with specimens of V. tenebrosum n. sp. with one example from Eungella having five combs on one side of both the meso- and meta-nota but three on the other side of both. The character is considered useful here if a range of specimens can be included in an analysis.

A gap in the lateral chaetotaxy of the frons near the antennae was only found in one species V. pallidum n. sp.

In most cases there is a line of macrochaetae just a single macrochaeta wide along the lateral margins before it becomes two or more macrochaetae wide. In the southern group species, this row is fairly short (1–7 macrochaetae), in the more northern species this row is much longer (5–15). The character does not appear reliable for separating closely related species.

The peri-antennal group offers little help. In some individuals it is clearly isolated from the marginal macrochaetae, but in others it is contiguous; in most individuals it is hard to decide whether it should be classified as contiguous or isolated. The number of macrochaetae in the peri-antennal group is variable but the southern species have fewer macrochaetae (2–4) while the more northern species have 3–12. The single, quite large, specimen of V. advenum n. sp. has 11–12. Visma pallidum n. sp. has the smallest average number with 2–5. The character may be relevant in separating species in the V. capricornia group (e.g. the large specimens from Mt Moffatt each had 9–13 macrochaetae in each group while the two specimens from Marlborough only had five but the nine specimens from Redcliffe Tableland material had 4–10. More specimens need to be examined including subadult and very mature specimens.

The relative length of the articles of the maxillary palp proved far too variable within each species, even from one side of an individual to the other. For example, the average relative length of the ultimate to penultimate articles in three specimens of V. brayi n. sp. from the same locality were 1.04, 1.15 and 1.20 .

The five articles of the labial palp were always of the compact type but their arrangement can be quite variable. Sometimes the distal three curve around the proximal two in a cluster arrangement, sometimes the distal three are in a straight line parallel to the proximal two, sometimes these lines almost merge with the proximal two intruding into the gaps between the distal three, and in some cases the papillae form a straight line. There appears to be quite some variation within the same species and this may be related to specimen age; in juvenile specimens the cluster arrangement is most common, becoming more off-set in younger adult specimens and approaching a straight line in the largest individuals. The character could perhaps be useful for distinguishing between larger specimens of each species.

The presence of a macrochaeta mediad of the anterior trichobothrium on the mesothoracic notum is a useful character. Most species have a submarginal macrochaeta mediad of each anterior trichobothrium of the mesonotum, this macrochaeta is absent on all V. pallidum n. sp. examined. On some specimens of other species (seven specimens over five species), this macrochaeta was lacking on one side but never absent from both sides.

The prothoracic sternum was always trapezoidal in the species described here with the posterior margin usually slightly concave but in some specimens could be straight or even just slightly convex and therefore is difficult to use. Some of the Western Australian material included by Silvestri in the type series of H. stilivarians had a quite convex posterior margin so that the shape of the sternum appeared more parabolic that trapezoidal. This character should best be reconsidered when the Western Australian fauna is more thoroughly investigated .

The L /W ratio of urotergite X is probably too variable. For example, the ratio varied between 0.33 and 0.43 in the eight specimens collected near Mt Crawford in South Australia, here assigned to V. cf. stilivarians . The presence of a gap in the chaetotaxy of the posterior margin also proved unreliable as in a few species, one or more specimens showed a gap where the others didn’t .

The number of pairs of abdominal styli is somewhat useful; however, the number can be variable in at least one species ( V. brigalowsum n. sp.) although DNA suggests this group may be split into two lineages, one of which always seems to have five pairs of styli and the other either four or five pairs of styli. We have nevertheless used this character to define some species differences even though only a single specimen may have been available, but only when supported by molecular data, e. g., V. advenum n. sp. and V. bingara n. sp.

Parameres are clearly divided into two segments on some species, on others the suture appears to be incomplete and in others no suture could be observed. It is assumed here that the ancestral condition was two-segmented but in some species this suture is fully or partly fused. The shape of the paramere appears to be a useful character, being long and conical in V. brigalowsum n. sp. but shorter and more rounded in other species such as V. pallidum n. sp. and V. xanthorrhoea n. sp.

PI

Paleontological Institute

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