Australotomurus Stach, 1947

Bellini, Bruno Cavalcante, Greenslade, Penelope, Baquero, Enrique, Jordana, Rafael & Souza, Paolla Gabryelle Cavalcante De, 2022, A synthesis of the current knowledge on the Australian Orchesellidae (Collembola, Entomobryoidea), Zootaxa 5115 (2), pp. 221-257 : 234-237

Genus Australotomurus Stach, 1947

Diagnosis. Specimens pigmented, colour patterns variable, eyepatches black. Scales absent and dorsal macrochaetae abundant, as in other Orchesellini . Antennae five or six segmented, with Ant. I always subdivided, rarely Ant. II as well, apical bulb of Ant. IV present, males with dimorphic chaetae on Ant. Ib, II or III, rarely also on frontolateral head. Postantennal organ present. Eyes 8+8. Tenent-hairs acuminate. Tenaculum with 5–15 chaetae. Manubrium ventrally with 2+2 distal spines, mucro bidentate without the mucronal spine (adapted from Mari-Mutt & Greenslade 1985; Greenslade & Jordana 2014).

Remarks on Australotomurus dorsal macrochaetotaxy. To provide further data to compare Australotomurus and other scaleless Orchesellidae species, we labeled the dorsal macrochaetotaxy of the genus based on the original drawings of Mari-Mutt & Greenslade (1985) and Greenslade & Jordana (2014). Data on the anterior head and Abd. II–IV chaetotaxy are available to all species ( Figs 9–17 ), while Th. II–Abd. I was only described to Australotomurus morbidus Greenslade & Jordana, 2014 and A. womersleyi Mari-Mutt & Greenslade, 1985 ( Figs 14 and 16 ), and Abd. V only to A. morbidus ( Fig. 15D ). We could also confirm the dorsal head chaetotaxy of Australotomurus based on undescribed species, adding chaetae missing on the previously described seven species and the trunk sensilla. Chaetal labels were provided after a detailed comparison among all studied Australotomurus species and other Orchesellidae . The justifications to suggest homologies are presented below.

The overall dorsal macrochaetotaxy of Australotomurus is similar to other scaleless Orchesellidae , in which the excessive plurichaetosis and high levels of intraspecific variability in adults obscure clear comparisons among the species ( Mari-Mutt & Greenslade 1985; Potapov & Kremenitsa 2008; Baquero et al. 2017). The dorsal chaetotaxy within the genus was detailed labeled only to A. morbidus Greenslade & Jordana, 2014 , and it is mainly constituted by macrochaetae, as seen in Orchesellinae and Nothobryinae genera like Orchesella Templeton, 1836 (in Templeton & Westwood 1836), Orchesellides Bonet, 1930 , Capbrya Barra, 1999 and Nothobrya Arlé, 1961 ( Szeptycki 1979; Jordana & Baquero 2006; Potapov & Kremenitsa 2008; Baquero et al. 2017; Nunes & Bellini 2019; Nunes et al. 2020).

To the anterior dorsal head, we used as a model A. morbidus . Compared to its others congeners, this species shows an overall reduced dorsal macrochaetotaxy. On the A series, A. morbidus shows three extra mac after A5 which were not labeled in Greenslade & Jordana (2014, p. 567, fig. 16). So we named A6 following its position as seen in D. dolosus sp. nov. ( Fig. 3G ), the most external as A7, and the posterior to A6 as A 6p. While A6 and A7 are present in all Australotomurus species, A6p is only absent in A. echidnus ( Fig. 10A ). Some species like A. barbatus Mari-Mutt & Greenslade, 1985 and A. johanni Mari-Mutt & Greenslade, 1985 also have another mac between A6p and An3, labeled as A7i ( Figs 9A and 12A ). The group of internal mac nearby and including A3 and A4 is highly interchangeable among the species, and this field can have only these two mac (as in A. morbidus ), three (as in A. barbatus , A. echidnus , A. immodestus Mari-Mutt & Greenslade, 1985 , and A. montanus Mari-Mutt & Greenslade, 1985 ), four (as in A. womersleyi Mari-Mutt & Greenslade, 1985 ) or can be completely devoid of mac (as in A. johanni ). Because of this we named the two possible extra mac as A3e and A4e. Only in A. morbidus there is an extra mac seen between A0 and A2, which was named as A1e. The M series of this latter species have M0, which was also observed more anteriorly in undescribed species ( Fig. 18 ). This mac is absent in all other described taxa, which have instead S0’ slightly ahead S0 ( Figs 9A , 10A , 11A , 12A , 13A , 16A ). Most species of the genus have the complete M1–4 series, however A. montanus is devoid of M1–2 and A. morbidus of M1. Among the other taxa, there can be an extra mac between M2 and M3 named as M3i, as in D. dolosus sp. nov. ( Fig. 3G ); and a second one posterior to M2 (M2p), only seen in A. barbatus and A. womersleyi . In A. morbidus there is a mes external to M4 herein labeled as M4e, which may be present as well in Capbrya (see Nunes et al. 2020, p. 27, fig. 5). To Nothobrya , apparently M4e is missing and a better interpretation to the dorsal head group M3–4–4e of N. sertaneja Nunes & Bellini, 2019 (p. 384, fig. 11) may be M3i–3–4. The S series of Austrolotumurus is remarkably complex and variable, and it is apparently more similar to that of Orchesellides and Orchesella than to Capbrya and Nothobrya ( Jordana & Baquero 2006; Potapov & Kremenitsa 2008; Baquero et al. 2017; Nunes & Bellini 2019; Nunes et al. 2020). We first detected the main mac (S0–S6, including S6i), which were also seen in D. dolosus sp. nov. ( Fig. 3G ) and are present in all species (with exception of S 2 in A. montanus ). We also observed S3e is universally seen in Australotomurus taxa. After, we compared the other extra chaetae to Lepidosira neotropicalis Nunes & Bellini, 2019 (in Nunes et al. 2019), to mark the external and internal mac. We also identified a more anterior mac nearby S5 (S5a), present in all species besides A. echidnus and A. morbidus , and a second one nearby S4 (S4a), only seen in A. barbatus and A. womersleyi . Since there is no consensus of the nomenclature of S series among the Entomobryoidea , as the more external chaeta can be named as S5 (presented as S5i in Jordana & Baquero 2005), S6 (Soto-Adames 2008) or S7 ( Mari-Mutt 1979), it is important to state this series may have a different understanding of the homologies using different systems, like the one of Jordana & Baquero (2005). The post-sutural (Ps) series with its only three possible mac, proved itself highly variable among Australotomurus taxa. No described species has the three mac (Ps2–3, Ps5) at the same time. While Ps2 is present in most taxa, except for A. womersleyi, Ps 3 was only seen in A. echidnus and A. womersleyi , and Ps5 only in A. barbatus , A. montanus , and A. morbidus . Finally, the other posterior chaetae are organized in five series: post-occipital internal (Pi), post-occipital anterior (Pa), post-occipital medial (Pm), post-occipital posterior (Pp) and post-occipital external (Pe), and were originally represented to all described species, except for A. echidnus . On the posterior border of the head there is a collar of mac partially represented to few species (unnamed posterior chaetae in Figs 9A , 11A , 12A , 13A , 14A , 16A ), which we also observed in specimens of Nothobrya and Capbrya ( Nunes & Bellini 2019, p. 384, fig. 11, and Nunes et al. 2020, p.27, fig. 5, respectively). This posterior collar (or crown) may be homologous to the spine-like chaetae seen in more derived Entomobryoidea , as the Seirinae (see Nunes et al. 2021, p. 7, fig. 6). The complexity of the posterior head chaetotaxy in Australotomurus complicates the correct identification of the macrochaetae homologies, however excluding the labile (present or absent) mac, its main pattern could be better compared to other taxa. We first identified the chaetae nearby the postocullar bothriotrichum (Pa6), Pa4–5, and Pm5 mac, which were observed in all species. Identifying the pattern with a triangle made by Pa2–3 and Pm3, with a lateral Pp3 (slightly different in A. womersleyi and A. johanni , but mostly stable in the other species) was crucial to determine the homology of other posterior mac. This conjunct of chaetae is mostly present as mac or mic in other Entombryoidea, like other scaleless Orchesellidae as Nothobrya and Capbrya , some Heteromurinae as D. dolosus sp. nov. ( Fig. 3G ) and Falcomurus spp. , Entomobrya Rondani, 1861, Seirinae and Lepidocyrtinae ( Jordana & Baquero 2005; Soto-Adames 2008; Cipola et al. 2018, 2019, 2020; Nunes & Bellini 2019, Nunes et al. 2020, Bellini et al. 2021). The Pa2–3, Pm3, and Pp3 set was also observed in all species of Australotomurus , and helped us to identify the Pi series and the presence of extra mac surrounding them. In our proposition, we considered the extra mac Pa3e and Pa4e as the external chaetae to Pa3 and Pa4 respectively, slightly differently from Jordana & Baquero (2005). We also merged Pp and Pe series in a single Pe row, and Pe1–2 were observed to all species. A summary of the head’s dorsal macrochaetatoxy of Australotomurus is represented in Fig. 18 , including extra macrochaetae seen only in undescribed species (marked in grey). In this figure, as well as to the trunk ( Figs 19–20 ), we also included in the left side the main areas of chaetae described in Jordana & Baquero (2005), with some modifications of Baquero et al. (2017). It is important to state the labels herein provided to the head mac should be taken as provisional, since the first instar was not studied to any of the species, differently from Soto-Adames (2008) for example. So, at least some of the labels do not separate with confidence the primary from secondary chaetae. Nevertheless, the comparisons we have made with other genera and among the species gave support to the presented system.

As said before, the dorsal chaetotaxy of Th. II–Abd. I was only described for two species. Here, as well as to the other trunk segments, we applied Szeptycki (1979) more strictly, with the modifications of Zhang et al. (2019), and some additions of Nunes et al. (2020). The main differences between A. womersleyi and A. morbidus are: on Th. II, A. womersleyi has the p1i2 set, two extra mac associated to m4 complex (m4p2 and m4i2), two extra chaetae in the m4ai complex, and the absence of m5 and its anterior multiples (the opposite in A. morbidus ) ( Figs 14B , 16B ); on Th. III, it has also the p1i2 set with two mac, m1a, and lacks m5p (contrary to A. morbidus ) ( Figs 14C , 16C ); and on Abd. I, its macrochaetotaxy is remarkably more complex, with the presence of multiples of a1a, a2a and a set of three mac on a3a group, a5i–2 and a5p2 mac, p6, and m6 (all absent in A. morbidus ), plus five extra mac without clear homologies (marked as a ‘x’) ( Figs 14D , 16D ). A synthesis of the dorsal macrochaetotaxy of Th. II–Abd. I of A. womerleyi and A. morbidus is represented in Fig. 19 , including the trunk sensilla observed in the undescribed species.

Following Szeptycki (1979) and Zhang et al. (2019), the Abd. II in Australotomurus spp. shows internally three main fields with a variable number of secondary mac: a1–3 complex, always with a1, a2, and a3, plus different sets of multiples; m3ea complex, with a set of 3–6 chaetae with unclear homologies; and m3e complex, including m 3ei and m3ep, whenever present. This last group always holds m3e and can show up to five other multiples (m 3ei, m3ep, m3e2–3). The primary m3 mac is present in all species, but p4 is only seen in A. barbatus , A. johanni , and A. montanus , and m4 is present only in A. echidnus . The external mac in most species are a6, m5–6 and p5, and the absence of some of these chaetae in A. echidnus , A. morbidus , and A. immodestus should be considered with caution, as such chaetae can be easily overlooked due to position. All possible macrochaetae in this segment seen in previously described species are represented in Fig. 20A . Observing the undescribed species, this segment may present up to five sensilla, including as.

Similarly to the Abd. II, the Abd. III also shows the same three main fields with a variable number of secondary mac (sensu Szeptycki 1979 and Zhang et al. 2019). On the a1–3 complex, a1 is universally present while a2–3 mac may be absent in A. womersleyi and only a3 mac can be absent in A. johanni . On the m3ea complex, m3ea is mostly present (may be absent only in A. morbidus and A. montanus ), while m3eai is present only in A. johanni and A. montanus , and it is labile in A. barbatus . The m3e complex holds the m3e and m 3ei mac (the second present only in A. echidnus , A. johanni , and it is labile in A. montanus ), and up to four more secondary mac including m 3ei. The primary m3 is present in all species of Australotomurus , while A. montanus may also have a posterior mac herein labeled as m3p, plus p3, and A. barbatus also has a labile p3. The external mac are always am6, pm6, m7, and p6 on this segment, however we could track a 7 in part of the undescribed species. The original description of A. echidnus shows an abnormal position to the third bothriotrichum of Abd. III ( Mari-Mutt & Greenslade 1985, p. 234, fig. 58). We believe this is the fallen a5 bothriotrichum, which is not represented in the drawing in its expected position. So we corrected this drawing following Szeptycki (1979). A synthesis of the macrochaetotaxy of Abd. III in Australotomurus is represented in Fig. 20B . This segment has up to seven regular sens (including as and acc.p6) and the microsensillum ms in the undescribed species.

The dorsal macrochaetotaxy of the Abd. IV is remarkably complex and variable in Australotomurus . To this segment we chose the two most complex species regarding the internal mac, A. johanni and A. echidnus , to track the homologies and apply them to the other taxa. We found this internal macrochaetotaxy, especially the more anterior mac, fit best the interpretation of Orchesellides boraoi Bonet, 1930 juvenile provided by Zhang et al. (2019, p. S22, fig. S14C). In this late species there is a transversal arch of mac made by A3, Ae3, B3, Be3, an extra unnamed one, C1, and Sm, before T2 bothriotrichum. It follows a similar pattern seen in A. barbatus , A. echidnus , A. montanus , A. johanni , and A. womersleyi , but they all lack Ae3. The extra mac nearby C1 is present in all species of Australotomurus but A. morbidus , and since it may be useful to compare the species but do not have a clear homology, we provisionally name it as the extra anterior (xa) mac. Another mac without clear homology seen only in A. johanni and A. womersleyi is posterior to xa and external to B5, and was provisionally named as the extra posterior mac (xp). Considering the internal mac, A6, B2, Be3, C1, and Sm are stable in Australotomurus while the others vary among the species, or even are polymorphic in the same taxon. Among the undescribed species we could also track a labile B1. Regarding the lateral Abd. IV, D1p, D3, E1–3, and F1 were represented to all species, while other differences may be considered with caution as the more lateral chaetae of this segment may have been overlooked in their original descriptions. A summary of the macrochaetotaxy of the Abd. IV is shown in Fig. 20C . In this segment we observed in the undescribed species several long sensilla as expected, which were not represented in the drawing, but our preliminary analysis did not allow us to clearly identify as and ps, so they were also omitted in the Fig. 20C .

The dorsal chaetotaxy of the Abd. V ( Figs 15D , 20D ) was only previously represented to A. morbidus . With the presence of three transversal rows of mac it is tempting to assume they represent a, m, and p series, as represented in Greenslade & Jordana (2014, p. 568, fig. 17). The presence of a posterior unpaired mac also suggests it is p0, as seen in other Entomobryoidea . However, the development of scaleless Orchesellidae shows that the more internal a and m mac (a1, m2, a3, and m 3 in a sequence) can become closer to each other and aligned in the adults ( Szeptycki 1979; Nunes et al. 2020). Also, the reduced number of mac represented to A. morbidus strongly suggests the lateral chaetae were disregarded, and only the central mac were represented. We could confirm this analyzing the undescribed species, which let us to include further lateral mac ( Fig. 20 , grey symbols) and the four sens seen in this segment. So, concerning A. morbidus , the first row in this segment is represented by a1, m2, a3, and m3, the second by p1, p3–4, and the third and more posterior row by pp series ( Fig. 15D ). In many Entomobryoidea , whenever present p0 occurs above p1, as in the Orchesellinae studied by Szeptycki (1979, p. 189). However, there can be further unpaired mac on this segment, even posteriorly to p0 (see Zhang et al. 2019, p. S25, fig. S17G). We believe it is the case to A. morbidus , and so we labeled this unpaired posterior mac as p0p.

As discussed before, the presence or absence of the more lateral mac on trunk in the original descriptions, summarized in Figs 19–20 , should be considered with caution as many of these chaetae are primary and were possibly overlooked in the descriptions ( Szeptycki 1979; Zhang et al. 2019). They can also exist as mic or mes, as well as other primary trunk chaetae not originally represented in some species. Nevertheless, we marked them as present or absent (with a dash above the mac symbols). About the different positions some chaetae could show, represented in Figs 18–20 , at least in some cases this could be the result of more diagrammatic and imprecise drawings of Mari-Mutt & Greenslade (1985), which we tried to translate to this study as close as possible to the original representations.

A detailed comparison of the main differences of the anterior dorsal head and Abd. II–IV macrochaetotaxy of Australotomurus species are provided in Tables 2 – 3 . Other segments were omitted since they were not described to all species.

Figures

FIGURE 3. Dicranocentrus dolosus sp. nov. head: A, apex of right Ant. IV (dorsal view), arrow points to the ventral pin projection, dashed sens are present or absent; B, apex of left Ant. III (dorso-lateral view); C, left Ant I. ventral face smooth chaetae; D, left Ant II. ventral face smooth chaeta; E, labral papillae; F, labral and prelabral chaetotaxy; G, dorsal head chaetotaxy and eyes (right side).

FIGURE 9. Dorsal macrochaetotaxy of Australotomurus barbatus: A, head; B, Abd. II; C, Abd. III; D, Abd. IV.

FIGURE 10. Dorsal macrochaetotaxy of Australotomurus echidnus: A, head; B, Abd. II; C, Abd. III; D, Abd. IV.

FIGURE 11. Dorsal macrochaetotaxy of Australotomurus immodestus: A, head; B, Abd. II; C, Abd. III; D, Abd. IV.

FIGURE 12. Dorsal macrochaetotaxy of Australotomurus johanni: A, head; B, Abd. II; C, Abd. III; D, Abd. IV.

FIGURE 13. Dorsal macrochaetotaxy of Australotomurus montanus: A, head; B, Abd. II; C, Abd. III; D, Abd. IV.

FIGURE 14. Dorsal macrochaetotaxy of Australotomurus morbidus: A, head; B, Th. II; C, Th. III; D, Abd. I.

FIGURE 15. Dorsal macrochaetotaxy of Australotomurus morbidus: A, Abd. II; B, Abd. III; C, Abd. IV; D, Abd. V.

FIGURE 16. Dorsal macrochaetotaxy of Australotomurus womersleyi: A, head; B, Th. II; C, Th. III; D, Abd. I.

FIGURE 17. Dorsal macrochaetotaxy of Australotomurus womersleyi: A, Abd. II; B, Abd. III; C, Abd. IV.

FIGURE 18. A summary of the dorsal head macrochaetotaxy of all Australotomurus species combined based in the literature (black circles), grey circles represent mac only seen in the undescribed species, black circles without a dash above them represent mac seen in all previously described taxa. The right side shows the complete labeled chaetotaxy as discussed in the text; the left side shows the main areas of mac based in Jordana & Baquero (2005) and Baquero et al. (2017). Double arrows and dashed circles show variable positions of some mac.

FIGURE 19. A summary of the dorsal macrochaetotaxy of A. morbidus and A. womersleyi combined, pseudopores position were marked based on A. morbidus and the sensilla and microsensilla were observed only in the undescribed species. Circles without a dash above them represent mac seen in both species. A–C, right side shows the complete labeled chaetotaxy of Th. II–Abd. I respectively, as discussed in the text; the left side shows the unlabeled chaetae and complexes, plus Th. II T1 and T2 areas of mac based in Jordana & Baquero (2005) and Baquero et al. (2017). Double arrows and dashed circles show variable positions of some mac.

FIGURE 20. A summary of the dorsal abdominal (Abd. II–V) macrochaetotaxy of all Australotomurus species combined based in the literature (black circles), grey circles represent mac only seen in the undescribed species, black circles without a dash above them represent mac seen in all previously described taxa, pseudopores position were marked based on A. morbidus and the sensilla and microsensillum were observed only in the undescribed species. A–D, right side shows the complete labeled chaetotaxy of Abd. II–V respectively, as discussed in the text, Abd. V only previously described for A. morbidus; the left side shows the unlabeled chaetae and complexes, plus abdominal A1–10 areas of mac based in Jordana & Baquero (2005) and Baquero et al. (2017). Double arrows and dashed circles show variable positions of some mac.