Rambutanura oblita Babenko & Antipova, 2024, sp. nov.
Creators: name: Babenko, Anatoly
name: Antipova, Maria
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Collembola
Poduromorpha
Neanuridae
Rambutanura
Rambutanura oblita

description: Rambutanura oblita sp. nov.
Figs 1–16, Table 1–3
Type material. Holotype: female, Vietnam, Dong-Nai Province, Ma-Da Forest, 13 June 1995, Tatiana K. Sergeeva leg. Paratypes: 2 females and 1 juvenile, same data as holotype; 2 females and 2 males, same data as holotype, but 12 May 1995. All types of the new species are deposited in the collection of the Zoology and Ecology Department of the Moscow State Pedagogical University.
Diagnosis. A species of the genus characterized by the presence of elongated finger-shaped tubercles only on the last three abdominal segments, a large and variable number of dorsal sensilla in Ant. IV and the absence tubercle Cl on the head. In other respects, it shares almost all characters mentioned in the original generic diagnosis with other known congeners: large and convex body, absence of blue pigment, 2+2 colourless ocelli, labral formula 0/2,2, labium with 11 ordinary setae and a minute sensorial papilla, styliform maxilla, mandible with more than six teeth, tubercle arrangement of the ‘ Bilobella type’, plurichaetosis of mou setae on Ant. IV, ordinary setae and dorsal sensilla on terga, and unguis with one inner tooth.
Description. Body length (without antenna) 2.4–4.9 mm, holotype 3.3 mm. Body wide and flattened, tubercles prominent, well developed, those on Abd. IV–VI prolonged, finger-shaped (Fig. 1). Granulation not too strong, secondary granules usually rounded at apex, cuticular reticulations clearly visible only on finger-shaped digitations on abdominal tip (Fig. 14). Live body color unknown, alcohol material yellowish.
Head with 2+2 colourless ocelli. Antennae slightly longer than head and clearly shorter than head width. Apical vesicle on Ant. IV subdivided, small and poorly visible, dorsally Ant. III–IV fused, ventral separation clear. Both dorsal and ventral sides of Ant. IV with many supplementary setae, including both common s-setae (mou) and blunt sensilla S (Figs 8–9); i seta and subapical organite (or) present. Antennal organ on Ant. III without sgd, consisting of two “inner”, rather long sensilla, sgv and ms (Figs 8, 10); ventral side of Ant. III with 4–5, 4, 5(6) ordinary setae in ve, vc and vi groups, respectively; dorsal side with 3 setae (Fig. 10). Ant. I–II with 12–14 and 11–12 setae, respectively (Table 1).
Other cephalic setae: Vi, 5; Ve, 15–20; labrum, 0/2, 2; labium, 11 + x; Ant. I, 12–14; Ant. II, 11–12; Ant. III, 15–18+2 inner S + sgv + ms; Ant. IV, general plurichaetosis + many S + seta i + or
Dorsal side of head with 7 prominent tubercles (Fig. 2): Af, 2Oc, 2(Di+De) and 2(Dl+L+So), tubercle Cl undeveloped and all setae located in anterior part of head (C, E, D, F, G, G’) free (Fig. 3). General cephalic chaetotaxy see Table 1. Buccal cone short, labral sclerotization non-ogival. Labrum without prelabral setae, but with two pairs of labral setae (0/2, 2 totally). Labium with three proximal setae and only one visible sensillar papilla x, both basomedial and basolateral parts of labium each with 4 setae. Maxilla styliform (Fig. 6). Mandible comb-like with two big basal teeth and 15–18 smaller ones, associated with an additional ramus divided apically into 3–4 branches (Fig. 7).
Dorsal setae strong, slightly thickened and almost smooth, their differentiation into macro- and mesosetae clearcut (Figs 11–12), sensilla thin, whip-like and longer than mesosetae (Fig. 13). Th. I–Abd. IV with a complete set of separate dorsal tubercles: Di, De, Dl and L (absent from Th. I, as usual); tubercles Dl and L on all these segments, especially on Abd. IV, clearly enlarged. Tubercles Di, De and Dl on Abd. V fused and forming two long digitations, Abd. VI also bilobed, with two digitate tubercles. Lengths of these elongated tubercles presented in Table 2; these usually only 7–10 times shorter than total body. Traumatic absence of some of them more often observed on Abd. IV. Dorsal chaetotaxy notably plurichaetotic (Fig. 2, Table 3), sensillar formula as 22/22211; sensilla on thoracic terga present on tubercles De and Dl, on Abd. I–III present on De and L, on Abd. IV only on De, and on Abd. V on tips of digitations (Di+De+Dl).
Ventral chaetotaxy as in Figs 4–5 and Table 3, setae on first abdominal sterna short and thin, growing stronger towards abdominal tip. VT with 4+4(5) distal chaetae. Furcal area without tiny setulae (mi). Males with a group of curved thickened setae on a transverse swelling anterior to genital plate (Fig. 16). Unguis with a strong inner tooth, laterobasal pair of setae on pretarsi small and poorly visible (Fig. 15). Chaetotaxy of legs as in Table 3.
Etymology. The name of the new species (feminine in gender, from the Latin oblitus(a) meaning forgotten) reflects the quite long temporal gap between its capture in nature and the description.
Affinities. The status of R. oblita sp. nov. as a distinct species can hardly be questioned. The most striking distinctive feature of the new species is undoubtedly the presence of six finger-shaped tubercles on the last three abdominal segments, this clearly bringing it closer to four of the five known species of the genus. The degree of development of these outgrowths in the new species is lower, as in all congeners these are developed not only on the abdomen, but also on the head and thorax. Thus, in R. yoshiiana Deharveng, 1988, the type species of the genus, all tubercles on the body, including the head, are elongated and finger-shaped, whereas only tubercles Di on the abdomen of R. malayana (Yosii, 1976) are not elongated. Rambutanura dawydoffi is characterized by digitate tubercles on the head, the last abdominal segments and laterally on Th. II–Abd. III, whereas tubercles in the mid parts of the terga are low. In R. carcharia, only tubercles Di on Th. I–Abd. IV are not elongated. However, the identical tuberculization, the plurichaetosis on the antennae and dorsal tubercles, a slightly increased number of dorsal sensilla, as well as such an unusual character as the absence of dorsal sensilla from AOIII (which is also characteristic at least of R. yoshiiana, R. malayana and R. carcharia) obviously indicate a fairly close relationship of R. oblita sp. nov. with the other congeners that show a more pronounced elongation of dorsal tubercles across the body.
The presence of only a small number of finger-like tubercles in the new species makes it comparable to the only Chinese representative of the genus, R. hunanensis Jiang & Dong, 2018 (in Dong et al. 2018), which is characterized by prominent, but not finger-shaped tubercles. That species can easily be distinguished from R. oblita sp. nov., for example, by the presence of a large number of dorsal sensilla (444/44444, including those on Th. I and on tubercles Di on all terga in R. hunanensis, vs 22/ 22211 in R. oblita sp. nov.).
It seems noteworthy that the attribution of R. hunanensis to the genus Rambutanura has required a significant expansion of the latter’s original diagnosis, in particular the inclusion of species with tubercles both swelling or finger-like in shape (Dong et al. 2018, p. 384). This expansion has led to the problem of separating the genus Rambutanura from W. vicina (Denis, 1934), the type species of the genus Womersleya Denis, 1948, which shows the same arrangement of tubercles as Rambutanura, but… differs from that genus by the absence of any digitation on the head and tergites and a much lower plurichaetosis (Deharveng 1988, p. 714–715). When erecting the genus Rambutanura, Deharveng(1988,p.715) considered the differentiation of digitations as a major apomorphic character, and placed this genus in the “digitanurian” line (Deharveng 1987) together with Digitanura Deharveng, 1987, a second South Asian genus with finger-shaped tubercles at the end of the abdomen, differing from Rambutanura in the arrangement of the dorsal tubercles on the head and Abd. V (tubercles Di separate). The situation is complicated since, according to the recent cladistic analysis (Smolis & Paśnik 2020), the genus Womersleya, along with other genera of the ‘bilobellan lineage’ of the tribe Paleonurini, was transferred to the tribe Neanurini, while the genus Rambutanura remained in the Paleonurini, as well as Pronura Delamare Deboutteville, 1953 of the same ‘bilobellan lineage’ (see Bellinger et al. 1996 –2024). This ‘bilobellan lineage’ also contains species, such as Bilobella digitata Cassagnau, 1967, which tend to form finger-shaped tubercles at the end of the abdomen, although overall they are not very similar to the described species. All this quite clearly indicates that the existing generic and tribal division of the subfamily Neanurinae is rather far from ideal and in need of further attention.
The second, no less intriguing trait of the new species, is undoubtedly the chaetotaxy of the fourth antennal segment. The vast majority of the known species in the subfamily are characterized by the existence of a constant and characteristic arrangement of setae on the dorsal side of Ant. IV (Deharveng 1981) and this feature is the most important and least controversial criterion for belonging to Neanurinae (Smolis & Paśnik 2020, p. 498). Plurichaetosis of ordinary mou setae on Ant. IV was already indicated in the original diagnosis of the genus (Deharveng 1988) and it seems to be typical of all known species of the genus, including R. oblita sp. nov. But the increased and rather unstable number of blunt dorsal sensilla on Ant. IV has previously not been noted among the species of the subfamily, this obviously being a unique character of the new species.
description: Published as part of Babenko, Anatoly & Antipova, Maria, 2024, A new species of the genus Rambutanura Deharveng, 1988 from southern Vietnam (Collembola, Neanuridae), pp. 142-150 in Zootaxa 5486 (1) on pages 143-148, DOI: 10.11646/zootaxa.5486.1.7, http://zenodo.org/record/13209835