Appendisotoma Stach, 1947

Potapov, Mikhail, Babenko, Anatoly, Bu, Yun, Bayartogtokh, Badamdorj, Gulgenova, Ayuna & Luan, Yun-Xia, 2024, Taxonomy of the Cryptopygus complex. IV. Cyclomorphosis in three species of Appendisotoma and description of a new species from Kazakhstan (Collembola, Isotomidae), Zootaxa 5453 (4), pp. 487-510 : 488

Genus Appendisotoma Stach, 1947

Here we follow the characterization of the genus proposed formerly by Christiansen & Bellinger (1998) and complemented by Potapov et al. (2013). Due to fusion of the two last abdominal segments, the latter diagnosis corresponds to Cryptopygus -complex of genera, completed with the following characters:

- S-chaetae placed in posterior position on body tergites (although the character is unknown for the most North American species)

- mucro with 3 or more teeth

- at least 6+6 ocelli

- chaetae on anterior side of manubrium present

More reliable diagnosis of the genus is impossible so far because of the poor knowledge of morphology of the American species. The following characters are variable: number of s-chaetae on body tergites, apical whorl on tibiotarsi with 7 or 11 chaetae, presence/absence of apical lobe on dens, presence/absence of anal spines (often occur among North American species), and length of furca. The genus appears to be an odd member among the genera of the Cryptopygus -complex ( Potapov et al. 2013) and might be closely related to Proisotoma s. str. belonging to the Proisotoma -complex (see the Ecological and taxonomic value of cyclomorphosis of Appendisotoma part). At least several, if not the most, species of the genus have tibiotarsi with all T-chaetae (apical whorl with 11 chaetae, e.g. Fig. 4 ), which are highly unusual in subfamily Anurophorinae , and thus indicate a possible relation of Appendisotoma congeners to the subfamily Isotominae . Another typical character of Isotominae is the presence of 4 chaetae on proximal field of labium ( Fig. 45 ) that is shown in A. sibirica and A. absoloni . The differences between all the species of Appendisotom a studied by us are given in Table 1 .

Figures

FIGURES 1–7. Appendisotoma bisetosa, winter form: 1, macrochaetae and s-chaetae on body tergites; 2, chaetotaxy of Abd. II–IV, s-chaetae on Abd. IV encircled, macrochaetae connected by dotted line; 3, tibiotarsus, lateral view; 4, apical part of tibiotarsus, outer view; 5, Ant.I–III, dorsal view of right antenna, one additional bms on Ant. II not shown on figure; 6, furca, posterior view, chaetae of central area of manubrium encircled; 7, dens, outer view. Abbreviations: s—s-chaetae, ms—mschaetae, bms—basal ms-chaetae, os—outer s-chaetae of AO, ls—lateral s-chaetae of AO.

FIGURES 43–49. Appendisotoma sibirica: 43, s-chaetae on body tergites; 44, Abd.IV–VI (microchaetae not shown on Abd.VI and shown only as sockets on Abd.V); 45, labial palp, simplified; 46, apical part of tibiotarsus III, outer view; 47, laterodistal chaetae of ventral tube; 48, furca, anterior view; 49, Ant.I–III, dorsal view of left antenna.Abbreviations: pr—proximal chaetae, other abbreviations as on Figs 1–7.