Isotopenola nilgiris ( Denis, 1947 ) Denis, 1947

Potapov, Mikhail, Babenko, Anatoly, Fjellberg, Arne & Greenslade, Penelope, 2009, Taxonomy of the Proisotoma complex. II. A revision of the genus Subisotoma and a description of Isotopenola gen. nov. (Collembola: Isotomidae), Zootaxa 2314, pp. 1-40 : 36-37

Isotopenola nilgiris ( Denis, 1947) comb. nov.

Fig. 117 , Tab. 2

Proisotoma nilgiris Denis, 1947: 102 .

Material. We have examined a single (possibly type) specimen from J.R. Denis collection, labeled as India, Nilgiris , Devarsgola, Tea exper. station, F. van Emden, 1946 ( MNHN).

Affinity. This species is listed among Ballistura on the Collembola .org web-site ( Bellinger et al., 1996 – 2009) but clearly differs from all studied Ballistura in having a complete B-row of tibiotarsal chaetae (the presence of unpaired B4/5 is a unique character of the Ballistura / Folsomides evolutionary lineage in Anurophorinae ) and 4 sublobal chaetae (3 in Ballistura ). From all Scutisotoma , of which a few species also lack anterior chaetae on manubruim, it can easily be distinguished by 2 prelabral chaetae (usually 4, rarely 3, in Scutisotoma ), the absence of bms on Ant.3 (always present in Scutisotoma ), reduced number of labial guard chaetae (a rare character in Scutisotoma ) and posterior position of tergal sensilla on abdomen (midtergal in Scutisotoma ). Nor does it conform to the diagnosis of Proisotoma s.str.

In general the species complies with the diagnoses of both Isotopenola gen. nov. and Subisotoma . Like all species of these genera it is characterized by 2 prelabral chaetae, reduced number of labial guard chaetae (only 4 and 5 e-guard chaetae were asymmetrically found near papilla E), 4 sublobal chaetae on outer maxillary lobe, simple maxillary palp, posterior position of tergal sensilla (slightly anterior to p-row, total sensilla 44/ 33334, Fig. 12 ), absence of anterior chaetae on manubrium, tibiotarsi with a complete B-row without unpaired chaeta B4/5 (23–26–27 chaetae as a whole), and poorly differentiated macrochaetae. The shape of dens and mucro is also not different from that in Isotopenola and Subisotoma , although dens has more anterior (7) and posterior (about 12) chaetae ( Fig. 117 ).

Some characters are not typical of either Subisotoma and Isotopenola , such as only 2+2 postlabial chaetae, rather small PAO subequal to the nearest ocellus, VT with only two posterior chaetae and 3 long and distinctly clavate tenent chaetae on Ti.1–3 (3–3– 3 set is very unusual for the family).

The presence of separated ventral setaceous fields on Abd.III, ventral secondary granulation on body, the absence of basal microsensilla and additional sensilla on Ant.3 and full set of microsensilla (11/111) indicates that the species may be a primitive member of the genus Isotopenola .

Figures

FIGURES 116 – 117. Isotopenola spp.: 116, Isotopenola sp. 4 (New Zealand), ventral chaetotaxy of Abd. II – IV (tenaculum not shown); 117, I. nilgiris, dens and mucro, and apical part of dens, dorsal view. sf – II and sf – III – setaceous fields on Abd. II and III, respectively.

FIGURES 9 – 12. Sensillar chaetotaxy of Isotopenola: 9, Isotopenola australis (5,5 / 4,4,4,4,5); 10, Isotopenola delicata sp. nov. (sensillar polychaetosis); 11, Isotopenola loftyensis (sensillar polychaetosis); 12, Isotopenola nilgiris (4,4 / 3,3,3,3,4).