A new species of Tullbergia (Collembola, Tullbergiidae) from Buenos Aires, Argentina

Abstract A new species of Tullbergia from Argentina is described and illustrated; it is differentiated from Tullbergia paranensis by the number of vesicles of postantennal organ, pseudocelli shape and its formulae and the number of dorsal sensilla on Ant. IV. In addition a key for the identification of the members of the family from Argentina is included.


Introduction
Tullbergiidae is a small family with important diversity in the Southern Hemisphere, it has a total of 32 genera and 216 species in the world (Bellinger et al. 2013); but from Argentina only 15 species in 6 genera are known; six of them belong to Tullbergia (Bernava Laborde & Palacios-Vargas, 2008). These species have been found in Argentinian localities such as Buenos Aires, Entre Ríos, Neuquén and Córdoba, always associated to soils with high organic matter content. The lack of studies in other parts of the country could explain their absence in other Argentinian locations.
Tullbergiidae is an euedaphic group of small to very small size Collembola (0.4-1.5 mm except Tullbergia antarctica Lubbock, 1876 which is 3-4 mm) without pigmentation, eyes and furcula. They are very sensitive to ecological changes and so of importance for detecting the impact of different factors on soil ecology. Most important contributions to the taxonomy of the family in Argentina were done by Cassagnau and Rapoport (1962), Izarra (1965Izarra ( , 1969Izarra ( , 1972Izarra ( , 1975 and Rapoport (1962Rapoport ( , 1963 while information about this and other families of Collembola from Argentina is summarized by Bernava Laborde and Palacios-Vargas (2008). In this paper we describe and illustrate a new species of Tullbergiidae which resembles Tullbergia paranensis Izarra,1969.

Materials and methods
Specimens were obtained from soils samples that were processed by Berlese-Tullgreen funnels and preserved in 75% alcohol. Later, slides were prepared in Hoyer's solution. Specimens were studied and measured with a phase contrast microscope.
Ratio head: antenna = 1: 0.8. The relative lengths of Ant. I: II; III; IV are as 1: 1.6; 1.9; 1.8. Ant. III and IV fused dorsally (80 µm). Sense organ of Ant. III with two small sensory rods concealed behind one of the two integumentary folds; in addition there are three thick sensilla clubs, which are rounded at tip; two strongly bend towards each other and not concealed by cuticule. At bases of cuticle, the third sensillum concealed by one tegumentary fold. There is a ventral straight sensillum protected by three setae longer than other ventral setae. Ant. IV furnished with 6 sensilla, 3 of them very thin and long, three thick and short, one distinct subapical pit, one microsensillum and one slightly trilobed apical bulb (Fig. 1). Postantennal organ elliptical 35 µm (range 28-51), as long as width of the Ant. I, consisting of 72 (65-86) simple vesicles lying in two regular rows (Fig. 5).
Dorsal chaetotaxy of thorax and abdomen in Figs 5 and 8 and Table 1. Th. II and III with one lateral microsensillum on each side. Dorsal chaetotaxy of abdomen on Fig.  8. Head ventrally mainly with microsetae, three pairs of postlabial setae, posterior one is macroseta (Fig. 7). Th. II and III ventrally with one pair of setae each and four setae of different sizes on each pleural side.
Distribution. Known only from Punta Lara, the type locality in Buenos Aires Province, Argentina.
Ecology.Tullbergia alcirae sp. n. was found in soil samples. The specimens were taken from the first 10 cm in horizon A, with a density of 624 ± 30 individuals per m 2 . Fredes et al. (2009) have pointed Tullbergia sp. as a good trampling indicator in a recreation area from Miramar, Buenos Aires, Argentina. Tullbergia species in Argentina come from an extensive area with different environmental conditions but the low sampling intensity doesn`t allow to develop any biogeographic hypothesis about its distribution.
Discussion. Tullbergia alcirae sp. n. is similar to T. paranensis because they share the presence of 3 thick curved sensilla on Ant. III, isolated by digitations of the tegumentary fold, and also by the presence of one ventral sensillum and the same shape of pseudocelli. T. alcirae sp. n. differs from T. paranensis in having more vesicles in the postantennal organ (72 vs. 30), the presence of a minute empodial appendix (versus none). It also differs in the pseudocellar formulae (11/122/22221 vs /111/11111). The number of dorsal sensilla on Ant. IV is also different (6 vs. 5).
Tullbergia is supposed to have pseudocelli of type I (Weiner and Najt 1991), but it is of type III in these two species, pointing to the need of a revision of the Tullbergiidae from Argentina.
Variation. Tenent hairs are very slightly capitated and often leg one has one capitated and one acuminate tenent hairs.
Key to species of Tullbergiidae from Argentina (with provinces where they are distributed)