TAXONOMIC ELEMENTS ON UROPODA GRESSITTI HIRSCHMANN, 1972 FROM SOUTH GEORGIA (ACARI: UROPODINA: UROPODIDAE)

Female, deutonymph, protonymph and larva of the species Uropoda gressitti Hirschmann, 1972 are described, based on specimens collected from South Georgia by the British Antarctic Survey in 1981. Original drawings of adult and immature stages are presented with a key to the Uropodina species of the Subantarctic region.


INTRODUCTION
Uropodina mites are small (300 -1200 µm), yellow or reddish-brown members of the soil fauna; they inhabit soil, leaf litter, moss, lichens and bark of tree. Several species live in association with other arthropods and vertebrates. More than two thousand species are known worldwide (Wiśniewski and Hirschmann 1993). The Antarctica is the most poorly studied region of the world, up to now only four Uropodina species are reported from this region.
The first two species found in the material collected during the German South-Polar Expedition (Possession Island), were described as Opisthope crozetensis Richters, 1907 and Piracarus crozetensis Richters, 1907(Richters 1907. Later Hirschmann (1974) placed these two species into the genus Uropoda Latreille, 1806 resulting to the new combination Uropoda crozetensis (Richters, 1907), but Hirschmann (1974) needed to change the name of Piracarus crozetensis to Uropoda richtersi Hirschmann, 1974 to avoid homonymy. Some years later Hirschmann (1972) observed soil material from the South Georgia and described two other new species: Uroobovella gressitti Hirschmann, 1972and Uropoda gressitti Hirschmann, 1972. Unfortunately Hirschmann (1972 gave only a brief description of females of these species and he did not find the immature stages of the latter species.
In 2008, I spent two weeks in the Natural History Museum, in London, where I studied the unsorted soil samples of the Arachnida collection. I found several specimens of Uropoda gressitti Hirschmann, 1972 in the materials collected during the British Antarctic Survey, 1981. Females, deutonymphs, protonymphs and larvae of U. gressitti, were observed and their description and/or redescription is provided in the present paper.

MATERIALS AND METHODS
Specimens were cleared in lactic acid mounted on slides and later stored in alcohol. Drawings were made using a drawing tube at 16 and 40x magnification. All specimens examined are deposited in the Arachnida collection of the Natural History Museum, London (UK). Abbreviations: h1-h3, hypostomal setae, h4, capitular setae, St1-St5, sternal setae. Measurements are given in micrometers (µm), width of idiosoma was taken at the level of the coxae IV.
Legs -Bearing smooth and simple setae, the first leg with claws. Ventrianal shield without ornamentation and bearing four pairs of smooth and needle-like setae (ca. 10-11 µm). Only one pair smooth and needle-like adanal setae (ca. 8 -9 µm) present. Tritosternum with narrow basis, its laciniae smooth and divided into four branches ( Figure 2B).
Tritosternum with narrow basis, its laciniae smooth and divided into three branches ( Figure 2E).
Tritosternum with wide basis, its laciniae smooth and divided into four branches (Fig. 2F).
Occurrences -The specimens were found in South Georgia: Maiviken, Bay of Isles, Prince Olaf Harbour and West Bay. Hirschmann (1972) described this species based on females (the number of the studied specimens is not given in Hirschmann's original description) and the description comprises only a few sentences; several characters (epistome, tritosternum, etc.) are missing from the description. The present paper thus provides a complete description of this species based on more than 30 females; it also provides the description of immature stages. Specimens presently examined are shorter in length than the specimens described by Hirschmann (1972) (570 µm long and 450 µm wide), however any other significant differences was found in the studied specimens. During my investigation I found only the larvae, nymphs and females, hence I suggest this species could be parthenogenetic, which is typical for soil inhabiting species, forming low-density populations, especially in temperate and cool zones (Błoszyk et al. 2004). Hirschmann (1972) found this species in moss and lichen, similar to the newly collected specimens, which were caught in moist moss. To help Uropodina species identification from Subantarctic region, we proposed a key including four species. The other three Uropodina species known from this region are as follows:

CONCLUSION
Uropoda crozetensis (Richters, 1907) Opisthope crozetensis Richters, 1907: 284-285. Figures 10-13, on  Notes to Richters' species: Richters (1907) found every immature stage and both sexes of these two species. Unfortunately Richters (1907) illustrated the dorsal and ventral idiosoma of these species in photos, several characters (e.g. gnathosoma, etc) are not presented in the figures, hence the identification of these species on the basis of Richters's (1907)