FIRST REPORT OF THE MILLIPEDE Oxidus gracilis ( DIPLOPODA , POLYDESMIDA , PARADOXOSOMATIDAE ) IN SERBIA

Ten specimens of Oxidus gracilis (C. L. Koch, 1847) were collected in the hothouse of Botanical Garden “Jevremovac” in Belgrade. This is the first finding of an alien millipede species in Serbia.


INTRODUCTION
Presently, the Serbian millipede fauna comprises 103 species (ANTIĆ et al., 2013(ANTIĆ et al., , 2014;;ANTIĆ, 2015;JOVANOVIĆ and ANTIĆ, 2015).The family Paradoxosomatidae belongs to the order Polydesmida, the second largest order of millipedes in Serbia with two families and 23 species (ANTIĆ et al., 2013).Oxidus gracilis (C.L. Koch, 1847) is the second representative of the family Paradoxosomatidae and the 104th millipede species in Serbia.To date, millipede species alien to Europe were not registered in Serbia (DAISIE, 2008), but considering that O. gracilis is a widespread successful anthropochore (STOEV, 2004), it is not surprising that the network of pathways among European greenhouses and hothouses travelled by this species eventually has come to include Serbia.

MATERIALS AND METHODS
Ten specimens of Oxidus gracilis were collected in the hothouse of Botanical Garden "Jevremovac" in Belgrade.Specimens were preserved in 70% ethanol and examined at the laboratories of Institute of Zoology, Faculty of Biology, University of Belgrade, using Carl Zeiss Jena Technival 2 binocular stereomicroscope.Gonopods were dissected and mounted in glycerin as temporary microscopic preparations and observed under a Carl Zeiss Axioscope 40 microscope.Picture of the living specimens was made with a Canon PowerShot SX530 HS digital camera.

RESULTS AND DISCUSSION
Oxidus gracilis (C.L. Koch, 1947) (Fig. 1   Origin: The native range of the species is East or Southeast Asia (STOEV and KORSÓS, 2010).COOK (1911) stated that the species originates from the East Indies.STOEV and KORSÓS (2010) expressed the assumption about Ryukyu Islands of Japan as the possible site of origin of the genus, based on the finding of populations of the two congeners of O. gracilis in the natural forest habitats of these islands.Three out of four congeners of O. gracilis are distributed in Japan, but not only in the Ryukyu Islands (NGUYEN and SIERWALD, 2013).Japan, as a native territory of O. gracilis, was previously indicated by GOLOVATCH and KIME (2009), who noticed that the species favors higher altitudes in Middle America which could possibly reflect a northern temperate origin.

Habitat:
O. gracilis has a high adaptive potential which enables it to populate various types of terrestrial natural habitats, agricultural, horticultural and artificial areas and those under varying human influence, as well as subterranean habitats (STOEV and KORSÓS, 2010).Unable to survive longer than two hours under the temperature of -4°C, the species can only be found in the hothouses in the northern regions (STOEV and KORSÓS, 2010).
Specimens from the hothouse of the Botanical Garden "Jevremovac" in Belgrade were found in shaded conditions under stones and branches, or walking and mating on a moist soil partially covered in moss (Figs 1 and 2).The species seems to have established a thriving population considering the observed reproductive behaviour and juveniles of different stadia.Temperature at the hothouse varies between 19-24ºC.This is the first record of a myriapod from a hothouse/greenhouse in Serbia.Controlled temperature and humidity, as well as the variety of plant species have probably created a proper environment for some other alien myriapod species, which could be a suitable subject for more comprehensive study.
Material studied: Four adults (3 females and 1 male) and 6 juveniles were collected on 28 September 2015 by Dragan Antić in the hothouse of the Botanical Garden "Jevremovac" in Belgrade.Details on biology of this well-known species have been given by SCHUBART (1934), CAUSEY (1943) and BLOWER(1985).It is the only millipede species alien to Europe with established populations in some natural ecosystems on the continent and in the Caucasus(STOEV et al., 2010).Its bisexual populations are maintained by laying eggs during the whole year(CAUSEY, 1943;BLOWER, 1985).