<p>Gustina populacija i sezonske fluktuacije u<br />brojnosti voluharica i mi&scaron;eva (Rodentia:<br />Muridae) predstavljaju najvažniji faktor u<br />diverzitetu, distribuciji i abundanci<br />ektoparazitskih vrsta. Epidemiolo&scaron;ki modeli<br />ukazuju da bi povećanje gustine populacija<br />glodara dovelo i do povećanja gustine<br />populacija ektoparazita zbog postojanja većeg<br />izbora preferentnih habitata (jedinke domaćina).<br />Voluharice i mi&scaron;evi predstavljaju grupu glodara<br />koja ima izuzetan vektorski potencijal za veliki<br />broj vrsta iksodidnih krpelja (Acari: Ixodidae),<br />naročito triksenih i diksenih vrsta. Ako se<br />gustina populacija potencijalnih domaćina<br />(voluharica i mi&scaron;eva) posmatra kao stani&scaron;te za<br />iksodidne krpelje, tada se i meĎu njima mogu<br />uočiti razlike koje u kvalitativnom ili<br />kvantitativnom smislu podržavaju različite<br />gustine populacija krpelja. Većina vrsta glodara<br />zbog svojih &scaron;irokih areala, sezonskih migracija i<br />fluktuacija brojnosti predstavlja jednu vrstu<br />specifičnog &bdquo;epidemiolo&scaron;kog mosta&ldquo; koji je<br />odgovoran za održavanje visokih gustina<br />populacija krpelja u okviru odreĎenih stani&scaron;ta,<br />ali, &scaron;to je jo&scaron; značajnije, i prostorno preno&scaron;enje<br />pojedinih vrsta iksodidnih krpelja van okvira<br />datog habitata. Na osnovu dokazanog<br />vektorskog potencijala glodara, utvrĎen je i cilj<br />istraživanja koji podrazumeva tačno<br />odreĎivanje sezonske fluktuacije i prostorne<br />disperzije voluharica i mi&scaron;eva na odabranim<br />lokalitetima, utvrĎivanje dinamike populacija<br />prikupljenih krpelja iz prirode i brojnosti krpelja<br />prisutnih na domaćinu, vektorsku i<br />ektoparazitsku povezanost glodara i krpelja u<br />odnosu na tip habitata, meteorolo&scaron;ke parametre<br />(sezonu), uzrasnu klasu i pol glodara. TakoĎe će<br />se razmatrati i četiri postavljene radne hipoteze<br />koje se tiču odnosa glodari &ndash; krpelji: (1) broj<br />različitih stadijuma krpelja na individuama<br />domaćina se povećava sa povećanjem starosne<br />grupe (mase tela) domaćina, (2) broj različitih<br />stadijuma krpelja na individuama domaćina se<br />smanjuje sa povećanjem gustine populacije<br />domaćina, (3) veći broj različitih stadijuma<br />krpelja na individuama domaćina se konstatuje<br />na ženkama, nego na mužjacima i (4) najveći<br />broj parazitirajućih stadijuma krpelja se nalazi<br />na glavi domaćina. Tokom četvorogodi&scaron;njeg<br />ispitivanja (od 2008. do 2011. godine) sezonske<br />dinamike glodara na lokalitetima Apatin,<br />Bogojevo, Labudnjača (Kamari&scaron;te) i Čelarevo<br />ukupno je izlovljeno 2.736 jedinki, od kojih je<br />najbrojnija vrsta A. terrestris, zatim slede: A.<br />agrarius, A. flavicollis, A. sylvaticus i C.<br />glareolus. Ukupan broj konstatovanih krpelja<br />iznosio je 257. Krpelji su pripadali sledećim<br />vrstama i razvojnim stadijumima: I. ricinus<br />(larve i nimfe), I. trianguliceps (larve), D.<br />marginatus (larve i nimfe), H. concinna (larve i<br />nimfe) i R. sanguineus (larve i nimfe). U okviru<br />proučavanih ekosistema, glodari imaju značajnu<br />ulogu u održavanju krpeljskih populacija<br />različitih vrsta, omogućavajući i olak&scaron;avajući<br />transstadijalni kontinuitet u ciklusu razvića.<br />Dalje, na osnovu bioekolo&scaron;kih karakteristika, a<br />naročito arela kretanja za vreme perioda<br />intenzivne ishrane i parenja, sve ispitivane vrste<br />glodara predstavljaju i veoma dobre vektore<br />determinisanih vrsta iksodidnih krpelja izmeĎu<br />različitih tipova stani&scaron;ta, obezbeĎujući im<br />prostornu i vremensku disperziju, &scaron;to je od<br />velikog ekolo&scaron;kog, medicinskog i veterinarskog<br />značaja.</p> / <p>The population density and seasonal fluctuations<br />of voles and mice (Rodentia: Muridae) are the<br />most important factors in the diversity,<br />distribution and abundance of ectoparasites.<br />Epidemiological models indicate that an increase<br />in the rodent population density could stimulate<br />an increase in population density of ectoparasites<br />due to the greater variety of preferred habitat<br />(individual hosts). Voles and mice are a group of<br />rodents that have exceptional vector potential for<br />a large number of ixodid ticks species (Acari:<br />Ixodidae), especially tree-host and two-host<br />species. If the densities of the potential host<br />population (voles and mice) are observed as the<br />habitats for ixodid ticks, the qualitative and<br />quantitative differences among them are<br />noticeable, so as different species diversity and<br />population densities of ixodid ticks. Because of<br />the wide ranges of activity, seasonal migrations<br />and population size fluctuations, most rodent<br />species represent a specific type of an<br />&quot;epidemiological bridge&quot; which is responsible<br />for the maintenance of high population density<br />of ticks within certain habitats, but more<br />importantly, the spatial transfer of certain ixodid<br />tick species beyond the boundaries of the certain<br />habitat. Based on the proven vector potential of<br />rodents, the aims of the research were to<br />determine: the seasonal fluctuations and spatial<br />dispersion of voles and mice at selected<br />localities, the dynamics of tick populations<br />collected from nature and obtained from the<br />hosts, vector and ectoparasitic relation between<br />rodents and ticks concerning the type of habitat,<br />meteorological parameters (season), age classes<br />and gender. The four hypotheses will be<br />reviewed: (1) the number of different stages of<br />ticks on the hosts increases with the age group<br />(body mass) of the host, (2) the number of<br />different stages of ticks on the hosts decreases<br />with increasing host population density, (3) a<br />larger number of ticks obtained from the hosts<br />are found on the females than on the males, and<br />(4) the highest number of ticks could be found<br />on the host&rsquo;s head. The four year study (2008 to<br />2011) of seasonal dynamics of voles and mice<br />was conducted at four localities: Apatin,<br />Bogojevo, Labudnjača (Kamari&scaron;te) and<br />Čelarevo. The total of 2.736 rodent specimens<br />were caught. The most numerous species was A.<br />terrestris, followed by: A. agrarius, A .<br />flavicollis, A. sylvaticus and C. glareolus. The<br />total number of identified ticks was 257,<br />belonging to the following species and<br />developmental stages: I. ricinus (larvae and<br />nymphs), I. trianguliceps (larvae), D.<br />marginatus (larvae and nymphs), H. concinna<br />(larvae and nymphs) and R. sanguineus (larvae<br />and nymphs). Within the studied ecosystems,<br />rodents play a significant role in maintaining<br />different species of tick populations, enabling<br />and facilitating transstadial continuity in the life<br />cycles. Furthermore, based on bio-ecological<br />characteristics, especially areal activity during<br />the period of intensive feeding and mating, all<br />observed rodent species were very good vectors<br />of certain ixodid tick species among different<br />types of habitats, providing them spatial and<br />temporal dispersion, which is of great<br />ecological, medical and veterinary importance.</p>

Water from Mantua reservoir has, during some years, exhibited reddish-brown staining when used by Brigham City for irrigation. I propose that seasonal fluctuations in the reservoir chemistry create an environment conducive to dissolving iron from the iron-rich sediments, which subsequently precipitate during irrigation, resulting in a staining event. These conditions are produced by chemical and biological decomposition of organic matter, coupled with isolation of the hypolimnetic waters, which results in seasonal low concentrations of dissolved oxygen in these waters. Under these specific circumstances, anaerobic conditions develop creating a geochemical environment that causes iron and manganese reduction from Fe(III) to Fe(II) and Mn(IV) to Mn(II), respectively. These reducing conditions facilitate reduction-oxidation (redox) chemical reactions that convert insoluble forms of iron and manganese found in the reservoir sediments into more soluble forms. Consequently, relatively high amounts of dissolved iron and manganese are generated in the bottom waters immediately adjacent to the benthic sediments of the reservoir. Water withdrawn from a bottom intake pipe during these periods introduces iron-rich water into the distribution system. When this water is exposed to oxygen, reoxidation shifts redox equilibrium causing precipitation of soluble Fe(II) and Mn(III) back to highly insoluble Fe(III) and Mn(IV). The precipitant appears on contact surfaces as the aforementioned ferric stain. This research focuses specifically on the iron chemistry involved and evaluates this hypothesis using various measurements and models including field data collection, computer simulations, and bench-scale testing to validate the processes proposed.