Metabolic and Endocrine Responses of Desert-Adapted Mice Reproductive System to Increased Salinity

From an evolutionary point of view, reproduction timing is an important adaptation which enables the transfer of genetic properties, thus enabling species continuation. Rodents inhabiting arid environments need reliable cues for triggering their reproduction. Results of previous studies showed that increased dietary salinity plays an important role as an ultimate regulator for desert adapted rodents＇ reproductive system. The authors aimed discovering pathways by which high salinity can affect the reproductive system and metabolic status of desert adapted common spiny mice, Acomys cahirinus. Mice were challenged with osmotic stress, water source salinity increased gradually from 0.9% - 5% NaCI under short days （SD） and long days （LD）. The authors assessed leptin and free fatty acid （FFA） levels using ELISA while, SYBR green technology was used for relative receptor expression （RQ） of target genes. Results revealed that serum levels of the hormone leptin were significantly （P 〈 0.05） reduced in salinity treated （ST） mice. Levels of FFA were significantly （P 〈 0.05） increased in LD- and SD-ST-males. In ST-SD females a significant increase （P 〈 0.05） in expression levels of leptin （Ob-Rt） mRNA receptor gene, in ovaries was noted. Aldosteron （Nr3c2） and vasopressin （AVP） mRNA receptor expression genes levels were significantly （P 〈 0.05） increased in both LD- and SD- ST- males.

Bright artificial light at night is associated with increased body mass,poor reproductive success and compromised disease tolerance in Australian budgerigars(Melopsittacus undulatus)

Artificial light at night(ALAN)can cause circadian disruption and result in adverse behavioral and ecologi­cal effects in free-living birds,but studies on captive pet birds as companion animals have been infrequent.We studied the effects of exposure to bright ALAN on body mass,melatonin sulfate levels,reproduction and dis­ease severity in Australian budgerigars(Melopsittacus undulatus)kept in captivity.During the experiment,birds were kept under outdoor temperature,humidity and natural photoperiod from September to December.A total of 48 birds were equally split into 4 groups(6 mating pairs each)and concurrently exposed to ALAN of 200 lux with different duration(0,30,60 and 90 min).Monthly observations were recorded for all dependent parame­ters.ALAN exposure increased mass gain and suppressed melatonin levels in a dose-dependent manner,espe­cially during December.In addition,ALAN exposure in all duration groups decreased egg production and re­duced hatchability from 61%±14%in the ALAN-unexposed control group to 0%in the ALAN-exposed birds.Disease severity was also found to increase in line with the duration of ALAN exposure.In captive M.undu­latus,ALAN exposure was demonstrated to affect photoperiodic regulation with subsequent excess mass gain and reproduction impairment,and increased susceptibility to infections plausibly through duration dose-depen­dent suppression of melatonin.To the best of our knowledge,this is the first study to demonstrate a possible as­sociation between acute bright ALAN of increasing duration and both natural development of infections as well as reproductive cessation in captive birds.Our findings could be used to improve breeding conditions of captive birds.

Effect of conspecific and heterospecific urine odors on the foraging behavior of the golden spiny mouse

The common spiny mouse(Acomys cahirinus)inhibits the foraging activity of the golden spiny mouse(A.russatus).These two sympatric species of spiny mice,which are considered habitat competitors,occur in extreme arid environments.To test this theory of competition,the influence of urinary odors of both conspecific and heterospecific mice on the foraging behavior of A.russatus was studied under controlled laboratory conditions.Twenty adult males,born in captivity and unfamiliar to the odors of the donor mice,were tested in 3 experimental conditions choosing between 2 seed patches that were scented with urine of either heterospecifics(A.cahirinus),conspecifics(A.russatus)or controls(odors of the tested individual).Of the 20 males,12 were also tested with urine of unfamiliar gerbils,bushy-tailed jird,considered as competitors in the field.Both conspecific and heterospecific urine samples from Acomys significantly reduced foraging behavior of A.russatus when compared to the control odor.The inhibitory effect of the Acomys urine does not result from the novelty of chemical stimuli of the urine because no effect was shown with unfamiliar gerbil urine.The findings are in accordance with the general theory that A.cahirinus dominates the foraging activity of A.russatus.We hypothesize that chemical cues in the urine of Acomys spp.might induce a negative effect on the foraging behavior of A.russatus.

Physiological adaptations of small mammals to desert ecosystems

Adaptations of animals to the xeric environment have been studied in various taxonomic groups and across several deserts.Despite the impressive data that have been accumulated,the focus in most of these studies is mainly on the significance of one variable at a time.Here,we attempt to integrate between responses of several physiological systems,challenged by increasing diet and water salinity and extreme temperatures,acquired in different studies of thermo and osmo-regulatory adaptations,of small rodents,to the xeric environment.Studies have shown differen-tial thermoregulatory responses to increased dietary salinity,which were attributed to habitat and habits of the relevant species.In the thermoregulatory studies,a potential adaptive significance of low metabolic rate was demonstrated.From an evolutionary point of view,the most important adaptation is in the timing of reproduction,as it enables the transfer of genetic properties to the next generation in an unpredictable ecosystem,where repro-duction might not occur every year.Results in this aspect show that increased dietary salinity,through an increase in vasopressin plasma levels,plays an important role as a regulator of the reproductive system.We assume that the amount of food existing in the habitat and the amount of reserves in the animal in the form of white adipose tissue are important for reproduction.Photoperiod affects all studied physiological responses,emphasizing the impor-tance of pre-acclimation to seasonal characteristics.We summarize the existing data and suggest neuro-endocrine pathways,which have a central role in these adaptations by affecting thermoregulation,osmoregulation and repro-duction to create the optimal response to xeric conditions.These hypotheses can be used as the basis for future studies.

Suggesting the use of integrated methods for vole population management in alfalfa fields

Human-made agro-ecosystems lack negative feedback controls, which may result in rodent population explosions,causing considerable economic loss and thus increasing human–wildlife conflicts. The traditional solution is theextensive use of rodenticides, which have a negative impact on the environment. In Beit-Sheaan Valley, Israel,which is located on a major route for migrating birds, poisoning of voles may result in the death of birds that preyon the dead voles (e.g. storks and herons). In the present essay we discuss some integrated methods, based on theimplementation of ecological principles in agro-ecosystems, that could be used to decrease the use of rodenticides.The first method is light interference during winter (long scotophase), which can result in the death of the socialvole Microtus socialis kept in enclosures under natural conditions. Under laboratory conditions such interferencecauses a decrease in thermoregulatory ability in the cold. As light interference is a source of pollution, only activevole burrows should be illuminated. The second method involves using the mobile irrigation pipelines to flood thevole burrows and force them to escape into the open, where diurnal birds such as storks and herons will prey onthem. The third method involves the use of nesting boxes for barn owls and stands for diurnal raptors, both ofwhich prey on voles. The great advantage of using an integrated approach is that voles cannot become adapted toany one of the methods. Such integrated methods, together with appropriate treatment of alfalfa fields by farmers,can provide an efficient and sustainable pest control approach.