Trophic cascade driven by behavioral fine-tuning as naïve prey rapidly adjust to a novel predator.

The arrival of novel predators can trigger trophic cascades driven by shifts in prey numbers. Predators also elicit behavioral change in prey populations, via phenotypic plasticity and/or rapid evolution, and such changes may also contribute to trophic cascades. Here, we document rapid demographic and behavioral changes in populations of a prey species (grassland melomys Melomys burtoni, a granivorous rodent) following the introduction of a novel marsupial predator (northern quoll Dasyurus hallucatus). Within months of quolls appearing, populations of melomys exhibited reduced survival and population declines relative to control populations. Quoll-invaded populations were also significantly shyer than nearby, quoll-free populations of conspecifics. This rapid but generalized response to a novel threat was replaced over the following 2 yr with more threat-specific antipredator behaviors (i.e., predator-scent aversion). Predator-exposed populations, however, remained more neophobic than predator-free populations throughout the study. These behavioral responses manifested rapidly in changed rates of seed predation by melomys across treatments. Quoll-invaded melomys populations exhibited lower per-capita seed take rates, and rapidly developed an avoidance of seeds associated with quoll scent, with discrimination playing out over a spatial scale of tens of meters. Presumably the significant and novel predation pressure induced by quolls drove melomys populations to fine-tune behavioral responses to be more predator specific through time. These behavioral shifts could reflect individual plasticity (phenotypic flexibility) in behavior or may be adaptive shifts from natural selection imposed by quoll predation. Our study provides a rare insight into the rapid ecological and behavioral shifts enacted by prey to mitigate the impacts of a novel predator and shows that trophic cascades can be strongly influenced by behavioral as well as numerical responses.

Strategic Timing of Glial HMOX1 Expression Results in Either Schizophrenia-Like or Parkinsonian Behavior in Mice.

Aims: In this original research communication, we assess the impact of shifting the window of glial HMOX1 overexpression in mice from early-to-midlife to mid-to-late life, resulting in two disparate conditions modeling schizophrenia (SCZ) and Parkinson's disease (PD). Mesolimbic hyperdopaminergia is a widely accepted feature of SCZ, while nigrostriatal hypodopaminergia is the sine qua non of idiopathic PD. Although the advent of parkinsonian features in SCZ patients after treatment with antidopaminergic agents is intuitive, subtle features of parkinsonism commonly observed in young, drug-naïve schizophrenics are not. Similarly, emergent psychosis in PD subjects receiving levodopa replacement is not unusual, whereas spontaneous hallucinosis in nonmedicated persons with idiopathic PD is enigmatic. Investigations using GFAP.HMOX1 mice may shed light on these clinical paradoxes. Results: Astroglial heme oxygenase-1 (HO-1) overexpression in mice throughout embryogenesis until 6 or 12 months of age resulted in hyperdopaminergia, hyperkinesia/stereotypy ameliorated with clozapine, deficient prepulse inhibition of the acoustic startle response, reduced preference for social novelty, impaired nest building, and cognitive dysfunction reminiscent of SCZ. On the contrary, astroglial HO-1 overexpression between 8.5 and 19 months of age yielded a PD-like behavioral phenotype with hypodopaminergia, altered gait, locomotor incoordination, and reduced olfaction. Innovation: We conjecture that region-specific disparities in the susceptibility of dopaminergic and other circuitry to the trophic and degenerative influences of glial HMOX1 induction may permit the concomitant expression of mixed SCZ and PD traits within affected individuals. Conclusion: Elucidation of these converging mechanisms may (i) help better understand disease pathogenesis and (ii) identify HO-1 as a potential therapeutic target in neurodevelopmental and neurodegenerative disorders.

Gold nanourchins induce cellular stress, impair proteostasis and damage RNA.

Gold nanoparticles have excellent potential for theranostic applications, but their impact on living cells is only partially understood. Many gold nanoparticles enter cells through endosomes/lysosomes which are linked to different cell organelles and compartments. Our study focuses on the unfolded protein response (UPR) in the endoplasmic reticulum (ER), cytoplasmic RNA-granules and proteostasis, because they are established indicators of cell stress and key regulators of cellular homeostasis. Using HeLa and renal proximal tubule cells as model systems, we show that gold nanourchins reduce cell proliferation, cause ER stress and impair proteostasis. Specifically, gold nanourchins activate the PERK-branch of the UPR, promote RNA oxidation, enhance P-body formation, and accumulate the oxidative stress marker Nrf2 and NFκB in nuclei. Taken together, our study demonstrates that gold nanourchins compromise ER, redox, protein, and RNA homeostasis. These insights provide new information on the cellular responses and molecular changes that gold nanourchins elicit in mammalian cells.

I Environmental DNA sampling is more sensitive than a traditional survey technique for detecting an aquatic invader.

Effective management of alien species requires detecting populations in the early stages of invasion. Environmental DNA (eDNA) sampling can detect aquatic species at relatively low densities, but few studies have directly compared detection probabilities of eDNA sampling with those of traditional sampling methods. We compare the ability of a traditional sampling technique (bottle trapping) and eDNA to detect a recently established invader, the smooth newt Lissotriton vulgaris vulgaris, at seven field sites in Melbourne, Australia. Over a four-month period, per-trap detection probabilities ranged from 0.01 to 0.26 among sites where L. v. vulgaris was detected, whereas per-sample eDNA estimates were much higher (0.29-1.0). Detection probabilities of both methods varied temporally (across days and months), but temporal variation appeared to be uncorrelated between methods. Only estimates of spatial variation were strongly correlated across the two sampling techniques. Environmental variables (water depth, rainfall, ambient temperature) were not clearly correlated with detection probabilities estimated via trapping, whereas eDNA detection probabilities were negatively correlated with water depth, possibly reflecting higher eDNA concentrations at lower water levels. Our findings demonstrate that eDNA sampling can be an order of magnitude more sensitive than traditional methods, and illustrate that traditional- and eDNA-based surveys can provide independent information on species distributions when occupancy surveys are conducted over short timescales.