Using Classical and Operant Conditioning to Train a Shifting Behavior in Juvenile False Water Cobras (Hydrodynastes gigas).

All animals have the capacity to learn through operant conditioning and other types of learning, and as a result, zoos and other animal care facilities have shifted towards the use of positive reinforcement training to shape the behavior of animals under their care. Training offers animals the choice to participate in their own husbandry routines and veterinary procedures, while also providing mental stimulation. By adopting these practices, the welfare of animals in human care has improved, but it has not been applied equally across taxa. Snakes are frequently overlooked in the discussion of choice and control in a captive setting, likely due to the historical misinterpretation of their intelligence and behavioral needs. In this study, a shaping plan was developed for 28 juvenile false water cobras (Hydrodynastes gigas), a rear-fanged venomous species, from four clutches. Snakes were rewarded with food when completing behaviors related to the ultimate goal of following a target into a shift container. The purpose of this study is to incorporate the trained behaviors in routine husbandry practices, while preventing unnecessary stress in the snakes and risk to the keeper.

Diversity and relative abundance of ammonia- and nitrite-oxidizing microorganisms in the offshore Namibian hypoxic zone.

Nitrification, the microbial oxidation of ammonia (NH3) to nitrite (NO2-) and NO2- to nitrate (NO3-), plays a vital role in ocean nitrogen cycling. Characterizing the distribution of nitrifying organisms over environmental gradients can help predict how nitrogen availability may change with shifting ocean conditions, for example, due to loss of dissolved oxygen (O2). We characterized the distribution of nitrifiers at 5 depths spanning the oxic to hypoxic zone of the offshore Benguela upwelling system above the continental slope off Namibia. Based on 16S rRNA gene amplicon sequencing, the proportional abundance of nitrifiers (ammonia and nitrite oxidizers) increased with depth, driven by an increase in ammonia-oxidizing archaea (AOA; Thaumarchaeota) to up to 33% of the community at hypoxic depths where O2 concentrations fell to ~25 µM. The AOA community transitioned from being dominated by a few members at oxic depths to a more even representation of taxa in the hypoxic zone. In comparison, the community of NO2--oxidizing bacteria (NOB), composed primarily of Nitrospinae, was far less abundant and exhibited higher evenness at all depths. The AOA:NOB ratio declined with depth from 41:1 in the oxic zone to 27:1 under hypoxia, suggesting potential variation in the balance between NO2- production and consumption via nitrification. Indeed, in contrast to prior observations from more O2-depleted sites closer to shore, NO2- did not accumulate at hypoxic depths near this offshore site, potentially due in part to a tightened coupling between AOA and NOB.

Alarm Odor Compounds of the Brown Marmorated Stink Bug Exhibit Antibacterial Activity.

Some insects release scented compounds as a defense against predators that also exhibit antimicrobial activity. Trans-2-octenal and trans-2-decenal are the major alarm aldehydes responsible for the scent of Halyomorpha halys, the brown marmorated stink bug. Previous research has shown these aldehydes are antifungal and produce an antipredatory effect, but have never been tested for antibacterial activity. We hypothesized that these compounds functioned similarly to the analogous multifunctional action of earwig compounds, so we tested whether these aldehydes could inhibit the growth of bacteria. Disk diffusion assays indicated that these aldehydes significantly inhibited the growth of Methicillin-resistant Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, in vitro. Moreover, mealworm beetles (Tenebrio molitor) coated in stink bug aldehydes showed a substantial reduction in bacterial colonization compared to vehicle-treated insects. These results suggest that brown marmorated stinkbug aldehydes are indeed antibacterial agents and serve a multifunctional role for this insect. Therefore, stinkbug aldehydes may have potential for use as chemical antimicrobials.

Acidification Enhances Hybrid N2O Production Associated with Aquatic Ammonia-Oxidizing Microorganisms.

Ammonia-oxidizing microorganisms are an important source of the greenhouse gas nitrous oxide (N2O) in aquatic environments. Identifying the impact of pH on N2O production by ammonia oxidizers is key to understanding how aquatic greenhouse gas fluxes will respond to naturally occurring pH changes, as well as acidification driven by anthropogenic CO2. We assessed N2O production rates and formation mechanisms by communities of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in a lake and a marine environment, using incubation-based nitrogen (N) stable isotope tracer methods with 15N-labeled ammonium (15[Formula: see text]) and nitrite (15[Formula: see text]), and also measurements of the natural abundance N and O isotopic composition of dissolved N2O. N2O production during incubations of water from the shallow hypolimnion of Lake Lugano (Switzerland) was significantly higher when the pH was reduced from 7.54 (untreated pH) to 7.20 (reduced pH), while ammonia oxidation rates were similar between treatments. In all incubations, added [Formula: see text] was the source of most of the N incorporated into N2O, suggesting that the main N2O production pathway involved hydroxylamine (NH2OH) and/or [Formula: see text] produced by ammonia oxidation during the incubation period. A small but significant amount of N derived from exogenous/added 15[Formula: see text] was also incorporated into N2O, but only during the reduced-pH incubations. Mass spectra of this N2O revealed that [Formula: see text] and 15[Formula: see text] each contributed N equally to N2O by a "hybrid-N2O" mechanism consistent with a reaction between NH2OH and [Formula: see text], or compounds derived from these two molecules. Nitrifier denitrification was not an important source of N2O. Isotopomeric N2O analyses in Lake Lugano were consistent with incubation results, as 15N enrichment of the internal N vs. external N atoms produced site preferences (25.0-34.4‰) consistent with NH2OH-dependent hybrid-N2O production. Hybrid-N2O formation was also observed during incubations of seawater from coastal Namibia with 15[Formula: see text] and [Formula: see text]. However, the site preference of dissolved N2O here was low (4.9‰), indicating that another mechanism, not captured during the incubations, was important. Multiplex sequencing of 16S rRNA revealed distinct ammonia oxidizer communities: AOB dominated numerically in Lake Lugano, and AOA dominated in the seawater. Potential for hybrid N2O formation exists among both communities, and at least in AOB-dominated environments, acidification may accelerate this mechanism.