Wild dogma: An examination of recent "evidence" for dingo regulation of invasive mesopredator release in Australia

There is growing interest in the role that apex predators play in shaping terrestrial ecosystems and maintaining trophic cascades. In line with the mesopredator release hypothesis, Australian dingoes (Canis lupus dingo and hybrids) are assumed by many to regulate the abundance of invasive mesopredators, such as red foxes Vulpes vulpes and feral cats Felis catus, thereby providing indirect benefits to various threatened vertebrates. Several recent papers have claimed to provide evidence for the biodiversity benefits of dingoes in this way. Nevertheless, in this paper we highlight several critical weaknesses in the methodological approaches used in many of these reports, including lack of consideration for seasonal and habitat differences in activity, the complication of simple track-based indices by incorporating difficult-to-meet assumptions, and a reduction in sensitivity for assessing populations by using binary measures rather than potentially continuous measures. Of the 20 studies reviewed, 15 of them (75%) contained serious methodological flaws, which may partly explain the inconclusive nature of the literature nvestigating interactions between invasive Australian predators. We therefore assert that most of the “growing body of evidence” for mesopredator release is merely an inconclusive growing body of literature only. We encourage those interested in studying the ecological roles of dingoes relative to invasive mesopredators and native prey species to account for the factors we identify, and caution the value of studies that have not done so.

Marking scallops for release and recapture

Objectives : To develop a method to mark hatchery reared saucer scallops to distinguish them from animals derived from wild populations. Outcomes achieved : Juvenile saucer scallop (Amusium balloti) shells have been successfully marked en masse using 3 chemicals, namely alizarin red S, calcein and oxytetracycline (OTC). Considering spat survival, mark quality and mark duration collectively, the most successful chemical was OTC. Scallop spat immersed for three days in 200 or 300 mg L-1 OTC resulted in good mark incorporation and high survival. Tris was an effective means of buffering pH change during OTC treatment, with no apparent adverse effects to the scallops. The marks from OTC treatment were still visible in live scallops for at least 10 months, even with exposure to natural filtered light during that period. A second discernible shell mark was added 27 days after the first with no evident toxicity to the scallops. A simulated seabed system was designed which provide marked improvements in scallop juvenile survival and growth. Advice on shell marking has been given to QSS by DPI&F, and the first commercial trials have now commenced, with initial results showing successful marking of juvenile scallops at QSS. This research will allow the industry to monitor the survival, growth and movement of specific cohorts of deployed scallops. This will provide valuable feedback to assess the value of the ranching venture, to optimise release strategies, and to develop improved species management plans.

Porous silica-based nanocapsules for targeted and controlled release of biocides

Develops a new technology for the delivery of biocides against agricultural pests, with biocides contained within silica nanocapsules which are themselves protected by an outer envelope, capable of being selectively broken down by the target pest. Will reduce the amount of biocide escaping into the environment, prolong the life of the biocide, reduce biocide usage rates, and reduce undesirable effects on non-target organisms.

Lack of release of bound anthocyanins and phenolic acids from carrot plant cell walls and model composites during simulated gastric and small intestinal digestion

Separately, polyphenols and plant cell walls (PCW) are important contributors to the health benefits associated with fruits and vegetables. However, interactions with PCW which occur either during food preparation or mastication may affect bioaccessibility and hence bioavailability of polyphenols. Binding interactions between anthocyanins, phenolic acids (PAs) and PCW components, were evaluated using both a bacterial cellulose-pectin model system and a black carrot puree system. The majority of available polyphenols bound to PCW material with 60-70% of available anthocyanins and PAs respectively binding to black carrot puree PCW matter. Once bound, release of polyphenols using acidified methanol is low with only similar to 20% of total anthocyanins to similar to 30% of PAs being released. Less than 2% of bound polyphenol was released after in vitro gastric and small intestinal (S.I.) digestion for both the model system and the black carrot puree PCW matter. Confocal laser scanning microscopy shows localised binding of anthocyanins to PCW. Very similar patterns of binding for anthocyanins and PAs suggest that PAs form complexes with anthocyanins and polysaccharides. Time dependent changes in extractability with acidified methanol but not the total bound fraction suggests that initial nonspecific deposition on cellulose surfaces is followed by rearrangement of the bound molecules. Minimal release of anthocyanins and PAs after simulated gastric and S.I. digestion indicates that polyphenols in fruits and vegetables which bind to the PCW will be transported to the colon where they would be expected to be released by the action of cell wall degrading bacteria.

Adsorption and release of biocides with mesoporous silica nanoparticles

In this proof-of-concept study, an agricultural biocide (imidacloprid) was effectively loaded into the mesoporous silica nanoparticles (MSNs) with different pore sizes, morphologies and mesoporous structures for termite control. This resulted in nanoparticles with a large surface area, tunable pore diameter and small particle size, which are ideal carriers for adsorption and controlled release of imidacloprid. The effect of pore size, surface area and mesoporous structure on uptake and release of imidacloprid was systematically studied. It was found that the adsorption amount and release profile of imidacloprid were dependent on the type of mesoporous structure and surface area of particles. Specifically, MCM-48 type mesoporous silica nanoparticles with a three dimensional (3D) open network structure and high surface area displayed the highest adsorption capacity compared to other types of silica nanoparticles. Release of imidacloprid from these nanoparticles was found to be controlled over 48 hours. Finally, in vivo laboratory testing on termite control proved the efficacy of these nanoparticles as delivery carriers for biopesticides. We believe that the present study will contribute to the design of more effective controlled and targeted delivery for other biomolecules.

Surviving the effects of barotrauma: assessing treatment options and a ‘natural’ remedy to enhance the release survival of line caught pink snapper (Pagrus auratus)

A new technique to ameliorate the effects of barotrauma was tested based on observations of pink snapper, Pagrus auratus (Forster), inadvertently piercing their everted stomach with their teeth and releasing trapped swim bladder gases. This technique was termed buccal venting and involved piercing the everted stomach protruding into the buccal cavity or out of the mouth with a 16-gauge hypodermic needle (a practice previously not encouraged). Short-term (~3 days) survival of buccal-vented fish was not significantly different from laterally vented fish nor untreated controls. Both buccal and lateral venting techniques were shown to cause no harm and allowed fish to return to depth. The short-term (1–3 days) post-release survival of line caught snapper was 88% with no significant difference in survival across three depth ranges tested (37–50, 51–100 and 101–180 m). Survival of sublegal pink snapper (<35 cm TL) was not significantly different (P > 0.05) from that of legal-sized fish (≥35 cm TL). Healing of the swim bladder was observed in 27% of pink snapper dissected after ≤3 days in captivity, and healing of stomachs was observed in 64% of pink snapper that had been buccal vented. Relatively high post-release survival rates of line caught pink snapper may offer some protection for snapper stocks where high fishing pressure and legal size restrictions result in the majority of the catch having to be released.

Does lethal control of top-predators release mesopredators? A re-evaluation of three Australian case studies

Top-predators can sometimes be important for structuring fauna assemblages in terrestrial ecosystems. Through a complex trophic cascade, the lethal control of top-predators has been predicted to elicit positive population responses from mesopredators that may in turn increase predation pressure on prey species of concern. In support of this hypothesis, many relevant research papers, opinion pieces and literature reviews identify three particular case studies as supporting evidence for top-predator control-induced release of mesopredators in Australia. However, many fundamental details essential for supporting this hypothesis are missing from these case studies, which were each designed to investigate alternative aims. Here, we re-evaluate the strength of evidence for top-predator control-induced mesopredator release from these three studies after comprehensive analyses of associated unpublished correlative and experimental data. Circumstantial evidence alluded to mesopredator releases of either the European Red Fox (Vulpes vulpes) or feral Cat (Felis catus) coinciding with Dingo (Canis lupus dingo) control in each case. Importantly, however, substantial limitations in predator population sampling techniques and/or experimental designs preclude strong assertions about the effect of lethal control on mesopredator populations from these studies. In all cases, multiple confounding factors and plausible alternative explanations for observed changes in predator populations exist. In accord with several critical reviews and a growing body of demonstrated experimental evidence on the subject, we conclude that there is an absence of reliable evidence for top-predator control-induced mesopredator release from these three case studies. Well-designed and executed studies are critical for investigating potential top-predator control-induced mesopredator release.

Synthesis of Silica Vesicles with Controlled Entrance Size for High Loading, Sustained Release, and Cellular Delivery of Therapeutical Proteins

A rationally designed two-step synthesis of silica vesicles is developed with the formation of vesicular structure in the first step and fine control over the entrance size by tuning the temperature in the second step. The silica vesicles have a uniform size of ≈50 nm with excellent cellular uptake performance. When the entrance size is equal to the wall thickness, silica vesicles after hydrophobic modification show the highest loading amount (563 mg/g) towards Ribonuclease A with a sustained release behavior. Consequently, the silica vesicles are excellent nano-carriers for cellular delivery applications of therapeutical biomolecules.

Increased attractiveness of honeybee hive product volatiles to adult small hive beetle, Aethina tumida, resulting from small hive beetle larval infestation

The small hive beetle, Aethina tumida Murray (Coleoptera: Nitidulidae), is a recent but significant pest of honeybee Apis mellifera L. (Hymenoptera: Apidae) hives in various regions throughout the world, including Eastern Australia. The larval stage of this beetle damages hives when they feed on brood, pollen, and honeycomb, leaving behind fermented wastes. In cases of extreme damage, hives collapse and are turned to an odorous mass of larvae in fermenting hive products. The yeast Kodamaea ohmeri (Etchells & Bell) Yamada et al. (Ascomycota) has been consistently isolated from the fermenting material as well as each life stage of this beetle. Various studies have noted that the small hive beetle is attracted to volatiles from hive products and those of the yeast K. ohmeri, although earlier studies have not used naturally occurring hive products as their source of fermentation. This study investigated changes through time in the attractiveness of natural honeybee hive products to the small hive beetle as the hive products were altered by the action of beetle larvae and fermentation by K. ohmeri. We used gas chromatography-mass spectrometry and choice-test behavioural assays to investigate these changes using products sampled from three apiaries. Attractiveness of the fermenting hive products (‘slime’) increased as fermentation progressed, and volatile profiles became more complex. Fermenting hive products remained extremely attractive for more than 30 days, significantly longer than previous reports. These results have strong implications for the development of an external attractant trap to assist in the management of this invasive pest.

Controlled release of ethylene gas from the ethylene-α-cyclodextrin inclusion complex powder with deliquescent salts

Deliquescent calcium chloride (CaCl2) and magnesium chloride (MgCl2) were investigated for their practical application to release ethylene gas from an ethylene-α-cyclodextrin inclusion complexes (CD IC) powder at relative humidities (RHs) between 11.2 and 93.6 % at 18 °C. The IC powder and deliquescent salts were mixed at a ratio of 1:5, respectively. CaCl2 and MgCl2 started to deliquesce at 32.7 % RH. The IC powder dissolved in the concentrated salt solutions to release ethylene gas. Increasing the RH accelerated the release rate. Maximum release of ethylene gas was achieved after 24 h at 75.5 and 93.6 % RH for both IC powder-deliquescent salts mixture. The deliquescent salts proved to be a simple option for releasing ethylene gas from the IC powder.