Dating back to 255 Mya, a diversity of vertebrate species have excavated mysterious, deep helical burrows called Daimonelix (devil's corkscrews). The possible functions of such structures are manifold, but their paucity in extant animals has frustrated their adaptive explanation. We recently discovered the first helical reptile burrows, created by the monitor lizard Varanus panoptes. The plugged burrows terminated in nest chambers that were the deepest known of any vertebrate, and by far the deepest of any reptile (mean = 2.3 m, range = 1.0-3.6 m, N = 52). A significant positive relationship between soil moisture and nest depth persisted at depths > 1 m, suggesting that deep nesting in V. panoptes may be an evolutionary response to egg desiccation during the long (approximately 8 months) dry season incubation period. Alternatively, lizards may avoid shallower nesting because even slight daily temperature fluctuations are detrimental to developing embryos; our data show that this species may have the most stable incubation environment of any reptile and possibly any ectotherm. Soilfilled burrows do not support the hypothesis generated for Daimonelix that the helix would provide more consistent temperature and humidity as a result of limited air circulation in dry palaeoclimates. We suggest that Daimonelix were used mainly for nesting or rearing young, because helical burrows of extant vertebrates are generally associated with a nest. The extraordinary nesting in this lizard reflects a system in which adaptive hypotheses for the function of fossil helical burrows can be readily tested.

Emerging infectious diseases are one of the greatest threats to global biodiversity. Chytridiomycosis in amphibians is perhaps the most extreme example of this phenomenon known to science. Translocations are increasingly used to fight disease‐induced extinctions. However, many programmes fail because disease is still present or subsequently establishes in the translocation environment. There is a need for studies in real‐world scenarios to test whether environmental manipulation could improve survival in populations by generating unfavourable environmental conditions for pathogens. Reintroductions of amphibians impacted by chytridiomycosis into environments where the disease persists provide a scenario where this paradigm can be tested. We tested the hypothesis that manipulating environmental salinity in outdoor mesocosms under near‐identical environmental conditions, present in a nearby translocation programme for an endangered amphibian, would improve survival and determine the mechanisms involved. One hundred and sixty infected and 288 uninfected, captive‐bred, juvenile frogs were released into 16 outdoor mesocosms in which salinity was controlled (high‐ or low‐salinity treatment). The experiment was run for 25 weeks from the mid‐austral winter to the mid‐austral summer of 2013 in a temperate coastal environment, Australia. Increasing salinity from c. 0.5 ppt to 3.5–4.5 ppt reduced pathogen transmission between infected and uninfected animals, resulting in significantly reduced mortality in elevated salt mesocosms (0.13, high‐salt vs. 0.23, low‐salt survival at 23 weeks). Increasing water temperature associated with season (from mean 13 to 25°C) eventually cleared all surviving animals of the pathogen. Synthesis and applications. We identified a mechanism by which environmental salinity can protect amphibian hosts from chytridomycosis by reducing disease transmission rates. We conclude that manipulating environmental salinity in landscapes where chytrid‐affected amphibians are currently translocated could improve the probability of population persistence for hundreds of species. More broadly, we provide support for the paradigm that environmental manipulation can be used to mitigate the impact of emerging infectious diseases.

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The predators of first- and second-instar larvae of Aedes stimulans and A. trichurus in temporary woodland pools near Belleville, Ontario, were determined mainly by use of mosquito larvae tagged with radioactive phosphorus, but in part from the presence of aedine remains found in the digestive tracts of dissected beetles. Of 428 pond animals collected from the test pools 122 were found to be radioactive above background. Among the 17 species of aquatic insects and other animals that fed on mosquito larvae, 8 species of Dytiscidae, 1 of Hydrophilidae, 1 of Limnephilidae, and 1 pond snail are regarded as important predators. Three additional species of water beetles were identified as predators from aedine remains in their digestive tracts. The abundance of the predators, and the times of occurrence of six species in relation to mosquito development, are discussed.

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