Skin Bacterial and Fungal Microbiome Responses to Diet Supplementation and Rewilding in the Critically Endangered Southern Corroboree Frog.

The composition and dynamics of the skin bacterial and fungal microbiome is thought to influence host-pathogen defence. This microbial community is shaped by host captivity, diet, and microbial interactions between bacterial and fungal components. However, there remains little understanding of how specific micronutrients influence bacterial and fungal microbiome composition and their inter-domain interactions during rewilding of captive-bred animals.

Dietary carotenoid supplementation has long-term and community-wide effects on the amphibian skin microbiome.

The amphibian skin microbiome plays a crucial role in host immunity and pathogen defence, yet we know little about the environmental drivers of skin microbial variation across host individuals. Inter-individual variation in the availability of micro-nutrients such as dietary carotenoids, which are involved in amphibian immunity, may be one factor that influences skin microbial assembly across different life history stages. We compared the effect of four carotenoid supplementation regimes during different life stages on the adult skin microbiome using a captive population of the critically endangered southern corroboree frog, Pseudophryne corroboree.

Application of Reproductive Technologies to the Critically Endangered Baw Baw Frog, .

Reproductive technologies (RTs) can assist integrated conservation breeding programs to attain propagation targets and manage genetic diversity more effectively. While the application of RTs to enhance the conservation management of threatened amphibians has lagged behind that of other taxonomic groups, a recent surge in research is narrowing the divide. The present study reports on the first application of RTs (hormone-induced spawning, hormone-induced sperm-release, and sperm cryopreservation) to the critically endangered Baw Baw frog, .

The Increasing Role of Short-Term Sperm Storage and Cryopreservation in Conserving Threatened Amphibian Species.

Multidisciplinary approaches to conserve threatened species are required to curb biodiversity loss. Globally, amphibians are facing the most severe declines of any vertebrate class. In response, conservation breeding programs have been established in a growing number of amphibian species as a safeguard against further extinction.

A test for plasticity in sperm motility activation in response to osmotic environment in an anuran amphibian.

Evolutionary theory predicts that selection will favor phenotypic plasticity in sperm traits that maximize fertilization success in dynamic fertilization environments. In species with external fertilization, osmolality of the fertilization medium is known to play a critical role in activating sperm motility, but evidence for osmotic-induced sperm plasticity is limited to euryhaline fish and marine invertebrates. Whether this capacity extends to freshwater taxa remains unknown.

Does dietary β-carotene influence ontogenetic colour change in the southern corroboree frog?

Ontogenetic colour change occurs in a diversity of vertebrate taxa and may be closely linked to dietary changes throughout development. In various species, red, orange and yellow colouration can be enhanced by the consumption of carotenoids. However, a paucity of long-term dietary manipulation studies means that little is known of the role of individual carotenoid compounds in ontogenetic colour change.

Hormone-induced ovulation and artificial fertilisation in four terrestrial-breeding anurans.

The development and application of reproductive technologies has great potential to enhance the conservation management of threatened amphibians globally. The present study quantified the efficacy of protocols previously developed for Pseudophryne guentheri for hormonally inducing egg release and artificial fertilisation in three additional terrestrial-breeding species of Australian ground frog; namely Pseudophryne bibronii , Pseudophryne coriacea and Heleioporus eyrei . Females of each species were administered a priming dose of 0.

Love at first flight: wing interference patterns are species-specific and sexually dimorphic in blowflies (Diptera: Calliphoridae).

Wing interference patterns (WIPs) are stable structural colours displayed on insect wings which are only visible at specific viewing geometries and against certain backgrounds. These patterns are widespread among flies and wasps, and growing evidence suggests that they may function as species- and sex-specific mating cues in a range of taxa. As such, it is expected that WIPs should differ between species and show clear sexual dimorphisms.

Evidence that genetic compatibility underpins female mate choice in a monandrous amphibian.

Mate choice for genetic benefits remains controversial, largely because few studies have estimated the relative contributions of additive and non-additive sources of genetic variation to offspring fitness. Moreover, there remains a deficit of these estimates for species where female-mate preferences have been quantified in the wild, especially species characterized by monandry or monogamy. Here, we use artificial fertilization techniques combined with a cross-classified breeding design to simultaneously test for "good genes" and "compatible genes" benefits of mate choice in the monandrous red backed toadlet (Pseudophryne coriacea).

The effect of injection and topical application of hCG and GnRH agonist to induce sperm-release in the roseate frog, .

Reproductive technologies may assist amphibian conservation breeding programs (CBPs) to achieve propagation targets and genetic management goals. However, a trial-and-error approach to protocol refinement has led to few amphibian CBPs routinely employing reproductive technologies with predictable outcomes. Additionally, while injections can be safely administered to amphibians, perceived animal welfare risks, such as injury and disease transmission, warrant the development of alternative hormone administration protocols.

The evolution of sexually dimorphic cuticular hydrocarbons in blowflies (Diptera: Calliphoridae).

Cuticular hydrocarbons (CHCs) are organic compounds found on the cuticles of all insects which can act as close-contact pheromones, while also providing a hydrophobic barrier to water loss. Given their widespread importance in sexual behaviour and survival, CHCs have likely contributed heavily to the adaptation and speciation of insects. Despite this, the patterns and mechanisms of their diversification have been studied in very few taxa.

Major Transitions in Cuticular Hydrocarbon Expression Coincide with Sexual Maturity in a Blowfly (Diptera: Calliphoridae).

In many animals, there is a prolonged pre-reproductive period prior to sexual maturity. To avoid premature mating attempts, it is common for phenotypic changes to occur during this period that signal the onset of reproductive viability. Among the insects, pre-reproductive phases can last for up to 50% of the adult lifespan, but little is known about the accompanying phenotypic changes that signal sexual maturity.

Warmer temperature and provision of natural substrate enable earlier metamorphosis in the critically endangered Baw Baw frog.

Temperature and food availability are known to independently trigger phenotypic change in ectotherms, but the interactive effects between these factors have rarely been considered. This study investigates the independent and interactive effects of water temperature and food availability on larval growth and development of the critically endangered Baw Baw frog, . Larvae were reared at low (12°C) or high (17°C) water temperature in the absence or presence of substrate that controlled food availability, and body size and time to metamorphosis were quantified.

Genetic benefits of extreme sequential polyandry in a terrestrial-breeding frog.

Sequential polyandry may evolve as an insurance mechanism to reduce the risk of females choosing mates who are genetically inferior (intrinsic male quality hypothesis) or genetically incompatible (genetic incompatibility hypothesis). The prevalence of such indirect benefits remains controversial, however, because studies estimating the contributions of additive and nonadditive sources of genetic variation to offspring fitness have been limited to a small number of taxonomic groups. Here, we used artificial fertilization techniques combined with a crossclassified breeding design (North Carolina Type II) to simultaneously test the "good genes hypothesis" and the "genetic incompatibility hypothesis" in the brown toadlet (Pseudophryne bibronii); a terrestrial-breeding species with extreme sequential polyandry.

Effect of long-term dietary beta-carotene supplementation on sperm concentration and motility in an endangered amphibian.

Dietary carotenoids have a high antioxidant capacity, so it has been hypothesised that carotenoid supplimentation will improve sperm production and quality by protecting sperm from oxidative damage. The effects of carotenoids on sperm have only been assessed in three vertebrate species, and evidence for improved sperm concentration and motility remains equivocal. One reason for this might be that in most studies there has not been an assessment of the effects of single carotenoid compounds over a range of doses.

Effect of carotenoid class and dose on the larval growth and development of the critically endangered southern corroboree frog.

Dietary carotenoids are expected to improve vertebrate growth and development, though evidence for beneficial effects remains limited. One reason for this might be that few studies have directly compared the effects of carotenoids from different classes (carotenes versus xanthophylls) at more than one dose. Here, we tested the effect of two doses of dietary β-carotene and lutein (representing two different carotenoid classes) on the growth and development of larval southern corroboree frogs ().

Hormone-induced sperm-release in the critically endangered Booroolong frog (): effects of gonadotropin-releasing hormone and human chorionic gonadotropin.

Research into the development of reproductive technologies for amphibians has increased in recent years due to the rapid decline of amphibian species globally. Reproductive technologies have great potential to overcome captive breeding failure and improve the propagation and genetic management of threatened species. However, the incorporation of these technologies into conservation breeding programs has been protracted, primarily as a result of trial-and-error approaches to the refinement of hormone therapies.

The Role of Reproductive Technologies in Amphibian Conservation Breeding Programs.

Anthropogenic environmental change has led to unprecedented rates of species extinction, presenting a major threat to global biodiversity. Among vertebrates, amphibians have been most severely impacted, with an estimated 41% of species now threatened with extinction. In response to this biodiversity crisis, a moral and ethical obligation exists to implement proactive interventionist conservation actions to assist species recovery and decelerate declines.

Dose and life stage-dependent effects of dietary beta-carotene supplementation on the growth and development of the Booroolong frog.

Carotenoids are known for their antioxidant capacity and are considered to play an important role in vertebrate growth and development. However, evidence for their beneficial effects remains limited, possibly because very few studies have tested for dose effects across different life stages. The present study investigated the effect of various doses of dietary beta-carotene supplements on the growth and development of larval and post-metamorphic Booroolong frogs ().

Effect of captivity on morphology: negligible changes in external morphology mask significant changes in internal morphology.

Captive breeding programmes are increasingly relied upon for threatened species management. Changes in morphology can occur in captivity, often with unknown consequences for reintroductions. Few studies have examined the morphological changes that occur in captive animals compared with wild animals.

The unexpected genetic mating system of the red-backed toadlet (Pseudophryne coriacea): A species with prolonged terrestrial breeding and cryptic reproductive behaviour.

Molecular technologies have revolutionized our classification of animal mating systems, yet we still know very little about the genetic mating systems of many vertebrate groups. It is widely believed that anuran amphibians have the highest reproductive diversity of all vertebrates, yet genetic mating systems have been studied in <1% of all described species. Here, we use single nucleotide polymorphisms to quantify the genetic mating system of the terrestrial breeding red-backed toadlet Pseudophryne coriacea.

Hormone-induced spawning of the critically endangered northern corroboree frog Pseudophryne pengilleyi.

Fundamental knowledge of the optimal hormone concentrations required to stimulate amplexus and spawning in breeding pairs of amphibians is currently lacking, hindering our understanding of the proximate mechanisms underpinning mating behaviour. The present study investigated the effects of: (1) the dose of a gonadotropin-releasing hormone analogue (GnRH-a) administered; (2) male-female hormone administration interval; and (3) topical application of GnRH-a, on spawning success in the northern corroboree frog. Administration of GnRH-a at doses of 0.

Body Odor and Sex: Do Cuticular Hydrocarbons Facilitate Sexual Attraction in the Small Hairy Maggot Blowfly?

Cuticular hydrocarbons (CHCs) play an important role as contact pheromones in insects, particularly in flies. However, for many fly taxa our understanding of the importance of CHCs in sexual communication is limited. Within the family Calliphoridae (blowflies), sex-specific differences in CHCs have been reported for several species, but there is no evidence that CHCs facilitate sexual behavior.