Yolk contributes steroid to the multidimensional endocrine environment of embryos of Niveoscincus metallicus, a viviparous skink with a moderately complex placenta

Is plastic ingestion in birds as toxic as we think? Insights from a plastic feeding experiment

Plastic pollution is a modern tragedy of the commons, with hundreds of species affected by society's waste. Birds in particular mistake plastic for prey, and millions of wild birds carry small plastic loads in their stomach and are exposed to potential toxicological effects. It is currently unknown how severely the toxicological and endocrine disrupting chemicals in plastic affect avian development, reproduction and endocrine function. To address this question, we conducted multi-generational plastic feeding experiments to test the toxicological consequences of plastic ingestion at environmentally relevant loads in Japanese quail, Coturnix japonica, investigating parental and two filial generations. Contrary to expectations, we found no evidence of lasting toxicological effects on mortality, adult body weight, organ histology, hormone levels, fertility, hatch rates and eggshell strength in birds experimentally fed plastic. However, we found plastic ingestion causes higher frequencies of male reproductive cysts and minor delays in chick growth and sexual maturity, though without affecting ultimate survival or reproductive output. We report that although plastic ingestion causes detectable endocrine effects in our model species, our lack of finding mortality, morbidity and adverse reproductive outcomes may challenge the common hypothesis of severe toxicological harm and population-level effects when environmentally relevant loads of plastic are ingested.

Variations upon a theme: Australian lizards provide insights into the endocrine control of vertebrate reproductive cycles

Australian lizards exhibit a broad array of different reproductive strategies and provide an extraordinary diversity and range of models with which to address fundamental problems in reproductive biology. Studies on lizards have frequently led to new insights into hormonal regulatory pathways or mechanisms of control, but we have detailed knowledge of the reproductive cycle in only a small percentage of known species. This review provides an overview and synthesis of current knowledge of the hormonal control of reproductive cycles in Australian lizards. Agamid lizards have provided useful models with which to test hypotheses about the hormonal regulation of the expression of reproductive behaviors, while research on viviparous skinks is providing insights into the evolution of the endocrine control of gestation. However, in order to better understand the potential risks that environmental factors such as climate change and endocrine disrupting chemicals pose to our fauna, better knowledge is required of the fundamental characteristics of the reproductive cycle in a broader range of lizard species.