Synergistic effects of the invasive Chinese tallow (Triadica sebifera) and climate change on aquatic amphibian survival

Microplastics as an emerging threat to amphibians: Current status and future perspectives

Given their pervasiveness in the environment, particularly in aquatic ecosystems, plastics are posing a growing concern worldwide. Many vertebrates and invertebrates in marine, freshwater, and terrestrial ecosystems exhibit microplastic (MP) uptake and accumulation. Some studies have indicated the fatal impacts of MPs on animals and their possible transfer through food chains. Thus, it is crucial to study MP pollution and its impacts on environment-sensitive and globally threatened animal groups, such as amphibians, which also play an important role in the energy transfer between ecosystems. Unfortunately, research in this field is lacking and sources of organized information are also scarce. Hence, we systematically reviewed published literature on MPs in amphibians to fill the existing knowledge gap. Our review revealed that most of the previous studies have focused on MP bioaccumulation in amphibians, whereas, only a few research highlighted its impacts. We found that more than 80% of the studied species exhibited MP accumulation. MPs were reported to persist in different organs for a long time and get transferred to other trophic levels. They can also exhibit cytotoxic and mutagenic effects and may have fatal impacts. Moreover, they can increase the disease susceptibility of amphibians. Our study concludes the MPs as a potential threat to amphibians and urges increasing the scope and frequency of research on MP pollution and its impacts on this vulnerable animal group. We also provide a generalized method for studying MPs in amphibians with future perspectives and research directions. Our study is significant for extending the knowledge of MPs and their impacts on amphibians and guiding prospective research.

Increased Temperature Influenced Growth and Development of Lithobates pipiens Tadpoles Exposed to Leachates of the Invasive Plant European Buckthorn (Rhamnus cathartica) and a Triclopyr Herbicide

Multiple factors including habitat loss, pollutants, invasive species, and disease have contributed to the global decline of amphibians, and further declines can be expected as a result of climate change. Warming temperatures may allow for range expansion of invasive plants, and because herbicides are the primary method to control invasive plants, chemical use may increase. A laboratory experiment was performed to examine the individual and combined effects of leachates from the invasive plant European buckthorn (Rhamnus cathartica, L.) and a triclopyr herbicide (Renovate® 3; 0.21 mg/L), which is commonly used to manage R. cathartica, on northern leopard frog (Lithobates pipiens, Schreber) tadpoles at 2 temperature regimes (20 and 25 °C). We measured tadpole growth weekly and body and intestine morphology at the conclusion of the experiment after 8 wk. In the presence of R. cathartica leachates, tadpole growth increased at 25 °C, but only during the first 3 to 4 wk of the experiment. From week 5 until the end of the experiment, tadpoles were significantly smaller at 25 °C compared with 20 °C, but had more developed limb buds at the end of the experiment (except in the triclopyr treatment). Triclopyr had minimal effects on tadpole growth at the low dose used in this study. These results encourage further examination of potential effects of global climate changes in combination with other environmental factors that may impact amphibian populations. Environ Toxicol Chem 2021;40:2547-2558. © 2021 SETAC.

Reproductive endpoints of Rhinella arenarum (Anura, Bufonidae): Populations that persist in agroecosystems and their use for the environmental health assessment

Degradation of the environment by agriculture affects the persistence and health of the amphibian populations. Characteristics related to reproduction of anuran can be used to evaluate the status of populations and as endpoints in environmental health assessment. In this in situ study the aspects related to the amplexus and ovipositions of the bioindicator species Rhinella arenarum that inhabits agroecosystems were analyzed. The hypothesis of this study is that perturbations of agroecosystems have a negative impact on the size of reproductive adults, on the size of ovipositions and eggs, and on the survival of eggs and embryos. Study area is located in the rural landscape of central Argentina. Four sampling sites were selected: C1, C2 and C3 are ponds on agroecosystems; and SM is a reference site that is not affected by agriculture or livestock. Abundance of amplexus pairs, oviposition and tadpoles per site was recorded. Individuals´ snout-vent length (SVL) in amplexus was measured. The fecundity was calculated like number of eggs per oviposition. The eggs' Gosner stage, the diameter eggs and the frequency of dead and abnormal eggs were recorded by oviposition. Killing-power between egg-embryo and egg-tadpole was calculated. The higher phosphate concentration was detected in all agroecosystems and nitrate was detected in C1 and C2. Conductivity, salinity and SDT were higher in C1 site Male SVL from the SM site was lower than the other sites while the largest SVL was of female from the C3 site. The higher frequencies of sprouted eggs and of dead eggs were recorded in the C2 site. Egg diameter was associated with SM and correlated negatively to SVL of the male and female. No correlation between female SVL and oviposition size was recorded. Killing-power in the passage from egg to tadpole classes was higher in the three agroecosystems. The hypothesis of this study was corroborated in part. Reproductive adults in agroecosystems did not have smaller body size. However, in the agroecosystem ponds, the eggs with smaller diameter were registered, the oviposition had higher frequency of abnormal eggs and the higher mortality was registered. This confirms the high sensitivity of the early stages to environmental disturbances and sustains their use as endpoints for the environmental health assessment.