Ruthsatz K et al. (2023), Life in plastic, it's not fantastic: Sublethal ...

XB-ART-59800

Sci Total Environ 2023 Aug 10;885:163779. doi: 10.1016/j.scitotenv.2023.163779.

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Life in plastic, it's not fantastic: Sublethal effects of polyethylene microplastics ingestion throughout amphibian metamorphosis.

Ruthsatz K , Schwarz A , Gomez-Mestre I , Meyer R , Domscheit M , Bartels F , Schaeffer SM , Engelkes K .

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Microplastics (MP) are an abundant, long-lasting, and widespread type of environmental pollution that is of increasing concern as it might pose a serious threat to ecosystems and species. However, these threats are still largely unknown for amphibians. Here, we used the African clawed frog (Xenopus laevis) as a model species to investigate whether polyethylene MP ingestion affects amphibian growth and development and leads to metabolic changes across two consecutive life stages (larvae and juveniles). Furthermore, we examined whether MP effects were more pronounced at higher rearing temperatures. Larval growth, development, and body condition were recorded, and standard metabolic rate (SMR) and levels of stress hormone (corticosterone, CORT) were measured. We determined variation in size, morphology, and hepatosomatic index in juveniles to identify any potential consequences of MP ingestion across metamorphosis. In both life stages, MP accumulation in the body was assessed. MP ingestion was found to result in sublethal effects on larval growth, development, and metabolism, to lead to allometric carry-over effects on juvenile morphology, and to accumulate in the specimens at both life stages. In larvae, SMR and developmental rate increased in response to MP ingestion; there additionally was a significant interaction of MP ingestion and temperature on development. CORT levels were higher in larvae that ingested MP, except at higher temperature. In juveniles, body was wider, and extremities were longer in animals exposed to MP during the larval stage; a high rearing temperature in combination with MP ingestion counteracted this effect. Our results provide first insights into the effects of MP on amphibians throughout metamorphosis and demonstrate that juvenile amphibians may act as a pathway for MP from freshwater to terrestrial environments. To allow for generalizations across amphibian species, future experiments need to consider the field prevalence and abundance of different MP in amphibians at various life stages.

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Species referenced: Xenopus laevis
GO keywords: larval development [+]

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	Graphical abstract
	Fig. 1. Effects of MP ingestion during development on A snout-vent length (mm), B growth rate (mg × d−1), C body mass (mg), D body condition (scaled mass index, SMI), E corticosterone level (pg × mg−1), and F standard metabolic rate (SMR, mL O2 × h−1 × g−1), in Xenopus laevis larvae at developmental stage NF57. Box = 1. And 3. Quartiles. Whiskers = 1.5-fold interquartile range. Dots = outliers, minimum, and maximum values. Error bar = median.
	Fig. 2. Effects of MP ingestion during development on A relative forelimb length, B tibiofibula:femur ratio, C relative hindlimb length, and D relative body width in juveniles (i.e., ten days after completing metamorphosis at NF66) of Xenopus laevis. Box = 1. and 3. quartiles. Whiskers = 1.5-fold interquartile range. Dots = outliers, minimum, and maximum values. Error bar = median.
	Fig. 3. Mean number of MP particles × g−1 per treatment in late larvae (i.e., developmental stage NF57,) and in juveniles (i.e., ten days after completing metamorphosis at NF66) in Xenopus laevis. One larva and four juveniles of each aquarium were randomly selected and analyzed, respectively. The A larvae (N = 18) and half of the B juveniles (N = 36) were processed and analyzed in total, whereas in the second half of the juveniles (N = 36) the guts were dissected. Both C the guts and D the body remnants after gut dissection were analyzed individually. Light microscopic pictures of E the MP treatment and F the control group at 400× magnification (Axio Imager.M2, Zeiss, Germany). Width of white rectangle: 100 μm. White arrows: MP particles.