Adaptation of life-history traits and trade-offs in marine medaka (Oryzias melastigma) after whole life-cycle exposure to polystyrene microplastics

Microplastics are ubiquitous in marine environments and may cause unexpected ecological effects. This study adopted a whole life-cycle exposure to illuminate the impact of polystyrene microplastics on life-history strategies of marine medaka (Oryzias melastigma), including the hatching of embryos, growth and reproduction of F0 generation, and embryonic and larval development of F1 offspring. Microplastics accumulated on the eggshell and reduced embryonic hatching rate and larval body length and weight. Similarly, 150 days of microplastic exposure decreased body mass and gonadosomatic index of adult fish, but accelerated sexual maturity of female fish, showing a trade-off between growth and reproduction. Microplastic exposure also caused obvious histopathological damages to gonads and decreased egg productions and fertilization rates. Moreover, parental microplastic exposure induced elevated heartbeats, premature hatching, and slow growth in F1 offspring. Antioxidative stress response, sex hormone disruption, and disturbed transcription of steroidogenic genes in the reproductive axis could partially explain the reproduction impairment and transgenerational trade-offs. Furthermore, transcriptome analysis revealed that the steroid hormone biosynthesis and cytochrome P450 pathways in the testes of male fish were significantly affected after 20 mu g/L microplastic exposure. These findings suggest that microplastic pollution may be an emerging threat to the sustainability of marine fish population.

Automated summary

Microplastics have significant impacts on the reproduction and transgenerational trade-offs of marine medaka, affecting hatchability, body weight and length, sexual maturity, gonadal damage, fertilization rate, and more. Parental exposure to microplastics leads to increased heartbeats, premature hatching, and slow growth in offspring, possibly due to oxidative stress, hormonal disruption, and altered transcription of steroidogenic genes. Furthermore, transcriptome analysis shows considerable effects on steroid hormone biosynthesis and cytochrome P450 pathways in male fish testes after exposure to 20 μg/L microplastics, indicating a potential threat to the sustainability of marine fish populations.