Impact of Microplastics on the Feeding Behavior and Reproductive Physiology of Zebrafish (Danio rerio) Across Developmental Stages

Project Abstract

Exposure to microplastics (MPs) at environmentally relevant concentrations can alter feeding strategies and disrupt reproductive physiology in zebrafish (Danio rerio), with effects that vary across ontogenetic stages. This study investigates how polystyrene MPs (1–5 ?m and 10–50 ?m) and weathered MPs influence feeding rate, prey selectivity, gut morphology, energy balance, gonadal development, and secondary sexual characteristics across larval, juvenile, and adult stages over a 90-day exposure period. Behavioral assays quantified bite rate, foraging efficiency, and social feeding dynamics in controlled tank ecosystems, while imaging-based analyses assessed changes in gut length, villus structure, and lipid storage. Reproductive endpoints included gonadosomatic index, oocyte maturation stages in females, spermatogenic progression in males, and fecundity in breeding assays. Concurrently, transcriptomic profiling of key metabolic and endocrine pathways (insulin-like growth factors, thyroid hormone axis, steroidogenesis) complemented targeted qPCR analyses of genes regulating appetite (neuropeptide Y, leptin), stress response (HSP70, cortisol receptors), and reproductive function (vasa, aromatase, follistatin). Results indicate a dose- and size-dependent attenuation of feeding efficiency, with smaller MPs strongly impairing prey capture and increasing gastric retention times, particularly in larvae, leading to reduced growth trajectories. MPs induced stage-specific metabolic shifts, including elevated lipid deposition in hepatocytes and altered carbohydrate utilization, consistent with endocrine disruption signals. Reproductive analyses revealed delayed gametogenesis, reduced fecundity, and altered sex steroid profiles, more pronounced in adults exposed to smaller MPs and aged cohorts. At the molecular level, upregulation of stress-responsive genes and downregulation of appetite and reproductive regulators were observed, aligning with observed phenotypic changes. Weathered MPs elicited more pronounced adverse outcomes than pristine particles, likely due to surface aging and increased adsorption of environmental contaminants, which intensified oxidative stress and endocrine disruption. Epigenetic assessments suggested differential DNA methylation patterns in promoter regions of key metabolic and reproductive genes, potentially explaining persistent effects across developmental stages. Integrative data modeling linked MP exposure to cascading effects impaired feeding reduces energy availability, constraining growth and delaying maturation, while endocrine disruption perturbs gametogenesis and fecundity, collectively diminishing population-level fitness. The study provides mechanistic insight into how MPs of varying sizes interact with developmental physiology to alter behavior and reproduction in zebrafish, highlighting the heightened vulnerability of early life stages and the synergistic impact of particle weathering. These findings underscore the ecological and evolutionary implications of MP pollution for aquatic vertebrates, informing risk assessment and mitigation strategies aimed at preserving reproductive viability and population resilience in MP-contaminated habitats.

Project Overview

What This Project Is About

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A straightforward study that looks at how tiny plastic particles in the water affect how zebrafish eat and how their bodies reproduce, and how these effects change as the fish grow from larvae to adults.

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The Problem It Addresses

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Microplastics are widespread in aquatic environments. We don’t fully understand how they change feeding behavior or reproductive health in zebrafish across different life stages, which could affect fish populations and ecosystem health.

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Objectives of the Project

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1. Describe how microplastics are present in controlled water conditions.
2. Observe changes in feeding rate and food preference with increasing microplastic exposure.
3. Assess reproductive parameters such as spawning frequency, egg quality, and fertilization rate.
4. Compare effects between larval, juvenile, and adult zebrafish.
5. Identify potential thresholds where effects become noticeable.

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What You Will Do Step by Step

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1. Literature review to understand current findings and gaps.
2. Set up zebrafish tanks with graded microplastic concentrations.
3. Expose fish at different developmental stages and monitor feeding behavior.
4. Pair fish to study reproduction and collect data on spawning and egg quality.
5. Measure physiological indicators (growth, stress markers) as needed.
6. Analyze data using basic stats to find trends and differences between groups.
7. Interpret how results relate to environmental relevance.

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Expected Outcome

Clear understanding of how microplastics affect feeding and reproduction in zebrafish at different life stages, with practical insights for environmental risk assessment and potential guidance for reducing microplastic exposure in aquatic systems.