Heatwaves during embryonic development reveal duration-dependent effects in zebrafish

Area of Science:

• Environmental Science
• Developmental Biology
• Climate Change Research

Background:

• Climate change is increasing heatwave frequency and intensity.
• Ectotherms, particularly during embryonic development, are vulnerable to heat stress.
• The impact of short, ecologically relevant heat stress on embryonic development requires further investigation.

Purpose of the Study:

• To investigate the effects of short-term heat stress during embryonic development in zebrafish (Danio rerio).
• To evaluate the consequences of simulated heatwaves of varying durations and frequencies on zebrafish survival, development, and behavior.
• To determine if embryonic heat stress influences larval thermotolerance.

Main Methods:

• Exposed 1753 zebrafish embryos to simulated heatwaves (35°C for 6, 24, or 48 hours, once or twice).
• Assessed pre- and post-natal survival, hatching time, larval body size, and locomotor activity.
• Evaluated larval activity at both control and heat-stress temperatures.

Main Results:

• High temperatures (35°C) significantly increased pre-natal mortality.
• Heatwave duration influenced outcomes: 48-hour heatwaves accelerated development but yielded smaller larvae with increased swimming under heat.
• Shorter heatwaves (24 hours or two 6-hour events) showed no significant effects.

Conclusions:

• Zebrafish embryos are highly sensitive to brief heat stress events during development.
• The duration of heatwave exposure critically determines the severity and type of developmental and behavioral responses.
• Findings provide insights into species' responses to climate change and the vulnerability of early life stages.