Exposure to ultraviolet radiation induces escape hatching of cisco (Coregonus artedi) embryos
Cisco (Coregonus artedi) embryos typically incubate in dark, ice‑covered northern lakes, but climate‑driven reductions in ice and clearer water may increase UV‑B exposure. Experiments exposing eyed embryos to artificial UV‑B showed strong evidence for UV‑induced escape hatching: embryos hatched roughly 30 days earlier and in a more synchronized pulse, independent of temperature. However, UV‑B also produced larvae with irregular pigmentation and ~20% lower heart rates, indicating reduced fitness. These results expand the escape‑hatching framework and suggest that increased UV‑B could intensify recruitment bottlenecks for coregonines by reducing post‑hatch survival. Understanding these responses is essential for predicting resilience under changing winter conditions.
Subject Tags
- Lakes
- Life Sciences
- Wildlife
Abstract
- Cisco (Otoonapii in Ojibwe; Coregonus artedi Lesueur, 1818), is a widely distributed stenothermic freshwater fish whose embryos typically incubate under ice and in the dark. We used cisco as a model organism for testing the potential of UV-induced escape hatching behaviour. Owing to reduced ice cover and increased water transparency in north temperate lakes, these experiments provide insights into the resilience of coregonine embryos if exposed to ultraviolet radiation (UV-B; 280–320 nm).
- Eyed cisco embryos were exposed to artificially sourced UV-B through a series of experiments that measured the hatching rate and fitness (heart rate and pigmentation pattern) two days after hatching and under cold [6.6°C] and warm [8.6°C] conditions.
- These experiments supported an extension of the escape hatching behaviour hypothesis, whereby UV-B exposure induced earlier (ca 30 days) and more punctuated hatching of cisco embryos, independent of an increase in water temperature. UV-B exposure produced more larvae with irregular pigmentation patterns and reduced heart rates (by about 20%)—both of which could be indicative of reduced fitness.
- UV-induced escape hatching adusts the fundamental framework in which we characterise fish embryo resilience to increased UV-B exposure and the potential consequences of reduced ice cover. Earlier hatching from UV-B exposure could increase the recruitment bottleneck of these fish by reducing survivorship of the post-hatched larvae.
Citation
Berry, N. L., Bunnell, D. B., Overholt, E. P., Schumacher, J. A., Almeda, A. Z., Schoenebeck, C. W., ... & Williamson, C. E. (2025). Exposure to Ultraviolet Radiation Induces Escape Hatching of Cisco (Coregonus artedi) Embryos. Freshwater Biology, 70(5), e70031. https://doi.org/10.1111/fwb.70031
TNC Authors
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Andrew Tucker
Conservation Scientist, Wisconsin
The Nature Conservancy
Email: atucker@tnc.org