The heartbeat of daphnia, commonly known as water fleas, can now be used to detect micro-toxicity in water.
The Korea Research Institute of Standards and Science (KRISS) announced Friday that it has developed a toxicity assessment system that automatically measures and analyzes the heart rate of daphnia.
The system can process heart rate data from about 150 daphnia per hour, enabling more sensitive evaluation of low-concentration contaminant toxicity than conventional methods that relied on averaging small numbers of specimens.
Daphnia are widely used in aquatic toxicity assessments because they are easy to raise, show high reproducibility, and have transparent bodies that facilitate long-term observation.
The current international standard toxicity test, "OECD 202," determines swimming impairment by visual inspection, which produces measurement variability depending on the observer's subjectivity. Heart rate measurement has drawn attention as a quantitative indicator to complement this limitation, but the rapid heartbeat of about 6 to 8 times per second has been difficult to measure accurately by eye.
To address this, the KRISS research team developed a system that automatically measures and analyzes daphnia heart rate. The method fixes the daphnia on cotton fabric, captures the heart area through high-speed imaging, and records repeated brightness-change signals to automatically calculate the heart rate. Measurement data is generated in real time within the system, and toxic responses can be confirmed through subsequent analysis.
Using this system, the researchers simultaneously collected and analyzed changes in daphnia heart rate following toxic substance exposure at a scale of about 150 daphnia per hour. This large-scale analysis identifies response distributions across individual specimens, further enhancing analytical precision.
Through data distribution, the system can capture not only subtle differences between individuals but also low-concentration, non-lethal toxicity that was difficult to identify with existing methods. The equipment design is also intuitive and straightforward, allowing flexible application across various research environments and substances, giving it high scalability.
This is expected to help detect early warning signs of environmental hazards and is anticipated to be used in the future risk assessment of chemicals and nanomaterials present in aquatic ecosystems such as rivers and lakes.
The achievement is the result of joint research between KRISS and the KIST Europe Research Institute. The system, developed under KRISS leadership, was installed on-site at KIST Europe, which used it to conduct nanomaterial toxicity assessment experiments and data verification.
"This system is a technology that enhances the precision of aquatic environment toxicity assessment," said Kwon Ik-hwan, senior researcher at the KRISS Nano-Bio Measurement Group. "We will further advance it for application not only in nanomaterial toxicity assessment but also in human-like models such as cardiac organoids."
"The system developed by KRISS has been installed at the on-site laboratory of KIST-Europe and is being used for CHIASMA, a Horizon Europe project," said Lee Tai-gyu, principal researcher. "Through technology transfer with domestic equipment developers, we plan to spread it to cardiac toxicity research teams worldwide."
