Open-access Daphnia atlas provides detailed view of sentinel species for environmental research

A unique web-based resource of Daphnia, a sentinel species for environmental pollution, commonly used to help us detect and understand the potential toxic effects of chemicals in the environment, has just been established by Penn State researchers.

Daphnia, also known as the water flea, is a small freshwater crustacean known for its sensitivity to pollution. To date, the impact of chemicals has been measured only at the whole organism level. Being able to measure the toxic effects of chemicals on cells and tissues opens new exciting opportunities to predict the adverse effects of chemicals.

A Penn State team, with collaborators from the University of Birmingham, U.K., and Mount Allison University, Canada, has now created the first reference atlas that enables the analysis of tissue and cell specific effects of chemicals: the Daphnia Histology Reference Atlas (DaHRA).

"This atlas provides the first open-access resource for the Daphnia community," remarked Dr. Khai C. Ang, assistant professor in the Department of Pathology at Penn State College of Medicine and principal investigator and director of this project.

"It provides researchers with a resource to understand the normal microanatomy so that scientists can correctly interpret the impacts of environmental pollutants on the organism as an indicator for ensuring environmental health and sustainability."

The images were made possible by the meticulous cutting, scanning, and labeling work of a team led by first author Dr. Mee Siing Ngu. The atlas includes female and male adult D. magna cut in three anatomical planes, enabling visual recognition of specific organs and developmental stages. DaHRA's user-friendly web-based interface was made possible by the programmer Daniel Vanselow, who also participates in other atlas projects.

"To facilitate user interpretation of the Daphnia's organs and tissues, each tissue plane is color-coded and captured from different angles. Users will be able to identify each tissue, thanks to the careful labeling of each tissue captured by the atlas," said Dr. Ngu, who is also the DaHRA curator. "These tools can also be implemented to atlases of other model organisms."

To make the tool as useful as possible for scientists, educators, and policymakers, the online viewer allows seamless navigation and zooming into high-resolution images, complete with labels that are compliant with standardized anatomical terms. This democratized access not only enhances the understanding of Daphnia microanatomy but also fosters collaboration and knowledge sharing across the scientific community.

The Daphnia atlas project was conceived by physician-scientist Dr. Keith Cheng, distinguished professor of pathology, biochemistry and molecular biology and pharmacology at the College of Medicine. "In human clinical diagnostics, molecular change needs to be correlated with changes in cellular and tissue morphology for validation. However, even recognizing abnormal morphology requires prior knowledge of normal morphology. This principle applies equally to cancer diagnoses as it does to toxicology," said Dr. Cheng.

"The atlas' example of Daphnia histopathology reveals how harmful chemicals affect specific tissues, even before causing developmental failure or death. Combined histopathology with advanced molecular tools would enable precise detection of toxicity, improving chemical risk assessment for better environmental protection and regulation," said Professor Dr. Luisa Orsini, a collaborator from the University of Birmingham, U.K.

The introduction of DaHRA has transformative implications for ecotoxicology and environmental science.

Dr. Ang plans to integrate DaHRA's data with molecular and other toxicological effects with the aim of understanding the adverse effect of chemicals in the environment. Drs. Ang, Ngu and Cheng are also working to apply the tools of the Daphnia atlas to other organisms.

The Daphnia Histology Reference Atlas is an open-access resource available, and the manuscript detailing this significant work is now published in Science of the Total Environment and is accessible to the scientific community, promoting ongoing dialogue and research in ecotoxicology and environmental science.