About Daphnia pulex

Daphnia pulex, the common water flea, is a microcrustacean arthropod (typically 0.2-3.0 mm long) found ubiquitously in freshwater around the globe, predominately in small ponds and ephemeral pools. D. pulex live for around 10-30 days, but can live up to 100 days in the absence of predation. Their anatomy is easily studied, due to the see-through carapce which reveals the internal organs at work.

Daphnia pulex is sensitive to environmental changes and exhibits context-dependent responses (e.g. switching from clonal to sexual reproduction, or rapidly changing haemoglobin levels) that make it a sensible agent to assess the ecological impact of environmental fluctuations. Predation can induce a range of morphological changes in D. pulex. In response to kairomones (chemicals released by predatory insect larvae), D. pulex develop small protusions (neckteeth) that act as a defence mechanism. It can also change size to avoid either detection by larger vertebrate predators, or consumption by smaller invertebrate predators.

In addition to its usefulness in a variety of research areas (including ecology, toxicology, and physiology), in evolutionary terms Daphnia pulex is important as a representative of the sister group to the insects, and can highlight genes present in the pancrustacean common ancestor.

Picture credit: Dr Paul D.N. Hebert (University of Guelph)

Taxonomy ID 6669

Data source Joint Genome Institute

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