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Daphnia Pulex - the common water flea

Daphnia Pulex - the common water flea

This week there has been an important breakthrough in science as the Daphnia Pulex is the first crustacean to have its complete genome sequenced.  Significant, because not only has the research into this water flea produced better understanding about aquatic ecosytems where near lethal toxins, such as Cadmium are often present – but also, more recently, enabled better insight into environmental genomics – the new science of how the environment and genes work together.

Joshua Hamilton, senior scientist at the Marine Biological Laboratory (MBL) likens the behaviour of the creature to a canary in a coal mine, in that its response to freshwater ecosystems and therein toxic pollutants, can warn us of possible adverse conditions in the entire ecosystem.  Daphnia Pulex helps to define regulatory limits, and to monitor industrial and municipal discharges.

Sub-lethal levels of a major environmental contaminant, the metal cadmium, which is highly toxic to aquatic life (and to humans), is one of the most common contaminants found in the U.S. EPA Superfund sites. 

Daphnia and humans have many shared genes, enabling us to research human illnesses

“But with many shared genes between Daphnia and humans, we will now also apply Daphnia as a surrogate model to address issues directly related to human health. This puts us in a position to begin integrating studies of environmental quality with research of human diseases.” Joseph Shaw, co-author of the cadmium study, points out.

Daphnia Pulex, the common water flea, measures just 1 mm but with 31,000 genes in its DNA – more than any other animal – has fascinated and intrigued scientists.  Humans have about 23,000.

Tiny perfect alien

Tiny perfect alien


The animal has unique ways of responding to stress, with some species producing exaggerated tail spines, neck teeth or protective helmets when threatened by predators.

This crustacean has a transparent tiny body, compound eyes (not unlike a fly), limbs that are jointed, and a simple nervous and circulatory system.  Yes, this is a wonder in its own right, but not unusual… 

Sophisticated and strange behaviour

The Daphnia Pulex is able to adapt to extremes in its environment (acidity, dangerous toxins, oxygen concentrations, temperature) and food quality.  And, is able to reproduce both sexually and asexually (like the aphid). 

Small, quiet, humble, unobtrusive…but treasured for its unique genes which teach us how to maintain our aquatic ecosytems, and even help us fight human diseases, due to the many shared genes.  Really no small feat.


Copyright Stephanie Faith 2011


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