Humble water flea boasts more genes than humans

IT may be a simple form of pond life, but in terms of genetic complexity the humble water flea beats humans hands down.

Scientists have learned that the one millimetre- long creature has more genes than another other animal known.

In total, about 31,000 genes are packed into its DNA. In comparison, humans have only about 23,000.

The common water flea, Daphnia pulex, is the first crustacean to have a blueprint made showing the sequence of chemicals that make up genetic code, or genome.

At first glance Daphnia seems ordinary enough, having a transparent body, jointed limbs, compound eyes and a simple nervous and circulatory system.

But its genome is not only unusually large but full of surprises.

“More than one third of Daphnia’s genes are undocumented in any other organism — in other words, they are completely new to science,” said Dr Don Gilbert, one of the researchers from Indiana University at Bloomington in the United States.

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.

The creatures are able to reproduce both sexually and asexually. They thrive in the absence of males by clonal reproduction, until harsh environmental conditions favour the benefits of sex.

A high rate of gene duplication is the main reason why Daphnia has so many genes, say the researchers writing in the journal Science.