Anoxia From Water Pollution Alters Gender Ratios In Fish - Reuters

[hatrack]

HONG KONG — A lack of oxygen in highly polluted waters can sharply alter the sex ratio among fish, resulting in far more males than females, a study has found, which could result in the extinction of a species.

In a three-and-a-half year study, researchers at the City University of Hong Kong used more than 10,000 embryos of zebra fish -- a small, hardy freshwater species -- and raised half of them in water that was depleted of oxygen. The other half was raised in normal, oxygenated water.

Hypoxia, or oxygen depletion, occurs when there are less than two parts of oxygen for every million parts of water. It occurs naturally in places where salt and fresh waters meet, though it is now also caused by pollution in many parts of the world.

"We found that whereas 61 percent of zebra fish spawned into males under regular oxygen conditions, under hypoxic conditions, the number of males increased to 75 percent," said Rudolf Wu, chair of biology at the university. This is the first study ever to suggest that hypoxia can affect sex development, differentiation and ratio in any animal species. It was published in the May issue of the journal Environmental Science & Technology.

EDIT

http://www.enn.com/today.html?id=10626

[valerief]

1. There may be a lack of oxygen in males

But no lack of hot air.