Biological Sciences
New gender-bending parasite discovered in shrimps
Mon, 17 Sep 2012 09:59:00 BST
Scientists have discovered a new parasite, previously unknown to science, which may be responsible for turning shrimps and other crustaceans from male to female.
The research, which reverses 40 years of scientific thinking, means scientists can start addressing the problem of gender imbalance in crustaceans caused by feminising parasites.
Marine biologists at the University of Portsmouth have discovered a new species of paramyxean, a type of parasite, which they believe feminises its host. They found that paramyxean almost always exists alongside another well-known parasite known as microsporidians, which scientists previously believed to be the feminising force.
Their research led them to conclude that the existing parasite simply ‘hitchhikes’ a ride with the new parasite which carries out the work of sex reversal
The research is funded by the Natural Environment Research Council and published in the International Journal for Parasitology.
The newly discovered paramyxean parasite is related to a group of organisms known to cause catastrophic sexual dysfunction in molluscs. The issue can be disastrous for commercial mussel and oyster bed operations and can have major consequences further up the food chain. In amphipod crustaceans such as shrimps (Echinogammarus marinus), both parasites infect their hosts by transmitting vertically from ‘mother’ to offspring and converting the host in its early, most vulnerable stages of life. Vertically transmitted parasites depend on the reproductive success of their hosts to survive and by turning them female, all parties have the best chance of survival.
Dr Alex Ford from the University’s Institute of Marine Science (IMS) said that the discovery could re-write the textbooks. He said: “It means that we can start looking at a whole different genus causing the feminisation of crustaceans. And this is vital research because we’re seeing a gender imbalance which is a serious ecological problem affecting species further up the food chain. Marine creatures such as shrimps and molluscs are food for fish and seabirds which mean the consequences could be profound.
Dr Stephen Short from the IMS said that these species are additionally vulnerable because industrial pollutants such as plastics, oils and toxic PCBs in the water makes them less able to fight infection or attack.
“Newborn crustaceans are sexless and are very open to being directed a particular way. What we’re currently seeing is worrying for our marine habitats because the problem is chronic and widespread.”