SCIENTISTS say infertility problems for thousands of childless couples could be solved by a humble sea creature.

The Sea Squirt - a slug-like form of marine life usually found clinging to mooring ropes - reproduces in a similar way to humans.

It has enabled experts at Newcastle and Durham Universities to use the eggs and sperm of the tiny creatures in experiments, avoiding the controversial use of human embryos.

Before it was hailed as a possible answer to human infertility, the Squirt was best known for eating its own brain. It only uses it to find a suitable rock or rope to rest on. Once firmly attached, it then digests its cerebral matter, having no further use for it.

Now Dr Alex McDougall and Dr Keith Jones, of Newcastle University, and Dr Tony O'Sullivan, from Durham, are using Squirts in a research project which aims to unravel the mystery to why human sperm sometimes fail to fertilise eggs when they come into contact.

Their findings show that in Sea Squirts the sperm contains a type of protein which triggers chemical changes in the egg, leading to the development of an embryo.

They believe the protein is defective or missing from the sperm of some infertile men.

Dr McDougall said: "Many of the problems associated with conception are due to a poor medical understanding of the basic biology that goes on during the early stages of life.

"Our studies will, we hope, one day be useful in treating human infertility conditions."

Sea Squirts are regarded as a delicacy by the French and Japanese.