A supplement which has a surprise aphrodisiac effect on frogs and fish could aid the future survival of rare species.

Harpenden researcher Dr Keith Davies found that the reproduction rate among roundworms – or nematodes - along with molluscs, fish and frogs dramatically increased when the supplement was added to water.

It is hoped it could work for humans too.

Dr Davies, a senior lecturer at the University of Hertfordshire, and his colleague, Dr John Hart, CEO of Endocrine Pharmaceuticals Ltd, have reported on their findings in The Journal of Experimental Biology.

Guppy fish at London Zoo were given a peptide, a short protein, in their tank water. Six months later, they had produced four times as many offspring than unexposed fish.

Meanwhile an endangered amphibian from Madagascar, brown mantella frogs at Paignton Zoo in Devon, bred for the first time in a zoo anywhere in the world.

The protein was dissolved in water and misted on to the frogs in their rainforest enclosure, to achieve absorption through the skin.

Dr Davies went on: “It is good for the conservation and preservation for rare species, and zoos have been quite interested in our research.”

However, the boost to fertility was an unexpected finding as early on, the research focused on how such peptides affected the growth of breast cancer cells.

He added: “We wanted to test the supplement on a whole organism but when we tested it, it also affected fertility. It was surreptitious as we weren’t expecting it.

“I think we have a handle on the ‘switch’ that increases reproduction in nematodes, frogs and fish.

“We are working on seeing whether we can use it to increase or decrease fertility.”

Dr Hart, who coordinated various laboratories involved in the project, said: “What we have developed is an aphrodisiac which acts by lifting a natural brake on reproduction.

“This brake operates in the species we’ve tested, ranging from tiger stingrays to freshwater snails, so it should be present in mammals too including humans.”

The researchers are now looking for a commercial partner to make the product available for animal breeders, and also for clinicians treating infertile couples.