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  Yahoo News 19 Jan 07
Sperm secrets of male seahorses uncovered
By Patricia Reaney

LONDON (Reuters) - Scientists have uncovered for the first time secrets about how male seahorses produce their young that could prove valuable in conservation efforts to save the vulnerable species.

Unlike other animals and humans in which the female becomes pregnant, male seahorses carry their unborn in a pouch on their body and give birth to their young. They manage to reproduce very efficiently with small amounts of sperm and have a short window of opportunity in which to fertilize the female eggs.

"We were delighted to finally be able to uncover the male seahorse's fertilization mechanism, a fascinating area of seahorse reproduction that has been neglected until now," Professor Bill Holt, of the Zoological Society of London (ZSL), said on Friday.

After observing and filming the mating behavior of the yellow seahorse, Holt and his team discovered that when it comes to efficiently reproducing male seahorses are way ahead of humans and most other species.

But seahorses face threats from habitat loss, pollution and fishing and are listed as vulnerable on the World Conservation Union, or IUCN, Red List of endangered species.

"We did sperm counts and observations of the mating behavior and have videos of the whole sequence of the mating. With all of the evidence together you can see exactly what is going on," said Holt.

To overcome the lack of sperm yellow male seahorses produce two types of sperm, according to the findings reported in the Journal of Experimental Biology. "But even more surprising, the sperm they produce is expelled from their bodies into the sea water. But the sperm still manage to find the male pouch where the females have deposited the eggs," said Holt. "We can't explain exactly how that actually happens."

All the female seahorse has to do is produce the eggs and transfer them to the pouch -- a process that takes 5-10 seconds. The sperm also have to find their way into the pouch in that time because once the eggs are transferred the pouch closes and is sealed.

Although the research focused on the yellow seahorse, a species found in Southeast Asia, Australia and Japan, Holt and his team said all seahorses reproduce in the same way.

Adult yellow seahorses measure 8 cm (3.1 inches) and live about five years. Unlike humans who can produce billions of sperm but normally only one or two young at a time, seahorses give birth to about 100.

"If they have only a few hundred sperm and are producing a hundred offspring that is amazing in the world of sperm," Holt added.
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