Friday, June 18, 2010

The Knysna seahorse - a curious, legendary African fish

Seahorses are thought to have evolved at least 40 million years ago and have survived from ancient times with only very small changes in body structure or organ function.

They are unusual fish that have captured the imagination of artists, writers and poets, being found in the mythology, legends, folklore and superstitions. In fact some people still believe that these endearing creatures exist only in fables and children's stories- This time, they are wrong.

Given their unusual appearance and extraordinary biology, it is not surprising that Asians have credited seahorses with magical powers- like they always do. Seahorses are therefore exploited as traditional medicines. This use has led to concerns that the natural seahorse stocks are being depleted at a rapid and unsustainable rate.

The pregnant male!

Seahorses are the only fish species where the male experiences a true pregnancy. The pregnancy is considered true, as fertilization is internal and the eggs are held in a pouch consisting of tissues, which contain a capillary network which provides oxygen and placental fluid to the embryos.

The pregnancy of the Knysna seahorse lasts up to two or three weeks. The male will then give birth to between 5 and 200 young from one pregnancy and during the male's pregnancy the female will be busy producing more eggs. This means that just a few hours after the male giving birth, the female will once again pass her now ripe eggs into the male's pouch. The male will therefore be pregnant throughout the entire breeding season.

Flirting seahorses?

The seahorses mate monogamously for the entire breeding season. Every day the pair will come together in a ritualistic flirtatious dance to reinforce their connection. This ritual helps keep the pair synchronized reproductively. While the male is pregnant he will move very little, which for a seahorse means not more than a few centimeters.

If a mate is removed or dies, it will take weeks to find a new mate, that is, if it is able to at all! This is because seahorses live in isolated groups and move very little. It is thus extremely difficult to find another seahorse in the same part of the reproductive cycle.

So female look for a mate?

Since it is the male that becomes pregnant it was previously believed that it would be the females that competed for the male partners. This however is simply not the case. Like in most species, it is the male that competes with other males to attract and defend his female seahorse. So, it would appear that the male actually wants to be pregnant. The seahorse male is sounding more and more like every woman's perfect mate! Muwahaha.

Source: Science Africa