A male that really does get pregnant

The Knysna Heads and estuary

My home town in South Africa is Knysa, pronounced NIGH – ZNUH.  Apparently the name comes from the Khoi-San language for ‘hard-to-get-to”, probably because of the dense forests that covered the region.  These are the forests of the legendary Knysna elephants, of which conservationists now believe only about 12 survive.

Almost equally rare is the Knysna seahorse (Hippocampus capensis), which makes its home in only three estuaries in the world – the Knysna, Swartvlie, and Keurbooms.  Because of this minute habitat it is regarded as an endangered species.  Fortunately, despite the widespread use of traditional medicines in South Africa, this seahorse is not used for any, unlike seahorses in other parts of the world.

A pregnant male - only 5 - 12 cms long

The Knysna seahorse is between 5 and 12 cms long, and surprisingly they are fish, with gills, backbone, swim bladder and fins.  Over millions of years, its scales have come together to form an insect-like outer protective layer that looks like a horse.  It swims very slowly, usually upright.

Seahorses have no teeth or stomachs, so eating needs to happen frequently because they cannot store food.  Typically they will hang onto the reed with their tail and change color so as to be camouflaged.  As shrimp or zooplankton float by, they suck them in through their tubular mouth.

A most peculiar aspect of these strange creatures is that the young, sometimes up to 200, are born from the male!  The female produces the eggs, and when ripe passes them to a special pouch the male has, where they are fertilized.  Gestation is about 2 – 3 weeks.  Then the cycle repeats itself.  The seahorse is the only fish species where the male actually becomes pregnant.

During the mating season, a pair of seahorses is monogamous, with the ‘pregnant’ male moving very little (only a few centimeters, hanging onto its piece of grass or reed), while the female can wander around in search of food.  When the female returns, there is a ritualistic flirting to strengthen their bonding.  Of course, this makes interlopers unsuccessful if they try to take over another seahorse’s mate.

Very little is known about the Knysna Seahorse, but recently a few research projects have started through Rhodes University in Grahamstown.  We all hope that the management of the three estuaries allows Hippocampus capensis to survive.

Stan - Thursday (rushing to get to our fourth book event)