capabilities of the giant clam.
There are stories from the warmer countries that can make the blood
in your veins freeze. Stories about giant clams that can grab the leg of
an unsuspecting pearl diver, or even a tourist, and cause death by
In fact there are no reported occurrences of this at all, but giant
clams do exist, and they have a very interesting lifestyle. This giant
is the Tridacna gigas, and can be found mainly in the Pacific, although
its most location is the Australian Great Barrier Reef. The size of the
clams is quite imposing reaching up to 150 cm, although the largest
museum exhibit measured 1368.7 mm. Large specimens can weigh up to 225
The clam has quite a long life span of up to 40 years, and when in
season it releases a phenomenal number of eggs – the photo depicts
a clam releasing its eggs – there can be a billion in one spawn.
(If only we could teach our hens to do the same!) Such egg production in
relation to the relatively rare occurrence of the adult is an example of
an exceptionally harsh natural selection.
The eating habits of this creature are also very interesting. It is
assumed that an important, if not main source of nutrition for the clam,
is the unicellular algae Zooanthella, which grows inside the clam
itself. In normal conditions, the clam is open and the hinge which joins
the two halves of the shell together is anchored in the seabed. Thanks
to this, light penetrates to the inside of the clam and photosynthesizing algae
living there utilize the light to produce carbohydrates. The green
tinge as is seen in the photograph is an evidence of happy co-operation
of these two symbionts.
This is a great example of symbiosis – the clam gives out
plenty of carbon dioxide, which the algae assimilates, it then is eaten
by the clam which allows the further excrection of carbon dioxide. Sort
of like a snake eating its own tail. Of course the energy source
powering all of this is the sun.