are found in the more marine conditions of the mangrove, and occur
in large numbers. The free-swimming larvae in the water attach themselves
head-first to almost any surface (including hard-bodied/shelled animals),
glue themselves with a strong cement, form calcareous plates around
them and then feed by sticking out feathery legs to catch plankton
when the tide rises!
Ships use extra fuel just to overcome the drag caused by accumulations
of these animals on hulls (also called fouling). Combatting this problem
is in fact a multi-million dollar industry for marine paint countries.
Usage of heavy metal paints and synthetic compounds cause damage to
the environment and it is hoped that a natural compound can be isolated
from some animals which appear never to get settled on.
on a tree trunk
Zonation of barnacles
on a mangrove
Euraphia forms a
tree trunks, you will see a classic case of zonation. The lower and
wetter parts of a tree trunk are inundated more frequently by the
sea, and it gets drier up the tree until you reach the driest parts
only splashed every two weeks by a spring tide.
In competition for space and thus feeding area, zonation occurs:
Barnacle clusters often
consist of both dead
and living individuals
The larger Acorn barnacles (Balanus
sp., Family Balanidae) are found on the lower, wetter parts of the
tree. The smaller Star barnacles
(Euraphia sp. formerly Chthamalus sp. Family Chthamalidae)
are forced to survive by adapting to the less favourable drier zones
further up the tree which Balanus is as yet unable to colonise.