The hydroid colony and its life cycle  The picture depicts an
example of what a hydroid colony can look like. It is also
possible to see the different stages of the hydroids life cycle.
Notice how the colony consists of several genetically identical
individuals called polyps. When the planula larvae have attached
themselves to the substrate, the first individual grows out and
starts catching food with its tentacles. The colony grows when
new polyps bud off. Polyps that comprise the colony can share
nutrition via the stems, and it is possible for different polyps
to have different functions within the colony. In the picture
above it is possible to see the feeding polyps that catch food
with their poisonousness tentacles and the reproductive polyps
that produce the free-swimming medusae that build either sperms
or eggs.    The colony that is depicted in the picture above is
about 3 cm high and the medusae are about 5 mm wide. The egg,
sperm and planula larvae are smaller than 1 mm.    Hydroid
colonies can vary