Fish Species at  Fish Parasites   By Margaret A. Wissman, DVM,
DABVP |  Page 1 of 2  Printer Friendly  Parasites are a group of
organisms that may or may not cause illness in aquarium fish,
depending on a number of factors. Before we learn about the
different fish parasites, let's find out exactly what a parasite
is.  Parasites have arisen by evolution from what were free-
living animals (animals not living on or in another animal, and
not reliant on another to draw their nourishment). They often
resemble their ancestors a good deal, but have become better
adapted for a parasitic life. Some parasites have developed
organs, such as suckers for hanging on to their hosts. Many lay
tremendous numbers of eggs because the chances that any one egg
will infect a new host are incredibly small. Parasites have
generally changed biochemically and immunologically, so they can
survive inside another organism and not be digested or killed.
Some of them depend on their hosts for compounds that their
ancestors could synthesize