By Jim E. Quarles.
Before introducing you to your worst nightmare, let me state, that
following this part of the articles on fish diseases, I will outline some
of the medications that are used in the vain hope that some hobbyist will
realize the actual harm they are causing in nature by the methods they
employ to treat their sick fish. This has reached the point of endangering
treatment of human diseases.
The roundworms are related to radiferous, but two look totally
different. The horsehair worms are also related. Most nematodes are
free-living in rock, soil, freshwater and marine water, mud, debris, and
decaying sludge, leaf litter, and animal waste. They are found everywhere,
even in Arctic Ice, and they are the most abundant animals on earth.
They are also parasites or mimmensals in plants and animals where they
may be harmless or indeed very harmful. Some are agricultural pests, such
as root knot, and others are major parasites involved with humans.
Hookworm, ascaris, pinworm and trichinosis, in the temperate zone and
blindness, loa loa, guinea worm, filariasis, and elphantisis in tropical
countries. All of the above are caused by nematode infections.
Some are useful, micro worms and vinegar eels are both cultured as food
for baby fishes. The micro worms were discovered from a bar in soggy mats
under beer mugs, vinegar eels in apple cider. Many are essential to
natural decomposition of organic matter. Also, many free living ones feed
on diatoms or algae, while others are carnivorous. Nematodes live inside
all invertebrates and vertebrates, including fishes. Only a few kinds have
been reported as parasites inside aquarium fishes, mostly in hatcheries,
but that undoubtedly because they've not been sufficiently studied. Not
long ago anisakine worms were discovered in raw fish and shellfish, the
discovery was made when sushi and sashimi were popularized in Hawaii.
Anisakine worms are big worms and wander about through tissues of people
sometimes coming out the nose. They normally live in sea lions and seals
and never to quite find a comfortable resting-place in people maybe we
just don't taste good to them!
These parasites become a real problem for aquarists. You may ask why
don't we just zap them with formalin or copper? The problem has been
unusual structure and metabolism and resistance to our standard drugs. We
only now understand their physiology and so that we can develop a drug
that will interfere with the nematode function what will not at the same
time interfere with a fish function. Most truly effective preparations are
not on the shelves of aquarium shops nor are they released to the pet
trade as over the counter products. However you will find them in dog, cat
and horse foods.
So just what is some of the biological factors of Nematodes that make
them so successful in nature? One thing to notice is that they are rounded
in cross sections, thin, elongated, and in most cases pointed at both ends
but coiled as just one. They have tough skin, which is called cuticle, and
it's as difficult to get through as the cuticle of your fingernails. This
enables them to go anywhere, through anything, and resist heat, drying,
chemicals, digestive juices, and lots of predators. And if that was not
enough protection, below the cuticle, is an equally tough muscle that is
mostly longitudinal and this is why then tend to coil up like a watch
The sexes are separate, with males and females often of different sizes
and shapes. Most lay eggs but others are live bearers. In explaining their
life cycle it must be noted that they pass through several larval
developmental stages, and like many parasites this occurs in different
hosts, but some only require a single host to complete its life cycle.
Nematode Parasites of fishes
When considering fish parasites, here, I am only referring to those
most commonly found in tropical fish kept by the hobbyist either as a
hatchery product or simply for personal enjoyment.
This of course is a little known or studied subject, and we are
learning more about these parasites all the time. More is known about
Nematode parasites in marine game fish than the fish normally found in the
Nematodes in aquarium fish are most often discovered when they encyst
on the flank, causing a huge boil that can be lanced. They also infest the
intestinal tracts of guppies and other live bearers.
I first became interested in the parasites while developing my discus
fish hatchery. Tapeworm and other forms of roundworms can be said to be
common in all wild caught discus and angelfish.
In most cases I have found that while all fishes have parasitic worms
in their intestinal tract, only rarely will they cause illness. Out breaks
are more often a consequence of crowding, resulting in constant
reunification. The adage: "A clean tank is a healthy tank" has
never been truer than in the case of parasites.