Stickleback Parasites
(version 1.0; 01/27/04)
Unlike most model
organisms used to study genetics and molecular biology, sticklebacks are caught
in the wild where they are subject to infection by parasites and diseases. Often they come back to the lab with
the fish. Some of these can cause
problems with survival and fertility in captivity and a few are contaigous and
can spread from tank to tank.
Listed below are a few we have encountered in our own collections. During the husbandry discussion in the
course, we will compare experiences with these and other parasites in different
labs and how best to avoid or cope with them.
Schistocephalus
(Schistocephalus solidus)[1] is a tapeworm dependent on two intermediate hosts and a
definitive host to complete its life cycle. The tapeworm life stage found in
fish is a larval or plerocercoid stage. Often several larval tapeworms may be
found in a single fish and can comprise a large portion of the total volume or
weight of the host. Fish infested by tapeworms often exhibit impaired movement
and can be identified by a swollen abdomen. When piscivorous birds such as
mergansers, blue heron, or other fish eating birds consume the fish, the larval
tapeworm attains sexual maturity within a few days, produces eggs for several
days, and then dies. Eggs are then expelled from the bird in fecal matter. Eggs
that reach the water are taken up by small crustaceans (copepods), where the
first larval or procercoid stage develops. The copepods are in turn eaten by
fish to complete the life cycle. Because of the complex life cycle, this common
parasite is not contaigous in the laboratory and we have never seen it in
lab-reared fish. However, we have
found that infested females do not produce eggs reliably and it is important to
make sure that you bring back healthy fish from the field if you intend to
breed them. Occasionally, we have
successfully de-wormed fish by squeezing out the parasite.