People do not require a great deal of training to do adequate dissections to recover
parasites. University undergraduate classes can acquire a lot of valuable data. However,
people with some expertise or experience are required for many, but not all,
identifications.
Volunteers and volunteer networks can contribute cursory observations of large
parasites. In fresh water, these include some arthropods on gills and skin of fish.
Copepods on gills are sometimes visible with the naked eye; they are white or cream-coloured and often have two egg sacs. The fish louse, Argulus, is quite large, and can be
seen crawling on the body surface. Leeches also can be easily seen on the external
surface. Certain digenean metacercariae form blackspot and can be seen on the skin or in
the flesh of fish. As adults, these parasites infect birds or mammals. The large yellow
grub Clinostomum is found in pustule-like capsules just under the skin of fish, often in the
head or tail region. The huge, ribbon-like plerocercoids of the cestodes Ligula and
Schistocephalus can be found in the body cavities of cyprinids and sticklebacks,
respectively. These are tapeworms that use birds as definitive hosts. A large redish
nematode, Eustrongylides, also can be seen in the body cavity of fish. This nematode is a
larval stage, and its adults infect birds. Other tapeworm plerocercoids (e.g.
Diphyllobothrium, Triaenophorus) are clearly visible as cysts on the viscera or in the
musculature of fish. Adult cestodes such as Proteocephalus and acanthocephalans can be seen easily if the intestine is cut open.
Non-specialist volunteers should categorize the common macroparasite groups.
Flatworms include digeneans (or flukes) and cestodes (or tapeworms). These are flat, and
the cestodes are long and segmented, the digeneans short and rounded. Long narrow
worm-like organisms are nematodes (or roundworms). Tubular animals with a spiny
"head"-like portion are acanthocephalans (or thorny-headed worms). Crustaceans are
external parasites with hard body parts. Databases collected by volunteer groups should be
maintained independently from those of experts until verification of species is assured.
