There are lots of different ways to categorize parasites. You could group them based on their morphology (anatomical structures), habitat (where they live...e.g. on the scalp or in the intestines), or on their evolutionary history. Biologists take all of these things into account when they place these animals into particular taxonomic groups (categories used for scientific identification). We refer to the categorization of these and other organisms as "taxonomy". As you read the posts on this blog, you will see the taxonomy listed for each parasite discussed. For those of you who are not familiar with taxonomy, here's a quick guide to help you follow the scientific jargon.
At the highest level of taxonomy, all organisms are placed into one of three groups, which are called Domains. These three Domains of life are:
(1) Archaea--Organisms that live in extreme environments and lack a true cellular nucleus
(2) Eubacteria--Organisms that do not live in extreme environments and lack a true cellular nucleus
(3) Eukarya--Organisms with a true cellular nucleus
For this blog, we will only be discussing organisms in Eukarya unless a particular parasite transmits a bacterial disease...in which case, the bacterium would belong in Eubacteria.
Within Eukarya are several groups we call Kingdoms. These Kingdoms include the plants (Plantae), fungi (Fungi), protists (Protista...but some texts will break this group into several kingdoms), and animals (Animalia). For this blog, we will be looking mostly at protists and animals, but occassionaly, I may feel like discussing fungal parasites. (Just for funzies! Gotta switch it up once in a while!)
Protist taxonomy is almost always in a state of flux. The little guys that we will look at from this group will all be unicellular (single-celled). They are difficult for biologists to classify because they mostly reproduce asexually. This makes using DNA to construct a picture of protists' evolutionary history near impossible....but lots of research focuses on protists, so maybe someday we will have all the answers. In the meantime, I will try to let you know about protist taxonomy on a post-by-post basis.
As for the animals, this group includes many different groups known as Phyla (sing. Phylum). The Phyla that interest us the most for this blog include:
(1) Platyhelminthes--"Flatworms", such as tapeworms, flukes, and monogenes.
(2) Nematoda--"Roundworms", such as whipworms, threadworms, and pinworms.
(4) Acanthocephala--"Thorny-headed Worms"
(5) Arthropoda--Crustaceans, tongue worms, insects, and arachnids.
Within each of these Phyla exist many groups we call Classes...within those Classes exist Orders...within those Orders exist Families...within those Families exist Genera (sing. Genus)...and finally, each member of a Genus is given a descriptive name or "specific epithet", sometimes referred to as a "species". However, in scientific literature, a "species" is always listed using the name of the Genus and of the specific epithet together. This is what we call "Binomial Nomenclature"...meaning that these two names (of the Genus and of the specific epithet) are used as a naming system to characterize a specific type of organism at the lowest taxonomic level. Binomial nomenclature is always underlined if handwritten or italicized if typed. (Except on blogspot...where they won't let you properly format the titles of posts!!!) The genus name is always capitalized, and the specific epithet is always left in an under-case format.