This is the first of two lab sessions that center around important concepts in parasitology. These concepts are heavily illustrated with examples drawn primarily from among the species you studied during the first seven lab sessions. There should be little new material here, just a different way of viewing the material that you have been exposed to before. Most of the photos you will see are portions of the same photos that have already been used. Don't worry so much about the specific organism you are looking at. Be concerned with the general type of parasite that it is, and the type of adaptation being illustrated.
The format of the web pages for these two sessions is different from that used for the taxonomic labs. These pages use embedded graphics, so they will take longer to download, but there are fewer pages that need to be accessed during each lab session.
The material for these three lab sessions has been organized so that each lab deals with a few discrete topics. If you finish one of the shorter sessions early, please proceed to the next one. If you don't get around to finishing one of the longer sessions, finish it the next time.
Always be critical when applying the general topic of "adaptations" to specific examples. For example, one of the things you may notice is that parasites that don't seem to need attachment organs possess them nevertheless. Always keep in mind that there are evolutionary constraints on parasites, and they don't automatically lose features that aren't needed at the moment. So if you see a ventral sucker on a trematode that lives in the tissues of the liver, it is probably there because the ancestors of that species have ventral suckers, not because it has a present usefulness as an adaptation for attachment. Of course, if it were an "expensive" structure to produce or maintain, it would probably be selected against eventually. On the other hand, the cercaria of that liver fluke may need that ventral sucker to attach to vegetation prior to encysting, and the sucker may then simply persist throughout life.
An integral part of understanding parasitism is the concept of host finding. Parasites spend some or all of their existence in or on a host, and host finding deals with everything involved in getting into (or onto) a new host. It is a broad topic, and includes the obvious technique of the parasite actively searching for and getting into the host, as well as the less obvious technique of using one host to get into another one.
The first part of the section on host finding deals with problems and solutions for parasites that need to find a host in aquatic habitats. The second part considers terrestrial habitats.
The section on adaptations for attachment starts out by describing some of the basic morphological components that are used to provide attachment to the host. Many of these components appear in diverse taxa of parasites. Often, these "building blocks" are combined into specialized attachment organs, which are described next. These specialized holdfasts are usually specific to particular taxa. Finally, a series of examples is provided to illustrate how parasites in different habitats often use different sets of attachment structures, each suited to a particular habitat.