Lab 9: Adaptations for feeding, reproduction and dispersal

Overview

The last lab session dealt with problems associated with parasites finding and getting into (or onto) new hosts. This session deals with adaptations that help the parasites remain in the host, acquire the nutrients that they need to grow and reproduce, and disperse from their hosts.

Feeding

The section on adaptations for feeding is organized according to the location in or on the host where the parasite feeds, and the type of material it feeds on. In many cases feeding structures are easily seen with light-microscope photos, and these are the ones emphasized in this lab session. Some taxa have physiological or ultrastructural adaptations for feeding. These may be mentioned but are not illustrated.

Reproduction

The concept of reproduction includes anything responsible for the production of new individuals. Many parasites reproduce at several points during their life cycle, sometimes sexually and sometimes asexually. When studying how parasites reproduce, consider the consequences for both parasite transmission, and the host parasite relationship.

Reproduction may simply produce progeny that will be transmitted to new hosts. This has important consequences for parasite transmission but may have few consequences for the host in which these progeny are produced unless the progeny cause some sort of damage. Reproduction may also produce progeny that remain in the host and continue to develop.

Dispersal

The concept of dispersal deals with ways in which parasites are spread from the host, so that they increase their chances of encountering new hosts. Do they await ingestion by a blood-feeding vector, or do they simply pass out in the host's excreta as they are produced? Do they time when they leave, or simply take their chances. The concept of dispersal is not one where certain ways can be considered "better" than others. Rather, parasites use a variety of techniques, which all work (or the parasite would be extinct!) Some aspects of dispersal grade into the concept of host finding (Lab 8), but we had to start (and finish) somewhere.