The good parasite

Written by Thomas Hesselberg

Thursday, 23 August 2007

The freshwater amphopod Gammarus roeseli. Photo: Prof. Dr. U. Heitkamp.
Usually we think of parasites as organisms that are very harmful to their host and indeed a parasite is defined as having a negative impact on its host. However, there are also certain situations where parasites can have a positive effect on their host. A French research team investigated a freshwater amphipod, Gammarus roeseli, a small crustacean, and its parasite, a worm belonging to the group of acanthocephalans.

Although Gammarus roeseli lives in freshwater, it is tolerant to some level of salinity in the water. The researches tested the behaviour as well as ATPase activity in gill homogenates of infected and non-infected amphipods when placed in water with a range of different salinities. They found that infected individuals show a higher tolerance toward salinity than non-infected individuals. Furthermore, they tried to relate the increased salinity tolerance of infected individuals to an increase in gill ATPase activity, which is used in osmoregulation.

They found, however, no difference. Instead the parasite may change the oxygen consumption of the host and its haemolymph concentration. However, although the parasite helps the amphipod to survive better in salt water, it probably has an ulterior motive for that. The fact is that the parasite requires a final water bird host to finish its development. And water birds are predominantly found in brackish and salt water…

Source:
Piscart, C., Webb, D. and Beisel, J. N. (2007). An acantocephalan parasite increases the salinity tolerance of the freshwater amphipod Gammerus roeseli (Crustacea: Gammaridae). Naturwissenschaften 94: 741-747.

Tag it:

Add as favourites (13) |

Quote this article on your site | Views: 786 | E-mail

Be first to comment this article

Only registered users can write comments.
Please login or register.