We demonstrated in this study that laboratory mass cultures offer
optimal conditions for the development of epibionts. Therefore, it is
important to examine newly collected copepods for the presence of
epibionts prior to initiating copepod cultures. Generally, infested
cultures lead to massive mortality of the host. In this study we
attempted to maintain the infested culture as long as possible. This
allowed us to describe qualitatively the dynamics of the epibiont-host
interaction and to quantify the role of small-scale processes. The presence
of epibionts significantly affected the swimming activity of males
and therefore decreased their ability to search for and grasp females,
leading to reduced mating success. During the maximum infestation
period, the escape behavior (jump) of copepods was severely reduced,
and no mating success was recorded. In field conditions the observed
changes in the behavior of infested males would increase their vulnerability
to predators. Although the population of E. affinis reached a critical
low density in the aquarium, the few remaining copepods
recovered from the negative effect of infestation, and restored their
fecundity, leading to the improvement in population recruitment. We
thus confirmed that the population of E. affinis from the Seine estuary
could rapidly overcome a very critical situation imposed by artificially
induced heavy infestation by their specific epibiont Zoothamnium sp.