China
Africa
Explore chapters and articles related to this topic
The Ecology of Parasitism
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Density-dependent competitive interactions are common among parasites. Here we will focus on intraspecific competition (as between two individual tapeworms of the same species), as opposed to interspecific competition (as between two different tapeworm species), which will be discussed further in the section on infracommunities. Three types of intraspecific competition are usually recognized: interference competition; resource or exploitative competition; and apparent competition. Interference competition refers to active aggression between interacting individuals. One example is provided by the trematode Echinostoma paraensei, which in the snail Biomphalaria glabrata produces a mother redia with a large sucker able to attack and damage or kill later-arriving parasites of the same species but of different genotypes. Other trematode larvae also attack conspecifics. In parasitoids, the same phenomenon occurs when multiple individuals of the same species but different parentage end up in the same host species.
The Ecology of Parasitism
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2015
Eric S. Loker, Bruce V. Hofkin
Density-dependent competitive interactions are common among parasites. Here we will focus on intraspecific competition (as between two individual tapeworms of the same species), as opposed to interspecific competition (as between two different tapeworm species), which will be discussed further in the section on infracommunities. There are three types of intraspecific competition: interference competition; resource or exploitative competition; and apparent competition. Interference competition refers to active aggression between interacting individuals. One example is provided by the trematode Echinostoma paraensei, which in the snail Biomphalaria glabrata produces a mother redia with a large sucker able to attack and damage or kill later-arriving parasites of the same species but of different genotypes. Other trematode larvae also attack conspecifics. In parasitoids, the same phenomenon occurs when multiple individuals of the same species but of different parentage end up in the same host species.
Therapeutic implications of NK cell regulation of allogeneic CD8 T cell-mediated immune responses stimulated through the direct pathway of antigen presentation in transplantation
Published in mAbs, 2018
J.I. Rodriguez-Barbosa, M.C. Ferreras, L. Buhler, N.D. Jones, P. Schneider, J.A. Perez-Simon, M.L. del Rio
Newly generated cells (recent thymic emigrants and peripheral cell division) compete in the immune system with resident cells for survival.36 Sometimes one population prevents other population from occupying a particular niche and from exploiting the resources there (interference competition). In other occasions, and more often, different populations may have common needs for resources present in the niche, which is in limited supply (exploitation competition).36 The CD8 T cell independent niche can, however, be invaded by other cells, such as NK cells, an example of exploitation competition, which is in agreement with our results. This NK cell exploitation of the CD8 T cell niche may account for the delay of graft rejection. Our data in this sense is in agreement with that reported by Zecher´s work using immunodeficient and T cell-depleted immunocompetent recipients who provided evidence in favor of the role of NK cells in modulating CD8 T cell responses, not by killing homeostatically proliferating T cells, but by competing for T cell growth factors.21 Our findings suggest that this competition for common resources may provide an advantage to NK cells that would reduce the availability of these cytokines to the alloreactive repertoire of CD8 T cell reacting against bm1 antigens. Therefore, reaching the threshold frequency of alloantigen specific CD8 T cells necessary to initiate rejection would take longer and consequently graft rejection would be delayed.
Intraguild predation between Pristionchus pacificus and Caenorhabditis elegans: a complex interaction with the potential for aggressive behaviour
Published in Journal of Neurogenetics, 2020
Kathleen T. Quach, Sreekanth H. Chalasani
Two general forms of competition, exploitation and interference, are involved in this basic form of intraguild predation. First is exploitative competition, in which two species indirectly negatively affect each other by consuming the same resource and thereby reducing resource abundance (Case & Gilpin, 1974; Tilman, 1982; Vance, 1984). If two species have the exact same resource needs and only engage in exploitative competition, the species that is more efficient at consuming the shared resource should theoretically emerge as the winner, while the less efficient consumer is driven to extinction or a different niche (Vance, 1984). In order for intraguild predation to be robust and its participating species to coexist, it must include a second form of competition, interference competition (Amarasekare, 2002; Hsu, 1982; Vance, 1984). In interference competition, one species reduces the ability of the other to exploit the shared resource (Case & Gilpin, 1974; Hsu, 1982; Vance, 1984). Intraguild predation involves a severe form of interference competition in which the competitor is killed. With these two forms of competition in mind, there are three key predictions of a simple model of stable intraguild predation (Holt & Huxel, 2007; Holt & Polis, 1997):The intraguild prey is superior in exploiting the shared resource.The intraguild predator should have greater fitness from predating on the intraguild prey than from competing on a purely exploitative level.The intraguild predator, by reducing the population of the more efficient consumer species, indirectly increases the abundance of the shared resource at equilibrium.