Hosts species

Parasiticides can be roughly divided according to parasites, host species, or chemical classification (see Antiparasitic agents—anthelmintics Antiparasitic AGENTS—ANTiPROTOZOALs). By any classification, these are ubiquitous in the management and control of parasites of both companion and food-producing animals (2,3). 

Crystallization of 5 in the open air from an initially aprotic solvent (N,N-dimethyl-acetamide) led to a non-layered structure which is characterized by a three-dimensional lattice of loosely-packed host species interspaced by channel-type zones accommodating the solvent guest components (Fig. 9). 

Fig. 32a and b. Schematic illustration of intermolecular arrangements in the crystalline complexes of host 25 (taken from Ref.25>) a the two-dimensional hydrogen bonding pattern parallel to the ab plane (the shaded area represents the 1,1-diphenylcyclohexane framework) b the van der Waals type packing of the hydrogen bonded layers along the c axis (R represents the cyclohexyl ends of the host species)... 

Fig. 2.1. A tree representing the phylogeny of Wolbachia in arthropods (groups A and B) and filarial nematodes (groups C and D). Group designations correspond to those proposed by Werren etal. (1995) and by Bandi etal. (1998). The names at the terminal nodes are those of the host species. The tree is based on the ftsZgene sequence alignment used by Bandi etal. (1998). The tree was obtained using a distance matrix method (Jukes and Cantor correction neighbour-joining method).

Many species of parasitic nematodes are maintained in the laboratory in host species in which they are not found in nature. This has the potential consequence that the laboratory population is, in some way, different from the natural population. Transfer and adaptation of a parasite from a natural host into a different species in the laboratory entails a process of selection. The selection will act on the trait ability to survive in a nonnatural host . Most of the parasite population may have had little, or indeed no, ability to survive in the non-natural host. Thus, at its most extreme form, this selection will have been for the very small proportion of the parasite population with the ability to survive in a non-natural host. A consequence of this is that the parasite population will have gone through a genetic bottleneck. 

Investigating phenotypic diversity is not easy. A basic requirement is to have different lines of parasite available and in natural host species. However, being aware of the possibility of variation between individual worms would be a start. The few studies that have molecularly considered individual worms (Bianco et al., 1990 Fraser and Kennedy, 1990 Currie et al., 1998) have found variation between individual worms. Such variation may be the basis of some experimental noise . Perhaps efforts should be focused on this noise The phenotypic diversity that exists in natural, and even laboratory, populations of nematodes is maintained there by natural selection. This tells us, anthropomorphically, that such diversity matters to parasitic nematodes. It is hoped that this chapter has shown that it should also matter to us. 

Parasitic hymenoptera often eavesdrop on the pheromone communication of their host species. The type of host pheromone recognized depends on the host stage parasitized. Phoretic egg parasitoids are often attracted by the host sex pheromone, while species that parasitize later stages (larval, pupal) often do not respond to host sex pheromone components [ 11,42]. Larval parasitoids often recognize volatiles from the damaged host plant and/or host larval frass volatiles. Parasitoids of forest beetles respond to the beetle aggregation pheromones [42]. 

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