Autor:innen:
Dr. Diana Rueda-Ramírez | Humboldt-Universität zu Berlin | Germany
Dr. Eric Palevsky | Newe Yaar Research Center, Agricultural Research Organization (ARO), Israel | Israel
Prof. Dr. Liliane Rueß | Humboldt-Universität zu Berlin | Germany
Pest suppression is one of the desirable functions of a healthy soil. Predatory Mesostigmata soil mites, with their high degree of omnivory, are one of the most remarkable groups performing this function. Only recently, it has been recognised that the bottom-up effect of the diet is important for these organisms´ fitness, which ultimately affects their performance as biocontrol agents of soil pests. In below-ground systems, free-living nematodes (FLN) are an important food source and provide essential nutrients such as omega 3 long-chain polyunsaturated fatty acids (ω3-LC PUFAs). Previous studies showed that numerous species of Mesostigmata prefer FLN and, in many cases, a nematode-based diet has a positive effect on mite performance. Here we assess the food quality of nematodes for the maintenance of predator fitness, i.e. development, reproduction and lipid content. We selected two mite species, different in size and morphology, collected from vegetable crops in Israel. The selected nematodes were five species of FLN, all collected from the same fields, and one species of phytoparasitic nematode. Depending on species and trophic group, nematodes show different fatty acid patterns and both mite species reflect the PUFA pattern of the diet. All nematode species were able to produce ω3-PUFA de novo, except the bacterial feeder Acrobeloides aff. bodenheimeri, which had the highest proportion of ω6-PUFA. Interestingly, the latter nematode, without ω3-LC PUFA, was the best diet for both mites. Macrocheles aff. scutatus, a medium-sized mite with a holodorsal shield and a width greater than 0.5 times the length, fed and developed on all nematodes except the entomophilious nematode Oscheius tipulae. Even it was able to complete its development feeding on the plant parasitic Meloidogyne incognita, its reproduction was almost zero. Protogamasellopsis zaheri, a small-medium-sized mite with a split dorsal shield and a body width less than 0.5 times the length, developed and reproduced with all nematodes, with M. incognita being an intermediate diet. Our results demonstrate that nematode species vary in their nutritional quality as prey and that food quality is predator species dependent, which will affect the biocontrol potential on nematode plant parasites. We hypothesise ω6-PUFA may play an important role in the reproductive and developmental parameters of some mesostigmatid mites; however, other factors such as nematode size and behavior may play an important role