Infectivity of populations of the entomopathogenic nematodes Steinernema feltiae and Heterorhabditis megidis in relation to temperature, age and lipid content

Abstract

The infectivity of populations of the entomopathogenic nematodes Steinernema feltiae and Heterorhabditis megidis from Greece (GR) and the UK was compared using Galleria mellonella larvae as hosts. Dose-response tests showed that the two Steinernema populations did not differ in their establishment rates but they were more infective than H. megidis UK 211. The temperature range for infectivity was greater than that for development. However, the optimal temperature for infection and development for all populations was 23°C. Infectivity of Steinernema populations was not affected by storage for 12 weeks. However, 12 week-old H. megidis UK 211 infective juveniles (IJ) were less infective than fresh IJ. H. megidis GR showed very low establishment rates at all the doses and temperatures tested, before and after storage. The results are discussed in relation to the nematodes' climatic origin and lipid content. Pouvoir infestant de populations des nématodes entomopathogènes Steinernema feltiae et Heterorhabditis megidis suivant la température, l'âge et le contenu lipidique - Le pouvoir infestant de populations des nématodes entomopathogènes Steinernema feltiae et Heterorhabditis megidis provenant de Grèce et du Royaume Uni a été comparée, utilisant comme hôte Galleria mellonella. Les tests de dose/réaction ont montré que les taux d'établissement des deux populations ne diffèrent pas mais que leur pouvoir infestant était plus élevée que celle de H. megidis UK211. La plage des températures permettant l'infestation était plus étendue que celle relative au développement. Cependant, les températures optimales pour l'infestation et pour le développement étaient l'une et l'autre de 23°C pour toutes les populations. L'infestivité des populations de Steinernema n'a pas été affectée par un stockage de 12 semaines. Les juvéniles infestants de H. megidis UK211 âgés de 12 semaines montraient toutefois une infestivité plus faible que celle d'individus frais. Les specimens de H. megidis provenant de Grèce présentaient - que ce soit avant ou après le stockage - des taux d'établissement très faibles pour toutes les doses et les températures testées. Ces résultats sont discutés en relation avec l'origine climatique et le contenu lipidique des nématodes.

Rapid Age-Related Changes in Infection Behavior of Entomopathogenic Nematodes

“…This is probably not the case. Wright et al (1997), Grewal (2000), and Menti et al (2000) showed that S. feltiae IJs do not age rapidly. If whole life spans were considered, S. carpocapsae and H. bacteriophora might age in a more linear fashion, decreasing in infectiousness at a constant rate with time, whereas S. feltiae ages bimodally (Hay and Fenlon, 1995) or at different rates with time (Bohan and Hominick, 1997).…”

“…In this experiment, old nematodes were not extremely old in comparison with the typical IJ life span. Although older than Ͻ1-wk-old IJs, 2-to 4-wk-old S. feltiae IJs are rather young, considering they can live for several months (Grewal, 2000;Menti et al, 2000). It is, therefore, understandable that old and young S. feltiae were infectious.…”

Three dimensional study of wounded plant roots recruiting entomopathogenic nematodes with Pluronic gel as a medium

“…Attraction decreasing for 140 days and 180 days of storage time might be due to further declining energy (lipid) reserves as suggested by nematode bodies becoming increasingly transparent. The consumption of these reserves is thought to be associated with a decline in the ability to infect (Griffin, 2012;Menti et al, 2000). This phenomenon could be explained by phased infectivity in which infectivity is changed associated with aging (Dempsey and Griffin, 2002;Griffin, 2012;Ryder and Griffin, 2003).…”

Ecological characterization of Steinernema anatoliense (Rhabditida: Steinernematidae)

“…But Menti et al (2000) mentioned that this is not always the case because when they compared two S. feltiae and two Heterorhabditis megidis isolates recovered from Greece and UK, they didn't Wnd obvious diVerence between the isolates. In addition, the cold-adapted S. feltiae has been isolated from tropical Hawaii, and it still retains its coldadapted traits (Hazir et al, 2001).…”