Ex vivo development of Phasmarhabditis spp. associated with terrestrial molluscs

Abstract

The success of Phasmarhabditis hermaphrodita (Schneider) Andrássy (Rhabditida: Rhabditidae) as a biological control agent of molluscs has led to a worldwide interest in phasmarhabditids. However, scant information is available on the lifecycle development of species within the genus. In the current study, the development of P. hermaphrodita, Phasmarhabditis papillosa, Phasmarhabditis bohemica and Phasmarhabditis kenyaensis were studied using ex vivo cultures, in order to improve our understanding of their biology. Infective juveniles (IJs) of each species were added to 1 g of defrosted homogenized slug cadavers of Deroceras invadens and the development monitored after inoculated IJ recovery, over a period of eight–ten days. The results demonstrated that P. bohemica had the shortest development cycle and that it was able to produce first-generation IJs after eight days, while P. hermaphrodita, P. papillosa and P. kenyaensis took ten days to form a new cohort of IJs. However, from the perspective of mass rearing, P. hermaphrodita has an advantage over the other species in that it is capable of forming self-fertilizing hermaphrodites, whereas both males and females are required for the reproduction of P. papillosa, P. bohemica and P. kenyaensis. The results of the study contribute to the knowledge of the biology of the genus and will help to establish the in vitro liquid cultures of different species of the genus.

Thirty years of slug control using the parasitic nematode Phasmarhabditis hermaphrodita and beyond

“…These results indicate that reproducing on an invertebrate can produce similar numbers of progeny as when the nematode kills a slug host and reproduces on it 128 . As well as P. hermaphrodita , other Phasmarhabditis species such as P. bohemica , P. bonaquaense and P. apuliae 136 can all be grown under laboratory conditions on dead slugs and have different generation times.…”

“…Also, the time it takes for new dauer juveniles to develop can differ with species. For example, P. bohemica had the shortest development cycle compared to P. hermaphrodita , P. papillosa and P. kenyaensis when grown on rotting slug ( D. invadens ), but it should be noted for industrial production that P. hermaphrodita is best as it is a hermaphrodite and not gonochoristic like the other species 136 . As well as differences between species, temperature also can severely affect the survival and growth of P. hermaphrodita .…”

“…For example, P. bohemica had the shortest development cycle compared to P. hermaphrodita, P. papillosa and P. kenyaensis when grown on rotting slug (D. invadens), but it should be noted for industrial production that P. hermaphrodita is best as it is a hermaphrodite and not gonochoristic like the other species. 136 As well as differences between species, temperature also can severely affect the survival and growth of P. hermaphrodita. Survival dramatically decreases at 25 °C and 35 °C but there is no difference at 5, 10 and 15 °C, 137 with the optimum growth temperature for P. hermaphrodita at 17 °C.…”