Behavioural responses of Phasmarhabditis hermaphrodita (Nematoda: Rhabditida) to mucus from potential hosts

Abstract

Host recognition behaviours were investigated in the Rhabditid nematode Phasmarhabditis hermaphrodita. Infective juveniles were exposed to mucus samples from mollusc species of varying susceptibility (Arion hortensis agg., Deroceras reticulatum, Tandonia budapestensis, Helix aspersa, Limax flavus, Limax marginatus). Behavioural responses to the mucus were analysed using video-taped sequences. During contact with the mucus samples, infective juveniles decreased duration and frequency of forward crawling and increased frequency and duration of head thrusting and duration of head waving. Other host recognition behaviours identified included body waving and pushing. Most significant differences in behaviour recorded were between controls and during exposure to mollusc mucus; there were few significant differences between mollusc species. The results suggest that P. hermaphrodita forages by the 'cruise' method until mucus from potential hosts is encountered, but then concentrates its search behaviour, characterised by the decrease in forward crawling. However, there were no recorded behaviours that would differentiate between readily susceptible species and those with low or unknown susceptibility.

Natural variation in chemoattraction in the gastropod parasitic nematodes Phasmarhabditis hermaphrodita, P. neopapillosa and P. californica exposed to slug mucus

“…This strain has been in industrial production since 1994 fed on a monoxenic diet of Moraxella osloensis -a bacterium that was initially chosen as it produced the greatest number of virulent nematodes (Wilson et al, 1994, Wilson et al, 1995. Research using this same strain 6 to 10 years ago reported strong chemoattraction towards D. reticulatum, A. subfuscus and D. invadens (Hapca et al, 2007a, Nermut et al, 2012, Rae et al, 2009, Small & Bradford, 2008, which was not observed in this study. In fact the majority of nematodes remained at the point of application.…”

“…The terrestrial gastropod parasitic nematode Phasmarhabditis hermaphrodita is a lethal parasite of several pestiferous slug species (Wilson et al, 1993) and has been formulated into a successful biological control agent by BASF Agricultural Specialities called Nemaslug® (Rae et al, 2007). In order to find slugs in soil P. hermaphrodita is attracted to slug mucus, faeces and volatile cues (Hapca et al, 2007a, Nermut et al, 2012, Rae et al, 2009, Rae et al, 2006, Small & Bradford, 2008. These experiments have not only been carried out on agar plates but in more realistic ecological conditions in soil and sand (Hapca et al, 2007b, Nermut et al, 2012.…”

“…Experiments examining how P. hermaphrodita responds to host cues (Hapca et al, 2007a, Nermut et al, 2012, Rae et al, 2009, Small & Bradford, 2008 have all focussed on using the commercial strain designated DMG0001 (Hooper et al, 1999), which has been in culture for over 20 years (Wilson et al, 1993). There is no information on how other strains of P. hermaphrodita or Phasmarhabditis species respond to slug mucus.…”

Caenorhabditis elegansnematodes are not attracted to the terrestrial isopodPorcellio scaber

“…Alternatively, C. briggsae could be attracted to hosts and C. elegans just follows that species. P. hermaphrodita shares habitats and mollusk hosts with C. elegans and C. briggsae (Rae et al, 2009;Petersen et al, 2015;Schulenburg & Félix, 2017) and has been shown to chemotax toward the mucus, faeces, and volatile odorants of slugs and, in the case of snails, hyaluronic acid (Rae et al, 2006(Rae et al, , 2009Hapca et al, 2007;Small & Bradford, 2008;Nermut et al, 2012;Andrus et al, 2018). This observation suggests that C. elegans might prefer mollusks to isopods such as P. scaber and testing attraction to these species is a good future step.…”

Gastropod parasitic nematodes (Phasmarhabditis sp.) are attracted to hyaluronic acid in snail mucus by cGMP signalling

“…P. hermaphrodita has been shown to successfully protect crops such as lettuce and oilseed rape against slug damage (Wilson & Rae, 2015). P. hermaphrodita is able to infect and kill many slug species from the families Arionidae, Milacidae, Limacidae and Vaginulidae (Rae, 2017a) and uses mucus, faeces and volatiles to find slugs (Rae et al, 2006;Hapca et al, 2007a,b;Nermut et al, 2012;Small & Bradford, 2008). However, all of these behavioural studies have concentrated on studying chemoattraction towards slugs and not snails.…”