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Rae R, Sheehy L, McDonald-Howard K. Thirty years of slug control using the parasitic nematode Phasmarhabditis hermaphrodita and beyond. PEST MANAGEMENT SCIENCE 2023; 79:3408-3424. [PMID: 37394691 DOI: 10.1002/ps.7636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 06/23/2023] [Accepted: 06/27/2023] [Indexed: 07/04/2023]
Abstract
Several slug species are highly pestiferous and threaten global sustainable agriculture. Current control methods rely heavily on metaldehyde pellets, which are often ineffective, harm nontarget organisms and have been banned in some countries. A viable alternative is the parasitic nematode Phasmarhabditis hermaphrodita (and recently P. californica), which has been formulated into a biological control agent (Nemaslug®) to control slugs across northern Europe. Nematodes are mixed with water and applied to soil where they seek out slugs, penetrate behind the mantle and kill them in 4-21 days. Phasmarhabditis hermaphrodita has been on the market since 1994 and since then there has been ample research on its use. Here we review the research carried out on P. hermaphrodita over the last 30 years since its development and release as a commercial product. We provide information on life cycle, worldwide distribution, history of commercialisation, gastropod immunity, host range, ecological and environmental factors that affect its success in the field, bacterial relationships, and summarise results of field trials. Finally, we suggest future directions for P. hermaphrodita research (and other Phasmarhabditis species) to enhance its use as a biological control agent to control slugs for the next 30 years. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Affiliation(s)
- Robbie Rae
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK
| | - Laura Sheehy
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK
| | - Kerry McDonald-Howard
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK
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Tandingan De Ley I, Kiontke K, Bert W, Sudhaus W, Fitch DHA. Pellioditis pelhamensis n. sp. (Nematoda: Rhabditidae) and Pellioditis pellio (Schneider, 1866), earthworm associates from different subclades within Pellioditis (syn. Phasmarhabditis Andrássy, 1976). PLoS One 2023; 18:e0288196. [PMID: 37672545 PMCID: PMC10482300 DOI: 10.1371/journal.pone.0288196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 07/27/2023] [Indexed: 09/08/2023] Open
Abstract
Recently, much attention has been focused on a group of rhabditid nematodes called Phasmarhabditis, a junior synonym of Pellioditis, as a promising source of biocontrol agents for invasive slugs. Pellioditis pelhamensis n. sp. was first isolated from earthworms near Pelham Bay Park in Bronx, New York, USA, in 1990 and has been found to be pathogenic to slugs as well as some earthworms. It has also been used in several comparative developmental studies. Here, we provide a description of this species, as well as a redescription of a similar earthworm-associated nematode, Pellioditis pellio Schneider, 1866, re-isolated from the type locality. Although P. pelhamensis n. sp. and P. pellio are morphologically similar, they are reproductively isolated. Molecular phylogenetic analysis places both species in a clade that includes all species previously described as Phasmarhabditis which are associated with gastropods. Phasmarhabditis Andrássy, 1976 is therefore a junior synonym of Pellioditis Dougherty, 1953. Also, Pellioditis bohemica Nermut', Půža, Mekete & Mráček, 2017, described to be a facultative parasite of slugs, is found to be a junior synonym of Pellioditis pellio (Schneider, 1866), adding to evidence that P. pellio is associated with both slugs and earthworms. The earthworm-associated species P. pelhamensis n. sp. and P. pellio represent different subclades within Pellioditis, suggesting that Pellioditis species in general have a broader host range than just slugs. Because of this, caution is warranted in using these species as biological control agents until more is understood about their ecology.
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Affiliation(s)
- Irma Tandingan De Ley
- Department of Nematology, University of California, Riverside, CA, United States of America
| | - Karin Kiontke
- Department of Biology, New York University, New York, NY, United States of America
| | - Wim Bert
- Nematology Unit, Department of Biology, Ghent University, Ghent, Belgium
| | - Walter Sudhaus
- Institut für Biologie/Zoologie, Freie Universität Berlin, Berlin, Germany
| | - David H. A. Fitch
- Department of Biology, New York University, New York, NY, United States of America
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Nematodes and trematodes associated with terrestrial gastropods in Nottingham, England. J Helminthol 2022; 96:e81. [DOI: 10.1017/s0022149x22000645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Abstract
A parasitological survey of terrestrial slugs and snails was conducted at popular dog walking locations across the city of Nottingham, with the intensions of finding gastropods infected with parasites of medical (or veterinary) importance such as lungworm (metastrongyloid nematodes) and trematodes. A total of 800 gastropods were collected from 16 sites over a 225 km2 area. The extracted nematodes and trematodes were identified by molecular barcoding. Of the 800 gastropods collected, 227 were infected (172 had nematode infections, 37 had trematode infections and 18 had both nematode and trematode infections). Of the nematode infected gastropods genotyped, seven species were identified, Agfa flexilis, Angiostoma gandavense, Angiostoma margaretae, Cosmocerca longicauda, Phasmarhabditis hermaphrodita, Phasmarhabditis neopapillosa and an unknown Cosmocercidae species. Of the trematode infected gastropods genotyped, four species were identified, Brachylaima arcuate, Brachylaima fuscata, Brachylaima mesostoma and an unknown Plagiorchioidea species. No lungworm species were found within the city of Nottingham. To our knowledge, this study represents the first survey of gastropod-associated nematodes and trematodes in the East midlands of the United Kingdom.
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Natural variation in host-finding behaviour of gastropod parasitic nematodes ( Phasmarhabditis spp.) exposed to host-associated cues. J Helminthol 2021; 95:e10. [PMID: 33622419 DOI: 10.1017/s0022149x20000401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The gastropod parasitic nematode Phasmarhabditis hermaphrodita has been formulated into a successful biological control agent (Nemaslug®, strain DMG0001) used to kill slugs on farms and gardens. When applied to soil, P. hermaphrodita uses slug mucus and faeces to find potential hosts. However, there is little information on what cues other species of Phasmarhabditis (P. neopapillosa and P. californica) use to find hosts and whether there is natural variation in their ability to chemotax to host cues. Therefore, using chemotaxis assays, we exposed nine wild isolates of P. hermaphrodita, five isolates of P. neopapillosa and three isolates of P. californica to mucus from the pestiferous slug host Deroceras invadens, as well as 1% and 5% hyaluronic acid - a component of slug mucus that is highly attractive to these nematodes. We found P. hermaphrodita (DMG0010) and P. californica (DMG0018) responded significantly more to D. invadens mucus and 1% hyaluronic acid than other strains. Also, P. hermaphrodita (DMG0007), P. neopapillosa (DMG0015) and P. californica (DMG0017) were superior at locating 5% hyaluronic acid compared to other isolates of the same genera. Ultimately, there is natural variation in chemoattraction in Phasmarhabditis nematodes, with some strains responding significantly better to host cues than others.
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Cutler J, Rae R. Pathogenicity of wild and commercial Phasmarhabditis hermaphrodita exposed to the pestiferous slug Deroceras invadens. J Invertebr Pathol 2020; 174:107435. [PMID: 32561403 DOI: 10.1016/j.jip.2020.107435] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 06/12/2020] [Accepted: 06/13/2020] [Indexed: 11/18/2022]
Abstract
Many terrestrial gastropods are pestiferous and pose a significant threat to agriculture, horticulture and floriculture. They are usually controlled by metaldehyde based pellets but an alternative control method is the slug parasitic nematode Phasmarhabditis hermaphrodita, which has been formulated into a biological control agent (Nemaslug®) for use by farmers and gardeners to kill certain pestiferous slug species in 4-21 days. The current strain of P. hermaphrodita (called DMG0001) has been used in commercial production since 1994, but there is little information about the pathogenicity of wild strains of P. hermaphrodita towards slugs. Here, we exposed the pestiferous slug Deroceras invadens to nine wild isolated strains of P. hermaphrodita (DMG0002, DMG0003, DMG0005, DMG0006, DMG0007, DMG0008, DMG0009, DMG0010 and DMG0011) and the commercial strain (DMG0001) to three doses (0, 500 and 1000 nematodes per ml). Survival and feeding were recorded over 14 days. All wild P. hermaphrodita strains (other than DMG0010) and P. hermaphrodita (DMG0001), applied at 500 nematodes per ml, caused significant mortality to D. invadens compared to an uninfected control. Similarly, all P. hermaphrodita strains applied at 1000 nematodes per ml, caused significant mortality to D. invadens compared to an uninfected control. Overall, all wild P. hermaphrodita strains (other than DMG0011) caused significantly more mortality than P. hermaphrodita DMG0001 at one or both nematode concentrations. In summary, we have found some wild P. hermaphrodita strains were more virulent than P. hermaphrodita (DMG0001). Ultimately, these strains could potentially be developed as alternative, efficient biological control agents for use against slugs.
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Affiliation(s)
- James Cutler
- Liverpool John Moores University, School of Biological and Environmental Sciences, Byrom Street, Liverpool L33AF, UK.
| | - Robbie Rae
- Liverpool John Moores University, School of Biological and Environmental Sciences, Byrom Street, Liverpool L33AF, UK
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Luong LT, Mathot KJ. Facultative parasites as evolutionary stepping-stones towards parasitic lifestyles. Biol Lett 2019; 15:20190058. [PMID: 30991912 DOI: 10.1098/rsbl.2019.0058] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Parasites and parasitic lifestyles have evolved from free-living organisms multiple times. How such a key evolutionary transition occurred remains puzzling. Facultative parasites represent potential transitional states between free-living and fully parasitic lifestyles because they can be either free-living or parasitic depending on environmental conditions. We suggest that facultative parasites with phenotypically plastic life-history strategies may serve as evolutionary stepping-stones towards obligate parasitism. Pre-adaptations provide a starting point for the transition towards opportunistic or facultative parasitism, but what evolutionary mechanism underlies the transition from facultative to obligate parasitism? In this Opinion Piece, we outline how facultative parasites could evolve towards obligate parasites via genetic assimilation, either alone or in combination with the Baldwin effect. We further describe the key predictions stemming from each of these evolutionary pathways. The importance of genetic assimilation in evolution has been hotly debated. Studies on facultative parasites may not only provide key insights regarding the evolution of parasitism, but also provide ideal systems in which to test evolutionary theory on genetic accommodation.
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Affiliation(s)
- Lien T Luong
- 1 Department of Biological Sciences, University of Alberta , Edmonton, Alberta, Canada T6G 2E9
| | - Kimberley J Mathot
- 1 Department of Biological Sciences, University of Alberta , Edmonton, Alberta, Canada T6G 2E9.,2 Canada Research Chair in Integrative Ecology, University of Alberta , Edmonton, Alberta, Canada T6G 2E9
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Abstract
Summary
The terrestrial gastropod parasitic nematode Phasmarhabditis hermaphrodita is the only nematode that evolved to infect and kill slugs and snails. Because of this ability it has been formulated into a biological control agent for gardeners. In this Forum article, the author outlines several reasons why P. hemaphrodita is a nematode that is worth studying, including its ability to control the behaviour and kill slug hosts. The author discusses how P. hemaphrodita is being developed as a model nematode to be used to study the genetic evolution of parasitism, as well as potential research ideas for the future.
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Affiliation(s)
- Robbie Rae
- School of Natural Sciences and Psychology, Liverpool John Moores University, Byrom Street, Liverpool, L33AF, UK
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Gastropod parasitic nematodes ( Phasmarhabditis sp.) are attracted to hyaluronic acid in snail mucus by cGMP signalling. J Helminthol 2018; 94:e9. [PMID: 30428945 DOI: 10.1017/s0022149x18000986] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Phasmarhabditis hermaphrodita is a parasitic nematode of terrestrial gastropods that has been formulated into a biological control agent for farmers and gardeners to kill slugs and snails. In order to locate slugs it is attracted to mucus, faeces and volatile cues; however, there is no information about whether these nematodes are attracted to snail cues. It is also unknown how wild isolates of P. hermaphrodita or different Phasmarhabditis species behave when exposed to gastropod cues. Therefore, we investigated whether P. hermaphrodita (commercial and wild isolated strains), P. neopapillosa and P. californica were attracted to mucus from several common snail species (Cepaea nemoralis, Cepaea hortensis, Arianta arbustorum and Cornu aspersum). We also examined whether snails (C. aspersum) collected from different locations around the UK differed in their attractiveness to wild isolates of P. hermaphrodita. Furthermore, we also investigated what properties of snail mucus the nematodes were attracted to, including hyaluronic acid and metal salts (FeSO4, ZnSO4, CuSO4 and MgSO4). We found that the commercial strain of P. hermaphrodita responded poorly to snail mucus compared to wild isolated strains, and C. aspersum collected from different parts of the UK differed in their attractiveness to the nematodes. We found that Phasmarhabditis nematodes were weakly attracted to all metals tested but were strongly attracted to hyaluronic acid. In a final experiment we also showed that pharmacological manipulation of cyclic guanosine monophosphate (cGMP) increased chemoattraction to snail mucus, suggesting that the protein kinase EGL-4 may be responsible for Phasmarhabditis sp. chemoattraction.
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Development of Phasmarhabditis hermaphrodita (and members of the Phasmarhabditis genus) as new genetic model nematodes to study the genetic basis of parasitism. J Helminthol 2018; 93:319-331. [PMID: 29607798 DOI: 10.1017/s0022149x18000305] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The genetic mechanisms of how free-living nematodes evolved into parasites are unknown. Current genetic model nematodes (e.g. Caenorhabditis elegans) are not well suited to provide the answer, and mammalian parasites are expensive and logistically difficult to maintain. Here we propose the terrestrial gastropod parasite Phasmarhabditis hermaphrodita as a new alternative to study the evolution of parasitism, and outline the methodology of how to keep P. hermaphrodita in the lab for genetic experiments. We show that P. hermaphrodita (and several other Phasmarhabditis species) are easy to isolate and identify from slugs and snails from around the UK. We outline how to make isogenic lines using 'semi-natural' conditions to reduce in-lab evolution, and how to optimize growth using nematode growth media (NGM) agar and naturally isolated bacteria. We show that P. hermaphrodita is amenable to forward genetics and that unc and sma mutants can be generated using formaldehyde mutagenesis. We also detail the procedures needed to carry out genetic crosses. Furthermore, we show natural variation within our Phasmarhabditis collection, with isolates displaying differences in survival when exposed to high temperatures and pH, which facilitates micro and macro evolutionary studies. In summary, we believe that this genetically amenable parasite that shares many attributes with C. elegans as well as being in Clade 5, which contains many animal, plant and arthropod parasites, could be an excellent model to understand the genetic basis of parasitism in the Nematoda.
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Morris A, Green M, Martin H, Crossland K, Swaney WT, Williamson SM, Rae R. A nematode that can manipulate the behaviour of slugs. Behav Processes 2018; 151:73-80. [PMID: 29499346 DOI: 10.1016/j.beproc.2018.02.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 02/20/2018] [Accepted: 02/26/2018] [Indexed: 11/18/2022]
Abstract
The ability of parasites to manipulate the behaviour of their hosts has evolved multiple times, and has a clear fitness benefit to the parasite in terms of facilitating growth, reproduction and transfer to suitable hosts. The mechanisms by which these behavioural changes are induced are poorly understood, but in many cases parasite manipulation of serotonergic signalling in the host brain is implicated. Here we report that Phasmarhabditis hermaphrodita, a parasite of terrestrial gastropod molluscs, can alter the behaviour of slugs. Uninfected slugs (Deroceras panormitanum, Arion subfuscus and Arion hortensis) avoid areas where P. hermaphrodita is present, but slugs infected with P. hermaphrodita are more likely to be found where the nematodes are present. This ability is specific to P. hermaphrodita and other nematodes (Steinernema carpocapsae and Heterorhabditis bacteriophora) do not induce this behavioural change. To investigate how P. hermaphrodita changes slug behaviour we exposed slugs to fluoxetine (a selective serotonin reuptake inhibitor) and cyproheptadine (a serotonin receptor antagonist). Uninfected slugs fed fluoxetine no longer avoided areas where P. hermaphrodita was present; and conversely, infected slugs fed cyproheptadine showed no increased attraction to areas with nematodes. These findings suggest that a possible mechanism by which P. hermaphrodita is able to manipulate parasite avoidance behaviour in host slugs is by manipulating serotonergic signalling in the brain, and that increased serotonin levels are potentially associated with a reduction in parasite avoidance.
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Affiliation(s)
- Alex Morris
- Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom
| | - Michael Green
- Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom
| | - Hayley Martin
- Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom
| | - Katie Crossland
- Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom
| | - William T Swaney
- Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom
| | - Sally M Williamson
- Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom
| | - Robbie Rae
- Liverpool John Moores University, School of Natural Sciences and Psychology, Byrom Street, L33AF, United Kingdom.
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