Phasmarhabditis hermaphrodita




Rev 05/25/2021

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Morphology and Anatomy Life Cycle
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        Phasmarhabditis hermaphrodita (Schneider, 1859), Andrassy, 1983
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Morphology and Anatomy:



  • Specimens from slugs often much longer than those from bacterial cultures

  •  Body almost straight when killed by heat, robust, elongate and tapering gradually to the bluntly rounded head end.

  • Lip region about 18 um wide, � flattened anteriorly and continuous with the body contour.

  •  Rounded lips arranged in three pairs: one dorsal, the others sub-ventral.

  • Aphid opening visible on the outer margin of each lateral lip.

  • Stoma rounded-triangular in cross section, its length similar to the lip region width.

  • Pharyngeal collar usually reaching almost to the anterior end of the prominent promesorhabdions

  • Metarhabdions well developed,rounded, isomorphic, each with three minute tubercles.

  • Esopahgus cylindrical, somewhat swollen about half way along its length before suddenly narrowing into the isthmus

  • Isthmus ends in a prominent terminal bulb with the usual prominent rhabditid valvular structure.

  • Excretory pore usually just anterior to the terminal bulb.

  • Nerve ring surrounding the anterior part of the isthmus

  • Tail conical, about three anal body diameters long, tapering to a ?filiform terminus.

  • Cuticle with ? fine transverse and longitudinal striations giving it a tesselated appearance.

  • Lateral ? field usually with four lines but six lines sometimes visible midway between vulva and anus

  • A prominent phasmid visible on each side of the tail about half way along its length.

  • Anus a short, anteriorly curved, transverse slit; rectum somewhat in� ated.

  • Vulva a ventral, elongated, transverse slit about mid way along the body.

  • Reproductive tracts paired and opposed; ovaries reflexed and reaching back almost to the level of the vulva.

  • Sperm often visible in the oviduct although males absent (this species

  •  In mature female/ hermaphrodites, almost round oocytes ?filling much of the body cavity and those nearer the vulva often embryonated.

  • Sometimes hatching of juveniles inside the parent female.



  • Very rare

 Ref: Hooper et al (1999)


Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:


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The nematode was first described as being associated with the slug Arion ater by Schneider in 1859, more than 60 years before the first reference to entomopathogenic nematodes (Steiner, 1923).  Later, Maupas (1900) in a study of nematode development and reproduction established cultures of P. hermaphrodtia (which he called Rhabditis causenelli) that he found as dauer larvae in the intestine of Arion ater.  The cultures were maintained on decaying flesh of slugs (Wilson and Grewal, 2005).



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Biology and Ecology:

Parasite of snails and slugs. The parasite infects slugs in the area beneath the mantle surrounding the shell, causing a disease with characteristic symptoms, particularly swelling of the mantle. Infection leads to death of the slug, usually between seven and 21 days afterwards. The nematode then spreads and multiplies in the cadaver (Wilson et al., 1993).

Phasmarhabditis hermaphrodita is capable of killing several species of slug pests from the genera Deroceras, Arion and Tan-donia (Wilson et al., 1993), as well as snails (Glen & Wilson, 1997).It is markleted by MicroBio Ltd under the trademark Nemaslug� (Glen & Wilson, 1997).

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Life Cycle:

Ecophysiological Parameters:

For Ecophysiological Parameters for this species, click If species level data are not available, click for genus level parameters

Maupas (1900) determined that P. hermaphrodita is a protandrous autogamous hermaphrodite with males occurring very infrequently (1 mmale per 715 females). Maupas did not observe any mating. in a protandrous hermaphrodite, the genital tract first produces sperm that are stored in a spermatheca and then produces oocytes which are fertilized by the stored sperm. The term autogamous recognizes that this is se;f-fertilixation rather than amphimixis.  This mode of reproduction is well-defined for Caenorhabditis elegans.

Wilson and Grewal (2005) considered that there are three life cyvlcle phases:

1. Saprobic: Grewal ad colleagues were able to culture the benatode on bacteria (presunably) decoposing homogenized slugs and slug feces.
2. Necromenic: Dauer stge infective juveniles enter the slug and remain inactive until the slug dies. The nematodes then emerge from the dauer stage and complete their lifecycle while feeding on bacteria decomposing the cadaver. This lifecycle phase was first observed by Maupas (1900) and reported on by Mengert (1953).
3. Parasitic: Dauer larvae enter the slug. The infection leads to death of the slug, usually between seven and 21 days afterwards. The nematode then spreads and multiplies in the cadaver (Wilson et al., 1993).  As of 2021, the cause of death of the slugs is unknown. Is it due to direct activity of the nematodes or to associated bacteria that may be toxic?
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Ecosystem Functions and Services:


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Formulated into a biocontrol agent (Nemaslug and Slugtech) for snails and slugs.

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Glen, D.M. & Wilson, M.J. 1997. Slug-parasitic nematodes as biocontrol agents for slugs. Agro-Food-industry HiTech. 8, 23-27.

Hooper, D J, Wilson, M J, Rowe, J A and Glen, D M. 1999. Some observations on the morphology and protein profiles of the slug- parasitic nematodes, Phasmarhabditis hermaphrodita and P. neopapillosa (Nematoda: Rhabditidae). Nematology, 1: 173�182.

Maupas, E. 1900. Modes et formes de reproduction des nematodes. Archives de Zoologie Experimentale et Generale 7, 563-628.

Mengert, H. 1953. Nematoden und Schnecken. Zeitschrift f�r Morphologie und Okoligie der Tiere 4, 311-349.

RaeP.S.Grewal, J.F Robertson, M. J Wilson. 2007. Biological control of terrestrial molluscs using Phasmarhabditis hermaphroditaa: progress and prospects. Pest Management Science 63:1153-1164.

Steiner, G. 1923. Aplectana kraussei n. sp., eine in der Blattsespe Lyda sp. Parasitierende Nematodenform, nebst Bomerkungen uber das Seitenorgan der parasitischen Nematoden. Zentralblatt f�r Bakteriologie Parasitenkunde Infecktionskankheiten und Hygiene Abteilung I Original 59, 14-18

Wilson, M.J., D.M. Glen, S.K. George. 1993. The rhabditid nematode Phasmarhabditis hermaphrodita as a potential biological control agent for slugs. Biocontrol Science and Technology 3:503-511.

Wilson, M.J. and Grewal, P.S. 2005. Biology, production, and formulation of slug-parasitic nematodes . In: Grewal PS, Ehlers R-U, Shapiro-Ilan DI, editors. Nematodes as Biological Control Agents. CAB International, Wallingford, UK; 2005. p. 421-429.



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Copyright © 1999 by Howard Ferris.
Revised: May 25, 2021.