Phasmarhabditis hermaphrodita

Phasmarhabditis hermaphrodita
Scientific classification
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Order: Rhabditida
Family: Rhabditidae
Subfamily: Peloderinae[1]
Genus: Phasmarhabditis
Species: P. hermaphrodita
Binomial name
Phasmarhabditis hermaphrodita
(A. Schneider, 1859)

Phasmarhabditis hermaphrodita is a microscopic nematode in the family Rhabditidae. It is a lethal parasite of the slug, Deroceras reticulatum and a large number of other slug species from the families Milacidae, Limacidae and Arionidae.[2] It is used as a molluscicide for the biological control of these pests.[3]

Description

Phasmarhabditis hermaphrodita can be detected and quantificated from soil samples by quantitative PCR.[4] This method can also be used to distinguish it from the morphologically similar Phasmarhabditis neopapillosa.[4]

Slug pest Deroceras reticulatum is one of the host species for Phasmarhabditis hermaphrodita

Life cycle

Under natural conditions, infective juveniles of this species are found in the soil. They represent a stage in the development of the nematode which is specially adapted for survival in this unfavorable environment and while there, bacteria colonize their gut.[5] The juveniles actively search for potential slug hosts. When these are found, the nematodes enter through the breathing pore (pneumostome) below the mantle and move to the shell cavity.[6] Here the bacteria are released and start multiplying and the nematodes feed on them and resume their growth.[5] The bacteria cause septicaemia in the slug which develops a characteristic swelling of the mantle area and there is a marked reduction in its feeding activity.[7] After between four and twenty one days, depending on the number of parasites and the temperature, the slug dies. The nematodes need several days to complete their life cycle and seem to be able to modify the host's behaviour so that it remains below the ground surface before death and is thus not readily available to predators and scavengers.[8] The nematodes eat the cadaver and produce another generation of infective juveniles which move off through the soil in search of new slug hosts.[5][6]

Biological control of slugs

Phasmarhabditis hermaphrodita can be used in organic farming instead of poisonous metaldehyde or carbamates.[9]

This nematode is commercially reared in a culture with the bacterium Moraxella osloensis and sold as a biological molluscicide.[10] The culture is mixed with water and applied as a drench to the surface of the soil. This is best done at a soil temperature of about 15 °C, with a minimum of 5 °C and a maximum of 20 °C. The soil should be kept damp afterwards. Young seedlings and cuttings can best be protected by applying the nematodes one week in advance of sowing or planting. The protection is expected to last for at least six weeks.[10] Because infection of the slug reduces its feeding activities, crop protection is rapid even before host mortality occurs.[3]

It has been shown that when released, new generations of nematodes do not continue their symbiosis with Moraxella osloensis but associate with a complex and variable mixture of other bacteria while still retaining their virulence.[11]

In a study by Speiser et al. (2001),[9] Phasmarhabditis hermaphrodita had little effect on larger specimen of Spanish slugs.[9]

References

  1. ↑ Nguyen, K. B. (3 March 2006). "SUBORDER RHABDITINA". Entomology & Nematology Department, University of Florida. Retrieved 7 December 2010.
  2. ↑ Wilson, M. J.; Glen, D. M.; George, S. K. (1993). "The rhabditid nematode Phasmarhabditis hermaphrodita as a potential biological control agent for slugs". Biocontrol Science and Technology. 3 (4): 503–511. doi:10.1080/09583159309355306.
  3. 1 2 "Pest Control Biological Control of Slugs Using the Slug Parasite Nematode Phasmarhabditis hermaphrodita". University of Aberdeen. Retrieved 7 December 2010.
  4. 1 2 MacMillan, K. (2006). "Quantification of the slug parasitic nematode Phasmarhabditis hermaphrodita from soil samples using real time qPCR". International Journal for Parasitology. 36 (14): 1453–1461. doi:10.1016/j.ijpara.2006.08.005. PMID 17010977.
  5. 1 2 3 An, R.; Sreevatsan, S. & Grewal, P. S. (2008). "Moraxella osloensis Gene Expression in the Slug Host Deroceras reticulatum". BMC Microbiology. 8: 19. doi:10.1186/1471-2180-8-19.
  6. 1 2 Tan, L. & Grewal, P. S. (2001). "Infection behaviour of the Rhabditid Nematode Phasmarhabditis hermaphrodita to the grey garden slug Deroceras reticulatum". Journal of Parasitology. 87 (6): 1349–1354. doi:10.1645/0022-3395(2001)087[1349:IBOTRN]2.0.CO;2.
  7. ↑ Glen, D. M.; Wilson, M. J.; Brain, P. & Stroud, G. (2000). "Feeding activity and survival of slugs, Deroceras reticulatum, exposed to the rhabditid nematode, Phasmarhabditis hermaphrodita: a model of dose response". Biological Control. 17 (1): 73–81. doi:10.1006/bcon.1999.0778.
  8. ↑ Pechova, H. & Foltan, P. (2008). "The parasitic nematode Phasmarhabditis hermaphrodita defends its slug host from being predated or scavenged by manipulating host spatial behaviour". Behavioural Processes. 78 (3): 416–420. doi:10.1016/j.beproc.2008.02.011.
  9. 1 2 3 Speiser, B.; Zaller, J. G.; Neudecker, A. (2001). "Size-specific susceptibility of the pest slugs Deroceras reticulatum and Arion lusitanicus to the nematode biocontrol agent Phasmarhabditis hermaphrodita". BioControl. 46 (3): 311–320. doi:10.1023/A:1011469730322.
  10. 1 2 "Phasmarhabditis-System product information". Retrieved 7 December 2010.
  11. ↑ Rae, R. G.; Tourna, M. & Wilson, J. M. (2010). "The slug parasitic nematode Phasmarhabditis hermaphrodita associates with complex and variable bacterial assemblages that do not affect its virulence". Journal of Invertebrate Pathology. 104 (3): 222–226. doi:10.1016/j.jip.2010.04.008.

Further reading

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