Biodiversity and Biosystematics - Novel Techniques in Biosystematics

The secure identification of parasites may be problematical and yet is of prime importance, particularly where closely related forms show different pathological effects on hosts. A case in point is that of the notifiable monogenean G. salaris which has decimated wild Norwegian salmon stocks and has spread across Europe. The Gyrodactylus species that occur on salmonids are very difficult to discriminate from each other. Research within the Parasitology Group has developed two semi-automatic classification systems for the rapid identification of G. salaris, from closely related species parasitising British salmonids. The first system uses a combination of novel specimen preparation and image-analysis to produce high quality point-to-point morphometric data suitable for the differentiation of species using a range of advanced statistical classification techniques including neural networks. The second system automates the procedure further, eliminating human error, to produce an outline of the attachment hooks which are then summarised by the application of shape descriptors to it.

The data are then fed automatically into a statistical classifier trained to discriminate selected species. The software for these systems which are now in operation by government health diagnosticians and will assist inspectors in the differential diagnosis of species that parasitise salmonids and aid in the early detection of G. salaris.

Imaging software developed within the Group allows for the semi-automated analysis of a wide range of biological material processed from live material or from images grabbed using the light, SEM, TEM and confocal microscope. Programmes including the enumeration of fish eggs, rotifers, the imaging of specific cell structures within whole mounts such as sensilla, and the quantification of larger monogeneans such as Benedenia seriolae and Zeuxapta seriolae, common parasites of yellowtail kingfish. The BEAST (Benedeniid Enumeration and Segmentation Techniques) software, which has been developed for the Australian government, enables users to perform a range of operations on a single image field of monogeneans including counting individuals and measuring a range of morphometric parameters, which will inform farm management and control strategies.

Selected References

  1. Bakke, T.A., Nilsen, K.B. & Shinn, A.P. (2004) The application of chaetotaxy to discriminate between Norwegian Gyrodactylus salaris Malmberg, 1957 clades and related species from salmonids. Folia Parasitologica, 51, 253-261.
  2. Shinn, A.P., Sommerville, C., Bron, J .E. & Gibson, D.I. (2003) Notes on the mechanism of attachment in species of the genus Gyrodactylus Nordmann, 1832. Invertebrate Biology, 122, 1-11.
  3. Bell, A.S., Sommerville, C. & Gibson, D.I. (2002) Multivariate analyses of morphometric features from Apatemon gracilis (Rudolphi, 1819) and A. annuligerum (v. Nordmann, 1832) (Digenea: Strigeidae) metacercariae. Systematic Parasitology, 51, 121-133.
  4. Shinn, A.P., Gibson, D.I. & Sommerville, C. (2001) The discrimination of Gyrodactylus salaris from species of Gyrodactylus parasitising British salmonids using novel morphometric parameters. A scanning electron microscopy study. Journal of Fish Diseases, 24, 83-97.
  5. Shinn, A.P., Kay, J.W. & Sommerville, C. (2000) The use of statistical classifiers for the discrimination of species of the genus Gyrodactylus (Monogenea) parasitising salmonids. Parasitology, 120, 1-9.
  6. Kay, J.W., Shinn, A.P. & Sommerville, C. (1999) Towards an automated system for the identification of notifiable pathogens. Parasitology Today, 15 (5), 201-206.
  7. Gaze, W.H. & Wootten, R. (1999) An SEM study of adhesive disc skeletal structures isolated from trichodinids (Ciliophora : Peritichida) of the genera Trichodina Ehrenberg, 1838 and Paratrichodina Lom, 1963. Systematic Parasitology, 43, 167-174.
  8. Bell, A.S., Sommerville, C. & Gibson, D.I. (1998) Karyological studies on three strigeid digeneans Ichthyocotylurus erraticus (Rudolphi, 1809), I. variegatus (Creplin, 1825) and Apatemon gracilis (Rudolphi, 1819). Systematic Parasitology, 41, 169–178.
  9. Shinn, A.P., Gibson, D.I. & Sommerville, C. (1998) Chaetotaxy of members of the Gyrodactylidae (Monogenea), with comments upon their systemic relationships with the Monopisthocotylea and Polypisthocotylea. Systematic Parasitology, 39, 81–94.
  10. Shinn, A.P., Sommerville, C. & Gibson, D.I. (1998) The application of chaetotaxy in the discrimination of Gyrodactylus salaris Malmberg, 1957 (Gyrodactylidae: Monogenea) from species of the genus parasitising British salmonids. International Journal of Parasitology, 28, 805–814.
  11. Shinn, A.P., Sommerville, C. & Gibson, D.I. (1997) Argentophilic structures as a diagnostic criterion for the discrimination of species of the genus Gyrodactylus von Nordmann (Monogenea). Systematic Parasitology, 37, 47-57.
  12. Bell, A.S., Gibson, D.I. & Sommerville, C. (1997) Chaetotaxy and surface structures of the miracidia of Ichthyocotylurus erraticus (Rudolphi, 1809), L. variegatus (Creplin, (1825) and Apatemon gracilis (Szidat, 1928) (Digenea, Strigeidae). Systematic Parasitology, 36, 203-212.
  13. Bell, A. S., Gibson, D.I. & Sommerville, C. (1996) Chaetotaxy and armature of Ichthyocotylurus erraticus (Rudolphi, 1809) and Ichthyocotylurus variegatus (Creplin, 1825) cercariae (Digenea, Strigeidae ). Parasitology Research, 83, 70–76.
  14. Shinn, A.P., des Clers, S., Gibson, D.I. & Sommerville, C. (1996) Multivariate analysis of morphometrical features fromGyrodactylus spp. (Monogenea) parasitising British salmonids:Light microscope based studies. Systematic Parasitology, 33, 115- 125.
  15. Shinn, A.P., Gibson, D.I. & Sommerville, C. (1995) A study of the composition of the sclerites of Gyrodactylus Nordmann, 1832 (Monogenea) using X-ray elemental analysis. International Journal of Parasitology, 25, (7), 797-805.
  16. Andrade-Salas, O., Sommerville, C., Wootten, R., Turnbull, T., Melvin, W., Arnezaga, T. & Labus, M. (1993) Immunohistochemical screening and selection of monoclonal antibodies to the salmon louse Lepeophtheirus salmonis (Kroyer, 1837). In: “Pathogens of Wild and Farmed Fish: Sea Lice” Boxshall, G. & Defaye, D. (eds.) Ellis Horwood Ltd., 323-331.
  17. Shinn, A., Gibson, D.I. & Sommerville, C. (1993) An SEM study of the haptoral sclerites of the genus Gyrodactylus Nordmann 1832 (Monogenea) following extraction by digestion and sonication techniques. Systematic Parasitology, 25, 135-144.