Hostname: page-component-78c5997874-m6dg7 Total loading time: 0 Render date: 2024-11-15T07:39:54.964Z Has data issue: false hasContentIssue false
  • English
  • Français

Response of Haemonchus contortus cayugensis to a change in the ratio of smooth to linguiform

Published online by Cambridge University Press:  06 April 2009

L. F. Le Jambre  and
L. H. Ractliffe
L. F. Le Jambre
Affiliation:
Division of Animal Health, C.S.I.R.O., Pastoral Research Laboratory, Armidale, N.S.W., 2350, Australia
L. H. Ractliffe
Affiliation:
Division of Animal Health, C.S.I.R.O., Pastoral Research Laboratory, Armidale, N.S.W., 2350, Australia
Get access Rights & Permissions [Opens in a new window]

Extract

The equilibrium, of vulvar phenotypes in Haemonchus contortus cayugensis was changed by infecting lambs with either a selected strain of smooth or of linguiform worms. Subsequently the lambs grazed the same pasture and observations were made on changes in worm populations in the lambs, and on pasture it appeared that the seasonal change in the relative frequencies of A and B linguiform worms was related to density-dependent factors in the host. In the spring, when lambs first become infected, the worm population is small and the majority of linguiform worms are A-type. As the season progresses the density of the parasite population increases. Once the population becomes crowded selection begins to favour the B-type females. The effects of crowding on linguiform A females can be seen as a positive correlation between the percentage of linguiform A and their weight. Population density also affected the survival of A-type worms since there was a negative correlation of percentage A-type on total worm numbers. There was a similar negative correlation between percentage A-type and total worm numbers in both the continuously infected and tracer lambs.

Population density did not affect the proportion of smooth worms. However, smooth worms increased in the tracers from, approximately 10% at the beginning of the experiment to 55% at its conclusion 18 weeks later. The latter percentage is almost within range of the local subspecies, which has 60% or more smooth worms. It appears therefore that the proportion of smooth to linguiform worms is a stable equilibrium maintained by natural selection.

Type
Research Article
Information
Parasitology , Volume 73 , Issue 2 , October 1976 , pp. 213 - 222
Copyright
Copyright © Cambridge University Press 1976

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Bliss, C. I. (1967). Statistics in Biology, vol. I. New York: McGraw-Hill Company.Google Scholar
Das, K. M. & Whilock, J. H. (1960). Subspecifiation in Haemonchus contortus (Rudolphi, 1803), Nema, Trichostrongyloidae. Cornell Veterinarian 50, 182–97.Google Scholar
Georgi, J. R. (1974). Parasitology for Veterinarians, 2nd ed. Philadelphia: W. B. Saunders.Google Scholar
Le Jambre, L. F. (1971). The adaptiveness of polymorphism in Haemonchus contortus. Ph.D. Thesis, Cornell University, N.Y. 14850.Google Scholar
Le Jambre, L. F. (1976). Genetics of vulvar morph types in Haemonchus contortus. I. Haemonchus contortus cayugensis from the Finger Lakes Region of New York. Submitted to International Journal of Parasitology.Google Scholar
Le Jambre, L. F. & Ractliffe, L. H. (1971). Seasonal change in a balanced polymorphism in Haemonchus contortus populations. Parasitology 62, 151–6.CrossRefGoogle Scholar
Le Jambre, L. F. & Whitlock, J. H. (1968). Seasonal fluctuation in linguiform morphs of Haemonchus contortus cayugensis. Journal of Parasitology 54, 827–30.CrossRefGoogle Scholar
Le Jambre, L. F. & Whitlock, J. H. (1973). Optimum temperature for egg development of phenotypes in Haemonchus contortus cayugensis as determined by Arrhenius diagrams and Sacher's entropy function. International Journal of Parasitology 3, 299–310.CrossRefGoogle Scholar
Le Jambre, L. F, Dash, K. M, Southcott, W. H. & Donnelly, J. B. (1976). Density dependence of linguiform morph types in Haemonchus contortus. (In preparation.)Google Scholar
Le Jambre, L. F, Ractliffe, L. H, Uhazy, L. S. & Whitlock, J. H. (1972). Evidence that the seasonal polymorphism apparent in linguiform Haemonchus contortus cayugensis also occurs in the other phenotypes. International Journal for Parasitology 2, 171–3.CrossRefGoogle Scholar
Li, C. C. (1966). Population Genetics, 5th ed. University of Chicago Press.Google Scholar
Michel, J. F. (1970). The regulation of populations of Ostertagia ostertagi in calves. Parasitology 61, 435–47.CrossRefGoogle ScholarPubMed
Ractliffe, L. H, Le Jambre, L. F, Uhazy, L. S. & Whitlock, J. H. (1971). Density dependence of the weight of Haemonchus contortrus adults. International Journal for Parasitology 1, 297–301.CrossRefGoogle ScholarPubMed
Whitlock, J. J. (1962). Bionics and experimental epidemiology. In Biological Prototypes and Synthetic Systems, vol. I, pp. 39–48. New York: Plenum Press.CrossRefGoogle Scholar