Hostname: page-component-cd9895bd7-8ctnn Total loading time: 0 Render date: 2024-12-27T22:41:08.723Z Has data issue: false hasContentIssue false
  • English
  • Français

The relationship between Pseudodiplorchis americanus (Monogenea) density and host resources under controlled environmental conditions

Published online by Cambridge University Press:  06 April 2009

K. Tocque  and
R. C. Tinsley
K. Tocque
Affiliation:
School of Biological Sciences, Queen Mary and Westfield College, University of London, Mile End Road, London El 4NS
R. C. Tinsley
Affiliation:
School of Biological Sciences, Queen Mary and Westfield College, University of London, Mile End Road, London El 4NS
Get access Rights & Permissions [Opens in a new window]

Summary

A previous study has shown that, under natural conditions, energy reserves of the desert toad, Scaphiopus couchii, are negatively related to the density of infection by Pseudodiplorchis americanus. However, this was based predominantly on collections of active animals from breeding congregations and inevitably selected toads which were in good condition. The parasite, a blood-feeding monogenean, occurs in burdens of up to 30 worms/host (mean intensity 6 worms/host) and represents a significant drain on reserves because the host does not feed during a 10-month hibernation. Field studies cannot resolve the possibility that larger worm densities are not observed in nature due to parasite-induced host mortality. The present study was conducted during investigations of P. americanus development and survival under controlled laboratory conditions, utilizing experimentally infected hosts which created worm densities larger than those observed in natural populations. At all temperature regimes, infected animals had smaller fat bodies than those uninfected but differences were generally not statistically significant due to large individual variations, presumably resulting from variations in past feeding efficiency. At cool temperatures (15–20 °C) there was no density-dependent effect on host fat body weight, and at a diurnal temperature cycle of 20–34 °C (simulating that experienced by host and parasite during the summer months), the effects of high temperatures were greater than the effects of infection, due to increased toad metabolic rates. The most significant effects of P. americanus were observed in hosts that began hibernation in relatively poor condition and experienced moderate temperatures (25 °C) during hibernation. The toads generally maintained packed blood cell levels (PCV) levels even when fat body weights were low, but infected animals had a lower PCV irrespective of fat body levels. In animals unfed after field collection, PCV was reduced in uninfected toads and was even lower in infected animals. Although very heavily infected toads (burdens of 35–95 worms/host) were generally in poorer condition than uninfected toads they still survived long-term hibernation under extreme nutritional stress. This study therefore confirmed observations made in field studies that there is a density-dependent relationship between the hosts' survival prospects and P. americanus infection. However, given the large variability in feeding efficiency and stored resources between individual toads, there is no evidence that the most heavily infected toads would have been unrepresented in field samples due to parasite-induced mortality.

Keywords

MonogeneaPseudodiplorchis americanusdensity dependencehost-parasite relationshipsparasite-reduced host condition
Type
Research Article
Information
Parasitology , Volume 108 , Issue 2 , February 1994 , pp. 175 - 183
Copyright
Copyright © Cambridge University Press 1994

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

Adjei, E. L., Barnes, A. & Lester, R. J. G. (1986). A method for estimating possible parasite-related host mortality, illustrated using data from Callitetrarhynchus gracilis (Cestoda: Trypanorhyncha) in lizardfish (Saurida spp.). Parasitology 92, 227–43.CrossRefGoogle Scholar
Anderson, R. M. (1978). The regulation of host population growth by parasitic species. Parasitology 76, 119–57.CrossRefGoogle ScholarPubMed
Anderson, R. M. & May, R. M. (1978). Regulation and stability of host-parasite population interactions. I. Regulatory processes. Journal of Animal Ecology 47, 219–47.CrossRefGoogle Scholar
Bragg, A. N. (1961). A theory of the evolution of the spade footed toads deduced principally from a study of their habits. Animal Behaviour 9, 178–86.CrossRefGoogle Scholar
Dimmitt, M. A. & Ruibal, R. (1980). Exploitation of food resources by Spadefoot Toads (Scaphiopus). Copeia 1980, 854–62.CrossRefGoogle Scholar
Gill, D. E. & Mock, B. A. (1985). Ecological and evolutionary dynamics of parasites: the case of Trypanosoma diemyctyli in the red-spotted newt Notophthalmus viridescens. In Ecology and Genetics of Host-Parasite Interactions (ed. Rollinson, D. & Anderson, R. M.), pp. 157–83. London: Academic Press.Google Scholar
Goater, C. P. & Ward, P. I. (1992). Negative effects of Rhabdias bufonis (Nematoda) on the growth and survival of toads (Bufo bufo). Oecologia 89, 161–5.CrossRefGoogle ScholarPubMed
Hochachka, P. W. & Guppy, M. (1987). Metabolic Arrest and the Control of Biological Time. Cambridge, Mass: Harvard University Press.CrossRefGoogle Scholar
Holmes, J. C. (1982). Impact of infectious disease agents on the population growth and geographical distribution of animals. In Population Biology of Infectious Diseases (ed. Anderson, R. M. & May, R. M.), pp. 37–51. New York: Springer-Verlag.CrossRefGoogle Scholar
Kennedy, C. R. (1987). Long-term stability in the population levels of the eyefluke Tylodelphys podicipina (Digenea: Diplostomatidae) in perch. Journal of Fish Biology 31, 571–81.CrossRefGoogle Scholar
Lester, R. J. G. (1984). A review of methods forestimating mortality due to parasites in wild fish populations. Helgolander Meeresunters 37, 53–64.CrossRefGoogle Scholar
May, R. M. & Anderson, R. M. (1978). Regulation and stability of host-parasite population interactions. II. Destabilising processes. Journal of Animal Ecology 47, 249–67.CrossRefGoogle Scholar
Mayhew, W. W. (1962). Scaphiopus couchi in California's Colorado desert. Herpteologia 18, 153–61.Google Scholar
Mayhew, W. W. (1965). Adaptations of amphibians (Scaphiopus couchi) to desert environments. American Midland Naturalist 74, 95–109.CrossRefGoogle Scholar
McClanahan, L. Jr. (1967). Adaptations of the spadefoot toad Scaphiopus couchi to desert environments. Comparative Biochemistry and Physiology 20, 73–99.CrossRefGoogle Scholar
Seymour, R. S. (1973). Energy metabolism of dormant spadefoot toads. Copeia 1973, 435–45.CrossRefGoogle Scholar
Tinsley, R. C. (1990). The influence of parasite infection on mating success in spadefoot toads, Scaphiopus couchii1. American Zoologist 30, 313–24.CrossRefGoogle Scholar
Tinsley, R. C. & Earle, C. M. (1983). Invasion of vertebrate lungs by the polystomatid monogeneans Pseudodiplorchis americanus and Neodiplorchis scaphiopodis. Parasitology 86, 501–17.CrossRefGoogle Scholar
Tinsley, R. C. & Jackson, H. C. (1988). Pulsed transmission of Pseudodiplorchis americanus (Monogenea) between desert hosts (Scaphiopuscouchii). Parasitology 97, 437–52.CrossRefGoogle Scholar
Tocque, K. (1993). The relationship between parasite burden and host resources in the desert toad (Scaphiopus couchii), under natural environmental conditions. Journal of Animal Ecology 62, 683–93.CrossRefGoogle Scholar
Tocque, K. & Tinsley, R. C. (1991). Influence of desert temperature cycles on the reproductive biology of the monogenean Pseudodiplorchis americanus. Parasitology 103, 111–20.CrossRefGoogle Scholar
Tocque, K. & Tinsley, R. C. (1992). The ingestion of host blood by the monogenean Pseudodiplorchis americanus: a quantitative analysis. Parasitology 104, 283–9.CrossRefGoogle Scholar
Tocque, K. & Tinsley, R. C. (1994). Survival of Pseudodiplorchis americanus (Monogenea) under controlled environmental conditions. Parasitology 108, 185–194.CrossRefGoogle ScholarPubMed