Stochasticity Accelerates Nematode Egg Development

Abstract

Day-degrees models of nematode development assume that temperature stochasticity has no effect on the development rate of infective stages as long as the mean temperature is held constant. This assumption was tested in this study. Unembryonated Heterakis gallinarum eggs were subjected to nocturnal and diurnal daily temperature cycles at 12 and 17 C. respectively, and embryonation was compared with eggs subjected to similar stochastic daily cycles, in which random normal variations in the temperature were added to the 2 temperatures. The prediction that there is no effect of stochasticity was refuted. Embryonation of eggs subjected to variable daily cycles occurred significantly earlier than that of eggs subjected to deterministic daily cycles, suggesting that stochastic variation in temperature accelerated embryonation even though mean temperatures were the same. These findings show that the development time of H. gallnarum eggs is decreased by stochastic variation in temperature, which may have important implications for the effects of climate change on parasite availability.

Broad-Scale Assessment of Rangeland Health, Grand Staircase–Escalante National Monument, USA

“…This disease is important in domestic fowl and game bird farms (Bergstrom 1982). Because development of H. gallinarum can be influenced by temperature fluctuations, fluctuations in parasite abundance could be linked with weather conditions (Saunders et al 2002). The documentation of cecal worms in greater sage-grouse suggests the possibility of exposure to H. meleagridis, however the documentation cited by consisted solely of a personal communication with an investigator that identified H. gallinae in a single greater sage-grouse specimen.…”

Bionomics of Larvae of Parelaphostrongylus Odocoilei (Nematoda: Protostrongylidae) in Experimentally Infected Gastropod Intermediate Hosts

“…At or below To, development from LI to L2 occurred for U. pallikuukensis (Kutz, 2000), but not E. rangiferi (Halvorsen and Skorping, 1982). It is possible that stochastic variation in temperature may trigger development from LI to L2 when temperatures briefly reach or exceed a critical threshold (Saunders et al, 2002). Alternatively, the threshold temperature for development from LI to L2 may be lower than that for L2 to L3.…”

“…However, an exponential or power relationship cannot be excluded, and larval development at cooler temperatures may be faster than predicted by the linear model (Saunders et al 2002); it is not known whether the amount of development that occurs at or below threshold temperature is biologically significant. For this reason, and in light of the possibility of biological differences in P. odocoilei across its broad geographic range, the DD model needs to be validated using observations of larval development in the field before it can be broadly applied ( …”

“…Degree-day (DD) models, which describe the amount of heating above a critical threshold temperature, are widely used to determine conditions allowing parasite development and can be incorporated into deterministic, predictive models for rates of parasite development under different climatic conditions (Campbell et al, 1974;Harvell et al, 2002;Saunders et al, 2002). Early workers began to examine the effects of weather and climate on parasite transmission (Levine, 1963), but "this became a neglected and low prestige area over the last 2 decades as our ability to study the ... more molecularly glamorous aspects of the parasite life-cycle increased" (Smith et al, 1995).…”

Optic tectum morphogenesis: A step‐by‐step model based on the temporal–spatial organization of the cell proliferation. Significance of deterministic and stochastic components subsumed in the spatial organization

“…This study also presents a biomathematical approach that could provide a conceptual framework to analyze a recurrent and controversial point in developmental biology: the problem about ''determinism'' and ''stochasticity'' and their possible role in developing organisms (Bronk et al, 1968;Saunders et al, 2002;Meng et al, 2004;Song et al, 2006;Raj et al, 2010;Zernicka-Goetz and Huang, 2010;Wu et al, 2011).…”