AN ASSESSMENT OF THE RELEVANCE OF THERMAL TIME RELATIONSHIPS TO NEMATOLOGY

The requirements and problems of conducting thermal time studies are d iscussed and the utility of fitting a linear relationship between temp erature and rates of nematode embryogenesis and development is reviewe d. Published data on durations of development at different temperature s, for a range of nematodes including animal parasitic species, are co nverted to rates of development and base temperatures (T-b) and therma l constants (S, expressed as degrees C day requirements above T-b) are estimated. New data on the minimum requirements for embryogenesis in Meloidogyne javanica are compared with the minimum requirements for a complete life cycle. The ecological significance of differences in the value of T-b and S are considered and it is proposed that, for compar able species (M. hapla and M. javanica), as the value of T-b increases so the value of S decreases.