Température stable et température fluctuante. I. Etude comparative de leurs effets sur le développement de certaines Planaires

Summary

The temperatures were a constant 10 °C level on the one hand, and a 24 h pattern varying rhythmically between 5 and 15 °C on the other hand. The Triclads were the two closely related limnophilic species Polycelis nigra and P. tenuis.

The effect of the two temperature regimes depends on the species considered. When compared with the 10 °C constant level, fluctuations accelerated the development in P. nigra. In P. tenuis the duration of egg development remained unchanged but the maturation and generation times were significantly lengthened by these fluctuations. Considering cocoon development, the computation of expected times determined from the hourly proportion of development occuring at 5, 10 and 15 °C constant levels gives a better approximation of times observed under fluctuating conditions than does the consideration of the development time for the sole mean level of 10 °C.

If confirmed by new experiments under different temperature regimes, these results ought to provide a contribution to the mutual interpretation of laboratory and field data on the effects of temperature.