Abstract
We have used high energy-resolution neutron scattering to probe nanoscale dynamic processes in living millipedes (Narceus americanus). We have measured the temperature dependence of the intensity of scattered neutrons that do not exchange energy with the living samples on the 1.5 ns time scale, thereby excluding the signal from the highly mobile intra- and extra-cellular bulk-like aqueous constituents in the sample. This measured “elastic” scattering intensity exhibits a non-monotonic temperature dependence, with a noticeable systematic decrease detected between 295 and 303 K on warming up from 283 to 310 K. This decrease demonstrates an excellent inverse correlation with the non-monotonic, as a function of temperature, increase in the slow diffusivity previously observed in planarian flatworms and housefly larvae. This correlation suggests the existence of a biological mechanism, possibly common between different classes (Insects and Myriapods) and even phyla (Arthropods and Platyhelminthes), that dampens the slow nanoscopic dynamics in ectothermic organisms in response to the temperature of the environment exceeding the physiologically optimal range.
Highlights
Ectothermic animals are critically dependent on their environment to sustain the body temperature within the physiological range
In search of possible microscopic mechanisms underpinning the whole-body response of ectotherms to changing environment temperature, we have turned to high energy-resolution quasielastic neutron scattering measurements[3,4]
Because stiff chitin much differs in its dynamic response from soft tissues, we find that its presence introduces an additional component to the scattering signal and necessitates modification to the data collection and analysis procedure
Summary
Ectothermic animals are critically dependent on their environment to sustain the body temperature within the physiological range. The Q dependence of the higher-E data presented in Fig. 4 suggests that the signal from the millipedes in the higher energy transfer region is dominated by scattering from the bulk-like aqueous constituents in the sample.
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