Abstract
The effect of acute and chronic cold exposure on heart rate (HR) and neuronal function in crayfish Procambarus clarkii and prawns Macrobrachium rosenbergii was addressed. This is particularly important since prawn farms of this species are used for aquaculture in varied climates world wide. The success of P. clarkii as an invasive species throughout the world may in part be due to their ability to acclimate to cold and warm habitats. A set of experiments was devised to address the physiological abilities of these species in managing rapid changes to cold environments as well as their ability to respond to sensory stimuli by using behavior and a bioindex of HR. Prawns died within 2 hrs when moved from 21℃ to 5℃. Crayfish reduced their HR but survived for at least a week with this rapid change. Changes in temperature of 5℃ each week resulted in death of the prawns when 10℃ was reached. Some died at 16℃ and some lasted at 10℃ for 1 day before dying. Crayfish remained responsive to sensory stimuli and survived with either rapid or slow changes in temperature from 21℃ to 5℃. Primary sensory neurons were rapidly inhibited in prawns with an acute change to 5℃, where as in crayfish the activity was reduced but not completely inhibited. An induced sensory-CNS-motor circuit elicited activity at neuromuscular junctions in prawns and crayfish at 21℃ but with acute changes to 5℃only in crayfish was the circuit functionally intact. The ability to survive rapid environmental temperature changes will impact survival and in time the distribution of a species. The significance of these findings is that they may account, in part, for the wide ecological distribution of P. clarkii as compared to M. rosenbergii. The invasiveness of organisms, as for P. clarkii, is likely linked to the physiological robustness to acute and chronic temperature changes of habitats.
Highlights
Animals that are conformers to the environment, such as many invertebrates, face physiological and behavioral tasks to survive in extreme environments
Sometimes the heart rate (HR) may first slow down and will increase upon an initial shock of colder temperature just in the case of a physical disturbance (Figure 4). Such biphasic responses have been noted in earlier studies for HR as well as ventilatory rate (VR) [7,8,28,29] for environmental disturbances when animals were held at 21 ̊C
This study demonstrated that the crayfish species Procambarus clarkii is very resilient to surviving acute as well as chronic exposure to cold environments as compared to the prawn species Macrobrachium rosenbergii
Summary
Animals that are conformers to the environment, such as many invertebrates, face physiological and behavioral tasks to survive in extreme environments. The ability of the crayfish Procambarus clarkii and the prawn Macrobrachium rosenbergii to acclimate to rapid and gradual exposure of cold environments was addressed in this study. Both species have economic and ecological concerns such that they are both used for human food consumption in places outside their native habitats. The desire to rear crustacean species for food sources in different environments comes at a cost in managing the environment in which the animals are raised. An outdoor or a regulated environment for rearing these animals drives the economic feasibility of growing them as a food source. The temperature for transportation is of concern when there is a strong susceptibility to rapid temperature changes
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