Abstract
We report here the effects of temperature on the p1 neuromuscular system of the stomatogastric system of the lobster (Panulirus interruptus). Muscle force generation, in response to both the spontaneously rhythmic in vitro pyloric network neural activity and direct, controlled motor nerve stimulation, dramatically decreased as temperature increased, sufficiently that stomach movements would very unlikely be maintained at warm temperatures. However, animals fed in warm tanks showed statistically identical food digestion to those in cold tanks. Applying dopamine, a circulating hormone in crustacea, increased muscle force production at all temperatures and abolished neuromuscular system temperature dependence. Modulation may thus exist not only to increase the diversity of produced behaviors, but also to maintain individual behaviors when environmental conditions (such as temperature) vary.
Highlights
Ectotherms have lower energy requirements than endotherms because they do not actively maintain a constant body temperature
This phase change was significant (p = 0.023, Student’s paired ttest), it was much smaller than the shift expected if Lateral Pyloric (LP) neuron firing delay after PD neuron burst beginning had not shortened as temperature increased
Not as perfect as that observed in Cancer, lobster pyloric networks showed substantial phase compensation as temperature changed
Summary
Ectotherms have lower energy requirements than endotherms because they do not actively maintain a constant body temperature. In the crayfish Orconectes limosus, contraction force in response to muscle depolarization by current injection increases with warming [8], whereas in the crayfish Astacus leptodactylus force induced by motor neuron stimulation decreases with warming [2,3,4]. These data were mostly obtained in leg muscles. This temperature sensitivity in other crustacean muscles prompted us to test whether pyloric neuromuscular function, and stomach activity, may not be maintained as animal temperature changes, even if correctly-phased pyloric network rhythmic activity is
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