Regulation of blood pressure in the land crab Cardisoma guanhumi

Area of Science:

• Crustacean physiology
• Cardiovascular regulation in invertebrates
• Comparative physiology

Background:

• The land crab Cardisoma guanhumi exhibits unique physiological adaptations to its terrestrial environment.
• Understanding cardiovascular responses to blood volume changes is crucial for invertebrate physiology.

Purpose of the Study:

• To investigate the cardiovascular and muscular responses to acute and chronic blood volume alterations in Cardisoma guanhumi.
• To elucidate the role of cardioregulatory nerves in mediating these responses.

Main Methods:

• Monitoring cardiovascular parameters including heart rate (fH) and hemolymph pressure.
• Measuring activity of dorsoventral muscles (DVMs) and epimeral attractor muscles (EAMs).
• Surgical denervation of cardioregulatory nerves to assess neural influence.

Main Results:

• Acute blood volume reduction increased DVM and EAM activity, leading to bradycardia and decreased hemolymph pressure.
• Blood volume expansion reciprocally affected DVM and EAM activity but not heart rate.
• After nerve cutting, hypovolemia did not affect fH but increased DVM activity.
• Dehydration-induced blood volume reduction increased DVM activity while maintaining fH and hemolymph pressure.

Conclusions:

• Cardiovascular responses to blood volume changes in Cardisoma guanhumi involve complex interactions between muscle activity and neural control.
• DVM activity plays a significant role in regulating cardiovascular function during hypovolemia, potentially independent of direct neural control.
• The findings provide insights into the physiological mechanisms underlying volume homeostasis in crustaceans.