Vascular peripheral resistance and compliance in the lobster Homarus americanus

Area of Science:

• Cardiovascular Physiology
• Comparative Anatomy
• Biomechanical Engineering

Background:

• Understanding hemolymph flow in crustaceans is crucial for physiological studies.
• The mechanical properties of arteries influence circulatory system efficiency.
• Lobster circulatory system presents a unique model for studying vascular dynamics.

Purpose of the Study:

• To measure and compare peripheral resistance and mechanical properties of arteries in the lobster.
• To investigate the relationship between artery radius, flow rate, and resistance.
• To analyze the functional implications of arterial structure on hemolymph circulation.

Main Methods:

• Measurement of peripheral resistance in arterial beds.
• Assessment of mechanical properties (compliance, stiffness) of seven major arteries.
• Comparison of resistance and mechanical properties across different arterial pathways.
• Analysis of arterial wall structure, including fibril layers and muscle presence.

Main Results:

• Vascular resistance is inversely proportional to artery radius and decreases non-linearly with increasing flow rate.
• The hepatic arterial system exhibits lower resistance than predicted by radius alone.
• Arteries are compliant at physiological pressures but stiffen at higher pressures and radii.
• The dorsal abdominal artery contains striated muscle and maintains compliance across expected hemolymph pressures.
• Total vascular resistance at in vivo flow rates is approximately 1.93 kPa s ml-1.

Conclusions:

• Lobster arteries exhibit varied mechanical properties and resistance patterns.
• Arterial compliance and stiffness are pressure and radius-dependent.
• The dorsal abdominal artery may play an active role in flow regulation.
• All arteries likely function as Windkessels, damping pulsatile flow and pressure.