GUADAGNOLI, Jutta A.*; REIBER, Carl L.*: Hemodynamics of the grass shrimp P. Pugio under normoxic and hypoxic conditions

We investigated the hemodynamics of the of the grass shrimp Palaemonetes pugio under normoxic and hypoxic conditions. In many larger decapod crustaceans such as crayfish, crabs and lobsters, exposure to progressive hypoxia results in a decrease in heart rate with a concomitant increase in stroke volume. However, the grass shrimp responds in the opposite manner with an increase in heart rate and a decrease in stroke volume. During hypoxic exposure animals may redirect hemolymph flow through the seven arteries leaving the heart. We first developed a hemolymph flow profiles of the grass shrimp under normoxic conditions (Po₂ 20 Kpa). Using videomicroscopy and dimensional analysis, heart rate, stroke volume and cardiac output were determined. Shrimp were injected with methelyne blue to determine hemolymph velocity. Velocity along with vessel diameters, were then used to calculate flow through each of the vessels. These flows were summed and compared to the results of dimensional analysis of cardiac output. Under normoxic conditions cardiac output was distributed as follows: anterior aorta 17%; anterior laterals 36%; posterior aorta 13%; hepatic arteries 4% and sternal artery 30%. The same parameters were then measured during hypoxic exposure (13.3 KPa, 5.3 KPa and 2.7 KPa). Flows through the vessels changed in order maintain adequate O₂ delivery to the anterior portion of the animal and the ventral nerve cord.