Meeting Abstract

P1.114  Saturday, Jan. 4 15:30  Does the ventilatory pump affect the gill circulation in blue crabs and lobsters? JORGENSEN, D.; ENGLAND, M.*; HENSLEY, S.; BRINGS, V.; Roanoke College mgengland@mail.roanoke.edu

Blue crabs and lobsters carry out gas exchange with two sets of gills each housed in a branchial chamber (BC) located on either side of the thorax. The BCs are each ventilated by the action of a scaphognathite (Sc), which generates a suction pressure in its BC that pulls water past its gill set. During periods of increased oxygen demand, Sc activity increases, resulting in greater suction pressure in the BC driving increased ventilation. The gills in both animals are invested with small diameter hemolymph channels that bring hemolymph into close contact with the ventilatory water. A heart contracts rhythmically, pushing hemolymph through the circulatory system including the gill circuits. We are interested in the relationship between gill circuit perfusion and the hydrostatic pressure environment in the BC. We measured hydrostatic pressure in the BCs concurrently with hemolymph pressure in spaces just up- and downstream from the gill circulation to determine hemolymph pressure drop (&deltaP) across the gill circuit (a measure of hemolymph flow resistance). In some experiments, we concurrently measured hemolymph velocity in an afferent gill hemolymph vessel. We challenged the animals by walking them on a submerged treadmill. Our data show that &deltaP decreases by as much as 50% during a period of increased Sc activity. Preliminarily, we found that hemolymph velocity in an afferent gill vessel increases concurrently by as much as 2X. These data suggest that increased Sc activity may cause passive dilatation of gill vessels and assist the heart in moving hemolymph through the gill circulation during periods of higher metabolic demand.