Meeting Abstract
Lobsters carry out gas exchange with two sets of gills each housed in a branchial chamber (BC) located on either side of the thorax. Each gill set consists of groupings of trichobranchiate gills that extend into the BC from the epipodites of the thoracic appendages. In decapod crustaceans, venous hemolymph collects in a relatively large vascular space, the pre-gill or infrabranchial (Ib) sinus, before moving through the gill circulation, and into the pericardial (P) sinus, in which the heart is suspended. We are interested in characterizing gill perfusion in resting and active lobsters. Hemolymph moves through the gill circulation down a hydrostatic pressure gradient from the Ib to the P sinuses. The Ib sinus, though geometrically-complex, is a contiguous space and our hypothesis was that hemolymph pressure should be equivalent at all points in the space. Perfusion of the different gill groupings within a gill set, driven by equivalent Ib sinus pressure, should be relatively equivalent. We measured hemolymph pressure along the length of the Ib sinus (at the base of the cheliped, and pereiopods 3 and 5) in lobsters at rest and while the animals walked at a steady rate on a submerged treadmill. We found that hemolymph pressure is not homogeneous in the Ib sinus in resting lobsters, being higher at the anterior and posterior ends of the sinus by as much as 2-fold. During exercise, we found that pressure in the sinus became more homogeneous, although we still saw substantial pressure differences along the sinus’s length. These results suggest that gill perfusion may vary considerably along the length of a gill set with implications regarding gas exchange and other gill functions.
