High-resolution computed tomography of lobster (Panulirus interruptus) stomach.

We used micro computed tomography to produce a high-resolution density image of the lobster (Panulirus interruptus) stomach and identified on this image the previously defined stomach ossicles. These data are the first coordinate-based, three-dimensional description of the stomach and are a necessary first step for developing biomechanical models of it. They are also interesting for several reasons in their own right. First, the ossicles showed large shape and density variations. These data suggest that different ossicles may serve different functions, with some acting as force-delivering levers, some as spring-like elements, and some as wall-like elements that resist internal stomach pressure or function as two-dimensional force-delivering plates. Second, large intra-ossicle density variations were present in individual ossicles, reminiscent of I-beams, oval bicycle frames, and similar mass-minimizing structural elements, suggesting that evolution has minimized ossicle mass and identifying which ossicle regions are most likely important in force delivery. Third, joints appeared to be either continuous density interconnections without distinct separations between the ossicles or 'floating' joints in which the ends of the two ossicles were separated by relatively large distances spanned by connective tissue. In these latter joints, although the distance between ossicle ends is likely maintained at a relatively constant value, a wide range of ossicle angles would thus be theoretically possible. Notably absent are close-apposition, morphologically specialized joints such as hinge or ball-and-socket joints.