定義： A 1D measurement of a single cell along its longest axis. Typically, this is the distance along a straight line connecting the anterior-most point and the posterior-most point.
定義： A 1D measurement of a single cell. Typically, this is the distance along a straight line connecting the left-most part of the cell to the right-most part of the cell. It is perpendicular to the length axis and the depth axis.
定義： Living in the fluid medium (water or air) but unable to maintain their position or distribution independently of the movement of the water/air mass (adapted from Lincoln et al., 1998).
