Degrees of vacuolation of the absorptive intestinal cells of five Sagitta (Chaetognatha) species: possible ecophysiological implications

The intestinal S-cells show few ultrastructural differences among the five species, whereas the vacuolar volume of the A-cells is higher in the mesoplanktonic species of Sagitta. Data further reveal differences in the degree of intestinal vacuolation among the species, whose ecophysiological implications influence their vertical distribution pattern.