Size, Weight and Chemical Composition

Abstract

The measurement of copepods has been made by different people in different ways. The length of the metasome is perhaps the measurement used most frequently but often the total length, i.e. to the end of the caudal furcae, has been taken. This however has the disadvantage that if, as frequently happens, the urosome is bent, two measurements are necessary. Sømme (1934) points out that after fixation a variable amount of stretching or telescoping takes place between the free segments of the metasome and especially between the metasome and urosome and that a more reliable measurement is that of the cephalosome. By this means only could he distinguish between the early copepodite stages of C. finmarchicus and C. hyperboreus. Although this is probably an improvement on the other measurements used, his suggestion has not been generally adopted. In addition different fixatives may cause either stretching or shrinking; formalin for instance increases the length slightly.