The duration of embryonic development depends upon temperature. The young hatch with a yolk reserve that allows them to survive for a few days in the absence of food. When food, especially mysids, is available, the hatchlings begin to attack immediately. Swimming prey are seized by the tentacular clubs. Benthic prey, such as crabs, are pounced upon and seized with the arms.
Growth is fast.
In tropical species, a chamber may be formed daily so that the number of septa corresponds to the age in days. In temperate water however, it takes two to three days for a new chamber to be completed. Spawning takes place over a prolonged period of time or throughout the year. The number of mature eggs found in the ovary at any one time is not an indicator of fecundity. In Sepia officinalis the total of laid eggs surpasses by several times the holding capacity of the ovary.