To obtain an estimate of the amount of cannibalism that may occur in natural conditions, we
experimentally recorded the spontaneous hatching of cysts across a female’s lifetime. Freshly matured females, isolated from batch cultures, were transferred to 1.5 l aquaria, filled with EPA medium. Four males per female were added, to ensure a continuous fertilization of the females. They were fed the standard algal diet, given 1200 lux illumination, a 12/12 photoperiod, and a 25% water renewal regime per day. At each release of a clutch, any cysts deposited were removed at once. They were counted and kept in separate vials in 40 ml of
medium taken from their original aquarium. Per individual clutch, the incidence of spontaneous
hatching was followed and summed over a week. All nauplii that hatched were counted and removed
from their container daily. The experiment was conducted in quadruplicate, and lasted until
the last female died after 96 days and 36 clutches.