Culture of fish food organisms

Unit 8 - Brine Shrimp or Artemia

8.4.3.Development of an Artemia cyst from incubation in seawater until nauplius release
When incubated in seawater the biconcave cyst swells up and becomes spherical within 1 to 2 h. After 12 to 20 h hydration, the cyst shell (including the outer cuticular membrane) bursts (= breaking stage) and the embryo surrounded by the hatching membrane becomes visible. The embryo then leaves the shell completely and hangs underneath the empty shell (the hatching membrane may still be attached to the shell). Through the transparent hatching membrane one can follow the differentiation of the pre-nauplius into the instar I nauplius which starts to move its appendages. Shortly thereafter the hatching membrane breaks open (= hatching) and the free-swimming larva (head first) is born. Dry cysts are very hygroscopic and take up water at a fast rate i.e. within the first hours the volume of the hydrated embryo increases to a maximum of 140% water content; However, the active metabolism starts from a 60% water content onwards, provided environmental conditions are favourable.
The aerobic metabolism in the cyst embryo assures the conversion of the carbohydrate reserve trehalose into glycogen (as an energy source) and glycerol.