In Situ Observation of Shrimp Feeding Process Under Microgravity Environment

We carried out an in situ observation of the feeding process of edible shrimp in a microgravity environment. To realize that condition, we developed a new type of clinostat with high-speed rotation, with a maximum rotation of 130 rpm. Under that rotation speed, aquatic organisms such as fish and crustaceans have a suppressed capability of recovering their proper swimming form, making it possible for them to be exposed to a pseudo-weightless condition. This method allowed us to successfully observe the feeding process of shrimp in that condition. As a supporting experiment, we conducted similar experiments using larval Artemia crustaceans, i.e. brine shrimp, and we confirmed that they, too, can exhibit feeding behavior under a weightless environment, even when exposed for the long period of four days. According to a gene ontology analysis of shrimp exposed to microgravity for 24 h, a significant difference was detected in the exposed shrimp as compared with control shrimp at 1 G. Those results suggested that exposure to weightlessness may have a biological impact on the shrimp, although the details are unknown yet. We believe that the high-speed clinostat will contribute greatly to the future progress of engineering applications in microgravity research.