As far as we know, food does not exist naturally in space. If we want to explore the cosmos, we must bring it with us. Among the oldest and most common types of food on planet Earth is seafood, yet we know surprisingly little about how aquatic animals will react to the microgravity they will encounter in space.
A new study by researchers from Okayama University of Science in Japan, recently published in the journal Microgravity Science and Technology, aims to answer this question. It employs a novel method of simulating microgravity to observe the response of crustaceans to a space environment and finds that they may become suitable candidates for a future space food chain.
Most experiments in microgravity conditions on Earth are conducted in drop towers or during parabolic flights—both methods provide only a few seconds of true “microgravity” and are unsuitable for longer-term studies. The International Space Station offers an alternative, but it is extremely expensive and has very limited space for additional experiments. Therefore, the researchers turned to an alternative tool: the clinostat.
These specialized chambers rapidly change the orientation of their contents, altering the gravitational field and simulating at least some effects of microgravity. They rotate in such a way that the combination of gravity and centrifugal force effectively cancels out over a given period. These setups work well for single-celled organisms and plants, but they are less effective for complex animals.
Conventional clinostats rotate relatively slowly—only 10-25 rpm. An agile animal placed in such a clinostat can reorient itself quickly enough to counteract the centrifugal force, undermining the “microgravity” effect that works so well with less complex organisms. So the researchers thought: why not create a clinostat that rotates faster?
They developed a custom clinostat that spins at around 130 rpm—more than two rotations per second. This high rotation speed prevents complex organisms, such as shrimp or fish, from having enough time to reorient themselves with respect to Earth’s gravitational field before the machine changes that orientation. In other words, the rotation’s acceleration allows these aquaculture samples to experience genuine pseudo-weightlessness.
Using their new high-speed clinostat, the researchers began experiments on actual animals. The first were juvenile kuruma shrimp. The researchers constructed a sample container with a digital camera and lighting, subjecting the shrimp to 15 minutes of simulated microgravity while closely observing them as they attempted to feed. The active rotation caused strong water splashing inside the container, generating an internal flow at a speed of approximately 0.15 meters per second.
To compensate for the water splashing, the shrimp clung to a plastic mesh placed inside the container. They also consumed only those food pellets that appeared directly in front of their mouths, rather than actively hunting as they would in a normal 1G gravity environment. Importantly, when the water flow stopped, the shrimp fed most effectively. Unfortunately, it is difficult to determine whether the limited feeding behavior was caused by the water splashing or by microgravity, but the increased activity after the water movement ceased provides compelling evidence that shrimp will indeed feed actively under microgravity conditions if exposed to them.
The researchers observed not only feeding behavior but also genetic changes. They exposed a group of shrimp to 24 hours of simulated microgravity and then conducted gene ontology analysis, comparing their RNA to that of a control group subjected to normal 1G gravity. Sharp changes were detected in genes controlling the metabolic process of chitin, as well as in genes governing cuticle development. Since both of these features are related to movement and the exoskeleton of shrimp, this strongly suggests that “microgravity” affects their movement even at a biological level.
Because shrimp are relatively large and thus difficult to study in statistically significant scales, the researchers also conducted an additional experiment using brine shrimp—more commonly known as Artemia or “sea monkeys.” They were placed in the clinostat for continuous four-day rotation, and the researchers observed them successfully consuming algae, excreting waste from this feeding, and significantly increasing in size. In other words, they lived under microgravity conditions, and it appeared to have no major negative effects.
However, the experiments were not entirely successful. Initially, the researchers wanted to collect data on some species of fish as well, but the cameras proved unable to handle this task, limiting the results presented in the paper to vertebrates-free subjects and creating significant opportunities for the next phase of research. Fortunately, other projects are also attempting to work with fish in space, including the Lunar Hatch Program, which hopes to place fertilized fish eggs in water on the Moon, and SpaceGenFish, which is developing a fully automated aquaculture system for use on the International Space Station.
For now, however, further research is needed if aquaculture is to play a critical role in providing fresh meat for future astronauts. Given the success of this technology on Earth and the ongoing support for its space-based counterpart, this is certainly not the last time we will hear about using sea monkeys in space experiments.
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