The Hook: In one of the digests, a line flashed by that was easy to scroll past as a curiosity: "Japanese biologists are teaching shrimp to feed in microgravity conditions — for a future lunar base." At first glance — amusing exotica, something in the spirit of a "did you know?" science column. But when I dug into it, it turned out that behind this formulation hides one of the most beautiful engineering challenges of the decade — a story about how a team from Okayama University of Science spent three years heroically reinventing the wheel, because no one before them figured out that the classic clinostat doesn't work on motile animals. And the second, even less obvious discovery — why exactly weightlessness turns out to be the ideal environment for their own "Third Water," even though on Earth it was their main headache. This is a rare case where space solves an Earth problem rather than creating a new one.
To understand why a Japanese (and in parallel — French) research center needed crustaceans in orbit, we need to step half a pace back. Any serious lunar or Martian base is essentially a closed biosphere in a can. NASA has been working since the 1960s on the concept of Bioregenerative Life Support System (BLSS): a cycle in which plants take carbon dioxide from the crew, produce oxygen and food, and crew waste goes back as fertilizer. The problem is that a plant-based diet is catastrophically inadequate for humans: critically lacking complete protein, omega-3 fatty acids (EPA/DHA), vitamin B12, and taurine. Humans don't synthesize these nutrients themselves and must get them from animal food.
Hauling cows to the Moon — madness: cattle consume too much oxygen, emit too much CO₂, require enormous areas and cumbersome manure disposal systems. But fish and crustaceans — a completely different league. According to a 2021 review in Frontiers in Astronomy and Space Sciences, fish consume 5–20 times less energy and 3 times less oxygen than mammals. Their excrement is dissolved directly in water and easily handled by biofilters. FCR (feed conversion ratio) in fish is radically lower than in chickens and cows. And — a key bonus for space — water is a natural radiation shield, which is critical outside Earth's magnetic field.
So the logical strategy: on the base they build integrated multi-trophic aquaculture (IMTA) — microalgae → zooplankton/shrimp → fish → human. Each link processes the waste of the previous one. Algae provide oxygen, shrimp convert plant waste into high-protein meat, fish synthesize EPA/DHA from algal biomass. Closed loop. Beautiful on paper. But there's a catch: no one has ever raised these animals in weightlessness, and the feeding process itself — from swallowing food to its passage through the intestine — may work completely differently in the absence of gravity.
Standard methods of simulating microgravity on Earth are parabolic flights (several seconds of weightlessness per airplane dive) and drop towers (also seconds). For plants and bacteria, that's enough. But to film a full 15-minute video of a shrimp eating, you need something else.
The most accessible device — a clinostat. This is a device that rapidly rotates a sample, constantly changing its orientation relative to the gravity vector. If you spin fast enough, the object "doesn't have time to figure out" where up and down are, and on average "sees" zero gravity. Standard clinostats operate at 10–25 RPM — enough for cell cultures and seedlings. But not for a shrimp.
And here the actual engineering drama begins. The team of Toshimasa Yamamoto (Okayama University of Science) spent three years struggling with the fact that an ordinary clinostat doesn't work on motile animals. The reason is simple and elegant: a shrimp or fish — not a wheat seedling. They actively change posture in water. At 20 RPM they simply have time to reorient and swim to the center of rotation, where centrifugal force is minimal. That is, the clinostat for them is not weightlessness, but a carousel with a centrifugal gradient.
The team tried several alternatives:
Then they decided to go all in: ordered from Advanced Engineering Services Co., Ltd. a custom clinostat that rotates at ~130 RPM — more than two rotations per second. At such speed even an active shrimp doesn't have time to reorient. They with their own hands (more precisely, the hands of engineer Kanji Kameyama from the university Design and Manufacturing Center) designed and assembled:
And it worked. They filmed the first video in history of a kuruma shrimp (Marsupenaeus japonicus) feeding in simulated microgravity.
The results turned out to be not alien, but very practical:
Active rotation creates an internal water flow in the container at a speed of ~0.15 m/s. This water "throws" the shrimp in different directions, preventing it from eating calmly. The shrimp instinctively clings to the plastic mesh inside the container to fix its position — a clear illustration of how behavior changes in the absence of a stable "bottom."
The shrimp eats only what ends up right in front of its mouth. On Earth, the kuruma shrimp is an active ambush predator that attacks moving prey. In the clinostat it passively waits for a food pellet to end up in close proximity. That is, locomotion and hunting in weightlessness are drastically simplified — the shrimp loses the ability for active capture.
When the water calms down — the shrimp eats most effectively. This is a critical clue: the main problem is not the absence of gravity per se, but the hydrodynamics of weightlessness. If you deliver food into still water (for example, through an automatic dispenser), the shrimp will cope.
Genetic analysis (Gene Ontology) revealed changes in genes responsible for chitin metabolism and cuticle development — that is, the shell. In a shrimp that spent 24 hours in pseudo-microgravity, not only behavior changes, but the very biology of the exoskeleton. This intersects with Yamamoto's own observation that in weightlessness shrimp shells become thinner — and that's already a direct engineering risk for the life support system.
To verify the results on a statistically significant sample, researchers added Artemia (also known as "sea monkeys") — tiny crustaceans about 1 mm long. They fit 10 per container, and they spent 4 full days in the clinostat. Artemia successfully consumed the microalga Tetraselmis, excreted waste products, and grew significantly during that time. That is, the entire food chain "alga → crustacean → growth" works in microgravity without visible problems.
This is the first proof that a full trophic chain in orbit is not fantasy, but an engineering problem with an understandable solution.
While the Japanese were fine-tuning the clinostat, the French from Ifremer under the wing of CNES (French space agency) and with ESA support were developing the parallel program Lunar Hatch. Their goal is even more ambitious — send fertilized eggs of European sea bass (Dicentrarchus labrax) to the Moon so they hatch in a lunar biosphere. The logic is ruthlessly elegant:
Lunar Hatch is now preparing tests on ESA's GEPAM (Gravitational Experimental Platform for Animal Models) platform — there they'll test embryo behavior in hypergravity (5–8 g at launch) and real microgravity (aboard ISS or suborbital vehicles).
Here's where I found the tastiest bit. Yamamoto's team has "The Third Water" (Koteki-Kankyo-Sui) — a patented formulation with pH 7, containing exactly the minimum salts (sodium, potassium, calcium) that fish need. The main trick: marine and freshwater fish can live in the same water. Ideal for space, where every liter counts.
But this water has a critical bug on Earth: its density is so low that fertilized fish eggs sink. And even after hatching, larvae can't float up. And to feed on plankton that drifts in the water column, a larva must hang in the column. On Earth — doesn't work. 25 years of research at Okayama beat against this wall.
And now — the twist. In weightlessness gravity disappears, and eggs with larvae remain in a natural suspended state by default. The problem they struggled with for decades is solved by the very fact of space. Yamamoto says this directly in an interview with Global Seafood Advocate: "The biggest challenge we've faced – the sinking of eggs in low-density water – is instantly solved in space."
This is a rare case where space doesn't create a problem, but removes a fundamental Earth one. Just like with cryogenic superconducting magnets (which on Earth require liquid helium, but in deep space can be cooled passively) or 3D printing of organs (which on Earth suffers from the construction's own weight).
Yamamoto's goal — full-scale aquaculture experiment on ISS by ~2030. Fully automated C-RAS (Closed Recirculating Aquaculture System):
As candidates for "space fish," Yamamoto is considering red sea bream, flounder, greasyback shrimp, and grouper. Grouper is especially attractive: FCR 1.2 — that is, 1.2 kg of feed yields 1 kg of fish. Nearly ideal.
In parallel, Ifremer is working out delivery of fertilized eggs to the lunar surface, and JAXA is discussing SpaceGenFish — a fully automated system for ISS.
Behind the beautiful architecture lurk several serious questions that still await their researcher:
If Yamamoto's team achieves a working C-RAS by 2030, it will be the first closed food chain in human history beyond Earth. Not a tube of paste, not freeze-dried cottage cheese, but live fish grown in orbit from eggs delivered from Earth. This is essentially the first step toward a true extraterrestrial civilization — civilization is defined not by the presence of buildings, but by the ability to produce food for one's kind from local resources.
And the second, more modest thought: this story is a typical example of how a space program unintentionally solves Earth problems. Yamamoto's "Third Water" tormented him for 25 years — and weightlessness turned out to be not a new difficulty, but the key. Just as ISS research on regenerative cardiac medicine has already yielded Earth-based methods for treating heart attacks; plant biology in orbit has already produced new wheat varieties. Every time we hear "why spend billions on space?" — it's worth remembering that very often the main value is found not in antennas and not in rocket fuel, but in understanding how life works in extreme conditions. A shrimp chewing food in a clinostat at 130 RPM is not a curiosity. It's a small brick in the foundation on which in 50–100 years an extraterrestrial farm may stand.
What struck me most in this story was the engineering honesty of Yamamoto's team. Three years. Three years they went through one standard approach after another (tower, parabola, magnetic levitation), got failures, and instead of giving up or pretending "well, it kind of works," they ordered a custom 130 RPM clinostat from an external contractor and themselves, by hand, in a university workshop, designed the containers and mounts. This is a rare archetype in modern science — "benchtop engineering" in the spirit of the 19th century, when the experimental physicist soldered his own instruments.
Second — the humiliating rightness of space. No matter how much we design biospheres for Earth gravity, space stubbornly offers us different rules. And the only way not to bump into things in orbit is to spend years fine-tuning prototypes on Earth, and exactly the way Yamamoto fine-tunes them: through attempts, failures, manual work, and willingness to reinvent a basic instrument if it doesn't cope.
Third — this is a story about idea contagion between domains. The French Lunar Hatch project, Japanese C-RAS, German OMEGAHAB, American Veggie, Soviet/Russian programs with medaka — all of them independently feel out the same conclusions: water is the best environment for life in space, feeding fish with eggs is cheaper than with live fish, a closed cycle requires a multi-level trophic chain. This is convergence — when different teams, in different countries, by different methods, arrive at the same architectural answers. A good sign: it means the answers are correct.
And fourth, for the engineer in me — admiration for the simplicity of the "Artemia → Tetraselmis" link. Tiny crustaceans 1 mm long, 10 of which fit in a container, feed on microalgae, excrete waste, grow for 4 days in continuous microgravity. This is an ideal model organism for space biology: small, fast, statistically reproducible. An order of magnitude better than shrimp, of which only 1–3 fit in the clinostat. And if C-RAS ever flies to Mars, Artemia will be first in it — like yeast in a brewery, like E. coli in biotechnology.
Subjectively: I'm not a big fan of seafood, but after this investigation I look at an ordinary shrimp on a plate with some new respect. This is a creature whose ancestors survived four mass extinctions, and now may become one of the first species that humans deliberately grow beyond the cradle. And if in 30 years there really is a lunar-Martian fish market on Mars — it will be opened by a Japanese biologist who wasn't afraid to order a more powerful clinostat.