On a 12-day Russian biosatellite flight, seven silkworm varieties spun silk, built cocoons, mated and laid eggs; some developmental stages occurred 2-3 days faster than ground controls

Silkworms are one of the oldest domesticated insects on the planet, yet they are still teaching scientists new things; this time about surviving space. According to the study, ‘Space flight experiment on Chinese silkworm on board the Russian 10th Biosatellite,’ published in Advances in Space Research by researchers at the Institute of Space Medico-Engineering in Beijing, seven varieties of the silkworm Bombyx mori were sent to space aboard a Russian biosatellite for 12 days. Amongst the passengers on the spacecraft were separate batches of silkworms at every stage of the life cycle, eggs, larvae, pupae, and adult moths, plus cocoons already forming, so that different groups could reach different milestones in parallel during the short flight, rather than any single batch racing through the entire cycle alone. Across these groups, silkworms in orbit successfully spun silk, formed cocoons, mated, laid eggs, hatched, pupated, and emerged as moths.

A biosatellite built for biology

The mission behind this experiment was Bion 10, also called Cosmos 2229. It was launched by Russia on December 29, 1992, and recovered near Karaganda, Kazakhstan, on January 10, 1993, after thermal-control issues forced the spacecraft to return two days ahead of its planned 14-day mission, having spent 12 days in orbit. Bion 10 belongs to a longer series of missions conducted by the Russians since the Soviet era, where monkeys, insects, plants, and other living things have been sent into orbit to study the effects of zero gravity and radiation on their physiology. NASA's own technical document notes that Cosmos 2229 is the eighth of the series of collaborative US and Russia biosatellite missions, with experiments sponsored by various countries, including the US, France, Germany, Canada, and Kazakhstan alongside the Chinese silkworm project.

What went right in orbit

The silkworm life cycle includes sensitive stages such as the egg-to-larva transition, cocoon spinning, and the adult moth stage, when it mates and lays eggs. Any one of these stages can easily go wrong in the environment created by vibrations during launch and the microgravity of space flight, along with a closed capsule. Researchers observed that not a single phase went wrong during their 12-day trip to space. All the stages of the silkworm life cycle, including cocooning, mating, and oviposition, were successfully carried out during the entire flight of 12 days, which is itself a meaningful result for a mission this short.

Faster hatching, and eggs that hatched more easily

Developmental timing was the area where the effects of spaceflight were most apparent. The data show that hatching and egg laying in the experimental group happened two to three days faster compared to those processes in the control group. A second, related finding involved diapause eggs, the dormant eggs laid by silkworms when conditions become unfavorable and which then begin development after some time. The hatching rate of these dormant eggs was higher in the space-flown group than in the control group, suggesting that the flight environment may have made it easier for some eggs to break dormancy and hatch.

Not without side effects

The outcomes of the mission have been inconsistent. Researchers documented that the lifespans of two of the seven silkworm breeds tested in space were shorter than those of the same breeds on Earth. In addition, genetic variation was observed in three of the seven breeds, though the abstract does not specify what form these variations took. The combination of results, including rapid growth on one hand and shorter lifespans and genetically altered silkworm varieties on the other, suggests that space travel has diverse effects on various silkworm breeds instead of one uniform impact.

Why the embryo stage stood out

Taken together, the authors of the Chinese study concluded that the embryonic phase is the one that is the most sensitive to the spaceflight conditions. It also fits the trend seen in the results themselves, as the factors which were shown to have the most influence on the moths, such as hatching time, hatching rate, and genetic differences, all trace back to what happens to an egg before it hatches, rather than to the larva, pupa or moth stages that follow.

Silkworms have done this before

It wasn’t the only time a silkworm went to space. A separate silkworm experiment flown roughly a decade and a half later by Japanese researchers aboard Russia's Foton-M3 biosatellite, also a 12-day mission, found similarly encouraging results for the later life stages. Male moths that had been to space were mated with female moths that were on Earth, and more than 95 percent of the eggs laid by these moths hatched normally, according to the research results reported by the Japan Aerospace Exploration Agency. When taken together, the results of the two studies show that silkworms' reproductive system is capable of functioning in space, even though, as seen from the Chinese study, the egg stage itself carries the most visible signs of change.