Comparative Analysis of Muscle Atrophy During Spaceflight, Nutritional Deficiency and Disuse in the Nematode Caenorhabditis elegans.

While spaceflight is becoming more common than before, the hazards spaceflight and space microgravity pose to the human body remain relatively unexplored. Astronauts experience muscle atrophy after spaceflight, but the exact reasons for this and solutions are unknown. Here, we take advantage of the nematode C. elegans to understand the effects of space microgravity on worm body wall muscle. We found that space microgravity induces muscle atrophy in C. elegans from two independent spaceflight missions. As a comparison to spaceflight-induced muscle atrophy, we assessed the effects of acute nutritional deprivation and muscle disuse on C. elegans muscle cells. We found that these two factors also induce muscle atrophy in the nematode. Finally, we identified clp-4, which encodes a calpain protease that promotes muscle atrophy. Mutants of clp-4 suppress starvation-induced muscle atrophy. Such comparative analyses of different factors causing muscle atrophy in C. elegans could provide a way to identify novel genetic factors regulating space microgravity-induced muscle atrophy.

Comparison of Life Traits in Two Bacterivorous Nematodes Suggest Different Ecological Strategies to Exploit Similar Habitats.

Environments can be in states of dynamic change as well as persistent stability. These different states are a result of outside external conditions, but also the constant flux of living organisms in that ecological fauna. Nematodes are tremendously diverse, and many types can reside in the same soil microenvironments at the same time. To examine how so many nematodes can thrive and exploit a single environment, we identified two bacterivorous nematodes, Caenorhabditis elegans and Acrobeloides tricornis, that can inhabit rotting apple and soil environments. We cultured both nematodes in the laboratory and compared their life traits. We found that whereas C. elegans develops and reproduces extremely quickly, A. tricornis reaches sexual maturity much later and lays eggs at a slower rate but remains fertile for a longer time. In addition, A. tricornis displays a slower feeding behavior than C. elegans. Finally, A. tricornis has a significantly longer lifespan than C. elegans. These differences in development, physiology and behavior between the two nematodes hint at different ecological strategies to exploit the same habitat over different time periods, C. elegans as a colonizer-type nematode, and A. tricornis as more of a persister.

Consumption of Oleic Acid During Matriphagy in Free-Living Nematodes Alleviates the Toxic Effects of the Bacterial Metabolite Violacein.

Maternal behaviors benefit the survival of young, contributing directly to the mother's reproductive fitness. An extreme form of this is seen in matriphagy, when a mother performs the ultimate sacrifice and offers her body as a meal for her young. Whether matriphagy offers only a single energy-rich meal or another possible benefit to the young is unknown. Here, we characterized the toxicity of a bacterial secondary metabolite, namely, violacein, in Caenorhabditis elegans and found it is not only toxic towards adults, but also arrests growth and development of C. elegans larvae. To counteract this, C. elegans resorted to matriphagy, with the mothers holding their eggs within their bodies and hatching the young larvae internally, which eventually led to the mothers' death. This violacein-induced matriphagy alleviated some of the toxic effects of violacein, allowing a portion of the internally-hatched young to bypass developmental arrest. Using genetic and pharmacological experiments, we found the consumption of oleate, a monounsaturated fatty acid produced by the mother, during matriphagy is partially responsible. As such, our study provides experimental evidence of why such a drastic and peculiar maternal behavior may have arisen in nematode natural habitats.