A recent study on jellyfish-like creatures, called hydras, has revealed a strange phenomenon. When overfed, these tiny freshwater organisms can develop transmissible tumors, which can be passed to their clone offspring. This finding not only helps us understand tumor development in hydras but also offers new insights into the wider study of contagious cancers. While cancer is a common risk for multicellular life, very few cases involve tumors spreading between individuals.

Most notably, transmissible cancers have been observed in Tasmanian devils, dogs, and several types of bivalves. Scientists are particularly keen to study how these cancers spread in order to prevent them in humans and other animals. Tasmanian devils, for example, suffer greatly from a facial tumor disease that threatens their population.

Rapid Reproduction Linked to Tumor Growth

However, finding new cases of contagious cancer is challenging. This led evolutionary ecologist Sophie Tissot, from the French National Centre for Scientific Research, and her team to approach the issue from a different angle. Conveniently, 15 years ago, hydras in a lab setting developed tumors after being overfed, providing a unique opportunity for further study.

Hydra oligactis, which reproduces asexually by cloning, is especially useful for cancer research. These hydras can form tumors in lab environments, offering insights into the genetic processes behind cancer. Tissot and her colleagues aimed to demonstrate the value of studying hydras for understanding the evolution of transmissible cancers.

Their research involved collecting 50 hydras from Montaud Lake, France, and recreating conditions in the lab that prompted tumor development in earlier studies. Some hydras were overfed, and within two months, many had developed tumors. The researchers then studied how these tumors were passed through five generations of hydra clones. They confirmed that tumors in hydras could be passed on and even increased over time.

Environmental Factors and Cancer Spread

Interestingly, they found that hydras with transmissible tumors began to reproduce faster before tumors fully developed, possibly as a survival strategy. Tumor-carrying hydras produced more buds early on, while the buds themselves had higher mortality rates once tumors appeared. This could reflect a life-history adjustment to offset the costs of tumor growth.

The researchers concluded that while transmissible cancers are rare, environmental conditions might play a key role. Human activity could disrupt ecosystems and create environments where these cancers spread more easily.

This study, published in Proceedings of the Royal Society B, highlights the need to consider these factors in the ongoing study of contagious cancers.