Research Highlights

1. Discovery of Tumors in Wild Hydra Populations

For the first time, my work demonstrated the presence of spontaneous tumors in natural populations of hydras. Through field sampling and histological analysis, I confirmed that these tumors are composed of abnormally proliferating cells. Interestingly, the microbiome of these hydras revealed the presence of an unidentified species of Chlamydiales, potentially implicated in tumor formation.

2. Host Life-History Traits and Tumor Manipulation

I investigated how these tumors influence hydra life-history traits, discovering that:

• Tumorous hydras exhibited increased asexual and sexual reproduction before succumbing to early death, suggesting a compensatory reproductive strategy.

• The tumors were found to manipulate host phenotypes, including the development of additional tentacles, enhancing prey capture and potentially benefiting both the host and tumor cells.

3. Experimental Validation of Tumor-Induced Manipulation

Using transplantation experiments, I demonstrated that:

• Tumors were responsible for inducing the growth of additional tentacles in their hosts, confirming tumor-driven phenotypic manipulation.

• This behavior mirrors strategies typically associated with parasitic organisms, providing novel insights into the evolutionary potential of tumors.

4. Ecological Consequences of Host-Tumor Interactions

I explored the broader ecological implications of tumorous hydras within aquatic ecosystems, finding that:

• Tumorous hydras attracted more predators, such as fish, compared to their healthy counterparts.

• They were more frequently colonized by commensal ciliates, altering their ecological interactions.

• Enhanced tentacle growth improved prey capture efficiency, further complicating their role in ecosystem dynamics.