When people go to the aquarium—either by themselves or with their families—they usually go to see the big, attention-grabbing animals: sharks, sea lions, belugas, or even jellyfish. I myself have been part of this crowd, but as someone who wants to pursue a scientific career, I also have to think about the small stuff. The species that don’t draw huge crowds are often the ones that are most important to the ecosystem. I wanted to highlight a species that has existed for millions of years yet remains unfamiliar to many people: comb jellies (Ctenophora), a group of marine invertebrates that has been around for over 700 million years. Some scientists believe comb jellies may have been the first animals to evolve, predating jellyfish and anemones—meaning they are literally part of the blueprint of animal life. Their structures for movement evolved from the tentacles of sea-dwelling ancestors; as mouths expanded and body size decreased, the tentacles shifted toward the rear. Not all comb jellies are the same size; some grow much larger than others, because factors such as food availability, species differences, and environmental conditions all play a role. Comb jellies feed on zooplankton, larval fish, and other small organisms, while their predators include turtles, sea jellies, and larger fish. Ultimately, the main goal of raising awareness about comb jellies is to understand how and why they are so important to the ocean.

Comb jellies play a crucial role in marine ecosystems. As mentioned before, they serve as a food source for larger animals, help regulate plankton populations, and most importantly, provide insight into how species adapt to extreme climate change. Comb jellies are able to tolerate a wide range of temperatures and salinities, and they reproduce quickly, allowing them to colonize new areas. In some scenarios, however, these traits can have negative ecological effects. Rapid population increases can disrupt ecosystems by reducing competition within food webs, and comb jellies can also impact commercial fisheries by consuming fish eggs and larvae, leading to decreased fish populations.

Although ancient, comb jellies can be both beneficial and harmful in today’s marine ecosystems. They help control populations of smaller organisms, contribute to nutrient cycling, and play a role in carbon transport. Yet their ability to thrive under changing climate conditions allows them to outcompete other species, potentially destabilizing food webs. Because of this dual nature, understanding comb jellies is essential for predicting and protecting the future health of our oceans.