On Caribbean coral reefs, an unlikely partnership has gone largely unnoticed: tiny fish regularly nestle within the feathery structures of tube worms. While these sensitive worms typically snap shut at the slightest disturbance, they show a remarkable tolerance for their tiny guests.
A study published in Symbiosis , found that these small coral reef fishes form previously undocumented associations with Christmas tree worms and other tube-dwelling worms on Caribbean coral reefs. This discovery is potentially the first time this symbiotic behavior has been observed between fish and worms.
Lead author on the study Morgan Bennett-Smith, a PhD candidate in Boston University Marine Evolutionary Ecology Laboratory , noted that this behavior was really strange, because these worms are extremely skittish thus prompting further investigation. Earlier research conducted by Bennett-Smith has shown this same behavior between the fish and worms in Papua New Guinea.
"It may represent a widespread ecological phenomenon that scientists have simply overlooked, and suggest that there are potentially many micro interactions that remain undocumented," said Bennett-Smith. "Coral reefs are host to various forms of life and observing these small interactions could unveil new discoveries of how coral reef ecosystems function."
This research grew out of the Boston University Marine Program (BUMP) , involving undergraduate student researchers, who learned scientific diving and underwater research methods through BUMP's curriculum. For many students this was their first experience conducting underwater research.
"Participating in projects like this is all I've ever wanted to do. From pouring over marine science books as a kid to now having the opportunity to work with researchers in the program and explore marine ecosystems, that's what I spent every night dreaming about. It was the opportunity of a lifetime for me," said Boston University undergraduate researcher Mason Murchison.
"Modern biology often focuses on genomics, big datasets, and advanced technology. Those tools are incredibly important, but discoveries still begin with people paying attention to the natural world. This study started because divers noticed something unusual and asked questions. The fact that we were able to connect observations from Papua New Guinea, Belize, and archival photographs from Bonaire highlights that many hidden interactions on coral reefs are waiting to be discovered." remarked Bennett-Smith.
Groups of undergraduate researchers would document through diver surveys the neon gobies' interactions with the Christmas tree worms by swimming over the coral reefs and stopping for 10 minutes when they saw the fish and worms together. Uncovering and documenting these relationships is vital to understanding the way coral reefs function and how they react to environmental change.
Bennett-Smith emphasized that "the field surveys the students conducted for their class project became an important part of this research and I'm most proud of the student involvement in this study and the opportunity to introduce them to scientific research."
The researchers noted that the nature of the relationship between the fish and worms is unclear and potentially the first time this behavior has been observed. It is not yet understood who is benefiting from this association and looking further into whether it's a mutualistic relationship, a commensal relationship, or even a parasitic relationship, would be one aspect for continued study. Additional steps for further investigation might involve bringing the fish and worms into a controlled lab environment that might help uncover the nature of their relationship.
