Hiding in Plain Sight: Evidence of Echeneidae Cloacal and Gill Diving Behavior in Manta Ray Hosts.

Symbioses between remoras (Family Echeneidae) and marine megafauna are well-documented across diverse lineages. However, despite recent advancements in understanding the intricacies of these interactions, the dynamics of these relationships remain poorly understood, largely due to the highly mobile nature of both host and symbiont. Here we report seven observations of Echeneidae cloacal diving behavior in manta rays. These observations span all three currently described species of manta rays (Mobula yarae, Mobula birostris, and Mobula alfredi), demonstrate that large Echeneidae can perform cloacal diving behavior in both juvenile and adult manta rays, and show that this behavior occurs across multiple ocean basins. We also document one observation of Echeneidae attachment beneath a host's gill slit and several occurrences of gill injuries consistent with Echeneidae intrusion. These observations contribute to the growing database of Echeneidae-host behavioral interactions and provide an important foundation for understanding the extent, diversity, and dynamics underlying these highly debated, cryptic megafauna-symbiont interactions in marine environments. By providing new evidence of the complexity of symbiotic relationships in marine environments, this study also offers a multi-species natural history context that may inform future research and conservation considerations.