Meeting Abstract
Remoras (Family Echeneidae) are best known for their cranial suction disc modified from dorsal fin elements. Remoras use the disc to adhere to a number of different hosts (e.g. sharks, fish, turtles, marine mammals, and ship hulls) for several possible reasons, including efficient travel, feeding opportunities, and locating mates. While previous work has shown that remoras can generate suction forces opposing pull-off removal, our research has found that the remora disc is a complex hierarchical mechanism with many different factors contributing to the long term but easily reversible nature of the remora adhesive disc. Here we focus on two morphological features that are responsible for maintaining attachment to a host: lamellar spinules and cranial vasculature. Using a friction model to estimate the spinule contribution to shear resistance, we found that the tooth-like spinules on the flat lamellae that make up the disc generate friction an order of magnitude greater when interacting with a rough substrate like shark skin than with a smooth surface, thereby explaining the difference in adhesive strength on different surfaces observed in previous work. The cranial vasculature of remoras is highly modified with respect to the position and relative size of anterior veins as compared to other fishes. Most notably, the anterior cardinal sinus lies dorsal to the cranium, in direct contact with the ventral surface of the disc. Presumably the orientation of the remora cranial vessels contributes to applying pressure on the disc against the host to maintain strong adhesion for extended periods of time.
