One of the amazing things you get to see when diving with sharks is the ubiquitous remora, (Perciformes Echeneidae). a fish that has developed a sucker mechanism situated on the top of the remoras head that enables it to attach to a shark and hitch a free ride, thereby conserving energy and staying close to the action. It is not uncommon to see large tiger sharks with up to seven of remoras attached to their underbelly, patiently waiting for the right time to detach and grab an easy meal.
I’m not quite sure how these guys identify the ideal host, but often they will try and ‘hook up’ with a freediver, swimming around you perhaps trying to assess whether you would be a suitable host. Towards the end of a recent shark dive I made this shot of Wolfgang Leander with seven remora who were momentarily considering him as a possible host. Quite fitting actually!
Wikipedia has the following to say about the relationship between remora’s and their hosts:
“The relationship between remoras and their hosts is most often taken to be one of commensalism, specifically phoresy. The host they attach to for transport gains nothing from the relationship, but also loses little. The remora benefits by using the host as transport and protection and also feeds on materials dropped by the host. There is some controversy over whether a remora’s diet is primarily leftover fragments, or actually the feces of the host. In some species (Echeneis naucrates and E. neucratoides) consumption of host feces is strongly indicated in gut dissections. For other species, such as those found in a host’s mouth, scavenging of leftovers is more likely. Many sources also suggest that for some remora/host pairings the relationship is closer to mutualism with the remora cleaning bacteria and other parasites from the host.”
From my own experience, I have seen a Zambezi shark try to eat its own remora, chasing it to the surface at great speed, which would perhaps suggest that as with all relationships, things can get a bit tenuous at times!