“God save thee, ocean sunfish
From the fiends that plague thee thus
Why look’st thou so? With thy large shoals,
Thou fed the albatross.”
- Samuel Taylor Coleridge, sort of.
Albatrosses are superb long-distance fliers that can scour vast tracts of ocean in search of food. But sometimes, food comes to them. In July 2010, Tazuko Abe from Hokkaido University found albatrosses cleaning a school of ocean sunfish, basking at the surface of the western Pacific Ocean.
The ocean sunfish is a truly bizarre animal. It looks like someone cut the head off a much bigger fish and strapped fins to it. It’s the largest of the bony fish*. The biggest one ever found was 2.7 metres in length and weighed 2.3 tonnes. The youngsters, of course, are much smaller. The ones that Abe saw on his research cruise were just 40 centimetres long. There were at least 57 of them, each turned on its side so its broad flank faced the water surface.
The basking shoals were attending a sort of sunfish spa. The fish were infested with parasites. Pennella, a long scarlet relative of shrimp and crabs, was embedded headfirst in the flesh beneath their fins, busily sucking their blood. But not for long – black-footed and Laysan albatrosses were attracted to the shoal and picked the Pennella off their bodies. In some cases, the sunfish seems to be courting the birds, following them around and swimming sideways next to them.
Ocean sunfish live throughout the oceans but they often spend time at the surface before diving to the depths. Some scientists think that they’re absorbing heat from the sun, but it’s possible that they could also be looking for a spot of personal hygiene.
These fish can play host to at least 50 species of parasites, and they often have considerable numbers on their large bodies. Many ocean animals rely on cleaner fish or cleaner shrimp to rid them of parasites. It’s possible that albatrosses might fulfil the same role for ocean sunfish.
Of course, the association might have been a one-off. However, there are other reports of seabirds such as shearwaters and albatrosses flocking around schools of basking sunfish. This instance stands out only because Abe has photographic evidence that they were actually parasites. As he rightly points out, such events would be difficult to spot among the vastness of the open ocean.
* Fish have skeletons that are either made of cartilage, as in sharks and rays, or bone, as in all the others.
Reference: Abe, Sekiguchi, Onishi, Muramatsu & Kamito. 2011. Observations on a school of ocean sunfish and evidence for a symbiotic cleaning association with albatrosses. Marine Biology http://dx.doi.org/10.1007/s00227-011-1873-6
January 12th, 2012 at 9:28 am
Love it! There’s also an excellent sequence in Blue Planet’s Open Ocean episode that shows gulls picking at penellids on the flanks of a much larger Mola basking at the surface. Just for fun, Mola holds at least four parasite records that I know of. 1. Most parasite species in a single fish species 2. Biggest copepod (Penella) 3. Biggest skin fluke (Capsala martineri, about the size of a silver dollar) and 4. longest worm, Nematobothrioides, which winds through their flesh and can be 40 or more feet long (but no-one really knows because its so hard to dissect them out intact)
January 12th, 2012 at 12:34 pm
Ocean sunfish (the Hawaiian name, mola mola, is also excellent) are one of the most charming and spectacular fish in the ocean – they’ll come right up to a ship and flap about on the surface, looking at you with their calm fishy eyes. I wonder now if they are waiting for the ship to nibble off the parasites? After a while they look disappointed and dive off into the blue.
January 12th, 2012 at 12:43 pm
A little gross and definitely fascinating! (I think that should be part of the definition for parasites). Plus, I had never seen or heard of ocean sunfish. What a crazy, fantastical creature!
Thanks for continuing to keep your scientific sense of wonder alive and for passing it along in such an engaging, readable way to your readers. Your enthusiasm is infectious.
January 12th, 2012 at 3:59 pm
Wow, that was one of the most informative comments I’ve read! Thanks! (Grossed me out too…)
January 14th, 2012 at 10:04 pm
I thought this was common knowledge that birds clean molas. This has been documented a lot. Plus many different kinds of fish clean them, eating various parasites from various parts of the sunfish bodies. I know they have multiple parasites but I thought the number known to science was less than 50. Anyway, nice read. They are truly unusual creatures and a joy to encounter under the sea.
February 1st, 2012 at 9:42 pm
The biggest one ever found was 2.7 metres in length and weighed 2.3 tonnes
Biggest ever weighed, they can grow to at least 3.32 meters.
Fish have skeletons that are either made of cartilage, as in sharks and rays, or bone, as in all the others.
Molids skeletons actually are almost entirely cartilaginous.