We mostly focus on freshwater here, but I want to take a minute or two to introduce a peaceful giant of the sea: The Ocean Sunfish (Mola mola). 

molamola by per ola norman
Above: An Ocean Sunfish (Mola mola) - By Per-Ola Norman (Own work) [Public domain], via Wikimedia Commons


The Mola mola is found in the order Tetraodontiformes – a fancy term for the group that contains fish such as the pufferfish, triggerfish, boxfish (and, of course, the ocean sunfishes). The cool thing about this order is that they split from other fish around 80-195 million years ago1, which means they have no close relatives and have evolved many special adaptations that make them the strange looking creatures they are today.

Many fish have special adaptations, and a lot of these are not all visibly obvious. Although, his isn’t the case for the Mola mola, as you may notice when looking at them. Compared to our small aquarium fishes, the M. mola can reach a whopping 2.3 tonnes, with a length of 2.7 metres2 - that’s the size of a (very small) elephant! However, less elegant than an elephant, the Ocean Sunfish lacks a caudal (tail) fin, replaced by a ‘pseudotail’ called a clavus. The dorsal (top) fin is so large that people may mistake fish swimming at the surface for sharks, and is used alongside the anal (bottom) fin for most of its motion - giving it a speed of 3.2km/h3. Much like pufferfish, its teeth are also fused to form what’s often called a beak - which they cannot actually close!


1024px mola mola skelett naturhistorisches museum wien
Above: A skeleton of the Mola mola at the Natural History Museum, Vienna - By Sandstein (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons


Starting out at a tiny 0.25cm larva, this fish can grow up to 60 million times in size3, gaining up to 0.82kg per day4. What do they have to eat to gain this kind of weight? Mostly jellyfish and zooplankton (with the occasional sponge, squid, eel larvae and small fish thrown in). The female Ocean Sunfish can also lay 300 million eggs in one go - with this, it’s seems pretty safe to assume that these guys have their fair share of predators,  seeing as we aren't overrun by these plate-shaped giants! Predators of the Mola mola include sea lions, orcas, large sharks, and of course - humans.

Despite their size, the Mola mola is considered a peaceful fish (provided you aren’t a jellyfish, of course). Whilst I’m not a huge fan of approaching aquatic life so closely, this video shows the gentle giant swimming alongside a group of divers. For those who aren’t keen on searching the depths of the oceans for the chance to see one of these guys, I end this article with a rather upbeat video of a small Mola mola feeding from the Monterey Bay Aquarium in California, a favourite Youtube channel of mine. I hope to see an Ocean Sunfish for myself one day, but for now, videos will have to do!