Top Ten Sharks #5 – The Megamouth Shark, Megachasma pelagios

The elusive and mysterious megamouth shark, one of only three known filter-feeding species of shark and the one least known to us. (Credit: Wikimedia Commons via Australian Geographic)

To start with, that Latin name! Megachasma pelagios – If I’m not getting my tongue twisted does that not translate as ‘giant cave of the deep’?

Anyway, I’ll be honest, I know next to sod all about the megamouth shark. Any marine biologist worth a damn, who isn’t specifically researching the megamouth shark right now, should tell you the same thing. If they don’t, they’re a liar.

It is one of only three known filter feeding sharks, the others being the basking shark and the whale shark. It belongs to the unique family Megachasmidae – although there is some suggestion it should go in the Cetorhinidae with the basking shark. It is the only extant member of its genus, Megachasma, although there are at least two hypothesised fossil members.

It has a very unique look, like someone took a regular sort of shark and…squashed it and stretched it. They can get pretty sizeable, around 5m for a female, 4m for a male – maximum size is probably in the 6m range but, as mentioned…we don’t know.

A preserved megamouth shark. At one point there was a lot of discussion about their teeth and exposed gums. They are highly reflective, and it was suggested that they may have used ‘photophores’ or light producing cells, to use them to attract prey but this has, I think, since been disproved. Quite what the use is in the reflectiveness of this tissue is still up for debate, whether that has an attractive property for prey or is used to signal other megamouths are the two most widely accepted hypotheses. (Credit: GordonMakryllos CC-BY-SA 4.0)

Why don’t we know?

It was only first discovered in 1976.

Now it’s not unusual for new species to be discovered in our oceans. We don’t swim in them, all over the place, 24/7 like we do on our land. The seas are teeming with mysteries. The thing is most of the shark and fish we discover are either really, really deep (like thousands of km deep) or are quite small.

This is a giant thing that has a vertical migration between around 1,000m to the surface level, depending on where its food source, the plankton, is.

Since its discovery in 1976, according to Google a total of 16,148 days (if counting from 31 Dec. 1976) there have been around 100 encounters with the megamouth shark. To put it into even more perspective, even if we’re very West-centric, and we say since the damn of Western academic enquiry rising up in the Hellenic world, in Anthenian culture, for example, at its peaks around the mid 400s BCE, then in nearly 2,500 years of human observation of the natural world we’ve only see this creature around 100 times – Incredible.

It’s a lethargic beast, that’s for sure. A specimen caught off of California was tagged and released where it made vertical migrations between 160m and 12m and moved at an average rate of between 1.5-2.1km/h. I’m fairly certain that’s about half of my ‘deliberately slow’ pace for walking.

A very rare video of a megamouth shark swimming off the coast of Indonesia’s Komodo Island.

Like a lot of other sharks it is ovoviviparous – the female lays eggs within herself, develops them until they hatch and then gives birth. Studies of the genomes of dissected specimens from around the world exhibit low genetic diversity – suggesting they are not discrete populations but a dispersed, migratory, interbreeding population.

That’s about it.

That’s kind of all we know.

So what’s the point? Why is this number 5 on our list? Surely the great white could have been bumped higher!?

Well hold your horses.

Because I chose the megamouth to go here for what it tells us about what we don’t know, more than what it tells us about what we do.

We are land animals. We evolved on land, from land-based ancestors going back hundreds of millions of years now, to have land-adapted, land-based thoughts in our land-based brains. That deep blue world out there is as alien to us as the Moon or Mars. Yeah, okay, we can swim, we can dive, we can send submersibles but that doesn’t make it less alien.

There is much we need to learn about life, and about life in the oceans even more so.

A map of our world (not to scale, it’s been flattened which leads to some landmasses becoming distorted) but it gives you a good idea of how dominant the Big Blue really is. I’m not even sure how many large, inland lakes are included on this map. We are an aquatic planet above all else. (Credit: Adapted from VardionCC-BY-SA 3.0)

To some extent those seas are our mother-medium, the place where all life once started, before it learned to grow a body, before it gained meaningful senses, before it sprouted, before it grew tendrils and roots, before it grew limbs, it was afloat on those salty waves.

There is something terrifying about it to us, and I think it is that unknown, that mystery and possibly on some deep, genetic level, the idea that we ‘escaped’ – because it can appear to be a dread world down there. It can seem an empty, dark void.

But it isn’t. The seas and the oceans are (Sometimes literally) aglow with life, teeming with it, bursting at the seams with it, not merely in the photic zone, either, not even just where the sun’s light touches, but in the depths, in the deepest depths. There are entire ecosystems powered without the sun, chemotrophic, in those depths. I talked about them in my Introduction to Biology that nobody read (possibly because it was grimly subtitled ‘Grow, Fuck, Age, Die!’)

A whole new system of ‘trophy’ of eating, found by the hydrothermal vents near to the darkest depths of our oceans. The chemical outpouring from those vents feeds miscroscopic life, bacteria and archaea, that convert the chemicals into energy, to be consumed by, or work symbiotically with, other lifeforms to form a whole new food-web. Far from being barren and desolate for lack of sunlight, our ocean floors are actually teeming with life. (Credit: Credit: NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011 – Public Domain)

Our lives are lived very self-centrically. We are, by the nature of our psychology, the centre of our own world. Biologically, if we believe selfish gene theory, if we believe community theories, kin selection theories, we have a hierarchy of priorities from self to our family, to our extended family and friends, our towns, our cities, countries, allied countries, our human world and only once we can extend our minds and our concerns beyond the self-interest of our own species can we recognise quite how much ‘other’ there is. We are all the minority.

To us the human world seems like everything, but we don’t even cover 100% of the land on this planet, and that land barely covers 30% of the surface of our planet.

The life in the seas owns the majority stake in Earth, and there are 15 foot long sharks that weren’t discovered, for the very first time, until 1976!? What else is out there!? What more don’t we know!?

Images of the initial ‘discovery’ of the megamouth shark in 1976. I believe it was accidentally caught on the anchor of a US Navy vessel off Hawai’i (Credit: US Navy and Leighton Taylor – Used without permission)

I put the Megamouth here because it is a stark reminder to us, as people, as scientists, as biologists, as philosophers, as whatever you may be – There’s more we don’t know than there is we do, about everything. Not just the seas, this planet, our ecosystems, the species on it, our nearest relatives, even our own damn selves. There are deeper questions to be asked, the answers to which merely pose more questions!

It is where it is because it is effectively the poster-shark of We Lack Discipline, reminding us all of how ignorant we truly are, how little we actually know and why we must all remain, with a humble heart, but youthful energy, an exuberant, pioneering spirit for knowledge.

We must always be the Curious Idiot™.

Want to dive deeper into some aquatic shark content?
Our Introduction will give you the basics of shark biology, ecology and natural history.
#10 – The massive, magnificent megalodon – a prehistoric giant!
#9 – The beautiful and quick blue shark
#8 – Known for it’s spiral of jagged teeth, Helicoprion – the Buzzsaw shark!
#7 – The frilled shark, a mysterious living fossil with much to tell us about sharks past.
#6 – The Great White, Apex predator, whale scavenger, more intelligent than we thought.

#4 – The Graceful Hammerhead family – Much overfished, and is one a veggie?
#3 – The aparently philosophical basking shark! – Happy just existing.
#2 – The longest living vetebrate on earth – The Greenland Shark


Published by Karl Anthony Mercer

Karl Anthony Mercer is a writer, poet, author, musician and part-time dandy. He can often be found squatting in fields looking at insects (he is an unapologetic wasp fanatic), wandering around museums over-dressed, or hiding in a dank corner singing sad songs on a small guitar. His writing on WordPress consists of MercersPoems - an outlet for his poetry often using natural imagery, gothicism and decadence to explore the struggles of living as an autistic person; and We Lack Discipline - Where he writes about factual, often academic topics he has learned and is interested in (e.g. biology, psychology, Roman history etc.) with an inimitable, often light-hearted and irreverant style. You can support Karl by; Subscribing to the We Lack Discipline Patreon - Or buying him a coffee (he loves coffee!) -

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