Mobula Rays Profile
Devil rays get all the attention. Once known by their genus name, Manta, these enormous flappy sea animals can grow to 7 metres across and appear to have the largest relative brain-to-body size of any fish.
But they share a family with a lesser-known genus of rays, the Mobula rays.
Similarly gentle and giant, this genus still has a lot to teach us about intelligent life in the oceans, and in a move that should expedite their research, this genus has now engulfed the Mantas entirely.
Mobula Rays Facts Overview
| Habitat: | Marine |
| Location: | Mostly tropical and subtropical waters, sometimes temperate |
| Lifespan: | Possibly up to 75 years |
| Size: | Up to 5.2 m (17 ft) across |
| Weight: | Up to 3,000 kg (6,600 lb) |
| Colour: | Black on top, white underneath |
| Diet: | Zooplankton |
| Predators: | Sharks, orcas |
| Top Speed: | 35 km/h (22 mph) |
| No. of Species: | 11 |
| Conservation Status: | Many species are endangered (IUCN) |
Mobula rays were once thought of as distinct from the Mantas, but DNA sequencing has shown that they in fact contain them.
So, the Manta genus is obsolete and there is now only Mobula. It’s great news for the overlooked species, as it demands better assessment, which needs deeper research. And this couldn’t come at a more important time, as many of the species within the genus are now endangered.
Interesting Mobula Rays Facts
1. No such thing as a Manta
There are quite a few subtle morphological differences between the two groups or rays. Mantas have larger horns, or cephalic lobes, and a mouth that sits right on the front of their face.
Mobula rays have longer tails, shorter lobes, and a mouth that sits under the head, like that of a stingray.
Until very recently, this was enough to categorise them as two separate genera, but in 2017 DNA research showed that they’re much more closely related than was thought, and the two genera, Mobula and Manta, were collapsed into just Mobula, with the ex-mantas nesting within the wider Mobula group.
This means that Mobula rays are now the largest rays in the world, and technically they always were.
So, there are still differences between the two groups but they’re still genetically similar enough to share a genus. 1
2. Devil Rays
Rays are a superorder of very flat fish, closely related to sharks. They’re split into four orders: the Torpediniforms, or electric rays; the Rhinoprisitiformes, with weird-looking noses; the Rajiforms, which contain skates and sawfish; and the order known as Myliobatiformes, which contains stingrays, eagle rays and the Mobula rays.
At the family level, Mobulidae contained the Manta and Mobula genera and now only has the latter as the sole genus with eleven species.
Between them, these rays have been called devil rays or flying rays, the former name given in reference to their lobed facial appendages, which direct water toward their mouth while they are swimming around, feeding on plankton. 2
3. Flying Rays
The other nickname comes from their habit of breaching. Even some of the largest Mobula rays do this, flapping their wing-like fins and accelerating to the surface with enough momentum to throw themselves clear of the water.
Sometimes they do this alone, other times they do it in large groups. They can leap up to two meters out of the ocean, splashing back down
Nobody’s quite sure why they do it, but considering how intelligent they likely are, they might just be enjoying themselves.
4. They have warm brains
A network of large and dense blood vessels called the rete mirabile surrounds the brains of these rays, and it’s there to keep the brain warm.
They spend a lot of time basking in the surface waters, but when they’re sufficiently warmed up, Mobula rays are known to embark on deep descents.
Keeping warm blood around the brain helps them stay lucid in the frigid depths, where researchers think the rays forage near the sea bed. This might have something to do with why they’re considered so intelligent, and the giant manta has one of the largest brains of any fish and the largest relative to body size.
Some evidence also suggests that it passes the mirror test – a simple test of whether an animal recognises itself in a mirror that indicates whether it has a sense of self.
5. Some can sting
Some Mobula rays, including the appropriately-named spinetail devil ray, have spines on their tails, similar to those found in stingrays.
Most species don’t have this, and some have one embedded – a vestigial spine that is no longer used. 3
6. They’re elusive
One of the reasons it’s taken so long to realise these rays are all from the same genus is the difficulty in studying them.
The entire ocean system of interactions between surface waters and the deep is not properly understood in general, and Mobula rays are a significant part of this system, supporting various networks of nutrient exchange between levels.
It’s only recently that these rays have been known to embark on deep dives, sometimes as deep as 2 km beneath the surface, well below the ability for easy research!
Only with long-term tracking projects are marine biologists starting to uncover the secrets of these incredible aliens, but there’s still so much to learn, and every passing year creates more urgency. 4
7. And they’re in danger
Several species of Mobula are in a lot of trouble, including the Spinetail, which is threatened, like many of the others, by targeted and untargeted fishing practices.
Being species that like to aggregate, a large net can spell the end for countless rays all at once, but they’re also targeted by spear fishers, especially in the face of rising demand for their gill plates, which are used by ignorant people who don’t know how medicine works.
The majority of the threat though, comes from tuna and other mainstream fisheries, who pull them up by accident while hunting other species.
Mobula Rays Fact-File Summary
Scientific Classification
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Order: | Myliobatiformes |
| Family: | Mobulidae |
| Genus: | Mobula |
Fact Sources & References
- Mark ‘Crowley’ Russell (2017), “No more mantas, only mobulas”, Dive Magazine.
- Manta Trust (2017), “Manta Ray Breaching”, YouTube.
- “Spinetail Devil Ray”, Manta Trust.
- Simon R. Thorrold (2014), “Extreme diving behaviour in devil rays links surface waters and the deep ocean”, nature communications.