An Inconvenient Hagfish

On the importance of intermediates.

1280px-eptatretus_stoutii

We think of scientific progress as working like building blocks constantly being added to a growing structure, but sometimes a scientific discovery can actually lead us to realize that we know less than we thought we did. Take vision, for instance. Vertebrates (animals with backbones) have complex, highly-developed “camera” eyes, which include a lens and an image-forming retina, while our invertebrate evolutionary ancestors had only eye spots, which are comparatively very simple and can only sense changes in light level.

At some point between vertebrates and their invertebrate ancestors, primitive patches of light sensitive cells which served only to alert their owners to day/night cycles and perhaps the passing of dangerous shadows, evolved into an incredibly intricate organ capable of forming clear, sharp images; distinguishing minute movements; and detecting minor shifts in light intensity.

584px-diagram_of_eye_evolution-svg
Schematic of how the vertebrate eye is hypothesized to have evolved, by Matticus78

In order for evolutionary biologists to fully understand when and how this massive leap in complexity was made, we need an intermediate stage. Intermediates usually come in the form of transitional fossils; that is, remains of organisms that are early examples of a new lineage, and don’t yet possess all of the features that would later evolve in that group. An intriguing and relatively recent example is Tiktaalik, a creature discovered on Ellesmere Island (Canada) in 2004, which appears to be an ancestor of all terrestrial vertebrates, and which possesses intermediate characteristics between fish and tetrapods (animals with four limbs, the earliest of which still lived in the water), such as wrist joints and primitive lungs. The discovery of this fossil has enabled biologists to see what key innovations allowed vertebrates to move onto land, and to precisely date when it happened.

There are also species which are referred to as “living fossils”, organisms which bear a striking resemblance to their ancient ancestors, and which are believed to have physically changed little since that time. (We’ve actually covered a number of interesting living fossils on this blog, including lungfish, Welwitschia, aardvarks, the platypus, and horseshoe crabs.) In the absence of the right fossil, or in the case of soft body parts that aren’t usually well-preserved in fossils, these species can sometimes answer important questions. While we can’t be certain that an ancient ancestor was similar in every respect to a living fossil, assuming so can be a good starting point until better (and possibly contradictory) evidence comes along.

So where does that leave us with the evolution of eyes? Well, eyes being made of soft tissue, they are rarely well preserved in the fossil record, so this was one case in which looking at a living fossil was both possible and made sense.

Hagfish, which look like a cross between a snake and an eel, sit at the base of the vertebrate family tree (although they are not quite vertebrates themselves), a sort of “proto-vertebrate.” Hagfish are considered to be a living fossil of their ancient, jawless fish ancestors, appearing remarkably similar to those examined from fossils. They also have primitive eyes. Assuming that contemporary hagfishes were representative of their ancient progenitors, this indicated that the first proto-vertebrates did not yet have complex eyes, and gave scientists an earliest possible date for the development of this feature. If proto-vertebrates didn’t have them, but all later, true vertebrates did, then complex eyes were no more than 530 million years old, corresponding to the time of the common ancestor of hagfish and vertebrates. Or so we believed.

hagfish
The hagfish (ancestors) in question.  Taken from: Gabbott et al. (2016) Proc. R. Soc. B. 283: 20161151

This past summer, a new piece of research was published which upended our assumptions. A detailed electron microscope and spectral analysis of fossilized Mayomyzon (the hagfish ancestor) has indicated the presence of pigment-bearing organelles called melanosomes, which are themselves indicative of a retina. Previously, these melanosomes, which appear in the fossil as dark spots, had been interpreted as either microbes or a decay-resistant material such as cartilage.

This new finding suggests that the simple eyes of living hagfish are not a trait passed down unchanged through the ages, but the result of degeneration over time, perhaps due to their no longer being needed for survival (much like the sense of smell in primates). What’s more, science has now lost its anchor point for the beginning of vertebrate-type eyes. If an organism with pigmented cells and a retina existed 530 million years ago, then these structures must have begun to develop significantly earlier, although until a fossil is discovered that shows an intermediate stage between Mayomyzon and primitive invertebrate eyes, we can only speculate as to how much earlier.

This discovery is intriguing because it shows how new evidence can sometimes remove some of those already-placed building blocks of knowledge, and how something as apparently minor as tiny dark spots on a fossil can cause us to have to reevaluate long-held assumptions.

Sources

  • Gabbott et al. (2016) Proc. R. Soc. B. 283: 20161151
  • Lamb et al. (2007) Nature Rev. Neuroscience 8: 960-975

*The image at the top of the page is of Pacific hagfish at 150 m depth, California, Cordell Bank National Marine Sanctuary, taken and placed in the public domain by Linda Snook.

The Cost of Colour

or, the fading world at the tip of your nose.

Sobo_1906_324Try to imagine a colour you’ve never seen. Or a scent you’ve never smelled. Try to picture the mental image produced when a bat uses echolocation, or a dolphin uses electrolocation. It’s nearly impossible to do without referring to a previous experience, or one of our other senses. We tend to tacitly assume that what we perceive of the world is more or less all there is to perceive. It would be closer to the truth to say that what we perceive is what we need to perceive. Humans don’t require the extraordinary sense of smell that wild dogs do in order to get by in the world. But it wasn’t always this way.

Scent molecules are picked up and recognized in our noses by olfactory receptors. Each type of receptor recognizes a few related types of molecules, and each type of receptor is written into our DNA as an olfactory receptor (OR) gene. In mammals, OR genes make up the largest gene family in our genome. There are over a thousand of them. Sadly for us, over 60% of these genes have deteriorated to the point of being nonfunctional. Why? In what must be a hard piece of news for X-Men fans, extra evolutionary features tend not to hang around unless they’re actively helping us to survive longer and breed more. If a gene can develop a fault that makes it useless without causing its host a major competitive disadvantage, it’ll eventually do so, and an incredible number of these broken genes – called “pseudogenes” – have built up and continue to sit in our genome. This isn’t specific to humans; cows, dogs, rats, and mice all have about 20% of their OR genes nonfunctional. But that still works out to a difference of hundreds of different types of scents that we can’t detect. Even compared to our closest relatives, the apes and old world monkeys, we have twice as many OR pseudogenes, and are accumulating random mutations (the cause of pseudogenes) at a rate four times faster than they are. This is all quite logical, of course; humans have evolved in such a way that being able to smell prey or potential mates from a distance just isn’t key to our survival.

Phylo tree image
From: Gilad et al. (2004) PLoS Biology 2(1): 0120

What’s more interesting is that when scientists looked at the OR genes of apes and old world monkeys (OWMs), they found elevated rates of deterioration there, too… about 32%, compared to only 17% in our next closest group of relatives, the new world monkeys (NWMs). So what happened between the divergence of one group of primates and the next that made an acute sense of smell so much less crucial? The answer came with the one exception among the NWMs. The howler monkey, unlike the rest of its cohort, had a degree of OR gene deterioration similar to the apes and OWMs. The two groups had one other thing in common: full trichromatic vision. Nearly all other placental mammals, including the NWMs, are dichromats, or in common parlance, are colourblind. Using molecular methods that look at rates of change in genes over time to determine when a particular shift happened, scientists determined that in both instances of full colour vision evolving, the OR genes began to deteriorate at about the same time. It was an evolutionary trade-off; once our vision improved, our sense of smell lost its crucial role in survival and slowly faded away. In apes and monkeys, this deterioration process seems to have come to a halt – at a certain point, what remains is still necessary for survival – but in humans, it is ongoing. We know this because of the high number of OR genes for which some individuals carry functional copies, and some carry broken copies. This variability in a population, called polymorphism, amounts to a snapshot of genes in the process of decay, since the broken copies are not, presumably, causing premature death or an inability to breed amongst their carriers. So as we continue to pay the evolutionary price for the dazzling array of colours we are able to perceive in the world, our distant descendants may live in an even poorer scentscape than our current, relatively impoverished one. There may be scents we enjoy today that will be as unimaginable to them as the feel of a magnetic field is to us.

As a quick final point, it turns out humans aren’t the only animal group to have undergone a widescale loss of OR genes. Just as full colour vision made those genes unnecessary for us, so moving into the ocean made them unnecessary for marine mammals. In an even more severe deterioration than that seen in humans, some whales and porpoises have nearly 80% OR pseudogenes. As you may already know, whales, dolphins, and other marine mammals evolved from land-dwelling, or terrestrial mammals (want to know more about it? Read my post here). Using methods similar to those mentioned above for primates, researchers found that at about the same time they were adapting anew to life in the ocean, their scent repertoire was beginning to crumble. And since anatomical studies show that the actual physical structures used to perceive scent, such as the olfactory bulb in the brain, are becoming vestigial in whales, it’s likely the loss isn’t finished yet. Interestingly, the researchers behind this study also looked at a couple of semi-marine animals, the sea lion and the sea turtle, which spend part of their time on land, and found that they have a sense of smell comparable to fully terrestrial animals, with no increased gene loss.

The widescale and ongoing loss of the sense of smell in certain animals, particularly ourselves, is a nice illustration of an evolutionary principle which can be summarized as “use it or lose it”, or more accurately, “need it or lose it.” We tend to think of evolution as allowing us to accrue abilities and features that are useful to us. But unless they’re keeping us and our offspring alive, they’re not going to stick around in the long term. Which makes you wonder, with humans’ incredible success in survival and proliferation on this planet, which relies overwhelmingly on our cognitive, rather than physical abilities, what other senses or abilities could we eventually lose?

Sources

*The image at the top of the page comes from Sobotta’s Atlas and Text-book of Human Anatomy (1906 edition), now in the public domain.

Randomly Assembled and Surprisingly Dangerous: The Platypus

(Via: National Geographic)

Common Name: The Duck-Billed Platypus

A.K.A.: Ornithorhynchus anatinus

Vital Stats:

  • Only species of Family Ornithorhynchidae
  • Males average 50cm (20”) long, females 43cm (17”)
  • Weigh between 0.7 and 2.4kg (1.5 – 5.3lbs.)
  • Body temperature of 32 degrees Celcius; five degrees lower than placental mammals
  • Live up to 17 years in captivity
  • Eat freshwater crustaceans, worms, and insect larvae

Found: Eastern Australia and Tasmania

It Does What?!

Besides looking like it was assembled from spare parts? We’ve all seen pictures of platypuses (yes, “platypuses”, not “platypi”) before, and everyone knows what total oddities they are: the duck-like bill, the beaver-esque tail, the fact that they lay eggs, despite being mammals; but behind these weird traits lie… even more weird traits! So let’s take a moment to appreciate the lesser-known eccentricities of the platypus, shall we?

First off, these cuddly looking freaks are actually dangerous. Male platypuses have a spur on each hind foot which is filled with a venom powerful enough to kill a large dog. While it isn’t enough to take out a human, it does cause severe, incapacitating pain whose after-effects can last for months. One of only a very few venomous mammals, the male’s venom production increases during the breeding season, suggesting its purpose may lie in competition with other males.

Why your dog and your platypus shouldn’t play together.
(By Jason Edwards, via: How Stuff Works)

And speaking of breeding, reproduction in platypuses isn’t exactly ‘mammal standard’, either. Unlike all other mammals, which have two sex chromosomes (X and Y; XX for females, XY for males, with rare exceptions), the platypus has ten. Talk about evolutionary overkill. A male platypus has the pattern XYXYXYXYXY, while a female has ten Xs. Researchers have found that the actual genetic structure of these sex chromosomes is actually more similar to birds than mammals, although 80% of platypus genes are common to other mammals.

After this alphabet soup of chromosomes arranges itself, up to three fertilised eggs mature in utero for about four weeks; much longer than in most other egg-laying species (in birds, this may be only a day or two). Once laid, the eggs are only about the size of a thumbnail, and hatch in around ten days. While platypuses produce milk, they don’t actually have proper teats to suckle their babies- the fluid is released from pores in the skin. A small channel on the mother’s abdomen collects the milk, which is then lapped up by the young. Strangely, the babies are actually born with teeth, but lose them before adulthood. Such is the impracticality of platypus design…

Adorably impractical.
(Via: noahbrier.com)

Finally, let’s explore platypus hunting methods. Platypuses are the only mammals with the sixth sense of electroreception. Those leathery duck bills of theirs are actually precision receptors that can detect the electric fields created in the water by the contractions of muscles in their prey. Considering the prey in question is largely worms and insect larvae, we’re talking big-time sensitivity here. The bill is also very receptive to changes in pressure, so a movement in still water can be picked up in this way as well. Researchers have suggested that by interpreting the difference in arrival time of the pressure and electrical signals, the hunter may even be able to determine the distance of the prey. This would be especially useful, given that platypuses close both their eyes and ears when hunting. In fact, they won’t even eat underwater; captured food is stored in cheek pouches and brought to land to be consumed.

So there you have it. The platypus: even weirder than you thought.

[Fun Fact:The female platypus has two ovaries, but only the left one works.]

Intelligent Design’s Worst Nightmare
(Via: Animal Planet)

Says Who?

  • Brown (2008) Nature 453: 138-139
  • Grant & Fanning (2007) Platypus. CSIRO Publishing.
  • Graves (2008) Annual Review of Genetics 42: 565-586
  • Moyal (2002) Platypus: The Extraordinary Story of How a Curious Creature Baffled the World. Smithsonian Press.

What’s the matter, louse got your tongue? (Cymothoa exigua)

Via: Parasite of the Day

Common Name: The Tongue-Eating Louse

A.K.A.: Cymothoa exigua

Vital Stats:

  • Females are 8-29mm long by 4-14mm wide (0.3”-1.1” x 0.16”-0.55”)
  • Males are 7.5-15mm long by 3-7mm wide (0.3-0.6” x 0.12”-0.28”)
  • Preys on 8 species of fish from 4 different families

Found: In the Eastern Pacific, between the Southern U.S. and Ecuador

It Does What?!

With a name like “Tongue-Eating Louse”, you know this is going to be viscerally horrible, but bear with me… it’s also pretty neat. Despite the name, these aren’t actually lice, but parasitic crustaceans known as isopods. While there are dozens of species in the genus Cymothoa, most are parasites which live in the gills of fish and are, relatively speaking, unremarkable. But Cymothoa exigua is something special. While the male of the species (and this is a slippery term, as they can change sex when necessary) lives in fish gills, the female has developed an altogether original strategy.

Try to enjoy a tuna sandwich now.
Via: Smithsonian.com

Entering through the gills, the female takes up a position at the back of the fish’s mouth and attaches herself to the base of its tongue. She then pierces the tongue with her front appendages and begins to consume the blood inside it. Over time, the lack of bloodflow causes the tongue to slowly wither up and fall off. What’s left is a stump consisting of about 10% of the original tongue (yes, someone measured this). The parasite can now attach herself to the stump using her seven pairs of hook-like pereopods (read: ‘feet’) and actually begin to function as the fish’s tongue.

What’s really amazing is how well this seems to work. The parasite has evolved a body shape which closely matches the curves of the inside of the host’s mouth. Unlike our tongues, a fish tongue has no real musculature or flexibility; its only real function is to hold food against the fish’s teeth. With the parasite in place, the host is able to use its body to do exactly that. While the isopod is thought to feed on the fish’s blood, researchers have found that infected hosts have normal body weights and typical amounts of food in their digestive tract when caught. This is, to date, the only known case of a parasite functionally replacing an organ in its animal host.

Once it’s in there, this thing’s not coming out without a fight.
Via: This Site

Because edible snapper fish are amongst the host species of C. exigua, there have been cases of the parasite showing up in people’s supermarket purchases, including one person who thought they had been poisoned after eating one. So are they dangerous? Not to eat, no, but researchers tell us they can give a nasty little bite, given the opportunity. So the moral of this story is: if you bring home a fish for dinner and see an evil-looking parasite posing as its tongue… don’t stick your finger in its mouth.

.

Says Who?

  • Brusca & Gilligan (1983) Copeia 3: 813-816
  • Brusca (1981) Zoological Journal of the Linnean Society 73(2): 117-199
  • Williams & Bunkly-Williams (2003) Noticias de Galapagos 62: 21-23
See you in your nightmares.

Advertising in the Wild… Not So Very Different (Ophrys sp.)

(Via: lastdragon.org)

Common Name: Bee Orchids

A.K.A.: Genus Ophrys

Vital Stats:

  • 30-40 recognised species in the genus
  • Grows to a height of 15-50 cm (6-20”)
  • The name Ophrys comes from a word meaning “eyebrow” in Greek, for the fuzzy edges of the petals
  • First mentioned in ancient Roman literature by Pliny the Elder (23-79 A.D.)

Found: Throughout most of Europe and the British Isles

It Does What?!

We tend to think of animals (including humans) as using plants to serve our ends exclusively- we eat them, clothe ourselves with them, build homes with them, and so on. But for all the obvious ways in which the animal kingdom takes advantage of the plants, there are numerous, more subtle, ways that they use us to do their bidding. One of those ways is as pollinators; plants enlist animals to help them reproduce. And while that enlistment often takes a rather mundane form – a bit of pollen brushed onto a bird’s head as it sips nectar, say – sometimes a group of plants will get a bit more creative about it. Such is the case with the bee orchids.

These highly specialised flowers depend on very specific relationships with their pollinators; often only a single species of bee (or wasp, in some cases) will pollinate a given species of orchid. Without those pollinators, the orchids can’t produce seed and would die out. So how do you control a free-roving creature that has other places to be? Why, sex, obviously. (Isn’t that the basis of most advertising?) The bee orchid has evolved a flower that not only looks, but smells like a virgin female of the bee species which pollinates it.

May not be appropriate for younger readers.
(Via: This Site)

At a distance, the bee detects the pheromones of a receptive female. Once he moves in closer, there she is, sitting on a flower, minding her own business. So he flies in and attempts to do his man-bee thing, only to find that he’s just tried to mate with a plant. Mortified (I imagine), he takes off, but with a small packet of pollen stuck to his head. He’s memorised the scent of this flower now and won’t return to it, but amazingly, the orchids vary their scent just slightly from one flower to the next, even on the same plant, so that the duped bee can never learn to distinguish an orchid from a female. What’s more, because the scent is more different between plants than between flowers on the same plant, he is more likely to proceed to a different plant, decreasing the chances that an orchid will self-fertilise.

Hilariously, researchers have shown that, due to their higher levels of scent variation compared to true female bees (variety being the spice of life, right guys?), male bees actually prefer the artificial pheromones of the orchids over real, live females. In experiments where males were given a choice between mating with an orchid and mating with a bee, they usually chose the flower, even if they had already experienced the real thing.

So there you have it. Plants: master manipulators of us poor, stupid animals.

Who could resist?
(Via: Wikia)

Says Who?

  • Ayasse et al. (2000) Evolution 54(6): 1995-2006
  • Ayasse et al. (2003) Proceedings of the Royal Society, London B. 270: 517-522
  • Streinzer et al. (2009) Journal of Experimental Biology 212: 1365-1370
  • Vereecken & Schiestl (2008) Proceedings of the National Academy of Science 105(21): 7484-7488
  • Vereecken et al. (2010) Botanical Review 76: 220-240

Sea Cucumbers, or, How to Really Lose Weight Fast

Via: www.starfish.ch

Common Name: Sea Cucumbers, Holothurians

A.K.A.: Class Holothuroidea

Vital Stats:

  • Approximately 1250 species
  • Size: 2-200cm (¾” to 6.5’)
  • Lifespan: 5-10 years in the wild

Found: Throughout the oceans, in both shallow and very deep regions

It Does What?!

Where to begin? This is an odd one… To start, despite the name sea cucumber, this isn’t a plant but an animal; a relative of starfish and sea urchins. One could be forgiven for mistaking the holothurians for plants, however. Most spend their lives lying on the ocean floor, looking like a sunken vegetable, and covering a distance of a couple metres or less per day in their search for food. The creatures feed on small particles, like algae and plankton. There is a tiny mouth at one end of their body, surrounded by between eight and thirty tentacle-like feet with which they grab their food and which can actually be retracted into their mouth. But that’s not really the interesting end of a sea cucumber, as we’ll see.

Via: www.answers.com

Lacking both eyes and any rapid means of locomotion, holothurians are tempting prey for crabs, fish, and other large sea creatures. When threatened, they have the single most bizarre and seemingly impractical defence mechanism ever evolved: self-evisceration. As a predator approaches, the sea cucumber violently contracts the muscles around its body wall and actually expels its own internal organs via its anus (demurely labelled as the ‘aboral pole’ in the diagram). Yes, really. In some species, these organs include most of the creature’s respiratory system, which takes the form of sticky threads that blanket and ensnare the predator. And just to add genuine injury to the insult, this discharge is accompanied by a toxic chemical known as holothurin, which kills whatever’s nearby. Disgusting, but effective. Once expelled, the missing organs can be regenerated in 1-5 weeks, depending on the species. Some researchers speculate that this ability may even be used as a means of ridding the organism of accumulated waste or parasites. The ultimate detox regime, if you will.

Are those your lungs, or are you just happy to see me?
Via: Wikimedia Commons

One such parasite is the pearl fish. You see, holothurians actually breathe through their rear end as well, so when one of them, umm… opens up… to take in some fresh, oxygenated water, in goes the fish, which then feeds on the sea cucumber’s internal organs. You can see why they might want to rid themselves of this visitor.

Strange as it all seems, the sea cucumber’s strategy is quite a successful one. At depths below five and a half miles (8.8km), they make up fully 90% of the mass of all macrofauna (i.e. any animal that’s not microscopic). Among the species that live at shallower depths, populations can reach a density of 1000 cucumbers per square metre. And it’s a good thing, because they’ve got one predator with whom spewing out their guts won’t work: humans. Sea cucumbers are a popular ingredient in Chinese and other Southeast Asian cuisines, although only about ten species are used for this purpose. These species are farmed commercially in artificial ponds, and are also used in traditional Chinese medicine. Perhaps not surprisingly, they are considered to improve male sexual health.

Does a Body Good.
Via: www.theworlds50best.com

[Fun fact: Sea cucumbers have a body wall made up of collagen fibres which they can ‘unhook’ at will, essentially liquefying their interiors and allowing them to squeeze into very small cavities as a means of hiding from predators. Once inside the cavity, they re-solidify themselves, making the creature very difficult to extract from its hideout.]

Says Who?

If the Eyes are the Window to the Soul, this Fish has a Sunroof

Things are lookin’ up

Common Name: Barreleye Fish

A.K.A.: Macropinna microstoma  (and related species)

Vital Stats:

  • Size: 15cm (6″) long
  • Depth: 600-800m (2000′-2600′) below sea level
  • Discovered: 1939
  • First Photographed: 2008

Found: Subarctic and Temperate regions of the North Pacific

It Does What?!

As you have likely already noticed, fish don’t have necks. At least not in the sense that they are able to look upward. So for a bottom-dweller lurking about in the cold depths of the ocean, being able to see that tasty bit of food floating by above is something of a problem. Some species get around this issue by floating vertically in the water so their whole bodies are pointing upwards. Simple enough. But in the spirit of meeting every challenge with an impossibly bizarre solution, nature has also produced a fish with eyes directly on the top of its head. After all, why re-orient the entire fish when you can just shift a couple of parts?

Those things on the front that look like eye sockets?
That would be its nose.

But the strangeness of the Barreleye Fish goes a little further than that. These aren’t just normal fish eyes in an unusual location. This species’ main prey are jellyfish and their relatives, which frequently come equipped with stingers that could damage the eyes of most predators. So rather than a normal spherical eye perched on top of its head, Macropinna has a tubular structure with the lens buried deep within its head (the dark green areas in the images). Overlying the tubular eyes is a tough, fluid-filled, transparent shield which the fish can look through. That’s right, it looks through the top of its own head. This way, stings from jellyfish will never damage the delicate ocular tissue.

What’s more, the fish’s unique tubular eyes are supremely adapted for the dark depths of the ocean. They allow unusually accurate depth perception (due to a large overlap of the two visual fields) and enhanced light gathering compared the spheroid eyes. In an environment up to 2600 feet (800m) down, where little daylight penetrates and everything appears in monochrome, these adaptations enable the barreleye to distinguish even faint shadows and silhouettes moving above it, and to precisely gauge how far up they are.

The Barreleye Fish, failing to look at the camera.

Researchers had long been puzzled as to how the barreleye eats, since, with its eyes on top of its head, its visual field didn’t include the area around its mouth. The species has been known since 1939, but only as small mangled bodies caught up in deep-sea fishing nets (adults are only about six inches long). In each case, the transparent casing of the fish’s head had been destroyed by the nets and the rapid changes in pressure as the nets were pulled up, making its anatomy difficult to study. In 2008, however, scientists from the Monterey Bay Aquarium Research Institute sent remote operated vehicles with cameras down to try, for the very first time, to snap some photos of these oddballs in action. What they learned was that, when it spots prey, the barreleye can actually rotate its entire tubular eye downward, like moving the telescope in an observatory. This way, it can turn and look at its target straight on as it pursues. Most of the time, though, the fish was seen to use its large, flat fins to hold itself nearly motionless, looking up through its personal sunroof, just waiting for some unlucky jellyfish to float on by.

Says Who?

  • Robison & Reisenbichler (2008) Copeia 4: 780-784.
  • Monterey Bay Aquarium Research Institute

All images taken by the Monterey Bay Aquarium Research Institute (MBARI)