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Shark (And Relatives) Week(s) @ the Library: Part II

Welcome back to the Stage of Fish, dear readers! Today I will conclude what I started last week: talking about batoids, aka shark relatives! In particular, I’ll be talking about stingrays, manta rays and electric rays.

Round 1: STINGRAYS

Stingrays have long had a reputation for being dangerous.  This is probably because they have venom-coated barbs on their tails that they will stab you in the leg with if you stomp on them.

However, due to the tragic and unusual death of nature television show star Steve Irwin at the tail of a stingray, reactions to them seem to have to turned to outright fear: while one should never give too much credence to YouTube comments or anything they read on Yahoo! Answers, I have seen far too many comments on batoid-centric videos that called every batoid a “stingray” and treated every “stingray” like it’s a vicious predator out to get them.  This is actually the same way many people tend to talk about sharks, which is also grossly inaccurate, misinformed and has led to negative repercussions for that much-put-upon fish.

Image Credits: Stephen Frink/Getty Images  Justin Lewis/Getty Images  http://animal.discovery.com/fish/stingray/

FACTS:

When a stingray wounds a human, it is out of self-defense, not malice.  I personally think that stabbing whatever creature that is exponentially larger and heavier than me and happens to be standing on my cartilaginous body is a perfectly valid reason for exercising a typically non-lethal defense mechanism.  When you are playing at the beach, please remember that you are in their habitat, not vice versa.  Also:     

Humans are not a food source for stingrays, therefore they are not hunting you; stingrays physically can not eat you. I promise. 

The Elasmodiver, a site that’s been a great resource to me both while writing this entry and just in general for my daily elasmobranch needs, actually has a page set up with information specifically related to this disturbing issue about stingray barbs, how to treat stingray injuries and information about stingrays relevant to beachgoers.  I strongly recommend that everyone visit this if no other link provided here just to combat some of the rampant fear-based misinformation on stingrays that’s floating around.

Like all wild animals (which it is, make no mistake), it is good to treat stingrays with respect: don’t live in terror of them, do take precautions to not step on them (do the Stingray Shuffle!), don’t molest them, etc.

ANOTHER BEEF: YouTube commenters and members of the media are guilty of calling pretty much every batoid a “stingray” all the time.  This is inaccurate and wrong: taxonomically speaking, stingrays must be members of the Dasyatidae family.  There are LOTS of batoids that are not “stingrays”.  Here are some examples of  inaccurate reports about batoids in the media for an object lesson!Many of you may have seen news reports of a “giant stingray” leaping onto a woman in her boat some years ago.  This “giant stingray” is clearly an eagle ray one of the most photogenic (and thus well-known) and large batoids.  Please compare:

An eagle ray. Diamond-shaped body, notice the head shape. Max weight is 230 kg/507 lb (so the average weight is well up there); common            length is 180 cm/5’9″.  Thus the eagle ray that leapt on the woman in the report (reports of the ray’s weight seems to oscillate between 200-300 lbs.) is perfectly   average for its species.  Eagle rays, unlike stingrays, swim a lot and school.  They don’t engage in the same burying behavior, though they will swim near/at the seafloor. And yes, as observed, they leap, sometimes into boats.
A Southern stingray.  Traditional disc-shaped body.  Typically smaller than an eagle ray. Found on sandy bottoms, near reefs, in seagrass beds; not known for leaping like eagle rays, mobulas or mantas.

As you and anyone who has experience with rays can see, the two cannot be confused.  It would be very odd if a stingray, a creature that dwells on the seafloor, randomly jumped into someone’s boat, as opposed to a ray of a species that frequently swims along the surface and is known for jumping.

An eagle ray. Photo credit: http://www.similandiveguide.com/eagle-ray.html

To be fair, I do not expect every person to be able to identify every batoid, but instead of calling an unknown batoid a “stingray” (which is not a generic label.  Sorry, the word “stingray” narrows it down a very specific set of rays!) perhaps they could just call it a ray?  That’s not wrong, unless it’s not a ray.  Which is possible, people call all sorts of things all sorts of wrong names all the time.

I will also take this opportunity to talk about Stingray City, a snorkeling/scuba diving site at Grand Cayman Island known for its stingray population that’s habituated to humans.  If you’re bent on physically interacting with stingrays (which I guess is better than being terrified of them), this might be an option for you.  Many well-known photographs of Southern stingrays are from this site.

Kfulgham84, the author of this image, demonstrates the dangers and temptations of fraternizing with stingrays at Grand Cayman Island.

They are tolerating you, not trying to become your friend: please be respectful towards them.  They are not pets, do not treat them like your cat (unless your cat is a stingray).  I assume that our readership knows better and would behave appropriately around rays, but  some folks who have not been educated about how to behave around tame-ish wild animals do not.

Additionally, many public aquariums (including our own here in the Boston area) have supervised ray & shark interaction areas if you feel the need to physically connect with batoids. In my experience, the most popular species in these tanks tend to be stingrays and cownose rays, as well some species of smaller sharks (epaulette sharks, bamboo sharks, etc).

In conclusion: If you swim with the rays, or happen to encounter them in an unscheduled manner, don’t be That Guy.However, I will talk more about stingrays than just complain about those who do ill by them.  Stingrays can get very large, as attested to in one of the photos up above.

The largest stingrays in the world are the freshwater stingrays that live in the rivers of Thailand, Malaysia and Indonesia.  They are the guys that show up in e-mail forwards from your relatives and websites that feature many exciting animated pop-up ads.

 

Zeb Hogan (the fellow behind the Megafish Project) with H. chaophraya.  Most photos of giant stingrays aren’t too exciting because they live in muddy rivers so it’s just people holding them and them being huge.

They are more formally known as freshwater whiprays and the binomial name is Himantura chaophraya.  Yes, they are stingrays, meaning they have very large barbs on their tails.  National Geographic has covered them as part of their Megafishes Project, which I naturally encourage you to check out because large weird freshwater fish are great.  Jeremy Wade of Animal Planet’s River Monsters also did an episode on them if you enjoy that media modality.

Round 2: MANTAS

The largest ray, mantas are the charismatic megafauna of the batoid world.  Behold their majestic form:

A manta ray smile. Awkward.
The first thing you might notice about manta rays (aside from their size) is how weird they look compared to the standard batoid (omitting the guitarfish, sawfish, etc.) body shape:

       Here are mobulas doing their flying thing off Cabo Pulma:

Also, they school.  A lot.  They are somewhat photogenic.

  • Their eyes are on the sides of their heads.  While this isn’t as weird as the cephalic lobes or the the front-of-the-head mouth (this eye position is also present in eagle rays), stingrays’ eyes are on top of their heads.
  • Like the largest of their non-flattened elasmobranch comrades, the whale shark, manta rays are also filter feeders.  Unfortunately, the manta does not get to sport the natty grid + spots pattern that looks so cool on whale sharks.  Now that I think about it, I’m surprised people don’t kill them to wear their skin, they do it to every other species unfortunate enough to have skin that is aesthetically pleasing to humans.
  • While they are filter feeders, manta rays DO have teeth!  However, they’re for reproductiontime, not for dinnertime.  I actually reviewed this earlier when talking about batoid dentition, so scroll up if you want to see their little poky teeth.
Manta at Sharm-el-Sheikh in Egypt, ©Tim Snell http://www.testmeat.co.uk/photos/index.php?id=745
So how big are these guys?  The maximum recorded size from FishBase claims a 910 cm/29.86 ft for length and 3,000 kg/6,613.9 lb. for weight. That’s 3.3 tons of batoid, by the way. However, FishBase also tells us that mantas are commonly 450 cm/14.8 ft and the sources I could find says average weight is more around 1,360 kg/3,000 lb., a mere 1.5 ton of flattened cartilaginous fish.
1933, y’all.  Also, mini-manta is precious, aside from being dead.
I hate having to say this, but evidence on the Internet compels me: just because you can ride a manta ray doesn’t mean you should. In fact, you shouldn’t.  Why?  Let’s talk about MUCUS.
Any of you who’ve ever touched a fish before know that they’re slimy (scroll down for slime, as interpreted by hagfish).  Fish are slimy due to the protective coating of mucus on their bodies that protects them from infection, harmful organisms and other external badniks.  Touching/handling/stressing fish removes some of this valuable mucus coating, which can injure them and/or make them more susceptible to infection.  Thus, riding a manta would most likely be detrimental to their mucus coating and could possibly outright injure it.

 

Don’t be this person.

Round 3: TORPEDO RAYS, aka ELECTRIC RAYS

What?  A fish with many names?  You don’t say! First, let’s get our etymology on via the Online Etymology Dictionary: the “torpedo” comes from the Latin torpere, meaning to “be numb”. Coincidentally, these guys are also known as “numbfish” or “crampfish” in some quarters.  This is as deep as I’ll go.  The Etymology Dictionary actually provides Proto Indo-European stems so you should be grateful that that isn’t within the purview of this entry, although I actually have an idea for an entry that involves PIE and fish so none of you are truly ever safe.

 

Bullseye electric ray photographed by Andy Murch http://www.elasmodiver.com/bulls-eye_electric_ray.htm
Electric rays (that’s what I’m going to call them IN GENERAL) look a little weird compared to the rest of the rays we’ve covered.  I tend to overgeneralize their body shape as “unfortunate pancakes taped together”.  This diagram provides a better idea of the diversity in electric ray body shapes:

 

Still look like weird pancakes. (Madl & Yip, 2000)

In addition to being pancakeoid, you’ll notice their tails (or more properly, “caudal fins”) more closely resemble those of fish than of stingrays or certainly mantas with their spindly tails. What are they used for?  LOCOMOTION!  Somehow this makes them look even sillier, the guy below vaguely looks like a living metal detector who just happens to be an awesome electric batoid. I doubt he is sympathetic to your gouty toe.

Torpedo Ray at Casino Point (Catalina Island, California), Photo by Nick Ambrose http://californiadiver.com/torpedo-ray/

Electroreception (the biological ability to perceive electrical impulses) is not something unusual to elasmobranchs or to many fish in general; the platypus can do it, why can’t you? Electric rays are unique among rays in that they can both detect and emit electric impulses, an ability that is shared to a lesser extent by skates, though their electroreceptive organs differ in origin, function, strength, and location. Note that skates’ electrical discharges are too weak to be used for defensive or predatory functions.

Let’s break it down taxonomically.  Technically, there’s no such “thing” as an electric ray, given that would imply that there is a single species called “the electric ray”.  That is a blatant falsehood because there are actually about 60 species of rays that emit electricity.

Let me show you, because if you’re going to learn one thing from me it’s ridiculous fish taxonomy.  Let’s do this thing:

Class: Chondrichthyes (Contains Elasmobranchii and Holocephali [chimaerae]) 
     Subclass: Elasmobranchii (It’s a shark or a batoid!)

          Superoder: Batoidea (It’s a batoid!)

               Order: Torpediniformes (Rays that do the electric thing)

Under the order Torpediniformes we get four families of electric ray with four evocative names: Narcinidae, Narkidae, Torpedinidae and Hypnidae.  There may be a suggestion of a naming motif hidden here.  Indeed, electricity-producing rays have been known to humans for a very long time and apparently used to be subject to medical employment.

This 2,300 year old garum (fish sauce) plate from Christies boasts two cephalopods and two batoids.  The batoids are two types of electric ray and the cephalopods are an octopus and a squid.
Scribonius Largus, Emperor Claudius of Rome’s court physician, used electric rays as treatment for headaches and gout.  We know this because he recorded it in his text Compositiones medicae, where he specifically mentions treating people by having them stand in buckets with “live black torpedo fish” circa 50 C.E.  Apparently the physician Galen also thought electric rays were pretty good for this kind of thing, even though it strikes me as rather rude.
The skin is peeled back to reveal the electricity-producing organs.  Engravings from John Hunter’s paper to the Royal Society ©Royal College of Surgeons of England 1. The under surface of a female torpedo 2. The upper surface of a female 3. The under surface of a male

I’ve found allusions to the ancient Greeks using electric rays as a form of anesthesia during childbirth (?!) but no reliable references because the Internet is full of lies.  I have, however, found a letter from a guy doing experiments on electric rays writing to Benjamin Franklin about them in 1772 to tell him that he figured out that BY GOD THEY’RE FULL OF ELECTRICITY, JUST LIKE THAT LEYDEN JAR

Anyway, people have known about them for a while and used them for their busted toes and all kinds of weird stuff, with nary a thought for the ray’s welfare in mind.

BONUS: What do electric eels (which are actually really big knifefish, not eels at all) get for Christmas? Forced labor, depending on how liberal your definition of “labor” is.

So how strong is the shock of the electric ray, anyway? It kind of depends on which electric ray you’re talking about.  As is so often the case with fish records, they vary and FishBase ain’t talking.  The max seems to be about 200-220 volts and that seems to be pretty outstanding; the species cited as producing this was Torpedo nobiliana, the Atlantic torpedo.  I look askance at records of things like 700 volts, which I have seen cited as an upper range figure.

Please, manta riders, approach, harass and attempt to ride this ray.

There is a reason for the pancakeosity of the of the electric ray: if you observed the engraving by John Hunter above, electric rays’ kidney-shaped electricity-producing organs are located in the sides of their discs.  If you’d like to see these organs in the flesh, the Brine Queen dissected an electric ray and documented the process.

An electric ray will specifically use its Thor-like powers to ambush its prey, wrap its flexible body around it to deliver powerful shocks, and then devour it using its distensible jaws.  I’m not sure if the diver in this video got shocked, but the put out ray’s posture seems to suggest it at the very least entertained the notion:

I think this covers your introduction to batoids.  There’s always more to say because there are a LOT of batoids: The ReefQuest Centre for Shark Research says that 55% of total extent elasmobranch species (sharks + batoids) are batoids, with around different 555-573 species of batoids.  I’ve mentioned fewer than 10 species in this entry, to put it in perspective.

To conclude my entry, I’ll give a small bit of attention to the neglected skate.  Skates are always neglected and I’ll fully admit I neglected them here.  I blame the world for not having more information on skates and I blame skates for not being manta rays or having much of a reputation beyond, “How is it not a ray?”.

While no, they don’t get as big as river stingrays or mantas, they certainly can get big.  I applaud the angler pictured below, Damian Greenwood, for releasing his quarry.  There are definitely more sustainable fish to eat.  Read the full write-up here.

192 lb/87 kg skate caught off the west coast of Scotland.
For those of you interested in skate fishing in the region, here is a handy skate identification chart courtesy NOAA, though it does contain information on protected species that is from 2014 and is thus not the most current re: fishing governance.
As your reward for reading through all of this, why not check out a book about skates, rays and more-than-likely sharks? Here are today’s offerings:
For the diehard elasmobranch enthusiast! Successor to the classic work in shark studies, The Elasmobranch Fishes by John Franklin Daniel (first published 1922, revised 1928 and 1934), Sharks, Skates, and Rays provides a comprehensive and up-to-date overview of elasmobranch morphology. Coverage has been expanded from anatomy to include modern information on physiology and biochemistry. The new volume also provides equal treatment for skates and rays. The authors present general introductory material for the relative novice but also review the latest technical citations, making the book a valuable primary reference resource. More than 200 illustrations supplement the text.
Hundreds of thousands of people have an intentional encounter with sharks every year, and shark-watching has become a multi-million dollar business. The ultimate shark-watcher’s guide, this comprehensive and ground-breaking book is essential reading for any marine enthusiast who wants to navigate the waters of those who consort with sharks.
Sometimes you just need a general lay-level text on elasmobranchs: this book is your destination. Sharks have a reputation of being the most feared creatures of the sea, and in this fantastic book, we learn the myths and facts of these fascinating animals–and that they aren’t as deadly as they seem. Of the more than 850 shark species, 80 percent either would not hurt people, or would rarely encounter them.
Sharks and their kin–skates and rays–have remained essentially unchanged for hundreds of millions of years, and their very existence is now threatened by man and his fears. Thomas Allen takes us through the evolution of the shark, its folklore, its commercial uses, and gives us a detailed look at shark attacks–where they happen, why, and how to protect yourself from them. He describes over one hundred shark species–their behavior, appearance, size, and distribution–and provides helpful scientific illustrations. He offers current information on scientific research (including the recent studies on shark cartilage in cancer research), current population findings, and continuing conservation efforts.
With over twenty-five color photographs of familiar and unusual sharks, interesting and fact-filled sidebars, and useful appendices, THE SHARK ALMANAC is a comprehensive overview and the perfect book for anyone interested in these amazing creatures.
Shark : Stories of Life and Death from the World's Most Dangerous Waters
Shark picks up where previous Adrenaline titles such as Rough Water and Deep Blue left off, with a collection focusing on man’s terrifying interactions with one of the planet’s most frightening beasts–an animal that arouses our most primal fears–fears that were recently brought to the surface by an outbreak of fatal attacks on this country’s beaches. From novelists to sailors to oceanographers to divers, man’s encounters with sharks have produced a diverse body of gripping, ofteninspired writing by great names in adventure literature. Along with 16 black-and-white photos, selections feature a wide range of work with an emphasis on thrills and chills, including Peter Matthiessen on the great white shark, Edward Marriott on hunting man-eaters off Nicaragua, Richard Fernicola’s account of the 1916 shark attacks that inspired Peter Benchley’s Jaws, and Jacques Cousteau’s studies of the creatures. If you’re interested in checking out this title, please speak with a librarian.

*=yes, I’m oversimplifying and excluding subspecies.  DEALMadl, P & Yip, M. (2000). Essay about the electric organ discharge (eod) . Proceedings of the Cartilagenous fish Colloquial Meeting of Chondrichthyes , http://www.sbg.ac.at/ipk/avstudio/pierofun/ray/eod.htm