Tuesday, April 12, 2011

BATOIDS: Curiously Strong Fish

An undulate ray (Raja undulata)
©Alain-Pierre Sittler
Données d'Observations pour la Reconnaissance et l’Identification de la faune et de la flore Subaquatiques

1) What's a batoid?  For that matter, what's an elasmobranch?

A batoid is a ray (e.g. manta ray) or a skate.  Batoids are members of superorder Batoidea, which is under subclass Elasmobranchii. Elasmobranchii in turn is one of two subclasses under class Chondrichthyes, which contains cartilaginous fish, as opposed to bony fish (for the record, most fish are bony).  The other member of this class is Holocephali, the chimaera, aka the rabbitfish, ghost shark, ratfish, etc.  While chimaera are awesome, even fewer people care about them/know they exist than batoids and they will definitely merit their own entry in the future.  


A chimaera. Told you they were cute.
http://palaeo.gly.bris.ac.uk/palaeofiles/fossilgroups/chondrichthyes/modernforms/modernforms.html

Elasmobranchii contains the sharks and the batoids, thus making an elasmobranch any member of subclass Elasmobranchii.  Yes, this will be on the test.

2) So...what exactly are skates and rays, then?

To be exceptionally crude about it, they're flat-bodied sharks.  TIME FOR VISUAL AIDS!

Smooth skate
© Andy Murch
http://www.elasmodiver.com/SmoothSkate.htm
 
 A cownose ray, my most beloved of batoids!
 Florida Fish and Wildlife Conservation Commission (FWC).
http://research.myfwc.com/gallery/image_details.asp?id=26194

As for the $1,000,000 question, "What's the difference between skates and rays?", let's break it down bulleted list style:

-Rays bear live young.  Live birth by a manta in captivity (Japan in 2007) revealed that young manta rays come out rolled up like batoid burritos, with their wings folded.  Unfortunately, this one appeared to fall victim to an abusive father after five days.


Hello little skatelet! An egg case full of skate.
http://people.whitman.edu/~yancey/

-Skates lay eggs.  These eggs (egg cases, really) are awesome and are colloquially known as mermaid's purses.  If you live near a coastline you may have been lucky enough to have found one on a beach.  Some species of shark (such as dogfish) also produce this type of egg case.  Here is a handy egg case ID chart for UK readers wondering what they've found on the beach.

-Rays have thin, whiplike tails; the tails of skates tend to be fleshier.  

-Rays tend to be much larger than skates.  You don't see stuff like manta rays or the stingrays that get hauled out of the Mekong River in the skate family.


-Skates don't have the infamous tail barbs that some species of ray use for defense.  Instead, skates rely on thorns on the surface of their bodies.  Check out the image of the "smooth" skate again.  I can personally vouch that petting cownose rays is fun but I would not like to try it with a skate.

-Additionally, there are differences in dentition:  rays do the "crushing" plate form of dentition, skates have horrid little teeth.

As is so often the case, the ReefQuest Centre for Shark Research has written up a nicer, cleaner and infinitely more professional explanation than I just provided. I will also take this opportunity just to promote their site in general, given I end up on quite regularly: elasmo-research.org, my poppets!

3) Just skates and rays?  So what's a sawfish? 

...okay, I wasn't being completely honest with you.  In addition to skates and rays, by far the most numerous members of the group, there are sawfish and guitarfish. There are further subdivisions of guitarfish into "guitarfish" and "wedgefish" but a) these terms don't seem to be used consistently and b) frankly I don't care to delve into it, given fish names are tricky business on a good day. Suffice to say that both guitarfish and wedgefish are funky batoids that look like permutations on the theme of "shark-ray".

Sawfish are probably the most well-known due to their fabulous rostrums, aka "saws":

PISCINE ALGEBRA: SAWFISH = SAW + FISH

SAWFISH FACTS TO BLOW YOUR MINDS:
  • The spikes on the rostrum are not teeth but denticles. Denticles are a type of modified tooth, which while close to teeth, are not teeth. Bear in mind that the famous skin of sharks and sawfish are also covered in dermal denticles.  If a sawfish loses a denticle, it does not grow back.  However, that doesn't make them not-pokey.
  • The rostrum houses electroreceptors which allow the sawfish to detect the movement and even heartbeats of buried prey.
  • In turn, rostrums (rostra?) are good tools for digging up said buried prey.  Think of them as nature's electroreceptive denticle-lined shovels.  In a pinch, the sawfish can use them for slashing, too!
  • Like many large elasmobranchs, sawfish are endangered.  Wait, it's cool, lives in the ocean and is endangered?  THERE'S A SHOCKER
Unfortunately, like so many creatures with interesting organs, humans have been hacking them off and selling them as elixirs, charms, markers of prestige, curios, medicine, etc. forever.  In my quest for information on sawfish, I found an image of a sawfish that had had its rostrum cut off, been released and the wound had healed, effectively leaving the sawfish to live without one of its sensory organs.  I'm pretty sure you can fill in the blanks on the implications of that.  Their large oil-filled livers, bile, fins and skin that are of commercial interest.  Wonderful.

It goes without saying that this is cruel and somewhat akin to shark finning, another practice that fills me with joy and mirth.  Clearly I needed more evidence today to strengthen my general tendency towards misanthropy.

Child with a pile o' sawfish rostrums in Key West.  Not sure where the rest of the sawfish are.
http://www.boldwater.com/article_sawfish_ebay.shtml

Guitarfish are more famous than they probably have any right to be, thanks to the program Ace of Cakes.  Specifically, the crew was asked to make a cake for the third birthday of Sweet Pea, a shark ray (aka bowmouth guitarfish aka mud skate [?!]) who resides at the Newport Aquarium in Kentucky, in the shape of Sweet Pea herself.  Here is the original:

That's a lie, this is Scooter, Sweet Pea's "roommate".  Yeah, I know what you're up to buddy.
http://www.msnbc.msn.com/id/16951419/ns/technology_and_science-science/

...and here's Sweet Pea's birthday cake!
http://www.charmcitycakes.com

For the curious, I believe the specific Ace of Cakes episode featuring Sweet Pea is called "Swimming With the Sharks".  I vaguely remember it because I was squealing like a 4-year-old because BATOIDS ON THE TV!!!!

Cakes aside, I'm uh, not sure how much I can say about shark rays given there doesn't seem to be a whole lot of information out there about them.  I have learned that like everything else in the universe they get stuck in nets and make fisherfolk mad, they're pretty much impossible to mistake for any other creature and the "bowmouthed" part of their name is derived from the silhouette of their head resembling a longbow.

As for "shark ray", well, they kind of look like someone smashed and shark and ray together and they're the result.  No idea about "mud skate" though, that's a stupid name for them and really non-descriptive given their unique appearance.

How about non-bowmouth guitarfish?


Guitarfish that lack the "bowmouth" adjective look similar to their bowmouthed relatives, but with pointier heads and a greater diversity of body shapes:


It is much harder to find good pictures of not dead/mutilated 
guitarfish online than you'd think. BE NICE TO GUITARFISH
  
Speaking of guitarfish, the Tennessee Aquarium Blog has a couple of nice entries with lovely images showing Gibson, a giant guitarfish who lived at the aquarium for a bit when floods hit Nashville (where Gibson typically resides) in May of 2010.  Entries how one goes about moving a giant guitarfish and what one feeds such creatures follow.  There's even an online story for children about a guitarfish named Gilbert, although it's a slightly less biologically accurate representation (in all fairness, the author acknowledges this).  You should probably read it, you'll thank me later.


However, the real awesomeness of guitarfish is what they look like underneath:

Atlantic guitarfish: dorsal and ventral views of head
© George Burgess

While it's tempting to call the lower image the guitarfish's "face", that's incorrect; its eyes are on the top (dorsal) side of its body while the holes located behind the eyes are the spiracles.


WHAT'S A SPIRACLE?  I'm glad you asked that question!  Aside from the simple answer ("Them holes in ray heads!"), lets have an illustration from our friend Lord Blue-Spotted Ray:


 
Bluespotted ribbontail ray (Taeniura lymma) 
near Leyte, Philippines
Photo by Nicolai Johannesen 

To be simple about it, spiracles are holes on the surfaces of some animals that are used for respiration.  They're probably most well-known in an oceanic context from the example of batoids, but they have ample representation on land as well.  For example, many caterpillars, some types of spiders, scorpions, and others.  LET'S HAVE A VISUAL AID

© Tufts School of Arts and Sciences

See those holes sportily dotting the side of our very hungry caterpillar?  Those are their spiracles, which they can open and close at will.  Spiracles do occur in other animals, but for purposes of our discussion we'll focus on their presence in elasmobranchs (if you care you can look it up).  Yes, elasmobranchs, not just batoids: sharks (though not all sharks, mind you) have spiracles too.

Grey carpet shark; the spiracle is located below the eye.
© David Harasti

But anyway, back to the point at hand, which was ray "faces".  So what're all the holes on the under (ventral) sides of their weird heads?  The mouth is pretty self-evident, it's where they stick their food.  What ISN'T self-evident is their dentition, which is one of the big differences between skates and rays.  Rays certainly have teeth (a wide variety, in fact), but they're fused together into "crushing plates".  This can be somewhat difficult to mentally visualize so here's an example of a spotted eagle ray jaw: 

http://www.flmnh.ufl.edu/fish/gallery/descript/seray/seray.html
© Cathleen Bester

This particular set of jaws is used for crushing shelled mollusks into lunch. As I said before though, there's diversity of ray teeth so here's an illustration of dentition from perhaps the most familiar and unfairly maligned of batoids, the stingray.  This example has the benefit of showing how the jaw actually fits into the fish's head, too!  EXCITEMENT FOR ALL

Dentition of yellow stingray, A. Opened mouth of female, B. Front upper teeth (above line) and rear upper teeth (below line) of female, C. Side view of upper tooth of female, D. Upper teeth of mature male, E. Side view of one tooth of same
(Fishes of the Western North Atlantic, 1948)
http://www.flmnh.ufl.edu/fish/Gallery/Descript/yellowstingray/yellowstingray.html 
As is so often the case though, we have an exception to the rule of ray teeth: the Shamu of the batoid world, the manta ray.  Yes, I know I've managed to go this entire entry without even mentioning their awesome remora-crusted forms, except when they're beating their tortillaform offspring to death in captivity in displays of paternal care.  Mantas are filter feeders, preferring zooplankton to whelks, but they actually possess vestigial peg-shaped teeth on their lower jaw.  Poky vestigial teeth that look like this:

Manta ray teeth!
Photographer: Mark McGrouther
© Australian Museum

These teeth are not used for eating, but unsurprisingly, for mating.  Mantas get frisky, which is concerning when both members of congress can weigh up to 5,000 lb/2,268 kg.  Regardless, there is your manta ray dentition.  So what about skates?  Unlike rays, skates have their nice and pointy teeth arrayed prettily on their funky jaws in non-crushing plate fashion:

http://courses.washington.edu/chordate/453photos/teeth_photos/specialized_teeth.htm

The big question is, will skates bite you with their pointy little teeth?  I searched the Internet in vain because the word "skate" is an unfortunate homograph in English. Additionally, there's apparently some phenomenon related to hockey called "skate bite" that definitely does not involve batoid skates (although there is one that involves octopus).
...I was still talking about guitarfish faces, wasn't I?  I suppose the important part isn't so much knowing what every part of a batoid "face" is (though I encourage it!), but the fact of the matter is that picking up on resemblance of the ventral side of batoids (particularly skates) to a vaguely human idea of a grimacing face is not new. 
A few hucksters back in the day (back in the day = at least as far back as the 1500s) decided to capitalize on this and gave us the Jenny Haniver: a the body of a dried skate or ray (which preserved the "face") which was then cut and shaped to give to give it a vaguely anthropoid figure.  Some were purported to be the corpses of mermaids, some of devils (the pectoral fins of batoids came in handy for infernal capes), alien creatures, etc.

Ms. Haniver in all her glory!  This thing is incredibly cute (if you're into mutilated batoids).
http://www.zymoglyphic.org/acquisitions/haniver.html

Internet rumor purports that the celebrated bishop fish, one of my personal heroes and sources of inspiration in life, may have been a Jenny Haniver, but I find this difficult to swallow, given it would be very difficult for a Jenny Haniver to a) appeal to Catholic bishops and b) make the sign of the cross before swimming off into the Baltic Sea. We're going to ignore the fact that all of these things seem awfully impractical for any type of fish to do and just enjoy the illustration below:

Gesner, Conrad. (1587). Historiae animalium.

NOTE: If you haven't checked out the digital version of Conrad Gesner's Historiae Animalium you should probably run, not walk, there now.  It was published in 1587 which pretty much guarantees that is amazing and an utter delight.  This text has the distinction of featuring the angriest porcupines and beavers I have ever seen in my life.

Let's get back to confirmed living batoids.  I should probably do obligatory sections on three subjects that I kept running across as I've done research for this post: 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 staple 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.



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 in this entry 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 (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/straight-up stupid: taxonomically speaking, stingrays must be members of the Dasyatidae family.  There are LOTS of batoids that are not "stingrays".  In a timely fashion, there are actually inaccurate reports about a batoid in the media currently so let's have an object lesson! 

Many of you may have seen news reports of a "giant stingray" leaping onto a woman in her boat.  This "giant stingray" is clearly an eagle ray to any person with eyes and who knows anything about batoids, given eagle rays are both photogenic (thus well-known) and large.  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 (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.  Seriously, it would be really odd if a stingray, a creature that hangs out 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.
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 stuff 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.  I will suggest it if you are hellbent on physically interacting with stingrays, which I guess is better than being terrified of them.  Many well-known photographs of Southern stingrays are from this site.  However, there's also photography of people making utter jacklords of themselves with the rays.

Kfulgham84, the author of this image, demonstrates 
the dangers and temptations of fraternizing with stingrays 
at Grand Cayman Island. I'm sure that cloaca examination 
was all in the interest of "science".

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).  Of course Star-Gazy Pie readers know better and would naturally behave appropriately around rays but apparently some fools who clearly didn't receive proper home-training DO NOT.  Also, these fools take pictures of their foolish behavior and post it on the Internet.

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 fools 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 Megafish Project dude) 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 huge fricking 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 and knowledge is my drug of choice.  Jeremy Wade of Animal Planet's River Monsters also did an episode on them if you prefer that sort of fare. 


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: 
  • The mouth is on the front of the head (not the bottom of the body) 
  • The prominent cephalic lobes, aka the sticky-out things on the front of their heads. Mobula rays (which basically look like small manta rays) also have these structures.  Speaking of mobulas (which I will not talk much about, beyond saying that the two members* of family Mobulidae are mantas and mobulas, to give you an idea of their relationship), Paul and Michael Albert have produced a research essay/narrative/photo gallery thing called The Flying Mobulas of the Sea of Cortez that is worth a look.
       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 sexytime, 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, not just because it's like the oceanic equivalent of ghost-riding the whip.  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.  

Behold, the Übermensch in its natural habitat! Unfortunately there was no 
name because believe you me I'd be posting it.  Mounts: They're for WoW, 
not diving, you puddle of Ebola bleed-out. 

Oh, and possibly your silly self too, but at that point you have it coming so you'll get no pity or love from this fish blog, though you'll likely receive a heaping tablespoon of derision and contempt, tied with a ribbon made of French cave-aged scorn.

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 good ol' Proto Indo-European and fish (NOTE: It's actually an aborted term paper!) 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; geez, the platypus can do it, why can't you?  However the electric rays are unique among batoids in that they can both detect and emit electric impulses.
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 while you're here it's ridiculous fish taxonomy.  Let's do this thing, you know most of it already due to my blathering:

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 (to the point of being amusing) 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 OH GOD THEY'RE FULL OF ELECTRICITY, JUST LIKE THAT LEYDEN JAR.
           
Anyway, yeah, 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 in Japan? 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 engraving by John Hunter, 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 give attention to 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 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 also applaud the angler, Damian Greenwood, for releasing it.  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.


*=yes, I'm oversimplifying and excluding subspecies.  DEAL 

Madl, 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 

5 comments:

  1. Why is everything in the ocean so pretty & awesome? Cool entry.

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  2. A fantastic entry, and well worth the wait! I think we have all learned something today. For me, batoids are one sort of critter I don't know much about, so... that would be nearly everything.

    brb reading about the bishop fish

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  3. The awesomeness of this epic post cannot be overstated. I came upon it while searching for pictures of sawfish for an illustration I had to make, and it is definitely my find of the month. I'm a children's writer and illustrator, and a fake scientist, and stuff like this inspires and encourages me. Thank you for being awesome.

    In closing: skatlet skatelet skatelet!

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  4. This comment has been removed by the author.

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  5. I guys,

    Check the shark page at
    http://skaphandrus.com
    a comprehensive catalogue of marine species to sea lovers.

    ReplyDelete