A Ray of Hope in a Sea of Chum

Megalodon: The Monster Shark Lives
Discovery brings SHARK WEEK viewers on a search for a massive killer Great White shark responsible for a rash of fatalities off the coast of South Africa. One controversial scientist believes that the shark responsible could be Megalodon, a 60-foot relative of the Great White that is one of the largest and most powerful predators in history. Our oceans remain 95% unexplored, and this massive prehistoric predator has always been shrouded in secrecy, but after a rash of newly discovered evidence, authorities are forced to investigate and hunt for the predator long thought to be extinct. A crew of scientists and shark experts examine evidence and fearlessly seek answers to the many questions surrounding one of the last great mysteries of the deep ocean while creating the largest chum slick in history. (http://bit.ly/SharkWeek2013-programming) 

That’s the way Shark Week feels to me these days, like a big, multi-platform chum slick…a greasy, fetid soup of fear and fascination that titillates more that it educates. Is that over the top? Yeah, probably, but then it will fit right into a line-up that includes titles like: I Escaped Jaws, Great White Serial Killer, and Sharkpocalypse. In all honesty, most of these shows will not be nearly as bad as their titles suggest. My primary beef is (and continues to be) the lack of shark diversity during Shark Week.

But hark, what’s that? A bioluminescent beacon of light from the deep? On Thursday, August 8, Discovery’s feature program is Alien Sharks of the Deep. Reading that title out loud makes it sound worse than the rest…like an early draft of the robo-monster blockbuster Pacific Rim. But no, this program appears to explore the weird, wonderful, and diverse sharks of the oceanic abyss. Could this restore my faith in the potential that is Shark Week? Think of some of the possibilities:

 Goblin sharks: Goblins have been known as tenguzame, after tengu, a fantastical creature of Japanese mythology often depicted with an elongated nose or beak. Goblins are fantastical in their own right, with long, blade-like rostrums and slingshot protrusible jaws that have to be seen to be believed.

070209-goblin-shark_big

Goblin shark

 Taillight and lantern sharks: Many deepsea sharks are bioluminescent, creating light with specialized organs called photophores. Many of these sharks use their photophores to hide in the downwelling light by erasing their shadows through counterillumination. Tailight sharks also secrete a blue luminescent fluid from their, um, ‘tail end.’ Since the species is known from only two specimens and has never been seen alive, no one knows exactly what this fluid is for.

 Megamouth: Not to be confused with Megalodon. In fact, the two couldn’t be less alike. Large Megalodon teeth may be 5-7 inches long (about the size of your hand), megamouth teeth 5-7 millimeters (half the size of your pinkie fingernail). Whereas Megalodon likely fed on whales and other large marine mammals and turtles, megamouth is a plankton specialist. There have been only 55 confirmed sightings of megamouth sharks since 1976, and only a handful of these have been examined by scientists.   

Megamouth-shark

Megamouth shark

 Frilled sharks: Frilled sharks are a freak show. They hardly look like sharks at all. Well, they do, just more like sharks from hundreds of millions of years ago. The long, eel-like body, terminal mouth, unusual teeth, fins, and other anatomical features are all distinctly ancient. 

Frilled-shark-showing-specially-adapted-teeth

Frilled shark

 Rough sharks: Rough sharks are another group that breaks the stereotypical shark mold—small and hunchbacked, with large spiny dorsal fins. They may be fairly common in the deep waters where they’re found, but still, we know very little.

Rough shark. Photo Joanna Franke

Rough shark. Photo Joanna Franke

 Six- and sevengills: Cow sharks are another group with distinctly ancient features. Many have seen sevengills in public aquariums, but the larger sixgill sharks don’t do as well on display. Sixgills are broad, ponderous creatures, with large specimens more than 16 feet long and as big around as a Volkswagen (as one diver describes them). These normally deepwater denizens have been occasionally spotted right under pier at the Seattle Aquarium. Puget Sound’s deep, glacier-etched profile provides a unique opportunity to observe and study these sharks without the need for research vessels or submersibles. 

Bluntnose six-gill shark

Bluntnose six-gill shark

 Cookiecutters: Interested in learning about a glowing foot-long shark that feeds on whales, tunas, swordfish, and squid? So are scientists, as they don’t seem to agree on how this small, slow-swimming shark seems to manage it. While they might not have the physique for the feat, they have the oral equipment. Fleshy lips and a strong tongue create a suction grip that buys time for the cookiecutter’s large, triangular lower teeth to cut a plug from its unsuspecting victim. 

Photograph by Reuters/Tokyo Sea Life Park/Handout

Cookie cutter shark. Photograph by Reuters/Tokyo Sea Life Park/Handout

 Cats and dogs: The deepsea is really the realm of dogfish and catsharks…dozens of species, some with names alone that inspire curiosity. Don’t you want to know more about lollipop catsharks, mosaic gulper sharks, birdbeak dogfish, spatulasnout catsharks, velvet bellies, demon catsharks, frog sharks, pajama sharks, pocket sharks, and pygmy ribbontail catsharks? Me too.

 I’m excited for Alien Sharks in a way I haven’t been for Shark Week programming in a very long time. Wednesday night I’ll have trouble sleeping with visions of lanternsharks dancing in my head. There is soooo much more to sharks than white sharks and tigers and bulls (oh my). How can we encourage more programming that highlights this fascinating diversity? We can watch.

 That’s my call to action. Watch Alien Sharks of the Deep on August 8, 10:00/9:00 central. Ask your friends to watch. Throw an Alien Sharks party. Dress up like an Alien Shark for work. Live tweet #AlienSharks like the second coming of Sharknado (you can follow and tweet at me @jimwharton). Show Discovery your love for Alien Sharks and beg them for more. Be as pathetic as you like. Let’s send a message that it’s a big wide world of sharks out there and we want to see more of it…and we’ll be happy to swim through an ocean of chum to get there.

Myth debunked: Delaware Bay not an annual pit stop for all shark species

A fan of Beach Chair Scientist on Facebook recently asked me to demystify a rumor she had heard. This is what she wanted to know: “I was told that over the course of a year, at least one of every species of shark can be found in the Delaware Bay. Do you know if this is true?” I asked Jim Wharton, frequent BCS guest blogger and shark expert, to tackle this one. This is his response.

Sadly, it is not true. There are at least 500 species of sharks in the ocean. They range in size from six inches to sixty feet. They can be found in water ankle deep to the abyssal depths … from the tropics to polar ice caps. To find a nexus point like this anywhere in the ocean would miraculous. Sharks are just too diverse.

Still, there are sharks in Delaware Bay. Anglers might encounter sand tigers, sandbar (brown) sharks, smooth dogfish, and spiny dogfish with other occasional visitors (including at least one record of a juvenile white shark). In fact, the National Marine Fisheries Service has identified the Bay as ‘Essential Fish Habitat’ for several species of Federally protected ‘Highly Migratory Species’ including sandbar sharks, sand tigers, and smooth dogfish. This designation recognizes the critical foraging and nursery habitat the Bay provides for these important species.

Sand tiger shark at the Georgia Aquarium. Image (c) Underwater Times

Dr Dewayne Fox’s lab at Delaware State University is working to create a conservation plan for the sand tiger sharks in the Bay. These distinctive, snaggletoothed sharks are very popular in public aquariums. Despite their fearsome appearance, they rarely interact with people. Sand tigers are top predators and represent a critical keystone species in the ecology of Delaware Bay. Dr. Fox and his students are implanting passive acoustic transmitters inside sharks to better understand their movement patterns. The transmitters emit an identifiable ‘ping’ that is collected by strategically located listening stations to help researchers track the animals in the Bay. Understanding how the sharks use the Delaware Bay is essential to identifying critical habitat for protection. You can learn more about Dr. Fox’s work here.

Sand tigers, by way, are freakish and fantastic creatures that are well-worth saving. No sharks have swim bladders, but sand tigers gulp air at the surface to make themselves neutrally buoyant. Sand tigers are one of many species that explode the myth of the shark in constant motion, frequently found lying near-motionless on the sandy bottom. Sand tigers are fish-specialists, with more-than-a-mouthful of narrow, prong-shaped teeth for grabbing slippery prey. They like to hang-out in large aggregations and may actively cooperate to herd schools of fish. Most fantastic of all…baby sand tigers are “embryonic cannibals.” Sand tiger embryos quickly exhaust their meager yolk sacs and start in on the undeveloped eggs…but they don’t stop there. The largest embryo in each uterus (yes, sharks have two) attacks and consumes its brothers and sisters in the ultimate form of sibling rivalry.

Good references for more on sand tigers:

  • Castro, J. I. (2011). The sharks of North America. Oxford: Oxford University Press.
  • Compagno, L. J. V., Dando, M., & Fowler, S. L. (2005). Sharks of the world. Princeton: Princeton University Press.

Thanks for sharing you knowledge, Jim! Check out his other BCS posts on sharks here.

10 fish you don’t see during Shark Week

I confess. I’ve given up on Shark Week. It took 25 years to shake me, but for the first time I can remember, I won’t be watching. When I was 16, you couldn’t schedule enough great white and shark attack programming to satisfy me. Danger Beach, Vic Hislop, Air Jaws … it was all good. It’s obviously a winning formula for Discovery, but for me, it’s just not enough any more.

There are 500 species of sharks out there. Probably more. There are so many stories to tell. Here are ten you (probably) won’t see this year during Shark Week:

1. Ocean giants. The two largest fishes on Earth are sharks. Thirty-foot, plankton-eating basking sharks can filter a swimming pool of seawater every hour through sieve-like gill rakers in their throats. Whale sharks grow bigger than school buses, and gather by the hundreds in the waters off Mexico’s Isla Holbox and other global hotspots for seasonal feasts of zooplankton or fish eggs. Despite surviving on this surface-dwelling diet, researchers have also tracked whale sharks to depths of more than 6,000 feet. Why?

2. Glowing deepsea sharks. Lantern sharks glow in the dark and hide in the light. Many species of deepwater sharks, including the lantern sharks, are bioluminescent (i.e., they create their own light). Some of these sharks can even project light from their bellies that closely matches the light filtering down from above, erasing their silhouette. They also happen to be beautiful little creatures with fantastic names, like the velvet belly shark, the taillight shark, and the splendid lantern shark. Wouldn’t you like to meet a splendid lantern shark?

3. Cookie cutters. Shark geeks know all about the cookie-cutter shark, but I always forget that they’re not exactly famous…yet. A big cookie-cutter is less than two feet long and yet they’ve been known to feed on tuna, seals, dolphins, and whales…yes, whales. It’s a neat trick. The cookie-cutters sneak up on large prey, attach themselves with fat, sucking lips and twist and thrash until they pull free a round plug of flesh. These little sharks have a remarkable set of jaws with positively enormous teeth. In fact, the cookie-cutters have the largest tooth-to-body-length ratio of any shark (including the great white).

4. Wobbegongs. Can I interest you in a flat shark with patterns like bad 70’s wallpaper and a mustache that would put Tom Selleck to shame? Wobbegongs are bottom-dwelling masters of camouflage with ornate, branching lobes hanging from their upper jaws that look enough like algae or kelp to attract unsuspecting fishes and crustaceans. Wobbegongs lie in wait until their prey gets just a little too close, then erupt in an explosion of tassels and teeth.

5. Hammers and saws. You may have seen hammerheads during Shark Week, but have you ever seen a winghead shark? Wingheads have ‘hammers’ nearly half their total body length. To what benefit? Don’t know. What’s stranger than a hammerhead? How about a sawshark? Imagine a shark, with a chainsaw blade attached to its face and two long noodle-like nasal barbels for detecting buried prey. You can’t make this stuff up.

6. Here be goblins. All sharks have protrusible jaws. Their choppers are loosely attached to their skull, which allows them to push their jaws forward to get a little extra reach, or to create suction. Goblin shark jaws aren’t just extendable, they’re spring-loaded. Elastic ligaments are stretched taught when the shark’s mouth is closed and slingshot the jaws forward as they open. Goblins may need the extra reach to get out from under their long, wide rostrum…which looks a little like an ironing board (at least to me).

7. Helicoprion. You’ll hear plenty about the mega-monstrous megalodon this week, but I’d rather hear a little more about a real pre-historic elasmobranch enigma. Helicoprion had a strange spiral tooth whorl that early paleontologists had no idea what to do with. Some placed it in the sharks’ mouth, some on their dorsal fin. Some suggested it shot out like a frog’s tongue to ensnare their prey. Though speculation seemed to have settled on a lower jaw placement, at least one author suggests the teeth may have resided in Helicoprion’s throat.

8. The shark that walks like a dog. One of my favorites is the epaulette shark, a charming little carpet shark with a distinctive ocellated spot on its flank and a peculiar habit of locomotion. Epaulettes scamper across the reef on large pectoral and pelvic fins. Truthfully, these sharks look more like salamanders than dogs as they wriggle over complex coral reef habitats…and maybe a little like pigs as they root around in the substrate searching for food with their nasal barbels.

9. The sharks who’re named for cats. The catsharks are the largest family of sharks, and boast some of the strangest and most beautiful sharks in the sea. Some catsharks sport snappy colors and patterns like the striped pajama catshark and the chain dogfish (which is actually a catshark). Others are just bizarre, like the spatulasnout and lollipop catsharks, two hyper-specialized deepsea rarities. The aptly named swell shark gulps seawater (or air) and inflates like a pufferfish when threatened.

10. Sleepers. There’s not only diversity in size, shape, and appearance; there is also surprising variety in the ranges and habitats of sharks. Would you expect to find sharks beneath arctic ice sheets? Greenland sharks and Pacific sleepers are lumbering, flabby, but impressive beasts, surviving and thriving where you’d least expect. Stomach contents range widely from giant squid to halibut to seal and whale blubber to at least one (probably apocryphal) account of an entire reindeer.

That’s ten, but I’m still ignoring that other elusive plankton-feeding giant, the megamouth shark, not to mention the long-tailed threshers, the surrealistic rough sharks, frilled sharks, cowsharks, spotted zebra sharks, and puffadder shysharks. I won’t be watching, so if you hear more than a gee-whiz sound bite on any of these sharks, you’ll have to leave a comment to let me know and my faith will be restored.

I will credit Shark Week for creating a lot of excitement about sharks once a year. Some of the kids thrilled by the antics of bait-addled and target-tempted whites, tigers and other super predators will go on to become scientists, conservationists and marine educators…but many others will merely have tired shark stereotypes newly instilled or freshly reinforced. The challenge falls to educators, researchers, and shark enthusiasts to pick up the gauntlet and fill in the blanks for those viewers who just don’t know what they’re missing when it comes to the unappreciated (but critically important) diversity of sharks.

This post was contributed by Jim Wharton, Director of Conservation and Education at the Seattle Aquarium.

Do all jellies sting?

Yes, they do. All jellies have specialized structures called cnidoblasts. Inside the cnidoblasts are capsules called nematocysts. Inside each nematocyst is a coiled, hollow thread. Nematocysts are triggered by mechanical (touch) or chemical stimuli. When they fire, the thread turns inside out, pierces its prey and delivers its venom. A jelly’s tentacles and oral arms are covered with thousands of these spring-loaded little death traps.

But not all nematocysts are created equal. The sting of a sea wasp can be deadly inside of five minutes. The famous “stingless” jellies of Jellyfish Lake in Palau however, have a venom so weak; you’d have to give them a good lick to have any effect at all.

But we’ve only scratched the surface here. Check back often at http://www.beachchairscientist.com for more insight about your favorite beach discoveries.

Jim Wharton
Vice President, Education Division, Director, Center for School and Public Programs, Mote Marine Laboratory

What allows jellies to float?

Jellies don’t technically float; they’re neutrally buoyant (or close to it). Floating would be bad. It would mean being stuck on the surface, like a boat. Jellies are mostly water-up to 96%. What’s left is mostly the “jelly” in a jellyfish, the mesoglea. Jellies sink exceedingly slowly, and make up for it with just a little bit of swimming. A few pulses of the bell can keep them in place, but that’s about it. Jellies can swim all day and not really “go” anywhere. These gelatinous gems are the world’s largest plankton-completely at the mercy of the ocean currents.

But we’ve only scratched the surface here. Check back often at http://www.beachchairscientist.com for more insight about your favorite beach discoveries.

Jim Wharton
Vice President, Education Division, Director, Center for School and Public Programs, Mote Marine Laboratory

What do sand sharks eat?

“Sand shark” can be a bit of a catch-all term, but it seems to most commonly refer to the sand tiger shark, Charcharius taurus. Sand tigers are an interesting case study in form following function in shark teeth. Sand tigers have long, narrow, prong-shaped teeth—like the tines of a fork. Their teeth are perfectly shaped for spearing slippery prey like fish and squid. But while slippery swimmers make up the bulk of their diet, it is worth pointing out that sharks are always opportunistic. Sand tigers are not above snapping up a wayward crab or lobster.

Jim Wharton
Vice President, Education Division, Director, Center for School and Public Programs, Mote Marine Laboratory

What is the rarest shark species?

There are plenty of candidates. The deep-diving, plankton-feeding megamouth shark was discovered as recently as 1976 and is only known from 40 or so specimens. A group of species called “river sharks” seem pretty rare. Some have been described from just a single collected specimen. There are many deep sea sharks that have only been caught a handful of times. Does that make them rare? Maybe we’re just lousy at finding them?

What is clear is that many species are much rarer than they used to be. One study finds shark populations in the Mediterranean Sea down 97%. Another found oceanic whitetips in the Gulf of Mexico down 99% since the 1950s. Large predators are naturally uncommon as it is. It takes a lot of energy in an ecosystem to support them. It’s up to us to make smart decisions when it comes to seafood and coastal development to keep them from becoming even rarer.

But we’ve only scratched the surface here. Check back often at http://www.beachchairscientist.com for more insight about your favorite beach discoveries.

Jim Wharton
Vice President, Education Division, Director, Center for School and Public Programs, Mote Marine Laboratory

Do sharks have bones?

No sharks do not have bones.

Sharks do have skeletons, but they’re made of cartilage rather than bone. Cartilage is the flexible stuff in the tip of your nose. A cartilage skeleton has its advantages. It’s light, flexible, and it heals faster than bone. In some spots though, sharks need a little extra strength. Their skulls, jaws, and spine are fortified with calcium salts, making them much thicker and stronger. Can you think of why a shark would need strong jaws, skulls, and spines?

by Jim Wharton
Vice President, Education Division, Director, Center for School and Public Programs, Mote Marine Laboratory

Do you have another great question? Email info@beachchairscientist.com.

Are stingrays related to sharks?

English: Various types shown. Taken at Mote Ma...

Image via Wikipedia

Stingrays and sharks are very closely related. They belong to a group of fishes called the elasmobranchs. All elasmobranchs have 1) skeletons made of cartilage (the flexible material that makes up the tip of our nose and ears) and 2) 5-7 gill slits. Elasmobrachs includes sharks, rays, and skates.

It’s not entirely incorrect to think of stingrays as flattened sharks. On the inside, they’re just about the same. There are some animals that blur the lines between the two. Angel sharks and wobbegongs are flat, but they’re not rays. Then there are sawfish (which are rays) and sawsharks (which are sharks). Sharkrays are just plain confused. As a general rule, if the gill slits are on the bottom, it’s a ray. If they’re on the side, it’s a shark.

Jim Wharton
Vice President, Education Division, Director, Center for School and Public Programs, Mote Marine Laboratory

Do you have another great question? Email info@beachchairscientist.com!

In what way can a beach be compared to a desert?

…It’s Charismatic Microfauna!

Well, yes there’s the sand, but there is also an unrecognized and perhaps even shocking biodiversity that lies not quite below the surface.

Would you believe me if I told you that in a single handful of wet sand you could be holding a community of organisms equaling, if not exceeding, the diversity found in an Amazonian rainforest?

All too often we suffer from a bias of scale, but biodiversity includes all organisms, including the mega-, the micro- and the meiofauna.

So just who are the meiofauna?meio

They are the smallest animals on earth—some no larger than a grain of sand.

They live in ultra-micro habitats within habitats and make an excellent example of the complexity of ecosystems and the interconnectedness of life.

The meiofauna aren’t a kind of animal, but rather a size-class of animals that live (mostly) in and among aquatic and marine sediments. (Fully 25 animal phyla have representatives in the meiofauna and they boast some of the most unique and strange biological adaptations in the Animal Kingdom.)

Without a microscope and a little curiosity, you’d probably never notice they were there…but you’d certainly notice if they weren’t…

Among the roles meiofaunal animals play in their environment is that of the decomposer. Beaches without a strong meiofaunal component have a distinctive, sulphuric odor of decay.

The meiofauna provide even more proof that there will always be new discoveries to be made in the marine environment—not just for us, but for all of science.

The newest animal groups described have been meiofaunal—three entirely new phyla described in the last 25 years. Exploring the meiofauna opens a whole new world discovery for even the most jaded, know-it-all, marine biologist!

But we’ve only scratched the surface here. Check back often at beachchairscientist.com for more about some of my favorite meiofauna.

By Jim Wharton, Director, Center for School and Public Programs with Mote Marine Laboratory

Photo (c) Rick Hochberg