A different kind of White Shark

8 08 2007

Australia is known for its populations of Great White Sharks (Carcharodon carcharias), but this week news broke of a different “white shark”; a male Grey Nurse (or “Sand Tiger,” Carcharias taurus, as we call them stateside) Shark that is entirely white.

White Nurse
An image of the all-white male shark, from The Daily Telegraph.

Normally these sharks, like many others, exhibit the classic “dark on top, white on bottom” counter shading, with some darker spots over the dorsal half of their body, but this one is being heralded as “albino.” Albinism is a genetic disorder by a lack of pigment in the hair, skin, and eyes of mammals, the eyes appearing red because there is no pigment in the eye to “cover up” the blood vessels in the back of the eye (we’d all look this way if we lacked pigment in our eyes, which actually occurs every now and then). What is more likely is that this is a shark exhibiting Leucism, which is caused by a reduction in all kinds of skin pigment (albinism just deals with melanin). While I’m not sure what an albino shark’s eyes would look like, the eyes of the shark in the picture seem to be no different from those of normal sharks, which is characteristic of Leucism rather than Albinism as well. Perhaps the most famous examples of leucism are alligators; they appear to be a creamy-white color with blue eyes, almost like giant versions of a white-chocolate alligator I once received as a treat when I was younger.

Still, the presence of such a shark does raise some interesting questions. It seems to be more skiddish than other sharks of its kind nearby, so did its bright coloring make it more attractive to predators (i.e. larger sharks), requiring it to be more shy? How did it get to grow to such a size if it was so conspicuous? Why hasn’t it been seen previously? Why hasn’t another case been seen previously? We might not be able to get answers to any of these questions, but the presence of a potentially leucistic shark is definitely exciting.

Mmmmm….. blue…

6 08 2007

Why not kick off the week with another great carnival? Malaria, Bedbugs, Sea Lice, and Sunsets has the 3rd incarnation of the Carnival of the Blue, and it’s definitely worth a look.

The Discovery Channel ditches science for Shark Week

30 07 2007

One of my first encounters with the Discovery Channel’s annual “Shark Week” was in the summer of 1990, watching a documentary featuring shark scholar John McCosker with a dead baby great white shark, pointing out its bits of anatomy and why they were important. The narrator’s description of the sharks miraculous blood-circulation system, allowing it to maintain a body temperature several degrees centigrade about the surrounding seawater, is as clear in my mind today as it was shortly after viewing it. Even when turning to the subject of shark attacks, the approach was minimalist, letting famous photograph Al Giddings recall an attack on his friend Leroy French among the Farallon Islands off California; it was a beautiful, fair documentary that was reflected more of the nature of the Great White than its more famous monstrous media persona. Other shows documented shark tracking techniques, their sensitivity to different kinds of light, and there was at least some inclusion of science into many of the programs I watched year after year.

Then, a few years ago, things started to change. There weren’t as many shows about the sharks themselves as melodramatic retelling of shark attacks, lots of fake blood, spliced stock footage, and terrible synthesizer music being more common than anything else. Conservation was almost never mentioned, the larger focus being on attacks (even if there were the obligatory mentions that attacks don’t happen all that often). Indeed, the Discovery Channel hit rock bottom with the schlock-fest “Anatomy of a Shark Bite,” a self-serving piece of junk that tried to sensationalize an attack of shark biologist Eric Ritter, the metallic reconstructions of shark jaws giving rise to terrible “documentaries” like “Hippo vs. Bull Shark.” Given the downturn of the programming, I’m almost embarrassed to admit that in 2000 I assisted the “Creative Works Team” to find information about sharks for the Discovery Channel, my keys hanging from a lanyard that I was given as a “thank you” for my work for the channel.

This year, the 20th Anniversary of Shark Week, things are worse than ever. While some decent older documentaries like “Jurassic Shark” are thrown in, the new programs are mostly more of the same blood-and-guts survivor stories, one of which is called “Top Five Eaten Alive.” The synopsis of the show is as follows;

Each year dozens of people are eaten alive by sharks. These are the world’s five most amazing survivor stories.

For a short time I worked on organizing and researching cases in the Global Shark Attack File, and I can tell you that dozens of people every year are not “eaten alive” by sharks. There are a number of attacks every year (so low as to be almost insignificant risk-wise), but there have been very few cases where victims have actually be consumed by sharks. Attacks by Great White sharks, for instance, are primarily of the “bite and spit” variety, sharks being unsure whether surfers or swimmings are seals, and so they take people into their mouths and then let them go almost immediately; if they really wanted to eat us, the inch-long serrated teeth would make short work of prey with a few side-to-side thrashings of the head. Again, some people have been eaten by sharks, but I am hard pressed to think of even one substantiated case where someone was swallowed hole or “eaten alive.” This kind of sensationalist B.S. certainly doesn’t belong on a channel claiming to be educational, but then again we know the Discovery Channel is no longer educational, and columnist David Hinckley has pointed out that it’s just another version of pushing the envelope in one area (disgusting and bloody content instead of sex, drugs, or profanity), only there may be more leeway since it’s perceived to have some educational value.

Despite it being well known that sharks are in serious trouble all over the globe, the Discovery Channel continues to ignore there is a problem (see the film Sharkwater if you have any doubts). Instead, they continue to revisit the 1916 shark attacks off of New Jersey (some years saying it was a Bull Shark, others that it was a Great White), “Black December” off South Africa, the USS Indianapolis tragedy, and other tried-and-true horror stories. While the Discovery Channel endorsed the well-made horror film Open Water a few years ago (featuring one absolutely awful documentary about a woman stranded at sea, her camera capturing “Death Tape footage” even though she survived the ordeal relatively unharmed), they seem to do absolutely nothing when it comes to conservation. It’s too late to change this years programming, but concerned shark fans (people who have looked forward to watching Shark Week every year since it’s inception) are starting to speak up about the irresponsible programming. Science should not be a ratings game, and there is no reason that the Discovery (and even National Geographic) Channel should continue to ignore the real horror story; what we’re doing to our oceans.

Update: In attempting to recall at least one case of someone being “eaten alive” I remembered two files from the mid-1800’s in South Carolina. A sailor was taking a swim off the side of his ship when a supposedly 25-foot long shark came along and, as the story goes, swallowed him. Another file from that same year tells of a man in a sailor’s uniform found in the stomach of a 25-foot long shark caught off South Carolina, and I have reason to believe that this is the same shark, sailor, and case. The date of the attack was listed as “circa 1840” and the capture of the shark is listed as 1837, so although the capture would seem to precede the attack the actual date of attack is only rough at best. Unfortunately many of the original records were lost due to fire or other causes, and so we’ll probably never know for sure.

Idiocy beyond belief; SHARKS DON’T HAVE WEBBED FEET!

26 07 2007

Update: Many thanks to Chris for reminding me of one of my most favorite SNL sketches;

In March I blogged about a Malaysian woman who claimed to have found a shark with webbed feet, although anyone with even a cursory knowledge of shark anatomy could see that the “webbed feet” were really the paired male reproductive organs indicative of sharks known as claspers. [Not that I expect others to have this understanding, but rather that it’s obvious if you do have that knowledge] Now the story has resurfaced, probably due to it being featured on this blog, and plenty of folks are blathering away about how the shark does or does not support evolution. Apparently this has become the evolution equivalent of the New Zealand “plesiosaur” mix-up, at least among evolution supporters who are woefully uninformed. I was content to keep my mouth shut about this issue, just letting the issue fade away into obscurity, but then I received this comment from “bnutler”;

yeah but the first feet probably were not “feet” either. the process of evolution involves mutations, and this is an example of a mutation could have lead to feet. it would be unintelligent to assume that the first feet were actually intended to be used in the way land animals use them. It would be even more unintelligent to think that something hand designed everything on earth..

This is why the evolution debate frustrates me; even amongst people who support evolution, understanding can be absent. Tetrapods did not evolve their limbs from paired claspers; the bones of our limbs (and the limbs of our ancestors all the way down to the first tetrapods) are homologous with those of fish belonging to the Class Sarcopterygii, an extant example being the Coelacanth. The living coelacanth is not ancestral to us however, as it is too young in age and belongs to the wrong group. The group that led to tetrapods were the Rhipidistia, a subgroup of the Sarcopterygiian fish, and it was the bones in the fleshy fins of these animals that gave rise to the tetrapod limb. Indeed, even though living coelacanths are not our ancestors, they give us a clue as to how fins could have been modified to limbs; in addition to having the proper structure, they can “walk” through the water using their fins, moving them independently. Epaulette Sharks can walk along the bottom as well, using their pectoral and pelvic fins, although their skeletons are a long way from being anything close to that of the Rhipidistians.

Anyway, shark claspers are only found in male sharks, and although they are supported by cartilage they are not otherwise connected to the spine or skeleton. Thus, in order for claspers to be the antecedents to feet, they’d have to become present in all sharks of that species (including females), somehow change their musculature, change their skeletal structure, allow attachment to the rest of the skeleton, and also duplicate themselves in the front part of the skeleton and undergo the same changes (unless you’re going to argue that claspers made the back feet and pectoral fins made the front feet). This is obviously ridiculous, and furthermore what is being suggested by bnutler is a major saltation; a major change from having paired reproductive organs to having feet overnight (it would bring a new meaning to foot-fetishes, I’ll tell you that much). This isn’t even mentioning all the other physiological changes that would have to occur in the body (which we have evidence for in tetrapod evolution, especially in the spine and skull), and overall sharks are an extremely poor candidate for tetrapod ancestors, then or now.

I don’t mean to be so overly harsh, but I simply cannot believe all the back and forth over this picture. If anything, it’s a lesson that it’s not simply enough to get people to agree that evolution has occurred; if they do not understand it no good will come from it. Without understanding, people will have “faith” in evolution rather than knowledge of it, and even if a school isn’t teaching ID or creationism it doesn’t mean that they’re teaching evolution accurately (or at all!). I especially liked bnutler’s ending sentences, wherein he (she?) insinuates that because I don’t agree that the shark claspers are really freaky feet, I must believe that limbs were “intelligently designed” or created for a purpose. I guess they don’t stop by here much, huh?

[Update: Changed some of the language as it was a bit harsh; such comes from blogging out of frustrations. Also I was writing feverishly using the Mac at home, which does not highlight spelling/grammatical errors, which I have now fixed as well.]


24 07 2007

It’s that time of year again; when groups of “macho” men go out and try and prove something by catching and killing sharks off Martha’s Vineyard, a community on the southern part of Cape Cop, Massachusetts. You may have even seen some of the tournament in years past, broadcast as the “Monster Shark Tournament” on ESPN, and make no mistake, this is not a catch-and-release tournament or one that seems to have conservation in mind. Sharks are caught and brought in to be measured in front of crowds at the docks, points being awarded for the size and rarity of the bloodied animals. The big prize that made the news today? A 16 and 1/2 foot long, 536 pound thresher shark (I’m assuming it was a Common Thresher, Alopias vulpinus, from the photo, as there are three species of threshers) caught by Allen Mullaney. While thresher sharks are considered vulnerable by the IUCN and many conservationists and those concerned with animal rights have protested the shark tournament, the “sportsmen” (and I use the term despite their conduct) are not to be dissauded. Says Mullaney;

‘‘You have to love the sport of fishing to understand,’’ he said. ‘‘It was just me against him.’’

The false man-eater aspect of the tournament was played up by the coverage on ESPN when I saw it the summer before last, just as it is used to sell Shark Week on the Discovery Channel (which gets more atrocious every year). There is no care for conservation from those who fish for these sharks; it’s all about personal glory and the debunked myth of sharks as ruthless killers and sea monsters. I’ve fished for shark myself, catching a 3-foot dusky shark off Ocean City, Maryland which was measured, tagged, and released. Even this method can be quite stressful to the animal, but it is at least trying to benefit science while allowing fishermen to continue their definition of “sport.” The Oaks Bluff competition, however, offers no such consolation. Indeed, despite protests voiced about the lack of ethics involved and the behavior of some of the participants, the town went along with the tournament anyway.

I would hope that this would be the last year the tournament took place, but sharks still suffer from a PR problem despite the policy changes that have been made, and terrible TV programming doesn’t help. In 2000 I assisted the Discovery Channel with getting information for Shark Week: Uncaged (particularly the “Fin Time” segments that ran during commercial breaks), but I can hardly remember a year when the focus was on conservation and science rather than gory spectacles promising “Death Tape Footage.” Two years ago the Discovery Channel had a tie-in with the horror film Open Water, but yet they refuse to endorse the acclaimed conservation-oriented shark documentary Sharkwater. I guess they’d prefer to tell tales of death like Grizzly Man because animal violence sells. Even on its sister channel, Animal Planet, animal-on-human violence is inescapable. I forget the idiot’s name, but there a series that stemmed from a special featuring an ex-circus trainer trying to get close to lions on foot. He now has his own series which starts with a self-serving introduction about how he overcame his fear of lions after an abused animal decided not to take it anymore and took it out on the whip-wielding trainer. The show features lots of shaky-camera/fake-blood reenactments with the host commiserating with fellow attack victims afterwards, but the whole thing just makes me sick.

If that is the best “science” television can offer I’m glad I don’t get cable.

These sharks just keep getting pregnant!

27 06 2007

Because of my public school education, I have been trained to immediately think of the New Mexico Whiptail lizard (Cnemidophorus neomexicanus) whenever I hear the word “parthenogenesis.” What exactly parthenogenesis was or how it occurred was never covered, but the association between reproduction without a male and these lizards was certainly hammered in to my brain. Lately, however, there have been various cases of other animals exhibiting parthenogenic reproduction, including Komodo Dragons (Varanus komodoensis) and Bonnethead Sharks (Sphyrna tiburo).

The latest news deals with a Blacktip Reef Shark (Carcharhinus melanopterus) that had died after a physical had gone awry, the shark (named “Tidbit”) biting one of the aquarium staff before dying shortly thereafter. Upon autopsy, veterinarian Bob George discovered a near-term baby shark inside Tidbit, making this perhaps the second known case of shark parthenogenesis known. Tests still need to be done to confirm this, but Tidbit was not kept with any males of her species and sharks are not known to hybridize, so it is fairly certain that this is another case of parthenogenesis (it should also be noted that both bonnetheads and blacktip reef sharks belong to Order Charcharhiniformes, or the “Ground Sharks”).

In the case of the bonnethead shark, the parthenogenic offspring was female, and the CNN article linked above makes no mention of the sex of the offspring found in Tidbit (whatever I guessed, I’d have a 50/50 chance at being right). It is possible that in times of sexual isolation some sharks can produce offspring on their own, but if no males show up (or no males are produced through parthenogenesis, as komodo dragons apparently can achieve), then the population is no better off. I would also be interested to see if this particular ability exists across all shark groups or just in this particular order; are the “warm-bodied” lamniform sharks like Makos, Porbeagles, and Great White Sharks capable of this as well? Is this ability something new that evolved in this one group, or is it an ancestral condition that more derived sharks have lost? For now we’ll have to await Tidbit’s test results, but if nothing else aquarium curators should be keeping their eyes open for more instances of parthenogenesis going on right under their noses.

GA Aquarium suffers 2nd Whale Shark Death

13 06 2007

Just two weeks ago I wrote about the death of “Ralph”, one of the star attractions of the Georgia Aquarium, as two new whale sharks were being introduced to the crowded habitat. Now a second whale shark, “Norton”, has died. Norton seems to have suffered in a manner similar to Ralph, his health declining as he refused to eat (I wonder if they force-fed him with a PVC pipe, too). I seriously don’t know how an aquarium irresponsible enough to cram so many whale sharks in one tank could be allowed to introduce more, and I seriously hope that they will be blocked from obtaining any more animals. They aren’t helping preserve the species, despite their platitudes about starting a breeding program; the whales sharks are there to make people money, and now two of these rare animals have died so someone’s pockets could be a little heavier. Absolutely disgusting.

Sniffing out the truth on shark senses

4 06 2007

Perhaps one of the longest-standing myths about sharks is that they can “smell a drop of blood up to a mile away.” This little pseudo-fact shows up in nearly every popular work on the subject (particularly children’s books) and even in museums (like the newly re-opened Hall of Human Origins at the American Museum of Natural History). This all stems from a misunderstanding of what scents are and how they are detected; different scents and odors are actually chemicals of varying amounts present in a medium like air or water, different animals having differing sensitivities to varying concentrations of the chemicals. Sharks devote a large part of their brain to olfaction (sense of smell) and are able to detect certain odors in as little a concentration as one part per million in seawater. But in order to do this, however, they actually need to come across the chemicals in the water causing the odor, which they then follow up the “scent corridor” to the potential prey. In other words, they can’t smell anything until they actually come across the scent, so if you cut yourself in the ocean sharks don’t have some kind of 7th sense (they do have a 6th; electroreception) that tells them that someone a mile away is now bleeding. Even if some of your blood does enter the water, it is becoming more apparent that sharks are more interested in oils and certain body fluids than blood, which seems less able to travel far in seawater. Hopefully research will be done on this topic soon, but it is important to separate the truth about sharks from the modern mythology often confused with fact.

This all brings me to a newly published paper in the Journal of Experimental Biology by Jayne M. Gardiner* and Jelle Atema, in which it was determined that smooth dogfish sharks (Mustelus canis) rely on more than simply smell to find their prey. When the sharks were subjected to some squid-odor dispersed in the tank alone, they had some amount of difficulty finding the source of the scent even though you would think their sense of smell alone would be enough. When a brick was added to “jumble” the scent, however, the sharks did much better. Why? Along the body of a shark are mechanoreceptors known as the lateral line (which is present in other fish as well). These mechanoreceptors not only allow the shark to detect the movements of other fish around it, but to detect “odor plumes” (a three dimensional signature of a scent) as well, and the study seems to show that “feeling” an odor is just as important as smelling it. Likewise, when the sharks lateral lines were disabled by the researchers, they seemed to rely on vision for their lost sense, and while it took the sharks longer to find the source of the scent they had the same amount of success when in the light (they did not do well at all while in the dark).

Through much of my time in grade school, sharks were treated as “primitive” fish, a sort of “living fossil” that has gone “virtually unchanged for millions of years.” Perhaps it was my preferential bias towards these animals, but I always rejected this particular view; how could such amazing animals, with senses lacking in many of the more evolved fish, be primitive throwbacks? No one ever put them in context of evolution or pointed out that sharks have been evolving since they first appeared and have not always looked like they do now, and instead the “origin time” for each group of animals was used as a benchmark for how evolved (and therefore “important”) it was. I would love to say that such misunderstandings are no longer being taught in our schools, but I can’t be so sure. Indeed, just as we fight to keep creationism out of schools, so too should we fight for better elementary science education. It’s foolish to assume that in the absence of creationism, evolution is being taught correctly to students, and with the current focus on standardized test scores understanding science has become less and less of a priority for many schools. We are doing a great disservice to ourselves and students if we idly allow long-refuted myths to continue.

The GA aquarium continues to piss me off

1 06 2007

In mid-January of this year, “Ralph” the whale shark (Rhincodon typus) died at the Georgia Aquarium. Most initial news reports suggested that no one had any idea why the giant shark stopped swimming and soon died, the aquarium later admitting that the shark had not been eating for some time. In order to ensure that the animal gained enough nutrition, aquarium staff force-fed Ralph with a tube shoved down his throat, but this course did not help the shark.

The cause of death was reported to be peritonitis caused by a puncture in Ralph’s stomach. Aquarium staff and some researchers present suggested that the PVC pipe used to feed Ralph did not cause the fatal perforation of the stomach, although they conceded that it may have been contributory to his ill-health. Another male whale shark, “Norton,” stopped eating for a time as well, but I can only assume that he has recovered as there has been no more news, and I can’t say I’ve heard anything involving the female whale sharks Alice & Trixie. In the wake of Ralph’s death, Taiwan (which supplied the aquarium with the sharks) was reluctant to give the exhibitors any more, but apparently they gave in as two new whale sharks arrived at the aquarium today.

I really don’t see the reason for adding two more whale sharks when the aquarium already had three and one died from causes that no one at the aquarium seems to understand (either that or they’re lying). Every now and then I hear the assertion that these animals should be kept for a breeding program, but for a breeding program you need to be able to keep animals alive and well in captivity, something that is even more difficult with pelagic marine species. Plus, even if the sharks did breed we would have to assume they’d want to release the babies into the wild or that any country would let them do so, so I can’t even be sure they have “good intentions.” I do not have high hopes for the new whale sharks, and I have to wonder if they feel a bit cramped; whale sharks are large and far-ranging, and even the biggest aquarium is probably too small.

Unfortunately the Georgia Aquarium hasn’t been exactly forthcoming with information regarding Ralph’s death, nor are they likely to. If it was discovered that they contributed to the death of a threatened animal through lax husbandry practices (which I think is quite likely), they’d lose a lot of credibility and perhaps even the ability to collect rare specimens in the future, making it in the best interests to simply wave their hands around and side-step questions whenever the name “Ralph” comes up.

Huge Great White Shark caught off Rizhao, China

10 05 2007

According to this People’s Daily Online article, a Great White Shark just under 15-feet long was caught off Rizhao, China (Shandong province). While great whites grow much larger than 15 feet, this is still a huge animal, especially when great whites in excess of 16 feet are rare. The article is light on details, but there are several photos of the dead female shark (the shark has no claspers, therefore, it’s a female) with the fishermen. I don’t know about you, but dead sea creatures (and white sharks especially) always make me sad; they look grotesque when hoisted up by their tails, blood covering their heads and guts crammed up near their pectoral fins. Even so, while the death of this one shark is significant many more are killed every day, further depleting stocks under pressure and in turn causing significant ecological change. If you’re scientist and support conservation I ask you to please sign the Manifesto for Shark Conservation, and if not check out the film SHARKWATER for a closer look at what’s happening to these animals.