Happy Friday!

The post TGIF: Elasmo-Lite-Brites first appeared on Deep Sea News.

Another year of science closes, giving us pause to review those new species of sharks described in the scientific literature, bringing the total number of known shark species to 512. Perhaps it’s a hollow victory to have so many different species known at a time when sharks populations worldwide are either in decline or in a complete population tailspin. But as taxonomists continue to kick ass and give names, our knowledge of shark evolution, biogeography, and ecology continue to get richer. Meet the new sharks of 2015:

Ginglymostoma unami, the Pacific Nurse Shark
This isn’t really the brand-spankin’ new species you might think, but it has been known for well over a century. The Nurse Shark (Ginglymostoma cirratum) had a disjunct distribution between the Caribbean and Gulf of Mexico and the eastern central Pacific oceans, meaning their range was divided into two separate populations. Like some nooks in the Ozarks, land barriers prevented gene flow, so the populations were both physically and genetically separated by a small spit of land called Central America. This team didn’t use genetic methods to test if the populations were distinct enough to be considered different species, but relied on a meristics, the process of compiling detailed measurements of the shark’s anatomy and comparing these values between the populations.  However, a 2012 paper on populations genetics of G. cirratum showed that the Pacific population was genetically quite unique, and divergent from any of the Atlantic populations. Since these two nurse shark populations had been separated by three million years, a few things can happen, like speciation. Indeed, their analysis showed that these two species are morphologically different enough to warrant giving the Pacific population its own scientific name. This name, G. unami, is an acronym of their alma mater, the Universidad Nacional Autonoma de Mexico.

Moral-Flores, L.F.D., E. Ramirez-Antonio, A. Angulo, and G. Perez-Ponce de Leon. 2015. Ginglymostoma unami sp. nov. (Chondrichthyes: Orectolobiformes: Ginglymostomatidae): una especie nueva de tiburón gata del Pacífico oriental tropical. Revista Mexicana de Biodiversidad 86 (2015) 48-58.

Scyliorhinus ugoi, Dark Speckled Catshark
Way down among Brazilians sharks once swam there in the millions, but overfishing took surely took a hefty toll, yet there are still new shark species to be found. Case in point: a new catshark that had long been swimming along most of the Brazilian coast but had been confused as other known species. Catsharks are a widespread, diverse, and somewhat confusing group of sharks. Differences in color, morphological changes between juveniles & adults, and sexual differences between males & females create difficulties in sorting out just how many species there are. Here, the authors use detailed meristic analysis to extract out a species that had been there all along, but the morphological features that delineate the species had not yet been defined.

SOARES, K.D.A. & GADIG, O.F.B. & GOMES, U.L. 2015. Scyliorhinus ugoi, a new species of catshark from Brazil (Chondrichthyes: Carcharhiniformes: Scyliorhinidae). Zootaxa, 3937 (2): 347-361.

Atelomycterus erdmanni, Spotted-belly Catshark

This sexy beast is one of the more colorful species of catsharks, and is one of several new species discovered from a larger taxonomic mess called the coral catsharks.  Using meristics, genetics, and biogeographical analyses, it turns out that the “coral catshark” represents several species, with this species as the newest. They don’t live in coral, so much as they crawl on and among coral reefs of Indonesia, using their pectoral and pelvic fins like tiny feet and walking like a more limber and agile salamander. Named after Mark Erdmann, a fish taxonomist who collected most of the known specimens, and was rewarded with this li’l shark bearing his name.

Fahmi & White, W.T.  2015. Atelomycterus erdmanni, a new species of catshark (Scyliorhinidae: Carcharhiniformes) from Indonesia. Journal of the Ocean Science Foundation 14: 14-27.

Bythaelurus tenuicephalus, Narrow-head Catshark
2015 also brought us two more catsharks, from the same genus, and both from the depths of the southwestern Indian Ocean. Hailing from the outer continental shelf of Mozambique and Tanzania comes the Narrow-headed catshark. The vast majority of sharks in recent years have been from the more remote pockets of Earth’s oceans, and in particular, from the deep oceans that have barely been explored. This species of Bythaelurus is a “dwarf”, a species that is sexually mature at a much smaller size than most other species in its genus.  The advantage of dwarfism might allow this species to breed at a younger age, thus increasing their overall lifetime reproductive output. Or it could be that being smaller simply means eating smaller prey that larger species of catsharks might miss. This sort of niche-partitioning may explain why there are so many different species of catsharks. The species name tenuicephalus means “narrow head”, a little less imaginative than some names, but descriptive nonetheless.

KASCHNER, C.J. & WEIGMANN, S. & THIEL, R. 2015. Bythaelurus tenuicephalus n. sp., a new deep-water catshark (Carcharhiniformes, Scyliorhinidae) from the western Indian Ocean. Zootaxa, 4013 (1): 120–138.

Bythaelurus naylori, Dusky Snout Catshark
Another year, another catshark on the list.  This species however, has quite an interesting story behind its capture.  Massive trawlers, towing huge nets and pulling up tons of fish aren’t new, but what is new is the trend for these huge vessels to move from depleted fishing grounds in the shallows, and into the relatively untapped fishery resources of the deep sea. In addition to the targeted commercial species that will earn them great sums of money when they return to port, these nets also catch and kill tons of other non-marketable species.  This is what ecologists call ‘by-catch’, but there is a sunny side to such needless destruction.  Commercial vessels are often the first to explore deep-sea zones, well ahead of research cruises that are difficult to fund and even more impossible to sustain over time. If you can get onto one of these factory trawlers, the bounty of the bycatch is yours, and what a paradise this is to shark researchers. Dave Ebert & Paul Clerkin of the Pacific Shark Research Center at Moss Landing Marine Lab got the invite to board one of these vessels as it sailed south from Mauritius, but with a small catch: they had to stay for the entire three month trawling season. If you haven’t ever had the displeasure of sailing the wild waves and howling winds where the Indian Ocean meets the Southern Ocean, then you wouldn’t know that it makes The Deadliest Catch look like a Honolulu harbor cruise. Already hardened by the seas of the Gulf of Alaska, Paul made three of these cruises, collecting more than a dozen new species of skates, rays, sharks, and chimeras that will be published in future years. The species name naylori honors Gavin Naylor of the College of Charleston who, through genetic analysis, is compiling a more complete evolutionary history of extant shark species.

EBERT, D.A. & CLERKIN, P.J. 2015. A new species of deep-sea catshark (Scyliorhinidae: Bythaelurus) from the southwestern Indian Ocean. Journal of the Ocean Science Foundation 15:53-63.

And lastly….
Etmopterus benchleyi, Ninja Lanternshark
If you haven’t already seen this sassy new deepsea shark that went viral late last year, check it out here, and here, and here. That makes six new sharks for 2015, but new species will be discovered and described in 2016, so check back next year.
VÁSQUEZ, V.E. & EBERT, D.A. & LONG, D.J. 2015. Etmopterus benchleyi n. sp., a new lanternshark (Squaliformes: Etmopteridae) from the central eastern Pacific Ocean: Journal of the Ocean Science Foundation; 17: 43-55.

The post Meet the New Sharks of 2015 first appeared on Deep Sea News.

As the sun rose this morning here in Trinidad and Tobago where I’m conducting field work, I was certain about two facts.  First: Trinidadians and Tobagonians awoke to their morning ritual of doubles and a new reality with regard to their nation’s obligations on the international trade of five species of endangered shark species (Great, Scalloped, and Smooth Hammerhead sharks, Porbeagle sharks, and Oceanic White-tip sharks) as well as all manta ray species.  And secondly: I knew I could still drive this very morning (or any morning) to the public market just outside the Trinidad capital of Port of Spain and find dozens to hundreds of dead hammerhead sharks for sale.

Let’s take a look at the ocean optimism first.  As the direct result of the hard work by individuals and organizations for over a decade, the 16th Conference of the Parties (COP) for the Convention on International Trade in Endangered Species of Wild Fauna and Flora (or familiarly known as CITES) resolved in 2013 that five shark species and all manta rays were to be included in Appendix II.  As of this Sunday morning, September 14, 2014, those new rules came into effect and nations that are party to CITES must now enforce these regulations (more on what’s at stake if nations fail to take these obligations seriously in just a moment).

In the case of shark and ray conservation, the need for a body like CITES is born from the recognition of the self-perpetuating cycle of lack of information and lack of adequate management action for commercially valuable species at the local and regional levels.  This cycle has been acknowledged by many of us within the shark conservation community as the Wheel of Shame.

Although shark fishing occurs around the world, most jurisdictions lack good or reliable data on shark populations (or data is deficient for making informed decisions on sustainability).  Because of this data-poor situation, scientists cannot offer recommendations on stock assessments, catch limits, or other critical fisheries advice.  Governments tend not to prioritize or create fisheries management guidelines in the absence of scientific recommendations.  All the while, shark fishing continues unabated, species depletion continues, and the ecosystem function of having healthy shark populations in our oceans is undermined.  And around we go.

CITES works to help partially control the Wheel of Shame by subjecting international trade in specimens of selected species to certain controls. All import, export, re-export and introduction from the sea of species covered by the Convention has to be authorized through a licensing system. Each Party to the Convention must designate one or more Management Authorities in charge of administering that licensing system and one or more Scientific Authorities to advise them on the effects of trade on the status of the species.

The species covered by CITES are listed in three Appendices, according to the degree of protection they need.  Appendix I, the category with most stringent protection, includes species threatened with extinction.  Appendix II includes species not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization incompatible with their survival.  Appendix III contains species that are protected in at least one country, which has asked other CITES Parties for assistance in controlling the trade.

At each COP, the 175-nations (or Parties) submit proposals to list species on the Appendices, remove species from the Appendices, or transfer species from one Appendix to another. Species proposals are discussed and either passed or defeated by consensus or voted upon. Each Party gets one vote. It takes two-thirds of the Parties present and voting to pass a species proposal.

Decisions to propose CITES listing is based on the best available scientific evidence on species biomass, distribution, genomics, ecological connectivity, and known threats and vulnerability to commercial trade. Consideration for CITES listing is, by mandate, to include species not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization incompatible with their survival:

CITES RESOLVES that, when considering proposals to amend Appendix I or II, the Parties shall, by virtue of the precautionary approach and in case of uncertainty either as regards the status of a species or the impact of trade on the conservation of a species, act in the best interest of the conservation of the species concerned and adopt measures that are proportionate to the anticipated risks to the species.

Long-time readers may recall that I’ve not always felt so optimistic following a CITES meeting.  COP 15 in Doha saw Blue-fin tuna, polar bears, eight species of shark, and an entire family of red and pink corals get passed over.  Conservation work at this international level is extremely high stakes, tricky, and often (if not regularly) a quagmire of corruption, coercion, and collusion.  I’ve heard too many stories of flamboyant bribery, vote-buying, secret ballots, and eleventh-hour reversals.

Yet despite these challenges, CITES remains one of the most powerful tools in the international conservation arsenal.  Flouting CITES obligations is not a trivial matter for a Party.  And while it’s not as complete a list of shark species that I’d like to see receiving protection, the new CITES restrictions that came into effect today represents the most comprehensive global effort seen in CITES’ 40-year history to give sharks and manta rays a better chance of surviving in the wild.

WHAT DO NEW CITES RULES MEAN IN PRACTICAL TERMS?
The new CITES Appendix II listing for the five sharks and all manta rays has created a new reality to all CITES Parties.  Effective today, Parties wishing to continue international trade in any of these listed species must demonstrate a non-detriment finding in order to be provided permits for international trade.  While the official verbiage gets a bit technical, a non-detriment finding represents a comprehensive stock assessment of the target species that considers an analysis of population status, distribution, populations trajectories, current harvest rates, ecosystem roles and implications, and existing trade data.  In total, a non-detriment finding demonstrates that (in the case of sharks and rays) fishing for and international trade in these species will not cause the collapse or critical depletion of the species nor loss of any ecosystem functions those species provide.  Short of providing a non-detriment finding, Parties may not continue international trade.

Since participation in CITES is voluntary and each Party assumes financial and technical responsibility for their own implementation and compliance, you might think that CITES has little teeth when it comes to infractions or failure to uphold obligations.  In truth, the CITES Secretariat does not monitor international trade but  needs to be informed of an infraction by a Party before action is considered.  And if international trade in the now CITES Appendix II-listed sharks and rays is small, you might think that a Party has little to no risk in letting shark fins or manta gill-rakers slip through their borders.  But consider for a moment the full suite of CITES species a Party may traffic in their international trade, not just sharks and rays.

Infractions from lack of enforcement of any single CITES species regulation can impact all of a Parties trade in CITES species.  The language of the Convention stipulates that infractions can result in, “the recommendations to all Parties to suspend CITES related trade with the offending party.”  This means that a Party not only risks its trade in shark fin through lack of compliance in CITES Appendix II restrictions, but also its lucrative trade in exotic hardwoods like mahogany, rosewood, or ebony.  Then there’s trade in fish, invertebrate, and coral species for the multi-million dollar home aquarium industry.  Or trade in birds, reptiles, or mammals for the pet market.  And Parties also benefit financially by supplying biological specimens for pharmaceutical research.  With CITES regulatory infractions, if you’re in for a penny you’re in for a pound.

But while the new CITES Appendix II listings for sharks and rays are reason for celebration within the conservation community, our work is far from over.  Scroll back up to the top of this post and take another look at the photo.  That dead Scalloped hammerhead shark was photographed in a fish market here in Trinidad yesterday.  It was a juvenile, and it was one of many.  Today’s new CITES rules change NOTHING with regard to domestic fishing, consumption, and trade.  In a place like Trinidad, that local consumption and trade volume is not trivial.  Those endangered hammerheads will be there today, tomorrow, and as long as local and regional management recommendations are lacking.

That’s where working with local fishing communities, regional fisheries management organizations, local governments, and local communities comes into play.  Until local people recognize the importance of healthy sharks to healthy oceans, the unique life histories of sharks that make them particularly vulnerable to overfishing, and that in many cases a shark is worth far more alive than dead to local economies, this scene will continue to play out.  To date, ten nations have stepped forward to demonstrate shark conservation leadership at the local level through the creation of shark sanctuaries.  Coupled with regional fisheries reform measures, and now strengthened by the enhanced protection derived by the new CITES sharks and rays Appendix II rules, we are seeing real reason for cautious ocean optimism.

The post New Obligations and Continuing Challenges in Shark Conservation first appeared on Deep Sea News.

Needless to say, if I was a shark, I’d be pissed. Why? Because sharks today suffer from real shark problems.

(I hereby declare #realsharkproblems a thing. David Shiffman, please make it a thing.)

With millions of our finned friends killed every year for their various bits, many shark species face Megalodon’s fate should we continue on our current path. If they want blood and gore, maybe Discovery Channel should create a show or two about that.

Beyond overfishing and the finning industry however, sharks today, and in the not so distant future, face yet another surmounting threat.

Ocean acidification.

As you may or may not have learned on Shark Week, sharks and other elasmobranchs have a wicked sense of smell. They use their superior sniffers to find prey, mates, detect predators, and navigate in a seemingly endless ocean. All very important sharky behaviors.

However a new study, out in Global Change Biology this month, demonstrates that increasingly acidified waters interfere with sharks ability to respond to these critical chemical stimuli. Can I get a #realsharkproblems up in here? Researchers discovered that exposing the smooth dogfish shark, Mustelus canis, to current, mid-range, and high-level CO₂ conditions not only inhibited their ability to find prey, but also influenced their predatory behavior.

Not only is this a bad thing for sharks, but also for the greater ecosystem. Contrary to popular belief, sharks do not prefer to eat people. They do however like to eat fish, and often consume the sick and diseased fish, adding to overall ocean health. If they are unable to sense these fish, this could lead to any number of problems. Unfortunately, it is unknown as to whether or not shark species will be able to adapt fast enough to deal with the changes in ocean acidification predicted for 2100.

As if they didn’t have enough to deal with already…

Reference

Dixon, D.L., Jennings, A.R., Atema, J., Munday, P.L. (2014) Odor tracking in sharks is reduced under future ocean acidification conditions. Global Change Biology, 1-9. (Flume pictured)

The post Future Shark: Living in an Ocean on the Brink first appeared on Deep Sea News.

The post Shark Weak first appeared on Deep Sea News.

“Any form of art is a form of power; it has impact, it can affect change – it can not only move us, it makes us move.”                                         -Ossie Davis

What better way to bring awareness to the threats facing our oceans than to plaster them on the sides of buildings. Bold, beautiful, and too big to be ignored.

This is exactly what Tre Packard and the rest of the brilliant company of street artists at PangeaSeed are doing with their Sea Walls project.

Harnessing the power of their craft, the PangeaSeed artisans are fulfilling their ongoing mission to use art as a medium to bring public awareness and education surrounding the conservation and preservation of sharks and other marine species in peril.

Since 2009, PangeaSeed has shed light on numerous ocean issues through their artivism  campaigns. Most recently, their Sea Walls campaign has brought them all over the world as they draw epic murals depicting everything from invasive species to overfishing.

This next week, PangeaSeed will be assembling street artists from around the globe as they descend on the small Mexican island of Isla Mujeres. Inspired by the massive homage of whale sharks and manta rays that annually come to the island to feed, artists will cover the island in Sea Walls with the hopes that they can shed light on the issues and help change the tide for these majestic creatures.

Check out more of the amazing artwork that has stemmed from this project:

Aaron Glasson – Galle Fort, Sri Lanka addressing ocean pollution.

Aaron Glasson – San Diego, California addressing shark conservation.

Aaron Glasson and Celeste Byers – Colombo, Sri Lanka addressing manta ray overfishing.

Celeste Byers and Aaron Glasson – Ho Chi Minh City, Vietnam addressing the impact of fish farming. 

Aaron Glasson and Celeste Byers – Colombo, Sri Lanka addressing human impact on our seas.

CYH JAYSON – Taipei, Taiwan addressing “seafood” over-consumption and conservation.

Toof – Honolulu, Hawaii addressing shark conservation.

Aaron Glasson, PangeaSeed and JMA Middle School students, Burbank California addressing shark conservation.

For more about PangeaSeed and their Sea Walls project, please visit them at: www.pangeaseed.org

Top image: Aaron Glasson & Celeste Byers – Tulum, Mexico addressing invasive species.

The post Sea Walls: Lessons from a Paint Can first appeared on Deep Sea News.

*Turns down the music*

Sorry about that. Just get’s stuck in my head and then there is no stopping it. Anyways, yes, we converged on Miami for the first ever ScienceOnline Oceans conference. New friends! Old friends! Mini-DSN reunion! I do believe a great time was had by all!

The entire conference was off the hook and I send mad love to Karyn Traphagen and David Shiffman for being the masterminds behind the whole thing.

Perhaps the most epic part of this world wind weekend however involved something I have been wanting to do for quite some time now. Shark tagging with the crew from University of Miami’s RJ Dunlap Marine Conservation Program.

If you have ever been out on one of their tagging trips then you know what I am talking about. If not, then you need to go sign up for one right now: http://rjd.miami.edu/participate

As a fellow marine scientist this was cool, I can’t even imagine how amazing it is for the thousands of students and other groups they bring out every year. Some of whom have never even seen the ocean!! Essentially they took us through the whole process of what they do for their research and it was truly impressive. The morning began with a run down from the great @WhySharksMatter himself, David Shiffman, discussing the research that is currently being done in their lab and what feats they have been able to accomplish not just in Florida, but all over. All of this going on while the RJD interns, or their “undergrad army” as I like to call them, are prepping the boat for the sharkapolooza that is about to go down. It was like watching a well-oiled machine.

Once we had reached our destination, RJD PhD student Austin Gallagher used the #ShiffmanShark to explain the measurements we were going to take and why. With three measurements alone, we were collecting REAL, usable data for about 7 different projects!!!  AMAZING!!! Then with a kiss of the tuna the lines were in and we were fishing.

After pulling the first 10 lines, we had yet to catch any sharks. So what do you do when you aren’t catching sharks? A shark dance of course. And to show you the fine art of the shark dance, I give you some of my new and old SciO friends: Sarah, Violet, and Kathryn.

Teach me how to Sharky. Teach, Teach me how to Sharky. (Apologizes in advance for video shakiness….we were on a boat. Shaky happens.)

I think that deserves a round of internet applause.

Needless to say our shark dance worked for the group after us, but as David reassured us, even no data is good data.

For those interested in shark dancing tagging with the UM’s RJ Dunlap Marine Conservation Program, I highly recommend it. They are doing some pretty amazing things over there and it is exciting to be apart of. Or if playing with a 6ft bull shark isn’t really your thing, consider virtually adopting one with RJD’s Adopt-A-Shark program. Then you can tell all your friends you have a pet shark and you will henceforth be the coolest person in school.

Special thanks to the cool kids at RJ Dunlap for hosting this most exciting adventure! Keep up the good work and best of luck with your ongoing research!

The post Want to catch a shark. Got to do a shark dance. first appeared on Deep Sea News.

I can clearly remember the day that I saw Finding Nemo. I was eleven years old, and when Bruce the shark appeared on the screen, it scared the crap out of me. I spent the next five minutes of the movie with my eyes half-shut, waiting for Marlin and Dory to escape.

Obviously, a career in shark biology was not on my radar screen…

…yet.

Since YouTube didn’t exist yet in 2003, and I wasn’t seeking out videos of sharks to watch for fun on VHS, this was basically the only video of sharks I had ever seen. My first observations and information about sharks was formulated from Bruce.

And now I’m on my way to being a shark biologist.  Thanks to Bruce?

I’m sure that I’m far from the only person who this has happened to. (Well, at least, that’s what I tell myself as a shark biologist formerly terrified of my own field.)

Let’s get the nostalgia flowing!

WHAT 11-YEAR-OLD ME LEARNED:

Sharks have a lot of big teeth! They must use them to eat fish. I know they can regrow from my 5^th grade science class!

1/1 Pixar! They did a good job animating the different rows of teeth, and coloration of gums and general body. It’s basically spot on. Great White Sharks have specially designed teeth, with serrations on the edges to tear prey. These teeth are continuously replaced throughout their life, and some sharks go through up to 30,000! That’s a lot of fish ripped to shreds!

Sharks can sit around and rest while talking to others. Gills, lungs, similar thing in different mediums!

Swing and a miss, Pixar! This is actually untrue for the types of sharks we see in this film. There are two types of sharks – obligate ram ventilators, which have to swim in order to breathe, and buccal ventilators, which can rest and breathe by pumping water across their gills. In reality, all three of the sharks in Finding Nemo would have been suffocating if they stood still for the entire meeting.

Let’s churn the nostalgia pot a little more. Here’s the rest of the scene:

Great white reproduction is something we actually don’t know much about yet. Though probably unlikely that they would be incredible dads by human standards, this is a topic that is difficult to study. However, some of their characteristics are relatively similar to humans- for example, 15 years till sexual maturity, and 11-month gestation period.  Though, unlike humans, they are ovoviviparous  meaning an egg develops inside the female, hatches, then continues to mature until they are born live.

Sharks + blood = instant death.  Never going into the water again if I have a cut!

This is true but only to a certain extent. If you had a little cut and waded in waist deep, you’re in no real danger. We don’t all live on Amity Island like in Jaws. But the idea that sharks can use chemorecption to follow a trail of blood or other scents is completely realistic. In fact, they can track even low levels of certain chemicals to a source a quarter of a mile away or more! They have incredibly well-tuned senses, which make them the legendary animal they are. But in regards to humans, they are generally completely uninterested. We are actually not at all their ideal prey. So you can still love Bruce, Anchor, and Chum – they aren’t going to come after you.

So, in conclusion, fish are friends. Not food.

References:

Carlson JK, Goldman KJ, Lowe CG. “Metabolism, Energetic Demand, and Endothermy” pgs 203-224 in Biology of Sharks and Their Relatives. Carrier JC, Musick JA, Hiethaus MR, editors. CRC Press: Boca Raton, FL.

“Great White Sharks, Carcharodon carcharias ~ MarineBio.org.” MarineBio Conservation Society. Web. Sunday, September 22, 2013. <http://marinebio.org/species.asp?id=38>. Last update: 1/14/2013 2:22:00 PM ~ Contributor(s): MarineBio

Hodgson ES and Matthewson RF. (1971). “Chemosensory Orientation in Sharks.” Annals of the New York Academy of Sciences. Vol 188: 175-181.

Klimley AP and Ainsley DG. (1996) “Great White Sharks, The Biology of Carcharodon carcharias.” www.academicpress.com

The post “Fish are friends. Not food.” What Finding Nemo Taught Me About Sharks first appeared on Deep Sea News.

There is a diverse and abundant gut microbiome associated with finfish, sharks, and blue crabs. These gut microbiomes all have a core Proteobacteria community, which is in contrast to the human and terrestrial mammalian gut microbiome which is dominated by Firmicutes and Bacteroidetes ribotypes. This difference may partly be attributed to the fact that some of these Proteobacteria (such as Vibrio spp. and Photobacterium spp.) are typically associated with aquatic environments.  [Givens, 2012[

As Al mentioned, Sharks have crazy gut anatomy. Their intestinal tract is short, and so in order to increase surface area in the gut and maximize the adsorption of nutrients, they have this badass spiral valve:

So it’s not surprising that the microbial species inhabiting the shark gut would be so different from humans and other mammals. And what species of microbes, you ask?

The core gut microflora of the shark species we tested (sharpnose, spinner, and sandbar) contained Cetobacterium sp., Photobacterium sp. and Vibrio sp., with Photobacterium ribotypes dominating the core group of all three shark species…Our data indicate that Actinobacteria, Firmicutes (Clostridium sp), Fusobacteria (Cetobacterium sp.), and other Proteobacteria (Campylobacter sp. and Vibrio sp.) are also important members of the shark gut microbiome. Our findings also indicate that shark gut microbiomes have less richness and diversity than most finfish guts we sampled.

…we did not find a core microbial assemblage that encompassed all of the fish species we sampled. This is consistent with an analysis of fecal microflora reported by Ley et al. (2008), which found that no OTUs [DNA sequences of microbe species] were shared by all mammalian species sampled (humans and 59 terrestrial mammals). Our results suggest that the gut microflora of each species assembles in response to the fish’s specific physiological demands and dietary needs. [Givens, 2012]

Ok, so shorter gut also seems to lead to fewer gut microbes – but the exact community might be pretty variable based on the shark species, what they eat, and where they live.

And the presence of Photobacterium microbes in the shark gut is pretty cool – but also pretty confusing when you think about it. Microbes in this group are either A) are the symbionts responsible for bioluminescence in light organs of marine species, or B) pathogens responsible for septicemia, blood poisioning, in both fish and humans. I’d love to know the metabolic role of Photobacterium in the shark gut, since it is clearly a key player in the shark microbiome.

Why is the shark microbiome less diverse? Why is it so different from other bony fish? What is the functional role of these major microbe groups reported from the shark gut? The science on the shark microbiome very preliminary right now, but shark-associated microbes are most definitely worth your consideration during Shark Week!

Reference:

Givens, Carrie E (2012) A FISH TALE: COMPARISON OF THE GUT MICROBIOME OF 15 FISH SPECIES AND THE INFLUENCE OF DIET AND TEMPERATURE ON ITS COMPOSITION. PhD Thesis, University of Georgia

The post Sharks are overrated, lets talk about their microbiome first appeared on Deep Sea News.

Given that things are not likely to change anytime soon, I propose we all do our bit to make Shark Week a bit more like it used to be, like we want it to be.  It may have started as a Discovery marketing initiative, but like all good cultural phenomena it has long since grown beyond its origins and I think it’s fair to say Shark Week now lives in the minds and hearts of a curious and passionate public with a burning desire to know about and connect with one of the planets most incredible groups of animals.  To that end, here’s 5 cool things about sharks I doubt you’ll see on TV this week.

1. They can ungrow

Wait, what?  Ungrow?  Like, shrink?  Yes, exactly, a shark can be shorter next year than it is this year; this has been documented for several different species in wild and captive settings.  How is this possible and under what possible conditions could it be helpful?  Well, the answers to those two questions aren’t known for sure but we can wax hypothetical about how and why.  The key to the how lies in the cartilage skeleton that is common to all sharks and rays.  Much moreso than bone, cartilage is a dynamic tissue.  Cells called chondroblasts and chondroclasts are scattered throughout the cartilage and they make and destroy it in a process of continuous regeneration and remodeling.  This is much harder to do in bone, which does have analogous cells (osteoblasts and osteoclasts) but they have to deal with a rigid crystalline calcium phosphate matrix, which is harder to remodel than soft squidgy cartilage.  Combined with some atrophy of muscle and organ cells, you can see how it might be possible for sharks to become smaller if conditions demanded it, such as food shortage or environmental changes.  Very handy indeed.

2. The teeth of a great white are probably the most boring shark teeth there are

Before you do a Lumberg on me, check out these bad motor scooters:

Among the 400 or so species of sharks that currently swim the ocean, there exists a bewildering array of such tooth structures.  In fact, it’s probably been one of their keys to success, because it has allowed them to feed on a huge diversity of prey items, everything from microscopic plankton to the toughest bottom dwelling  invertebrates, all the way to the fatty and juicy mammals that take up a disproportionate amount of  the Shark Week air time.

3. Their teeth are the least interesting part of their gastrointestinal system anyway. 

There are three species of filter feeding sharks, the whale shark, basking shark and megamouth.  The first two of these are also the biggest and second biggest of all sharks, by a LOT.  Whale sharks get as big as Cacharocles megalodon ever did. Chew on that for a bit (well, gum it really; they have tiny, ineffectual teeth).  The fact that, among a class of predatory fishes, filter feeding habits arose not once but THREE times during evolution, with different mechanisms each time, blows my mind regularly.

The filter pads of whale sharks deserve special attention in this regard because they are really something else.  Derived from the leading edges of the gill rakers inside the mouth, they have become so highly branched and interwoven that the gills cannot be separated to allow bulk water to flow out through them (this is not the case for basking sharks, megamouths, or manta rays for that matter).  The average pore size in the whale shark filter pad is 1.9mm, and yet they can filter out food items that are much smaller through a near-magical process called cross flow filtration.  It’s one of the true marvels of evolution.

The gut of many sharks is a completely unique design called a spiral valve intestine.  It’s basically a spiral waterslide for your lunch.  Winding but regular, long yet compact, it’s a terrific design that natural selection has hit upon, and not found in any other group except in some holocephalan fishes, which are closely related to sharks.  If you ever did find yourself in a stomach of a shark, at least you know your last act on this earth would be a wicked fun trip down a spiral slide to bum town.  Wheeeee!

4. Males? Who needs ’em?

Bonnet head sharks, a smaller cousin of the hammerheads have been proven to reproduce at times by parthenogenesis, that is, without sex between males and females.   In these cases, all of which have taken place in public aquariums, all female groups added to the collection as pups have grown up and spontaneously produced pups of their own, without ever having been kept with a male.  Through a clever process of restoring the full complement of chromosomes after producing eggs (which normally have half), females are able to produce offspring under certain conditions without the need for a male to donate the half of genetic material usually supplied by sperm.  Why they do this is not clear, but it may be an adaptation for tough times when males are scarce or populations are small, the former being likely with the latter too.

5. Zebra sharks aren’t, really.

Zebras that is.  Not when they’re adults anyway.  Fully grown Stegostoma fasciatum are a creamy colour with brown spots.  In that regard, their scientific name (Stegostoma = covered mouth, fasciatum = striped) isn’t particularly accurate.

But when you see the babies, it makes a whole lot more sense:

What an utterly gorgeous animal!  Completely harmless, like 99% of shark species (really), aesthetically pleasing and with a curious and fascinating secret of changing from stripes to spots as they grow.  The class of fishes we call “sharks” are full of such amazing gems, if only the makers of pseudo-nature TV would stop obsessing over the 4 species that, on vanishingly rare occasions, have hurt people, maybe we could teach people about the rest of these spectacular natural treasures before they all disappear because we were too busy watching the wrong ones.

The post Five things about sharks you probably won’t see on TV this week first appeared on Deep Sea News.