by Geoff Brumfiel
Sharks have looked more or less the same for hundreds of millions of years. But a newly discovered fossil suggests that under the hood, a modern shark is very different from its ancient ancestors.
The finding, , strongly implies that sharks are not the "living fossils" many paleontologists once thought they were. "They have evolved through time to improve upon the basic model," says , a paleontologist at the American Museum of Natural History who helped identify the fossil.
This newly discovered creature dates back 325 million years. It's no . It was probably just 2 or 3 feet long and its teeth were tiny, "although there are rows of teeth in the mouth, so it would certainly give you a painful nip," Maisey says.
The fossil of this beastie is equally modest: It looks like an . But in recent years, paleontologists have begun using tools like CT scanners to look inside fossils. When Maisey scanned the fossilized head of the new shark, he got a shock. Inside, "it's not like the anatomy of a modern shark at all," he says.
The skeleton supporting this ancient shark's gills is completely different from a modern shark's. In fact, the gill skeleton looks much more like that of an average modern-day fish.
The finding turns old ideas about sharks on their head, says , an evolutionary biologist at the University of Chicago. Previously, many scientists had believed that shark gills were an ancient system that predated modern fish. But this new work suggests that modern-day fish may actually be the ones with the ancient gill structures. Shark gills are the gills that evolved.
"That bucks a trend that's been in the literature for years and years that sharks are somehow primitive living fossils," Coates says.
Why did sharks change the structure of their gills? Maisey suggests it might be to help them sprint after prey. Or to open their jaws more widely, so they could snap up bigger things, like swimmers.
Whatever the reason, sharks have been changing. at Uppsala University in Sweden says the new work is an important reminder that so-called living fossils like sharks and crocodiles aren't fossils at all. They are constantly adapting to the world around them. "We have to be very, very careful with the idea of living fossils," Ahlberg says.
This ancient little shark shows that evolution is always at work.
By DAVID McFADDEN
KINGSTON, Jamaica (AP) — Jamaica is reporting a big decline in sightings of lionfish, the voracious invasive species that has been wreaking havoc on regional reefs for years and wolfing down native juvenile fish and crustaceans.
Some four years after a national campaign got started to slash numbers of the candy-striped predator with a mane of venomous spines, Jamaica's National Environment and Planning Agency is reporting a 66 percent drop in sightings of lionfish in coastal waters with depths of 75 feet (23 meters).
Dayne Buddo, a Jamaican marine ecologist who focuses on marine invaders at the Caribbean island's University of the West Indies, attributes much of the local decrease in sightings to a growing appetite for their fillets. He said Sunday that Jamaican fishermen are now selling lionfish briskly at markets. In contrast, a few years ago island fishermen "didn't want to mess" with the exotic fish with spines that can deliver a very painful sting.
"After learning how to handle them, the fishermen have definitely been going after them harder, especially spear fishermen. I believe persons here have caught on to the whole idea of consuming them," Buddo said in a phone interview.
Lionfish, a tropical native of the Indian and Pacific oceans likely introduced through the pet trade, have been colonizing swaths of the Caribbean and Atlantic for years - from the U.S. Eastern Seaboard and the hard-hit Bahamas to the Gulf of Mexico. They have been such a worrying problem that divers in the Caribbean and Florida are encouraged to capture them whenever they can to protect reefs and native marine life already burdened by pollution, overfishing and the effects of climate change.
Across the region, governments, conservation groups and dive shops have been sponsoring fishing tournaments and other efforts to go after slow-swimming lionfish to try and stave off an already severe crisis. The U.S. National Oceanic and Atmospheric Administration launched a campaign in 2010 urging the U.S. public to "eat sustainable, eat lionfish!"
But just because shallow waters hugging coastlines have seen declines, the fast-breeding species is hardly on the way out. Fat, football-sized lionfish are daily caught in fishing pots set in deeper waters that spear fishermen and recreational divers never see.
In Jamaica, targeted efforts to remove them are ongoing even as a national lionfish project financed by the Global Environment Facility and the U.N. Environment Program project recently ran its course after four-and-a-half years.
"I don't think we'll ever get rid of it, but I think for the most part we can control it, especially in marine protected areas where people are going after it very intensively and consistently," Buddo said.
It remains to be seen exactly how much impact fishing and marketing of lionfish meat can have. For now, it's the biggest hope around. Scientists are still researching what keeps lionfish in check in their native range. In the Caribbean and the Atlantic, they have no natural predators to keep their ballooning numbers in check.
By Jason Bittel
You'll probably hear the parrotfish before you see them. The animals chomp through solid rock and coral with fused beaks. When you're snorkeling on one of Hawaii's reefs, the noise is unmistakable. Crunch, crunch, crunch. To watch the grazers at work, it would be easy to mistake parrotfish for the bad guys. Their chompers scar the reef with deep gouges and reduce what was once hard stone into nothing more than a cloud of sand, squirted unceremoniously out the fish's backsides.
Yes, that is what happens.
Parrotfish eat the algae that grows on rocks and coral. Special plates in the throat called the pharyngeal mill grind up all that material, and the fish literally poop out sand as a result — each parrotfish poops out up to 840 pounds a year. But according to Darla White, a marine scientist with Hawaii's Division of Aquatic Resources (DAR), parrotfish are actually integral to both the reefs' day-to-day health and long-term resiliency.
"It's all about real estate on the reef," says White. "Every living thing is just looking for space, and each bite the parrotfish takes opens up an opportunity for coral larvae to settle in."
Those bites are more valuable now than ever. Coral reefs thrive on clean, clear, low-nutrient water. But runoff from the islands contains fertilizers from farms and lawn care, and these excess nutrients cause both naturally occurring and invasive algae to go haywire. Before you know it, all the available real estate is shellacked with fast-growing algae, and the extremely slow-growing coral can't colonize these surfaces. Parrotfish keep these blooms in check by beak-biting straight down to the substrate.
Unfortunately for the reefs, parrotfish are freaking delicious. They are also beautiful. And that means the fish are a prized target of both subsistence-, sport-, and even some commercial-fisherman. Most herbivores don't take a hook, but spearfishing and nets work well enough. Add to this the unfortunate fact that many species of parrotfish are also really heavy sleepers, and you can see there's a problem. At night, they secrete a layer of mucous across their body that's thought to protect them from parasites and perhaps keep predators from sniffing them out. But it does nothing to prevent unscrupulous night divers from plucking the fishies from the reef like cooling pies off the proverbial windowsill.
To combat these pressures, White and her colleagues at the DAR designated part of the reef along West Maui's coast as the Kahekili Herbivore Fisheries Management Area in 2009. This made it illegal to kill or injure several species of herbivorous fish, including parrotfish, surgeonfish, and sea chubs, as well as sea urchins anywhere in the preserve. After several years of watching and waiting, they analyzed the results in 2012 and reported that parrotfish biomass had actually doubled. What's more, they found a strong positive relationship between total parrotfish biomass and the amount of coral growing on the reef.
Problem is, White says only 1 percent of Hawaii's coral reefs are under this kind of protection — which means most of the region's parrotfish are getting picked off before they can even reach full size. And this is a problem, because when it comes to parrotfish reproduction, size matters.
Hawaii's parrotfish live in harems — one guy to half a dozen or more gals — but every fish begins its life as a female. If the harem's male gets speared by a diver or otherwise decides to go out for a pack of smokes, the most dominant female can, over time, turn herself into a male.
You can tell when a female is going through this miraculous transformation because she will start to change from a dull gray to the more striking blues, greens, and purples of parrotfish males. And because the change doesn't just simply happen overnight, it's not uncommon to see a parrotfish swimming around that's half gray (female) and half green (male).
Before the color change is complete, some species of parrotfish use their half-and-half status as camouflage, deftly sneaking into harems that still have a super-male and fertilizing the females' eggs before the alpha fish knows what's up. (Note: This is known as "streaking" (through the Quad), and it's a good way to get your ass beat. Parrotfish are highly territorial.)
It should come as no surprise then that the biggest, beefiest, most flamboyantly colored parrotfish — which you now know to be exclusively male — are at the highest risk of human predation. This makes repopulating the reefs with algae-eaters all the more difficult, since males aren't simply hatched — they're built, over time and circumstance.
"It's human nature to try to fix something once it's broken," says White, regarding the state of Hawaii's reefs. "But to try to fix an entire ecosystem, especially one that's in the water? It's not easy."
But that won't stop them from trying. The DAR has partnered up with organizations like the Coral Reef Alliance and local businesses like The Snorkel Store to educate policymakers and actually get them in the water to see what's at stake. They've worked with hotels and landscapers to raise awareness about runoff. And the Coral Reef Alliance established something called the Fish-Friendly Business Alliance, which promotes businesses that don't sell fish food — because if grazers are eating pellets out of the hands of tourists, they don't have to eat as much algae.
Whether it's reducing algae and pollution or giving parrotfish populations a chance to rebound, the goal is to return Hawaii's reefs back to some semblance of balance — or lokahi, as the locals might say. Here on the mainland, I think that translates to, "You break it, you bought it."
AIMS scientists together with a team from The University of Western Australia, CSIRO and the University of San Diego have analysed coral cores from the eastern Indian Ocean to understand how the unique coral reefs of Western Australia are affected by changing ocean currents and water temperatures. The research was published today in the international journal Nature Communications. The findings give new insights into how La Niña, a climate swing in the tropical Pacific, affects the Leeuwin current and how our oceans are changing.
“Due to the lack of long-term observations of marine climate we used long coral cores, with annual growth bands similar to tree rings, to provide a record of the past. We obtained records of past sea temperatures by measuring the chemical composition of the coral skeleton from year to year. This showed how changing winds and ocean currents in the eastern Indian Ocean are driven by climate variability in the western tropical Pacific Ocean,” said Dr Jens Zinke (Assistant Professor at the UWA Oceans Institute and AIMS-UWA scientist). The long coral records allowed the scientists to look at these patterns of climate variability back to 1795 AD.
La Niña events in the tropical Pacific result in a strengthened Leeuwin Current and unusually warm water temperatures and higher sea levels off southwest Western Australia.
“A prominent example is the 2011 heat wave along WA’s reefs which led to coral bleaching and fish kills,” said Dr Ming Feng CSIRO Principal Research Scientist.
The international team found that in addition to warming sea surface temperatures, sea-level variability and Leeuwin Current strength have increased since 1980. The coral cores also reveal that the strong winds and extreme weather of 2011 off Western Australia are highly unusual in the context of the past 215 years. The authors conclude that this is clear evidence that global warming and sea-level rise is increasing the severity of these extreme events which impact the highly diverse coral reefs of Western Australia, including the Ningaloo Reef World Heritage site.
“Given ongoing global climate change, It is likely that future La Niña events will result in more extreme warming and high sea-level events with potentially significant consequences for the maintenance of Western Australia's unique marine ecosystems,” said Dr Janice Lough, AIMS Senior Principal Research Scientist.
The researchers used core samples of massive Porites colonies from the Houtman-Abrolhos Islands, the most southerly reefs in the Indian Ocean which are directly in the path of the Leeuwin Current. Using the chemical composition of the annual coral growth bands they were able to reconstruct sea surface temperature and Leeuwin Current for 215 years, from 1795 to 2010.
Reference: J. Zinke, A. Rountrey, M. Feng, S.-P. Xie, D. Dissard, K. Rankenburg, J.M. Lough, M.T. McCulloch. Corals record long-term Leeuwin current variability including Ningaloo Niño/Niña since 1795. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4607