November 6, 2013
New species of insects, worms and other creepy-crawlers are announced on a monthly basis. Similarly, just last week, two new humpback dolphin species splashed into the headlines. And in October, news broke that early humans may have included fewer species than previously thought. This forces the question: what does it take to be a distinct species?
More than 70 official species definitions exist, of which 48 are widely accepted and used by scientists. And there’s no hard rule that scientists must stick to just one definition; some apply a handful of species definitions when approaching the topic. “I personally go to my lab every day and use five species definitions to conduct research,” says Sergios-Orestis Kolokotronis, a molecular ecologist at Fordham University, and co-author of the new dolphin study, published in Molecular Ecology. “And I sleep just fine amidst this uncertainty.”
Species definitions oftentimes do not translate from one organism to another. Dolphins may become isolated by distance and behavior that prevents them from reproducing, but in other cases–such as bacteria, which reproduce asexually–these distinguishing markers do not apply. Thus, the definition of what constitutes a species varies depending on whether scientists are studying dolphins, monkeys, insects, jellyfish, plants, fungi, bacteria, viruses or other organisms, Kolokotronis explains. And likewise, methods for investigating those species also vary. “Whoever figures out THE unifying species definition across the Domains of Life gets the Crafoord Prize!” Kolokotronis jokes.
In the case of the four dolphin species, each occupy different sections of ocean around the world, including in the Atlantic off West Africa (Sousa teuszii), in the central to western Indo-Pacific (Sousa plumbea), in the eastern Indian and western Pacific (Sousa chinensis) and in northern Australia (researchers are in the process of working on a name for that one–Sousa bazinga, anyone?).
While the humpback dolphins look quite similar, their genetics tells a different story. Researchers collected 235 tissue samples and 180 skulls throughout the animals’ distribution, representing the biggest dataset assembled to date for the animals. The team analyzed mitochondrial and nuclear DNA from the tissue, which revealed significant variations between those four populations. They also compared the skulls for morphological differences.
Although the line between species, sub-species and populations is a blurry one, in this case, the researchers are confident that the four dolphins are divergent enough to warrant the “species” title. The mitochondrial DNA turned up genetic signatures distinct enough to signal a separate species, and likewise, differences in the dolphins skulls supported this divergence. Although the nuclear DNA provided a slightly more confounding picture, it still clearly showed differences between the four species.
“We can confidently say that such strong divergence means these populations are demographically and evolutionarily isolated,” says Martin Mendez, a molecular ecologist at the American Museum of Natural History and lead author of the dolphin paper. “The key is that all the evidence–mitochondrial DNA, nuclear DNA and morphology–exhibited concordant patterns of distinct units,” he continues, which are “usually a must for species proposals.”
The genetic data the team collected does not have enough resolution to reveal how long ago the humpback dolphins diverged, and the team has yet to examine the drivers that fueled those speciation events. But Mendez and his colleagues have found that, in some dolphin populations, environmental factors such as currents and temperature play a role in separating populations and encouraging speciation. Different behaviors can help reinforce that separation, too. Most likely, however, geographic isolation plays a significant role in this case. “For populations living a couple hundred kilometers from one another, it’s perfectly possible for them to meet,” Mendez says. “But the distance from Africa to Australia is so great, it’s difficult to imagine those populations would ever be linked.”
Dolphins, Mendez and his colleagues are finding, evolve relatively quickly once isolated from parent populations. New cryptic–or hidden–species have similarly turned up in waters near South America. There may very well be other species of dolphins–or any type of animal, in fact–lurking undetected within an already-discovered species. ”This really applies to most taxa,” Mendez says. Across the board, “we’re adding many more species by looking at genetic data.”
While cryptic species almost certainly await discovery and will increase the head-counts of some organisms, in the case of ancient human ancestors, on the other hand, researchers now suspect that we’ve been too quick to pull the species card. An extremely well-preserved, approximately 1.8 million year-old Homo erectus skull discovered in Georgia alerted scientists to the potential revision. The skull’s odd proportions–large, but with a small brain case–prompted researchers to analyze variation between modern human and chimpanzee skulls, and compare those variations with other known human ancestor species. As the Guardian reports:
They concluded that the variation among them was no greater than that seen at Dmanisi. Rather than being separate species, the human ancestors found in Africa from the same period may simply be normal variants of H erectus.
If the scientists are right, it would trim the base of the human evolutionary tree and spell the end for names such as H rudolfensis, H gautengensis, H ergaster and possibly H habilis.
Ancient humans, of course, are no longer around for us to study their behaviors and mating tendencies, so anatomy has to do. For now, researchers are calling for more specimens to determine where that line will fall.
The line distinguishing two species may be a fuzzy one, but in the case of the dolphins, it is a big deal in terms of conservation. Australia, for example, is planning to design protective legislation for its new dolphin species, and Mendez hopes other countries will do the same.
Nonetheless, pondering the speciation of humans in dolphins in light of these two findings raises lots of questions: Are we fractally subdividing genetic information and brain cavity size to group and regroup organisms, or is there vast genetic diversity in even familiar species that we’ve yet to uncover? What does it mean for a species to gain or lose members of its family tree? The world and its organisms await more research.
September 17, 2013
“Call me Migaloo,” would start the memoir of the most famous white humpback whale out there. He’s not quite from the pages of Moby Dick—Herman Melville’s white whale was a sperm whale and not entirely white—but Migaloo still makes quite a splash when he lifts his head or tail above the waves.
First spotted in 1991, he’s been seen more than 50 times since, including a few times around the Great Barrier Reef this summer. But the probable-but-unconfirmed spotting by Jenny Dean, a Queensland, Australia native, takes the cake. A few weeks ago, she captured Migaloo breaching in a spectacular photo, showcasing the whale’s bright whiteness that nearly looks photoshopped.
But what’s the deal with Migaloo and white whales? Let us ocean enthusiasts from the Smithsonian Ocean Portal answer your questions.
What do we know about Migaloo?
In the past 22 years since whale watchers first spotted the exceedingly social Migaloo—so-called after the Aboriginal word for “white fella”—scientists have been able to learn a bit about him. They think he was around 3-5 years old when first spotted, which makes him 25-27 now. Barring an unfortunate accident, he may have another 50 years ahead of him, although scientists don’t know for sure how long humpback whales live because they don’t have teeth—like tree rings, analyzing concentric layers in teeth is a common way to measure age in mammals.
They know he’s a male from his song. While both male and female humpback whales produce sound, only males sing the melodic humpback songs that long ago captured our imaginations. In 1998, researchers first recorded Migaloo singing—and his knack for melody gave it away.
His maleness was further confirmed by DNA after researchers from Lismore, Australia’s Southern Cross University, collected skin samples from Migaloo in 2004.
Are white humpbacks rare?
As far as we know, exceedingly so. Besides Migaloo, there are three other known white humpbacks. Willow lives up in the Arctic and was spotted along the coast of Norway in 2012. Meanwhile, Bahloo lurks in Migaloo’s territory in the Great Barrier reef, first seen in 2008. But these two are not as gregarious as Migaloo, rarely showing their faces.
The other known white humpback is a calf first seen swimming around the Great Barrier Reef in 2011. Unofficially named “Migaloo, Jr.,” the calf is not known to be the child of Migaloo—in fact, the two whales may not even be related. If a DNA sample from the calf is obtained someday, they could compare it with Migaloo’s genetic profile to find out.
There probably are more white whales out there, however. These are just the ones that have surfaced near people with cameras. Two years ago, an unknown white whale washed up on a beach, and if you dig around on the web, you can find even more.
How do we know these aren’t the same white whale?
In the case of Migaloo, Jr., it’s pretty obvious: he’s much smaller than the Migaloo Australians are so familiar with.
Bahloo and Migaloo hang out in the same area and, because Bahloo rarely shows its face, you could argue that the two are actually the same whale. But photos taken in 2010 showed a few black spots on Bahloo’s head and tail, differentiating it from Migaloo. Willow also has black patterns on the underside of its tail, making Migaloo the only documented all-white whale. These patterns and markings are distinct for each whale, white or otherwise, allowing researchers to track the creatures through detailed observations.
Why is he white anyway?
Many articles describe Migaloo and the other white whales as albino. But making that diagnosis is easier said than done.
Albinism is a genetic disorder in which the protein tyrosinase, which helps to produce the pigment melanin, is completely absent or damaged by a variety of possible mutations. Fully albino animals and people have no melanin whatsoever; they are white or pink from head to toe, including their eyes.
Willow and Bahloo are not albino: they have black spots or patches on their bodies. It’s more likely that they have leucism, a condition where all pigment types are lost in patches of cells.
Even though Migaloo is all white, scientists are skeptical that he is albino because he doesn’t have red or pink eyes—like other humpbacks, he has brown eyes. Instead, he’s considered the more conservative “hypo-pigmented,” describing a generic loss of skin color. It’s also possible that Migaloo is leucistic.
The Southern Cross University researchers could analyze his DNA for different genetic variants associated with pigment disorders to pinpoint the exact form. But there are many variants and, as Megan Anderson, who originally tested Migaloo’s DNA, said in a press release, “It’s going to be a long and complex process to test for albinism in this humpback whale as it has not ever been done before.”
And what about the calf? There isn’t enough known about it to be sure.
Are there other white whales that aren’t humpbacks?
Yes! These skin disorders are not exclusive to humpbacks. There have been several other wild spottings of white whales recently.
A white right whale calf (incorrectly described as albino) was filmed last year off the coast of Chile by a group of surfers. Last April, researchers spotted a white killer whale off the coast of Alaska, and they named it “Iceberg.” And a truly albino pink dolphin has been seen around Florida and the Gulf of Mexico repeatedly over the years.
In fact, whales aren’t the only creatures that can lack pigment. A plethora of other all-white examples—such as koalas, penguins, and gorillas—can be found throughout the animal kingdom.
August 30, 2013
You’re at the beach for a weekend with family or friends. Splashing and jumping, dunking your head beneath the waves, you start to cool off. Then you feel something soft brush against your leg—and suddenly, the coolness is replaced by a hot, shooting pain. You’ve been stung by a jellyfish. But what do you do now?
First let’s take a look at exactly what’s happening to your leg. Jellyfish have special cells along their tentacles called cnidocytes. Within these cells are harpoon-like structures full of venom, called nematocysts. The nematocysts shoot out when triggered by touch and can penetrate human skin in less time than it takes you to blink.
Once the venom is injected into your skin, the pain, redness and blistering begin. One of the main causes of this discomfort is a type of protein called a porin found in the venom of all jellyfish—and in all their relatives, including corals and anemones, which together form a group of creatures collectively known as cnidarians. Angel Yanagihara, a research professor studying box jellyfish venom at the Pacific Biosciences Research Center at the University of Hawaii, explains that the porins in box jellyfish are fast-acting and “promiscuous:” they are indiscriminate and “will punch holes in all types of cells” including blood, skin and nerve cells. The complex concoction of these proteins varies (along with the stinging cell mechanism) from species to species, which is why we might only feel a small sticky sensation when we come in contact with some anemones, while a box jelly sting may cause a trip to the emergency room or even kill you.
So after you’re stung, you should pee on it, right? Or get someone else to? That’s what you’ve seen on TV—maybe you’re thinking of a certain incident from Friends. But don’t pull those board shorts off too quickly—urine can do a lot of things, but it doesn’t help the sting. It may actually make it worse.
That’s because pouring freshwater—or urine—on the area will change the composition of the solution surrounding the remaining cells and may actually trigger the release of more nematocysts and venom. Instead, experts suggest rinsing the area with saltwater to help reduce discomfort. Before you do any rinsing, however, remove any jellyfish tentacles that remain on the skin, as nematocysts on loose tentacles can continue to sting even after they are detached from the jelly. Making sure that sand stays clear of the wound is also an important task, but likely a difficult one while on the beach. In the case of a box jelly sting, it would be helpful to have Yanagihara nearby with the two treatments she has developed—or even better would be to make use of her preventive ointment before going in the water. Because these aren’t yet available to the public, putting vinegar on the affected area and seeking medical attention are the suggested treatments.
It’s good to have this information in-hand when you go to the beach just in case—though it’s unlikely that you’ll be stung. But that possibility could be on the rise if, as has been suggested, jellyfish numbers are increasing. A study from April 2012 in Hydrobiologia found increasing jellyfish populations in 62 percent of the regions analyzed, including coastal areas of Asia, the Black Sea and the Mediterranean Sea. “Our study confirms these observations scientifically after analysis of available information from 1950 to the present for more than 138 different jellyfish populations around the world,” said Lucas
Brotze Brotz, the lead author of the study in a press release.
However, jellyfish are a difficult species to study: their life cycles aren’t well understood, and catching them by net is not a good option due to their fragile, gelatinous bodies. Because of this, sweeping claims about global changes in jellyfish populations are up for debate. Their historical numbers are largely unknown, making it hard to be sure whether jellyfish populations are increasing over the long term, or whether the increases we see are a part of natural population fluctuations or an artifact of more people reporting sightings. And there is evidence for these caveats: a different 2012 study found that the perceived rise in the number of jellyfish is actually the peak of a normal 20-year boom and bust cycle.
But if jellyfish are increasing globally, it is likely that human influences are the cause. Overfishing has reduced some jellies’ competition for food; increased nutrients running into the ocean create oxygen-depleted environments that jellies can tolerate better than other animals; and warmer water can help some species of jellyfish larvae to grow more quickly. Even jellies without a nasty sting can cause problems, clogging up pipes in nuclear power plants that use seawater to cool their reactors and pushing fish out of the ecosystem.
There still is much to learn about the fascinating and pulsing lives of jellyfish that can help to determine if their populations are increasing long-term. Scientists are making use of observant beachgoers, with websites where you can input your jelly sightings onto a map to generate global data on jelly populations. So if you do have the bad luck to get stung by a jellyfish, remember: wash it with salt water, not pee, and maybe pop your location into the map to help us all learn something from the experience.
Learn more about the ocean from the Smithsonian’s Ocean Portal.
August 5, 2013
People have been fascinated and terrified by sharks for thousands of years, so you would think that we know a fair bit about the roughly 400 named species that roam the ocean. But we have little sense of how many sharks are out there, how many species there are, and where they swim, let alone how many existed before the advent of shark fishing for shark fin soup, fish and chips, and other foods.
But we are making progress. In honor of Shark Week, here’s an overview of what we have learned about these majestic citizens of the sea in the past year:
1. Sharks mostly come in shades of gray, and it’s likely that they only see that way as well. Now, that knowledge is being put to use to protect surfers and swimmers offshore. In 2011, researchers from the University of Western Australia found that, out of 17 shark species tested, ten had no color-sensing cells in their eyes, while seven only had one type. This likely means that sharks hunt by looking for patterns of black, white and grey rather than noticing any brilliant colors. To protect swimmers, whose bodies often look like a tasty seal from below, the researchers are working with a company to design wetsuits that are striped in colorblocked disruptive patterns. One suits will alert sharks that they aren’t looking at their next meal, and a second suit that will help camouflage swimmers and surfers in the water.
2. The thresher shark has a long, scythe-shaped tail fin that scientists long-suspected was used for hunting, but they didn’t know how. This year, they finally filmed how the thresher shark uses it to “tail slap” fish, killing them on impact. It herds and traps schooling fish by swimming in increasingly smaller circles before striking the group with its tail. This strike usually comes from above instead of sideways, an unusual technique that allows the shark to stun multiple fish at once—up to seven, the study found. Most carnivorous sharks only kill one fish at a time and so are comparatively less efficient.
3. How many sharks do people kill each year? A new study published in July 2013 used available shark catch information to estimate the global number—a staggering 100 million sharks killed every year. Although the data are incomplete and often do not include those sharks whose fins are removed and bodies are thrown back to sea, this is the most accurate estimate to date. Slow growth and low birth rates of sharks mean that they are not able to repopulate fast enough to catch up with the loss.
4. The 50-foot giant megalodon shark is a staple of shark week, reigning as the great white’s larger and even more terrifying ancestor. But a new fossil discovered in November turns that supposition on its head: it looks like the megalodon isn’t a great white shark ancestor after all, but is more closely related to the fish-munching mako sharks. The teeth of the new fossil look more like great white and ancient mako shark teeth than megalodon teeth, which also suggests that great whites are more closely related to mako sharks than previously thought.
5. Sharks are worth more alive in the water than dead on the plate (or bowl). In May, researchers found that shark ecotourism ventures—such as swimming with whale sharks and coral reef snorkeling—bring in 314 million U.S. dollars globally every year. What’s more, projections show that this number will double in the next 20 years. In contrast, the value of fished sharks is estimated at 630 million U.S. dollars and has been declining for the past decade. While dead sharks’ value terminates after they are killed and consumed, live sharks provide value year after year: in Palau, an individual shark can bring up to 2 million dollars in benefits over its lifetime from the tourist dollars that pour in just so that people can view the shark up close. One citizen science endeavor even has snorkeling travelers snapping photos of whale sharks in an effort to help researchers. Protecting sharks for future ecotourism endeavors just makes the most financial sense.
6. Bioluminescence isn’t just for jellyfish and anglers: even some sharks are able to light up to confuse predators and prey alike. Lanternsharks are named for this ability. It’s been long known that their bellies light up to blend in with sunlight shining down from above, an adaptation known as countershading. But in February, researchers reported that lanternsharks also have “lightsabers” on their backs. Their sharp, quill-like spines are lined with thin lights that look like Star Wars weaponry and send a message to predators that, “if you take a bite of me, you might get hurt!”
7. What can an old sword tell us about sharks? Far more than you might expect—especially when those swords are made of shark teeth. The swords, along with tridents and spears collected by Field Museum anthropologists in the mid-1800s from people living in the Pacific’s Gilbert Islands, are lined with hundreds of shark teeth. The teeth, it turns out, come from a total of eight shark species—and, shockingly, two of these species had never been recorded around the islands before. The swords give a glimpse into how many more species once lived on the reef, and how easy it is for human memory to lose track of history, a phenomenon known as “shifting baselines.”
8. Sharks know some pretty neat tricks even before they’re born. Bamboo shark embryos develop in egg cases that float on the high seas, where they are vulnerable to being eaten by all manner of predators. Even as developing embryos, they can sense electric fields in the water given off by a predator—just like adults. If they sense this danger nearby they can hold still, even stopping their breathing, so they won’t be noticed in their egg cases. But for sand tiger shark embryos, which develop inside the mother, their siblings can pose the biggest threat—the first embryos to hatch from eggs, at just roughly 100 millimeters long, will attack and devour their younger siblings.
9. Shark fin soup has been a delicacy in China for hundreds of years, and its popularity has only increased in the last several decades with the country’s growing population. This increasing demand has heightened the number of sharks killed every year, but the expensive dish may be losing some fans.
Even before last year’s Shark Week, the Chinese government banned the serving of shark fin soup at official state banquets—and the conversation hasn’t died down since. Countries and states banning the trade of shark fins and regulating the practice of shark finning have made headlines this year. And just a few weeks ago, New York Governor Andrew Cuomo signed a ban of the possession and sale of shark fins in the state that will go into effect in 2014.
10. Shark fin bans aren’t the only method of protecting sharks. The island nations of French Polynesia and the Cook Islands created the largest shark sanctuary in December of 2012—protecting sharks from being fished in an area of over 2.5 million square miles in the south Pacific Ocean. And member countries of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) voted to place export restrictions on five species of sharks in March 2013. Does this mean that the general perception of sharks is changing for the better and that the public image of sharks is veering away from its “Jaws” persona? That, in essence, is up to you!
–Emily Frost, Hannah Waters and Caty Fairclough co-wrote this post
July 11, 2013
When most people think about organisms growing on the seafloor around Antarctica (if they think of them at all), a few short words come to mind: cold, slow, and dull. But under the right conditions, seafloor life on Antarctia’s continental shelf can grow very quickly, according to new research published today in Current Biology. The collapse of ice shelves in the Antarctic over the past two decades due to warmer waters bathing their undersides has already changed seawater conditions enough to allow typically slow-growing communities of glass sponges to sprout up under the more transient sea ice that has replaced the shelf.
“These things aren’t as unexciting as we thought; they are actually very dynamic,” says polar ecologist James McClintock of the University of Alabama, who was not involved in the research. “The idea that they [glass sponges] could recruit and grow rapidly when these ice shelves break up is exciting, and suggests that the seafloor is going to change more quickly than we imagined.”
Glass sponges are the architects of the most diverse community on the seafloor under ice shelves. Like corals, glass sponges provide habitat for many other organisms. Their basket-like inner cavities are rare nurseries in the cold water, and small marine isopods, juvenile starfish, brittle stars, and even fish eggs have been found inside. As they die, they leave behind silica mats meters deep on the seafloor, providing prime substrate for crinoids, anemones, and other sponges to settle and grow. Also like corals, glass sponges grow slowly. Most grow only two centimeters each year, which makes the largest ones hundreds of years old.
Food scarcity is the reason for this slow growth. Antarctic waters have a very short growing season just weeks long, when sunlight and warmer water foster blooms of phytoplankton. During this brief period, phytoplankton feeds zooplankton, and waste products from the latter organisms feed bacteria and animals (like glass sponges) that filter particles and bacteria from the water. Even how much of that bounty an animal receives depends on whether it has settled in a current carrying food–or if those manna-bringing currents are blocked by ice. That said, it’s no surprise that, with so little food available, most organisms on the seafloor grow very slowly.
Ice also poses a hazard to life on the Antarctic seafloor. Icebergs and other types of sea ice, if they encounter shallower waters from where they calved, can dig ditches into the seafloor up to 350 meters wide and 15 meters deep, obliterating any living organisms from the area. Ice crystals (known as anchor ice) can grow on non-moving objects such as sponges, rocks and seaweed, eventually causing them to float up from the seafloor and merge with the ice ceiling. Additionally, brinicles, icy fingers of saltwater, shoot down from frozen ice at the surface, killing everything they touch as they spread across the seafloor.
But the past couple decades have seen changes to the ice cover in the Antarctic. Two large ice shelves known as Larsen A and Larsen B collapsed in 1995 and 2002 respectively. This freed more open water for phytoplankton to bloom, left more seafloor area free from regular iceberg scraping, and potentially altered how warm water and food circulate through the area. But given the slow pace of life in Antarctica, scientists weren’t expecting to find much when in 2011 they cut through the transient sea ice to survey the
seafloor once beneath the Larsen A ice shelf . Much to their surprise, they discovered that communities of small glass sponges had sprung up in the four years since their last visit.
In fact, the numbers of glass sponges had doubled, many belonging to smaller species that are not as common on older Antarctic sponge reefs. And the researchers saw a large increase in the number of sponges between 50-100 square centimeters in volume, suggesting that the young sponges had grown very quickly—and certainly more quickly than just two centimeters a year.
The sudden availability of free space and an influx of food likely explain how these sponges were able to grow so quickly. But where did this extra food come from? Paul Dayton of the Scripps Institution of Oceanography, who studied the ecology of Antarctica’s surrounding sea floor for many years but was not involved in this study, hypothesizes that the melting of the ice shelves increased currents, waves and wind in the area, stirring up the seafloor and resuspending particles and bacteria for the sponges to eat.
The study of the growth of one community in one part of the Antarctic may seem small. But it’s an example of how we can’t predict how ecosystems are going to react to climate change. It’s possible that glass sponges will be “winners,” able to grow better in the particle-heavy water mixed up by currents, or it may just be a short-term change. “I personally see this more as a pulse than [a community] being taken over by glass sponges,” says Dayton. “But with the huge changes coming down as a result of warming and loss of sea ice, it very well could result in a massive change in the Antarctic benthic community.”