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.
October 31, 2013
Octopuses, those whip-smart but bizarre cephalopods, seem to embody everything creepy and mysterious about the sea–the thought of their soft squishy bodies lurking in the oceans’ dark reaches has inspired monsters ranging from the Kraken to the Caribbean Lusca. Their otherworldly forms, heightened by unfurling tentacles, find their way into more modern monsters and villains too–think Disney’s sea witch Ursula or Spider-Man’s Doc Oc. And don’t forget the octopus-themed horror movies!
A new book, Octopus! The Most Mysterious Creature in the Sea, by Katherine Harmon Courage, comes out today. Harmon Courage takes a deep dive into all things octopus, ranging from their culinary use in dishes around the world to their tragic sex lives. Here, we highlight a few of the fascinating points covered in the book.
1) Octopuses are waaay old. The oldest known octopus fossil belongs to an animal that lived some 296 million years ago, during the Carboniferous period. That specimen belongs to a species named Pohlsepia and is on display at the Field Museum in Chicago. Harmon Courage describes it as a “flattened cow patty” or a “globular splat,” but a close examination reveals the tell-tale eight arms and two eyes. Researchers aren’t sure, but possibly there’s an ink sack there, too. In other words, long before life on land had progressed beyond puny pre-dinosaur reptiles, octopuses had already established their shape for the millions of years to come.
2) Octopuses have three hearts. Two of the hearts work exclusively to move blood beyond the animal’s gills, while the third keeps circulation flowing for the organs. The organ heart actually stops beating when the octopus swims, explaining the species’ penchant for crawling rather than swimming, which exhausts them.
3) The plural of octopus is octopuses. The world “octopus” comes from the Greek, októpus, meaning “eight foot.” The word’s Greek roots means it’s pluralized as a Greek word, too, which depends on both a noun’s gender and the last letter it ends with. In this case, an -es is simply tacked on. So no octopi, octopodes or octopussies, Harmon Courage points out.
4) Aristotle thought octopuses were dumb. In his History of Animals, written in 350 BC, the Greek philosopher wrote that ”The octopus is a stupid creature, for it will approach a man’s hand if it be lowered in the water; but it is neat and thrifty in its habits: that is, it lays up stores in its nest, and, after eating up all that is eatable, it ejects the shells and sheaths of crabs and shell-fish, and the skeletons of little fishes.” After describing a few more quirks of octopus life history–it ejects ink for self-defense, it’s slimy, it can crawl on land–he flippantly signs off, “So much for the mollusca.” However, the big-brained cephalopod can navigate through mazes, solve problems and remember solutions, and take things apart for fun–they even have distinct personalities.
5) Octopus tentacles have a mind of their own. Two-thirds of an octopus’ neurons reside in its tentacles, not its head. As a result, the tentacles can problem solve how to open a shellfish while their owners are busy doing something else, like checking out a cave for more edible goodies. The tentacles can even react after they’ve been completely severed. In one experiment, severed tentacles jerked away in pain when researchers pinched them.
6) Octopus ink doesn’t just hide the animal. The ink also physically harms enemies. It contains a compound called tyrosinase, which, in humans, helps to control the production of the natural pigment melanin. But when sprayed in a predator’s eyes, tyrosinase causes a blinding irritation. It also garbles creatures’ sense of smell and taste. The defensive concoction is so potent, in fact, that octopuses that do not escape their own ink cloud can die.
7) Octopuses have blue blood. To survive in the deep ocean, octopuses evolved a copper rather than iron-based blood called hemocyanin, which turns its blood blue. This copper base is more efficient at transporting oxygen then hemoglobin when water temperature is very low and not much oxygen is around. But this system also causes them to be extremely sensitive to changes in acidity. If the surrounding water’s pH dips too low, octopuses can’t circulate enough oxygen. As such, researchers worry about what will happen to the animals as a result of climate change-induced ocean acidification.
8) Octopuses, to some, are erotic muses. Japan’s notorious “tentacle erotica” traces back to an 1814 woodblock print (potentially NSFW) titled Tako to Ama, or “Octopus and the Shell Diver.” According to Courage, the image takes inspiration from a legend about a female shell diver who is chased by sea creatures, included octopuses, after attracting the eye of a sea dragon god.
9) After mating, it’s game over for octopuses. Mating and parenthood are brief affairs for octopuses, who die shortly after. The species practices external fertilization. Multiple males either insert their spermatophores directly into a tubular funnel that the female uses to breathe, or else literally hand her the sperm, which she always accepts with one of her right tentacles (researchers do not know why). Afterwards, males wander off to die. As for the females, they can lay up to 400,000 eggs, which they obsessively guard and tend to. Prioritizing their motherly duties, females stop eating. But she doesn’t starve to death–rather, when the eggs hatch, the female’s body turns on her. Her body undertakes a cascade of cellular suicide, starting from the optic glands and rippling outward through her tissues and organs until she dies.
10) Most octopus for human consumption comes from North and West Africa. Octopus has been a popular food item in East Asia, Spain, Greece and other countries for centuries, and recently, it has gained popularity in the U.S. and beyond. Today, Koreans consume the most octopus. But that popularity has had an impact on octopus stocks in oceans around the world. In Japan, for example, octopus catches plummeted by 50 percent between the 1960s and the 1980s. The international demand for octopus inspired North and West African fisheries to start targeting the animals in the 80s, although recently demand has taken a toll on those waters as well, shifting fisheries from Morocco to Mauritania and, more recently, Senegal. According to the U.N. Food and Agriculture Organization, around 270,000 tons of octopus is imported by various countries around the world each year.
October 16, 2013
We often hear about melting sea ice, rising tides and bleached coral reefs, but climate change is poised to reverberate through a broader swath of the marine environment than these headline issues alone might suggest.
According to a new study published in PLoS Biology, “the entire world’s ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity.” As the ocean’s biogeochemistry shifts, the paper reports, so too will its habitats and the creatures living there. This could mean hardship for some 470 to 870 million people–many of whom live in poverty–who depend upon the bounty of the sea to support livelihoods and fill dinner plates. And these impacts are not predicted to occur centuries down the road, either: according to the study, they may transpire as soon as 2100.
Nearly 30 scientists from around the world–including climate modelers, ecologists, biogeochemists and social scientists–co-authored the study. They built upon computer models from the Intergovernmental Panel for Climate Change by compiling data from 31 Earth System Models that included at least one ocean parameter. All told, 27,000 years’ worth of data of the various overlapping, aggregated variables were compiled into their new model.
With those data compiled, they then modeled two different future scenarios: one in which atmospheric carbon dioxide concentrations increase to 550 parts per million, and another in which they hit 900 ppm (the planet currently stands at about 400 ppm, as compared to pre-industrial times, when that measurement was 280 ppm). The former model represents values predicted if mitigation efforts are undertaken, while the latter is predicted for a “business-as-usual” scenario where we maintain current levels of greenhouse gas emissions into the future.
Their model predicted changes in temperature, oxygen levels, increased acidity and productivity (the creation of organic compounds by primary producers like phytoplankton) on both the ocean surface and the sea floor under those two future scenarios. Nearly across the board on the ocean’s surface, they found, their models predicted a continued warming and rise in acidity accompanied by a decline in oxygen and productivity. The only exception was in a small fraction of the sea in polar regions, where the sea surface would experience increased oxygen and productivity. The magnitude of these predicted changes, they write, will be greater than any comparable shifts over the past 20 million years.
“When you look at the world ocean, there are few places that will be free of changes; most will suffer the simultaneous effects of warming, acidification, and reductions in oxygen and productivity,” Camilo Mora, a geographer at the University of Hawaii at Mānoa, said in a press release.
The most drastic impacts, they found, will occur on the ocean’s surface, but the seafloor will also experience its share of smaller but still significant changes. Seafloor temperature and acidity will change only slightly compared to the surface, but there will be large reductions in the influx of carbon, which provides food for many bottom-dwelling organisms. The drop in dissolved oxygen on the sea floor will be similar to that experienced on the surface.
These changes may be enough to disrupt the ocean floor’s delicate ecosystem. ”Because many deep-sea ecosystems are so stable, even small changes in temperature, oxygen, and acidity may lower the resilience of deep-sea communities,” Lisa Levin, an oceanographer at the University of California, San Diego, and co-author of the paper, said in the release. “This is a growing concern as humans extract more resources and create more disturbances in the deep ocean.”
As for the surface, the magnitude of the projected changes will vary by place. The tropics will experience the smallest changes in acidity; temperate regions will suffer the least significant shifts in temperature and productivity; and the Southern Ocean near Antarctica will be spared the least fluctuations in oxygen. But overall, across the board the ocean surface will suffer significant impacts.
With those data in hand, they then overlaid habitat and biodiversity hot spot information for 32 diverse marine environments around the world to see how these changes would impact ocean flora and fauna. Coral reefs, seagrass beds and other shallow areas will suffer the greatest impacts, they found, while deep ocean seamounts and vents will suffer the least.
Humans will not be spared the repercussions of those changes. In a final analysis, they quantified humanity’s dependence on the ocean by analyzing global jobs, revenues and food that comes from the sea. Most of the up to 870 million people who will be affected most by these changes live in some of the world’s poorest nations, they found.
While these predictions are subject to the same limitations that plague any computer model that attempts to represent a complex natural system and project its future fate, the authors believe that the results are robust enough to strongly support the likelihood that our oceans will be very different places in the not-too-distant future. If carbon dioxide levels continue to rise, they write, “substantial degradation of marine ecosystems and associated human hardships are very likely to occur.”
“It is truly scary to consider how vast these impacts will be,” co-author Andrew Sweetman of the International Research Institute of Stavanger, Norway, emphasized in the press release. “This is one legacy that we as humans should not be allowed to ignore.”
September 25, 2013
Sure, it’s not much to look at. But stare long enough, and you’ll see a jaw (jutting out towards the right), a pair of nostrils (small perforations directly above the mouth cavity) and even a tiny eye socket (just above the mouth, to the left of the nostrils, staring out sideways).
This admittedly homely fish fossil, the 419-million-year old Entelognathus primordialis, was recently discovered in China and described for the first time in an article published today in Nature. What makes it remarkable is everything that’s come after it: It’s the oldest known creature with a face, and may have given rise to virtually all the faces that have followed in the hundreds of millions of years since, including our own.
The uncommonly well-preserved, three-dimensional fossil, analyzed by a group of researchers from the Chinese Academy of Sciences, was excavated near Xiaoxiang Reservoir in Southeast China, in a layer of sediment that dates to the Silurian period, which ranged from roughly 419 to 443 million years ago. All other fish specimens from this era are jawless fish (a group of more primitive creatures that still live on today as lampreys and hagfish), so this is the first one that has what we might call a face: a mouth, nose and two eyes.
It’s difficult to conclude very much about the behavior or lifestyle of the ancient creature, but we do know that it swam in water (land animals didn’t begin to evolve until the Devonian period, which spanned 359 to 419 million years ago) and was likely a top-level predator of the early ocean ecosystem.
What has scientists so excited, though, is that the particular anatomical features of this fossil could upend our understanding of how vertebrates evolved over time. “When I first saw this, I was completely blown away,” says Matt Friedman a paleobiologist at the University of Oxford that reviewed the paper and wrote an accompanying article in Nature. “It’s the kind of fossil you might see once or twice in your lifetime, as a research scientist.”
Friedman and others find the fossil so remarkable because it combines a series of characteristics from two different groups: placoderms, an ancient class of armored fish that went extinct millions of years ago, and bony fish, a lineage that gave rise to all modern fish with jaws and bone skeletons. Previously, it was assumed that placoderms died out completely (and that the other, more recent types of fish with similar armor plating had independently re-evolved it much later), while a different, shark-like group of fish called acanthodians led to the bony fishes.
“What a fossil like this shows is that maybe that’s not the case,” Friedman says. “Because if you look at just the top of the skull and the body, it looks like a placoderm. But when you look at the side, and the front, you see it has jaws that, bone for bone, closely resemble the jaws of bony fish.”
This is significant because of what happened next: bony fish gave rise to all modern vertebrate fish, along with all amphibians, reptiles, birds and mammals, including ourselves. In other words, this fossil might mean that the placoderms didn’t go extinct, but rather evolved into the tremendous diversity of animals that live on both land and sea—and that this ancient, strange-looking face belongs to one of your oldest ancestors.
Scientists won’t immediately jump to reorganize their evolutionary family trees overnight, but the new finding will prompt a period of renewed scrutiny of the previous model. “It’s going to take a while for people to digest it and figure out what it all means,” Friedman says. “From a fossil like this, you’ve got a cascade of implications, and this is just the first paper to deal with them.”
Eventually, though, this finding could help transform our understanding of just how evolution occurred in our planet’s ancient oceans—and how the primitive creatures that swam in them eventually gave rise to the faces we see everyday.
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.