Size Does Matter. Brain Size!

Big brains, but all they
want to talk about is mackerel. 

(Discover Magazine, Sept, 11, 2012) - Every whale and dolphin evolved from a deer-like animal with slender, hoofed legs, which lived between 53 and 56 million years ago. 

Over time, these ancestral creatures became more streamlined, and their tails widened into flukes. They lost their hind limbs, and their front ones became paddles. And they became smarter.  Today, whales and dolphins – collectively known as cetaceans – are among the most intelligent of mammals, with smarts that rival our own primate relatives.

Now, Shixia Xu from Nanjing Normal University has found that a gene called ASPM seems to have played an important role in the evolution of cetacean brains. The gene shows clear signatures of adaptive change at two points in history, when the brains of some cetaceans ballooned in size. But ASPM has also been linked to the evolution of bigger brains in another branch of the mammal family tree – ours. It went through similar bursts of accelerated evolution in the great apes, and especially in our own ancestors after they split away from chimpanzees.

It seems that both primates and cetaceans—the intellectual heavyweights of the animal world—could owe our bulging brains to changes in the same gene. “It’s a significant result,” says Michael McGowen, who studies the genetic evolution of whales at Wayne State University. “The work on ASPM shows clear evidence of adaptive evolution, and adds to the growing evidence of convergence between primates and cetaceans from a molecular perspective.”

For decades, we’ve known that similarities between primate and cetacean intelligence run deep. For a start, both groups have members with unusually big brains. We humans have brains that are 7 times bigger than you’d expect for an animal of their size. The equivalent number is 2-3 for chimps and some monkeys, and 4-5 for some dolphins.

Over the last decade, scientists have identified seven genes that are linked to primate brain size. They’re called MCPH1 to MCPH7 (ASPM is the fifth in the line). Faults in these genes can lead to microcephaly – a developmental disorder characterised by a debilitatingly small brain.

McGowen had already shown that, unlike in humans, MCPH1 doesn’t neatly correlate with brain size in cetaceans. Xu wanted to see if ASPM would be more interesting. He sequenced the gene in fourteen species of cetaceans, from the bottlenose dolphin to the minke whale. He then compared these to known sequences from 18 other mammals, including several primates and the hippopotamus (the closest living relative to cetaceans).

Xu found that ASPM went through two periods of strong positive selection – where beneficial new versions of the gene spread through a population. The first coincides with the point when toothed whales (like sperm whale and dolphins) split away from the baleen whales (like blue, fin and humpback whales). Their brains got bigger. The second period marks the split of the toothed whales into the delphinoids (including all oceanic dolphins and porpoises) and all the others. The delphinoids’ already big brains got bigger still.

Xu also found signatures of positive selection within the ASPM genes of primates, but not in any other mammal groups. During their history, both groups must have experienced some evolutionary pressures that meant bigger brains suddenly became advantageous. We can only speculate what these might have been. For cetaceans, the toothed whales evolved to navigate with echolocation, and may have needed a larger brain to process the information from all the returning echoes. The delphinoids may owe their larger brains to the mental demands of living in large, complex social groups. (Both hypotheses have been on the cards for some time, and Xu’s ASPM discovery doesn’t provide a smoking gun for either.)

What does ASPM actually do? The gene is activated in neuroblasts, the embryonic cells that eventually divide into neurons. It helps to create structures in dividing cells that send a full complement of DNA into each daughter. If ASPM isn’t working properly, the neuroblasts cannot divide evenly, and brains get smaller. It’s not clear how the reverse happens – how changes in ASPM lead to bigger brains, but it’s now clear that this has happened in at least two mammal groups.

Xu found certain mutations that were associated with the bigger brains of toothed whales, and others that are associated with the even bigger brains of delphinoids. What these mutations did is anyone’s guess, and something that will take a lot of experimental work to uncover.

Here’s one critical nugget, though: they’re different to the changes you see in primates. The same gene may have enlarged the brains of both groups, but it did so in different ways. And undoubtedly, other genes were also involved.

(To close, here’s possibly my favourite ever example of convergent evolution, which also involves cetaceans. Toothed whales and some bats both use echolocation, and their abilities depend on the same changes to the same gene – Prestin. This was discovered at the same time by two independent groups of researchers, one led by Yang Liu and the other by Ying Li!)

Reference: Xu, Chen, Cheng, Yang, Zhou, Xu, Zhou & Yang. 2012. Positive selection at ASPM gene coincides with brain size enlargements in cetaceans. Proc Roy Soc B.

'Once in a lifetime' rare white whale calf spotted off Australia

The Telegraph.co.uk (Sept. 29, 2011) - An extremely rare white humpback whale calf has been spotted near Australia's Great Barrier Reef in an event witnesses described Thursday as a "once in a lifetime experience".

Believed to be just a few weeks old, the baby humpback was seen at Cid Harbour in the famous reef's Whitsunday Islands area by local man Wayne Fewings, who was with his family in a boat when he spotted a whale pod.

"We were just drifting when I noticed the smaller whale in the pod was white. I couldn't believe my eyes, and I just grabbed my camera," Fewings said.

"Then the white calf approached my boat, seeming to want to check us out. I was just so amazed at seeing this animal, it made me think how truly astounding the Great Barrier Reef is," he added of the sighting on Saturday.

"I feel very lucky to have witnessed this, it's a once in a lifetime experience."

Reef official Mark Read said white whales were highly unusual, with only 10-15 believed to exist among the 10,000-15,000 humpbacks living along Australia's east coast, and purely white ones – like the calf spotted on Saturday – rarer still.

Its parents could both have been dark humpbacks carrying the recessive white whale gene, but Read said one or either may also have been white themselves, raising speculation it was the offspring of famous white humpback Migaloo.

Migaloo – the name is an Aboriginal word meaning "whitefella" – is the world's best-known all-white humpback and has built up a loyal following in Australia since first being sighted in 1991.

Humpback whales are currently on their southern migration and Mr Read said the baby white would be feeding heavily from its mother as it laid down fat stores for the "cold Antarctic waters."

Its sex was unknown and Read said there were no plans to bestow the young mammal with a name of its own.

"We'd be pretty comfortable for him or her just to simply remain anonymous and just live out its life in relative peace and harmony," Read said.

Australia's east coast humpback population has been brought back from the brink of extinction following the halting of whaling in the early 1960s, he added, describing it as a "conservation success story."

Former Trainer Says Killer Whale Captivity Causes Attacks

Wired Science (Sept. 20, 2011) - On Sept. 19, a federal hearings began on the safety of keeping killer whales in captivity. Convened by the Occupational Health and Safety Administration in the aftermath of two fatal attacks on trainers, the hearings won’t consider the safety of killer whales — but according to former SeaWorld trainer Jeff Ventre, the two issues are inseparable.

An animal-loving Florida kid who majored in biology and rose to trainer stardom in Shamu Stadium before being fired, Ventre says the attacks that killed Dawn Brancheau at SeaWorld and Alexis Martinez at Loro Parque are manifestations of stress, even madness, in animals forced into miserable, unnatural conditions.

“Killer whales don’t attack humans in the wild,” said Ventre. “What we’ve seen in these injuries to people is a direct byproduct of the stress associated with captivity.”

Ventre was fired in 1995. SeaWorld says it was for being careless; Ventre says it’s because he’d become critical of the industry. Wired recently talked to Ventre, who has since become a medical doctor and cetacean advocate, about his work.

Wired: When did your feelings about keeping killer whales in captivity begin to change?

Jeff Ventre: When I started, I was just happy to have the job. It was amazing to see dolphins and sea lions and killer whales, despite the fact that they were in captivity. I thought there was going to be a lot of science, too. I’d grown up with Jacques Cousteau programming. Over time I found out there wasn’t much science going on. It was just a different version of the circus. Over time, that wears on you.

I did two different tours of duty at Shamu Stadium. The first time I was there, I was an apprentice. I did a lot of bucket-scrubbing, blue-collar type work, and had only a little water experience. Then I went around to the other stadiums, where they had dolphins, belugas and false killer whales, and honed my waterwork abilities. Then I was brought back to Shamu Stadium in 1994, where I spent my last two years. It was that second tour of duty that was somewhat enlightening.

By that time I’d learned enough about killer whales that I began to realize that what we were telling students coming in for education shows was at odds with what was true.

Wired: Give me an example.

Ventre: We were telling people that the animals lived to maybe 20 years old. But in reality, I knew that females lived to be 50, and males to be 30. That was a red flag. I also began to realize that all the killer whales in captivity had broken teeth. That seemed odd to me, because we were feeding them dead fish.

It’s because, when you put on a live public performance, or do a training session, you have to separate the killer whales with steel gates. These have horizontal bars on them. If you’ve ever seen two dogs on the opposite side of a fence barking, this is two orcas on the opposite side of a gate. Sometimes they charge the gate and bite down on the bars.

This knocks off the enamel and exposes the pulp of the tooth. This fleshy pulp is then drilled out by a veterinarian. What you have is a hollow tooth, creating a corridor down into the jaw itself. So for the rest of that animal’s life, they need to get their teeth flushed two or three times a day. In humans, it’s known that poor dentition leads to heart disease, kidney disease and stroke. These orcas are essentially left with a diseased mouth.

Wired: What are other ways in which killer whales are poorly suited for captivity?

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How Far Will Dolphins Go to Relate to Humans?

New York Times Science (Sept. 19, 2011) - OFF THE BAHAMAS — In a remote patch of turquoise sea, Denise L. Herzing splashes into the water with a pod of 15 Atlantic spotted dolphins. For the next 45 minutes, she engages the curious creatures in a game of keep-away, using a piece of Sargassum seaweed like a dog’s chew toy.

Dr. Herzing is no tourist cavorting with marine mammals. As the world’s leading authority on the species, she has been studying the dolphins for 25 years as part of the Wild Dolphin Project, the longest-running underwater study of its kind.

“I’m kind of an old-school naturalist,” she said. “I really believe in immersing yourself in the environment of the animal.”

Immerse herself she has. Based in Jupiter, Fla., she has tracked three generations of dolphins in this area. She knows every animal by name, along with individual personalities and life histories. She has captured much of their lives on video, which she is using to build a growing database.

And next year Dr. Herzing plans to begin a new phase of her research, something she says has been a lifetime goal: real-time two-way communication, in which dolphins take the initiative to interact with humans.

Up to now, dolphins have shown themselves to be adept at responding to human prompts, with food as a reward for performing a task. “It’s rare that we ask dolphins to seek something from us,” Dr. Herzing said.

But if she is right, the dolphins will seek to communicate with humans, and the reward will be social interaction itself, with dolphins and humans perhaps developing a crude vocabulary for objects and actions.

Other scientists are excited by the project. “ ‘Mind-blowing’ doesn’t do justice to the possibilities out there,” said Adam Pack, a cetacean researcher at the University of Hawaii at Hilo and an occasional collaborator with Dr. Herzing. “You’ve got crystal-clear warm water, no land in sight and an interest by this community of dolphins of engaging with humans.”

How far will dolphins go to engage?

“The key is going to be coming up with a system in which the dolphins want to communicate,” said Stan Kuczaj, director of the Marine Mammal Behavior and Cognition Laboratory at the University of Southern Mississippi. “If they don’t care, it won’t work.”

Dr. Kuczaj developed an early two-way communication system while working at a captive lab in Orlando in the late 1980s. The system relied on visual symbols, not sound, and used a large stationary keyboard that proved to be too cumbersome.

But he says that the effort gave him confidence that such a system could work and that Dr. Herzing is “definitely the closest to getting there.”

“If it works,” he said, “it’ll be a huge step forward.”

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Zoo Death Stirs Debate About Keeping Dolphins in Captivity

Wired Science (Sept. 14, 2011) - The death of a young bottlenose dolphin at a Chicago zoo was accidental, but some biologists say it shows why dolphins shouldn’t be kept in captivity for entertainment.

The dolphin, a 4-year-old named Nea, died on the afternoon of Sept. 5 at the Brookfield Zoo. According to a zoo press release, trainers heard “a loud pop” from the pool, apparently the sound of two dolphins colliding. Nobody reported seeing the collision, but it’s thought to have happened in the air as the animals jumped. Nea died minutes later from a fractured skull.

Zoo officials described it as a “freak incident,” ascribing it to typical roughhousing gone awry. But crowding dolphins into small, unnatural environments makes accidents more likely, said Wild Dolphin Project biologist Denise Herzing.

“Dolphins whack each other in the wild. That’s part of their aggressiveness. But in captivity, there’s less room,” said Herzing. “This isn’t the first time dolphins have had an accident in the air. Certainly there have been dolphins jumping out of tanks. The restricted lives of dolphins jumping in a pool can impact their ability to do what they normally do.”

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