Tag Archives: mammals

The mole rat is unique among the mammal world because of its ability to grow multiple sets of teeth, much in the same manner sharks do. Their teeth aren't that petrifying, though.

The mole rat grows teeth similar to sharks

The mole rat is unique among the mammal world because of its ability to grow multiple sets of teeth, much in the same manner sharks do. Their teeth aren't that petrifying, though.

The mole rat is unique among the mammal world because of its ability to grow multiple sets of teeth, much in the same manner sharks do. Their teeth aren't that petrifying, though.

Humans, as well as most mammals, have only two sets of teeth to make with during their entire lifetime. However, a new research published in the journal Proceedings of the National Academy of Sciences, which studied the dental structure of mole rats has shown that the species is an exception to this rule. In fact, they’re very much similar to sharks, which grow a new set of teeth regularly and change them like a conveyor belt.

In 1957, Stuart Landry first observed that the mole rat had more molars than the average rodent, however this particular fact never interested anyone enough to study the matter further – until now that is, after Helder Gomes Rodrigues from the University of Lyon made this remarkable discovery.

Apart from the mole rat, there are only four other mammals capable of changing their teeth regularly, namely three different manatee species and a pygmy-rock wallaby. Still, the mole rat is unique among mammals, in terms that it has a peculiar up and down movement of its teeth with concomitant rows of teeth sprouting. The other multiple tooth generating mammals first loose their old teeth and then grow a new set, similar to how regular mammals grow a new set after they lose their baby teeth.

X-ray synchrotron microtomographic 3D rendering of the upper dentition of a young mole rat. (c) PNAS

X-ray synchrotron microtomographic 3D rendering of the upper dentition of a young mole rat. (c) PNAS

For his research, Rodrigues analyzed 55 specimens and observed that in each one the back molars in the jaw of the rodents move forward, this although the old one hadn’t come out yet. The researchers saw that by the time the new molars finally reached the first ray, they displayed a very eroded structure from all the wear and tear.

The scientists then sought to find an explanation to this peculiar exception. The manatees and pygmy-rock wallaby have earned the ability to replace their teeth due to the hard elements in their die, however this is not the case with your typical soft plants eating mole rat. Instead, a viable evolutionary explination the researchers have come up with is that their unique ability is due to the fact they primarily dig with their front incisors, they grind things with their molars and swallow abrasive dust.

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Fancy a cup of pigeon milk?

Common sense might tell you that only mammals are capable of lactating, it’s a little know fact, however, that some species of birds are also capable of making milk for their young. The common pigeon produces milk in its crop, located near the esophagus, to feed its young. Scientists have long been wondering how the lactating process takes place for pigeons, but now Deakin University and CSIRO researchers found the gene expression involved. A few years from now we might be all drinking it.

If you find the prospect of such a thing ever happening, consider that its a highly nurturing substance – rich in minerals, protein, fat and antibodies. Since its mainly a bird accustomed and adaptable to all kinds of hazardous environments, pigeon milk is packed full of antioxidants and immune-system-boosting proteins. The pigeon’s e milk is actually a secretion that the parents regurgitate into the young bird’s mouths, helping them grow from their frail infancy. Flamingos and male Emperor penguins, oddly enough, produce it as well.

Deakin University and CSIRO research fellow Tamsyn Crowley said while the function was the same as mammalian milk, the mechanism was completely different.

”We identified a number of immune genes and also found the mechanism by which this process is happening,” she said. ”It’s not like a gland in a mammal that produces the milk. It’s actually part of the crop that falls off and then that is fed to the young.”

The pigeon’s crop, responsible for secreting the milk, is actually part of its digestion chain and is responsible for storing food. The crop however changes immediately prior to lactation in response to hormones and reverts back after lactation, exactly like in any other mammal. The birds begin ”lactating” two-days before the eggs hatch and feed their young for the first 10 days. In the first three days, squabs double their weight daily.
To understand the lactating mechanism in birds, scientists had to sequence the pigeon’s genome, which by their account more or less like flying blind. They did it eventually, of course, after they compared the gene expression of pigeons that do and do not lactate, and eventually compared them to the chicken’s DNA (enough weird science for today; you can’t milk a chicken, don’t worry).They found that the lactating pigeons had over-expression of genes involved with immune response and antioxidant production, as well as genes involved in the production of triglycerides.

‘If you can find proteins that are protecting against disease in pigeons, there’s nothing to say that that can’t be applied in other birds, such as chickens,” she said. ”And that could be a good thing for an industry that is already looking at ways to minimise antibiotics.”

As long as they don’t make lactating chickens, I’m all cool with it. The paper was published in the journal BMC Genomics.

Humpback Whale

Humpack whales flawless natural navigation studied

Humpback Whale

A recently published study 8 years in the making reveals the uncanny ability humpback whales have of following seemingly perfect straight paths for weeks at a time. The navigational precision of humpback whales cannot be explained by known theories.

Humpback whales feed during the summer near polar oceans and migrate to warm tropical oceans for the winter, where they mate and calves are born. This means that during a year a single humpback whale can easily amass 10,000 miles worth of return journeys, making them one of the most farthest migrating animals on Earth. Their migrating paths are perfectly straight, sometimes deviated only by a few degrees, fact that poised researchers to study them and see exactly what mechanism compels the huge watery mammals to become such precise navigators.

Researchers from the University of Canterbury, in Christchurch, tracked 16 radio-tagged whales as they migrated thousands of miles north from the South Atlantic and South Pacific with unswerving accuracy, often covering more than 600 miles but deviating off course by less than one degree.

“Such remarkable directional precision is difficult to explain by established models of directional orientation,” the researchers, led by Travis Horton from the University of Canterbury, wrote in the Royal Society journal Biology Letters.

Each animal was tagged with a special positioning device which attached to the whale from four weeks to seven months before falling out, transmitting precise position data and provided one of the most detailed sets of long-term migratory data for humpbacks ever collected.

Most long-distance traveling animals are believed to navigate using an internal compass that relies either on the earth’s magnetic field or the position of the sun. However, the scientists wrote, “it seems unlikely that individual magnetic and solar orientation cues can, in isolation, explain the extreme navigational precision achieved by humpback whales.”

They instead added, “The relatively slow movements of humpback whales, combined with their clear ability to navigate with extreme precision over long distances, present outstanding opportunities to explore alternative mechanisms of migratory orientation.”

Earth’s magnetism varies too much to explain the whales’ arrow-straight patterns, and you can’t really rely on solar navigation when navigating through water.

“Humpback whales are going across some of most turbulent waters in the world, yet they keep going straight,” said environmental scientist Travis Horton of the University of Canterbury, whose team will publish their findings April 20 in Biology Letters. “They’re orienting with something outside of themselves, not something internal.”

Horton suspects humpbacks rely on both mechanisms, and perhaps the position of the moon or stars. John Calambokidis of the Cascadia Research Collective, suggested a fourth mechanism for steering: long-distance songs that can carry for hundreds or thousands of miles underwater, and may provide navigational cues or help migrating whales coordinate their movements.

“These whales are clearly using something more sophisticated to migrate than anything we’ve surmised,” said Calambokidis. “I’m really looking forward to seeing what this team does next.”

Prepared to see, correction, hear something really amazing? Check out the video below.

UPDATE: a recent study has finally proven that sockeye salmon indeed rely on magnetic field to guide itself back to the freshwater stream of their birth – a trait that’s believed to be also used by the humpbacked whale.

Mammals, half way extinct??

The previous 5 mass extinctions wiped out more than three quarters of the world’s animals, and if things continue to move in the same way, the same thing will happen in North America, according to a University of California, Berkeley, and Pennsylvania State University analysis.

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Numerous scientists have warned that the direction things are moving in is way more dangerous than believed by most authorities, and the combined effect of habitat destruction, global warming and environmental degrading will lead to a global catastrophe, yet fully accurate estimations were not done, due to the inability to compare species that live today with species that live in the past. However, the researchers from the above mentioned universities teamed up in order to overcome that obstacle, and using data from three catalogs of mammal diversity they were able to conclude the study.

“The optimistic part of the study is that we haven’t come all that far on extinction in the past 10,000 years,” said co-author Anthony Barnosky, UC Berkeley professor of integrative biology. “We have this pulse when humans had their first effect about 13,000 years ago, but diversity has remained pretty steady for about 10,000 years.”

In the last 100 or so years, however, “we are seeing a lot of geographic range reductions that are of a greater magnitude than we would expect, and we are seeing loss of subspecies and even a few species. So it looks like we are going into another one of these extinction events.”

But there are still things that can be done.

“I’m optimistic that, because we haven’t lost those species yet, if we redouble our conservation efforts we can stem the tide of extinctions and have those species around in the future,” he added.

Double our efforts to conserve species – do you really see that happening? I would be absolutely thrilled to see this happening, or even a less significant intensification, but it makes me sad to think how unlikely this is. Just this month massive distress calls were launched about koalas and siberian tigers. The thing is, we are responsible for this, and this is why it’s our responsibility to do something. Everytime mammals (and not only) had such problems, they would eventually get over it, but all that changed ~13.000 years ago, when humans entered the scene.

“The bottom line is, mammals in general were able to deal with these changes in the past. Only when humans arrive do the numbers fall off a cliff.”

That’s something to think about when you go to sleep at night, or when you’re complaining about bad weather.