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Source : BBC News, April 26, 2017
http://www.bbc.com/earth/story/20170424-there-are-animals-that-can-survive-being-eaten
There are a few animals that can survive being eaten, and the skill might help them spread and colonise new regions
======================================================================
It was probably the trip of a lifetime. In 2012, biologists on an expedition to East Timor in southeast Asia spotted a brahminy blind snake wriggling out of somewhere quite unexpected: the rear end of a common Asian toad.
Mark O'Shea from the University of Wolverhampton in the UK and his colleagues witnessed the unusual event by chance after finding the pair under a rock. It is the first account of prey surviving digestion by a toad and of an animal as big as a blind snake emerging from a digestive tract alive.
"It's quite surprising that a vertebrate, which has lungs, was able to survive," says O'Shea.
Larvae and small marine invertebrates can pass through some predators unharmed. But larger prey items are likely to be chewed to death as soon as they enter an animal's jaws. Even if they somehow dodge this fate, travelling down the predator's throat in one piece can be a tight squeeze.
And there are bigger problems ahead. Most prey would not be able to survive exposure to the harsh gastric acids that break down tissue in a predator's stomach. Coping with the lack of available oxygen deep in the digestive system is another challenge.
For prey swallowed by a toad or a bird, however, chances of survival might be a little higher. These animals often push food to the back of their throat before swallowing it, which may boost the odds of safe entry into the digestive system.
This almost certainly helps explain how an incredibly toxic amphibian – the rough-skinned newt – can survive being swallowed by a frog. Once it enters the frog's stomach, the newt's toxins kill the frog before its digestive juices can really get to work. Then the newt simply has to crawl back up the dead frog's throat and out of its mouth.
Almost certainly the biggest problem the blind snake had to deal with was a prolonged lack of oxygen
But the brahminy blind snake did not kill its host – and it took a much longer path, through the gut, to exit the toad.
The snake may be better equipped for the journey than most species. With a long, slender body just a few millimetres wide, it effortlessly burrows through tiny holes and crevices in its environment. Passing through the narrow confines of a toad's digestive tract should not be too much of a challenge in principle.
O'Shea thinks the snake crawled through the toad's gut instead of simply being carried through by muscle contractions that move food along.
One factor that might have made that journey easier is the toad's earlier dining habits. It may not have eaten much in the hours before it swallowed the snake, meaning the path through its gut might have been clear. If so, the trip would have been a quicker one, reducing the snake's exposure to digestive acids.
But its skin was probably the biggest lifesaver. The closely-knit, overlapping scales that help blind snakes move on land would likely block gastric juices, preventing them from reaching delicate tissues and organs. The scales of other snakes come apart slightly when they move, so would not have the same protective effect.
Almost certainly the biggest problem the blind snake had to deal with was a prolonged lack of oxygen. As an underground dweller and due to its small size, it needs less air to survive than many animals. But still, there is a limit to how little it can tolerate. "Theoretically, the time it takes to get through the gut would determine if it lives or dies," says O'Shea.
Snails can endure the short digestive time without being fully exposed to the digestive juice
The researchers do not know how long it took the snake to journey through the toad's gut. But although they watched it wriggle out alive, it died about five hours later.
No post-mortem examination was carried out, but the researchers think the snake probably died from complications due to a lack of oxygen. "We couldn't think of anything else that would have killed it," says O'Shea.
Snails may be better gastric travellers than blind snakes, since they can survive on less oxygen.
In an experiment published in 2011, Shinichiro Wada from Tohoku University in Japan and colleagues fed tiny land snails, Tornatellides boeningi, to Japanese white-eye birds to see whether they could pass through their digestive system intact. About 15% survived the journey, which took between 20 and 120 minutes, proving for the first time that land snails can survive digestion. "Snails can endure the short digestive time without being fully exposed to the digestive juice," says Wada.
The snails' resistance is likely due to their shell, which provides them with natural armour. But Wada and his colleagues found that size was also key to survival. The shells of the species they examined, roughly 2.5mm wide, were recovered from bird faeces intact whereas those of larger species were usually broken into pieces. They think the snails may also produce mucus as additional protection from the acidic environment, but that idea still needs to be tested.
(To read more click on the link provided at the top of this post)
This section mostly contains political news though there is a section for political discussion.
I am using this section to post interesting news items.
Source : BBC News, April 26, 2017
http://www.bbc.com/earth/story/20170424-there-are-animals-that-can-survive-being-eaten
There are a few animals that can survive being eaten, and the skill might help them spread and colonise new regions
======================================================================
It was probably the trip of a lifetime. In 2012, biologists on an expedition to East Timor in southeast Asia spotted a brahminy blind snake wriggling out of somewhere quite unexpected: the rear end of a common Asian toad.
Mark O'Shea from the University of Wolverhampton in the UK and his colleagues witnessed the unusual event by chance after finding the pair under a rock. It is the first account of prey surviving digestion by a toad and of an animal as big as a blind snake emerging from a digestive tract alive.
"It's quite surprising that a vertebrate, which has lungs, was able to survive," says O'Shea.
Larvae and small marine invertebrates can pass through some predators unharmed. But larger prey items are likely to be chewed to death as soon as they enter an animal's jaws. Even if they somehow dodge this fate, travelling down the predator's throat in one piece can be a tight squeeze.
And there are bigger problems ahead. Most prey would not be able to survive exposure to the harsh gastric acids that break down tissue in a predator's stomach. Coping with the lack of available oxygen deep in the digestive system is another challenge.
For prey swallowed by a toad or a bird, however, chances of survival might be a little higher. These animals often push food to the back of their throat before swallowing it, which may boost the odds of safe entry into the digestive system.
This almost certainly helps explain how an incredibly toxic amphibian – the rough-skinned newt – can survive being swallowed by a frog. Once it enters the frog's stomach, the newt's toxins kill the frog before its digestive juices can really get to work. Then the newt simply has to crawl back up the dead frog's throat and out of its mouth.
Almost certainly the biggest problem the blind snake had to deal with was a prolonged lack of oxygen
But the brahminy blind snake did not kill its host – and it took a much longer path, through the gut, to exit the toad.
The snake may be better equipped for the journey than most species. With a long, slender body just a few millimetres wide, it effortlessly burrows through tiny holes and crevices in its environment. Passing through the narrow confines of a toad's digestive tract should not be too much of a challenge in principle.
O'Shea thinks the snake crawled through the toad's gut instead of simply being carried through by muscle contractions that move food along.
One factor that might have made that journey easier is the toad's earlier dining habits. It may not have eaten much in the hours before it swallowed the snake, meaning the path through its gut might have been clear. If so, the trip would have been a quicker one, reducing the snake's exposure to digestive acids.
But its skin was probably the biggest lifesaver. The closely-knit, overlapping scales that help blind snakes move on land would likely block gastric juices, preventing them from reaching delicate tissues and organs. The scales of other snakes come apart slightly when they move, so would not have the same protective effect.
Almost certainly the biggest problem the blind snake had to deal with was a prolonged lack of oxygen. As an underground dweller and due to its small size, it needs less air to survive than many animals. But still, there is a limit to how little it can tolerate. "Theoretically, the time it takes to get through the gut would determine if it lives or dies," says O'Shea.
Snails can endure the short digestive time without being fully exposed to the digestive juice
The researchers do not know how long it took the snake to journey through the toad's gut. But although they watched it wriggle out alive, it died about five hours later.
No post-mortem examination was carried out, but the researchers think the snake probably died from complications due to a lack of oxygen. "We couldn't think of anything else that would have killed it," says O'Shea.
Snails may be better gastric travellers than blind snakes, since they can survive on less oxygen.
In an experiment published in 2011, Shinichiro Wada from Tohoku University in Japan and colleagues fed tiny land snails, Tornatellides boeningi, to Japanese white-eye birds to see whether they could pass through their digestive system intact. About 15% survived the journey, which took between 20 and 120 minutes, proving for the first time that land snails can survive digestion. "Snails can endure the short digestive time without being fully exposed to the digestive juice," says Wada.
The snails' resistance is likely due to their shell, which provides them with natural armour. But Wada and his colleagues found that size was also key to survival. The shells of the species they examined, roughly 2.5mm wide, were recovered from bird faeces intact whereas those of larger species were usually broken into pieces. They think the snails may also produce mucus as additional protection from the acidic environment, but that idea still needs to be tested.
(To read more click on the link provided at the top of this post)
