Wildlife TV

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Tom and Jerry: Fatal attraction or something else?

How many of us grew up watching Tom the cat and Jerry the mouse constantly fighting and teasing each other to our own amusement? This show created in 1940 has been a source of entertainment for millions of children worldwide for decades. It shows us the reality of the animosity between cats and mice, but how real is it?
Do cats and mice really hate each other? Do they fight? Do naughty mice track down, tease and get cats in trouble?
The answer to all these questions might be slightly different than you think.

Domestic cats and urban mice are natural enemies the same way that lions and zebras are. One is the predator and one is the prey and while the former does whatever it takes to track down and hunt the other, the latter would do all it can to avoid that fate. They don’t exactly hate or fight each other for their own entertainment, they just do what they need to do to in order to survive.

Tom the cat chasing Jerry the mouse. From Warner Bros

Tom and Jerry   © Warner Bros

So why does Jerry keep on trying to chase and annoy Tom? Wouldn’t he just leave him alone and try to be sneaky and quiet as a mouse to the best of his abilities as that would be the difference between survival and being a snack?
Scientifically speaking there is one very good explanation to why Jerry does this (apart from the fact that they are clearly just cartoons and not realistic interpretations of cat-mouse interactions).

There’s a very well known parasite called Toxoplasma gondii that is the source of one of the most feared diseases for pregnant women, toxoplasmosis. While in humans it can cause life long damage if passed from pregnant mother to fetus, in mice the consequences are quite different.

Mice have evolved a healthy avoidance of predators, especially cats, for millions of years. They can detect signs of the presence of felines and alter their behaviour in order to avoid crossing its path. If it wasn’t for this trait passed from generation to generation we wouldn’t have mice nowadays.

But this is nothing special. All living beings strive for survival and that doesn’t exclude the parasitic protozoan, Toxoplasma gondii. Our friend gondii, even though it is able to live inside almost any warm blooded animal, has a thing for cats. They live their lives either inside a cat or doing whatever they can to convince another animal to get inside one. Over millions of years of evolution they have perfected their technique.

 

This is a conversation I imagined went between gondii pals:

  • “Hey Steve have you seen Carlos recently? Ever since he met that cat he’s doing well in his life. He can even reproduce sexually now!”
  • “No way Andre! I thought we could only reproduce asexuality. I must try this cat technique. How does this cat thing work?”
  • “It seems that we need to get ourselves inside a cat’s stomach and once we’re there it’s like heaven or something. That’s what Carlos told me though but he tends to overreact, you know that.”
  • “I must try this anyway. The problem is that we are inside a mouse now and they hate cats. How can we make this work?”
  • “Hum.. I know it! Let’s just make this mouse think that cats’ smell is the best smell in the world. Instead of avoiding it, it must get so excited about it that it will do its best to find the cat. Once it finds it we know what happens.. the cat will just eat our host, the mouse, and we end up in the cat’s stomach just as planned!”
  • “Dude, you’re a genius. Let’s do this!”

 

And this is pretty much what happens (with some creativity from my part). Toxoplasma gondii is capable of permanently changing the mouse host’s behaviour for its own benefit. This parasite increases the activity of the limbic regions of the mouse’s brain to react to a cat’s urine with sexual attraction instead of fear, forcing the mouse to seek the sexy company of the cat instead of hiding and escaping it.

The funny thing is that studies even show that this fatal attraction doesn’t happen with other species, only between cats and mice. It takes a Tom and Jerry for this scene to happen and all the other normal behaviours, senses and general health of the mouse remain unaltered. They just seem to suddenly feel extremely attracted to sexy cats..

That would explain why Jerry is so obsessed with Tom; always trying to get him in trouble, tease him and being naughty in general. He’s just a mouse in love..

 

Jerry the mouse kissing Tom the cat. From Warner Bros

Tom and Jerry   © Warner Bros

That’s all folks!

~Sofia.

 

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Is Immortality Real?

Immortality has been a subject that has fascinated human beings for the longest time. Many legends and mythologies discuss the possibility of supernatural beings and creatures with everlasting life and tell tales of heroes and adventurers seeking the fountain of youth or the elixir of life. In reality, humans are forced to be content with what little time we have on this Earth but left wondering; is immortality possible?

Ageing and eventually dying are natural processes that are a part of the rules of life, however, there are a few organisms that are capable of bending or even breaking these rules.

The animal kingdom is richly diverse and, as you might expect, different animals have vastly different lifespans and many have very brief lives, for example, the worm-like gastrotrich only has a few precious days of life in which to do all of its eating, fighting and mating.

 

Gastrotrich

A gastrotrich is a tiny worm-like aquatic creature that has one of the shortest lifespans in the natural world, only a few days. Photo Credits.

On the other end of the scale are animals that are extremely long-lived. An Aldabra giant tortoise (Aldabrachelys gigantea) that died in a zoo in India in 2006 was believed to have been born in around 1750 making him over 250 years old! The oldest mammals are believed to be bow-head whales (Balaena mysticetus); one individual caught in 2007 was found to have a 19th century harpoon embedded in its neck!

These remarkable cases might make our human lifespans seem measly by comparison, however, there are some organisms who live on a time-scale far beyond what we could ever experience. Some species of Antarctic glass sponges, hexactinellids, could live for as long as 15,000 years! Imagine a life longer than the whole history of human civilization.

 

Antarctic Hexactinellid Glass Sponges

Hexactinellids are glass sponges found in Antarctic waters. They are actually animals and may live for as long as 15,000 years! Photo Credits.

Longevity is impressive, but it is quite different from immortality. As unbelievable as it may seem, however, there are organisms that may be able to live forever.

Lobsters (family: Nephropidae) are animals that we are quite familiar with (mainly as an expensive meal), but they have some fascinating characteristics, most notably; they do not age. Lobsters grow continually throughout their lives but they do not get weaker or lose any function as they go, indeed, it has also been suggested that they become more and more fertile as they grow. A giant lobster (named George) was caught off the coast of Newfoundland in 2008 and was believed to have been approximately 140 years old! It is theorised that if left alone, lobsters might have the potential for immortality, growing indefinitely until they are killed by an external force such as a predator or disease. Lobsters achieve their longevity thanks to enzymes that repair damage to their DNA.

 

Lobster

Lobsters are a family of marine crustaceans. They grow continually throughout their lives but do not age. Photo Credits.

Turritopsis dohrnii is a species of tiny jellyfish that has a unique lifestyle that potentially qualifies it as immortal. These creatures live their lives up until a certain point, when conditions are right, when they will regress back to their infant form, a polyp. Almost like Benjamin Button, they age in reverse but they can repeat this cycle many times, potentially forever. Each time they revert to their immature stage, they are also capable of budding and producing whole new colonies of individuals.

So it seems as if some creatures have unlocked the secrets of immortality, however, immortality is quite different from invincibility. The process of ageing is also called senescence; this is where cells and organs deteriorate over time, whether as a result of being exposed to the stresses of everyday living, or the gradually increasing ineffectiveness of DNA replication. However, organisms that have beaten senescence are not guaranteed never ending life, there are my threats to their existence such as disease, fatal injury, predation etc. For example, the ‘Benjamin Button jellyfish’ rarely gets to even complete one of its life cycles in the wild because it is usually eaten by something first!

There are creatures that also attempt invincibility too: Tardigrades (sometimes called by the cuter names water bears or moss pigs) are microscopic animals that have a remarkable ability to survive extreme conditions; they earn the title of ‘extremophile‘. It seems to be very hard to kill a tardigrade; they can survive extreme sub-zero temperatures as easily as boiling water, they can survive the extreme pressures of the deep ocean as easily as the vacuum of space, they can survive without any food or water for years on end and can even tolerate extremely strong radiation. They can be found almost everywhere on Earth and have lived happily for tens of millions of years. Individual tardigrades can live for several decades depending on environmental conditions; not immortal but pretty close to indestructible!

 

A Tardigrade, or Water Bear

Tardigrades, or Water Bears, are microscopic animals that can survive almost any extreme condition. Photo Credits.

Humans have accomplished many great things, but sometimes we are reminded how fragile we are as animals. The natural world is full of amazing creatures with abilities that can humble us. Perhaps there are things we can learn from them and someday have a chance at immortality ourselves!

Thanks for reading!

Much love,

-Nick

 

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Callithrix kuhlii, you are NOT the father!

As a little guilty pleasure of mine, sometimes I enjoy watching tv shows where there’s a dispute of paternity involved. You know what kind of shows I’m talking about: those where the host proclaims “Trevor, you are NOT the father” and within a split second the audience is shouting, howling and/or clapping and the presumable “father” is doing something that resembles Dr. Zoiberg’s happy dance.


But how do paternity tests work?

The entire premise is quite simple; the man will provide a sample of his DNA by swabbing the inside of his cheek to collect epithelial cells and his genetic information will be compared to the one from the child. If they are around 50% similar to each other then the laboratory can attest that both parties are related.

When babies are formed they get 50% of the nucleic DNA from each parent to achieve the 100% they need to develop properly so if baby Trevor Jr. doesn’t have close to a 50% match of his DNA with Trevor Sr. then we can assume that they are not related.

However, what if I told you that there is a species in which the male that mated with the female and produced the baby was not the father? Even better, his brother (the baby’s uncle) is the father even though he never even met the mother!
This is so crazy but I can assure it’s true!

And if you are thinking that it must be some barely known species of fish or invertebrate you couldn’t be more wrong. It’s a small New World monkey, the Wied’s marmoset (Callithrix kuhlii) that lives in the tropical forests of Brazil.

A shy Wied's Marmoset (Callithrix kuhlii) hides behind a tree branch

A shy Wied’s Marmoset (Callithrix kuhlii) hides behind a tree branch.
Photo Credit


How is this possible?

The reason is simple; you see, in nature there are some very special individuals that have more than one DNA set. These individuals are called “chimeras”. The name came from the Greek mythology where the chimera was a creature that was made up of parts of several others animals.
While in Greek mythology chimeras looked quite crazy with part lion, part snake and part deer (or other variations), the real life chimeras existing on our planet are less easy to spot but equality exciting and the Wied’s marmoset is a great example of it.

These South American small monkeys are very well known for almost always giving birth to fraternal twins. As embryos in the womb of their mother, the twins’ placentas get fused together from an early stage in the development thus allowing stem cells the freedom to be transferred between both siblings. These stem cells are the ones that will eventually set up groups of cells and developing specific parts of the body.


So now follow me in this situation:

  • Marmoset A(ndre) and B(runo) are twin brothers and both chimera (as in, they both have sets of DNA from their twin brother).
  • Because of them being chimeras, when they were born, Andre ended up with his DNA in most parts of his body (such as the brain, muscles, liver, etc) but his testicles developed using Bruno’s DNA that got transferred through stem cells while they were in the womb.
  • This means that when Andre’s testicles produce sperm, the genetic information contained in this sperm will in fact be Bruno’s DNA.
  • Andre and Bruno were living in a Zoo and before they reached maturity, Bruno got transferred and Andre stayed behind.
  • Eventually they both reached sexual maturity and Andre got a female (C)arla pregnant.
  • When the babies were born the Zoo wanted to check out who the father was and tested the babies.
  • Because Andre’s testicles were producing sperm with Bruno’s DNA, their dad, Andre was technically and genetically not the dad.
  • This is how Bruno managed to father some babies even though he never even met Carla!


Nature can be so complex and crazy that sometimes I wonder if I’m reading a scientific article or watching a Mexican soap opera.

In case you want to know more about this very interesting topic feel free to read the (very detailed) article published by the Proceedings of the National Academy of Sciences.


Até à próxima!
~Sofia.


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