Wildlife TV

Learn interesting and funny plant and animal facts with videos and photos

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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Clawed Frogs: Nature’s Pregnancy Test

Mating and breeding are fundamental aspects of surviving as a species and although many animals have breeding seasons, humans as a species, do not. This means that women don’t have specific times during the year in which they are more fertile and willing to engage in mating in order to get pregnant. Instead, we go through monthly fertile cycles between the first menstruation (menarche) and menopause. This is good on one hand because it is not necessary to wait for a specific month or months of the year in order to get pregnant but also bad because, as it can occur at any given time, women might fail to notice they are pregnant and not take basic pre-natal care to ensure the survival and best development of the baby.

 

Old school pregnancy tests

For many reasons it quickly became important to find out if a woman was pregnant or not as soon as possible. Was the queen finally going to provide an heir? Was the future virgin bride not so virgin after all? Was the husband that had just come back from the sea really the father? Being able to tell, with a certain accuracy, if a woman was pregnant or not would solve many problems but we still have no idea how our (very ancient) ancestors were doing it (if they were at all) since no information was ever found. We are aware however that the first known pregnancy test started to be used in the ancient Egyptian and Greek cultures with the use of urine and grains. They would introduce, on one side, urine of the lady that wanted to find out if she was pregnant, and on the other side (as the control subject) the urine of a priest, on bags of barley and wheat. Both bags would be observed for how long germination would occur. If a lady was with child her grains would sprout a lot faster than the priest (we could easily infer he would not be pregnant).

Throughout history many other “urine analysis” techniques were used to find out if women were pregnant, some of them more scientific than others; but it wasn’t until the last century that animals started to be used in the procedure.

With the discovery that the hCG (human chorionic gonadotropin) hormone was produced by the placenta during the first trimester of pregnancy, scientists were able to design a better and more reliable way to test for pregnancy.

This discovery, in the 1930’s, boosted the development of pregnancy test worldwide with very big implications. For the first time in known history, scientists were using live animals such as mice and even rabbits for their testing. Infantile females (non-sexually mature) were injected with the urine of the woman to be tested and later on killed and dissected in order to look for the presence of ovulation in the animal. The ovulation would have been triggered by the hCG presence in the injected urine of pregnant women and would pose as a positive result.

This method, however, meant that for every tested woman we would end up with a dead mouse or rabbit. Luckily for humanity shortly after, still in the 1930’s, a gentleman named Lancelot Hogben found out that he could use a specific genus of frogs, the Xenopus, to get the same results but without having to kill the animal.

 

Xenopus: 1930’s-1950’s pregnancy test

Clawed frogs (Xenopus) were subjected to the same method; the urine of the woman was injected in its dorsal lymph sac and if the frog produced eggs in the first 12 to 24 hours the woman was with child. The big difference between mice and rabbits and these frog species is that amphibians, unlike mammals, have external fertilization so the new eggs could be easily observed without having to kill and dissect the animal.

By the 1940’s, this test, named the “Hogben Test” in honour of its discoverer, was already widely used in hospitals.

Many facts helped this method achieve worldwide recognition:

  • It was extremely accurate
  • It was very easy to perform
  • Results were achieved in 12-24 hours
  • The frogs were easily bred
  • The frogs were conveniently kept in aquariums
  • Amphibians in general have large eggs which can be easily examined and manipulated
  • Eggs are released outside the animal (they use external fertilization)
  • Clawed frogs reacted to the hCG hormone released by pregnant women
  • Since the frogs didn’t have to be killed and dissected in order to have their eggs examined, they could be used multiple times
African Clawed Frog (Xenopus laevis)

African Clawed Frog (Xenopus laevis)
Photo Credit

 

Pregnancy tests post-Xenopus

Even though there were many advantages to using this African species in laboratories all over the world, there were a few cons that ultimately made the test obsolete.

  • The clawed frogs (Xenopus) had to be imported from Africa in large numbers
  • Live animals need to be housed, fed and taken care of
  • One disease outbreak in a lab with frogs would be enough to close it down

 

Eventually science evolved enough that by the 1960’s the Hogben test became obsolete and today we can buy a small, cheap and easy to use pregnancy test that will give a result within minutes and without going through several technicians, scientists and doctors. The same result can be achieved in private and in minutes.

Unfortunately, all the Xenopus testing for decades came with a price. In 2006 researchers found out that this genus might have been the carriers of the (in)famous chytrid fungus, a deadly amphibian fungus that caused the mass extinction and population decline of almost 200 amphibian species all around the world. African clawed frogs are known to be one of the only species of amphibians in the world to be not only immune but also a carrier of this deadly fungus and several decades ago we shipped them all over the world..

There is no treatment for this fungus and the only way to control this mass extinction is through quarantine.A staggering 30% of known amphibian species are currently threatened with extinction  and about 500 amphibian species are so threatened at the moment that no human effort will be fast enough in order to stop its extinction. Projects like the Amphibian Ark are doing their best to help the remaining species we have surviving these dark times. If you can, visit their “How can I help?” page. There are many things all of us can do to help out, either by donating time, money or skills.

Small gestures can make a huge impact on these small creatures.

 

Até à próxima.

~Sofia.

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Mating for Life Part 4: Why are Animals Monogamous?

  • Why are animals monogamous?

As we’ve seen in previous posts (about birds, mammals and insects), monogamy is common in some parts of the animal kingdom and rare in others, but the way in which it is practised varies a great deal. But what are the advantages of being faithful to a mating partner? Generally speaking, it makes sense for animals to be promiscuous; mating with a lot of partners increases the chance of producing a large number of offspring as well as increasing the chance of having the opportunity to mate with the most desirable partner. However, monogamy does have some advantages, as demonstrated by many of the species we have already discussed.

Warthog Family

Warthogs (Phacochoerus africanus) are promiscuous animals; the males wander around large areas, mating with any females they come across. They sacrifice selectivity for increased chances of producing young every breeding season. Photo Credits.

Monogamy does have its advantages: Many animals, such as Azara’s night monkey males (Aotus azarae) invest a huge amount of time and energy into raising their young and so they are motivated to minimise the risk of accidentally raising another male’s offspring; they do this by having a system of mating for life and staying faithful to their partners, ensuring that their chosen female will birth only his offspring. Some animals practice ‘mate guarding‘ in order to secure reproductive success; once a male has mated with a female, he stands guard over her to ensure that no other males will also mate with her. This may not entirely qualify as monogamy, however, it may explain why partners stay together for at least as long the gestation period (until the offspring is born).

Many animals spend a lot of time and energy acquiring mates; performing elaborate displays and courtship rituals. This behaviour ensures that animals select the best mates possible (strongest, fastest, most agile etc.), it makes sense for animals to stick with their partner once they have been selected so that the process does not have to be repeated; they have a reliable partner who can provide offspring without having to waste time and energy each mating season. This is best exemplified by albatrosses (family: Diomedeidae) who invest the first 10 – 15 years of their life practicing and then attempting to secure mates; once they get one, they stick with them for life.

Black Browed Albatross (Thalassarche melanophrys)

Albatrosses, such as these black-browed albatross (Thalassarche melanophrys), mate for life, eliminating the need to perform mating rituals every breeding season. Photo Credits.

One significant advantage of mating for life, or at least being monogamous for a significant period of time is that young animals can have both parents around in their early life to help raise them. This system of rearing young is efficient as parents can take turns finding food while the other stays behind to protect the infant(s) and is best demonstrated by the emperor penguin (Aptenodytes forsteri) where parents take turns doing a 200km round trip to get food from the sea and return to the inland colony in Antarctica.

Emperor Penguin Family

Emperor penguins (Aptenodytes forsteri) are serially monogamous meaning they form very close social bonds with their partners, but pick new ones each breeding season. Photo Credits.

There have been many studies that have attempted to demonstrate and explain the origins of monogamy in animals. It has been suggested that infanticide (the killing of youngsters) caused the development of monogamy. In some species, such as lions (Panthera leo), when a male takes control over a group of females from another male, he will kill all of his predecessor’s cubs so that the females will become sexually receptive once again. Monogamy counteracts this by evolving a system where males will stay with their females long-term in order to ensure that their offspring grow up to independence successfully.

African Lions (Panthera leo)

Male lions (Panthera leo) practice infanticide; when taking over a new pride (group) they will kill the offspring of their predecessor to make the females receptive to mating again. Photo Credits.

There is also evidence that hormones can contribute to monogamy. A chemical called oxytocin is found in mammals (including humans (Homo sapiens)) and seems to be released into the body during moments such as child birth, copulation and suckling. Oxytocin might be released in animals’ bodies to promote proximity and bonding between individuals. In humans, it’s the chemical that makes you feel good when thinking about people you love.

As always, the animal kingdom is full of complexity and fascinating behaviour. Although most animals do not show faithful monogamy to a partner, the ones that do have some very good reasons to do so. I hope you enjoyed this series and learned something along the way!

Much love,

-Nick

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