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.


2 Comments »

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.

Leave a comment »

Hematophagia: Vampires are Real!

Animals eat all sorts of things. The diversity of species in the animal kingdom is matched by the diversity of diets. In previous posts we’ve seen how some animals will eat bones (osteophagia), rocks or soil (geophagia), and even faeces (coprophagia). The next ‘phagia‘ we’re going to look at is hematophagia; feeding on blood.

When we think of feeding on blood, the animals that come to mind are blood sucking leeches and pesky mosquitoes but in reality, it is a widespread feeding behaviour utilised by a broad range of species. There are two categories of animal that feed on blood, obligatory and optional; some animals exclusively feed on blood (they are obliged) and some just supplement blood into their regular diet (it is an option). We call animals that feed on blood ‘sanguivores

So why does blood make a good meal? Blood carries vital chemicals around the bodies of many animals and as is loaded with nutrients, proteins, salts and fats; it is a nutritious and high energy food source. Most predators, such as big cats, will gain the nutrients found in blood because they eat all of an animal’s tissues, but hematophagy is used to describe when animals specialise in feeding on this valuable food resource.

Common Vampire Bat (Desmodus Rotundus)

There is nothing supernatural about vampire bats, they are simply an animal adapted to a specific diet. Photo Credits.

Blood is, of course, kept inside animals’ bodies, so in order to drink it, a certain amount of ‘surgery‘ is required. The process of accessing blood is called phlebotomy, it involves cutting into flesh and revealing veins, arteries or capillaries. The tools used by hematophagic animals are almost always their mouth-parts but there are many different anatomical approaches.

The first part of phlebotomy is cutting the flesh; mosquitoes (family: Culicidae), ticks (superfamily: Ixodoidea) and other blood sucking invertebrates have sharp mouth-parts that pierce the skin and dig down to find a source of blood, they then suck up the liquid or let the victim’s blood pressure force the blood into the diner’s mouth. Vampire bats (subfamily: Desmodontinae), found in Central and South America, have a slightly more crude and messier method, they simply use their teeth to slice open their victim’s skin and then lap up the pool of blood that comes out of the wound with their tongue. Interestingly, vampire bats will also use their teeth to trim fur away from the site where they intend to feed.

Anopheles stephensi

This mosquito (Anopheles stephensi) is feeding on human blood by piercing her mouth-parts through the host’s skin. She is digesting the rich nutrients and expelling the excess liquid. Photo Credits.

So vampires are real, but they aren’t supernatural beings, they are animals looking for a good meal, and there are many different species.

Vampire bats are a special group of bats that have become specialist blood drinkers, hence their name. They do not rely on echolocation like many other bats but instead they have specialised senses for finding sleeping mammals on which they can feed. They sniff out carbon dioxide (CO2) and chemicals found in sweat, and have special thermoreceptors on their noses which allow them to detect heat; this also allows them to find warm spots on an animal’s body where blood is closest to the surface.

Vampire Bats (Desmondus rotundus)

These common vampire bats (Desmodus rotundus) are being given a free meal of fresh blood, but in the wild they specialise in stealing blood from sleeping mammals. Photo Credits.

Mosquitoes are perhaps the most famous blood suckers, however, in reality they are not exclusively hematophagic. Not all species of mosquito feed on blood, and for those that do, it is only the females. This family of flies has evolved to feed on nectar and fruit juices but the females of some species have adapted their mouth parts and specialise in drinking blood from the bodies of mammals or birds. But why only the females? The reason for that is related to the nutritiousness of blood as a food source; they use the extra nutrients to help in egg production and development.

Sanguivorous animals are generally parasites; they take blood from their hosts and give nothing back in return (except maybe for a nasty disease). There is one animal that until very recently was thought to be beneficial to it’s hosts, but the relationship is not what it seems. Oxpeckers (genus: Buphagus) are Southern African birds that spend their time riding large grazing animals around, feeding (mostly) on ectoparasites such as ticks. A large animal like a giraffe (Giraffa camelopardalis) has a lot of surface area and a lot of blood and as such attracts a lot of parasites. Oxpeckers have found that riding along on a giraffe is a great way to find all the food they need. It used to be assumed that oxpeckers provided a wonderful service to the large mammals of Africa but recent studies have shown this might not be the case. Although oxpeckers are very fond of ticks (which are already full of blood), they also practice hematophagia and will regularly drink fresh blood from wounds on their host mammal’s body. Oxpeckers will even open up wounds and prevent them from healing so that they have a regular source of blood, this can be painful for the animal as well as putting them at risk of infections.

Yellow-billed Oxpecker (Buphagus africanus)

The yellow-billed oxpecker (Buphagus africanus) is one of the two species of African bird that feed on mammals’ parasites. Recent studies have shown they might cause more harm than good by keeping wounds open to drink blood. Photo Credits.

Hematophagy in practice can be a risky business; anyone who has been bitten by mosquito knows that their first response is usually of aggression and the same is true for other animals. Feeding on an animal’s blood requires physical contact and if caught, there is a possibility of being attacked or even killed. However, blood is such a valuable food resource that many animals are willing to take on these risks in order to obtain it, and many of them have a few tricks that help them get away with it.

Most blood drinking animals have special saliva that delivers a cocktail of chemicals into the bite site when they start to take blood. Their saliva can contain anaesthetics that prevent the host from feeling the bite and reacting to it, and also anticoagulants which prevent the blood from clotting so that it stays liquid and drinkable.

Animals have formed complex relationships with one another when it comes to feeding. When we think of animals feeding on other animals we tend to imagine large predators killing and devouring their prey, but in reality, some species have developed techniques for getting the sustenance they need without so much theatrics.

Much love,

-Nick

2 Comments »

Follow

Get every new post delivered to your Inbox.

Join 216 other followers