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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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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Mating for Life Part 3: Monogamy in Insects

We’ve seen in part 1 (birds) and part 2 (mammals) of this series that there is a lot of variation in monogamy in the animal kingdom. It is worth mentioning one more group of animals before we carry on.

  • Do insects mate for life?

In the invertebrate world, there is a countless variety of mating techniques, but even amidst this variety there are some examples of monogamy and mating for life. Termites (infraorder: Isoptera) are colonial animals where a single queen produces all the offspring that then grow up to service the collective. A termite queen constantly produces offspring, most of which become workers and soldiers that serve the colony, but each year, the queen will produce a generation of breeding individuals. These ‘breeders’, called alates, are males and females with wings that fly away from the home colony to found their own. Females breed and then head underground where they will stay for the rest of their lives producing young. In many species of termite, a queen will keep a single male at her side, a king, who will mate with her throughout her life and he will be her sole partner and father to the entire colony.

Termites surrounding a queen

A termite queen is a huge, egg producing machine (she is the blob in the middle of this picture); all termites in her colony are her offspring but sometimes she is accompanied by a king for her entire life. Photo Credits.

Many species of insect, such as mosquitoes (family: Culicidae) are monogamous because they do not live long enough to be anything else! They hatch from their eggs as larva and spend most of their lives in a larval form. Eventually, the larvae transform into their adult form and emerge, they will then seek to find a single mate with whom they will reproduce and then die. The adult stage of many insects’ lives are dedicated to the sole purpose of producing a single batch of eggs. You could argue whether this counts as monogamous or is just the force of circumstance.

Mosquito

Mosquitos are monogamous mostly because they die not long after they mate for the first time! Photo Credits.

The invertebrates make up the majority of animals on Earth and there is of course a lot of variation within their behaviours, however, monogamy and mating for life is very much uncommon.

In the next post, we will look more at the advantages of monogamy and faithfulness to a mating partner and some explanations as to why some animals have adopted this mating technique.

Much love,

-Nick

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