World's oldest heart found in prehistoric fish

Jan 27, 2020
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By Pallab Ghosh
Science correspondent

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Artist's impression of the Gogo fish

Researchers have discovered a 380-million-year-old heart preserved inside a fossilised prehistoric fish.
They say the specimen captures a key moment in the evolution of the blood-pumping organ found in all back-boned animals, including humans.

The heart belonged to a fish known as the Gogo, which is now extinct.

The "jaw-dropping" discovery, published in the journal Science, was made in Western Australia.

The lead scientist, Prof Kate Trinajstic from Curtin University in Perth told BBC News about the moment she and her colleagues realised that they had made the biggest discovery of their lives.

"We were crowded around the computer and recognised that we had a heart and pretty much couldn't believe it! It was incredibly exciting," she said.

gogo fish heart.jpeg
The fish are perfectly preserved in boulders found in the Kimberley region of Western Australia.

Usually, it is bones rather than soft tissues that are turned into fossils - but at this location in Kimberley, known as the Gogo rock formation - minerals have preserved many of the fish's internal organs, including the liver, stomach, intestine and heart.

"This is a crucial moment in our own evolution," said Prof Trinajstic.

"It shows the body plan that we have evolved very early on, and we see this for the very first time in these fossils."
Her collaborator, Prof John Long from Flinders University in Adelaide, described the find as "a mind-boggling, jaw-dropping discovery".

"We have never known anything about the soft organs of animals this old, until now," he said.

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The Gogo fish's heart had two chambers, one above the other, which went on to evolve into the human heart

The Gogo fish is the first of a class of prehistoric fish called placoderms. These were the first fish to have jaws and teeth. Before them, fishes were no bigger than 30cm, but placoderms could grow up to 29.5ft (9m) in length.

Placoderms were the planet's dominant life form for 60 million years, existing more than 100 million years before the first dinosaurs walked the Earth.

Scans of the Gogo fish fossil showed that its heart was more complex than expected for these primitive fish. It had two chambers one on top of each other, similar in structure to the human heart.

The researchers suggest this made the animal's heart more efficient and was the critical step that transformed it from a slow-moving fish to a fast-moving predator.

The researchers scanned inside the boulders to discover a liver, stomach, intestines and a heart, shown in red

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The researchers scanned inside the boulders to discover a liver, stomach, intestines and a heart, shown in red

"This was the way they could up the ante and become a voracious predator," said Prof Long.

The other important observation was that the heart was much more forward in the body than those of more primitive fish.

This position is thought to have been associated with the development of the Gogo fish's neck and made space for the development of lungs further down the evolutionary line.


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A fossil of the head of a Gogo fish with large eye sockets


Dr Zerina Johanson of the Natural History Museum, London, who is a world leader in placoderms, and is independent of Prof Trinajstic's team, described the research as an "extremely important discovery" that helps to explain why the human body is the way it is today.

"A lot of the things you see we still have in our own bodies; jaws and teeth, for example. We have the first appearance of the front fins and the fins at the back, which eventually evolved into our arms and legs.

"There are many things going on in these placoderms that we see evolving to ourselves today such as the neck, the shape and arrangement of the heart and its position in the body."

The discovery fills in an important step in the evolution of life on Earth, according to Dr Martin Brazeau, a placoderm expert at Imperial College London, who is also independent of the Australian research team.

"It's really exciting to see this result," he told BBC News.

"The fishes that my colleagues and I are studying are part of our evolution. This is part of the evolution of humans and other animals that live on land and the fishes that live in the sea today."

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See: https://www.bbc.com/news/science-environment-62912225?utm_source=join1440&utm_medium=email

An amazing discovery which shows what can lie inside a boulder. Placoderms existed from the Silurian to the end of the Devonian period, about 416 million to 359 million years ago. But only two species persisted into the succeeding Carboniferous Period. During the Devonian they were a dominant group, occurring in all continents, except South America, in a variety of marine and freshwater sediments. In early evolutionary history, there were gnathostomes (jawed fishes) and agnathans (jawless fishes). Two early groups of gnathostomes were the acanthodians and placoderms, which arose in the late Silurian period and are now extinct. The construction of the two chambered hearts in the placoderms allowed them to become the apex predator due to the superior oxygenation their tissues received. And it is interesting to compare the ancient hearts with ours.
Hartmann352
 
Jan 27, 2020
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Fish are typically described as cold blooded creatures which means they get their heat from the environment they literally have cold blood, however there is one fish that bucks this trend The Opah. The Opah is also known as the moon fish, the sunfish, the king fish, the red fin ocean pan, the Jerusalem Haziq and by his Latin genus name lampreys (that’s a lot of names).

It was discovered in 2015 by Wagner. In the peer-reviewed journal Science Nicholas Wagner and his team of fellow research colleagues found that the upper species lampreys Curtis is able to generate heat as it swims from its muscles which warms the heart and the brain organs. This ultimately provides an evolutionary adapted advantage for the fish as it can out-compete traditional cold blooded species.

The warmer temperature allows for faster muscle contraction and so fast a movement to acquire food and to avoid predators additionally.

The increased temperature improves the eye resolution helping to aid the fish’s sight neurological brain transmissions are also sped up helping to improve responsiveness which is great in their deepwater habitats where you never quite know what may be lurking in the darkness. So it’s a true warm blooded animal like mammals or Birds, not quite the warm-blooded system that we have provides us with something known as homeo but me now home your thermy allows our bodies to maintain a stable temperature internally regardless of external environmental heat factors the OPA fish on the other hand have to keep moving around to stay warm. Well they do have an insulating layer of fat to help keep in some of the heat ultimately. They will reach a colder temperature if their movement is restricted and they are more susceptible to external temperature influences.

See: https://fishsubsidy.org/are-fish-warm-blooded-or-cold-blooded/

Most reptiles, amphibians, fish, and insects are unable to maintain their core body temperatures from within. They are, therefore, dependent on the temperature from their surroundings. Such organisms are therefore known as ectotherms (ecto meaning outside + therm meaning heat). Their core temperature also varies significantly, which means that they are poikilotherms (poikilo, meaning varied + therm meaning heat). As a result of their nature, such animals do not require to generate as much heat as warmblooded animals. These animals tend to have a lower resting metabolic rate, which is also known as bradymetabolism (Brady meaning slow + metabol meaning to change). In general, reptiles, fish, amphibians, and insects that are ectotherms and poikilotherms and have a bradymetabolism are known as cool-blooded animals.
Hartmann352
 

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