by
This article is republished from Conversation Under Creative Commons Licence. Read the The original articlewhich was published on October 20, 2022.
It is the question that has baffled scientists for hundreds of years: Where do sea snakes come from on Earth?
Aristotle’s best guess It is generated automatically. It was the Danish biologist Johannes Schmidt Beautiful It almost certainly originated in the Sargasso Sea, near the Bermuda Triangle, to add to the mystery. His extensive biological surveys more than 100 years ago found plenty of baby sea snakes in this area, leading him to conclude that they must be hatching somewhere nearby.
But neither breeding eggs nor adult snakes have been seen anywhere nearby. The question remains unanswered… until now.
Last week, a team of researchers able to confirm Yes, people knew that a 1-meter European eel from their local river actually came from a subtropical sea as far as 10,000 kilometers away. This team had something that the greatest thinkers in history did not have: great technology.
Pop-up satellite archival tags are a relatively new type of tracking device that allows scientists to map the movements of marine organisms in a way that was not possible before. The tags record where the animals travel, how fast they move, and even how deep they dive. Then, the tags separate and float to the surface where they can transfer the data back into the scientists’ eager hands.
The migration of the European eel is impressive, but still shrouded in mystery. All eels on the mainland come from the same place where they lay eggs — yes, even eels in backyard ponds, which can Slide along the ground To the sea after a little rain. Sea snakes can even climb the walls of enormous dams! But how do they know where to go? How do they decide when?
Australia also has its own bright pythons. They generally keep to themselves, so much so that most of us don’t even know they’re there. But with all this rain and flood, there is a chance that you might stumble upon one of them soon.
So I thought it was a good time to share five things you might not know about snakes, including those in Australia.
1. We have our own fascinating immigration story in Australia
Although the European eel’s journey is not exactly long, the Australian shortfin eel does make a mass migration.
in Research published last yearResearchers from the Arthur Rylah Institute and the traditional Aboriginal company Gunditj Mirring used satellite tracking markers to map the path of 16 eels from Port Phillip Bay off Melbourne, to the coral sea outside the Great Barrier Reef. Some have covered nearly 3,000 kilometers in just five months.
It’s an arduous journey. Signs showed that some of the snakes dive to depths of about 1,000 meters below the surface of the ocean, taking advantage of currents and evading predators. However, not all of them were successful, as at least five of the tracked snakes were eaten by sharks or whales.
2. Eels are masters of the obstacle course
When you stop to think about it, you’ll find that there are more than a few barriers between inland freshwater and the ocean. Many of the swamps and wetlands that traditionally provided safe passage were filled in and replaced by farms, dams and towns.
However, the snakes find a way. One of the main features is their ability to breathe through their skin, which means that even shallow water or grass soaked in a pond is enough for them to move through.
according to popular legendSea serpents have been seen gliding through urban gutters, athletic ovals, or over campus fountains, tracing ancient paths back to the sea.
3. Snakes are expert transformers
Imagine if you had to go through puberty four or five times, with each physical change more dramatic than the last. Then you will have a good understanding of what it means to be a snake.
Migratory eels have to go from being saltwater fish to freshwater fish and back again, which means they’ve done it amazing life cycles. They start as a tiny larva in the ocean in the Sargasso or Coral Sea where they pupate, before turning into translucent “glass eels”.
Then, they transform into dark “snakes” at about one year of age as they make their way back to fresh water, where they eventually mature into the adult sea snakes that live in our rivers, lakes, and dams.
And when the time is right, they make their final transformation into lean, mean migratory machines – known as silver snakes.
Their eyes grow larger and their heads become pointed and streamlined. They also stop eating, as their stomach shrinks to make room for larger gonads (all the better for reproduction).
4. Sigmund Freud was also a fan of eels
Speaking of gonads, Sigmund Freud (yes, that Freud) spent the early years of his research career trying Understand the sexual anatomy of snakes.
Unfortunately for Freud and eels, the only way to tell if a eel is male or female is to dissect it to observe its internal reproductive organs.
Despite performing hundreds of autopsies, Freud rarely found male snakes. It turns out that this is because snakes don’t develop reproductive parts until later in life—usually not until they are at least ten years old.
5) Snakes can live very long lives
Yes, these tall fish have a long lifespan, with some snakes living over 50 years.
Single man in sweden claimed An eel in his backyard lived to be 155 years old, while another eel lived to be 85 in a Swedish aquarium.
The snakes spend the first few years of their lives returning from their spawning grounds to fresh water, while the last few years they make the journey back to the sea. They spawn only once – after which they die.
What is the importance of this type of research?
Still there Much we do not understand About snakes around the world. But satellite research, like the one published this week, takes us one step closer to putting all the pieces together.
And this has real implications for how we care for eel populations. European eel (Anguilla Anguilla) He is seriously endangeredas the species has seen declines of up to 95% in the past 50 years.
We really don’t know how well Australian pythons track. If we understand where animals breed and how they get there, that means we can find ways to help them, rather than hinder their journey, and protect places that matter.
The Conversation is grateful for the contribution of Australia’s No. 1 eel enthusiast, Dr Emily Finch, who Twitter topic I inspired this article
written by Kylie SwanesPostdoctoral Fellow, School of Ecosystem and Forest Sciences, Melbourne University.
