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The Gap Year Blog

DARWIN DAY: Top 5 Living Fossils

13 Feb 2017 17:20 PM
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Safe to say (other than his groundbreaking studies into the conservation value of earthworms), Charles Darwin is most famous for his contributions to the theory of evolution, particularly natural selection. There are some creatures still alive today that have barely changed throughout natural history though. Here are 5 species that have stood the test of time, harking back to their evolutionary roots.

Coelacanth 

These rare carnivorous fish are perhaps the species most associated with the term "living fossil". They were thought to have gone extinct alongside the dinosaurs 65million years ago until a living specimen was discovered in 1938. 

Photo Credit: flickr | smerikal

Coelacanths swim at a depth of 700m and measure up to 6ft long. When compared to fossil records they have retained ancient features such as their thick scales and unique fins, which are considered to be an evolutionary step in the legs of the first terrestrial amphibians. 

There are only 2 species belonging to the order Coelacanthiformes; L. chalumnae, found in the West Indian Ocean off the coast of Africa and L. menadoensis, occurring around Indonesia's coast. Both species are estimated to number under 1000 individuals and because of their limited range, are considered critically endangered. They are also at risk from being caught as bycatch by deep-sea trawling, making the future of these ancient species uncertain.

Ginkgo Tree

Photo Credit: pixabay | WolfBlur

These primal looking trees belong to the monotypic order Ginkgoales, with all but one species extinct in the wild. Today Ginkgo biloba is only found along riverbanks in China but its origins can be traced back 270million years.

In their infancy there were many subspecies of gingko distributed worldwide, all adapting to their niche environments whilst retaining several advantageous traits. These traits dictated ginkgo morphology, longevity and distribution and were so successful they persisted over the course of 100 million years. However, these traits were also ironically their downfall as they were gradually outcompeted by the rise of rapidly adaptable angiosperms in their specialist habitats.

Photo Credit: Wikipedia | User:SNP

Despite the sudden shift in the evolution of plant-life, these ancient traits remain steadfast in the modern wild ginkgo, attaining a much-earned place on the list of living fossils.

Bristle Worms

Although exhibiting vast diversity across some 10,000 species, Bristle Worms or Polychaetes, all possess a common body-plan traceable to the early Cambrian era. Despite having to adapt to environmental changes and other factors, this basal physique has long been ecologically significant, making the majority of Bristle Worms living fossils.  


Photo Credit: flickr | Silke Baron

Their longevity has also made them incredibly resilient. Since the earliest record of Bristle Worms 505million years ago, there have been 5 mass extinction events and these critters survived every one. There's even a species alive today, the Pompeii Worm, that can withstand the boiling temperatures of the hydrothermal vents it lives on. 505million years is a long time to find your niche and if super heat-resistance isn't impressive enough, these worms get weirder. 

A species that would fit in more on Arrakis than here on Earth, Bobbit Worms reach up to 10ft in length and bury themselves on the seabed, lying in wait for other unsuspecting polychaetes.

The bristle worm Platynereis dumerilii has also proved vital for cancer development research as the simplicity of its cells, reminiscent of its ancestors', has allowed scientists to study a key step in the evolution of cell division.   

Frilled Shark

Photo Credit: WikiMedia | Citron

These sharks are regarded as the most primitive looking shark and exhibit basal traits of modern shark evolution dating back 95 million years. 

These sharks are unique for their slender, eel-like bodies and can grow to over 6ft in length. Unlike other sharks whose jaws are positioned on the underside, Frilled Sharks have front-facing jaws which allow them to swallow prey such as cephalopods and smaller sharks whole.

Their precise hunting strategy in the wild is unknown and theories include coiling their body and using their fins to propel them in a snake-like strike, however this may have arisen due to the shark's other serpentine attributes. Another suggested strategy is the combined use of their exposed lateral line hair cells, hypersensitive to motion and their ability to create sudden negative pressure changes, effectively sucking prey into their mouth. 

Tardigrades

These tiny micro animals, sometimes referred to as 'waterbears', are as big as a grain of sand and are estimated to be 600million years old, about twice as old as the first dinosaurs. There are over 1000 species of tardigrade all of which possess incredible survivability.

Photo Credit: Wikimedia | Schokraie E, Warnken U, Hotz-Wagenblatt A, Grohme MA, Hengherr S, et al. (2012) 

Despite naturally occurring in freshwater, or generally moist conditions living on leaves, moss and dirt, these little guys can survive almost anywhere on Earth and even beyond. Experiments have revealed them able to withstand temperatures exceeding 150 ˚C and below -270 ˚C. If that's not impressive enough, scientists have exposed them to radiation 1000 times the lethal dose for humans, submerged them in several types of acid and even exposed them to the vacuum of space, surviving for 10 days before returning  to Earth unharmed!

This resilience is achieved through a process called cryptobiosis; the ability to reduce, and even suspend, metabolic activity. The most common form of cryptobiosis performed by waterbears is anhydrobiosis at extremely low temperatures, contracting its body enough to lose up to 95% of its stored water, allowing for the creation of protective proteins and sugars. Once favourable conditions are restored, they rehydrate their bodies from surrounding moisture and walk away as if nothing happened.       

If you’re honouring Charles Darwin for Darwin Day, what better way to do it than with these guys. Displaying the sort of evolutionary development and resilience that would make one of the fathers of modern natural sciences proud.

By Thomas Phillips - Online Journalism Intern

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