Image of Aulacopleura koninckii trilobite fossil. Attribution: Nigel Hughes/UCR
Recent studies reveal that the ability to adapt was crucial to the thriving of an archaic marine organism.
A specific trilobite species, an old sea inhabitant related to lobsters and spiders, has been investigated by researchers. They discovered the mechanisms this peculiar species used to shield itself from predators, as well as how it managed to endure changes in Earth’s oxygen levels.
Trilobites flourished in the seas for almost 300 million years, commencing around 520 million years ago in the Cambrian Period. During their existence on Earth, longer than the time dinosaurs reigned, they survived two major mass extinctions and became dominant in marine ecosystems.
These creatures had bodies consisting of three parts: a head, a thorax, or middle portion, and a stiff tail. With over 20,000 identified trilobite species, the majority have a specific count of segments in their midsections once mature. However, something unusual was found in Aulacopleura koninckii.
In mature Aulacopleura, scientists noted that there was a variance of 18 to 22 segments in the middle part, while earlier growth stages showed minimal change in shape and size.
“This species was peculiar. The inconsistency in Aulacopleura bodies was puzzling, as others of the same time maintained a constant number,” Nigel Hughes, a paleobiologist at UC Riverside and author of the study on this trilobite, commented.
He likened the variable segments in trilobites to humans being born with different numbers of vertebrae.
A simulation of Aulacopleura’s defensive movement. Credit: Nigel Hughes/UCR
Many questions arose concerning this abnormality, including its impact on the creatures’ defense mechanisms and why it developed this way. Answers to these questions are now available in a new paper published in the Proceedings of the Royal Society B: Biological Sciences.
Trilobites, similar to modern-day pillbugs or “rollie pollies,” would curl into a ball to protect themselves from predators like large, squid-like beings and fish. When rolled up, the tail would neatly fit under the head, safeguarding soft tissues by the hard exterior skeleton. 3D modeling revealed that in Aulacopleura, full protection while rolling was confined to the smaller, immature forms with fewer than 18 middle segments.
Hughes noted that as the segments grew, the body proportions did not allow for complete shielding. “So, why did this species continue adding segments, and how did it fend off the fierce predators?”
Virtual reconstructions suggest that Aulacopleura with many mid-segments would roll up like related species, letting their tails protrude beyond their heads to minimize exposure.
“Alternative defense strategies would have left critical organs vulnerable — highly improbable,” Hughes added.
The researchers then considered why this trilobite had varying mid-section segments and referred to their previous work. Hughes explained that under these segments were legs that acted as gills. “The more segments, the more surface area for breathing.”
The ability to grow additional breathing apparatus likely allowed these creatures to withstand reductions in local oxygen levels on the sea floor, which excluded other species, including predators of larger Aulacopleura. When parts of the sea floor became anoxic, predators were forced to move to oxygen-rich areas, while the larger Aulacopleura could remain, free from predators.
Understanding how this species adapted to biological and environmental pressures enhances our knowledge of the evolution of survival tactics. Trilobite development offers insights into the early evolution of modern arthropod groups, such as insects and arachnids.
Hughes expressed the importance of studying these animals to understand the evolution of development itself. “It’s not so much that the meek will inherit the Earth, but the flexible.”
Reference: “Developmental and functional controls on enrolment in an ancient, extinct arthropod” by Jorge Esteve and Nigel C. Hughes, 14 June 2023, Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2023.0871
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Frequently Asked Questions (FAQs) about fokus keyword: trilobite
What is the primary subject of the study on ancient marine species?
The primary subject of the study is the trilobite species Aulacopleura koninckii, an ancient sea-dwelling relative of spiders and lobsters. The research focuses on understanding the unique survival strategies and adaptability of this species, particularly the varying number of segments in its mid-section and how this influenced its defense mechanisms and respiration.
What unusual characteristic did scientists find in Aulacopleura koninckii?
Scientists found that while most mature trilobites have a specific number of segments in their mid-sections, Aulacopleura koninckii displayed variation, with anywhere between 18 and 22 mid-section segments in mature specimens.
How did Aulacopleura koninckii defend itself from predators?
Aulacopleura koninckii defended itself by curling up into a ball shape, similar to modern pillbugs or “rollie pollies.” 3D modeling showed that protection during this rolling was mainly for smaller, immature forms, while those with more segments would let their tails extend past their heads to minimize exposed areas.
Why did this trilobite species have variable numbers of mid-section segments?
The variability in mid-section segments is believed to be linked to the legs underneath these segments, which served as gills. The more segments, the more surface area for respiration, which likely gave these creatures the ability to endure fluctuations in seafloor oxygen levels.
What insights does the study of Aulacopleura koninckii provide about survival strategies and evolution?
Studying this species provides insights into how survival strategies evolve and adapt to environmental pressures. The findings may also hold clues to the early evolution of major modern arthropod groups, including insects and arachnids, reflecting the importance of flexibility in evolutionary development.
5 comments
I think it’s just remarkable how something as specific as the number of mid-segments can affect survival. How do these creatures evolve in such a way, the nature’s mystery continues.
Why is this so special, there are tons of other ancient creatures with unique features. What makes trilobites so exciting?? I dont get it.
I’m fascinated by this discovery! Trilobites are a bit of a passion for me and to know that they had this unique flexibility, it’s just, wow, mindblowing stuff.
so much to learn frm ancient creatures. the way they adapted, survived, its like a lesson for all of us. Isn’t it?
ancient species like trilobites holding keys to modern science, Who knew? I got to read more about this. thanks for sharing!