The vast oceans are home to some of the most intriguing and mysterious creatures. Among these are octopuses and squids, known as cephalopods, which have developed unique sensing capabilities to navigate their underwater worlds.
Octopuses explore the seafloor with their eight arms, using highly sensitive suckers in a “taste by touch” approach, while squids employ a starkly different tactic, patiently hiding until they ambush their prey in swift bursts.
A recent pair of research studies led by scientists from the University of California San Diego and Harvard University delves into the evolutionary adaptations of these sensing abilities, revealing connections to human brain receptors.
These groundbreaking studies, published in the journal Nature, were conducted by researchers from Ryan Hibbs’ newly established laboratory at UC San Diego (formerly based at the University of Texas Southwestern Medical Center) and Nicholas Bellono’s lab at Harvard.
The research teams adopted a comprehensive approach, examining cephalopods from atomic-level protein structures to the entire functional organisms. They focused on sensory receptors as a key site for evolutionary innovation, intersecting ecology, neural processing, and behavior.
The investigation of how octopuses and squids sense their marine environments led to the discovery of new sensory receptor families, and the experts determined how these receptors drive distinct behaviors in the environment.
They employed cryo-electron microscopy technology, which uses cryogenic temperatures to capture biological processes and structures in unique ways, demonstrating that adaptations can help propel new behaviors.
“Cephalopods are well known for their intricate sensory organs, elaborate nervous systems and sophisticated behaviors that are comparable to complex vertebrates, but with radically different organization,” said Hibbs, a professor in the Department of Neurobiology. Hibbs brings expertise on the structure of a family of proteins in humans that mediate communication between brain neurons and other areas such as between neurons and muscle cells. “Cephalopods provide striking examples of convergent and divergent evolution that can be leveraged to understand the molecular basis of novelty across levels of biological organization.”
In one of the Nature studies, the scientists described for the first time the structure of an octopus chemotactile receptor, which octopus arms use for taste-by-touch exploration. These chemotactile receptors are similar to human brain and muscle neurotransmitter receptors, but have evolved to help evaluate potential food sources in the marine environment.
“In octopus, we found that these chemotactile receptors physically contact surfaces to determine whether the animal should eat a potential food source or reject it,” said Hibbs. “Through its structure, we found that these receptors are activated by greasy molecules, including steroids similar to cholesterol. With evolutionary, biophysical and behavioral analyses, we showed how strikingly novel structural adaptations facilitate the receptor’s transition from an ancestral role in neurotransmission to a new function in contact-dependent chemosensation of greasy environmental chemicals.”
The second Nature study focused on squids and their distinct ambush strategy for capturing food. The researchers combined genetics, physiology, and behavioral experiments to discover a new class of ancient chemotactile receptors and determined one structure within the class.
They also conducted an evolutionary analysis to link adaptations in squid receptors to more elaborate expansions in octopus receptors. By placing chemotactile and ancestral neurotransmitter receptors on an evolutionary timeline, the researchers were able to describe how evolutionary adaptations drove the development of new behaviors.
“We discovered a new family of cell surface receptors that offer a rare lens into the evolution of sensation because they represent the most recent and only functionally tractable transition from neurotransmitter to environmental receptors across the entire animal kingdom,” said Hibbs. “Our structures of these unique cephalopod receptors lay a foundation for the mechanistic understanding of major functional transitions in deep evolutionary time and the origin of biological novelty.”
Hibbs says the pair of new studies offers an excellent example of how curiosity in interesting creatures can lead to insights important for all of biology, namely how proteins – life’s building blocks – adapt to mediate new functions and behaviors.
“These studies are a great example of what being a scientist is all about – wonder, exploration and understanding how things work,” he said.
The findings not only shed light on the fascinating underwater lives of cephalopods, but also reveal a deeper understanding of the complex web of evolutionary connections that tie together the living world, including our own brains.
Octopuses are fascinating marine creatures that belong to the class Cephalopoda, which also includes squids, cuttlefish, and nautiluses. They are widely known for their remarkable intelligence, problem-solving abilities, and exceptional camouflage skills. Here are some more interesting facts about octopuses:
These captivating creatures continue to be a subject of fascination for scientists and the public alike, as researchers uncover more about their unique biology, behaviors, and adaptations to life in the ocean.
Squids are intriguing marine animals belonging to the class Cephalopoda, which also includes octopuses, cuttlefish, and nautiluses. They are known for their streamlined bodies, impressive swimming abilities, and bioluminescence. Here are some more interesting facts about squids:
The fascinating biology, behaviors, and adaptations of squids continue to captivate scientists and the public alike, as researchers uncover more about their complex lives in the ocean’s depths.