Tag Archives: organisms

Brainless Single-Celled Organisms Exhibit Pavlovian Learning Abilities

Posted on by
Reply

Stentor coeruleus – A remarkable single-celled organism

Melba Photo Agency / Alamy

Recent studies showcase that single-celled organisms, devoid of brains or neurons, can exhibit forms of advanced learning.

The most basic learning type is called habituation, where an organism gradually reduces its response to non-threatening stimuli like sounds or smells. This process is observed across various species, including animals and even plants. Habituation has also been demonstrated in some protists—complex eukaryotic cells that typically exist as unicellular organisms. For example, the trumpet-shaped blue spot stentor and slime mold poly skull.

Moving beyond habituation, associative learning evaluates how organisms connect multiple stimuli and predict events based on previous experiences. This concept was famously demonstrated by Ivan Pavlov, who showed that dogs could associate the sound of a bell with food, resulting in salivation at the mere sound.

Recently, Sam Gershman from Harvard University and his team utilized similar conditioning experiments to reveal that Stentor, a freshwater organism, is also capable of associative learning.

The stunning Stentor lives in freshwater habitats, using fine hair-like structures called cilia to navigate. Measuring up to 2 millimeters in length, it stands out among unicellular organisms. One end features a holdfast for surface attachment, while the opposite end has a trumpet-like feeding structure.


“When attached to a surface, Stentor primarily filters food from water. However, when disturbed, it retracts into a ball, making it temporarily unable to eat, which presents an ecological advantage,” Gershman notes.

To study Stentor’s learning capabilities, researchers conducted experiments by tapping the bottom of a Petri dish containing Stentor cultures. Most organisms initially contracted rapidly in response to loud taps, but this behavior diminished with repeated stimulation, indicating a form of habituation.

In subsequent experiments, the researchers introduced a weak tap followed by a strong tap. Typically, few microorganisms responded to the weak stimulus alone. However, the paired taps, executed every 45 seconds, gave Stentor sufficient time to re-extend, demonstrating associative learning over multiple trials.

After conducting over 10 trials, researchers noted an increased and then decreased probability of contraction following the weak tap, indicating a nuanced form of learning. “The observed pattern in the contraction rate signals a depth of cognitive ability previously underestimated in such simple organisms,” asserts Gershman.

The findings suggest that Stentor may be the first known protist capable of associative learning by linking weak and strong stimuli. “This raises compelling questions about the cognitive abilities of seemingly simple organisms compared to more complex multicellular entities,” adds Gershman.

Moreover, these revelations imply that associative learning could have ancient evolutionary roots, predating the emergence of complex nervous systems by millions of years. It echoes the way neurons in multicellular organisms learn through stimuli, drawing connections independent of synaptic changes, as described in previous research (here).

“The capacity of a single cell to perform complex tasks, once thought exclusive to organisms with brains, is quite remarkable,” concludes Shashank Shekhar of Emory University, who demonstrated Stentor’s ability to aggregate in short-lived groups for more efficient feeding.

“I suspect that other unicellular organisms may also possess similar associative learning capabilities,” he remarks. “Once such abilities arise, they may become prevalent across various organisms.”

While the mechanisms behind Stentor’s learning remain to be fully understood, Gershman posits that it may involve specific receptors allowing calcium influx, altering the internal voltage response to touch and thus influencing contraction behavior. Over time, repeated stimulation may modify these receptors, functioning as molecular switches to curtail contraction.

Topics:

  • Neuroscience /
  • Microbiology

Source: www.newscientist.com

Brain-free Learning: How Single-Celled Organisms Exhibit Pavlovian Conditioning

Posted on by
Reply
Stentor coeruleus, a unique single-celled organism

Stentor coeruleus: A single-celled organism with remarkable learning capabilities

Melba Photo Agency / Alamy

Fascinatingly, simple, single-celled organisms like Stentor coeruleus demonstrate advanced learning abilities, despite lacking brains or neurons.

The most basic form of learning, termed habituation, entails a gradual decline in response to recurrent, harmless stimuli—such as specific smells or sounds. This phenomenon is prevalent across all animal species and even plants, having also been observed in protists—complex eukaryotic cells that are principally unicellular. For example, both the trumpet-shaped blue spot stentor and slime mold Poly skull exhibit this behavior.

Moreover, a more complex aspect of learning involves associating different stimuli and events, allowing organisms to predict relationships. This form of associative learning became widely notable through Ivan Pavlov’s experiments where dogs learned to associate a bell’s sound with feeding, leading to salivation upon hearing the sound alone.

Recently, Sam Gershman from Harvard University and his team conducted similar experiments that indicated Stentor is capable of associative learning.

These remarkable organisms inhabit ponds and swim utilizing cilia, tiny hair-like structures lining their bodies. Growing up to 2 millimeters in length, Stentor stands out among single-celled entities, with a holdfast for anchoring and a trumpet-shaped feeding apparatus.

According to Gershman, “When they’re attached, they filter food. If disturbed, they rapidly contract into a ball shape, becoming immobile and unable to eat—this behavior is ecologically advantageous.” Using this response, they explored Stentor’s learning potential by tapping the bottom of a Petri dish containing numerous Stentor cultures. Initially, the creatures contracted quickly, but as the tapping continued—totaling 60 taps every 45 seconds—the contractions reduced, indicating habituation.

Subsequently, a weak tap was introduced one second before the stronger tap. This association is rare in microorganisms; the paired taps occurred every 45 seconds to align with Stentor’s unfolding time.

After conducting over 10 trials, researchers observed that the likelihood of a contraction after the weak tap initially surged before declining. “We noted a notable peak where the contraction rate rose and then fell—this isolation wouldn’t be visible through weak taps alone,” Gershman explained.

The findings reveal that Stentor is the first protist recognized for its associative learning ability, linking weak taps with louder ones. “This raises intriguing questions about whether seemingly simple organisms possess cognitive abilities typically reserved for more intricate multicellular organisms with nervous systems,” Gershman asserted.

This insight suggests that the capability for associative learning has ancient evolutionary roots, predating multicellular nervous systems by hundreds of millions of years. Some parallels may still be present in human neuron behavior, exhibiting learning independent of synaptic changes, illustrating diverse learning mechanisms.

It’s remarkable that a single-celled organism can perform complex tasks previously attributed solely to beings with brains and neurons. Shashank Shekhar at Emory University notes that Stentor can aggregate into temporary groups for more efficient feeding.

Gershman suspects other unicellular organisms might also possess associative learning abilities. “Once this trait arises, it likely emerges in various forms,” he claims.

If an organism is capable of learning, it must somehow store memories. While the exact mechanism in Stentor remains unclear, Gershman postulates it may involve calcium-receptive mechanisms altering internal voltages in response to stimuli, leading to contractions. These adaptations suggest possible molecular switches that inhibit contraction following repeated stimuli.

Topics:

  • Neuroscience /
  • Microbiology

Source: www.newscientist.com

Fossil Amber Unveils Ancient Ant Ecological Interactions with Other Organisms

Posted on by
Reply

Fossils preserved in amber are not only exquisite but also provide insights into ancient ecological interactions, including potential parasitism and symbiotic relationships between ants and mites. This revelation comes from a groundbreaking morphological study analyzing six amber specimens: Baltic, Dominican, and Burmese.

Fossils of an ant colony preserved in Baltic Sea amber from Lithuania. Image credit: José de la Fuente & Agustín Estrada-Peña, doi: 10.3389/fevo.2026.1724595.

“Inclusions in amber reveal potential interactions between various organisms that shaped prehistoric environments,” stated paleontologist Dr. Jose de la Fuente from the Game and Wildlife Research Institute.

“The identification and morphological analysis of fossil ants and other insects in amber offer a glimpse into life on Earth millions of years ago.”

In this pioneering study, de la Fuente and colleagues examined four pieces of Cretaceous amber (dating back 99 million years), one Eocene amber (approximately 56 to 34 million years ago), and one Oligocene amber (roughly 34 to 23 million years ago).

The specimens comprised ancient ants and other organisms, as well as a rare phenomenon known as syninclusion.

“The earliest ants, identified from the late Cretaceous period, were known as stem ants, which left no modern descendants. All existing ants evolved from crown ants,” the researchers emphasized.

“Both ant types are present in the six amber specimens we investigated, including the hell ant, which evolved from stem ants.”

The researchers utilized advanced microscopy to identify various species and document the distances between ants and other organisms in the specimens.

In three of the six amber pieces, ants were discovered in close proximity to mites.

The first specimen revealed crested ants, a wasp, and two ticks closely associated, suggesting they may have been traveling on the ants.

The second piece showcased stem ants alongside spiders, while the third contained hell ants, snails, millipedes, and numerous unidentified insects.

The fourth specimen featured a stem ant and a mite approximately 4 mm apart.

The fifth amber fragment included three distinct types of ants related to mites and termites, as well as poorly preserved mosquitoes and winged insects.

In the sixth sample, stem ants were found alongside wasps and spiders believed to be parasitic. It appeared the ants were consuming something, resting against another insect inclusion that might be a worm or larva, yet no interaction was evident, hinting it could be a coincidence.

“The closest co-inclusions of ants likely reflect behaviors and interactions between these organisms,” Dr. de la Fuente noted.

“The ant-mite interaction observed in the fourth specimen may indicate two potential scenarios.”

“First, a special symbiotic relationship where the tick hitches a ride on the ant to disperse to new habitats; second, parasitism occurring when the mites feed on the ant host during transport.”

While amber fragments featuring ants are scarce, those with multiple species are even rarer. Existing evidence suggests interactions between ants and mites may sometimes be mutually beneficial.

Future studies could clarify these interactions using micro-CT scans to explore attachment structures that may facilitate the mites’ travel on ants.

“Advanced imaging techniques are essential for enhancing the analysis of interactions among diverse organisms in fossil amber inclusions,” concluded Dr. de la Fuente.

For more details, read the research team’s paper published today in Frontiers in Ecology and Evolution.

_____

Jose de la Fuente and Agustín Estrada-Peña. 2026. Description of fossil amber containing ant co-inclusions. Front. Ecol. Evol 14; doi: 10.3389/fevo.2026.1724595.

Source: www.sci.news

2025 Discovery: Living Organisms Emit Ghostly Glow

Posted on by
Reply

Living Things Emit “Biophotons”

Microphone shot/Shutterstock

This year, scientists made a fascinating discovery: an eerie glow emitted by mice that vanished after death, evoking paranormal notions about the body’s aura. This finding has ignited significant interest in the scientific exploration of biophotons.

Biophotons are extremely faint particles of light created by cellular structures, particularly mitochondria, which are responsible for energy production. Researchers have been attempting to detect these weak signals, but the field has encountered skepticism. Separating biophotons from other light sources, such as infrared light, presents considerable challenges in demonstrating their authenticity.

<p>Due to experimental limitations, biophoton research has mainly concentrated on smaller, specific body parts. However, in May, <a href="https://scholar.google.com/citations?user=sUKbEwsAAAAJ&hl=en">Daniel Oblak</a> and his team at the University of Calgary, Canada, observed biophotons emitted from the entire bodies of four hairless mice. Interestingly, these biophotons dissipated shortly after the mice died.</p>
<p>The researchers also recorded biophotons emitted from the leaves of umbrella trees (<em>Heptapleurum arboricola</em>), reinforcing the evidence for their existence through comprehensive study.</p>
<p>Following the <em>New Scientist</em> report on the study, many media outlets contacted Oblak’s team for interviews. The phenomenon's similarity to a "spiritual aura," which some psychics claim reflects an individual's physical and mental health, may have contributed to the public's fascination. Oblak mentioned, "Someone from Argentina urged us to investigate the glow of hands during healing." </p><section>

</section>
<p>However, Oblak emphasizes that the science surrounding biophotons is legitimate. Numerous scientists have approached his team to collaborate on further studies. One proposal involves investigating biophoton production mechanisms in plants. Experts in genetically modified seeds suggest analyzing changes in biophoton emissions by disabling specific genes.</p>
<p>Insights into how biophotons correlate with seed germination could significantly benefit agriculture, according to Oblak. “You could assess seed samples to determine if the germination process happened without direct contact with the seeds.”</p>

<section class="ArticleTopics" data-component-name="article-topics">
    <p class="ArticleTopics__Heading">Topics:</p>
</section>

Source: www.newscientist.com

Snowball Earth’s harsh environmental conditions provided a competitive edge for the evolution of multicellular organisms

Posted on by
Reply

Fossil and molecular evidence suggests that complex multicellular organisms arose and proliferated during the Neoproterozoic Era (1-541 million years ago). An extreme glacial period during the Cryogenian Period (720-635 million years ago), an event commonly referred to as Snowball Earth, led to dramatic changes in Earth's climate and oceans. New research suggests that Snowball Earth was an environmental trigger for the proliferation of complex multicellularity across multiple groups of eukaryotic organisms.

Artist's impression of “Snowball Earth.” Image courtesy of NASA.

Solving the mystery of why multicellular organisms emerged could help pinpoint life on other planets and explain the enormous diversity and complexity seen on Earth today, from marine sponges to redwoods to human societies.

The prevailing thinking is that oxygen levels must reach a certain threshold for a single cell to form a multicellular colony.

However, the oxygen story does not fully explain why the multicellular ancestors of animals, plants and fungi emerged simultaneously, or why the transition to multicellularity took more than a billion years.

The new study shows how the specific physical conditions of Snowball Earth, particularly the viscosity of the oceans and the depletion of resources, may have led eukaryotes to become multicellular.

“It seems almost counterintuitive that these extremely harsh conditions – this frozen planet – could actually select for larger, more complex organisms, rather than causing species to become extinct or shrink in size,” said William Crockett, a doctoral student at MIT.

Using scaling theory, Crockett and his colleagues found that a hypothetical ancestor of early animals, reminiscent of swimming algae that fed on prey instead of photosynthesizing, would have grown in size and complexity under Snowball Earth pressures.

In contrast, single-celled organisms that move and feed by diffusion, such as bacteria, will grow small.

“The world changed after Snowball Earth because new life forms emerged on the planet,” said Professor Christopher Kemps of the Santa Fe Institute.

“One of the central questions of evolution is: How did we evolve from nothing on Earth to beings and societies like us? Was it all by chance?”

“We don't think it's luck. There are ways to predict these big changes.”

The study shows how, during the Snowball Earth era, the oceans froze, blocking sunlight and reducing photosynthesis, which resulted in nutrient depletion in the oceans.

Larger organisms that could process more water were more likely to eat enough to survive.

As the glaciers melt, these large creatures could expand even further.

“Our study provides hypotheses about ancestral features to look for in the fossil record,” Crockett said.

of study Published in Proceedings of the Royal Society B.

_____

William W. Crockett others2024. Snowball Earth's physical constraints drive the evolution of multicellularity. Proc. R. Soc. B 291 (2025): 20232767; doi: 10.1098/rspb.2023.2767

This article is a version of a press release provided by the Santa Fe Institute.

Source: www.sci.news

The genome of a new fern species from New Caledonia is the largest among all organisms

Posted on by
Reply

Tumecipteris oblancorata is a rare fern species known as the wolf lark, found in New Caledonia, a French overseas territory in the southwest Pacific Ocean. It has recently broken the world record with its genome size of 160.45 billion base pairs (Gbp), challenging current understanding and paving the way for further exploration of genome gigantism.

Tumecipteris oblancorata. Image courtesy of Pol Fernández.

Tomesypteris is a small and relatively understudied genus consisting of 15 species, mostly found in Oceania and some Pacific islands.

Scientists have previously estimated the genome sizes of two Tomesypteris species – Tumecipteris tannensis and Tomesypteris obliqua – with large genomes of 73.19 Gbp and 147.29 Gbp, respectively.

In 2023, Dr. Jaume Pellicer and his colleagues from the Royal Botanic Gardens, Kew, traveled to New Caledonia to analyze the genome size of Tumecipteris oblancorata.

The analysis revealed a record-breaking genome size of 160.45 Gbp for Tumecipteris oblancorata, also known as Tumecipteris truncata, surpassing the genome size of the Japanese flower plant species Paris Japonica (148.89 Gbp). For comparison, the human genome contains approximately 3.1 Gbp across 23 chromosomes.

Tomesypteris is a unique fern genus whose ancestors date back around 350 million years, characterized by primarily being epiphytes with a distribution limited to Oceania and a few Pacific islands.

Dr. Ilia Reich of the Royal Botanic Gardens, Kew, expressed surprise at the world record held by the inconspicuous Tumecipteris oblancorata, highlighting the diversity of plants at the DNA level and their importance in Earth’s biodiversity.

The team’s findings were published in the journal iScience.

Genome size diversity in eukaryotes: (A) Current distribution of genome sizes in the major lineages of plants, animals, and fungi. (B) Top 10 largest genome sizes recorded in eukaryotes. Image courtesy of Pol Fernández et al., doi: 10.1016/j.isci.2024.109889.

This remarkable discovery raises questions about the biological limits and complexities of plant genomes, inspiring further exploration into the mysteries of genome gigantism.

_____

Pol Fernandez othersThe 160 Gbp fork fern genome breaks eukaryotic size record. iSciencePublished online May 31, 2024, doi: 10.1016/j.isci.2024.109889

Source: www.sci.news