But the changes could be reversible.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.

What does it mean to be alive?

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.

The oceans are home to many of Earth's longest living creatures.

Glass sponges can survive for more than 10,000 years, and an individual quahog clam can thrive for more than 500.

A few jellyfish, jellies, and hydra are so good at regenerating themselves that they can theoretically live forever.

But the humble sea cucumber has a truly unique longevity trick.

Scientists in Canada have now discovered a sea cucumber species with tissue that may live 'indefinitely'.

When scientists amputated bits of a scarlet sea cucumber (Psolus fabricii), the tissues refused to die.

For three years and counting, the isolated tube feet and tentacles have sat all on their own in a tank of natural running seawater, without decaying away.

Not only are they not dead, but these tissues are biologically active and changing.

Many of their immune, metabolic, and cellular processes are still intact.

That's never been seen before – not from the tissue of any known animal on Earth.

"We haven't grown a new, complete sea cucumber yet, but we are seeing pretty stunning growth and diversification of cells literally years after this tissue was removed," explains marine biogeochemist Rachel Sipler from the Bigelow Laboratory for Ocean Science, a nonprofit research institute in the US.

"It's like a lizard that loses its tail. We know some lizards can grow new tails; we're talking about whether the tail can grow a new lizard."

Like many lizards on land, the sea cucumber species, P. fabricii, is a bit of a klutz in the ocean. It regularly loses or injures its tube feet and tentacles, which means it has a potentially great capacity for regeneration.

To test that idea in the lab, Sipler and her colleagues at Memorial University of Newfoundland watched and waited to see what happened to excised bits of this wild-looking sea cucumber.

Soon enough, the tissue samples began showing signs of wound repair. Their immune cells appeared to spring into action, and any dead cells were removed.

Repair was then followed by regeneration. Over time, the tissues began to absorb dissolved nutrients from the seawater, growing and restructuring themselves.

Years on, the isolated tentacles can still respond to tactile stimuli, indicating the preservation of a neural network.

This is the first known case of a tissue 'explant' surviving and growing long-term in a natural setting, write Sipler and her colleagues.

"Our findings," they add, "challenge conventional perceptions of tissue immortality."

They also raise the question: What does it mean for tissue to be alive?

For centuries now, scientists have tried to keep the cells and tissues of living animals functional, even when they are removed from the rest of the body.

While researchers have managed to engineer immortal cell lines from animal and human stem cells, these self-proliferating units must be kept in highly controlled environments, where they are carefully guarded against pathogens.

Keeping a whole bunch of cells alive within a section of tissue is much harder to manage.

Animal tissue is a flexible yet delicate structure; it requires a complex scaffold of communicating cells and a robust nutrient delivery system to keep everything plump.

Even when animal tissue is kept in a special solution to extend its longevity, it typically survives about 9 weeks in the laboratory.

But a bit of P. fabricii could live "indefinitely" in natural seawater, researchers speculate. In fact, it seems to thrive in the natural 'dirtiness'.

"Natural seawater is just about the most microbially diverse, least clean approach we could take experimentally," says Sipler.

"Yet, that rich environment full of bacteria and all this organic matter was actually feeding them and allowing this tissue to heal and grow."

The only other tissue culture that scientists have described as 'indefinite' was taken from a chicken embryo, and it did not show the same capacity for healing or survival as the scarlet sea cucumber.

In fact, P. fabricii may be unique even among sea cucumbers.

Sipler and her colleagues tested several other sea cucumbers, but none of their tissue explants survived more than 3.5 months.

"Here is this species that has this groundbreaking ability, and we had no idea," says Sipler.

"It's a reminder how much is yet to be discovered in the marine environment."

Related: Mammals May Have a Hidden Limb Regeneration Ability We Never Knew About

Andrea Bodnar, science director at the Gloucester Marine Genomics Institute, was not involved in the study, but she agrees with the paper's conclusions.

"The fact that tissue explants from a sea cucumber can heal, reorganize, and survive independently for years in natural seawater suggests an entirely new model for biological resilience and tissue regeneration," she says.

The study is published in Science Advances.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.

The key to heart health isn't cutting down on pasta or potatoes, new evidence suggests; it's not even a low-fat diet.

The research suggests the focus of healthy eating shouldn't necessarily be on what's being excluded from your diet (for example, reduced carbs or lowered calories).

Instead, the emphasis should be on what you're actually putting into your body, and the quality of those ingredients.

A study that tracked nearly 200,000 men and women in the US for around 30 years found that some low-fat and low-carb diets are better for heart health than others.

What separates them?

The key was the quality of the food itself, not the quantity of carbs or fats.

The research, led by public health researchers at Harvard University, suggests that if a diet contains too many processed foods and animal proteins or fats, or if it otherwise lacks in adequate vegetables, fruits, whole grains, healthy fats, or essential macronutrients, it may not benefit cardiovascular health as much in the long run, even if it is low carb or low fat by definition.

"Our findings highlighted that it's not simply about cutting carbs or fat, but it's about the quality of foods people choose to construct those diets," concluded Harvard epidemiologist Zhiyuan Wu, who led the research, published in February.

"Focusing only on nutrient compositions but not food quality may not lead to health benefits."

Participants in the study who ate healthy, varied diets with adequate macronutrients showed higher levels of 'good' cholesterol in their blood, as well as lower levels of fats and inflammatory markers compared to those who ate diets lacking in those essentials.

They also had a significantly lower risk of developing coronary heart disease, the most common cause of heart attacks.

"These results suggest that healthy low-carbohydrate and low-fat diets may share common biological pathways that improve cardiovascular health," explained Wu.

"Focusing on overall diet quality may offer flexibility for individuals to choose eating patterns that align with their preferences while still supporting heart health."

The findings are based on the self-reported diets of participants, who were all health professionals, so they may have had higher health awareness and better access to health care than the general population.

Related: This Diet Change Cuts Over 300 Calories a Day, Without Decreasing Meal Size

That's somewhat limiting; however, the length of follow-up in the study is impressive, amounting to more than 5.2 million person-years.

The findings join growing evidence suggesting that eating fewer processed foods and more whole grains and vegetables is generally best for a wide range of health outcomes.

Strict diets that count calories, carbs, or fats may not be necessary.

"This study helps move the conversation beyond the long-standing debate over low-carbohydrate versus low-fat diets," said Yale University cardiologist Harlan Krumholz, editor-in-chief of the Journal of the American College of Cardiology.

"The findings show that what matters most for heart health is the quality of the foods people eat. Whether a diet is lower in carbohydrates or fat, emphasizing plant-based foods, whole grains, and healthy fats is associated with better cardiovascular outcomes."

The study was published in the Journal of the American College of Cardiology.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.

It's hard to imagine pregnancy care without the ultrasound.

Since the 1950s, this incredible technology has provided an essential snapshot into the womb.

Now, scientists are taking it up a notch by trying to provide a continuous window of imaging.

In the coming years, new inventions may allow prospective parents and their physicians to monitor a developing fetus for hours on end, without the need for a traditional handheld ultrasound device or a sonographer standing by.

That sounds like sci-fi, but the proof of concept already exists.

Scientists at the University of California San Diego, Stanford, and Oxford have now invented a wearable ultrasound patch, called UPatch.

Mariana Tome, study co-author and obstetrics doctor at the University of Oxford, thinks the invention could "transform pregnancy care".

"This is the kind of technology obstetrics has been waiting for," she claims.

Like a handheld ultrasound, UPatch sends high-frequency sound waves inside the body to bounce off structures.

The returning echoes are then read by special software to capture a real-time view of what's going on inside the body.

UPatch sticks to the skin of the abdomen, where it 'reads' the echoes of red blood cells deep within the vessels of a developing fetus.

It can even accurately measure anatomical features of the fetus, such as the head circumference, abdominal circumference, or femur length, thereby providing an estimated weight.

Most impressively, UPatch does all this autonomously, without the need for a trained sonographer on hand.

The patch needs to be connected to a bulky backend powering system, and it doesn't work when a mother is walking or moving too much, but it is technically hands-free.

"Babies in the womb still cannot be monitored reliably, which is a major gap in maternity care worldwide, with huge implications. Solutions are needed urgently," says Antoniya Georgieva, a reproductive health researcher at Oxford.

"The UPatch technology opens the possibility of monitoring the most important signals of fetal health over much longer periods, gain essential new knowledge of how babies' oxygen supply and wellbeing adapt inside the womb, and ultimately helping clinicians identify problems earlier."

When researchers tested the patch on 62 pregnancies within a clinical setting, it performed on par with current ultrasound devices.

For one participant, the patch even noticed a dangerous change in blood flow to the fetus, signaling preeclampsia.

"Following the detection of compromised fetal health using the UPatch, the preeclamptic participant underwent intensive monitoring and the baby was delivered by Cesarean section four days later," write the study authors.

During pregnancy, ultrasounds are regularly recommended to monitor the health of both the mother and the child.

In higher-risk pregnancies, where patients are kept in the clinic for longer periods of time, ultrasounds are done multiple times a week.

Each one of those scans, however, takes time and requires a sonographer to use a handheld device to focus on parts of the uterus.

UPatch allows patients to be monitored in bed for hours, without the need for a clinician to move the device's focus or interpret the results in real time.

If UPatch is used in conjunction with classical imaging techniques, then perhaps pregnancy outcomes could be greatly improved, its inventors argue.

"This technology could expand access to prenatal imaging in healthcare deserts and low-resource settings, where shortages of trained sonographers often delay care for high-risk pregnancies," says Tom Park, the main engineer who designed and fabricated UPatch.

After comparing the patch to current ultrasound devices, the researchers then tested the patch continuously for between 1 and 6 hours in 52 pregnant women, including those affected by preeclampsia, gestational diabetes, hypertension, or poor fetal growth.

The findings reveal differences between short-term fluctuations in ultrasound readings and longer-term changes that require closer monitoring.

Researchers hope the device can help clinicians more readily detect signs of sustained fetal distress, so they can intervene sooner.

The flexible patch is designed with electrodes and an acoustic lens, so that when it wraps around an expectant mother's abdomen, it provides a window to the entire uterus while sitting, standing, or lying down.

Related: Yawning Is So Contagious You Can Catch It Before You're Born, Study Suggests

It can even provide details on how blood flow rates in the umbilical artery compare to those in the fetus's brain.

"This work shows how advances in soft electronics, ultrasound engineering, and clinical science can come together to address one of the most important unmet needs in pregnancy care," says senior author and engineer Sheng Xu from Stanford.

The study is published in Nature Biotechnology.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.

There's another factor that may matter more.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.