How a one‑eyed creature gave rise to our modern eyes

There is a tiny cyclops among your oldest ancestors, and humans share these remarkable ancestral roots with all other vertebrates. Researchers have found that all vertebrates evolved from a distant ancestor that had a single eye located at the top of its head. The study, published in Current Biology, also reveals that the remnants of this so-called median eye have today become the pineal gland in our brains.

This cyclops-like creature, which is our very distant relative, existed almost 600 million years ago. It was a small, worm-like organism that had adopted a sedentary lifestyle and fed by filtering plankton from seawater. Previously, this creature had some form of paired eyes, like most other animals.

We don't know whether the paired eyes in our branch of the evolutionary tree were just light-sensitive cells or simple image-forming eyes. We only know that the organism later lost them.
The increasingly calm lifestyle meant that the worm-like creature no longer needed paired eyes, and therefore that function was lost over the course of evolution. However, the animal kept a group of light-sensitive cells in the middle of its head. These cells developed into a small, primitive median eye that could keep track of night and day, and sense what was up and down.
Over the following millions of years, our distant ancestor once again began to live an active, swimming life, increasing the need for paired eyes. From parts of the small median eye, new image-forming eyes in pairs developed, the researchers conclude in the study.
Now we finally understand why the eyes of vertebrates differ so radically from the eyes of all other animal groups, such as insects and squid. The film of our eyes—the retina—developed from the brain, whereas the eyes of insects and squid originate in the skin on the sides of the head.
In other words, vertebrate eyes constitute a more modern model that evolved thanks to this peculiar detour via a cyclops' sedentary life. The conclusion that our modern eyes evolved through this specific evolutionary path, and not via some other ancient animal, is based on the researchers' extensive analysis of light-sensitive cells in all animal groups, as well as the physiology and placement of these cells in the body.
All vertebrates evolved from an ancestor with a single median eye atop its head, which later became the pineal gland in the brain. This median eye, originally used for light detection, was retained after the loss of paired eyes and eventually gave rise to the paired, image-forming eyes of modern vertebrates. The retina’s brain origin distinguishes vertebrate eyes from those of other animals.

George Kafetzis et al, Evolution of the vertebrate retina by repurposing of a composite ancestral median eye, Current Biology (2026). DOI: 10.1016/j.cub.2025.12.028

Why corals bleach: Neutrons show algae photosynthesis breaking down

Rising sea temperatures are causing coral reefs around the world to bleach. For the first time, a research team has investigated the biological processes behind coral bleaching directly in living corals. With the help of neutrons, they were able to visualize structural changes during the bleaching process.
Rising sea temperatures disrupt photosynthesis in coral-associated algae by altering the structure of their thylakoid membranes. Using small-angle neutron scattering, researchers directly observed these structural changes in living corals, linking membrane stress to the breakdown of symbiosis and subsequent coral bleaching. Persistent bleaching can lead to coral death.

Robert W. Corkery et al, In hospite and ex hospite architecture of photosynthetic thylakoid membranes in Symbiodinium spp. using small-angle neutron scattering, Journal of Applied Crystallography (2025). DOI: 10.1107/s1600576725007332

Women with severe burn injuries are more likely than men to develop blood poisoning

The skin forms a natural barrier that prevents bacteria entering the body. Severe burns stop this protective function from working properly, and germs can enter the blood more easily through the wounds. If the airways have suffered thermal or chemical injury through the inhalation of hot and toxic substances, they are also a gateway for infection.
Bacteria can multiply in the blood and spread throughout the body. In the worst case, this can cause blood poisoning—also known as sepsis—which can lead to multiple organ failure. This is a common cause of death in people with burn injuries. A new study has identified for the first time which patients are affected by such infections. The study was carried out before the disaster in Crans-Montana, but it can now help to better understand the physiological processes in critically ill burn patients.

The study focused on sex-specific differences. It analyzed data from 269 patients with severe burn injuries who were treated at the Center for Severe Burn Injuries at the University Hospital Zurich between 2017 and 2021. The insights, published in Burns, should help to prevent sepsis in patients with severe burn injuries or get it under control at an early stage.

Women with severe burn injuries are nearly twice as likely as men to develop bacteremia, which can progress to sepsis. This increased risk is not due to different bacterial species but may relate to altered immune or hormonal responses following burns. Understanding these mechanisms could improve prevention and management of sepsis in burn patients.
Women's immune systems often seem better able to cope with pathogens, and a number of studies have observed a stronger immune response.
In burn victims, however, it seems that this is not necessarily the case. The researchers are not yet able to answer the question of why the women with severe burn injuries in this cohort were much more likely to develop bacteremia.
One explanation that can be ruled out, however, is the presence of different pathogens, as predominantly the same bacteria were identified in the blood of male and female patients. These are species that colonize the skin and mucous membranes as part of the natural microbiome. They are usually harmless but can become dangerous if they enter the bloodstream in large quantities.
Sex hormones have an effect on human immune cells, which also fight infections. Female sex hormones such as estrogen are actually associated with a better response. But it is possible that burn injuries alter hormone metabolism, which then weakens the immune response, say the researchers.
While patients are usually given antibiotics early to fight the bacteria, the damaged barrier means that new infections keep occurring. Resistant bacteria can also quickly develop, for which very few effective antibiotics are available.

Nicole J.M. Schweizer et al, Impact of sex on the development of bacteremia in critically ill burn patients: A retrospective cohort study, Burns (2026). DOI: 10.1016/j.burns.2025.107845