A mystery killer wiped billions of sea stars. Biologists have just resolved the case.

Columbo, eat your heart: a team of scientists has just resolved a massive mystery of sea murder, catching the culprit behind the death of billions of sea stars in the last decade.

In a new study, researchers in the United States and Canada argue that the bacterial cousin of cholera is behind the epidemic. Thanks to a series of experiences involving wild and captive starfish, they have found proof that Vibrio Pectenicida is the likely cause of the waste of the sea star of the sea – a devastating condition which makes the invertebrates decompose and “melt”.

The team’s results seem to be well supported by evidence, Zak Swartz, a biologist specializing in sea stars at the Navy Biological Laboratory who was not involved in the study, told Gizmodo.

“This study definitively passes the sniff test for me. It seems quite convincing that V. Pectonida Bacteria is at least one SSW causal agent, “said Swartz.

Sea Stars began to disappear in 2013 when a huge SSWD epidemic struck the North American coast of the Pacific. The disease swept the seas from Alaska to Mexico, decimating more than 20 different species of starfish, also known as seasome. The distressed creatures first develop visible lesions on their skin, then their fabrics begin to decompose. Death by SSWD is often fast, killing the sea star in a few days.

There have been other dying of mass of sea star in recent decades, but the scale and the spread of this epidemic may make it the greatest epidemic of marine disease ever recorded in nature. Researchers believe that a particular species of seasart, PYLIANTHOIDES PYCNOPODIAlost 90% of its population against SSWD. Destruction has also considerably changed the environments where the stars of the sea formerly prospered. In the aftermath of SSWD epidemics, some regions also lost the Varech forests, because the sea urchins – once being in failure by the starfish – were medical underwater forests.

Marine scientists have been looking for the cause of the SSWD since its emergence. And like any great mystery, there have been some twists and turns. In 2014, a research team published an article which argued that a densovirus associated with the stars of the sea caused SSWD. But subsequent studies have shown that this virus – or any potentially pathogenic virus by the way – could only be found in a minority of affected species, the existing as the most likely suspect.

Swartz noted that some Vibrio Bacteria, however, were already known to cause an echinoderms-the large group of marine invertebrates which includes starfish. “So, in a sense, it feels like the answer was just hidden under our nose. This has a total meaning,” he said. Several species of Vibrio can also weaken humans, including cholera (Vibrio cholerae)).

Researchers did not participate in this study with V. Pectonida in mind from the start. They exhaustively studied star seasle samples with SSWD and healthy specimens, finally noting that only sick seas of sea bore high levels of bacteria in their coelomical fluid (the invertebrate blood version). The researchers were then able to isolate and develop new populations of bacteria collected from the star’s starfish. And when they have exposed healthy starfish to these bacteria, creatures developed quickly and died of SSWD.

These experiences are of the same type used to identify and show a particular germ in a specific germ causes a specific disease in humans, strengthening the team’s case. A more in-depth analysis also revealed that the SSWD is caused by a specific strain of bacteria, called FHCF-3.

“Here, we use controlled exposure experiences, genetic data sets and field observations to demonstrate that the bacteria, Vibrio Pentcida Strain FHCF-3, is a causal agent of SSWD”, wrote the authors in their article, published Monday in nature and evolution.

Although the mystery of what causes the SSWD seems resolved, Swartz and the study authors note that there are still several important questions. For example, scientists do not know exactly how epidemics start. Bacteria may be able to propagate by shared food from sea stars, or by physical contact with other seasicks. Low levels of bacteria can also always circulate in the environment, but only become a major problem in specific conditions, as at a certain temperature (Vibrio Bacteria in general thrive in warmer water).

However, given that SSWD remains a threat to the stars of the sea, the simple fact of knowing that its cause could stimulate the efforts to restore the starfish, the researchers said. It may be possible to find genetic mutations that help the starfish to repel these infections, for example, allowing scientists to raise starfish bearing these mutations in captivity in order to reintroduce them in nature to strengthen the resilience of the population.