Bacteria responsible for decimating starfish in North America identified

Science Editorial, Aug 4 (EFE).- A scientific team has identified a bacterial species as the cause of sea star wasting syndrome, which has decimated populations along the west coast of North America since 2013 and is behind the widespread loss of seaweed habitats.

This discovery comes more than a decade after the start of the epidemic that has killed billions of sea stars, representing more than 20 different species from Alaska to Mexico. Sea star wasting disease is considered the largest marine epidemic ever documented in nature.

The results of the new four-year research are published in the journal Nature Ecology & Evolution, in an article in which the scientists describe the "elusive" microorganism they say is responsible for the disease: a strain of the bacterium Vibrio pectenicida.

Vibrio is a genus of bacteria that has devastated corals and shellfish, as well as humans (Vibrio cholerae is the pathogen that causes cholera), explains a statement from the Hakai Institute of Canada, which notes that a strain of V. pectenicida has previously been shown to also kill the larvae of several species of scallop.

In sea stars, infection with the FHCF-3 strain of V. pectenicida triggers a severe disease that begins with external lesions and eventually kills the starfish by "melting" their tissues, a process that takes about two weeks after exposure. Affected individuals often become contorted and lose their arms.

Researchers focused on sunflower starfish (Pycnopodia helianthoides), which can grow 24 arms and reach the size of a bicycle wheel. Ninety percent of these have been wiped out by the disease in the last decade, landing them on the International Union for Conservation of Nature's Red List of critically endangered species.

The loss of sunflower sea stars has had widespread and long-lasting effects on coastal ecosystems.

"When we lose billions of sea stars, it really changes the ecological dynamics," says Melanie Prentice of the Hakai Institute and the University of British Columbia.

In the absence of sunflower sea stars, sea urchin populations increase, which means the loss of kelp forests, and that has broad implications for all other marine species and the humans who depend on them.

To reach their conclusions, Prentice's team conducted seven controlled exposure experiments with wild and captive-bred sunflower sea stars in quarantine, which indicated that a live, non-viral agent was involved.

Genetic sequencing was then used to profile the microbial communities of diseased and healthy sea star tissues. This led to the identification of the pathogen Vibrio pectenicida as the disease-causing agent, which was confirmed in laboratory experiments in which the sea stars were exposed to pure samples of the bacteria.

This isn't the first time a study has discussed possible causes of the starfish decline. In more than a decade of research on the disease, various etiological agents have been suggested, the researchers note in their article.

Early experimental work identified a densovirus as the possible causative agent. However, "inconsistencies in experimental results and molecular evidence have refuted this finding."

Now that scientists have identified a pathogen that causes the disease, they can investigate the factors that trigger it and the resistance to it.

One particular pathway is the relationship between this and rising ocean temperatures, as the disease and other Vibrio species are known to thrive in warm waters, says Alyssa Gehman.EFE