Horrible condition turning Starfish into Goo has finally been identified

In 2013, the lives of millions of starfish mysteriously died out. Limbs that were once strong, probing their arms for food, shriveled and tore from the rest of their body and melted into a sickly slime.

“There were guns everywhere,” said environmentalist Drew Harvell AtlanticEd Yong last year. “It looked like an explosion zone.”

The dismal remains of these animals, which are usually able to regenerate their own limbs, have been strewn across the west coast of North America, in one of the largest wildlife mass death events on record. . Over 20 species of starfish perished.

In some areas, the sunflower star (Pycnopods helianthoides), populations plummeted by an average of 90 percent within a few weeks, a loss that saw this once common and abundant species disappear from most of its range in just a few years.

The culprit behind this Starfish Wastage (SSW) has even reached captive starfish, killing individual animals within days.

Leg Pisaster ochraceus disintegration of starfish wasting syndrome. (Elizabeth Cerny-Chipman / Oregon State University / CC BY-SA 2.0)

This has led scientists to suspect that some sort of pathogen, like a virus or bacteria, is infecting these amazing sea creatures. However, subsequent studies exonerated the main viral suspect.

Meanwhile, more starfish deaths followed around the world, including half a world in Port Phillip Bay, Australia.

Now, marine biologist Citlalli Aquino from San Francisco State University and his colleagues have finally solved the mystery, showing that something much more complicated was going on.

By comparing the types of bacteria in healthy starfish and those with wasting disease, the researchers found that bacteria that thrive in low oxygen environments were abundant in sick animals, as were copiotrophs. – bacteria that like environments rich in nutrients.

Laboratory experiments confirmed that the depletion of oxygen in the water caused tissue melting damage in 75% of starfish. Adding excess nutrients or phytoplankton to the water also resulted in a deterioration in the health of the starfish.

By reanalyzing tissue samples from the 2013 event, researchers detected excess nitrogen – a sign the animals had suffocated to death.

“Starfish diffuse oxygen on their outer surface through small structures called papules, or skin gills,” said Cornell University marine microbiologist Ian Hewson. “If there is not enough oxygen around the papules, the starfish cannot breathe.”

These microorganisms do not directly cause disease, but steal the oxygen supply of starfish when increased levels of organic matter trigger microbes to bloom. As a result, starfish literally drown in their own surroundings. Then their decaying bodies further increase nutrients for the microbes, creating a horrible feedback loop of starfish death.

Aquino and his team noted that most SSW events are reported in late fall or summer, when phytoplankton that increase nutrient levels in the water via photosynthesis is more abundant.

Warmer temperatures are known factors in phytoplankton blooms, and Australia’s starfish dieback episode followed the longest and most intense heat wave on record. Starfish dieback events elsewhere have also followed the rise in sea temperatures.

“Warmer waters can’t have so much oxygen [compared with colder water] just by physics, ”Hewson told Erin Garcia de Jesus at Scientific news.

None of this bodes well for our future on a warming planet.

Melissa Pespeni, a biologist at the University of Vermont, who was not involved in the study, said Scientific news this complex entanglement of biological and environmental factors is “a new kind of idea for [disease] transmission.”

The devastating repercussions of the loss of these precious sea stars have already rippled through entire ecosystems. The sunflower star is a voracious predator with up to 24 arms that extend up to 1 meter (3.3 feet), making their way through the seabed for sea urchins, snails and other invertebrates to devour.

Without the sunflower and other starfish that control sea urchins, these herbivores make their way through giant kelp forests. By 2016, sea urchins had already reduced kelp populations by 80% in some areas, decimating these once thriving underwater forests.

“This is a very clear example of a trophic cascade, which is an ecological domino effect triggered by changes at the end of a food chain,” said Isabelle Côté, marine ecologist at Simon Fraser University, who last year investigated the environmental consequences.

“It’s a stark reminder that everything is connected with everything else.”

This research was published in Frontiers in microbiologyand.