Tag Archives: Starfish

Eliminating Predatory Starfish to Safeguard Great Barrier Reef Coral

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A diver injects vinegar into crown-of-thorns starfish as part of a culling program.

CSIRO

A culling program has successfully protected key areas of the Great Barrier Reef from voracious coral-eating starfish. Scientists who analyzed the results say efforts need to be scaled up to further protect coral reefs.

Crown-of-thorns starfish (COTS) are persistent predators of almost all types of coral within Australia’s Great Barrier Reef. Each starfish reaches a diameter of 1 meter and eats 10 square meters of coral reef each year.

Starfish live on coral reefs, and it is believed that increased nutrient input into reef waters due to agriculture and other human factors is increasing their numbers and exacerbating coral destruction. Between 1985 and 2012, they accounted for 40 percent of coral losses in the region.

When starfish erupted across the reef from 2012 to 2022, the Great Barrier Reef Marine Park Authority conducted a massive culling program. A team of divers injects the starfish with a single shot of vinegar or cow bile, which kills the starfish and prevents it from releasing its larvae.

Roger Beeden The Park Service and colleagues found that in areas where timely removals were carried out, outbreaks were limited and coral cover recovered and increased by up to 44%. Where no culling occurred, coral losses were severe. The study also confirmed that by preventing outbreaks on strategically important coral reefs, the larvae do not spread to other reefs on ocean currents, reducing further outbreaks.

To date, the program has focused on 500 of the marine park’s 3,000 reefs scattered throughout the park, which have significant value to the tourism industry or are home to starfish. were chosen because they are known to be important for the spread of

“The results we found in this study are the result of using integrated pest management. [the starfish] Just like managing plague locusts and other pest species, it needs to be done at the right time and on the right reef,” says Beeden.

But researchers recommend expanding the program from the current fleet of five to seven ships to 10 to 15 ships. “At any given time, about a third to a half of his 500 cases are involved in the current outbreak,” Beeden said.

Terry Hughes Researchers at James Cook University in Townsville do not agree that culling programs are worthwhile. “It is becoming increasingly clear that attempts to protect Great Barrier Reef corals by culling crown-of-thorns starfish on a few reefs are just a drop in the ocean,” he says.

Mr Hughes said geographical differences in starfish numbers and coral abundance – which the study attributed to levels of culling in different parts of the Great Barrier Reef – could be explained by which areas had suffered from recent cyclones and coral mass destruction. Events they say could be explained by who is most affected by large-scale bleaching. Professor Beeden acknowledges that it is difficult to separate these factors from the effects of selection, but he says: “Our results are strengthened and are not confounded by the fact that the increase in coral cover in the Townsville region was achieved despite two large-scale bleaching events in 2020 and 2022. do not have” “

Instead, Hughes says the priority should be to tackle global warming, which is accelerating the frequency and intensity of coral bleaching. “Each time there is a bleaching event, the Australian government announces additional funding to eliminate starfish from some coral reefs, shifting the focus away from addressing the causes of these outbreaks and reducing Australia’s greenhouse gas emissions.” he says.

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Source: www.newscientist.com

Starfish possess only a substantial, compressed head and lack a body.

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A juvenile Patilia miniata starfish with fluorescent staining highlighting the skeleton, muscles, and nervous system.

Laurent Formery

Scientists trying to figure out where the starfish’s head is located have come to the surprising conclusion that the starfish is practically the entire body of the animal. The discovery not only solves this long-standing mystery, but also helps us understand how evolution created the dramatic diversity of animal forms on Earth.

Starfish, also known as sea stars, belong to a group of animals called echinoderms, which includes sea urchins and sea cucumbers. Their strange body design has long puzzled biologists. Most animals, including humans, have distinct cranial and caudal ends, and a line of symmetry runs down the middle of the body, dividing it into two halves of its mirror image. Animals with this bilateral symmetry are called bilateral animals.

Echinoderms, on the other hand, have five lines of symmetry radiating from a central point and no physically obvious heads or tails. However, they are closely related to animals like us, having evolved from bilaterally symmetrical ancestors. Even larvae are bilaterally symmetrical and then radically reorganize their bodies as they metamorphose into adults.

These large differences make it difficult for scientists to find and compare equivalent body parts in bilateral animals to understand how echinoderms evolved. “Morphology tells us very little,” he says. Laurent Formery at Stanford University in California. “That’s too strange.”

Formalie and his colleagues decided to examine a set of genes known to direct head-to-tail control. All bilateralist organizations. In these animals, these genes are turned on and expressed in stripes in the outer layers of the developing embryo. The genes expressed in each stripe define which point it is on the cranio-caudal axis.

The aim was to see if gene expression patterns could reveal the hidden “molecular anatomy” of echinoderms. “This particular gene suite is ideal for investigating the diversity of the most extreme forms of animals,” says the team leader. chris lowe, also at Stanford University. “I think echinoderms are a very extreme experiment in how to use that bidirectional network to produce very, very different body plans.”

To the team’s surprise, the gene that determines the head edge of bilateral animals was expressed in a line running down the center of each star star’s lower arm. The next leading gene is expressed on both sides of this line, and so on.

Even more bizarrely, genes normally expressed in the trunk of bilateral animals were missing from the animals’ outer layers. This suggests that the starfish abandoned its trunk region and released its outer layer to evolve in a new direction, Formery said.

The findings show that “the bodies of echinoderms, at least with respect to their external surfaces, are essentially lip-walking heads.” Thurston Lacari from the University of Victoria, Canada, was not involved in the study. Animals like us may have swam away to escape predation. “Echinoderms didn’t need trunks because they were hunched over and armored,” Lacari says.

The idea that echinoderms are “head-like” animals is “interesting and powerful,” he says. Andreas Heyland at the University of Guelph in Ontario, Canada. This raises some very important and fundamental questions about how ecological factors shape the evolution of anatomy, he says. “Finding the underlying conserved patterns provides important insights into how development evolves.”

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Source: www.newscientist.com