Mediterranean sea urchins are more vulnerable than previously thought

FEBRUARY 7, 2020

by University of Barcelona

The sea urchin Paracentrotus lividus, an eatable species of great commercial interest found in the Mediterranean and North-East Atlantic, is more vulnerable than so far believed.

This is stated in a study by the University of Barcelona, the Spanish National Research Council (CSIC) and the University of Tromsø (Norway) on the genetic distribution of populations of this species, led by the experts Marta Pascual, from the Faculty of Biology and the Biodiversity Research Institute (IRBio) of the University of Barcelona, and Xavier Turon, CSIC research professor at the Center for Advanced Studies of Blanes (CEAB-CSIC). The study has been recently published in the journal Diversity and Distributions.

Using a genetic analysis of the populations of this sea urchin, this work assesses its population structure and connectivity as a result of its dispersal ability. Scientists analysed about 250 individuals of Paracentrotus lividus from eleven marine areas, ranging from the French Atlantic coast to the eastern Mediterranean.

Researcher Xavier Turon (CEAB-CSIC) notes that "adult sea urchin barely move," and that dispersal occurs during the larval stage, since "when they are larvae, they swim in the plankton and are carried away by marine currents. We thought they had a high dispersal capability, since they have a long larval lifespan, which lasts for weeks."

What the study reveals is that "the dispersal is not as wide as we expected," says Turon, "and geographical barriers such as the Strait of Gibraltar limit the connectivity of populations. The exchange of sea urchin larvae between different areas is more limited than what we thought."

Another shocking result is that the selection at a local level is having an impact on the genetic make-up of the different populations of urchins. "We found different allele composition among populations," note researchers Marta Pascual and Carles Carreras (UB-IRBio). "When we analysed the genetic sequences in which these differences appeared, we saw that they lay in genes that code for processes related to temperature and salinity." There is a strong selection pressure related to temperature in the Mediterranean, which can have important consequences regarding global warming.

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Marine scientists discover an important, overlooked role sea urchins play in the kelp forest ecosystem

JULY 10, 2019

by Harrison Tasoff, University of California - Santa Barbara

Sea urchins have gotten a bad rap on the Pacific coast. The spiky sea creatures can mow down entire swaths of kelp forest, leaving behind rocky urchin barrens. An article in the New York Times went so far as to call them "cockroaches of the ocean." But new research suggests that urchins play a more complex role in their ecosystems than previously believed.

A team led by Christie Yorke, a postdoctoral scholar at UC Santa Barbara's Marine Science Institute, studied how urchins might function to break up tough kelp into more manageable pieces that can feed other scavengers, also known as detritivores, living on the kelp forest floor. The paper, published in the Proceedings of the Royal Society B, is the first to look at sea urchins' role as shredders in the kelp forest ecosystem.

Urchins can have an outsized effect on kelp forests, especially when their predators aren't around to keep their population in check, Yorke explained. Overhunting of the sea otter, one of urchins' most significant predators, has allowed some urchin populations to clear cut vast tracts of kelp forest, drastically reducing the productivity and biodiversity of sites they've munched through. Some groups have even taken to indiscriminately smashing urchins to stem this scourge.

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Role of sea urchins on California kelp

The new research provides valuable information to understand and protect California's quintessential kelp forests

Date:  March 14, 2019

Source:  San Diego State University

California sheephead and spiny lobsters may be helping control sea urchin populations in Southern California kelp forests, where sea otters -- a top urchin predator -- have long been missing, according to a new San Diego State University (SDSU) study published in the journal Ecology. The research provides new insight into the complex predator-prey relationships in kelp forests that can be seen in the absence of sea otters.

The study is also the first to experimentally test the relative impact, or rate of feeding, of the California sheephead and spiny lobsters in comparison to sea otters, whose historical range spanned from British Columbia, Canada to Baja California, Mexico.

"Healthy kelp forests are important both economically and ecologically along our coast. They act as nurseries and vital habitat for valuable fishery species, recreation sites for kayakers, free divers, and scuba divers, and serve as the base of rocky reef food webs," says Robert Dunn, who led the study as a Ph.D. candidate at SDSU and University of California, Davis, funded by a NMFS-California Sea Grant Fellowship.

Kelp forests rely on the proper balance of herbivory and predation. Sea urchins dwell on the seafloor where they forage on macroalgae, including giant kelp. If their populations are left unchecked by predation, they can decimate kelp forests and prevent kelp from growing. That can transform a thriving community of kelp into an oceanic desert, known as an urchin barren.

The relationships between predators and prey vary among communities. Sea urchins have recently decimated kelp forests in Northern California, leaving researchers to wonder why Southern California kelp forests have remained relatively intact without sea otters to control the urchin populations.

Past research has indicated that Marine Protected Areas in Southern California house a diversity of predators -- warranting fewer urchins and abundant kelp. Dunn and his SDSU graduate advisor, Kevin Hovel, set out to better understand the potential for top-down control by these two distinct predators: the California sheephead and spiny lobsters.

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Sea Urchins Launch Their Weird Mobile Jaws to Scare Predators

By Stephanie Pappas, Live Science Contributor | April 24, 2017 07:08am ET

A common and colorful sea urchin has some truly bizarre appendages that seem to move independently from its body, and now scientists know why: It shoots these tiny, venomous jaws into the water to deter predators.

These teensy, toothy jaws are called pedicellariae, and when scientists discovered them in the early 1800s, they thought the jaws were parasites because they seemed to move independently from the urchin. Now, researchers find that urchins use their pedicellariae not only to defend themselves when attacked, but also as a warning to fish and other sea creatures to "stay away!"

Tripneustes gratilla, otherwise known as the collector urchin, is a widespread species found in shallow waters in the Bahamas, the Indo-Pacific region and even the Red Sea.



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For Sex-Changing Fish, Size Matters in Urchin Battle

by Becky Oskin, Senior Writer | December 12, 2014 06:12am ET

A sex-changing California fish is growing bigger and gobbling up more sea urchins after a decade of being protected from fishing, a new study finds.

In the Channel Islands offshore Southern California, the sheephead fish population has bounced back from overfishing since marine protected areas were established around the islands in 2002. Biologists are finding more large males and more egg-producing (larger) females.

And the bigger fish have bigger mouths, which is all the better for breakfasting on the rampant, kelp-destroying populations of sea urchins in the region. An 8-inch (20 centimeters) sheephead fish has a diet that is only 2 percent urchin, whereas an 18-inch (45 cm) sheephead munches on so many urchins that they make up 30 to 40 percent of its diet, according to the study, published Dec. 10 in the journal Proceedings of the Royal Society B.

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Enhancing green sea urchin egg production

Enhancing green sea urchin egg production to aid Maine's depressed urchin market is the research focus of a University of Maine marine bioresources graduate student.

Ung Wei Kenn, a second-year master's student from Kuala Lumpur, Malaysia, hopes to increase the egg or roe yield of farm-raised green sea urchins through high-quality feed, a process known as bulking. His research is part of a two-year, more than $215,000 research project funded by the National Sea Grant National Strategic Initiative and led by director Nick Brown and biologist Steve Eddy of UMaine's Center for Cooperative Aquaculture Research (CCAR) in Franklin, Maine.

"I was always interested in the vertical integration of aquaculture and seafood processing," says Ung, who completed his undergraduate work at the University of Tasmania, Australia. "I am also passionate about seafood that is popular in Asia. This topic is a blend of all that."

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Global Warming Causes 'Acid Indigestion' for Sea Urchins

Spiny green sea urchins face a new challenge from climate change: As the oceans become more acidic, urchin larvae struggle to digest theirfood, new research finds.

The study is the first to prove that ocean acidification can cause digestive problems for marine animals, though scientists have long been alarmed at the trend for other reasons. Ocean acidification has threatened oyster farms, slowed coral growth and caused common marine snails to shrink, among other effects.

Earlier studies have focused on calcification, or the process by which marine animals draw minerals from the water to build shells and skeletons, study researcher Meike Stumpp, a former Ph.D. student at the GEOMAR Helmholtz Centre for Ocean Research and the University of Kiel in Germany, said in a statement.

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Seven new species of sea urchins discovered in New Zealand

Deep water sea urchins have been little studied

June 2013. Seven new species of sea urchins (Known as Tam o'Shanters) have been discovered in a collection of urchins at the New Zealand National Institute of Water and Atmospheric Research's (NIWA) Invertebrate Collection.

Deep water fisheries scientist Owen Anderson says unfortunately people have little chance of seeing any of the new species alive because they live so deep in the ocean. They are not found on beaches and are too deep for divers to see so to find one is incredibly rare. They are occasionally seen when caught in deep sea nets.

Live in deep water

"These urchins live at a depth of 100-1200 metres and are named Tam o'Shanter as their shape is similar to a Scottish hat. New Zealand waters are rich with diversity when it comes to this urchin group - there are about 50 known species in the world with nearly a third of these found in New Zealand waters."

These deep sea urchins do not have a hard shell like their cousin kina and the various tropical species that can be seen in less than 10 metres of water, instead the Tam o'Shanter have a flexible leathery outer skin adapted for the deep sea environment in which they live, says Mr Anderson.

"There are many different kinds of urchins, which I hadn't appreciated before I started researching kina but now I am hooked. I love the symmetry and detail of the shell plating, they are very beautiful. I had the privilege of naming the seven new species and I'm also in the process of researching, identifying, and describing a further seven species."

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Baby Sea Urchins Use Allergy Chemical to Grow Up

Most humans experience some growing pains, but, for a young sea urchin, growing up means turning yourself inside out.

New research explores the key role a familiar substance, histamine, plays in this dramatic metamorphosis from a free swimming larva to the more familiar spiny adult that lives on the seafloor.

Well known to allergy sufferers for its association with sneezing, watery eyes and other symptoms, histamine prepares a sea urchin larva to transform into a radically different adult form within an hour, said study researcher Andreas Heyland, an assistant professor at the University of Guelph in Canada.

"They turn essentially inside out, like a sock," Heyland said.

Sea-urchin larvae swim freely in the ocean, living among other tiny organisms known as plankton, and as they mature they drift deeper into the sea. Before they can settle down on the seafloor, where they will spend the rest of their lives, the larvae must be able to pick up on environmental cues that tell them they are in the right spot.

Continued:  http://www.livescience.com/19937-sea-urchin-histamine-metamorphosis.html

Wrasse and starfish gang up on sea urchins

SEA urchins beware: you are under attack from two sides. Wrasse and starfish are both partial to sea urchin, but struggle to catch it on their own. So they give each other a helping hand to tackle their common prey.

Ornate wrasse, Thalassoma pavo, like to eat the tube feet of sea urchins, but as the urchins keep their feet buried in the sea bed the wrasse can't get to them easily. Marthasterias glacialis, a starfish, also likes sea urchin but isn't always fast enough to catch them.

Nicola Galasso of Tuscia University in Viterbo, Italy, and colleagues have found that the two help each other out. When a sea urchin is attacked by a starfish, it uproots itself and moves away. That exposes its tube foot, so a lurking wrasse can sweep in for a meal. The wrasse's feast disables the sea urchin, allowing the starfish to catch it and finish the job.

The two predators don't seem to be truly cooperating as neither makes a sacrifice for the other. But their actions nevertheless benefit each other. It is further evidence that wrasse are intelligent and can adapt their foraging methods, says Galasso, who presented her research last week at the summer conference of the Association for the Study of Animal Behaviour in St Andrews, UK. She has also found that ornate wrasse have learned to follow scuba divers, as they often break open sea urchins to attract fish.

http://www.newscientist.com/article/mg21128284.300-wrasse-and-starfish-gang-up-on-sea-urchins.html?DCMP=OTC-rss&nsref=online-news

Sea urchins see with their whole body

Many animals have eyes that are incredibly complex – others manage without. Researchers at the University of Gothenburg have shown that sea urchins see with their entire body despite having no eyes at all. The study has been published in the scientific journal Proceedings of the National Academy of Sciences (PNAS).

Most animals react to light and have developed a very sophisticated way of seeing complex images so that they can function in their surroundings. Good examples include insects' compound eyes and the human eye. Charles Darwin and other evolutionary biologists were bewildered by the eye's complexity and wondered how this kind of structure could have evolved through natural selection.

But some creatures, such as sea urchins, can react to light even though they do not have eyes. Previous studies of sea urchins have shown that they have a large number of genes linked to the development of the retina, which is the light-sensitive tissue in the human eye. This means that sea urchins have several genes that are coded for a widely occurring eye protein, opsin.

"It was this discovery that underpinned our research," says Sam Dupont from the University of Gothenburg's Department of Marine Ecology, one of the researchers behind the study and co-authors of the article. "We wanted to see where the opsin was located in sea urchins so that we could find the sensory light structures, or photoreceptors. We quite simply wanted to know where the sea urchin sees from."

The research group behind the study showed that the photoreceptors seem to be located on the tip and base of the tube feet that are found all over the sea urchin's body and are used to move.

"We argue that the entire adult sea urchin can act as a huge compound eye, and that the shadow that is cast by the animal's opaque skeleton over the light-sensitive cells can give it directional vision," says Dupont.

Source: University of Gothenburg via EurekAlert!

http://archaeologynewsnetwork.blogspot.com/2011/06/sea-urchins-see-with-their-whole-body.html

Algal bloom spreads along coast

An algal bloom blamed for killing worms, sea urchins and other sea creatures has spread along the west coast of Scotland.

The Scottish Environment Protection Agency, (Sepa), said the bloom was now in Loch Ryan in Dumfries and Galloway.

If follows reports last week of the same issue affecting waters at Bute, Ayr, Prestwick and West Kilbride.

Sepa said the bloom was likely to be dispersed by the tide and was no danger to humans or other mammals.

Sepa's Alistair McNeill said the number of dead sea invertebrates had caused public concern.

"Understandably people were worried that this was the result of a pollution incident, but it appears that this is a natural phenomenon," he said.

"This plankton was linked with similar problems elsewhere in Scotland in 2006.

"The bloom is likely to disperse naturally with tidal movement and under the influence of changing weather patterns."

A spokesman for Dumfries and Galloway Council's environmental standards department said there was currently "no risk to public health".




http://news.bbc.co.uk/1/hi/scotland/south_of_scotland/8142907.stm