Sea cucumber poop helps ecosystems


This 3 September 2018 video says about itself:

Sea Cucumber Poop Is Surprisingly Good For the Ecosystem | Nat Geo Wild

There are about 1,250 different species of sea cucumber across the world’s oceans. This is Thelenota anax. And yes, it’s doing what you think it’s doing. Sea cucumber poop is surprisingly important for the ecosystem.

Sea stars keep kelp forests alive


This December 2017 video says about itself:

Sunflower Seastar: Terrifying Predator? | National Geographic

This animal is more than three feet wide and one of the fastest animals in its biome! It’s also a very efficient scavenger.

From Simon Fraser University in Canada:

Sea stars critical to kelp forest resilience

August 13, 2018

A study by Simon Fraser University resource and environmental management researcher Jenn Burt reveals that sunflower sea stars play a critical role in the resilience of B.C. [British Columbia] ‘s kelp forests, which are among the most productive ecosystems on Earth. Similar to land-based forests, kelp forests provide essential habitat for species and also help remove CO2 from the atmosphere.

Burt and her team discovered sea otters and sunflower stars are complementary predators of sea urchins, which inhabit rocky reefs and voraciously eat kelp. Without natural predators, sea urchins quickly devour entire kelp forests.

“We showed that sea otters feed on large sea urchins, whereas the sunflower sea stars eat the small and medium-sized urchins that otters ignore”, says Burt. “We observed kelp density was highest at reefs with both sea otters and sunflower stars.”

The researchers made this discovery after Sea Star Wasting Disease killed 96 per cent of the sunflower star biomass on the Central coast in 2015 and 2016. During this period there was a 311 per cent increase in small and medium-sized sea urchins, which corresponded to a 30 per cent decrease in kelp density.

Burt says ecological surprises such as mass mortality events can reveal new insights into species interactions and ecosystem dynamics. She says these will become more important to learn from as climate change and other stressors make our future ocean ecosystems more unpredictable.

The combination of ocean warming and an infectious wasting disease has devastated populations of large sunflower sea stars once abundant along the West Coast of North America in just a few years, according to research co-led by the University of California, Davis, and Cornell University published Jan. 30 in the journal Science Advances: here.

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 study. The research provides new insight into the complex predator-prey relationships in kelp forests that can be seen in the absence of sea otters: here.

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: here.

Sea urchins seeing with their feet


This 2016 video says about itself:

Conceived in the open sea, tiny spaceship-shaped sea urchin larvae search the vast ocean to find a home. After this incredible odyssey, they undergo one of the most remarkable transformations in nature.

From Lund University in Sweden:

Sea urchins see with their feet

June 12, 2018

Sea urchins lack eyes, but can see with their tentacle-like tube feet instead, previous research has indicated. Now, researchers at Lund University in Sweden have tested their vision in a new study, and shown that while sea urchins have fairly low resolution vision — it is good enough to fulfill their basic needs.

Sea urchins are currently the only animals that have been shown to see without having eyes. They see using light-sensitive cells in their tube feet, which resemble tentacles and, like the spines, are all over the body. You could say that the entire sea urchin is one single compound eye”, says John Kirwan, who conducted the study as a part of his doctoral thesis, together with colleagues at Lund University.

The tube feet have other functions besides registering light. They are used for feeding and in some species are used by the sea urchin for locomotion. Others are used to attach to surfaces or as levers to correct its position when upside down.

John Kirwan studied the sea urchin species Diadema africanum. The experiments placed the animals in water inside strongly illuminated cylinders that had various dark images on the walls.

“Ordinarily, sea urchins move towards dark areas in order to seek cover. When I notice that they react to certain sizes of images but not to others, I get a measurement of their visual acuity”, explains John Kirwan.

To obtain further data, he carried out another experiment in which he showed rapidly growing figures above the sea urchins, as a way of conjuring up an image of an approaching predator. He then registered how large the figures had to be before the sea urchins would defend themselves by directing their spines towards the shadow above.

The acuity of vision was calculated using X-ray tomography and electron microscopy.

John Kirwan’s calculations show that of the 360 degrees surrounding the sea urchin an object must take up between 30 and 70 degrees for the sea urchin to see it. Humans only need an object to take up 0.02 degrees in order to detect it, making it clear that their eyesight is poor in comparison with human eyesight.

“However, this is still sufficient for the animal’s needs and behaviour. After all, it’s hardly poor eyesight for an animal with no eyes”, John Kirwan concludes.

For some, sea urchins are a pretty addition to an aquarium, while for others they are simply an ingredient in a common type of sushi. However, for developmental biologists, they represent more than 100 years of research and education. Because their eggs are transparent, embryonic development and even the act of fertilization were easily viewed with microscopes in the 1800s. Beyond the embryo, sea urchins have long lives — some species living up to 200 years — making them interesting for developmental biologists who study aging: here.

Sea cucumbers, essential for ecosystems


This video says about itself:

Seeking shelter up a sea cucumber’s bottom – World’s Weirdest Events: Episode 5 – BBC Two

The oceans are a hostile place, and you’re going to need some good shelter if you want to survive. The pearl fish has found a rather inventive way to keep away from predators…by hiding up a sea cucumber‘s bottom.

From the Wildlife Conservation Society:

Study in Fiji finds that removing sea cucumbers spells trouble for shallow coastal waters

June 5, 2018

Summary: The sea cucumber’s unimpressive appearance belies the outsized role these creatures play in converting decomposing organic matter into recyclable nutrients and keeping coastal ecosystems healthy and clean, and overfishing them can have negative impacts on coastal marine environments, according to a new study focusing on a species of sea cucumber called a sandfish.

The lowly sea cucumber strikes observers as a simple sausage-like creature, one that is far less interesting than brightly colored reef fish or color-changing octopi that share its coastal habitat.

The sea cucumber’s unimpressive appearance belies the outsized role these creatures play in converting decomposing organic matter into recyclable nutrients and keeping coastal ecosystems healthy and clean, and overfishing them can have negative impacts on coastal marine environments, according to a new study focusing on a species of sea cucumber called a sandfish in the journal PeerJ.

The authors of the study titled “Effects of sandfish (Holothuria scabra) removal on shallow-water sediments” are: Steven Lee of the Leibniz Centre for Tropical Marine Research and the University of Bremen; Amanda K. Ford of the Leibniz Centre for Tropical Marine Research and the University of Bremen; Sangeeta Mangubhai of WCS (Wildlife Conservation Society); Christian Wild of the University of Bremen; and Sebastian C.A. Ferse of Leibniz Centre for Tropical Marine Research and the University of Bremen.

In a sense, sea cucumbers are the vacuum cleaners of coastal marine environments. Since these invertebrates are also the target of a growing demand from Asian markets — dried sea cucumbers are known as “bêche-de-mer” — the authors of the study sought to examine the ecological implications of removing them from tropical coastal areas.

“Our study was designed to determine exactly how the removal of these organisms is impacting coastal ecosystems, which in this case was a coral reef flat in Fiji“, said lead author Steven Lee.

The experiment focused on a specific species of sea cucumber known as the sandfish (Holothuria scabra), and was conducted along a wide reef flat along the coast of Vanua Levu, Fiji for several months between September 2015 and February 2016. After conducting a standard survey of the site in order to determine the density of sandfish on the sea bottom, the researchers created 16 square plots with four “treatments” containing different densities of sea cucumbers, all of which were designed to ascertain the implications of harvesting, and overharvesting, sea cucumbers from the reef.

The research team found that, in plots with high densities of sea cucumbers, oxygen conditions within the sediment stayed relatively stable, even under elevated sea surface temperatures experienced during the 2015/2016 El Niño event. In plots where all sea cucumbers had been removed, the penetration of oxygen into surface sediments decreased substantially, by 63 percent.

Overall, the researchers found that a reef’s ability to handle increases in organic matter inputs from rainfall and flooding inland was diminished by the removal of sea cucumbers.

“Our findings suggest that overharvesting of sandfish and other sea cucumber species could have lasting effects on the marine ecosystems of small Pacific islands such as those in Fiji, resulting in changes that could limit the productivity of shallow water ecosystems”, said Dr. Sangeeta Mangubhai, Director of WCS’s Fiji Program. “Hopefully these results will help inform management decisions that will conserve moderate to high densities of sea cucumbers and protect these ecosystems in the interest of safeguarding coastal livelihoods and food security.”

“Sea cucumbers are an important source of livelihood for many tropical coastal communities and are heavily fished throughout the tropical belt, but so far we didn’t have a good understanding of the wider ecological implications of harvesting them” said Dr. Sebastian Ferse of the Leibniz Centre for Tropical Marine Research (ZMT) in Bremen, who collaborated with WCS in conducting this study as part of a project that looks into the social and ecological resilience of coral reefs in the South Pacific. “The results of this study fill an important knowledge gap and are timely for the management of an important resource for coastal communities.”

This work was supported by: the Leibniz Centre for Tropical Marine Research (ZMT); WCS; University of Bremen; the University of the South Pacific; and the residents of Natuvu village who permitted the study within their traditional fishing ground.

2018 has been designated by the International Coral Reef Initiative as the third International Year of the Reef. This is a great opportunity to come together to strengthen awareness on the plight of coral reefs, to step up and initiate conservation efforts.

Marine animals revolution after dinosaur extinction


This 2015 video from the USA says about itself:

What the heck is a crinoid? They might be one of the most common fossils this side of the Rocky mountains but they are seriously cool.

From the British Antarctic Survey:

Major shift in marine life occurred 33 million years later in the South

May 17, 2018

A new study of marine fossils from Antarctica, Australia, New Zealand and South America reveals that one of the greatest changes to the evolution of life in our oceans occurred more recently in the Southern Hemisphere than previously thought. The results are published today (17 May 2018) in the journal Communications Biology.

The Marine Mesozoic Revolution (MMR) is a key theory in evolutionary history. While dinosaurs ruled the land, profound changes occurred in the shallow seas that covered the Earth.

During the Mesozoic, around 200 million years ago, marine predators evolved that could drill holes and crush the shells of their prey. And although small in comparison to dinosaurs, these new predators, including crustacea and some types of modern fish, had a dramatic impact on marine life.

Among the species most heavily affected were sea lilies or isocrinids — invertebrates tethered to the seafloor by graceful stalks. Side on, these stalks resemble a vertebral column; in cross section, they are shaped like a five-pointed star — because sea lilies are related to starfish, sea urchins, and sand dollars. At their height during the Paleozoic, forests of sea lilies carpeted seafloors the world over.

Their restricted ability to move made sea lilies vulnerable to the new predators, so during the MMR they were forced into deeper waters in order to survive. Because it marked such a radical change in marine communities, scientists have long sought to understand this shift. They believed it occurred around 66 million years ago, but this new study shows that in the Southern Hemisphere, sea lilies remained in shallow waters until much more recently — around 33 million years ago.

A team from British Antarctic Survey, the University of Cambridge, the University of Western Australia, and the Royal Botanic Gardens, Victoria, made the discovery when they brought together field samples from Antarctica and Australia, with fossils from museum collections for the first time. The study provides conclusive evidence that this change happened at different times in different parts of the globe, and in the Antarctic and Australia, sea lilies hung on in shallow waters until the end of the Eocene, around 33 million years ago and it is unknown exactly why.

The study shows that knowing more about the Antarctic can reshape — or overturn — existing scientific theories.

According to lead author Dr Rowan Whittle from British Antarctic Survey: “It is surprising to see such a difference in what was happening at either end of the world. In the Northern Hemisphere these changes happened whilst the dinosaurs ruled the land, but by the time these sea lilies moved into the deep ocean in the Southern Hemisphere the dinosaurs had been extinct for over 30 million years.

“Given how the ocean is changing and projected to change in the future it is vital that we understand how different parts of the world could be affected in different ways and at a range of timescales.”

To get this richer picture of how sea lilies responded to the changing oceans of the Southern Hemisphere over millions of years, the team travelled to some of the remotest regions of Western Australia and Antarctica. Their hunt for fossil sea lilies was rewarded by the discovery of nine new species.

Co-author Dr Aaron Hunter from the University of Cambridge says: “We have documented how these sea lilies evolved as Australia split away from Antarctica moving north and becoming the arid outback we know today, while ice formed over the South Polar Region.

“The sea lilies survived in the shallow waters for millions of years longer than their Northern Hemisphere cousins, but as the continents moved further apart, they eventually had nowhere to go but the deep ocean depths where they have clung on to existence to this day.”

Starfish mass death on English beach


This video from England says about itself:

4 March 2018

Tens of thousands of starfish were washed up on Ramsgate beach in Kent after ‘The Beast From The East’, Storm Emma passed by. The sudden drop in temperature is thought to have killed the sea creatures.

What a pity so many of these beautiful animals died. One should hope that now these starfish will at least help to feed gulls, sanderlings and other birds.

How Silurian echinoderms ate


This October 2015 video from Utah State University in the USA is called What does the fossil record reveal about the evolution of Echinoderms?

By Laurel Hamers, 7:05pm, September 12, 2017:

Like sea stars, ancient echinoderms nibbled with tiny tube feet

Rare 430-million-year-old fossils preserve signs of these tentacle-like limbs

Sea stars and their relatives eat, breathe and scuttle around the seafloor with tiny tube feet. Now researchers have gotten their first-ever look at similar tentacle-like structures in an extinct group of these echinoderms.

It was suspected that the ancient marine invertebrates, called edrioasteroids, had tube feet. But a set of unusually well-preserved fossils from around 430 million years ago, described September 13 in Proceedings of the Royal Society B, provides proof.

Usually, when an echinoderm dies, “the tube feet are the first things that go,” says Colin Sumrall, a paleobiologist at the University of Tennessee, Knoxville who wasn’t part of the study. “The thing that’s so stunning is that they didn’t rot away.”

An abundance of soft-bodied creatures from the Silurian Period, which lasted from 443 to 416 million years ago, are preserved in a fossil bed in Herefordshire, England. The edrioasteroids found in this bed were probably buried alive by volcanic ash, entrapped before their soft tissues could break down, says study coauthor Derek Briggs, a paleontologist at Yale University. Decaying tissue then left a void that was filled in by minerals, which preserved the shape of the appendages.

Briggs and his collaborators slowly ground three fossils down, taking pictures layer-by-layer to build up a three-dimensional view. The specimens are a new genus and species, the analysis revealed. Unlike relatively flat sea stars and sand dollars, the species — dubbed Heropyrgus disterminus — had a conical body about 3 centimeters long. Its narrower end anchored in the seabed. The other end sported a set of five plates partially covering dozens of tube feet arranged in a pentagonal ring.

Today’s echinoderms use hydraulic pressure in a water vascular system to extend and retract their tube feet, which serve a variety of roles. The feet can help animals pull in tiny particles of food, filter water or gases, and even inch along the seafloor. Based on the placement of H. disterminus’s tube feet (and the fact that it’s stuck in one place), the animal probably used the appendages mostly for feeding and gas exchange, Briggs suggests. The fossils didn’t preserve the internal tubing that hooks up to the tube feet, but Briggs’ team thinks that it’s a series of canals arranged like spokes connected to a wheel hub.

Sumrall isn’t surprised that this edrioasteroid had tube feet. “It’s exactly what we would have expected,” he says. But all other preserved tube feet to date come from classes of echinoderms that still have living relatives today. Edrioasteroids are less closely related to modern echinoderms, so this find broadens the range of species that scientists know sported the structures.

H. disterminus does have a few surprises, though: Its tube feet are found in two sets, in an arrangement not seen in any other echinoderms. And while it has five-point symmetry in its fleshy top part (like most other echinoderms), that transitions to eight-point symmetry in its long, columnar body.

Sea stars sighted predators 79 million years ago: here.

Brittle stars fossils discovery in Australia


This video says about itself:

13 August 2017

Australia was a different place 275 million years ago – wild storms surged through icy seas, and marine animals lived a tenuous existence. But brittle stars had a survival strategy.

From the University of Cambridge in England:

Meadow of dancing brittle stars shows evolution at work

August 14, 2017

Newly-described fossil shows how brittle stars evolved in response to pressure from predators, and how an ‘evolutionary hangover’ managed to escape them.

Researchers have described a new species of brittle star, which are closely related to starfish, and showed how these sea creatures evolved in response to the rise of shell-crushing predators during the late Palaeozoic Era. The results, reported in the Journal of Systematic Palaeontology, also suggest that brittle stars evolved new traits before the largest mass extinction event in Earth’s history, and not after, as was the case with many other forms of life.

A fossilised ‘meadow’ of dancing brittle stars — frozen in time in the very spot that they lived — was found in Western Australia and dates from 275 million years ago. It contains several remarkably preserved ‘archaic’ brittle stars, a newly-described genus and species called Teleosaster creasyi. They are the last known complete brittle stars of their kind, an evolutionary hangover pushed to the margins of the world’s oceans by the threat from predators.

The researchers, from the University of Cambridge, suggest that while other species of brittle stars evolved in response to predators such as early forms of rays and crabs, these archaic forms simply moved to where the predators weren’t — namely the seas around Australia, which during the Palaeozoic era was pushed up against Antarctica. In these cold, predator-free waters, the archaic forms were able to grow much larger, and lived at the same time as the modern forms of brittle star, which still exist today.

Brittle stars consist of a central disc and five whip-like appendages, which are used for locomotion. They first appear in the fossil record about 500 million years ago, in the Ordovician Period, and today there are about 2,100 different species, mostly found in the deep ocean.

Early brittle stars were just that: brittle. During the Palaeozoic Era, when early shell-crushing predators first appeared, brittle stars made for easy prey. At this point, a split in the evolutionary tree appears to have occurred: the archaic, clunky brittle stars moved south to polar waters, while the modern form first began to emerge in response to the threat from predators, and was able to continue to live in the warmer waters closer to the equator. Both forms existed at the same time, but in different parts of the ocean.

“The threat from predation is an under-appreciated driver of evolutionary change,” said study co-author Dr Kenneth McNamara of Cambridge’s Department of Earth Sciences. “As more predators began to appear, the brittle stars started to evolve more flexible bodies, which enabled them to either burrow into the sediment, or to move more rapidly to escape.”

About 250 million years ago, the greatest mass extinction in Earth’s history — the Permian-Triassic extinction event, or the “Great Dying” — occurred. More than 90% of marine species and 70% of terrestrial species went extinct, and as a result, most surviving species underwent major evolutionary changes as a result.

“Brittle stars appear to have bucked this trend, however,” said co-author Dr Aaron Hunter, a visiting postdoctoral researcher in the Department of Earth Sciences. “They seem to have evolved before the Great Dying, into a form which we still see today.”

Meadows of brittle stars and other invertebrates such as sea urchins and starfish can still be seen today in the seas around Antarctica. As was the case during the Palaeozoic, the threat from predators is fairly low, although the warming of the Antarctic seas due to climate change has been linked to the recent arrival of armies of king crabs, which represent a real threat to these star-filled meadows.

Brittle Stars inspire new generation of robots able to adapt to physical damage: here.

Scientists have discovered the first evidence that brittle stars living in vibrant coral reefs use thousands of light sensors to navigate their way through their complex environments: here.

Big sea cucumber in Egypt


This video says about itself:

This Bizarre Sea Creature is Snake-like and Has Tentacles | National Geographic

25 July 2017

Meet one of the world’s longest sea cucumbers, which has tentacles on its head.

A diver filmed this bizarre sea creature at the bottom of the Red Sea off Egypt. It’s likely its species is Synapta maculata—one of the world’s largest sea cucumbers. They can grow to be seven to ten feet long, and they filter feed by capturing floating organic matter with their feather-like tentacles.