This 2016 video shows buzzards feeding in Belarus.
On 10 January 2020, a buzzard on a branch in the forest.
Great spotted woodpecker.
Two Egyptian geese land at a meadow where four others are present already. They are welcomed, or are they shown they are unwelcome?
On the beach, sanderlings.
Also at least five egg cases of thorny skates.
This 6 December 2020 video from the USA says about itself:
In this new Blue World adventure, Jonathan takes Zach-Of-All-Trades on a dive in Eastport, Maine to meet Gene the World-Famous wolffish, and his next-door neighbors, Bob and Jane the Wolffish. Along the way they also examine the variety of marine life that lives in Passamaquoddy Bay!
This September 2015 video from the United States Virgin Islands says about itself:
Bonefish, (Albula vulpes); Lackland Marine Sanctuary U.S.V.I.
From Florida Atlantic University in the USA:
Stunning discovery reveals bonefish dive 450 feet ‘deep’ into the abyss to spawn
December 7, 2020
Summary: Using active acoustic telemetry and sonar data, a study provides the first detailed documentation of a shallow-water fish diving 450 feet deep to spawn. Prior research has shown that bonefish dive about 164 feet to spawn, but this new and unprecedented study reveals that they reached depths of 450 feet, and moved below 325 feet for two hours before spawning in a rush upward to 220 feet deep.
A new study provides the first detailed documentation of a shallow-water fish diving 450 feet deep to spawn. Uncovering this very rare spawning behavior in bonefish (Albula vulpes) is unprecedented. Using active acoustic telemetry and sonar data along the southern shore of Abaco, The Bahamas, a team of scientists led by Florida Atlantic University’s Harbor Branch Oceanographic Institute in collaboration with Bonefish & Tarpon Trust, and University of Massachusetts Amherst, has discovered that although bonefish live in shallow waters less than 6 feet, they dive “deep” into the abyss to spawn.
While prior research in 2013 showed that bonefish descended approximately 164 feet to spawn, this new scientific finding reveals that bonefish descended to depths reaching 450 feet, and moved below 325 feet for two hours before spawning in a rush upward to 220 feet deep. Findings from the study, published in the journal Marine Biology, will be instrumental for conservation efforts for this economically and culturally important fish species.
“We were stunned by this discovery because the bonefish moved out beyond the incredibly abrupt and steep shelf drop off into the Providence Channel in Abaco,” said Steven Lombardo, first author and a Ph.D. candidate who works with Matt Ajemian, Ph.D., senior author, an assistant research professor at FAU’s Harbor Branch and head of the Fisheries Ecology and Conservation (FEC) Lab. “Data from our acoustic telemetry tags showed us in real time that bonefish were capable of handling extreme pressures. When they reached 334 feet in the first dive, we were floored, and 45 minutes later when they reached 450 feet deep, we were absolutely astonished.”
Active acoustic telemetry enabled the scientists to observe the spawning movements and is a method that employs small pill-like tags that are surgically implanted into the fish’s abdominal cavity, emitting an ultrasonic ping every three seconds. Researchers listened for the pings emitted from the tags using a boat-mounted directional hydrophone, using the strength of the signal communicated from the tag to the hydrophone to determine what direction to move the boat and follow the fish. Each ping transmitted by the tag inside the fish relayed data to the scientists, informing them of the depth of the fish’s location and the water temperature.
The researchers spent four days from sunrise to sunset observing the bonefish pre-spawning aggregation in hopes that they would move offshore to spawn. At sunset on the final scheduled night of their research cruise, bonefish began “porpoising,” where they gulped air at the surface, and then proceeded to move offshore following the edge of the continental shelf. The successful observation of bonefish spawning capped an 18-hour shift on the water, spanning two days.
“Following the bonefish on their offshore spawning migration was a marathon for the science team as well as the fish,” said Aaron Adams, Ph.D., co-author, senior scientist at FAU’s Harbor Branch and director of science and conservation at Bonefish & Tarpon Trust. “Most importantly for conservation, now that we know the conditions bonefish require to spawn we can better focus our efforts for habitat conservation.”
When many species of coastal marine fish spawn, they spawn in groups known as spawning aggregations, which are mixed males and females. These fishes follow a process known as “broadcast spawning” in which the males and females eject sperm and eggs into the open water where the eggs are fertilized. The eggs hatch in about a day, and the tiny larvae that hatch from the eggs live in the open ocean as plankton for days to months, depending on the species, before finding shallow water and becoming juveniles. Adults of many of these species migrate long distances from their home ranges to spawning locations, often spawning on the edges of reefs adjacent to deep water.
Unlike other coastal marine fishes, the bonefish partakes in a unique three-point spawning migration, traveling up to 70 miles from shallow water home flats to form nearshore pre-spawning aggregations before moving offshore to reproduce. Once at the pre-spawning location, they gather in large groups often numbering anywhere from 5,000 to 10,000 bonefish.
“Despite their economic and cultural importance, there are concerns about the long-term health of the bonefish fishery. Because of habitat loss and harvest in some locations, bonefish are classified as ‘Near Threatened,’ therefore information on their reproduction is critical to conservation efforts,” said Ajemian. “We are continuing our work on the offshore spawning movements of bonefish. We will be observing more spawning events at different locations and also will characterize what larval bonefish may be feeding on at these great depths.”
This research will support the ongoing efforts of the Bonefish Reproduction Research Project at FAU’s Harbor Branch, informing techniques used to rear captive spawned bonefish larvae through the feeding phase of development and beyond.
This 2017 video says about itself:
Amazing footage– A Whale Shark covered with Remora Fishes !! ( COMMENSALISM)
This awesome footage was shot at Koh Tao, Thailand courtesy of Underwater Videographer (Lara Dakers).
From the New Jersey Institute of Technology in the USA:
Secret surfing life of remoras hitchhiking on blue whales
October 28, 2020
Summary: A new study of blue whales off the coast of California has given researchers the first ocean recordings of their famous hitchhiking partner — the remora — revealing the suckerfish’s secret whale-surfing skills as well as their knack for grabbing the most flow-optimal spots while riding aboard the world’s largest vertebrate.
Sticking to the bodies of sharks and other larger marine life is a well-known specialty of remora fishes (Echeneidae) and their super-powered suction disks on their heads. But a new study has now fully documented the “suckerfish” in hitchhiking action below the ocean’s surface, uncovering a much more refined skillset that the fish uses for navigating intense hydrodynamics that come with trying to ride aboard a 100-ft. blue whale (Balaenoptera musculus).
In a study published Oct. 28 in the Journal of Experimental Biology, an international team of researchers studying the unique fluid environments of blue whales traveling off the coast of Palos Verdes and San Diego, CA has reported capturing the first-ever continuous recording of remora behavior on a host organism, using advanced biosensing tags with video recording capabilities.
The study shows the secrets behind the remora fish’s success in hitchhiking aboard baleen whales more than 30 times their size to safely traverse the ocean — they select the most flow-optimal regions on the whale’s body to stick to, such as behind the whale’s blowhole, where drag resistance for the fish is reduced by as much as 84%. The team’s findings also show that remoras can freely move around to feed and socialize on their ride even as their whale host hits burst speeds of more than 5 meters per second, by utilizing previously unknown surfing and skimming behaviors along special low-drag traveling lanes that exist just off the surface of the whale’s body.
Researchers say the study represents the highest-resolution whole-body fluid dynamic analysis of whales to date, the insights from which could potentially be used as a basis to better understand the behavior, energy use and overall ecological health of the species, as well as improve tagging and tracking of whales and other migratory animals in future studies.
“Whales are like their own floating island, basically like their own little ecosystems. …To get a look into the flow environment of blue whales within a millimeter resolution through this study is extremely exciting,” said Brooke Flammang, assistant professor of biology at New Jersey Institute of Technology and the study’s corresponding author. “Through lucky coincidence, our recordings captured how remoras interact in this environment and are able to use the distinct flow dynamics of these whales to their advantage. It is incredible because we’ve really known next to nothing about how remoras behave on their hosts in the wild over any prolonged period of time.”
Until now, scientists studying the symbiotic relationships between remoras and their hosts in their natural ocean habitat have predominantly relied on still images and anecdotal evidence, leaving much of how they go about their renown sticking behavior beneath the surface a mystery.
In their recent investigation, the researchers employed multi-sensor biologging tags with dual cameras that they attached to the whales via four 2-inch suction disks. The tags were able to calculate various measurements inside the whale’s ecosystem, such as surface pressure and complex fluid forces around the whales, as well as GPS location and traveling speeds through tag vibrations, all while video recording the remoras at 24 frames per second and 720p resolution.
“Fortunately, the drag on dimple-shaped airplane cockpits has been measured many times and we were able to apply this knowledge to help figure out the drag these remoras were experiencing,” said Erik Anderson, co-author, biofluid dynamics researcher at Grove City College and guest investigator at the Woods Hole Oceanographic Institution. “But our study still required calculating, for the first time ever, the flow over a blue whale using computational fluid dynamics … it took an international team of biologists, programmers, engineers and a supercomputer to do that.”
The team’s 211 minutes of video footage and whale tag data processed by researchers at the Barcelona Supercomputing Center captured a total of 27 remoras at 61 locations on the whales overall, finding that the remoras were most often podding and traveling between three of the most hydrodynamically beneficial spots where separating flow and wakes are caused by the whale’s distinct topographical features: directly behind the blowhole, next to and behind the dorsal fin, and the flank region above and behind the pectoral fin.
According to the team’s measurements, Anderson says that the sheer force experienced by an average-sized remora in the wake behind the blowhole of a whale swimming at the casual speed of 1.5 m/s can be as low as 0.02 Newtons, half the force of drag in the free stream above. However, Anderson notes that the average remora’s suction force of 11-17 Newtons is more than a match for even the most intense parking spot on the whale, its tail, where the remora experiences roughly 0.14 Newtons of shear force. And though the forces are greater, the same is true even for large remora riding on whales swimming at much higher speeds.
“We learned that the remora’s suction disk is so strong that they could stick anywhere, even the tail fluke where the drag was measured strongest, but they like to go for the easy ride,” said Erik Anderson. “This saves them energy and makes life less costly as they hitchhike on and skim over the whale surface like a NASA probe over an asteroid or some mini-world.”
Remoras Go Surf’s Up
The tags showed that to conserve energy while getting about on their floating island, the remoras take advantage of the whale’s physics by surfing inside a thin layer of fluid surrounding the whale’s body, known as a boundary layer, where the team found drag force is reduced by up to 72% compared to the much more forceful free stream just above. Flammang says the fishes can lift within 1cm from their host in this layer to feed or join their mates at other low-drag social spots on the whale, occasionally changing directions by skimming, or repeatedly attaching and releasing their suction disks on the whale’s body.
Flammang suspects that remoras are able to move freely without being completely peeled from their speedy hosts, which can move nearly seven times faster than the remora, through something called the Venturi effect.
“The skimming and surfing behavior is amazing for many reasons, especially because we think that by staying about a centimeter off the whale body, they are taking advantage of the Venturi effect and using suction forces to maintain their close proximity,” explained Flammang. “In this narrow space between the remora and whale, when fluid is funneled into a narrow space it moves at a higher velocity but has lower pressure, so it is not going to push the remora away but can actually suck it toward the host. They can swim up into the free stream to grab a bite of food and come back down into the boundary layer, but it takes a lot more energy to swim in the free stream flow.”
Along with uncovering new details of the remora’s hitchhiking prowess, the team says they will continue to explore both the flow environments around whales and the mechanisms by which specifically adapted organisms like remoras successfully attach to hosts in order to improve animal tag technologies and designs for extended periods of behavioral and ecological monitoring. The team is also using their new insights into the remora’s preferred low-drag attachment locations to better inform where they might tag whales in studies to come.
“It’s an extremely arduous process to study whales what with permitting, research regulations and the game of chance of finding animals, all for the tags to usually fall off within 48 hours,” said Flammang. “If we can come up with a better way to collect longer-term data through better tag placement or better technologies, it could really advance our learning of the species, and many other animals that remoras attach to.”
This 2018 video says about itself:
385 million years ago, a group of fish would undertake one of the most important journeys in the history of life and become the first vertebrates to live on dry ground. But first, they had to acquire the ability to breathe air.
Thanks to Ceri Thomas for the Ichthyostega reconstruction.
From Uppsala University in Sweden:
Large tides may have driven evolution of fish towards life on land
October 27, 2020
Big tidal ranges some 400 million years ago may have initiated the evolution of bony fish and land vertebrates. This theory is now supported by researchers in the UK and at Uppsala University who, for the first time, have used established mathematical models to simulate tides on Earth during this period. The study has been published in Proceedings of the Royal Society A.
“During long periods of the Earth’s history, we’ve had small tidal ranges. But in the Late Silurian and Early Devonian, they seem to have been large in some parts of the world. These results appear highly robust, because even if we changed model variables such as ocean depth, we got the same patterns,” says Per Ahlberg, professor of evolutionary organismal biology at Uppsala University.
Between 420 and 380 million years ago (Ma) — that is, during the end of one geological period, the Silurian, and beginning of the next, the Devonian — Earth was a completely different world from now. Instead of today’s well-known continents there were other land masses, clustered in the Southern Hemisphere. Stretching across the South Pole was the huge continent of Gondwana. North of it was another big one known as Laurussia, and squeezed between the two were a few small continents. Other salient differences compared with now were that Earth’s day lasted only 21 hours, since our planet revolved faster on its own axis, and the Moon looked much larger because its orbit was closer to Earth.
Life on land had gradually begun to get established. But the vertebrates, then consisting only of various kinds of fish, were still to be found only in the oceans. Then, during the Devonian, immense diversification of fish took place. One group to emerge was the bony fish, which make up more than 95 per cent of all fish today but were also the ancestors of terrestrial vertebrates. The earliest bony fish were the first animals to evolve lungs. What set off the evolution of bony fish, and how some of them started to adapt to a life on land, has not been clarified. One theory is that it happened in tidal environments where, in some periods, fish had been isolated in pools as a result of particularly large tides. This challenging habitat may have driven the evolution of lungs and, later on, the transformation of fins into front and hind legs.
To test this tidal theory, researchers at Uppsala University, in collaboration with colleagues from the Universities of Oxford and (in Wales) Bangor, used an established mathematical model of the tidal system for the first time to simulate, in detail, the tides in the Late Silurian and Early Devonian. Data on the positions of the continents, the distance of the Moon, the duration of Earth’s day, our planet’s gravity and the physical properties of seawater were fed into the model. These simulations showed unequivocally that the period, just like that of the present day, was one when large tides occurred in some places. The small continent of South China on the Equator showed a difference of more than four metres in sea level between high and low tide. The existence of tides at the time has previously been verified through studies of geological strata, but determining the extent of the difference between low and high tide has not been feasible. To researchers this news has been interesting, since fossil finds indicate that it was specifically around South China that bony fish originated.
“Our results open the door to further and even more detailed tidal analyses of key episodes in Earth’s past. The method can be used to explore the possible role of tides in other evolutionary processes of vertebrate development. And perhaps, conversely, whether tides, with their influence on ocean dynamics, played a part in the big marine extinctions that have taken place again and again in Earth’s history,” Ahlberg says.
This 2016 video from Mexico is called Face to face with huge smooth hammerhead in Cabo San Lucas.
From Nova Southeastern University in the USA:
New shark research targets a nearly endangered species
September 15, 2020
They are some of the most iconic and unique-looking creatures in our oceans. While some may think they look a bit “odd”, one thing researchers agree on is that little is known about hammerhead sharks. Many of the 10 hammerhead shark species are severely overfished worldwide for their fins and in need of urgent protection to prevent their extinction.
To learn more about a declining hammerhead species that is data-poor but in need of conservation efforts, a team of researchers from Nova Southeastern University’s (NSU) Save Our Seas Foundation Shark Research Center (SOSF SRC) and Guy Harvey Research Institute (GHRI), Fisher Finder Adventures, the University of Rhode Island and University of Oxford (UK), embarked on a study to determine the migration patterns of smooth hammerhead sharks (Sphyrna zygaena) in the western Atlantic Ocean. This shark, which can grow up to 14-feet (400 cm), remains one of the least understood of the large hammerhead species because of the difficulty in reliably finding smooth hammerheads to allow scientific study.
To learn about smooth hammerhead behavior, the research team satellite-tagged juvenile hammerhead sharks off the US Mid-Atlantic coast and then tracked the sharks for up to 15 months. The sharks were fitted with fin-mounted satellite tags that reported the sharks’ movements in near real-time via a satellite link to the researchers.
“Getting long-term tracks was instrumental in identifying not only clear seasonal travel patterns, but importantly, also the times and areas where the sharks were resident in between their migrations,” said Ryan Logan, Ph.D. student at NSU’s GHRI and SOSF SRC, and first author of the newly published research. “This study provides the first high resolution, long term view of the movement behaviors and habitats used by smooth hammerhead sharks — key information for targeting specific areas and times for management action to help build back this depleted species.”
The researchers found that the sharks acted like snowbirds, migrating between two seasonally resident areas — in coastal waters off New York in the Summer and off North Carolina in the Winter. Their residency times in these two locations coincided with two environmental factors: warmer surface water temperatures and areas with high productivity — indicative of food-rich areas.
“The high-resolution movements data showed these focused wintering and summering habitats off North Carolina and New York, respectively, to be prime ocean “real estate” for these sharks and therefore important areas to protect for the survival of these near endangered animals,” said Mahmood Shivji, Ph.D., director of NSU’s GHRI and SOSF SRC, who oversaw the study.
Identifying such areas of high residency provides targets for designation as “Essential Fish Habitat” — an official title established by the US Government, which if formally adopted can subsequently be subject to special limitations on fishing or development to protect such declining species.
The tracking data also revealed a second target for conservation. The hammerheads spent a lot of resident time in the winter in a management zone known as the Mid-Atlantic Shark Area (MASA) — a zone already federally closed for seven-months per year (January 1 to July 31) to commercial bottom longline fishing to protect another endangered species, the dusky shark. However, the tracking data showed that the smooth hammerheads arrived in the MASA earlier in December, while this zone is still open to fishing.
“Extending the closure of the MASA zone by just one month, starting on December 1 each year, could reduce the fishing mortality of juvenile smooth hammerheads even more,” said Shivji. “It’s particularly gratifying to see such basic research not only improving our understanding of animal behavior in nature but also illuminating pathways for recovery of species and populations that have been overexploited so we can try and get back to a balanced ocean ecosystem.”
The tracks of the smooth hammerheads (and other shark species) can be found here.
This 9 September 2020 video from England says about itself:
410-Million-Year-Old Fish Fossil Virtual 3D CT Scan
Virtual three-dimensional model of the braincase of Minjinia turgenensis generated from CT scan.
Credit: Imperial College London/Natural History Museum
From Imperial College London in England:
Ancient bony fish forces rethink of how sharks evolved
September 7, 2020
Sharks’ non-bony skeletons were thought to be the template before bony internal skeletons evolved, but a new fossil discovery suggests otherwise.
The discovery of a 410-million-year-old fish fossil with a bony skull suggests the lighter skeletons of sharks may have evolved from bony ancestors, rather than the other way around.
Sharks have skeletons made of cartilage, which is around half the density of bone. Cartilaginous skeletons are known to evolve before bony ones, but it was thought that sharks split from other animals on the evolutionary tree before this happened; keeping their cartilaginous skeletons while other fish, and eventually us, went on to evolve bone.
Now, an international team led by Imperial College London, the Natural History Museum and researchers in Mongolia have discovered a fish fossil with a bony skull that is an ancient cousin of both sharks and animals with bony skeletons. This could suggest the ancestors of sharks first evolved bone and then lost it again, rather than keeping their initial cartilaginous state for more than 400 million years.
The team published their findings today in Nature Ecology & Evolution.
Lead researcher Dr Martin Brazeau, from the Department of Life Sciences at Imperial, said: “It was a very unexpected discovery. Conventional wisdom says that a bony inner skeleton was a unique innovation of the lineage that split from the ancestor of sharks more than 400 million years ago, but here is clear evidence of bony inner skeleton in a cousin of both sharks and, ultimately, us.”
Most of the early fossils of fish have been uncovered in Europe, Australia and the USA, but in recent years new finds have been made in China and South America. The team decided to dig in Mongolia, where there are rocks of the right age that have not been searched before.
They uncovered the partial skull, including the braincase, of a 410-million-year-old fish. It is a new species, which they named Minjinia turgenensis, and belongs to a broad group of fish called ‘placoderms‘, out of which sharks and all other ‘jawed vertebrates’ — animals with backbones and mobile jaws — evolved.
When we are developing as foetuses, humans and bony vertebrates have skeletons made of cartilage, like sharks, but a key stage in our development is when this is replaced by ‘endochondral’ bone — the hard bone that makes up our skeleton after birth.
Previously, no placoderm had been found with endochondral bone, but the skull fragments of M. turgenensis were “wall-to-wall endochondral.” While the team are cautious not to over-interpret from a single sample, they do have plenty of other material collected from Mongolia to sort through and perhaps find similar early bony fish.
And if further evidence supports an early evolution of endochondral bone, it could point to a more interesting history for the evolution of sharks.
Dr Brazeau said: “If sharks had bony skeletons and lost it, it could be an evolutionary adaptation. Sharks don’t have swim bladders, which evolved later in bony fish, but a lighter skeleton would have helped them be more mobile in the water and swim at different depths.
“This may be what helped sharks to be one of the first global fish species, spreading out into oceans around the world 400 million years ago.”
From the University of Bristol in England:
True size of prehistoric mega-shark finally revealed
September 3, 2020
To date only the length of the legendary giant shark Megalodon had been estimated. But now, a new study led by the University of Bristol and Swansea University has revealed the size of the rest of its body, including fins that are as large as an adult human.
There is a grim fascination in determining the size of the largest sharks, but this can be difficult for fossil forms where teeth are often all that remain.
Today, the most fearsome living shark is the Great White, at over six metres (20 feet) long, which bites with a force of two tonnes.
Its fossil relative, the big tooth shark Megalodon, star of Hollywood movies, lived from 23 to around three million years ago, was over twice the length of a Great White and had a bite force of more than ten tonnes.
The fossils of the Megalodon are mostly huge triangular cutting teeth bigger than a human hand.
Jack Cooper, who has just completed the MSc in Palaeobiology at the University of Bristol’s School of Earth Sciences, and colleagues from Bristol and Swansea used a number of mathematical methods to pin down the size and proportions of this monster, by making close comparisons to a diversity of living relatives with ecological and physiological similarities to Megalodon.
The project was supervised by shark expert Dr Catalina Pimiento from Swansea University and Professor Mike Benton, a palaeontologist at Bristol. Dr Humberto Ferrón of Bristol also collaborated.
Their findings are published today in the journal Scientific Reports.
Jack Cooper said: “I have always been mad about sharks. As an undergraduate, I have worked and dived with Great whites in South Africa — protected by a steel cage of course. It’s that sense of danger, but also that sharks are such beautiful and well-adapted animals, that makes them so attractive to study.
“Megalodon was actually the very animal that inspired me to pursue palaeontology in the first place at just six years old, so I was over the moon to get a chance to study it.
“This was my dream project. But to study the whole animal is difficult considering that all we really have are lots of isolated teeth.”
Previously the fossil shark, known formally as Otodus megalodon, was only compared with the Great White. Jack and his colleagues, for the first time, expanded this analysis to include five modern sharks.
Dr Pimiento said: “Megalodon is not a direct ancestor of the Great White but is equally related to other macropredatory sharks such as the Makos, Salmon shark and Porbeagle shark, as well as the Great white. We pooled detailed measurements of all five to make predictions about Megalodon.”
Professor Benton added: “Before we could do anything, we had to test whether these five modern sharks changed proportions as they grew up. If, for example, they had been like humans, where babies have big heads and short legs, we would have had some difficulties in projecting the adult proportions for such a huge extinct shark.
“But we were surprised, and relieved, to discover that in fact that the babies of all these modern predatory sharks start out as little adults, and they don’t change in proportion as they get larger.”
Jack Cooper said: “This means we could simply take the growth curves of the five modern forms and project the overall shape as they get larger and larger — right up to a body length of 16 metres.”
The results suggest that a 16-metre-long Otodus megalodon likely had a head round 4.65 metres long, a dorsal fin approximately 1.62 metres tall and a tail around 3.85 metres high.
This means an adult human could stand on the back of this shark and would be about the same height as the dorsal fin.
The reconstruction of the size of Megalodon body parts represents a fundamental step towards a better understanding of the physiology of this giant, and the intrinsic factors that may have made it prone to extinction.
This 3 December 2018 video is called Pike React to Fish in a Bottle.
From the University of Groningen in the Netherlands:
How sticklebacks dominate perch
Analysis reveals waves of stickleback domination along the Baltic coast
August 27, 2020
A research project on algal blooms along the Swedish coast, caused by eutrophication, revealed that large predators such as perch and pike are also necessary to restrict these blooms. Ecologist Britas Klemens Eriksson from the University of Groningen and his colleagues from Stockholm University and the Swedish University of Agricultural Sciences, Sweden have now shown that stickleback domination moves like a wave through the island archipelagos, changing the ecosystem from predator-dominated to algae-dominated. Their study was published on 27 August in the journal Communications Biology.
Eriksson experimented with the effects of nutrients on algal blooms while working as a postdoctoral researcher in Sweden. When he added nutrients to exclusion cages in the brackish coastal waters, algae began to dominate. This was no surprise. However, when he excluded large predators, he saw similar algal domination. ‘Adding nutrients and excluding large predators had a huge effect,’ he recalls, 10 years later.
Food web
The big question that arose from these results using small exclusion cages was whether the results would be the same for the real Swedish coastal ecosystem. This coast consists of countless archipelagos that stretch up to 20 kilometres into the sea, creating a brackish environment. Here, perch and pike are the top predators, feeding on sticklebacks, which themselves eat the small crustaceans that live off algae.
To investigate how this food web developed over the past 40 years, Eriksson (who had moved to the University of Groningen in the Netherlands) connected with his colleagues at Stockholm University and the Swedish University of Agricultural Sciences to gather data on fish abundances and to carry out a series of field studies. They were inspired by recent suggestions that regime shifts can occur in closed systems such as lakes and wondered whether algal blooms in the Baltic sea could also be a consequence of such a regime change.
Grazers
Eriksson and his colleagues sampled 32 locations along a 400-kilometre stretch of coastline. ‘We visited these sites in the spring and autumn of 2014 and sampled all levels of the food web, from algae to top predators.’ These data were subsequently entered into a food web model, which helped them to find connections between species. The models showed that the small sticklebacks were important for the reproduction of the larger predators. And a local increase in sticklebacks means that a lot of the grazers in the ecosystem are eaten, which drives algal domination.
‘If you just look at the abundances of fish, you find a mixed system in which different species dominate,’ Eriksson explains. But looking at the changes in these fishery data over time showed an increase in sticklebacks that started in the late 1990s, initially in the outer parts of the archipelagos. ‘This is presumably caused by a reduction in the number of large predators. The reduction is the combined result of habitat destruction, fishing and increased predation by cormorants and seals.’ Sticklebacks migrate from the outer archipelagos inwards to reproduce, linking coastal and offshore processes.
Predation
Reduced predation increases the survival of sticklebacks, while both eutrophication and warming help to increase their numbers even further. As the sticklebacks reduced the number of grazers, algae began to replace seagrass and other vegetation. Furthermore, the sticklebacks also fed on the larvae of perch and pike, thereby further reducing their numbers. ‘This is a case of predator-prey reversal,’ explains Eriksson. Instead of top predators eating sticklebacks, the smaller fish strongly reduced the number of perch and pike larvae.
Over time, the stickleback domination moved inwards like a wave: regional change propagated throughout the entire ecosystem. This has important consequences for ecosystem restoration. ‘To counter algal blooms, you should not only reduce the eutrophication of the water but also increase the numbers of top predators.’ It means that those organizations that manage fisheries must start working together with those that manage water quality. ‘We should not look at isolated species but at the entire food web,’ says Eriksson. ‘This is something that the recent EU fishery strategy is slowly starting to implement.’
Furthermore, the propagation of local changes throughout a system has wider implications in ecology, especially in natural ecosystems that have complex interaction and information pathways. ‘And we know this from politics and human behaviour studies. A good example is the Arab Spring, which started locally and then propagated across the Middle East.’
This 2015 video says about itself:
The Hillstream Loach is not just cool and interesting, its also very popular in the aquarium hobby with many variants available.
Common/Trade Name: Hillstream Loach, Butterfly Loach
Scientific Name: Sewellia lineolata
Family: Balitoridae
Location: Southeast and East Asia
Max. size: 3 inches / 8 – 9 cm
PH range: 6.0 — 7.4
Temperament: Peaceful. Good candidate for a community fish tank
Temperature range: 68 – 75° F
Care level: Well acclimated specimens are quite hardy. Smaller individuals are quite tolerant of each other but will become more territorial as they grow. This fish prefers well-oxygenated water with plenty of hiding spots. They will scavenge dry and frozen foods. They love water movement, so a circulating powerhead is ideal for keeping these fish happy.
From the New Jersey Institute of Technology in the USA:
Key to fish family’s land-walking abilities revealed in study of Asia’s hillstream loaches
August 26, 2020
Summary: A new genetic and morphological study of South Asia’s hillstream loach (Balitoridae) family is shedding new light on the fishes’ unusual land-walking capabilities, including that of the family’s strangest relative — Cryptotora thamicola — a rare, blind cavefish from Thailand with an uncanny ability to walk on land and climb waterfalls using four limbs that move in salamander-like fashion.
In a study published in the Journal of Morphology, a team of researchers from New Jersey Institute of Technology (NJIT), Florida Museum of Natural History, Louisiana State University and Thailand’s Maejo University have successfully pieced together the ancestral relationships that make up the family tree of hillstream loaches (Balitoridae), detailing for the first time a range of unusual pelvic adaptations across the family that have given some of its members an ability to crawl, or even walk as salamanders do, to navigate terrestrial surfaces.
The team’s DNA-based comparative analysis of the fish family, known to currently encompass more than 100 species native to South and Southeast Asia, is the first of its kind to include Cryptotora thamicola — the only living species of fish known to walk on land in a step pattern similar to tetrapods, or four-limbed vertebrates such as reptiles and amphibians.
The results have revealed that three dominant variations of pelvic anatomy in the family, notably including key variations of a robust pelvic girdle and elongated sacral rib among many loaches, which researchers expect are central in explaining the different degrees of land-walking behavior exhibited by the fishes. The team says that the family’s modified pelvic features enabling terrestrial locomotion, which were found most pronounced in Cryptotora thamicola, may have been adapted to enhance their odds of survival in rivers and other fast-moving water environments that many Balitoridae inhabit today.
“The modified morphology of these Balitoridae, particularly the enlarged sacral rib connecting the pelvic plate to the vertebral column, is a big part of why studying this family is so exciting,” said Callie Crawford, the study’s corresponding author and Ph.D. candidate at NJIT’s Department of Biological Sciences. “These loaches have converged on a structural requirement to support terrestrial walking not seen in other fishes. What we’ve discovered is three anatomical groupings that have major implications for the biomechanics of terrestrial locomotion of these loaches, and the relationships among these fishes suggest that the ability to adapt to fast-flowing rivers may be what was passed on genetically, more than the specific morphology itself.”
“Now that we have revealed a spectrum of pelvic morphologies among these fishes, we can compare the extent of skeletal support with the walking performance in a species,” said Brooke Flammang, the study’s lead principal investigator and assistant professor of biology at NJIT. “This will allow us to measure the mechanical contribution of robust hips to terrestrial locomotion.”
Unlike most living fishes that feature pelvic fins located more anteriorly and attached to the pectoral girdle, balitorids typically boast a skeletal connection between the pelvic plate (basipterygium) and the vertebral column via a modified sacral rib and its distal ligament. These modifications are understood to help generate force against the ground useful for navigating land. The most extreme example emerged in 2016 with the discovery of Cryptotora thamicola in the fast-flowing aquatic conditions of the Tham Maelana and Tham Susa karst cave systems in northern Thailand. NJIT researchers then first identified that the rare species used a robust pelvic girdle attached to its vertebral column to walk and climb waterfalls with a salamander-like gait.
“This trait is likely key to helping these fishes avoid being washed away in the fast-flowing environment that they live in,” said Zach Randall, co-author of the paper and biological scientist at Florida Museum of Natural History. “What’s really cool about this paper is that it shows with high detail that robust pelvic girdles are more common than we thought in the hillstream loach family.”
“The sacral ribs allow forces from the fins pressing against the ground to be transferred to the body so that every time the fin pushes down during a step, the body is pushed up and forward,” explained Flammang. “The increased surface area of the more modified sacral ribs also offers more room for muscle attachment, so fishes such as Cryptotora thamicola can rotate their hips during walking, producing a salamander-like gait.”
River Loach Family Factions
To better understand the evolution of the river loach family, the team conducted a broad sampling of ?CT-scan data taken from 29 representative specimens, analyzing and comparing skeletal structures, muscle morphology as well as sacral rib shape across 14 of the 16 balitorid genera. The team also sampled genomic datasets of 72 loaches across seven families to reconstruct the evolutionary relationships in the Ballitoridae tree of life. “We were able to use a large survey of museum specimens and CT scanning to incorporate data even from specimens that didn’t have tissue or genetic data intact,” noted Randall.
The results showed that the loaches fall into three distinct morphotypes, which are expected to correlate to how well they are able to maneuver on land: species with a long, narrow rib that meets the pelvic plate; species with a thicker, slightly curved rib meeting the pelvic plate; and species with a robust crested rib interlocking with the pelvic plate. Of the species sampled, eleven fell into the third category with advanced land-walking abilities, such as Cryptotora thamicola, displaying the most robust sacral rib connection between the basipterygium and vertebral column.
“Our analysis showed that the morphotypes are not grouped by closely related taxa, but instead appear spread out across the phylogeny. That indicates to us that the extent of the modification of these features is less reflecting shared ancestry and more likely a product of adaptation to the flow regimes of their environments,” explained Crawford. “To better understand how and why these distinct morphotypes developed, we need more knowledge of the habitat of each species, including water flow rates, substrate types and how the rivers and streams change between rainy and dry seasons.”
Crawford and colleagues now aim to further investigate the stability physics and muscular forces at play that allow certain species to push their bodies off their ground as they walk. The team, including a recent Rutgers University graduate, Amani Webber-Schultz, recently completed fieldwork in Thailand earlier this year to collect more balitorid specimens, which they are studying using high-speed videos of the fishes walking.
“This will allow us to study details of their walking kinematics and gain even more insight into how walking performance might change between species with different pelvic morphologies,” said Crawford.
The study was supported by the National Science Foundation’s Understanding the Rules of Life Grant # 1839915 to BE Flammang, P Chakrabarty, and LM Page.
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