Showing posts with label Marine Biology. Show all posts
Showing posts with label Marine Biology. Show all posts

Wednesday, September 28, 2022

How fish survive the extreme pressures of life in the oceans

Photo credit: Milos Prelevic

Scientists have discovered how a chemical in the cells of marine organisms enables them to survive the high pressures found in the deep oceans.

The deeper that sea creatures live, the more inhospitable and extreme the environment they must cope with. In one of the deepest points in the Pacific - the Mariana Trench, 11 kilometers below the sea surface - the pressure is 1.1 kbar or eight tons per square inch. That is a 1,100-fold increase of the pressure experienced at the Earth’s surface.

Under normal or atmospheric pressure, water molecules form a tetrahedron-like network. At high pressure, though, the network of water molecules begins to distort and change shape. When this happens to the water inside living cells, it prevents vital bio-chemical processes from taking place - and kills the organism.

Our study provides a bridge between water under pressure at the molecular level and the wonderful ability of organisms which thrive under high pressure in depths of the oceans.

In reporting their findings, the researchers in Leeds have for the first time been able to provide an explanation of how a molecule found in the cells of marine organisms counteracts the effect of external pressure on the water molecules.

Tuesday, September 20, 2022

Octopuses prefer certain arms when hunting and adjust tactics to prey

A California two-spot octopus hunts a shrimp in an experiment, striking with its second arm.
Credit: Wardill Lab, University of Minnesota

Famous for their eight arms, octopuses leverage all of their appendages to move, jet through the water and capture prey. But their movements can look awkward and seemingly unplanned at times, more closely resembling aliens than earthly creatures.

“Normally when you look at an octopus for a short while, nothing is repeatable. They squirm around and just look weird in their exploratory movements,” said Trevor Wardill, an assistant professor in the College of Biological Sciences who studies octopuses and other cephalopods.

For a new study in Current Biology, Wardill and colleagues investigated whether octopuses preferred certain arms over others when hunting, rather than using each arm equally. A better understanding of how they use their arms will aid efforts to develop next-generation, highly-manipulative soft robots.

The research team studied the California two-spot octopus, which live for about two years and grow to the size of tennis balls. Octopus arms are numbered on each side of its body, starting at the center. Researchers dropped different types of prey, including crabs and shrimp, into the tanks and recorded video as the octopuses, who were hiding in ornamental SpongeBob “dens” with one eye facing outward, lunged for the snack. Because crabs move slowly while shrimp can flick their tails to escape quickly, each type of prey potentially requires different hunting tactics.

Saturday, September 17, 2022

In the sea anemone, the way you move matters

Sea anemones, it turns out, also benefit from maintaining an active lifestyle, particularly as they grow from ovoid-shaped swimming larvae to sedentary, tubular polyps. The tissue is visualized using actin-staining.
Credit: Ikmi group/EMBL and ALMF/EMBL

Researchers from EMBL’s Ikmi group employed an interdisciplinary approach to show how sea anemone ‘exercise’ changes their developing size and shape, uncovering an intimate relationship between behavior and body development.

As humans, we know that an active lifestyle gives us some control over our form. When we hit the pavement, track our steps, and head to the gym, we can develop muscle and reduce body fat. Our physical activity helps shape our physical figure. But what if we performed similar aerobics in our earliest forms?

Researchers at EMBL’s Ikmi group turned this question towards the sea anemone to understand how behavior impacts body shape during early development. Sea anemones, it turns out, also benefit from maintaining an active lifestyle, particularly as they grow from egg-shaped swimming larvae to sedentary, tubular polyps. This morphological transformation is a fundamental transition in the life history of many cnidarian species, including the immortal jellyfish and corals, the builders of our planet’s richest and most complex ecosystems.

During development, starlet sea anemone larvae (Nematostella) perform a specific pattern of gymnastic movements. Too much or too little muscle activity or a drastic change in the organization of their muscles can cause the sea anemone to deviate from its normal shape.

Wednesday, September 14, 2022

Researchers Discover First Pair of Mated Blue Crabs in Great Bay

UNH doctoral student Kelsey Meyer with large male blue crab in Great Bay Estuary.
Courtesy photo University of New Hampshire

Researchers at the University of New Hampshire have documented the first discovery of a pair of recently mated blue crabs in Great Bay Estuary (GBE), a finding that is expected to have serious impacts on the estuary’s ecosystem, particularly its fragile oyster population. Blue crabs have been captured in GBE since 2012 but this is the first-time researchers have found compelling evidence that the crabs are actually mating.

“The arrival of blue crabs capable of creating a sustained population poses a new threat to oysters and other native GBE species,” said Bonnie Brown, professor, and chair of the department of biological sciences.

Doctoral student Alyssa Stasse and technician Emily Williams were checking traps set out by doctoral student Kelsey Meyer, who is monitoring the estuary’s invasive green crab population, when they found the two blue crabs and the mating proof: the female, which had recently molted, had distended turgid seminal receptacles with large sperm plugs, clear evidence of crustacean copulation.

Thursday, September 1, 2022

Corals pass mutations acquired during their lifetimes to offspring

The Elkhorn coral, Acropora palmata, grows into large stands via polyp budding and fragmentation so that many colonies belong to the same clone or genet. During growth, mutations can accumulate in its cells and new research shows that the Ekhorn coral is able to pass these mutations onto to their sexual offspring. This is unlike most animals that prevent such a transfer from the body to reproductive cells.
 Credit: Ilian Baums / Penn State. Creative Commons

In a discovery that challenges over a century of evolutionary conventional wisdom, corals have been shown to pass somatic mutations — changes to the DNA sequence that occur in non-reproductive cells — to their offspring. The finding, by an international team of scientists led by Penn State biologists, demonstrates a potential new route for the generation of genetic diversity, which is the raw material for evolutionary adaptation, and could be vital for allowing endangered corals to adapt to rapidly changing environmental conditions.

“For a trait, such as growth rate, to evolve, the genetic basis of that trait must be passed from generation to generation,” said Iliana Baums, professor of biology at Penn State and leader of the research team. “For most animals, a new genetic mutation can only contribute to evolutionary change if it occurs in a germline or reproductive cell, for example in an egg or sperm cell. Mutations that occur in the rest of the body, in the somatic cells, were thought to be evolutionarily irrelevant because they do not get passed on to offspring. However, corals appear to have a way around this barrier that seems to allow them to break this evolutionary rule.”

Since the time of Darwin, our understanding of evolution has become ever more detailed. We now know that an organism’s traits are heavily determined by the sequence of their DNA. Individuals in a population vary in their DNA sequence, and this genetic variation can lead to the variation in traits, such as body size, that could give an individual a reproductive advantage. Only rarely does a new genetic mutation occur that gives an individual such a reproductive advantage and evolution can only proceed further if — and this is the key — the individual can pass the change to its offspring.

Global fish stocks can’t rebuild if nothing is done to halt climate change and overfishing

Photo by Hiroko Yoshii on Unsplash

Global fish stocks will not be able to recover to sustainable levels without strong actions to mitigate climate change, a new study has projected.

Researchers at UBC, the Stanford Center for Ocean Solutions and University of Bern projected the impact that different global temperature increases and ranges of fishing activity would have on biomass, or the amount of fish by weight in a given area, from 1950 to 2100. Their simulations suggest that climate change has reduced fish stocks in 103 of 226 marine regions studied, including Canada, from their historical levels. These stocks will struggle to rebuild their numbers under projected global warming levels in the 21st century.

“More conservation-oriented fisheries management is essential to rebuild over-exploited fish stocks under climate change. However, that alone is not enough,” says lead author Dr. William Cheung, professor in the Institute for the Oceans and Fisheries (IOF). “Climate mitigation is important for our fish stock rebuilding plans to be effective”

The research team, including co- author Dr. Colette Wabnitz of Stanford Centre for Ocean Solutions, used computer models to find out the climate change levels at which over-exploited fish stocks cannot rebuild. Currently, the world is on track to exceed 1.5 degrees of warming relative to preindustrial levels and approach two degrees in the next few decades, says Dr. Cheung.

Tuesday, August 23, 2022

Study finds that ocean cooling over millennia led to larger fish

Dahiana Arcila in Reykjavík, Iceland. Arcila is the recipient of a National Science Foundation CAREER award to study the evolutionary history of marine fish.
Source: University of Oklahoma

Earth’s geological history is characterized by many dynamic climate shifts that are often associated with large changes in temperature. These environmental shifts can lead to trait changes, such as body size, that can be directly observed using the fossil record.

To investigate whether temperature shifts that occurred before direct measurements were recorded, called paleoclimatology, are correlated with body size changes, several members of the University of Oklahoma’s Fish Evolution Lab decided to test their hypothesis using tetraodontiform fishes as a model group. Tetradontiform fishes are primarily tropical marine fishes, and include pufferfish, boxfishes and filefish.

The study was led by Dahiana Arcila, assistant professor of biology and assistant curator at the Sam Noble Oklahoma Museum of Natural History, with Ricardo Betancur, assistant professor of biology, along with biology graduate student Emily Troyer, and involved collaborators from the Smithsonian Institution, University of Chicago and George Washington University in the United States, as well as the University of Turin in Italy, University of Lyon in France and CSIRO Australia.

The researchers discovered that the body sizes of these fishes have grown larger over the past hundred million years in conjunction with the gradual cooling of ocean temperatures.

Wednesday, August 17, 2022

Sleeping giant could end deep ocean life

Resting balloonfish near the Florida Keys.
Credit: (OAR/National Undersea Research Program (NURP); University of Maine)

A previously overlooked factor — the position of continents — helps fill Earth’s oceans with life-supporting oxygen. Continental movement could ultimately have the opposite effect, killing most deep ocean creatures.

“Continental drift seems so slow, like nothing drastic could come from it, but when the ocean is primed, even a seemingly tiny event could trigger the widespread death of marine life,” said Andy Ridgwell, UC Riverside geologist and co-author of a new study on forces affecting oceanic oxygen.

The water at the ocean’s surface becomes colder and denser as it approaches the north or south pole, then sinks. As the water sinks, it transports oxygen pulled from Earth’s atmosphere down to the ocean floor.

Eventually, a return flow brings nutrients released from sunken organic matter back to the ocean’s surface, where it fuels the growth of plankton. Both the uninterrupted supply of oxygen to lower depths and organic matter produced at the surface support an incredible diversity of fish and other animals in today’s ocean.

New findings led by researchers based at UC Riverside have found this circulation of oxygen and nutrients can end quite suddenly. Using complex computer models, the researchers investigated whether the locations of continental plates affect how the ocean moves oxygen around. To their surprise, it does.

Tuesday, August 16, 2022

UF research shows a step toward restoring sea urchins: ‘The lawnmowers of reefs’

Sea urchin
Credit: Josh Patterson 

Coral reef ecosystems are severely threatened by pollution, disease, overharvesting and other factors. For thousands of years, long-spined sea urchins helped keep reefs intact. They eat seaweed, which can kill or seriously damage coral. Without coral, reefs suffer severe consequences, including diminished ability to support fish.

In the mid-1980s, more than 90% of the urchins that crawled the coral reefs in the western Atlantic and Caribbean died for reasons scientists have yet to determine. The population of the long-spined sea urchin – known scientifically as Diadema antillarum -- has been slow to recover on its own. That’s why scientists, including Josh Patterson, are stepping up their efforts to enhance urchin populations.

“You could call these urchins the lawn mowers of the reefs,” said Patterson, a UF/IFAS associate professor of fisheries and aquatic sciences. “They eat fleshy seaweeds that grow out of control on coral reefs and ultimately smother the corals.”

The UF/IFAS restoration ecologist is trying to return more of the urchin to an area that roughly includes the seas off the Florida Keys, Bermuda, the Yucatan Peninsula, Aruba and the Virgin Islands. He’s taken a small step toward the overarching goal of revitalizing the population of the vital echinoderm.

Extreme events stress the oceans

Sea snails - the picture shows a pteropod - play an important role in the marine food web. They are especially sensitive to ocean warming and acidification.
Source: Universität Bern Credit: Charlotte Havermans

When marine heatwaves and ocean acidity extreme events co-occur, it can have severe impacts on marine ecosystems. Researchers at the Oeschger Center for Climate Change Research at the University of Bern have determined for the first time the frequency and drivers of these compound events and have projected them into the future.

It's not just the land that is groaning under the heat – the ocean is also suffering from heatwaves. In the Mediterranean Sea along the Italian and Spanish coasts, for example, water temperatures are currently up to 5 °C higher than the long-term average at this time of year. Scientists have investigated marine heatwaves for a few years now – for example at the University of Bern. However, relatively little is known about how marine heatwaves co-occur with other extreme events in the ocean. Such events are known as compound events and considered to be a major risk of climate change. While the processes that lead to extreme events on land, such as floods, forest fires, heatwaves, or droughts and how they interact with each other have been intensively studied in the past, the finding that ocean weather and climate extreme events can also occur in combination is relatively new.

A group of researchers at the Oeschger Center for Climate Change Research, led by Thomas Frölicher, has now investigated whether marine heatwaves co-occur in combination with extreme events in other potential marine ecosystem stressors. In addition to heat, potential stressors also include high acidity levels in the ocean. "For the first time, we have quantified the frequency of compound events in which marine heatwaves happen together with extreme acidity", says Friedrich Burger, postdoctoral researcher and first author of the study just published in the journal Nature Communications. Extreme events of high ocean acidity are occurrences where the proton concentration in seawater is higher than normal.

Sunday, August 7, 2022

Researchers unveil key processes in marine microbial evolution

Microbial eukaryotes have made hundreds of great leaps from sea to land, which would explain today's great biodiversity
Credit: Albert Reñé.

An international study in which the ICM-CSIC has participated has reconstructed the evolutionary history of microbial diversity over the last 2,000 million years.

A study published recently in the prestigious journal Nature Ecology and Evolution has unveiled some of the key processes in marine microbial evolution. According to the study, led by the Uppsala University (Sweden) and with the participation of the Institut de Ciències del Mar (ICM-CSIC) of Barcelona, it is the large number of habitat transitions -from sea to land and vice versa- that have occurred in the last millions of years that explains the great current diversity.

According to the authors, "crossing the salinity barrier is not easy for organisms and, when this happens, the resulting transitions are key evolutionary events that can trigger explosions of diversity". However, until now it was not known how frequent these transitions have been in the eukaryotic tree of life, which comprises animals, plants and a wide variety of eukaryotic microorganisms.

Small but very versatile

Specifically, the work published now has shown that microbial eukaryotes have made hundreds of great leaps from sea to land, and also to freshwater habitats, and vice versa, during their evolution. This, in turn, has made it possible to deduce where the ancestors of each of the microbial eukaryote groups were found.

"Thanks to the fact that we have good phylogenetic trees and samples from different environments, we have been able to analyze the habitat transitions in different groups of eukaryotes, which have been hundreds of times during millions of years of eukaryotic evolution, which is more than we thought," explains Ramon Massana, ICM-CSIC researcher and one of the authors of the study.

Wednesday, July 27, 2022

Hot on the trail of the causes of rapid ice sheet in­stabil­it­ies in cli­mate his­tory

The re­search ves­sel MARIA S. MERIAN leav­ing the har­bor of St. John’s (Canada). As a par­ti­cipant on Ex­ped­i­tion MSM 39 (2014), Lars Max, along with other re­search­ers, ob­tained the sample ma­ter­ial for this study.
Credit: MARUM – Cen­ter for Mar­ine En­vir­on­mental Sci­ences, Uni­versity of Bre­men; D. Kieke

Extreme cooling events during the last glacial, known as Heinrich Events in the North Atlantic, are a good example of how local processes change the global climate. While the impacts of Heinrich Events on the global glacial environment are well-documented in the scientific literature, their causes are still unclear. In a new study, researchers from Bremen, Kiel, Köln and São Paulo (Brazil) have now shown that an accumulation of heat in the deeper Labrador Sea caused instabilities in the Laurentide Ice Sheet, which covered much of North America at the time. The Heinrich Events were triggered as a result. The researchers demonstrated this by reconstructing past temperatures and salinities in the North Atlantic. Their results have now been published in Nature Communications.

Hein­rich Events or, more ac­cur­ately, Hein­rich Lay­ers, are re­cur­rent con­spicu­ous sed­i­ment lay­ers, usu­ally ten to 15 cen­ti­meters thick, with very coarse rock com­pon­ents that in­ter­rupt the oth­er­wise fine-grained oceanic de­pos­its in the North At­lantic. Dis­covered and de­scribed for the first time in the 1980s by geo­lo­gist Hart­mut Hein­rich, U.S. geo­chem­ist Wally Broecker later of­fi­cially named them Hein­rich Lay­ers, which has be­come a stand­ard term in pa­leocean­o­graphy.

The pres­ence of Hein­rich Lay­ers has been es­tab­lished throughout the North At­lantic, from off Ice­land, south­ward to a line run­ning from New York to North Africa. Such coarse rock debris could only have been trans­por­ted such a great dis­tance from its point of ori­gin in the Hud­son Bay by ice­bergs.

Sunday, July 3, 2022

Humpback whales may steer clear of Hawaiʻi due to climate change

Humpback whale
Photo by Joshua Sukoff on Unsplash

Humpback whales may one day avoid Hawaiian waters due to climate change and rising greenhouse gasses, according the findings of a new paper published in Frontiers in Marine Science by a team of researchers including three University of Hawaiʻi at Mānoa graduate students—Hannah von Hammerstein and Renee Setter from the Department of Geography and Environment in the College of Social Sciences, and Martin van Aswegen from the Marine Mammal Research Program in the Institute for Marine Biology.

Humpback whales are known to migrate toward tropical coastal waters, such as Hawaiʻi’s, where they give birth to their calves. These areas lay in regions with sea surface temperatures ranging between 21 and 28 degrees Celsius (approximately 70–82 degrees Fahrenheit), and the whales typically return to the same sites annually.

According to von Hammerstein, Setter, van Aswegen and co-researchers from the Pacific Whale Foundation, anthropogenic climate change is warming the oceans at unprecedented rates. At the current pace, it is likely that some of these breeding grounds will heat up past the 21–28℃ temperature range over the next century.

Tuesday, June 28, 2022

How did vertebrates first evolve jaws?

A zebrafish showing the skeleton and jaw (magenta), the eye (green circle on the left), and gill-like pseudobranch and gills (green structures on the right).
Image resized using AI by SFLORG
Credit: Mathi Thiruppathy/Crump Lab

Five-hundred million years ago, it was relatively safe to go back in the water. That’s because creatures of the deep had not yet evolved jaws. In a new pair of studies in the journals eLife and Development, scientists reveal clues about the origin of this thrilling evolutionary innovation in vertebrates.

In the studies, Mathi Thiruppathy from Gage Crump’s laboratory at USC, and collaborator J. Andrew Gillis from the University of Cambridge and the Marine Biological Laboratory, looked to embryonic development as way to gain insight into evolution—an approach known as “evo-devo.”

In fishes, jaws share a common developmental origin with gills. During development, jaws and gills both arise from embryonic structures called “pharyngeal arches.” The first of these arches is called the mandibular arch because it gives rise to jaws, while additional arches develop into gills. There are also anatomical similarities: the gills are supported by upper and lower bones, which could be thought of as analogous to the upper and lower jaws.

“These developmental and anatomical observations led to the theory that the jaw evolved by modification of an ancestral gill,” said Thiruppathy, who is the eLife study’s first author and a PhD student in the Crump Lab. “While this theory has been around since the late 1800s, it remains controversial to this day.”

Thursday, June 23, 2022

Climate change could lead to a dramatic temperature-linked decrease in essential omega-3 fatty acids

MIT-WHOI Joint Program student Henry Holm pumping seawater for lipid samples from beneath sea ice on the Western Antarctic Peninsula, 2018. This is for a WHOI-led study that conducted a global survey of lipids in the ocean in order to analyze omega-3 fatty acids.
Image credit: Benjamin Van Mooy / © Woods Hole Oceanographic Institution

The effects of global climate change already are resulting in the loss of sea ice, accelerated sea level rise, and longer and more intense heat waves, among other threats.

Now, the first-ever survey of planktonic lipids in the global ocean predicts a temperature-linked decrease in the production of essential omega-3 fatty acids, an important subset of lipid molecules.

A significant implication of the survey is that as global warming proceeds, there will be fewer and fewer omega-3 fatty acids produced by plankton at the base of the food web, which will mean less omega-3 fatty acids available for fish and for people. Omega-3 fatty acid is an essential fat that the human body cannot produce on its own, and is widely regarded as a “good” fat that links seafood consumption to heart health.

The survey analyzed 930 lipid samples across the global ocean using a uniform high-resolution accurate mass spectrometry analytical workflow, “revealing heretofore unknown characteristics of ocean planktonic lipidomes,” which is the entirety of hundreds to thousands of lipid species in a sample, according to a new paper led by authors from the Woods Hole Oceanographic Institution (WHOI).

“Focusing on ten molecularly diverse glycerolipid classes we identified 1,151 distinct lipid species, finding that fatty acid unsaturation (i.e., number of carbon-to-carbon double bonds) is fundamentally constrained by temperature. We predict significant declines in the essential fatty acid eicosapentaenoic acid [EPA] over the next century, which are likely to have serious deleterious effects on economically critical fisheries,” states the paper, “Global ocean lipidomes show a universal relationship between temperature and lipid unsaturation,” published in the journal Science.

Tuesday, June 14, 2022

Right Whales’ Survival Rates Plummet After Severe Injury from Fishing Gear

Source: Duke University

Most North Atlantic right whales that are severely injured in fishing gear entanglements die within three years, a new study led by scientists at the New England Aquarium and Duke University finds.

North Atlantic right whales are a critically endangered species whose population has shrunk in recent decades. Scientists estimate fewer than 350 of the iconic whales are still alive in the wild today.

To examine the role fishing gear entanglements have played in the species’ decline, the researchers tracked the outcomes of 1,196 entanglements involving 573 right whales between 1980 and 2011 and categorized each run-in based on the severity of the injury incurred

The data revealed that male and female right whales with severe injuries were eight times more likely to die than males with minor injuries, and only 44% of males and 33% of females with severe injuries survived longer than 36 months.

Females that did survive had much lower birth rates and longer intervals between calving, a worrisome trend for the long-term survival of the species.

Sunday, June 12, 2022

Ningaloo corals are ill-equipped to handle future climate change

Source: Curtin University

The relatively pristine coral populations of WA’s inshore Kimberley region are better equipped to survive ocean warming than the World Heritage-listed Ningaloo Marine Park, according to a new Curtin University study.

Despite previous research predicting coral species would move south to cooler waters to protect themselves, the new study – published in Molecular Ecology – has found this may not hold true on the West Coast of Australia.

The new study, which investigated coral population connectivity and adaptive capacity, has found corals growing in different reef systems in north-western Australia are genetically isolated from each other.

The findings were based on the genetic data of a reef-building coral, Acropora digitifera, sampled from five well-known reef systems. The study sought to find out how connected these reef systems are, and how resilient this coral is to different future climate scenarios in different regions.

Lead researcher PhD student Arne Adam, from the Curtin School of Molecular and Life Sciences, said climate change had caused widespread loss of species biodiversity and ecosystem productivity across the globe, particularly on tropical coral reefs. He said the results suggest corals from northern reefs in WA are isolated from each other, meaning that corals may not be able to move to more southern reef regions.

Thursday, June 2, 2022

Research Shows How Gulf of Mexico Escaped Ancient Mass Extinction

The Mississippi River flowing into the Gulf of Mexico. According to researchers at the University of Texas Institute for Geophysics, river sediments and ocean currents helped simple sea life in the Gulf survive a deep-ocean mass extinction 56 million years ago.
Credit: U.S. Geological Survey

An ancient bout of global warming 56 million years ago that acidified oceans and wiped-out marine life had a milder effect in the Gulf of Mexico, where life was sheltered by the basin’s unique geology – according to research by the University of Texas Institute for Geophysics (UTIG).

Published in the journal Marine and Petroleum Geology, the findings not only shed light on an ancient mass extinction, but could also help scientists determine how current climate change will affect marine life and aid in efforts to find deposits of oil and gas.

And although the Gulf of Mexico is very different today, UTIG geochemist Bob Cunningham, who led the research, said that valuable lessons can be drawn about climate change today from how the Gulf was impacted in the past.

“This event known as the Paleocene-Eocene Thermal Maximum or PETM is very important to understand because it’s pointing towards a very powerful, albeit brief, injection of carbon into the atmosphere that’s akin to what’s happening now,” he said.

Cunningham and his collaborators investigated the ancient period of global warming and its impact on marine life and chemistry by studying a group of mud, sand, and limestone deposits found across the Gulf.

Wednesday, June 1, 2022

How Electric Fish Were Able to Evolve Electric Organs

UT Austin researchers confirmed that the genetic control region they discovered only controls the expression of a sodium channel gene in muscle and no other tissues. In this image, a green fluorescent protein lights up only in trunk muscle in a developing zebrafish embryo.
Image credit: Mary Swartz/Johann Eberhart/University of Texas at Austin.

Electric organs help electric fish, such as the electric eel, do all sorts of amazing things: They send and receive signals that are akin to bird songs, helping them to recognize other electric fish by species, sex and even individual. A new study in Science Advances explains how small genetic changes enabled electric fish to evolve electric organs. The finding might also help scientists pinpoint the genetic mutations behind some human diseases.

Evolution took advantage of a quirk of fish genetics to develop electric organs. All fish have duplicate versions of the same gene that produces tiny muscle motors, called sodium channels. To evolve electric organs, electric fish turned off one duplicate of the sodium channel gene in muscles and turned it on in other cells. The tiny motors that typically make muscles contract were repurposed to generate electric signals, and voila! A new organ with some astonishing capabilities was born.

“This is exciting because we can see how a small change in the gene can completely change where it’s expressed,” said Harold Zakon, professor of neuroscience and integrative biology at The University of Texas at Austin and corresponding author of the study.

In the new paper, researchers from UT Austin and Michigan State University describe discovering a short section of this sodium channel gene—about 20 letters long—that controls whether the gene is expressed in any given cell. They confirmed that in electric fish, this control region is either altered or entirely missing. And that’s why one of the two sodium channel genes is turned off in the muscles of electric fish. But the implications go far beyond the evolution of electric fish.

Cuttlefish: Chameleons of the sea

European cuttlefish
Source: City, University of London

Study suggests that European cuttlefish use a more complex strategy than previously thought to camouflage themselves within underwater surroundings.

A new study by City, University of London and others suggests that the European cuttlefish (sepia officinalis) may combine, as necessary, two distinct neural systems that process specific visual features from its local environment, and visual cues relating to its overall background environment to create the body patterns it uses to camouflage itself on the sea floor.

This is in contrast to previous research suggesting that the cognitive (brain) processes involved are much simpler, in that the cuttlefish adopts one of only three major types of body patterns to visually merge with its background. However, that does not explain why the animal possesses about 30 different body pattern components it could use to achieve this.

The study explored whether the cuttlefish uses a cognitive process that is triggered by specific, visual features in its environment and which warrants the number of body pattern components it possesses.

Like their cephalopod relatives the octopus and the squid, cuttlefish are masters at blending in with their environments, which is largely attributable to the way their brains are able to control how pigments in special cells called chromatophores on their skin are displayed across their bodies.

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