Posts Tagged ‘Fish’

A new University of Liverpool study has concluded that the anglers’ myth ‘that fish don’t feel pain’ can be dispelled: fish do indeed feel pain, with a similarity to that experienced by mammals including humans.

From hyper-ventilating and loss of appetite to long-term behavioural changes after a painful experience, the review by Dr Lynne Sneddon explores pain among fish and across the animal kingdom and explains its shared molecular foundations and the behaviours associated with avoiding and alleviating it.

Dr Lynne Sneddon, a biologist and one of the world’s leading experts on fish pain, said: “When subject to a potentially painful event fishes show adverse changes in behaviour such as suspension of feeding and reduced activity, which are prevented when a pain-relieving drug is provided.

“When the fish’s lips are given a painful stimulus they rub the mouth against the side of the tank much like we rub our toe when we stub it.

“If we accept fish experience pain, then this has important implications for how we treat them. Care should be taken when handling fish to avoid damaging their sensitive skin and they should be humanely caught and killed.”

The paper is published as part of ‘Evolution of mechanisms and behaviour important for pain’ – the latest theme issue of Philosophical Transactions of the Royal Society B that includes over a dozen articles on pain.

Research reference:

Sneddon Lynne U, Evolution of nociception and pain: evidence from fish models, 374, Phil. Trans. R. Soc. B, https://doi.org/10.1098/rstb.2019.0290

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By Michael Le Page

For many fish, changing sex is a normal part of life. For the first time, we have found out exactly how one of these species – a small cleaner fish called the bluehead wrasse – does it.

Erica Todd at the University of Otago in New Zealand and her colleagues removed some male bluehead wrasse from a few sites on reefs off Key Largo in Florida. This triggers females to change sex. They then caught changing females at regular intervals and looked at what was happening in their bodies down to the level of which genes were turning on or off.

They found that the loss of males makes some females stressed. They become more aggressive and start performing male courtship behaviours.

In individuals that become dominant in a social group, the genes associated with female hormones shut down in a day or two, and their colours begin to change – females of the species are yellow and brown (see above), while the males are green and blue.

At the same time, the egg-producing tissues in their ovaries start to shrink and begin to be replaced by sperm-producing tissues. In just 8 to 10 days, the mature ovaries are transformed into testes, and the fish can mate with females and sire offspring.

Read more: Zoologger: Shrimp plays chicken with its sex change
After around 20 days, the fish have the full male colours and the process is complete. “The bluehead is certainly remarkable for its speed,” says Todd. “Other species do take much longer.”

However, as the fish only live around two or three years, those 20 days are a fair chunk of their lifespan, equivalent to 2 years of a human lifetime.

Around 500 species of fish can change sex, a fact long known to biologists but which got wider attention recently when the Blue Planet II documentary narrated by David Attenborough showed Asian sheepshead wrasse changing sex. It is most common for female fish to turn into males but in some species including clownfish the males turn into females.

In at least one species, the hawkfish found around southern Japan, the females can not only turn into males but also turn back into females again if circumstances require it. For one species of shrimp, there is no need to change back. It starts out male but becomes an hermaphrodite – a phenomenon known as protandric simultaneous hermaphroditism.

Journal reference: Science Advances, DOI: 10.1126/sciadv.aaw7006

https://www.newscientist.com/article/2209254-bluehead-wrasse-fish-switch-from-female-to-male-in-just-20-days/

by MELISSA BREYER

If there’s a single way of eating that persists in laying claim as one of the healthiest, it’s the Mediterranean diet. Experts continue to sing the praises of eating plenty of olive oil, plant foods, fish and wine.

The latest research — following several years of headline-making studies — makes it hard to argue with them.

Following a Mediterranean diet can protect against the harmful effects of air pollution, according to a 2018 study conducted by New York University. The study analyzed about 550,000 people for 17 years and factored in their level of exposure to pollution. Those who followed the Mediterranean diet compared to those who didn’t had a lower risk of dying from cardiovascular disease and heart attacks.

“Air pollution is hypothesized to cause bad health effects through oxidative stress and inflammation, and the Mediterranean diet is really rich in foods that are anti-inflammatory and have antioxidants that might intervene through those avenues,” said study author Chris Lim on Time.com.

It’s worth noting that the diet doesn’t protect against ozone exposure. (Researchers believe that ozone exposure effects the cardiac system differently.)

Why the hits keep on coming

Researchers have been uncovering the benefits of this particular diet for years. In fact, the diet’s benefits for heart health were so clear in one 2013 study that researchers ended the study early, saying it was unethical to continue.

Research from 2014 added to the accolades. Scientists in Boston looked at the nutritional data from 4,676 women participating in the Harvard Nurses’ Health Study — the well-known ongoing prospective cohort analysis ­— and discovered that those whose food choices most closely followed a Mediterranean diet had longer telomeres. Telomeres are the protective buffers on the ends of chromosomes and can be used as a biomarker of aging; the longer they are, the better.

“We know that having shorter telomeres is associated with a lower life expectancy and a greater risk of cancer, heart disease and other diseases,” said study coauthor Immaculata De Vivo, an associate professor of medicine at Brigham and Women’s Hospital. “Certain lifestyle factors like obesity, sugary sodas, and smoking have been found to accelerate telomere shortening, and now our research suggests the Mediterranean diet can slow this shortening.”

The key is cell aging

The Mediterranean diet isn’t a specific diet plan per se, but rather eating in the traditional style of those living in Mediterranean countries. It’s characterized by consuming a lot of vegetables, fruits, nuts, legumes and unrefined grains. There is plenty of olive oil, but little saturated fat; a moderate intake of fish, but little dairy, meat and poultry. And while cookies and sugar are limited, a regular but moderate dose of wine is involved.

It’s thought that the antioxidants present in the favored foods protect against cell aging. While the researchers didn’t find that any specific food provided the silver bullet, they suggest that it was a combination of the components that predicted telomere length.

The researchers scored each woman’s diet according to how closely it adhered to Mediterranean components. What they found was that each one-point change in their grading system equated to an extra year and a half of life. A three-point change, the study notes, would correspond to an average 4.5 years of aging, which is comparable to the difference between smokers with non-smokers.

The researchers also concluded that women who may have veered slightly from the Mediterranean diet but who still ate a healthy diet — like eating chicken and low-fat dairy products in addition to the Mediterranean basics — also had longer telomeres than those who ate a standard American diet with red meat, saturated fats, sweets and empty calories. Those who followed the Mediterranean diet, however, had the longest telomeres on average.

https://www.mnn.com/food/healthy-eating/stories/mediterranean-diet-could-add-years-to-your-life


Small plastic fragments that have accumulated in the marine environment following decades of pollution can cause significant issues for marine organisms that ingest them, including inflammation, reduced feeding and weight-loss.

By Conn Hastings

A new study sheds light on the magnitude of microplastic pollution in our oceans. The study, published today in open-access journal Frontiers in Marine Science, found microplastics in the stomachs of nearly three out of every four mesopelagic fish caught in the Northwest Atlantic — one of the highest levels globally. These findings are worrying, as the affected fish could spread microplastics throughout the ocean. The fish are also prey for fish eaten by humans, meaning that microplastics could indirectly contaminate our food supply through the transfer of associated microplastic toxins.

“Microplastic pollution has been in the news recently, with several governments planning a ban on microbeads used in cosmetics and detergents,” says Alina Wieczorek from the National University of Ireland, Galway and lead author of the study. “The high ingestion rate of microplastics by mesopelagic fish that we observed has important consequences for the health of marine ecosystems and biogeochemical cycling in general.”

Microplastics are small plastic fragments that have accumulated in the marine environment following decades of pollution. These fragments can cause significant issues for marine organisms that ingest them, including inflammation, reduced feeding and weight-loss. Microplastic contamination may also spread from organism to organism when prey is eaten by predators. Since the fragments can bind to chemical pollutants, these associated toxins could accumulate in predator species.

Mesopelagic fish serve as a food source for a large variety of marine animals, including tuna, swordfish, dolphins, seals and sea birds. Typically living at depths of 200-1,000 meters, these fish swim to the surface at night to feed then return to deeper waters during the day. Through these vertical movements, mesopelagic fish play a key role in the cycling of carbon and nutrients from the surface to the deep sea — a process known as biogeochemical cycling. This means they could spread microplastic pollution throughout the marine ecosystem, by carrying microplastics from the surface down to deeper waters, affecting deep-sea organisms.

Despite their important role in marine ecosystems, mesopelagic fish have been relatively understudied in the context of microplastics. To investigate this further, Wieczorek and colleagues set out to catch fish in a remote area of the Northwest Atlantic Ocean: an eddy (whirlpool) off the coast of Newfoundland.

“These fish inhabit a remote area, so theoretically they should be pretty isolated from human influences, such as microplastics. However, as they regularly migrate to the surface, we thought that they may ingest microplastics there,” explains Wieczorek.

The researchers caught mesopelagic fish at varying depths, then examined their stomachs for microplastics back in the lab. They used a specialized air filter so as not to introduce airborne plastic fibers from the lab environment.

The team found a wide array of microplastics in the fish stomachs — with a whopping 73% of the fish having ingested the pollutants. “We recorded one of the highest frequencies of microplastics among fish species globally,” says Wieczorek. “In particular, we found high levels of plastic fibers such as those used in textiles.”

As the researchers were extremely careful to exclude contamination with fibers from the air, they are confident that the fish had ingested the fibers in the sea. Finding high levels of fibers in the fish is significant, as some studies investigating microplastics in fish have dismissed such fibers as contaminants from the lab environment, meaning their role as a pollutant may have been underestimated.

The researchers plan further studies to learn more about how these fish are ingesting and spreading microplastics. “It will be particularly interesting to see whether the fish ingest these microplastics directly as mistaken prey items, or whether they ingest them through eating prey species, which have previously ingested the microplastics,” says Wieczorek.

High levels of microplastics found in Northwest Atlantic fish


An Amazon molly, Poecilia formosa, an asexual fish species native to Texas that is entirely female.

By Shana Hutchin

Highlights

The Amazon molly has flourished by defying nature’s odds to reproduce asexually, cloning themselves by duping the male fish of another species to waste their germplasm

Females steal the entire genome of their host males, keep it for one generation and then throw it out again

The existence of Amazon mollies back anywhere from 100,000 to 200,000 years ago to a sexual reproduction event involving two different species of fish

Faculty Fellow Dr. Manfred Schartl led the international team that recently sequenced the first Amazon molly fish genome

No species is immune from the suffering of unrequited love, but scientists expect to learn volumes about the biological basis of sex from the newly sequenced genome of an all-female, asexual Texas native – the Amazon molly fish – that has thrived as a master of male manipulation over millennia.

The fresh waters along the Texas-Mexico border serve as home to this evolutionary anomaly – a fish that has flourished by defying nature’s odds to reproduce asexually through a natural form known as parthenogenesis in which growth and development of embryos occurs without fertilization, resulting only in daughters that are true clones of their mothers.

Texas A&M University Hagler Institute for Advanced Study (HIAS) Faculty Fellow Dr. Manfred Schartl led the international team that recently sequenced the first Amazon molly genome and the genomes of the original parental species that created this unique fish in an effort to better understand how its reproduction deviates from the male-female sexual norm and why the Amazon molly as a species has fared so well in the process.

The evolution of sex

The findings from their National Institutes of Health-funded research are published online today (Feb. 12) in the Nature research journal Nature Ecology & Evolution.

“The existence of two sexes, male and female, is one of the oldest and most widespread phenomena in biology,” says Schartl, a world leader in cellular and molecular biology of Xiphophorus model systems including platyfish and swordtails. “Studies on the exceptional case of asexuality helps us to better understand the biological meaning and evolution of sex.”

Animals that reproduce asexually are rare, compared to the overwhelming majority of species that exist as males and females and reproduce sexually. Because it was long thought that vertebrates would not be able to exist in such a way, Schartl says it was a sensation when the Amazon molly was the first asexual vertebrate discovered in 1932.

But even the most independent females occasionally need a male – in the Amazon molly’s case, to kick-start the parthenogenensis process. They seduce males from related sexual species for this service, which Schartl notes lacks the regular benefit for these males, which do not contribute their genes to the next generation.


An Amazon molly (right), caught in action while seducing a male Sailfin molly to steal sperm.

Thriving by cloning

“In essence, mollies repeatedly clone themselves by duping the male fish of another species to waste their germplasm,” Schartl says. “This reminds one of the tribe of female warriors in the Greek mythology, from which their name is derived.”

The team’s research traces the existence of Amazon mollies back anywhere from 100,000 to 200,000 years ago to a sexual reproduction event involving two different species of fish, an Atlantic molly and a Sailfin molly.

“That’s about 500,000 generations if you calculate it out to the present day, which makes them genetically older than humans,” Schartl says. “This is unexpected because asexuals are expected to be at disadvantage compared to their sexual counterparts.”

Schartl notes that one of the theories as to why asexual reproduction is incompatible with a species’ sustainability is the idea that if no new DNA is introduced during reproduction, then harmful gene mutations can accumulate over successive generations, leading to eventual extinction. Another hypothesis states that asexual reproduction is not like sexual reproduction, where the different genomes of the two parents are newly combined and create new genomes with every offspring. Because the absence of recombination in asexuals limits genetic diversity within a species, he says it gets more and more difficult to adapt to changes in the environment.

“Unexpectedly, we did not find the signs of genomic decay as predicted,” Schartl adds. “Our findings suggest that the molly’s thriving existence can be explained by the fact that the fish has a hardy genetic makeup that is often rare in nature and gives the animals some survival benefits.”

Schartl says the hybridization of the Atlantic and Sailfin mollies’ two different species genomes into a new one created a situation well known in the animal and plant breeding world — an artificial hybrid that is bigger, more colorful and capable of generating more and better products than the purebred parents, a phenomenon known as hybrid vigor.

https://today.tamu.edu/2018/02/12/texas-am-biologist-leads-international-team-that-sequences-first-amazon-molly-fish-genome/

A “faceless” deep-sea fish not seen for more than a century has been rediscovered by scientists trawling the depths of a massive abyss off Australia’s east coast, along with “amazing” quantities of rubbish.

The 40cm fish was rediscovered 4km below sea level in waters south of Sydney by scientists from Museums Victoria and the Australian government’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) on the weekend.

Dr Tim O’Hara, the chief scientist and expedition leader, who is a senior curator of marine invertebrates at Museums Victoria, said it was the first time the fish had been seen in waters off Australia since 1873, when one was dredged up by a British ship near Papua New Guinea.

“This little fish looks amazing because the mouth is actually situated at the bottom of the animal so, when you look side-on, you can’t see any eyes, you can’t see any nose or gills or mouth,” O’Hara said via satellite phone from the research vessel Investigator on Wednesday. “It looks like two rear-ends on a fish, really.”

The world-first survey of commonwealth marine reserves stretching from northern Tasmania to central Queensland began on 15 May. On board the Investigator research vessel for the month-long voyage are 27 scientists, 13 technicians and 20 crew.

Samples of animals and sediment have been collected from the bottom of the abyss each day by a metal sled-style device attached to 8km of thick wire. A video camera has also been trailed behind the ship to capture footage from the depths.

Finds have included bright red spiky rock crabs, spectacular bioluminescent sea stars and gigantic sea spiders as big as a dinner plate.

“The experts tell me that about a third of all specimens coming on board are new totally new to science,” O’Hara said. “They aren’t all as spectacular as the faceless fish but there’s a lot of sea fleas and worms and crabs and other things that are totally new and no one has seen them ever before.”

Di Bray of Museums Victoria told the ABC that the rediscovery of the faceless fish was a highlight of the “awesome stuff” thrown up by the study so far.

“On the video camera we saw a kind of chimaera that whizzed by – that’s very, very rare in Australian waters,” she said. “We’ve seen a fish with photosensitive plates that sit on the top of its head, tripod fish that sit up on their fins and face into the current.”

“A lot” of the species found would prove to be previously undiscovered, she predicted.

“We’re not even scratching the surface of what we know about our abyssal plain fishes.”

Equally “amazing”, O’Hara said, was the quantity of rubbish that researchers had dredged up.

“There’s a lot of debris, even from the old steam ship days when coal was tossed overboard,” he said. “We’ve seen PVC pipes and we’ve trawled up cans of paints.

“It’s quite amazing. We’re in the middle of nowhere and still the sea floor has 200 years of rubbish on it.”

In February, scientists reported “extraordinary” levels of toxic pollution in the 10km-deep Mariana trench, one of the most remote and inaccessible places on the planet.

Data from the survey of the eastern abyss would allow scientists to collect baseline data about its biodiversity and would likely be used to measure the impacts of climate change in the coming decades.

The research voyage is due to conclude on 16 June.

https://www.theguardian.com/environment/2017/may/31/faceless-fish-missing-for-more-than-a-century-rediscovered-by-australian-scientists

Federal biologist Jay Orr never knows what’s going to come up in nets lowered to the ocean floor off Alaska’s remote Aleutian Islands, which separate the Bering Sea from the rest of the Pacific Ocean. Sometimes it’s stuff he has to name.

The National Oceanic and Atmospheric Administration biologist is part of a group that uses trawl nets to survey commercially important fish species such as cod in waters off Alaska. Sometimes those nets come up with things no one has seen before.

With co-authors, Orr has discovered 14 kinds of new snailfish, a creature that can be found in tide pools but also in the deepest parts of the ocean. A dozen more new snailfish are waiting to be named. Additional species are likely to be found as scientists expand their time investigating areas such as the Bering Sea Slope, in water 800 to 5,200 feet deep, or the 25,663-foot deep Aleutian Trench.

“I suspect we are just scraping the top of the distributions of some of these deep-water groups,” Orr said from his office in Seattle.

Orr and his colleagues measure the abundance of rockfish, flatfish and other “bottom fish” for the Alaska Fisheries Science Center, the research arm of the NOAA’s National Marine Fisheries Service. The center studies marine resources off Alaska and parts of the West Coast.

Five boats with six researchers each surveyed Alaska waters in late June. The teams trawl on the Bering Shelf every summer and in either Aleutian waters or the Gulf of Alaska every other year.

Their findings on fish abundance are fed into models for managing fish populations.

The scientists put down a 131-foot trawl net that captures whatever is along the ocean bottom. A ton of fish is a standard sample. Along with fish, they get clues to the seafloor habitat. Sponges, for example, indicate a hard seafloor, or substrate.

Fifteen years ago, research biologist Michael Martin suggested a small modification: a net just 2 to 3 feet wide at the front of the trawl net.

“We realized we didn’t have a really good picture of the substrate that we were trawling over, and we figured we were missing some things in the big meshes that the larger net had,” Orr said. “So one of the other guys here decided to put this little net on, mainly as a means to see what the substrate looked like.”

On one of the first hauls, the small net returned with a variety of small, soft-bodied fish, including snailfish, that likely would have fallen out or gotten mashed in the main net. Orr took a look and knew they had found something different.

As someone who studies fish, “I sort of knew what I was looking for and what was known out there,” he said. “The first ones that came up, I saw them right away and said, ‘We don’t know what these are. These haven’t been named.'”

Snailfish have no scales, feel gelatinous and look like fat tadpoles. Aristotle described a Mediteranean variety found in ancient Greece as “sea slugs.”

Many fish have pelvic fins on their bellies, just behind the gills. Most snailfish species, instead of pelvic fins, have a sucking disc that they use to cling to rocks.

Orr identified some new varieties that did not have a sucking disc. Another had a hardened bone in its head. Another had a projecting lower jaw. Others varied by shape, color or body parts, such as vertebrae.

“Nearly all of them have genetic characters that distinguish them, too,” Orr said.

He has wide latitude for giving new species both common and Latin names. A red, white and black snailfish with a big, bulbous nose struck him as funny-looking. He gave it the common name of “comic snailfish” and the Latin name Careproctus comus, after Comus, the god of comedy in Greek mythology.

Snailfish made headlines in 2014 when researchers recorded them swimming nearly 27,000 feet, or more than 4 miles, below the surface in the Marianas Trench, making them the deepest-dwelling vertebrate on the planet. The Marianas Trench is about 200 miles southwest of the Pacific island of Guam and is known as the deepest part of the world’s oceans.

A critical part of the work is on the species his agency actively manages. Orr helped distinguish the northern rock sole, which spawns and grows differently than other rock sole. Fishing at the wrong time could disrupt a population important to the seafood market.

“Ultimately we’re managing an ecosystem,” Orr said. “It’s really important to know what each of the elements are.”

http://bigstory.ap.org/6f677b05f94b4031b82b1c41aaab835b