Fish eggs survive being eaten by ducks


This 2009 video is called Mallard Duck – HD Mini-Documentary.

By Carolyn Wilke today:

Fish eggs can hatch after being eaten and pooped out by ducks

In the lab, only a few carp eggs survived the dangerous trip through birds’ innards

For fish eggs, getting gobbled by a duck kicks off a harrowing journey that includes a pummeling in the gizzard and an attack by stomach acids. But a few eggs can exit unscathed in a duck’s excrement, possibly helping to spread those fish, including invasive species, to different places, a new study finds.

It’s been an “open question for centuries how these isolated water bodies can be populated by fish,” says fish biologist Patricia Burkhardt-Holm of the University of Basel in Switzerland, who was not involved with the work. This study shows one way that water birds may disperse fish, she says.

Birds’ feathers, feet and feces can spread hardy plant seeds and invertebrates (SN: 1/14/16). But since many fish eggs are soft, researchers didn’t expect that they could survive a bird’s gut, says Orsolya Vincze, an evolutionary biologist at the Centre for Ecological Research in Debrecen, Hungary.

In the lab, Vincze and her colleagues fed thousands of eggs from two invasive carp species to eight mallard ducks. About 0.2 percent of ingested eggs, 18 of 8,000, were intact after defecation, the team found. Some of those eggs contained wriggling embryos and a few eggs hatched, the team reports June 22 in the Proceedings of the National Academy of Sciences. It’s not clear yet whether eggs survive in this way in the wild.

Most of the viable eggs were pooped out within an hour of being eaten, while one took at least four hours to pass. Migratory ducks could travel dozens or possibly hundreds of kilometers before excreting those eggs, the scientists suggest.

Though the surviving egg count is low, their numbers may add up, making bird poop a possibly important vehicle for spreading fish. A single carp can release hundreds of thousands of eggs at a time, Vincze says. And there are huge numbers of mallards and other water birds throughout the world that may gorge themselves on those eggs.

Mallards usually eat plants. They have trouble eating meat, even an ‘easy’ small dead fish, as I have seen.

Finnish salmon sex life, new research


This video from Finland is called Small salmon in Teno river (Kuusiniemenväylä) 2016.

From the University of Helsinki in Finland:

Size matters in the sex life of salmon

June 23, 2020

Summary: For Atlantic salmon, size matters when it comes to love. Larger males and females that may spend up to four years at sea produce many more babies, but they are very rare compared to younger fish.

Every summer, tens of thousands of Atlantic salmon migrate from the Barents Sea to the Teno River, Finland, to spawn in the streams where they were born. This journey is a feat of endurance: salmon stop feeding and must navigate fast-flowing water, leap over obstacles, and avoid predators, hooks, and fishing nets to arrive at their spawning grounds.

The marathon doesn’t stop there though: once they arrive at their spawning grounds, they must fight for the possibility to mate with members of the opposite sex. Who are the winners of this evolutionary competition? It turns out that the largest fish produce the most offspring, but there are far fewer of these fish on the spawning ground battling for reproductive success than their younger — and smaller — competitors, according to researchers at the University of Helsinki and the Natural Resources Institute Finland.

The study, recently published in the scientific journal Molecular Ecology, is part of a long-term monitoring program. A small piece of fin tissue was removed for genetic fingerprinting of more than 5000 adults and juveniles before they were released back into the wild. Adults were also fitted with a unique identification tag after a few scales were carefully sampled. The scales are particularly valuable, as they record annual growth cycles, much like tree rings.

“Great care was taken to not harm the fish,” explains Dr. Kenyon Mobley, lead author of the article. “In fact, we have recaptured adults returning to spawn several years later and juveniles returning to spawn as adults.”

Larger salmon have more offspring

Most salmon in Teno River spend between one and four years at sea before migrating back to breed. The more time salmon spend at sea, the larger they grow. Females generally take between 2-3 years to mature, but most males return after just one year at sea.

Mobley’s study showed that for every year spent at sea, females gain over 4 kilograms of body weight and produce 60% more offspring. Males, on the other hand, gain nearly 5 kilograms of body weight and produce 200% more offspring for every year they spend at sea.

However, spending more time at sea comes with a significant cost. Very few of these older larger fish return to spawn. “This is presumably because spending more time at sea exposes fish longer to predators, fishing, and diseases, and thus a higher risk of death before having a chance to spawn,” explains Mobley.

“Knowing the reproductive contributions of different sized fish in this river section can help us to develop more accurate models of offspring production. These are needed for developing Teno salmon management guidelines,” says Professor Jaakko Erkinaro from Natural Resources Institute Finland. “It also helps our ongoing research aimed at predicting how many large adults may survive at sea to return to spawn,” Mobley adds.

Larger salmon have more mating partners

Like most animals in nature, salmon are not monogamous and can have up to eight mating partners, the study shows. Having more mating partners ensures successful fertilization of eggs and passing on their genes to the next generation.

Nearly all females captured in the study produced offspring, mating on average with more than two males, and gained 35% more mates for each year they spent at sea. Males have, on average, less than one mate, indicating that many males are excluded from mating presumably through strong competition by bigger males. For each year spent at sea, males gain 60% more mates. This means that larger salmon, in particular males, have a distinct advantage when it comes to finding mates.

Where are the females?

In the study population, females are a rare commodity. There are up to seven males for every female at the spawning ground near the entrance of the Utsjoki River. This pattern is consistent across all years of the study. Having a high number of males likely increases fights among males for opportunities to mate with the few available females. Why so few females return to this particular site remains a mystery, as other locations in the Teno River have a more balanced mix of males and females.

Early life-history affects female reproduction

Prior to entering the sea, juvenile salmon usually spend between 3-5 years in freshwater. The researchers were surprised to find that the longer the females stay in freshwater, the fewer years they spend at sea, and return to spawn at a much smaller size. Because these females are smaller, they have fewer eggs and produce less offspring. Males, on the other hand, do not seem to be affected by spending more time in freshwater.

“These results show how overlooked aspects of salmon life-history are important to the long-term conservation of these fish,” said Mobley.

Shipwreck Coral Reefs, video


This video says about itself:

Exploring Shipwreck Coral Reefs

Next on Blue World, Jonathan learns how to dive without a scuba tank by holding his breath a long time! But first, he investigates shipwrecks that are turning into coral reefs. All of this today on Jonathan Bird’s Blue World!

Nurseryfish video


This 20 June 2020 video says about itself:

Nurseryfish Dads Give Their Young a Headstart… Literally

Happy Father’s day! Today we’re talking about the fintastic Nurseryfish, which is one of the best dads you can fish for.

Thanks to Dr. Tim Berra for teaching us more about these amazing fish as well as providing such awesome pictures!

Hosted by: Hank Green

These fish live in Asia and Australia.

Carboniferous fossil fish sturgeon-like, no sturgeon


Tanyrhinichthys mcallisteri

From the University of Pennsylvania in the USA:

300-million-year-old fish resembles a sturgeon but took a different evolutionary path

June 22, 2020

Sturgeon, a long-lived, bottom-dwelling fish, are often described as “living fossils,” owing to the fact that their form has remained relatively constant, despite hundreds of millions of years of evolution.

In a new study in the Zoological Journal of the Linnean Society, researchers led by Jack Stack, a 2019 University of Pennsylvania graduate, and paleobiologist Lauren Sallan of Penn’s School of Arts & Sciences, closely examine the ancient fish species Tanyrhinichthys mcallisteri, which lived around 300 million years ago in an estuary environment in what is today New Mexico. Although they find the fish to be highly similar to sturgeons in its features, including its protruding snout, they show that these characteristics evolved in a distinct evolutionary path from those species that gave rise to modern sturgeons.

The find indicates that, although ancient, the features that enabled Tanyrhinichthys to thrive in its environment arose multiple times in different fish lineages, a burst of innovation that was not previously fully appreciated for fish in this time period.

“Sturgeon are considered a ‘primitive’ species, but what we’re showing is that the sturgeon lifestyle is something that’s been selected for in certain conditions and has evolved over and over again,” says Sallan, senior author on the work.

“Fish are very good at finding solutions to ecological problems,” says Stack, first author on the study, who worked on the research as a Penn undergraduate and is now a graduate student at Michigan State University. “This shows the degree of both innovation and convergence that’s possible in fishes. Once their numbers got up large enough, they started producing brand new morphologies that we now see have evolved numerous times through the history of fishes, under similar ecological conditions.”

The first fossil of Tanyrhinichthys was found in 1984 in a fossil-rich area called the Kinney Brick Quarry, about a half-hour east of Albuquerque. The first paleontologist to describe the species was Michael Gottfried, a Michigan State faculty member who now serves as Stack’s advisor for his master’s degree.

“The specimen looks like someone found a fish and just pulled on the front of its skull,” Stack says. Many modern fish species, from the swordfish to the sailfish, have protuberant snouts that extend out in front of them, often aiding in their ability to lunge at prey. But this characteristic is much rarer in ancient fishes. In the 1980s when Gottfried described the initial specimen, he posited that the fish resembled a pike, an ambush predator with a longer snout.

During the last decade, however, several more specimens of Tanyrhinichthys have been found in the same quarry. “Those finds were an impetus for this project, now that we had better information on this enigmatic and strange fish,” Stack says.

At the time that Tanyrhinichthys roamed the waters, Earth’s continents were joined in the massive supercontinent called Pangea, surrounded by a single large ocean. But it was an ice age as well, with ice at both poles. Just before this period, the fossil record showed that ray-finned fishes, which now dominate the oceans, were exploding in diversity. Yet 300 million years ago, “it was like someone hit the pause button,” Sallan says. “There’s an expectation that there would be more diversity, but not much has been found, likely owing to the fact that there just hasn’t been enough work on this time period, especially in the United States, and particularly in the Western United States.”

Aiming to fill in some of these gaps by further characterizing Tanyrhinichthys, Stack, Sallan, and colleagues closely examined the specimens in detail and studied other species that dated to this time period. “This sounds really simple, but it’s obviously difficult in execution,” Stack notes, as fossils are compressed flat when they are preserved. The researchers inferred a three-dimensional anatomy using the forms of modern fishes to guide them.

What they noticed cast doubt on the conception of Tanyrhinichthys as resembling a pike. While a pike has an elongated snout with its jaws at the end of it, allowing it to rush its prey head-on, Tanyrhinichthys has an elongated snout with its jaws at the bottom.

“The whole form of this fish is similar to other bottom dwellers,” Stack says. Sallan also noticed canal-like structures on its snout concentrated in the top of its head, suggestive of the locations where sensory organs would attach. “These would have detected vibrations to allow the fish to consume its prey,” says Sallan.

The researchers noted that many of the species that dwelled in similar environments possessed longer snouts, which Sallan called “like an antenna for your face.”

“This also makes sense because it was an estuary environment,” Sallan says, “with large rivers feeding into it, churning up the water, and making it murky. Rather than using your eyesight, you have to use these other sensory organs to detect prey.”

Despite this, other features of the different ancient fishes’ morphology were so different from Tanyrhinichthys that they do not appear to have shared a lineage with one another, nor do modern sturgeon descend from Tanyrhinichthys. Instead, the long snouts appear to be an example of convergent evolution, or many different lineages all arriving at the same innovation to adapt well to their environment.

“Our work, and paleontology in general, shows that the diversity of life forms that are apparent today has roots that extend back into the past,” says Stack.

Three-spined stickleback fish evolution, new research


This 2014 video says about itself:

Natural selection leads to the evolution of new traits. In this educational video, see how stickleback fish have adapted to live permanently in freshwater environments. Explore a case study of natural selection with this classroom-ready biology video.

Though stickleback fish once lived in the ocean, some populations now thrive in freshwater environments. This change resulted in drastic physical transformations. Explore topics in gene expression and adaptation in this fascinating short film.

From the University of Helsinki in Finland:

Parallel evolution in three-spined sticklebacks

What happens in the Eastern Pacific, stays in the Eastern Pacific

June 22, 2020

A group of researchers from the University of Helsinki used novel and powerful methods to disentangle the patterns of parallel evolution of freshwater three-spined sticklebacks at different geographic scales across their distribution range. The group concludes that the conditions under which striking genome-wide patterns of genetic parallelism can occur may in fact be far from common — perhaps even exceptional.

The three-spined stickleback (Gasterosteus aculeatus), a thumb-sized fish distributed across the Northern hemisphere, is a textbook model species in evolutionary biology. With the retreat of ice sheets since the last glacial maximum, ancestral marine populations have repeatedly colonised newly-formed freshwater habitats. Across their distribution range, sticklebacks in these novel freshwater environments exhibit remarkable similarities in their morphology, physiology and behaviour, a phenomenon known as “parallel evolution.”

“What is really remarkable in our results is that the repeatability of evolution in response to similar selection pressures in different oceans can be so different,” says group leader Juha Merilä, Professor at the Faculty of Biological and Environmental Sciences, University of Helsinki.

The genetic underpinnings of such parallel evolution have fascinated scientists for years, and they have discovered that the observed marine-freshwater differentiation is underlain by surprisingly parallel changes also at the genetic level. However, most studies on this topic have been based on either limited geographic sampling or focused only on populations in the Eastern Pacific region.

“As scientists, we are often tempted to provide simple narratives to extremely complex problems. What I liked the most about this project is that we did the exact opposite: we show that the story behind the three-spined stickleback’s spectacularly fast adaptation to novel habitats may be more complex than previously thought. I think that deciphering the role of demographic history in shaping evolutionary adaptation is a necessary step in solving the mystery,” says co-author Paolo Momigliano, postdoctoral researcher at the Faculty of Biological and Environmental Sciences, University of Helsinki.

Genetic parallelism 10 times higher in the Eastern pacific

With novel and powerful methods, a group of researchers from the University of Helsinki disentangled patterns of parallel evolution of freshwater three-spined sticklebacks at different geographic scales across their distribution range. They found that the extraordinary level of genetic parallelism observed in the Eastern Pacific region is not observed in the rest of the species’ range. In fact, they found approximately 10-fold higher levels of genetic parallelism in the Eastern Pacific compared to the rest of the world.

“I have been studying the worldwide population histories of the species in my PhD. We found their ancestral populations are residing in the Eastern Pacific. We predicted that the region harbours the source of ancestral genetic variations for parallel evolution, and such genetic variation could be lost during colonisation to the rest of the world, for instance in the Atlantic. These predictions were tested by both empirical and simulated data,” explains first author Bohao Fang, PhD candidate from the Faculty of Biological and Environmental Sciences, University of Helsinki.

What happens in the Eastern Pacific, stays in the Eastern Pacific

Their simulations showed that this difference in the degree of parallelism likely depends on the loss of standing genetic variation — the raw material upon which selection acts — during the colonisation of the Western Pacific and Atlantic Oceans from the Eastern Pacific Ocean.

This discrepancy could have been further accentuated by periods of strong isolation and secondary contact between marine and freshwater habitats in the Eastern Pacific, consistent with the group’s results and the geological history of the area. This secondary contact likely happened after the colonisation of the Atlantic Basin, resulting in much more genetic variation available for local adaptation in the Eastern Pacific — variation that never had the chance to spread to the Atlantic. In other words, the discrepancy in genetic patterns of parallel evolution between the two oceans is a result of the complex demographic history of the species, which involved range expansions and demographic bottlenecks.

“Our less assumption-burdened methods have been a key to quantifying parallel evolution at different geographic scales for the type of data that was available for this study. I thoroughly enjoy developing novel methods to study adaptation and evolution, and the idea that parallel evolution might be exceptional in the Eastern Pacific compared to the rest of the world has intrigued me for a long time. It was a lucky coincidence that I became a part of the Ecological Genetics Research Unit led by Juha Merilä where the samples to finally test this hypothesis became available,” concludes Petri Kemppainen, co-first author, method developer, and postdoctoral researcher at the Faculty of Biological and Environmental Sciences, University of Helsinki.

Nine walking shark species discovered


This 20 June 2020 video says about itself:

Scientists have discovered 9 species of ‘walking’ sharks.

In US news and current events today, researchers have confirmed that walking sharks branched from their nearest ancestor 9 million years ago, making them the most recently evolved type of shark. These sharks, who use their fins to ‘walk’ on the ocean floor, have been found off the coasts of Australia, Indonesia & New Guinea. Scientists have discovered a total of 9 species of walking sharks over the past 2 decades.

Read more here.

How betta fish fight, new research


This 2016 video says about itself:

The Complete Betta Fish Life Cycle in 3 Minutes

Love is beautiful. Betta fish love is uniquely beautiful. Watch their life evolve from courtship, eggs, fry to adulthood in this glittering video.

From PLOS:

Fighting fish synchronize their combat moves and their gene expression

Betta fish opponents undergo similar brain changes that become more synchronized after longer fights

June 17, 2020

When two betta fish are fighting for dominance, not only do their attacks mirror each other, but the gene expression in their brain cells also starts to align. The new findings, published June 17th in PLOS Genetics by Norihiro Okada of Kitasato University, Japan, may explain how the fish synchronize their fighting behavior.

The fighting fish Betta splendens is famous for its aggression, but opponents typically stop fighting after assessing the other’s abilities to avoid any serious injuries. The small freshwater fish is commonly used to study aggression in the lab, and it employs a handful of standard tactics like mouth-locking, bites, strikes and swimming to the surface to gulp air. In the new study, researchers observed that during a fight, two male opponents modify their actions to match the aggressive behavior of the other, leading to tightly synchronized battles.

Furthermore, when the researchers analyzed the brains of both opponents, they observed that the fish also synchronized which genes were turned on or off in brain cells. The fighting pair had similar changes in gene activity related to learning, memory, synapse function and ion transport across cell membranes. The synchronization was specific to a fighting pair and became stronger after fighting for an hour compared to a 20-minute fight, suggesting that the degree of synchronization was driven by fighting interactions.

The new study takes a neurogenomic approach to the old question of how animals synchronize their behavior. Similar mirrored behaviors also occur during mating, foraging and cooperative hunting, and these behaviors may also trigger synchronized brain changes in the pairs of animals. “One of my future plans is to elucidate what happens in the male-female interaction of fish on the molecular level,” said author Norihiro Okada.

The findings suggest that even though the betta fish are fighting each other, sometimes to the death, their brains may be cooperating at the molecular level.

How fish evolve into terrestrial animals


This 2018 video says about itself:

Fashionable Leaping Blennies | Planet Earth: Blue Planet II

Looking for love isn’t easy when you’re a blenny, but with a bright orange fin and a little determination, anything’s possible.

From the British Ecological Society:

How fish got onto land, and stayed there

June 17, 2020

Research on blennies, a family of fish that have repeatedly left the sea for land, suggests that being a ‘jack of all trades’ allows species to make the dramatic transition onto land but adapting into a ‘master of one’ allows them to stay there. The findings are published in the British Ecological Society journal Functional Ecology.

Researchers from the University of New South Wales and the University of Minnesota pooled data on hundreds of species of blennies, a diverse family of fish where some are aquatic and others have left the water completely. They found that a flexible diet and behaviour were likely to be instrumental in the transition to land.

However, once out of the water, restrictions on the type of food available triggered major evolutionary changes, particularly to their teeth, as land-dwelling blennies have become specialists in scraping algae and detritus from rocks.

Dr Terry Ord, lead author of the research, said: “The implications of our findings are that having a broad diet or being behaviourally flexible can help you move into a new habitat. But once there, this flexibility becomes eroded by natural selection. This presumably means those highly specialised species are less likely to be able to make further transitions, or cope with abrupt environment changes in their existing habitat.”

The scenario of fish colonising land has obvious parallels with the origin of all land vertebrates. “Fossils can give us important insights into how that transition might have unfolded, and the types of evolutionary adaptations it required or produced. But having a contemporary example of fish making similar ecological transitions can also help us understand the general challenges that are faced by fish out of the water” said Dr Ord.

Blennies are a remarkable family of fish with different species occupying strikingly different environments. Some are aquatic. Others spend time in and out of the water in the intertidal zone, an extreme environment with fluctuating water levels and pools that can rapidly change in temperature and oxygen levels.

Some species of blenny are terrestrial and spend almost their entire lives out of the water in the splash zone and must keep moist in order to breathe through their skin and gills. Despite these challenges, blennies have been incredibly successful in repeatedly making these dramatic transitions.

Because of this diversity, different blenny fish species represent clearly defined stages of the invasion process between two completely different environments. This makes them a unique group of animals to study.

Dr Ord explained the origin of the study with his co-author Dr Peter Hundt: “We both had extensive data collected on many different species of blenny from across the world. Peter had detailed information on diet and teeth morphology, while I had lots of data on behaviour and frequency of different species emerging from water for brief or extended periods on land.

“We threw a set of complex evolutionary statistical models at this combined data and we were able to reveal the sequence of events that likely allowed aquatic marine fishes to ultimately evolve into fishes that could leave water and then colonise land. Our study also showed how those species on land adaptively changed to better suit the specialised diet needed to survive on land.”

The authors caution that although the observational data suggests a flexible diet and behaviour allows a transition to new environments to occur, it cannot confirm causality. “Ideally we would perform some type of experimental investigation to try to establish casualty. What this experimental study might be is hard to imagine at this stage, but we’re working on it.” Said Dr Ord.

The authors are also looking to further investigate how the invasion of land has impacted other aspects of blenny fish behaviour, ecology and bodies. “Terrestrial blennies are really agile out of water, and I suspect they’ve adapted their body shape to allow them to hop about the rocks so freely. Which in turn implies they might not be able to go back to the water” said Dr Ord, “It would also be exciting to know how their sensory systems might have adapted out of the water as well, given vision and smell would probably work quite differently in these environments.”

New shark species discovered off Japan


The Shirai’s spurdog (Squalus shiraii): lateral (A-C) and ventral (D, E) views. Scale bars – 50 mm. Image credit: Viana & Carvalho, doi: 10.3897/zse.96.51962

From ScienceDaily:

A new character for Pokémon? Novel endemic dogfish shark species discovered from Japan

June 11, 2020

Summary: A new endemic deep-water dogfish shark: Squalus shiraii, was discovered in the tropical waters of Southern Japan by an international team of scientists. The finding brings the amount of spurdog shark species inhabiting Japanese waters to six.

Newly discovered creatures can often be as impressive and exciting as the ones from the Japanese movies and shows. Many of those fictional characters, including inhabitants of the famous Pokémon universe, might have their analogues among the real animals native to Japan. Maybe, a new species of the dogfish shark published in the open-access journal Zoosystematics and Evolution is also “a real Pokémon” to be?

A new deep-water dogfish shark: Squalus shiraii, was discovered in the tropical waters of Southern Japan by an international team of scientists, led by Dr. Sarah Viana from South African Institute for Aquatic Biodiversity.

The new shark has the body length of 59-77 cm and some unique characteristics such as tall first dorsal fin and caudal fin with broad white margins. Currently, the species is known exclusively as a Japanese endemic, occurring in the tropical shallow waters of Southern Japan in the North-western Pacific.

Spurdogs are commercially important for the world fish trade taxa. They are caught for a range of purposes: consumption of meat, fins and liver oil. Despite their high occurrence, the accurate identification data of species is scarce, population threats and trends remain unknown.

Japan currently represents one of the world’s leading shark fish trade countries, though, during the last decades the amount of shark catches is decreasing and over 78 elasmobranch species traded in Japanese shark fin markets are now evaluated as threatened.

The new species Squalus shiraii previously used to be massively misidentified with shortspine spurdog, due to the resembling shape of body, fins and snout length. However, there are some differences, defining the specificity of the new species.

“Squalus shiraii has body brown in colour, postventral and preventral caudal margins whitish, dorsal and ventral caudal tips broadly white and black upper caudal blotch evident in adults. S. mitsukurii has body conspicuously black to dark grey and caudal fins black throughout with post-ventral caudal margin fairly whitish and black upper caudal blotch not evident in adults,” shares lead author Dr. Viana.

Scientists propose the name for the newly described species as Shirai’s spurdog in honor to Dr. Shigeru Shirai, the former Japanese expert of the group.