Chimaera ghost sharks, video


This 16 September 2019 video says about itself:

Chimaera: The Deep Sea Phantom

The Chimaera, or Ghost Shark, looks like its skin has been stitched together.

Female Trinidad guppies save males from starvation


This 3 September 2018 video says about itself:

This video gives an impression of the fieldwork we conduct to study guppy behavior in the rainforest of Trinidad. It also summarizes the main conclusions of our scientific paper in Nature Ecology and Evolution, which examines how being social helps guppies find food.

Reference to Paper: Snijders L, Kurvers RHJM, Krause S, Ramnarine IW, Krause J (2018). Individual- and population-level drivers of consistent foraging success across environments. Nature Ecology and Evolution.

From Forschungsverbund Berlin in Germany:

Male Trinidad guppies find food thanks to females

September 13, 2019

For male Trinidad Guppies applies: if you are hungry, seek female company. A recent study led by scientists of the the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) and the Leibniz Institute for Zoo and Wildlife Research (IZW) together with other research institutions provides evidence that male guppy fish in the presence of females more often ended up at novel food patches. In contrast, female food discovery was independent of male presence.

Trinidad guppies (Poecilia reticulata) live in small watercourses in the rainforests of Trinidad. They have a preference for sporadic high-quality food resources, like fruits and insects, falling into the water- so it is usually uncertain when and where they encounter food. In this study, behavioural ecologist Lysanne Snijders and her team set up a field experiment and manipulated guppy sex compositions (all male, all female or mixed) in the wild using individually colour-marked guppies. They conducted social observations, followed by foraging trials.

Males reached more food patches when there were females around. Yet, females reached a similar number of patches either with or without males present. Males also spent less time social in absence of females, but the absence of males had no effects for females. The researchers analysed if this time spent socially was linked to patch discovery success. Indeed, in agreement with a previous study, more social guppies ended up at more food patches.

“Life in the group can be advantageous. You have to share the food with your peers, but it is also easier to find it if you use the information of others,” explains Lysanne Snjiders. Guppies, for example, react to the typical behaviour of successful food finders, which is: swim faster, grab food, stay there and eat.

The researchers can only guess why males behave differently in the absence of females than in sexually mixed groups. “In this case, males among themselves are more likely to be in a state of competition than cooperation and therefore spend less time together and miss out on important information,” says Lysanne Snijders.

The head of the study, IGB-researcher Prof. Jens Krause, is investigating the dynamics of swarm behaviour and collective intelligence in animals. He explains the importance of this field of research: “If we are able to understand the interactions of animals within a group, we can derive from this knowledge information about the spread of diseases, reproduction and predator-prey relationships. The structure of social networks may also be a decisive factor concerning the stability of a population. Such knowledge may help wildlife managers and conservationists, for example, to optimise disease management, breeding programmes or reintroduction activities.”

Guppies, a perennial pet store favorite, have helped a UC Riverside scientist unlock a key question about evolution: Do animals evolve in response to the risk of being eaten, or to the environment that they create in the absence of predators? Turns out, it’s the latter: here.

Shark tagged from submarine, first time ever


This 9 September 2019 video says about itself:

Shark Tagged From Submarine For First Time In History | National Geographic

For the past year, a research team has developed a new strategy to study the near-threatened bluntnose sixgill shark in deep waters.

Prehistoric sharks invented suction feeding, new research


This 26 February 2019 video says about itself:

SHARKS and other prehistoric fish. Size comparison chart. Paleoart

INCLUDED TAXA: Harpagofututor, Echinochimaera, Falcatus, Stethacanthus, Cladoselache, Hybodus, Orthacanthus, Edestus, Mawsonia, Xiphactinus, Great White Shark, Helicoprion, Rhizodus, Onchopristis, Dunkleosteus, Carcarocles megalodon, Leedsightys.

From the University of Chicago in the USA:

Long before other fish, ancient sharks found an alternative way to feed

3D reconstructions of a 335-million-year-old shark fossil show how it evolved suction feeding 50 million years before bony fish

September 11, 2019

Researchers from the University of Chicago have used tools developed to explore 3D movements and mechanics of modern-day fish jaws to analyze a fossil fish for the first time. Combined with CT imaging technology able to capture images of the fossil while it is still encased in rock, the results reveal that the 335-million-year-old shark had sophisticated jaws capable of the kind of suction feeding common to bony fishes like bass, perch, carp and also modern-day nurse sharks.

Remarkably, these ancient shark jaws are some 50 million years older than the earliest evidence of similar jaws adapted for suction feeding in bony fishes. This shows both the evolutionary versatility of sharks, and how sharks responded quickly to new ecological opportunities in the aftermath of one of the five big extinctions in Earth’s history.

“Among today’s aquatic vertebrates, suction feeding is widespread, and is often cited as a key factor contributing to the spectacular evolutionary success of ray-finned fishes”, said Michael Coates, PhD, professor of organismal biology and anatomy at the University of Chicago and senior author of the new study. “But here we show that high-performance aquatic suction feeding first appeared in one of the earliest known sharks.”

A complete construction kit to rebuild a shark

The study, published this week in Science Advances, describes the fossil of Tristychius arcuatus, a 2-foot long shark similar to a dogfish. It was first discovered by Swiss biologist Louis Agassiz in 1837, and later described in detail by John Dick, a former classmate of Coates’, in 1978. Tristychius, and other Devonian period sharks like it, are found in ironstone rock nodules along the shores of the Firth of Forth near Edinburgh, Scotland.

Shark fossils are rare because their cartilage skeleton usually rots away before there’s any chance of fossilization. For decades, researchers studying ancient sharks have been limited to isolated teeth and fin spines. Even if they do find a more complete skeleton, it’s usually flattened, or, if it’s encased in one of these stones, it crumbles when they try to remove it.

Coates and his lab have been leading the field in applying modern imaging technology and software to study these challenging fossils. CT scanning allows them to create 3D images of any fossilized cartilage and the impressions it left while still encased in the stone. Then, using sophisticated modeling software originally developed to study structure and function in modern-day fish, they can recreate what the complete skeleton looked like, how the pieces fit together and moved, and what that meant for how these sharks lived.

“These new CT methods are releasing a motherlode of previously inaccessible data,” Coates said.

His team started reexamining some of the same fossils Dick studied, as well as specimens left untouched in earlier research. “Some of this is superbly preserved,” Coates said. “We realized that when we got all the parts out [virtually], we had the complete construction kit to rebuild our shark in 3D.”

Beating underwater physics

That virtual construction kit also allowed them to create 3D plastic printouts of the cartilages that build a shark’s skull. These, in turn, allowed Coates and his team to model movements and connections, both physically and virtually, to see how the skull worked.

Fish that use suction feeding essentially suck water in through their mouths to catch elusive prey, such as worms, crustaceans and other invertebrates from the ocean floor. To do so, they have to draw water in when they open their mouth, but not force it back out when they close it.

Suction feeders overcome these challenging physics by funneling the water back out through their gills. The amount of suction they create can be enhanced by flexible arches and joints that expand the cheeks and the volume inside the mouth to draw the water through (imagine the feeling when you hold your hands together underwater and slowly pull your palms apart).

Today’s fish have perfected this process, but Tristychius had a similar feeding apparatus that could expand as it opened and closed its mouth to control the flow of water (and food). Crucially, this included a set of cartilages around the mouth that limited the size of the opening to control the amount of suction. The circular mouth was pushed forward at the end of its muzzle like a modern-day carpet shark or nurse shark, not a gaping, toothy maw like a great white.

While other sharks at the time did have the more typical snapping jaws, the combination of expanding cheeks and a carefully controlled mouth aperture provided Tristychius with access to previously untapped food resources, such as prey taking refuge in shallow burrows or otherwise difficult-to-capture schools of shrimp or juvenile fish, around 50 million years before bony fish caught on to the same technique.

“The combination of both physical and computational models has allowed us to explore the biomechanics in a Paleozoic shark in a way that’s never been done before,” Coates said. “These particular sharks were doing something sophisticated and new. Here we have the earliest evidence of this key innovation that’s been so important for multiple groups of fishes and has evolved repeatedly.”

Additional authors for the study include Kristen Tietjen from the University of Chicago, Aaron M. Olsen from Brown University, and John A. Finarelli from University College Dublin, Ireland.

Mako shark migration, new research


This 2 August 2019 video from the USA says about itself:

Joe Remeiro, Devon Massyn and Keith Poe capture amazing footage of a huge grander Mako shark, off the coast of California.

From the NOAA Fisheries West Coast Region in the USA:

Mako shark tracking off west coast reveals ‘impressive’ memory and navigation

These top predators travel far across the Pacific, returning to the same areas in the Southern California Bight each year

September 11, 2019

The largest effort ever to tag and track shortfin mako sharks off the West Coast has found that they can travel nearly 12,000 miles in a year. The sharks range far offshore, but regularly return to productive waters off Southern California, an important feeding and nursery area for the species.

The findings demonstrate “an impressive show of memory and navigation.” The sharks maneuver through thousands of miles of the Pacific but return to where they have found food in years past, said Heidi Dewar, a research fisheries biologist at NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, California.

Researchers tagged 105 mako sharks over 12 years — from 2002 to 2014. The tags record the sharks’ movements, as well as the environments the sharks pass through. Researchers have long recognized that ocean waters from Santa Barbara south to San Diego, known as the Southern California Bight, are an important habitat for mako sharks. Prior to this study, however, they knew little about what the sharks do and where they went beyond those waters.

The researchers are from NOAA Fisheries, Stanford University, Tagging of Pacific Predators, and the Center for Scientific Research and Higher Education in Baja California. They reported their results in the journal Animal Biotelemetry.

“We did not know what their overall range was. Were there patterns that they followed?” asked Nicole Nasby-Lewis, a NOAA Fisheries research scientist at the Southwest Fisheries Science Center and lead author of the new research. “It turns out they have their own unique movement patterns.” Sharks tracked over multiple years returned to the same offshore neighborhoods year after year.

Long-Range Travelers

The tagging data overall revealed that the sharks travel widely along the West Coast. They venture as far north as Washington, as far south as Baja California, and westward across the Pacific as far as Hawaii. The sharks tagged off California remained on the eastern side of the Pacific east of Hawaii. This indicates that they do not mix much with mako sharks in other parts of the Pacific.

Although there are examples of mako sharks crossing the ocean, it is probably the exception rather than the rule, said Dewar, a coauthor of the new research.

The finding provides insight into population dynamics of mako sharks across the Pacific. It also allows scientists to identify which fisheries the tagged mako sharks might encounter. Muscular mako sharks are a popular sport fishing target. They are also caught in U.S. longline and drift gillnet fisheries and are common in the international trade in shark fins. Mako sharks are overfished in the Atlantic Ocean, but not in the Pacific.

The researchers used two types of tags to track the sharks. One type, called pop-up tags, collect data and eventually pop off the animal and float to the surface, where they transmit their data via satellite. The second type transmits data to satellites each time the shark surfaces, determining the animal’s location by measuring tiny shifts in the frequency of the radio transmission.

Remembering Southern California

Mako sharks are among the fastest swimmers in the ocean, hitting top speeds of more than 40 miles per hour. The larger tagged sharks traveled an average of about 20 miles a day and a maximum of about 90 miles per day. They travel long distances in part because they must swim to move water through their gills so they can breathe, Dewar said.

Large numbers of juvenile sharks caught in the Southern California Bight indicate that it is a nursery area for the species. Tagged mako sharks returned there annually, most typically in summer when the waters are most productive. The tracks of the tagged sharks may look at first like random zig-zags across the ocean, Dewar said. They actually illustrate the sharks searching for food and mates based on what they remember from previous years.

“If you have some memory of where food should be, it makes sense to go back there,” Dewar said. “The more we look at the data, the more we find that there is a pattern behind their movements.”

The tagging results also provide a wealth of data that scientists can continue to plumb for details of the sharks’ biology and behavior. About 90 percent of the time the sharks remained in the top 160 feet of ocean, for example, occasionally diving as deep as 2,300 feet. Although the sharks traveled widely, they mainly stayed in areas with sea surface temperatures between about 60 and 70 degrees Fahrenheit.

“We can continue to ask new questions of the data to understand these unique movement patterns,” Nasby-Lucas said. “There’s a lot more to learn.”

Electric eels, strongly electric new species discovery


This video says about itself:

Electric eels leap from the water to deliver a more powerful shock to an animal they perceive to be a threat, according to research by Vanderbilt University biologist Kenneth Catania. Video footage demonstrates the defensive behavior in slow motion with the aid of an artificial arm and prop crocodile head outfitted with LEDs. This study confirms a claim made in 1800 by the German naturalist Alexander von Humboldt.

From the Smithsonian Institution in the USA:

Electric eel produces highest voltage discharge of any known animal

September 10, 2019

South American rivers are home to at least three different species of electric eels, including a newly identified species capable of generating a greater electrical discharge than any other known animal, according to a new analysis of 107 fish collected in Brazil, French Guiana, Guyana and Suriname in recent years.

Scientists have known for more than 250 years that electric eels, which send electricity pulsing through the water to stun their prey, live in the Amazon basin. They are widely distributed in swamps, streams, creeks, and rivers across northern South America, and have long been thought to belong to a single species. With modern genetic and ecological analyses, however, researchers at the Smithsonian’s National Museum of Natural History have discovered that electric eels in the Amazon basin belong to three different species that evolved from a shared ancestor millions of years ago. The findings are reported Sept. 10 in the journal Nature Communications.

The identification of two new species of electric eel highlights how much remains to be discovered within the Amazon rainforestone of Earth’s biodiversity hotspots — as well as the importance of protecting and preserving this threatened environment, says study leader C. David de Santana, a research associate in the museum’s division of fishes. “These fish grow to be seven to eight feet long. They’re really conspicuous,” he says. “If you can discover a new eight-foot-long fish after 250 years of scientific exploration, can you imagine what remains to be discovered in that region?”

About 250 species of electricity-generating fish are known to live in South America, although electric eels (which actually are fish with a superficial eel-like appearance) are the only ones that use their electricity to hunt and for self-defense. Like other electric fishes, they also navigate and communicate with the electricity they produce. Electric eels inspired the design of the first battery in 1799, and as researchers have learned more about how they generate enough electricity to stun a large animal, scientists and engineers have gained new ideas about how to improve technology and possibly even treat disease.

Smithsonian scientists have been collaborating with researchers at the University of São Paulo’s Museum of Zoology in Brazil and other institutions around the world to explore the diversity of the eels and other electric fishes in South America. As part of that effort, de Santana closely examined the electric eel specimens he and his colleagues had collected in the Amazon over the last six years.

All the specimens looked pretty much the same. Finding no external features on the fish that clearly distinguished different groups on first glance, de Santana turned to the animals’ DNA, and found genetic differences that indicated his 107 specimens represented three different species. Reexamining the animals with the genetic results in hand, he found subtle physical differences corresponding to the three genetic groups. He determined that each species has its own unique skull shape, as well as defining characteristics on the pectoral fin and a distinctive arrangement of pores on the body.

Each species has its own geographic distribution, too. The long recognized Electrophorus electricus, once thought to be widely distributed across the continent, actually appears to be confined to the highlands of the Guiana Shield, an ancient geological formation where clear waters tumble over rapids and falls. Electrophorus voltai, one of the two newly discovered species, primarily lives further south on the Brazilian Shield, a similar highland region. The third species, Electrophorus varii, named after the late Smithsonian ichthyologist Richard Vari, swims through murky, slow-flowing lowland waters.

Based on genetic comparisons, de Santana and colleagues determined that two groups of electric eels began to evolve in South America about 7.1 million years ago. One, the common ancestor of E. voltai and E. electricus, lived in the clear waters of the ancient highlands, whereas E. varii lived in the lowlands, whose murky waters were full of minerals and, consequently, conducted electricity more efficiently — an apparently important distinction for electric eels, whose discharge won’t travel as far in environments where conductivity is low.

According to the analysis, E. voltai and E. electricus diverged around 3.6 million years ago, around the time the Amazon River changed course, crossing the continent and traversing highland regions. Notably, de Santana’s team discovered that E. voltai can discharge up to 860 Volts of electricity — significantly more than the 650 Volts generated by E. electricus. This makes the species the strongest known bioelectric generator, and may be an adaptation to the lower conductivity of highland waters, he says.

De Santana says the previously overlooked diversity his team discovered is exciting since it creates new opportunities to investigate how animals generate high-voltage electricity by sequencing and comparing their genomes. Because the three species of electric eels diverged from one another so long ago, they may have evolved unique systems for electrogenesis, and, in the case of E. voltai, this system is entirely unexplored. “It could really have different enzymes, different compounds that could be used in medicine or could inspire new technology,” he says.