Evolution – Page 2 – Science Sushi

Whistling While They Work: Cooperative Laguna Dolphins Have A Unique Accent

Fishermen working with a cooperative dolphin to enhance their catch. Photo Credit: Carolina Stratico

When the mullet migrate northward, the fishermen in Laguna, Brazil are waiting. They rise early and take their places in line, waist-deep in the water, tarrafa—a kind of circular throwing net—in hand. Without a word, the dolphins arrive, herding schools of mullet towards the fisher line. The fishers say that the dolphins are an essential part of their fishing; they wait to fish until their marine helpers to arrive, in some cases standing for an hour or more, calling to the animals: “let’s work”. The fishers work as a unit, trading out their spots in line as the dolphins fill their nets.

But while the humans are united, the dolphin community is divided. Only some of the population cooperate with fishers in this manner. Scientists discovered that the ones that work with people form their own cohesive social network, separate from the other dolphins in the area. “The cooperative fishery appears to have influenced the structuring of this bottlenose dolphin population into social communities,” explain Bianca Romeu and her colleagues at Brazil’s Universidade Federal de Santa Catarina in a new paper this month in the journal Ethology. Their latest work reveals the depth of this rift: the cooperative dolphins don’t just behave differently, they communicate differently, too.

Continue reading “Whistling While They Work: Cooperative Laguna Dolphins Have A Unique Accent”

Tiny Bat Shrugs Off Stings From Deadly Scorpion

These tough bats can tussle with the deadliest scorpions in North America and win. Photo by Connor Long — These tough bats can tussle with the deadliest scorpions in North America and win.
Photo by Connor Long

Pallid bats (Antrozous pallidus) are quirky little creatures, the sole species in their genus. Their long ears, which can equal half their body length, make them look quintessentially batty, but unlike most of their night hunting relatives, they prefer to tackle ground-dwelling dinners—a strategy called “gleaning.” Pallid bats glean as much as half their body weight in prey every night, and their diet includes a wide range of crunchy little critters, including crickets, praying mantis, and beetles.

It is their taste for scorpions, though, that is particularly intriguing, and piqued the curiosity of scientists. It was unknown whether the bats have a trick for catching scorpions that keeps them from being stung, or whether they are resistant to the animals’ agonizing toxins. In a new PlosONE paper, researchers show it’s the latter: the bats’ laissez-faire attitude towards venom stems from an invulnerability to scorpion neurotoxins due to alterations in the voltage-gated sodium channels that the toxins target. Continue reading “Tiny Bat Shrugs Off Stings From Deadly Scorpion”

Older, wiser, deadlier: “blood nuking” effects of Australian brown snake venom acquired with age

A Shield-snouted Brown Snake (Pseudonaja aspidorhyncha) from Northern Territory, Australia. Photo by Christopher Watson — A shield-snouted brown snake (*Pseudonaja aspidorhyncha*) from Northern Territory, Australia. Photo by Christopher Watson

There’s an age old belief that baby snakes are more dangerous than adult ones. There are generally two proposed reasons why this could be: either a) young snakes have yet to learn how to control how much venom they inject, so they deliver all of their venom per bite, or b) that because the snakes are smaller, they need more potent toxins to successfully take out their prey. The first is misleading, because even if baby snakes did dump all their venom into each bite, they still have so much less venom than adults that it doesn’t matter (and there isn’t any real evidence they lack self-control*). The second, though, warrants closer investigation: do younger, smaller snakes really have deadlier venoms? A new study on brown snakes in Australia says no—and in fact, the opposite can be true. Continue reading “Older, wiser, deadlier: “blood nuking” effects of Australian brown snake venom acquired with age”

Beware the blenny’s bite: scientists uncover the toxins in fang blenny venom

Meiacanthus atrodorsalis—a prettly little fish with a venomous bite. Photo by Klaus Stiefel / Flickr — *Meiacanthus atrodorsalis*—a pretty little fish with a venomous bite. Photo by Klaus Stiefel via Flickr

“Did you tell her the one about George Losey and the blenny?” Rich Pyle asked with a knowing smirk. Pyle and I were sitting in the living room of legendary ichthyologist Jack Randall for a piece I was writing about him for Hakai Magazine. “It’s a good venom story,” Pyle continued, grinning.

Randall’s eyes lit up with mischievious joy as he launched into the tale. He and George Losey were invited to Guam to bear witness to a massive crown of thorns sea star invasion, he explained (“It was one overlapping another as far as you could see,” he recalled; “They decimated the corals of the whole northern coast”). While he and Losey were diving, Randall saw a small blenny—one of a group of blennies that he knew Losey had taken an interest in. Since he had a three-pronged sling-style spear on him, Randall caught the fish, which remained wriggling on the end of his spear tip. He asked Losey if he wanted it to examine later, and Losey did, but he didn’t have any containers to put it in. So, Losey did what seemed like the obvious thing: he tucked the creature into his swim trunks. “Well, it has a venomous bite…” Randall said laughing—a fact which was unknown at the time. “It bit him right here, on the belly,” Randall gestured, “and he let out a yelp!” That was how George Losey first discovered the venomous nature of fang blennies in the genus Meiacanthus, Randall explained—by making the mistake of putting one in his shorts.
Continue reading “Beware the blenny’s bite: scientists uncover the toxins in fang blenny venom”

What It Takes To Rule The (Marine) World

The dreaded tiger shark (Galeocerdo cuvier) is among a tiny minority of fish species which spans oceans, according to a new paper. Range map from FishBase, image of shark from Wikipedia. — The dreaded tiger shark (*Galeocerdo cuvier*) is among a tiny minority of fish species (<1%!) whose distributions span oceans, according to a new paper. Range map from FishBase, picture of shark by Albert Kok.

Fifty-five years ago, Jack Briggs determined there were 107 fish species with a trait most fish cannot boast: a global distribution. These circumtropical species can be found in all tropical oceans, having found their way around the land masses which split the seas (at least often enough to persist as a single species). Now, in a publication for the journal Fish and Fisheries, Briggs has teamed up with Michelle Gaither, a postdoctoral research associate at Durham University, UK, and colleagues from the University of Hawaii and the California Academy of Sciences to update the half-century-old list. Of the over 20,000 marine fish species, a mere 284 span the seas to maintain a global distribution.

The team was able to re-evaluate Briggs’ original list thanks to breakthroughs in DNA sequencing that have occurred over the past 50 years. By looking at genetic sequences rather than just morphological differences, scientists are able to not only separate similar looking species, they are able to determine whether a single species is split into distinct populations or whether individuals are able to travel vast distances to keep disparate areas connected. Thanks to genetic data, nineteen of the original 107 have since been shown to be complexes of multiple species or not to make it around the globe, while 196 new species have joined the 1% club. Continue reading “What It Takes To Rule The (Marine) World”

Electric Eels Shock Scientists With Sophisticated Hunting Strategies

An electric eel strikes towards its prey. Photo by Ken Catania, Vanderbilt University — An electric eel reaches for its prey. Photo by Ken Catania, Vanderbilt University

Lurking in the muddy waters of the Amazon is a fish that has fascinated some of the greatest scientists in history, including Darwin and Faraday. The electric eel (Electrophorus electrics) is one of the most notorious species on the planet, and yet, there is still much to be learned about these elusive fish.

Despite the name, electric eels aren’t actually eels at all — they’re the only species in the genus Electrophorus, a member of the knifefishes (order Gymnotiformes). These slender shockers can grow to lengths in excess of 7 feet and weigh almost 50 pounds, and are one of the top predators in the muddy South American waters they call home. Their name comes from the current-producing cells that coat roughly two-thirds of their body, called electrocytes, which can collectively discharge more than five times the voltage of a US power socket.

In humans, the shock produced by electric eels feels much like that of a stun gun, causing brief, painful paralysis by overactivation of muscles. And since the discovery that these slippery fishes can cause such a strong electrical pulse, it has generally been assumed that they use their weaponized electricity to stun prey, using their electric organs to produce taser-like shocks. But neurobiologist Kenneth Catania wasn’t sure that was the whole story. While the eels’ shock is enough to take out the small goldfish fed to them in captivity, Catania wasn’t sure that it would work on the diversity of invertebrates and fishes that could comprise the eels’ natural diet. He was curious what would happen if the eel were presented with larger, less easily subdued meal choices. Continue reading “Electric Eels Shock Scientists With Sophisticated Hunting Strategies”

Damsels In Distress Chemically Call For Help

A dusky dottyback considers whether the damselfish in front will fit in its mouth. Photo by Christopher E. Mirbach — A dusky dottyback considers whether the damselfish will fit in its mouth. Photo by Christopher E. Mirbach

Life as a damselfish is hard. These small species are common on tropical reefs worldwide, eating tasty plankton and nipping at other fish. They’re known for their attitude and their beauty, and are often found in stunning schools that cluster around coral heads. But while they’re abundant and vibrant, what they lack are good defenses — no spines, no toxins. Indeed, they are the perfect morsel for other fish-eating fish, and they know it. The moment a predator is detected, they’ll dart for cover, their speed and agility their only hope of survival.

As perpetual menu items, damselfish have developed multiple mechanisms for detecting danger. They can even “smell” danger — when damselfish’s skin is injured, certain chemical compounds leech into the surrounding water. Other damsels can sense these chemicals — essentially “smelling” them — and when a damselfish catches a whiff of Eau de Injury, it runs and hides. But while these chemical alarms seem to benefit fellow damselfish, scientists have long debated whether the injured fish has anything to gain from sending out chemical cues. Are the compounds simply a byproduct of the physical damage? Or do they serve some greater purpose to the fish under attack?

Now, an international team of scientists have published the first evidence of an individual fish benefitting from releasing these chemical alarm cues in a new paper in Proceedings of the Royal Society B. Continue reading “Damsels In Distress Chemically Call For Help”

Poisonous Problems: Chemical Defenses Come With Evolutionary Cost

The chemical weaponry of this beautiful little dart frog come at a high evolutionary cost. Photo by Dirk Ercken

Poison dart frogs are some of the most stunning species on Earth. But their vivid colors aren’t for aesthetics: they’re meant as a warning to potential predators. For while these frogs are visually stimulating, they are also armed with potent toxins. The poisons in their skin are so powerful that local tribes have been known to create deadly darts simply by rubbing them on the frogs’ backs — hence the name.

One might expect that the evolution of such a successful defense would allow these frogs to diversify faster than their relatives and outcompete their kin for resources and habitats — and, according to a study published in the early edition of Proceedings of the National Academy of Sciences this week, their toxins do give them a speciation advantage. But, their defenses don’t come cheap: poisonous frog species also go extinct at a faster rate. Continue reading “Poisonous Problems: Chemical Defenses Come With Evolutionary Cost”

Toxic Toad Eaters Reveal How Evolution Repeats Itself

Bufos marinus, invasive species extraordinaire and one helluva toxic toad. Photo by Chris Ison — Invasive species extraordinaire and one helluva toxic toad. Photo by Chris Ison

At the time, it seemed like the logical thing to do. Australian farmers were desperate. It was the 1930s, and beetles were tearing through their crops, especially sugar cane. Word spread of a toad that loved to gorge itself on the problem pests, which had been successfully brought to Hawaii to manage beetles in sugarcane fields. The Australians could have turned to pesticides, sure, but pesticides are expensive and often harmful to people and the environment. And if the toad could be introduced once, why not again? Why shouldn’t they fix their bug problem once and for all with a harmless little amphibian? So in 1935, two suitcases of cane toads (Rhinella marina; formerly Bufo marinus) arrived in Australia.

Those toads would go on to produce more than 1.5 billion descendants, contending for the title of worst invasive species in history. Continue reading “Toxic Toad Eaters Reveal How Evolution Repeats Itself”

Kelp Gulls Tear Out Baby Seal Eyes So They Can Feast On Their Remains When They Die

A kelp gull waits for an unfortunate pup to die. Photo by Naude Dreyer

I think it’s fairly safe to say that gulls are among the least-loved birds in the world. These loud and annoying seabirds have a disturbing lack of fear of large mammals — including us — and a seemingly insatiable appetite, as any beach picnicker can attest. It’s no wonder that the creators of Finding Nemo portrayed them as mindless feeding machines, the only species in the movie to lack intellect and personality. But they were wrong in at least one respect: while seagulls might be feeding machines, they are far from mindless. Continue reading “Kelp Gulls Tear Out Baby Seal Eyes So They Can Feast On Their Remains When They Die”