Tag Archives: Feast

Killer Whales Surround Great White Sharks and Feast on Their Livers

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Killer whales execute skilled hunting techniques to bring juvenile great white sharks to the water’s surface.

Marco Villegas

Killer whales in the Gulf of California have adopted a sophisticated hunting method to target juvenile great white sharks: they turn them upside down to immobilize them. This finding implies there may be a previously unnoticed pod of orcas in the area that specialize in hunting sharks.

Only a limited number of killer whale populations are documented to consume sharks, and even fewer have been observed preying on great white sharks (carcharodon carcharius). Historically, killer whales (Orcinus orca) off the coast of San Francisco have been linked to a recorded incident involving a great white shark in 1997, and a carcass recovered near Australia revealed signs of an orca attack, documented in 2023. Until recently, only one instance of a killer whale preying on a young great white shark had been noted, and that was in South Africa.

Jesus Eric Higuera-Rivas, an independent marine biologist from Mexico, along with colleagues, captured video footage of killer whales hunting juvenile great white sharks on two occasions in the Gulf of California. The initial footage, taken in August 2020, depicted five female killer whales collaboratively pushing a juvenile great white to the surface. “The killer whale was attempting to ram the great white and flip it over,” Higuera-Rivas remarked.

This tactic induced a temporary state of paralysis in the shark, known as tonic immobility. The orcas also managed to consume the energy-rich liver of the shark, sharing it among themselves. Shortly thereafter, the pod repeated their attack on another young great white shark. In August 2022, another group of five killer whales exhibited the same hunting strategy against juvenile great whites in the identical location.

Some of the killer whales involved in the first incident were identified as those previously seen hunting whale sharks and bull sharks. However, the video from the second incident was insufficiently clear to confirm if those were the same orcas. “But it’s highly probable,” says Higuera-Rivas.

The hunting behaviors of killer whale populations differ significantly based on their habitat. “Orcas are like hunting machines, akin to snipers. They employ specific strategies tailored to their prey,” Higuera-Rivas explains. These observations indicate that the killer whales in question may be part of an unrecognized group of shark hunters.

“This provides another example of a distinct feeding strategy, likely not shared by other orca groups globally,” states Andrew Trites from the University of British Columbia, Canada. However, further research is necessary for conclusive evidence, as these killer whales might descend from Pacific Northwest populations that hunt different shark species.

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Source: www.newscientist.com

Charming Maniacs in the Wild: Why Does This Adorable Sea Slug Feast on Sunlight?

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Locating one of the ocean’s most charming mollusks requires a diver with exceptionally keen vision. This tiny sea slug, Costa Sierra Crosimae—commonly referred to as a leaf sheep—reaches only a few centimeters in length, approximately the size of a fingernail. Their exquisite camouflage makes them hard to spot.

Their vibrant green bodies blend seamlessly with the seaweed they inhabit, which also happens to be their primary food source. An incredible transformation occurs when they consume it.

Similar to terrestrial plants, seaweed contains small structures called chloroplasts within its cells, which facilitate the process of photosynthesis. These chloroplasts harness sunlight energy to convert carbon dioxide into sugars.

When the leaf sheep feed on seaweed, akin to sheep grazing in a meadow, they can digest the sugars they consume. Alternatively, they can retain the entire chloroplasts without damaging them and incorporate them into their bodies for later use.

The features along the back of the leaf sheep resemble small leaves and are known as cerata. Each ceratum houses an extension of the sea slug’s digestive system, filled with chloroplasts, giving it a textured appearance.

Remarkably, these engulfed chloroplasts continue to photosynthesize, generating additional sugars. Therefore, as long as these sea slugs dwell in shallow tropical waters with abundant sunlight, they have a sustainable food source.

The scientist who first discovered this species in the early 1990s on Japan’s Kuroshima Island named it Black Himae.

Since then, divers have been diligently searching for the specific type of seaweed that these leaf sheep prefer, which is exclusively Avrainvillea green algae. These delightful sea slugs have been located in Indonesia and the Philippines.

Costasiella Nudibranch (Sheep Nudibranch) can be found in the Philippines and Indonesia. – Photo Credit: Getty Images

Like other sea slugs that maintain various seaweed species, leaf sheep lay their eggs in a meticulous helix, allowing them to hatch into larvae that drift through the water. Initially, the young sea slugs possess small shells before eventually discarding them to live shell-free.

The process of adopting chloroplasts from seaweed is known as keratoplasia, which can be observed in many other types of ocean slugs. For example, the green Elysian sea slugs (found along the British and other European coasts, Elysia viridis) utilize Codium seaweed (also known as the dead man’s fingers).

While these slugs lack the leaf-like projections seen in leaf sheep, they possess two wing-like extensions that unfold to maximize sunlight absorption for their self-sustaining food factories.

In this position, these marine slugs resemble drifting leaves. Another species, Elysia marginata, not only captures chloroplasts but also performs astonishing feats. Similar to geckos that shed their tails, these sea slugs can separate their heads from their bodies.

This process takes several hours, and while the detached body can survive for days, it does not regenerate a new head. Meanwhile, the original head roams for a while before growing a new body.

This behavior of severing the head may have evolved as a drastic but effective method for eliminating parasite-infected bodies.

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Source: www.sciencefocus.com

The Final Feast of the Trilobite – Sciworthy

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trilobite are a diverse group of marine animals that lived between 540 and 250 million years ago. They were some of the oldest and longest-lived arthropods known. Trilobites are named for the shape of their bodies, which are characterized by a hard exoskeleton divided into three lobes.

Paleontologists have described more than 20,000 different species of trilobites. Lifestyle and eating behavior. Some burrowed into the ocean floor, while others floated or swam freely in the ocean. But everything scientists know (or think they know) about what trilobites ate; indirect evidencelike them Intestinal shape and size. Researchers have never before discovered a fully-fed trilobite fossil. until now…

A group of researchers from the Czech Republic and Sweden recently reported a complete fossil of a trilobite. Bohemorichas Incora The intestinal contents remain intact. They discovered this unique specimen in the Šárka Formation in the Prague Basin of the Czech Republic. It died 465 million years ago lying on its belly on the ocean floor, rapidly becoming encased in a mass of silica. nodules. The researchers explained that the silica nodules prevented the carcass from being crushed during burial, preserving the entire fossil in three dimensions for millions of years.

The research team used a 3D imaging technique called . micro tomography Let's take a look inside the intestines of trilobites. They used this method to create a series of superimposed slice-by-slice images of the fossil's interior, which a computer program knitted into his three-dimensional shape. Scientists traditionally used his X-rays for microscopic tomography, but this team used a special energy source. synchrotron radiation, increase image resolution and contrast. Synchrotron radiation is high-intensity light produced by electrons traveling at nearly the speed of light in a circular accelerator. synchrotron. They combined this method with another type of imaging known as . Propagation phase contrast imagingwhich further enhances the contrast between normal light-absorbing soft tissues as well.

The researchers discovered that the trilobite's intestines were completely filled with shell fragments made of calcium carbonate. They determined that most of the shells belonged to small crustaceans, about the size of ants. ostracod. Some of the shell fragments were from larger, two-shelled organisms, similar to bivalves or bivalves, while others were from a single organism, similar to starfish. All of these creatures lived in the mud on the ocean floor, suggesting that the trilobites were feeding on them as they ran along the ocean floor. Because the trilobite ate several types of shelled creatures, the researchers hypothesized that it was a scavenger that scavenged indiscriminately on whatever it encountered, rather than a selective predator.

The researchers also noted that the trilobite's intestinal shell had sharp edges and no signs of etching. The researchers interpreted this to mean that the pH of the trilobite's digestive tract was neutral or alkaline, since if the intestine is acidic, like humans and most mammals, the shell will begin to dissolve. The researchers explained that enzymes that help animals digest food are very sensitive to pH. Therefore, this evidence suggests that trilobites had enzymes similar to other organisms with neutral or alkaline digestive systems. Living examples of these organisms include crustaceans such as shrimp and lobsters, and chelicerae such as spiders and scorpions.

Finally, the researchers found a series of small tunnels dug into the trilobite's remains. This indicates that the trilobites fell prey to their own scavengers after death, before becoming encased in silica. They found the most concentrated set of burrows near the trilobite's head, which appeared to be the area of ​​most intense feeding. They also found several burrows in the lower part of the trilobite's body, but none of them entered the digestive tract. In other words, the scavengers avoided the trilobite's intestines entirely. The researchers suggested that if intestinal enzymes continued to digest the animal's last meal after it died, the intestine could have remained toxic for some time.

The researchers concluded that the 3D specimen was: Bohemorichas Incola They said this provides the best knowledge to date of the feeding habits of trilobites, including what they eat and how they digest it. They also suggested that the physiological properties of this particular trilobite may mean that a near-neutral pH gut is a feature of most primitive arthropods. However, they also noted that few scientists have studied how gut pH affects digestion in living arthropods, so further research is needed to test this hypothesis. .


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Source: sciworthy.com