Bird Families

Clawed frog (Xenopus laevis)

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Dolphins Inermorostrum xenops as seen by the artist

Robert W. Boessenecker

American paleontologists have discovered fossils of a new species of small dolphins in the southeastern United States, Inermorostrum xenops, who lived about 29 million years ago. Despite belonging to toothed whales, they were toothless; they apparently hunted small fish and cephalopods, which were sucked in with the help of strong lips. Research published in Proceedings of the Royal Society B.

Toothed whales (Odontoceti) Is one of two modern suborders of cetaceans. They have full-fledged teeth, and they use echolocation to communicate with each other and hunt. Toothed whales also include the dolphin family (Delphinidae). Another suborder - baleen whales (Mysticeti) - feed on plankton, filtering it through a whalebone. The suborders split about 34 million years ago. Baleen whales gradually lost their teeth, they were replaced by horny plates - a whalebone, which developed from the gum tissue.

The Oligocene era (34-23 million years ago) was one of the most important periods for cetaceans. At this time, about 40 genera of cetaceans appeared, which differed in the morphology of the "beak" and teeth. It is known that baleen whales of that period fed in several ways: among them were predators, species that fed by sucking in the bottom fauna, species that filtered plankton with the help of a whalebone. Little is known about the food specialization of toothed whale fossils, in part because few fossils of this group have been found so far. The authors of the new study partially filled the gap by describing one of the ancient dolphins.

Paleontologists have described a new species of fossil dolphin from a partially preserved skull. Including the upper jaw and most of the orbital region (surrounding the eyes) have been preserved. Fossils found in the Wondo River in South Carolina. Scientists attributed the dolphin to the xenorophid family (Xenorophidae) - one of the most primitive groups of toothed whales. Xenorophids lived in the southeastern United States during the Oligocene, 33-23 million years ago.

Fossils of Inermorostrum xenops

"In just four million years, the xenops evolved from its toothed whale ancestors into a specialized toothless sucker," explains lead author Robert Boessenecker, a professor at Charleston College.

To trace how food specialization developed in toothed whales, the authors of the study performed a phylogenetic analysis of the "beaks" of ancient toothed whales. It turned out that the xenops, although they were the most ancient, were not the only "suckers" in the suborder. Some species of Oligocene toothed whales have acquired short "beaks" independently of the xenops. In some families of ancient dolphins, "beaks", on the contrary, grew. That is, these species were exclusively engaged in fishing. A possible reason for this diversity, researchers say, was the emergence of the Antarctic circumpolar current in the Middle Oligocene and a concomitant increase in the number of plankton and animals that fed on it. And after the appearance of prey, predators also appeared.

Earlier, researchers found that echolocation, characteristic of modern toothed whales, appeared at the very beginning of the evolution of this suborder, and increased sensitivity to high-frequency sounds arose even earlier.

Clawed frog (Xenopus laevis)

Message Ilya 72 »04 Aug 2014, 21:21

Content temperature: 18-25
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Add or add a description Clawed frog (Xenopus laevis) you can in this thread.
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Photo "Bird-veined Xenops - Xenops rutilans - Xenops Estriado" can be used for personal and commercial purposes according to the conditions of the purchased Royalty-free license. The image is available for download in high quality with resolution up to 2999x4000.

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Xenopus: A naked frog whose genome is mysteriously too human

Once Mother Nature decided to sew a soft toy with funny eyes and a smile on her face. But she somehow did not work with needlework, and as a result, it turned out here THIS. Before us is a faithful assistant to biologists, a friend of all inexperienced amphibian lovers and that same naked frog - clawed frog, she is a xenopus!

The expression on the muzzle of this something is forever frozen between the face of an enthusiastic moron and an enlightened Buddha (I want to believe that there is more Buddha there). Out of harm's way Nature settled the result of its hand-made in Central Africa, but bad people brought the animal to both Europe and America, where the amphibian successfully occupied local water bodies.

Pay attention to the eyes. Looks like the eyes of someone who saw some shit, don't they? These zyrkalki are bulging for a reason: such an arrangement allows you to both find food and track down enemies. Every scoundrel is ready to covet the fat 8 centimeter body of our heroine. The amphibian itself, by the way, drags into its mouth everything that will fit in it: fry, insects and even small fish - what only the clawed frog does not indulge in.

But the eyes are not the only way of orientation in the xenopus. The frog does not justify its belonging to the class of "amphibians" - the animal hardly ever gets out on land. And since she lives in water 24/7, she, like fish, has a lateral line, a special organ of touch. This strip looks as if the animal was sewn from two different pieces, and with crooked seams. But thanks to this organ, the chubby catches the smallest fluctuations in the water.

Despite the creepy appearance, the beast brought a lot of benefits to the biped. The eggs of these frogs turned out to be the most convenient object for research in the field of embryology. Using the example of xenopuses, they study literally everything: how the fetus develops, how the poison and all kinds of carcinogenic substances affect it. They even reveal the signs of individual genes - in how!

“But pardon me, monsieur, why are ordinary lake frogs so bad for these purposes? After all, they are both larger and closer. Vaughn scooped as much as necessary in a ditch with a bucket in the spring, take and experiment as much as you like ”- you say. And to this I will answer that biologists, as in the song, have 5 reasons to use our heroine for experiments.

First: xenopus eggs are quite large. The second is that the resulting tadpoles are almost transparent, since albino frogs were bred in captivity. The filling of the baby is literally visible with the naked eye, which means that you can watch the growth process of each organ offline and without registration! Moreover, biologists move these very organs to different parts of the body! For example, for this tadpole, scientists literally pulled their eyes on the butt. And the most amazing thing is that it was fully functional!

In addition, clawed frogs breed like devils. It is enough to inject the necessary hormone and the pop-eyed cheburek will rivet you 15,000 fresh model objects (eggs)! And it is not expensive to keep xenopuses. Throw it into a clean and warm aquarium, feed it from time to time, and the frog will be happy. These were reasons 3 and 4.

But the last, fifth reason is much deeper and more complex. The fact is that the genome of this frog turned out to be about the same length as that of the sapiens. As if this were not enough, it turned out that huge sections of the genome are completely identical to the human - and there are more coincidences than with other vertebrates. Now it's no surprise that albino frogs look so much like little naked men! These are real amphibious people!

Unpretentious maintenance and incredible fertility made it possible to bring xenopuses out of the gloomy dungeons of laboratories into amateur aquariums. The frog is extremely unpretentious, eats almost everything that you offer and does not require great skills in keeping cold-blooded.

However, this does not mean that the beast can be kept in a basin! Like any pet, the xenopus can get sick and die from improper handling. Their most common ailment is dropsy, from which the amphibian bursts as if not in itself.

But if you provide proper care for the clawed frog, the amphibian toy will delight you with its smile for a long 10-15 years.

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