PoDear

15/08/2022

Materials scientist Derk Joester and colleagues analyzed these teeth using high-energy X-rays from the Advanced Photon Source at Argonne National Laboratory in Lemont, Ill. They discovered that the interface between the teeth and flesh contained nanoparticles of santabarbaraite, an iron-loaded mineral never seen before in a living organism’s body.

These nanoparticles help the underpinnings of the teeth vary in hardness and stiffness by at least a factor of two over distances of just several hundred micrometers — a few times the average width of a human hair. Such variations let these structures bridge the hard and soft parts of the mollusk’s body. Now that santabarbaraite has been found in one organism, the researchers suggest looking for it in insect cuticles and bacteria that sense magnetic fields.

15/08/2022

The hard, magnetic teeth of a leathery red-brown mollusk nicknamed “the wandering meatloaf” possess a rare mineral previously seen only in rocks. The mineral may help the mollusk — the giant Pacific chiton (Cryptochiton stelleri) — meld its soft flesh to the hard teeth it uses for grazing on rocky coastlines, researchers report online May 31 in Proceedings of the National Academy of Sciences.

C. stelleri is the world’s largest chiton, reaching up to roughly 35 centimeters long. It is equipped with several dozen rows of teeth on a slender, flexible, tonguelike appendage called a radula that it uses to scrape algae off rocks. Those teeth are covered in magnetite, the hardest, stiffest known biomineral to date: It’s as much as three times as hard as human enamel and mollusk shells.

11/08/2022

The findings upend what scientists thought they knew about the ancient animals. Scientists have assumed the ancient creatures were herbivores. That’s in part because all six modern species of sloth are confirmed vegetarians, and in part giant ground sloths’ teeth and jaws weren’t adapted for hunting or powerful chewing and tearing (SN: 6/20/16).

But Darwin’s ground sloth could have managed to ingest already-killed meat, Tejada and colleagues say. And that might help solve a long-standing puzzle: the apparent absence of large carnivorous mammals in South America at the time. Darwin’s ground sloth, the researchers add, may have filled a vacant ecological niche: the scavenger who wouldn’t say no to a meaty meal.

11/08/2022

Nitrogen isotopes, different forms of the element, can vary a lot among different food sources as well as between ecosystems. Those isotope values in one amino acid, glutamine, change significantly with diet, increasing the higher the animal is on the food chain. But diet has little impact on the nitrogen values in another amino acid, phenylalanine. By comparing the nitrogen isotopes in the two amino acids found in the sloths’ hair, the researchers were able to eliminate ecosystem effects and zoom in on diets.

The data reveal that while the diet of the Shasta ground slothwas exclusively plant-based, Darwin’s ground sloth was an omnivore, Tejada and colleagues report October 7 in Scientific Reports.

10/08/2022

Muscle breakdown from inactivity or starvation releases compounds made of nitrogen — a crucial element found in muscle building blocks called amino acids. Too much nitrogen can be toxic, so the body normally eliminates the excess through urine in a compound called urea.

Previous work has shown that arctic ground squirrels (Urocitellus parryii) can recycle nitrogen for muscle preservation on their own, without gut microbes’ help (SN: 12/16/20). In the new study, Carey and colleagues tracked where nitrogen went in the bodies of thirteen-lined ground squirrels (Ictidomys tridecemlineatus) using an isotope, a form of the element with a different mass, as a tracer. In hibernating squirrels, nitrogen that had been processed by microbes ended up in skeletal muscle. But animals treated with antibiotics to clear out gut-inhabiting bacteria incorporated less nitrogen into muscle, a sign that the microbes were responsible.

Some gut microbes salvage nitrogen from urea and use it to make amino acids. Hibernating squirrels can then use those amino acids to preserve muscle, the findings suggest.

It seems that to help the creatures stay strong, Carey says, microbes and squirrels come together.

08/08/2022

Mismatched sexes are nothing new for spiders. The group shows the most extreme size differences between the sexes known among land animals, says evolutionary biologist Matjaž Kuntner of the Evolutionary Zoology Lab in Ljubljana, Slovenia. The most dramatic case Kuntner has heard of comes from Arachnura logio scorpion spiders in East Asia, with females 14.8 times the size of the males.

With such extreme size differences, mating conflicts in animals can get violent: females cannibalizing males and so on (SN: 11/13/99). As far as Kuntner knows, however, jorō spiders don’t engage in these “sexually conflicted” extremes. Males being merely half size or thereabouts might explain the relatively peaceful encounters.

When it comes to humans, these spiders don’t bother anybody who doesn’t bother them. But what a spectacle they make. “I’ve got dozens and dozens in my yard,” says ecologist Andy Davis at the University of Georgia in Athens. “One big web can be 3 or 4 feet in diameter.” Jorō spiders have lived in northeastern Georgia since at least 2014.

08/08/2022

Some thumbnail-sized, brown male spiders in Georgia could be miffed if they paid the least attention to humans and our news obsessions.

Recent stories have made much of “giant” jorō spiders invading North America from eastern Asia, some large enough to span your palm. Lemon yellow bands cross their backs. Bright red bits can add drama, and a softer cheesecake yellow highlights the many joints on long black legs.

The showy giants, however, are just the females of Trichonephila clavata. Males hardly get mentioned except for what they’re not: colorful or big. A he-spider hulk at 8 millimeters barely reaches half the length of small females. Even the species nickname ignores the guys. The word jorō, borrowed from Japanese, translates to such unmasculine terms as “courtesan,” “lady-in-waiting” and even “entangling or binding bride.”

01/08/2022

In the past, researchers have used data on land mammals to speculate about their counterparts in the sea. But the few actual measurements of these gas fluctuations in young porpoises in captivity have suggested their metabolic rates are higher than similarly sized land mammals. Captivity, however, might be stressing the animals and driving up their rates.

So Madsen and his colleagues wondered if porpoise breathing rate, something people can reliably count in free-swimming mammals, might give clues to the animals’ total daily energy needs, called the field metabolic rate. To connect breaths with energy use, study coauthor Laia Rojano-Doñate, also at Aarhus, turned to three captive porpoises kept in a net pen in a fjord, where the animals experienced natural ocean temperatures, salinity and water movements.

01/08/2022

01/08/2022