Martien van Beekveld made this video in Schijndel in the Netherlands.
This 20 August 2018 video from the USA says about itself:
5 Iconic Animals of Yellowstone | Nat Geo Wild
Yellowstone National Park may be best known for Old Faithful geyser and other unique geothermal features, but it’s also home to the largest concentration of mammals in the lower 48 states. Learn about wolves, elk, grizzly bears, bison, and river otters that call Yellowstone home.
This 8 August 2018 video from the USA says about itself:
See Foxes LIVE in Yellowstone | Yellowstone Live
We’re LIVE in West Yellowstone, MT with an adorable fox.
This 6 August 2018 video from the USA says about itself:
We’re LIVE in West Yellowstone, MT with a snake and a salamander.
This 5 August 2018 video from the USA says about itself:
We’re LIVE in Yellowstone with a bald eagle.
A Montana State University study of Yellowstone National Park and the surrounding area shows that increased population and density, as well as a changing climate, are affecting the overall ecological health of the region: here.
This May 2017 video says about itself:
Lizard Regenerates Tail; Time Lapse!
In this video you see footage of a [leopard] gecko who regenerates his tail. This is pretty cool to see so we thought we would put together a compilation of some of the best photos and images.
However, some animals are even better at regenerating tails.
By Leah Rosenbaum, 12:30pm, August 17, 2018:
How salamanders can regrow nearly complete tails but lizards can’t
Neural stem cells in the spinal cord prevent the reptiles from regenerating nerve cells
Salamanders and lizards can both regrow their tails, but not to equal perfection.
While a regenerated salamander tail closely mimics the original, bone and all, a lizard’s replacement is filled with cartilage and lacks nerve cells. That contrast is due to differences between stem cells in the animals’ spinal cords, researchers report online August 13 in Proceedings of the National Academy of Sciences.
When a salamander loses its tail, neural stem cells in the creature’s spinal cord can develop into any type of nervous system cell, including nerve cells, or neurons. But through evolution, lizard neural stem cells “have lost this ability”, says study coauthor Thomas Lozito, a biologist at the University of Pittsburgh. Lizards, while they can regrow cartilage and skin, cannot regenerate neurons, the researchers found.
Lozito and colleagues studied neural stem cells from the axolotl salamander (Ambystoma mexicanum) and from two lizard species — the green anole (Anolis carolinensis) and the mourning gecko (Lepidodactylus lugubris). The team also wondered if the lizard stem cells themselves weren’t capable of developing into neurons or if there was something about the environment of the lizard tail that prevented their regrowth. So the researchers implanted salamander neural stem cells into five gecko tail stumps. Some of the cells became neurons in the regrown tails, showing that the lizard stem cells were the problem.
The finding suggests that scientists would have to alter only the lizard stem cells instead of other parts of the tail to regrow a more complete appendage.
How lizards lost their ability to regenerate neurons and salamanders didn’t remains a mystery (SN: 11/28/15, p. 12). Scientists know that species’ places on the evolutionary tree have something to do with organisms’ ability to regrow body parts. “The more complex the species are, the less they can regenerate”, says developmental biologist Katharina Lust of the Research Institute of Molecular Pathology in Vienna, who was not involved in the study. Reptiles such as lizards are more complex organisms than amphibians like salamanders.
The researchers plan to use CRISPR/Cas9 gene editing to see if lizard neural stem cells can be modified to regenerate a perfect tail. Ultimately, the team hopes to one day coax stem cells in mammals to regenerate body parts.
“My goal is to make the first mouse that can regenerate its tail”, Lozito says. “We’re kind of using lizards as a stepping-stone.”
This April 2016 video from the USA says about itself:
Parthenogenesis, or virgin births, is an amazing process where females of some species can produce offspring without a male fertilizing her eggs.
In this video we explore how parthenogenesis is done on a cellular and chromosomal level.
There are three main methods parthenogenesis is done. Automictic, Apomictic, and Haploid. I go over in great detail how each of these different methods is done on a chromosomal level. If you are unfamiliar with meiosis and how we get our reproductive cells (sperm and eggs) I would suggest quickly looking it over somewhere online, but I do go over it briefly in the video. …
Special thanks to Charles Cole from the American Museum of Natural History for answering my questions about the whiptail lizards!
From Ohio State University in the USA:
Unisexual salamander evolution: A long, strange trip
Study finds surprisingly long stretches of celibacy
July 26, 2018
The reproductive history of the unisexual, ladies-only salamander species is full of evolutionary surprises.
In a new study, a team of researchers at The Ohio State University traced the animals’ genetic history back 3.4 million years and found some head-scratching details — primarily that they seem to have gone for millions of years without any DNA contributions from male salamanders and still have managed to persist. The research appears in the journal Evolution.
First, a bit about the unisexual Ambystoma salamander: They’re female, and they reproduce mainly through cloning and the occasional theft of another salamander species’ sperm, which the males of sexual species deposit on leaves and twigs and the like. When this happens, it stimulates egg production and the borrowed species’ genetic information is sometimes incorporated into the genome of the unisexual salamanders, a process called kleptogenesis.
Scientists who study these amphibians and their relatives, which are also called mole salamanders, have theorized that the theft of sperm is part of what has kept the unisexuals around so long. If all they ever did was clone themselves, biologists reason, they’d be vulnerable to all kinds of problems that unfold when you don’t mix up the DNA pool and would disappear from the earth fairly quickly.
Going into the study, the Ohio State team figured this sperm-borrowing happened with regularity throughout history, said study co-author H. Lisle Gibbs, a professor of evolution, ecology and organismal biology.
But findings revealed that the salamanders rarely dip into the other-species pool for genetic variation.
“This research shows that millions of years went by where they weren’t taking DNA from other species, and then there were short bursts where they did it more frequently”, said Rob Denton, who led the project as an Ohio State graduate student and is currently a postdoctoral researcher at the University of Connecticut.
“Surprisingly, it doesn’t look like they’re suffering any ill genetic effects. It’s a mysterious scenario that an animal can avoid sexual reproduction for millions of years and not suffer the consequences of that.”
Using newly available technologies and a novel and complex approach to sequence and evaluate about 100 DNA samples from the salamanders, the Ohio State researchers developed a genetic blueprint for what unfolded in the last 3.4 million years.
“When interbreeding happens, or there are adaptations to new changing environmental conditions, that all gets captured in the patterns of their genetic variation,” Denton said.
Under normal circumstances in nature, one would expect these salamanders to be long-gone, Gibbs said.
“Most asexual lineages blink out after 100,000 years. We think these have been around for 5 million years,” he said.
A puzzling detail that emerged in the study is that the sampling of DNA from other species appears to have increased in frequency in recent times, he said.
“The reasons for this are sort of tantalizing, and make you wonder: Did this happen because of some sort of environmental change or specific interactions with other species? We don’t know those answers but now we have some provocative questions”, Denton said.
He also noted that the evolutionary history of the unisexual salamander is far different from the history of other unisexual species, such as Amazon mollies.
“The mollies live fast and die hard, in less than a year, but these salamanders live slow and for long periods of time, into their 20s and 30s. And they reproduce every few years”, Denton said.
“These salamanders are just sort of plodding through evolutionary time doing strange and surprising things.”
The researchers noted that the study looked only at salamander DNA samples from Ohio and Michigan, so it’s unclear if the same patterns would be seen throughout Eastern North America and Canada, where the unisexual Ambystoma is also common.
Gibbs said it’s possible that this research could inform other areas of study, including plant science, because many plants are — like the unisexual salamanders — polyploid organisms. That means that they have more than two sets of chromosomes.
“If we can find patterns in common with these plants and animals, it would help us understand how these organisms evolve and how the molecular machinery of species with more than two sets of chromosomes works,” Gibbs said.
This 14 June 2018 video says about itself:
From the Florida Museum of Natural History in the USA:
Amber fossils provide oldest evidence of frogs in wet, tropical forests
June 14, 2018
About 99 million years ago, a tiny juvenile frog in present-day Myanmar was suddenly trapped in sap with a beetle, perhaps its intended next meal.
Unlucky for the frog, but lucky for science.
An extinct species now named Electrorana limoae, it’s one of four fossils that provide the earliest direct evidence of frogs living in wet, tropical forests and are the oldest-known examples of frogs preserved in amber.
“It’s almost unheard of to get a fossil frog from this time period that is small, has preservation of small bones and is mostly three-dimensional. This is pretty special,” said David Blackburn, study co-author and the associate curator of herpetology at the Florida Museum of Natural History. “But what’s most exciting about this animal is its context. These frogs were part of a tropical ecosystem that, in some ways, might not have been that different to what we find today — minus the dinosaurs.”
The findings and species description were published today in Nature’s Scientific Reports.
Frogs have been around for at least 200 million years, but glimpsing their early heyday is tough. Often small and lightly built, frogs don’t tend to preserve well. The frog fossil record skews toward more robust species from arid, seasonal environments, although the bulk of frog diversity today lives in tropical forests.
“Ask any kid what lives in a rainforest, and frogs are on the list”, Blackburn said. “But surprisingly, we have almost nothing from the fossil record to say that’s a longstanding association.”
The amber deposits of northern Myanmar in Southeast Asia provide a unique record of ancient forest ecosystems, with fossil evidence of mosses, bamboo-like plants, aquatic spiders and velvet worms. The discovery of Electrorana and the other fossils, the first frogs to be recovered from these deposits, help add to our understanding of frogs in the Cretaceous period, showing they have inhabited wet, tropical forests for at least 99 million years.
Frogs in amber are quite rare, with previous examples found in the Dominican Republic and Mexico and dating back only about 40 million and 25 million years, respectively.
Less than an inch long, Electrorana is the most well-preserved of the group. Clearly visible in the amber are the frog’s skull, its forelimbs, part of its backbone, a partial hind limb and the unidentified beetle. The other amber fossils contain two hands and an imprint of a frog that likely decayed inside the resin.
But Electrorana raises more questions than it answers, Blackburn said.
Many characteristics herpetologists use to discern details of a frog’s life history and determine how it’s related to other frogs — wrist bones, the pelvis, hip bones, the inner ear, the top of the backbone — are either missing or were not yet fully developed in the juvenile frog.
The existing bones provide clues about Electrorana’s possible living relatives, Blackburn said, but the results are puzzling: Species that have similar features include fire-bellied toads and midwife toads — Eurasian species that live in temperate, not tropical, ecosystems.
Gathering CT skeletal data for both living and extinct frogs, one of Blackburn’s long-term projects, could help illuminate ancient evolutionary relationships, possibly clarifying how Electrorana fits into the frog tree of life.
In the meantime, Blackburn nurtures the hope that other frogs in amber will be discovered, making Electrorana more than a one-hit wonder.
“We don’t have a lot of single-species frog communities in forests. It seems extremely unlikely that there’s only one. There could be a lot more fossils coming.”
In a new study, researchers have investigated how the endocrine-disrupting substance linuron affects reproduction in the West African clawed frog, Xenopus tropicalis. The scientists found that linuron, which is used as a pesticicide, impaired the males’ fertility, and that tadpoles developed ovaries instead of testicles to a greater extent, which caused a female-biased sex ratio: here.