beetles

why-are-there-so-many-species-of-beetles?

Why are there so many species of beetles?

beetles, entomology, insects, Science, syndication / /

The beetles outnumber us —

Diet played a key role in the evolution of the vast beetle family tree.

–

A box of beetles

Caroline Chaboo’s eyes light up when she talks about tortoise beetles. Like gems, they exist in myriad bright colors: shiny blue, red, orange, leaf green and transparent flecked with gold. They’re members of a group of 40,000 species of leaf beetles, the Chrysomelidae, one of the most species-rich branches of the vast beetle order, Coleoptera. “You have your weevils, longhorns, and leaf beetles,” she says. “That’s really the trio that dominates beetle diversity.”

An entomologist at the University of Nebraska, Lincoln, Chaboo has long wondered why the kingdom of life is so skewed toward beetles: The tough-bodied creatures make up about a quarter of all animal species. Many biologists have wondered the same thing, for a long time. “Darwin was a beetle collector,” Chaboo notes.

Despite their kaleidoscopic variety, most beetles share the same three-part body plan. The insects’ ability to fold their flight wings, origami-like, under protective forewings called elytra allows beetles to squeeze into rocky crevices and burrow inside trees. Beetles’ knack for thriving in a large range of microhabitats could also help explain their abundance of species, scientists say.

Enlarge / Despite their kaleidoscopic variety, most beetles share the same three-part body plan. The insects’ ability to fold their flight wings, origami-like, under protective forewings called elytra allows beetles to squeeze into rocky crevices and burrow inside trees. Beetles’ knack for thriving in a large range of microhabitats could also help explain their abundance of species, scientists say.

Of the roughly 1 million named insect species on Earth, about 400,000 are beetles. And that’s just the beetles described so far. Scientists typically describe thousands of new species each year. So—why so many beetle species? “We don’t know the precise answer,” says Chaboo. But clues are emerging.

One hypothesis is that there are lots of them because they’ve been around so long. “Beetles are 350 million years old,” says evolutionary biologist and entomologist Duane McKenna of the University of Memphis in Tennessee. That’s a great deal of time in which existing species can speciate, or split into new, distinct genetic lineages. By way of comparison, modern humans have existed for only about 300,000 years.

Yet just because a group of animals is old doesn’t necessarily mean it will have more species. Some very old groups have very few species. Coelacanth fish, for example, have been swimming in the ocean for approximately 360 million years, reaching a maximum of around 90 species and then declining to the two species known to be living today. Similarly, the lizard-like reptile the tuatara is the only living member of a once globally diverse ancient order of reptiles that originated about 250 million years ago.

Another possible explanation for why beetles are so rich in species is that, in addition to being old, they have unusual staying power. “They have survived at least two mass extinctions,” says Cristian Beza-Beza, a University of Minnesota postdoctoral fellow. Indeed, a 2015 study using fossil beetles to explore extinctions as far back as the Permian 284 million years ago concluded that lack of extinction may be at least as important as diversification for explaining beetle species abundance. In past eras, at least, beetles have demonstrated a striking ability to shift their ranges in response to climate change, and this may explain their extinction resilience, the authors hypothesize.

Why are there so many species of beetles? Read More »

scientists-get-dung-beetles-to-collect-dna-samples-for-biodiversity-studies

Scientists get dung beetles to collect DNA samples for biodiversity studies

beetles, biodiversity, Biology, DNA, peru, Science / /

High tech/low tech solutions —

Researchers are sequencing the DNA of wildlife using dung beetle stomach contents.

–

Image of forest-covered hillsides and a river winding through the jungle.

Enlarge / The Manu area of Peru contains a number of ecological zones.

Peru’s Manu Biosphere Reserve is the largest rainforest reserve in the world and one of the most biodiverse spots on the planet. Manu is a UNESCO-protected area the size of Connecticut and Delaware combined, covering an area where the Amazon River Basin meets the Andes Mountain Range. This combination forms a series of unique ecosystems, where species unknown to science are discovered every year. The remoteness of the region has helped preserve its biodiversity but adds to the challenges faced by the scientists who are drawn to study it.

Trapping wildlife for research in the dense jungle is impractical, especially considering the great distances researchers have to travel within Manu, either through the forest or on the waterways. It’s an expensive proposition that inevitably exposes the trapped animals to some amount of risk. Trapping rare and endangered animals is even more difficult and comes with significant risks to the animal.

Trapping beetles, however, does not pose the same challenges. They’re easy to catch, easy to transport, and, most importantly, carry the DNA of many animals in and on them. Any animal a biologist could hope to study leaves tracks and droppings in the forest, and the beetles make a living by cleaning that stuff up.

Beetles as DNA collectors

Beetles are plentiful in the rainforest, and the species that Alejandro Lopera-Toro’s team studies are not endangered. The study does mean that the beetles are killed, but overall, the effect on the ecosystem is minimal.

According to Peruvian biologist and team member Patricia Reyes, “The impact depends on the abundance and reproductive cycle of each species. Reducing the beetle population could have an effect on their predators, such as birds, reptiles, and other insects. The health of the forest depends on the beetles’ function to break down organic matter and disperse seeds. Despite not having found any effect on the ecosystem so far, we still limit how many individual beetles we collect and identify sensitive areas where collecting is prohibited. We promote sustainable methods of collection to mitigate possible impacts in the future.”

Getting beetles to do the work of collecting DNA for researchers took some adjustments. The traps normally used to study beetles cause the beetles to fall into a chemical solution, which kills and preserves them until they are collected. However, those traps contaminate the beetle’s stomach contents, making the DNA unusable. Lopera-Toro’s traps keep them alive, protecting the delicate strands of DNA that the beetles have worked so hard to collect. He and his team also go out into the forest to collect live beetles by hand, carefully recording the time and place each one was collected. Starting in July 2022, the team has been collecting dung beetles across Manu’s diverse ecosystems up and down the altitude gradient, from 500 to 3,500 meters above sea level.

In addition to obtaining DNA from the beetles, researchers also use them as test subjects for metabolic studies.

Enlarge / In addition to obtaining DNA from the beetles, researchers also use them as test subjects for metabolic studies.

Elena Chaboteaux

The Manu Biological Station team is using Nanopore technology to sequence the DNA found in the beetles’ stomachs, with the goal of finding out what animals are represented there. They specifically targeted dung beetles because their feeding habits depend on the feces left by larger animals. The main advantage to the Nanopore minION device is that it can separate long lengths of DNA on-site. “Long nanopore sequencing reads provide enhanced species identification, while real-time data analysis delivers immediate access to results, whether in the field or in the lab,” according to the Nanopore website.

Biologist Juliana Morales acknowledges that Nanopore still has a high rate of error, though as this new technology is refined, that issue is continually decreasing. For the purposes of the Manu Biological Station team, the margin of error is a price they’re willing to pay to have devices they can use in the rainforest. Since they’re not studying one specific species, but rather building a database of the species present in the region, they don’t need to get every nucleotide correct to be able to identify the species. They do, however, need a strand long enough to differentiate between a common woolly monkey and a yellow-tailed woolly monkey.

Though the researchers prefer to sequence DNA on-site with Nanopore minION devices, when they have more than a dozen samples to analyze, they send them to the University of Guelph in Ontario, Canada. It’s a logistical nightmare to send samples from the Peruvian jungle to Canada, but Lopera-Toro says it’s worth it. “The University of Guelph can process hundreds of DNA samples per day. I’m lucky if we can process 10 samples a day at the [Manu] lab.”

In the most recent batch of 76 samples, they analyzed the stomach contents of 27 species from 11 genera of beetles. From those 76 samples, they identified DNA of howler monkeys, spider monkeys, red brocket deer, night monkeys, peccaries, mouse opossum, Rufous-breasted wood quail, and two species of armadillos. Oddly, the beetles had also eaten about a dozen species of fruit, and one had consumed pollen from a tropical plant called syngonium.

The implications could be vast. “The dung beetle that ate the jaguar’s excrement will tell us not only the DNA of the jaguar but also what the jaguar is eating,” said Lopera-Toro. “If the jaguar kills a peccary and eats 80 percent of the peccary, beetles will eat some of the other 20 percent. If a beetle walks over a jaguar print or saliva, there could be traces of jaguar DNA on the beetle. We analyze the stomach contents and the outside of the beetle. We have an endless number of options, opportunities, and questions we can answer from studying these small insects. We can see the bigger picture of what is happening in the jungle.”

Scientists get dung beetles to collect DNA samples for biodiversity studies Read More »

getting-to-the-bottom-of-how-red-flour-beetles-absorb-water-through-their-butts

Getting to the bottom of how red flour beetles absorb water through their butts

12 days of Christmas, agricultural sciences, animals, beetles, Biology, Biomechanics, genomes, Genomics, red flour beetle, Science / /

On the third day of Christmas —

A unique group of cells pumps water into the kidneys to help harvest moisture from the air.

–

Who <em>doesn’t</em> thrill to the sight of a microscopic cross-section of a beetle’s rectum? You’re welcome.” src=”https://cdn.arstechnica.net/wp-content/uploads/2023/03/beetle-butt-TOP-800×536.jpg”></img><figcaption> <p><a data-height=Enlarge / Who doesn’t thrill to the sight of a microscopic cross-section of a beetle’s rectum? You’re welcome.

Kenneth Veland Halberg

There’s rarely time to write about every cool science-y story that comes our way. So this year, we’re once again running a special Twelve Days of Christmas series of posts, highlighting one science story that fell through the cracks in 2023, each day from December 25 through January 5. Today: red flour beetles can use their butts to suck water from the air, helping them survive in extremely dry environments. Scientists are honing in on the molecular mechanisms behind this unique ability.

The humble red flour beetle (Tribolium castaneum) is a common pantry pest feeding on stored grains, flour, cereals, pasta, biscuits, beans, and nuts. It’s a remarkably hardy creature, capable of surviving in harsh arid environments due to its unique ability to extract fluid not just from grains and other food sources, but also from the air. It does this by opening its rectum when the humidity of the atmosphere is relatively high, absorbing moisture through that opening and converting it into fluid that is then used to hydrate the rest of the body.

Scientists have known about this ability for more than a century, but biologists are finally starting to get to the bottom (ahem) of the underlying molecular mechanisms, according to a March paper published in the Proceedings of the National Academies of Science. This will inform future research on how to interrupt this hydration process to better keep red flour beetle populations in check, since they are highly resistant to pesticides. They can also withstand even higher levels of radiation than the cockroach.

There are about 400,000 known species of beetle roaming the planet although scientists believe there could be well over a million. Each year, as much as 20 percent of the world’s grain stores are contaminated by red flour beetles, grain weevils, Colorado potato beetles, and confused flour beetles, particularly in developing countries. Red flour beetles in particular are a popular model organism for scientific research on development and functional genomics. The entire genome was sequenced in 2008, and the beetle shares between 10,000 and 15,000 genes with the fruit fly (Drosophila), another workhorse of genetics research. But the beetle’s development cycle more closely resembles that of other insects by comparison.

Food security in developing nations is particularly affected by animal species like the red flour beetle which has specialized in surviving in extremely dry environments, granaries included, for thousands of years.

Enlarge / Food security in developing nations is particularly affected by animal species like the red flour beetle which has specialized in surviving in extremely dry environments, granaries included, for thousands of years.

Kenneth Halberg

The rectums of most mammals and insects absorb any remaining nutrients and water from the body’s waste products prior to defecation. But the red flour beetle’s rectum is a model of ultra-efficiency in that regard. The beetle can generate extremely high salt concentrations in its kidneys, enabling it to extract all the water from its own feces and recycle that moisture back into its body.

“A beetle can go through an entire life cycle without drinking liquid water,” said co-author Kenneth Veland Halberg, a biologist at the University of Copenhagen. “This is because of their modified rectum and closely applied kidneys, which together make a multi-organ system that is highly specialized in extracting water from the food that they eat and from the air around them. In fact, it happens so effectively that the stool samples we have examined were completely dry and without any trace of water.” The entire rectal structure is encased in a perinephric membrane.

Halberg et al. took took scanning electron microscopy images of the beetle’s rectal structure. They also took tissue samples and extracted RNA from lab-grown red flour beetles, then used a new resource called BeetleAtlas for their gene expression analysis, hunting for any relevant genes.

One particular gene was expressed sixty times more in the rectum than any other. Halberg and his team eventually honed in a group of secondary cells between the beetle’s kidneys and circulatory system called leptophragmata. This finding supports prior studies that suggested these cells might be relevant since they are the only cells that interrupt the perinephric membrane, thereby enabling critical transport of potassium chloride. Translation: the cells pump salts into the kidneys to better harvest moisture from its feces or from the air.

Model of the beetle's inside and how it extracts water from the air.

Enlarge / Model of the beetle’s inside and how it extracts water from the air.

Kenneth Halberg

The next step is to build on these new insights to figure out how to interrupt the beetle’s unique hydration process at the molecular level, perhaps by designing molecules that can do so. Those molecules could then be incorporated into more eco-friendly pesticides that target the red flour beetle and similar pests while not harming more beneficial insects like bees.

“Now we understand exactly which genes, cells and molecules are at play in the beetle when it absorbs water in its rectum. This means that we suddenly have a grip on how to disrupt these very efficient processes by, for example, developing insecticides that target this function and in doing so, kill the beetle,” said Halberg. “There is twenty times as much insect biomass on Earth than that of humans. They play key roles in most food webs and have a huge impact on virtually all ecosystems and on human health. So, we need to understand them better.”

DOI: PNAS, 2023. 10.1073/pnas.2217084120  (About DOIs).

Getting to the bottom of how red flour beetles absorb water through their butts Read More »