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Science

These beetles tuck symbiotic bacteria in “back pockets” during metamorphosis

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Enlarge / Certain species of beetle have evolved unusual “back pockets” to safely house symbiotic bacteria during metamorphosis—the only known instance of this among insects.

Certain species of beetle have evolved unusual “back pockets” to safely house symbiotic bacteria during metamorphosis—the only known instance of this among insects. It’s part of a mutually beneficial arrangement, since the bacteria protect vulnerable larvae and pupae from fungi. Scientists have also determined that only adult females retain these symbiotic bacteria, shuffling the populations out of those back pockets via friction to the genital area as they emerge from their pupae, according to a new paper published in the journal Frontiers in Physiology.

“We show how an insect can maintain beneficial microbial partners despite the drastic rearrangements of body structures that occur during metamorphosis,” said co-author Laura V. Flórez of the University of Copenhagen. “By modifying unique ‘pockets’ on their backs, Lagria beetles manage to keep their protective symbionts and facilitate their relocation during pupation to newly developed adult organs.”

There are many examples of microbial symbionts in nature. For instance, the Hawaiian bobtail squid has a built-in flashlight to help the creature navigate those murky nighttime waters, hunt for prey, and hide from predators in turn. It’s a special organ on the underside, a convenient little cavity that houses colonies of bacteria, Vibrio fischeri. Once that bacterial colony reaches a critical threshold, they all begin to glow, serving as a light source for the squid. Aphids, tubeworms, digger wasps, cereal weevils, and bean bugs have also evolved symbiotic relationships with microbes for various purposes.

And then there are beetles. Beetles are distinguished from other insects by front wings that harden into wing cases called elytra. Beetles undergo complete metamorphosis, i.e., overall bodily reorganization over the course of several developmental stages: egg to larva, to pupa, to the emergence of an adult from that pupal stage. So any symbiotic bacteria need to adapt accordingly during those developmental stages.

The current study focuses on two beetle species in particular: Lagria hirta (L. hirta) and Lagria villosa (L. villosa), both of which host a community of microbial symbionts throughout their life cycle. L. villosa‘s symbionts are dominated by one particular strain of Burkholderia bacteria that has lost the ability to be motile and probably could not survive for long outside their host beetles. Flórez and her research colleagues at Johannes Gutenberg University in Mainz, Germany, wanted to learn more about how the beetles maintain and protect their symbionts throughout metamorphosis.

An animated 3D micro CT scan of a pupa showing back pockets housing symbiotic bacteria.https://cdn.arstechnica.net/wp-content/uploads/2022/09/beetle-video-1.mp4?_=1

An animated 3D micro CT scan of a pupa showing back pockets housing symbiotic bacteria.

The team collected L. hirta beetles in Germany in 2020, rearing them in an outdoor terrarium to simulate natural conditions. The offspring were collected in 2021. The L. villosa specimens were collected in Brazil in 2019 and reared in plastic containers in a climate chamber. Then the researchers compared the concentrations of symbiotic bacteria and the morphological structure of exoskeletons in males and females.

They found that the beetles had three two-lobed protective pockets at the back of the thorax during the larval and pupal stages to house symbionts. Female beetles also hosted symbionts between bristles at the back of the head. But adult males lost their symbionts, while the bacterial populations shifted to the genital area in adult females. Flórez et al. concluded that there had to be a mechanism for the relocation of the symbionts on the outer surface—especially for those bacteria species that lacked motility—and thought friction might be the key.

To test this hypothesis, five early L. villosa pupae were inoculated with fluorescent beads to simulate transmission of the symbiotic bacteria. Two of the female adults that emerged were carefully dissected, with images taken at every step to track the location of the beads. A male adult was also dissected as a control.

The results confirmed their hypothesis. “The symbionts go from the highly exposed egg surface to colonize the pockets on the back of the larvae and pupae,” said co-author Rebekka S. Janke, a graduate student at Johannes Gutenberg University in Mainz. “Finally, they end up in specialized glands associated with the reproductive system of adult females.” When the adult female lays her eggs, those symbiotic bacteria get squeezed out of the glands and deposited on the eggs’ surface, protecting them throughout metamorphosis, and the cycle of life starts all over again.

That explains why only the adult females retain their symbionts into adulthood. “In the adult stage, the main purpose of the symbiotic organs seems to be to enable successful transmission onto the egg stage and to the next generation,” said Flórez. “Since only females lay eggs, male adults do not need to carry these potentially costly symbionts and are a dead-end for the bacteria.”

DOI: Frontiers in Physiology, 2022. 10.3389/fphys.2022.979200  (About DOIs).

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Science

Scientists Found Superworms That Love Eating Styrofoam, And It Could Be a Good Thing

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Packing material, disposable cutlery, CD cases: Polystyrene is among the most common forms of plastic, but recycling it isn’t easy and the vast majority ends up in landfills or finds its way to the oceans where it threatens marine life.

 

Scientists at Australia’s University of Queensland have now discovered that superworms – the larvae of Zophobas morio darkling beetles – are eager to dine on the substance, and their gut enzymes could hold the key to higher recycling rates.

Chris Rinke, who led a study that was published in the journal Microbial Genomics on Thursday, told AFP previous reports had shown that tiny waxworms and mealworms (which are also beetle larvae) had a good track record when it came to eating plastic, “so we hypothesized that the much larger superworms can eat even more.”

Superworms grow up to two inches (five centimeters) and are bred as a food source for reptiles and birds, or even for humans in countries such as Thailand and Mexico.

Rinke and his team fed superworms different diets over a three week period, with some given polystyrene foam, commonly known as styrofoam, some bran, and others not fed at all.

“We confirmed that superworms can survive on a sole polystyrene diet, and even gain a small amount of weight – compared to a starvation control group – which suggests that the worms can gain energy from eating polystyrene,” he said.

Polystyrene in the gut of a worm. (University of Queensland)

Although the polystyrene-reared superworms completed their life cycle, becoming pupae and then fully developed adult beetles, tests revealed a loss of microbial diversity in their guts and potential pathogens.

These findings suggested that while the bugs can survive on polystyrene, it is not a nutritious diet and impacts their health.

Next, the team used a technique called metagenomics to analyze the microbial gut community and find which gene-encoded enzymes were involved in degrading the plastic.

Bio-upcycling

One way to put the findings to use would be to provide superworms with food waste or agricultural bioproducts to consume alongside polystyrene.

“This could be a way to improve the health of the worms and to deal with the large amount of food waste in Western countries,” said Rinke.

 

But while breeding more worms for this purpose is possible, he envisages another route: creating recycling plants that mimic what the larvae do, which is to first shred the plastic in their mouths then digest it through bacterial enzymes.

“Ultimately, we want to take the superworms out of the equation,” he said, and he now plans more research aimed at finding the most efficient enzymes, then enhancing them further through enzyme engineering.

The breakdown products from that reaction could then be fed to other microbes to create high-value compounds, such as bioplastics, in what he hopes would become an economically viable “upcycling” approach.

© Agence France-Presse

 

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Science

More than 500 new species, including colorful beetles and a ‘hell heron,’ discovered in 2021

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The researchers were largely restricted from traveling to international field sites or visiting other museum collections due to the pandemic, but they persevered to reveal a wealth of species new to science, both living and extinct. The museum, which holds 80 million specimens in its collections, has a staff of 300 scientists.

The first of the two spinosaurids was named Ceratosuchops inferodios, which means “horned crocodile-faced hell heron.” In life, the dinosaur sported horns and bumps across its brow region. The spinosaurid also likely hunted in a way similar to herons, which can catch prey in the water as well as on land.

The second spinosaurid is Riparovenator milnerae, or “Milner’s riverbank hunter.” Both predators likely reached about 29.5 feet (9 meters) in length and had skulls measuring 3.2 feet (1 meter) long. Spinosaurid fossils have been uncovered around the world, but they may have evolved in Europe before migrating to other areas.

A decades-old fossil from the Isle of Wight, often called the United Kingdom’s dinosaur capital, also led to the discovery of Brighstoneus simmondsi, an iguanodontian with an unusual snout.
Fossils finds elsewhere revealed the earliest ankylosaur from Africa, a Chinese sauropod and the oldest carnivorous dinosaur to be found in the UK.

“It’s been a fantastic year for the description of new dinosaurs, especially from the UK,” said Susannah Maidment, a senior researcher in paleobiology at the Natural History Museum, in a release.

“These specimens are parts of a vast palaeobiological jigsaw puzzle that allows us to understand environments of the past and how they changed over time.”

Other ancient creature discoveries in 2021 included spiders trapped in amber, a plant-eating crocodile relative and a “Jurassic mouse” that once ran between the feet of dinosaurs 166 million years ago in what is now Scotland.

All creatures great and small

Earth is home to a vast array of small shrimplike crustaceans called copepods. They are found across the globe, from mountain lakes to ocean trenches, and scientists discovered 291 new species of copepods in 2021.

While these creatures are tiny, they are a vital source of food for fish and krill and critical to Earth’s carbon cycle and ecology. A collection spanning six decades, created by French marine zoologist Françoise Monniot and her late husband, marine biologist Claude Monniot, provided the basis for the perfect pandemic project.

“Copepods are not only free-living but many are parasites, and they can be found living in virtually every other major animal group,” said Geoff Boxshall, merit researcher in the museum’s department of life sciences, in a statement. “Completing the series of papers became my lockdown project when I was unable to enter the Museum.”

In addition to wasps, moths, crabs and flies, researchers also found 90 new species of beetles, including shiny purple and green ones from India and a large-jawed species from the Philippines.

And scientists finally solved the mystery of a bush cricket from Southeast Asia. They first heard its unusual, beautiful song in 1990, but didn’t connect the two until now.

There are five new species of plants from eastern Africa, called jewelweeds or touch-me-nots. These plants typically have pink or white blossoms, but some have begun to produce red flowers to make themselves more visible to birds.

The scientists also determined 10 new reptiles and amphibians, including a snake called Joseph’s racer. A 185-year-old painting helped researchers describe the species.

Unfortunately, some of the species discovered are also likely extinct, highlighting the importance of recognizing and understanding every creature on our planet.

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