Saturday, November 02, 2024

 

Mathematical model illuminates how environment impacts life choices of salmon


New model highlights how ecological change can affect evolutionary strategies



Tokyo Metropolitan University

Modeling the migratory choices of female masu salmon. 

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Researchers built a mathematical model looking at how the migratory choices of female masu salmon change in different environmental conditions.

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Credit: Jun-nosuke Horita




Tokyo, Japan – Researchers from Tokyo Metropolitan University have created a mathematical model that models how the evolutionary strategies of organisms are affected by the environment. They studied salmonid fishes which choose either to migrate to the sea then return to lay eggs or stay in the river depending on their individual features. Their model correctly predicts how the proportion choosing to migrate changes with environmental conditions, predicting how environmental change can trigger eco-evolutionary responses.

 

Salmonids (or salmon-like) fish are known to face a tough choice early in their lives. They can either stay where they are their entire lives or migrate to the sea where they adapt to seawater. Those that migrate then come back to the river to lay their eggs. This coexistence of steeply diverging strategies by which these fish survive can have a complex impact on how their populations evolve, particularly given their interaction with the environment, and how that might impact the features of individuals and lead to a changing proportion taking up different pathways. While such divergences are not rare in the animal kingdom, the way in which this can impact the evolution of a population is not fully understood.

To get more insight into this problem, a team of scientists led by Jun-nosuke Horita of the Japan Weather Association and Assistant Professor Yuuya Tachiki of Tokyo Metropolitan University have built a mathematical model which incorporates known traits of a particular salmonid, the female masu salmon, and looks at how populations change over time given the availability of alternative tactics. Female masu salmon have three tactics available to them. They can stay in the river where they are born their entire lives (residents), migrate to the sea after a year (early migrants), or move at a later stage of their lives (late migrants). For simplicity, they modeled the salmon to be either resident or early migrants and incorporated known features of salmon demographics such as the number of eggs given per individual, and their survival rate. A key feature was the incorporation of size distributions, since specimens which are smaller at an early stage of their lives are more likely to choose the migratory route.

Using their model, the team were able to show that there was a wide range of parameters over which a stable population was maintained. Importantly, they could identify a set of conditions under which alternative strategies began to kick in. They found that a river environment which was poor for survival coupled with a fertile sea environment led to a greater likelihood of divergent migratory tactics. Importantly, this is exactly what is seen in nature. They were also able to study extreme cases which may be difficult to consider otherwise. For example, when the survival rate of the harsh migration process dips below a certain point, there is a sudden switch which leads to entire populations becoming residents.

The ability to predict how populations choose different migratory strategies is important for understanding eco-evolution, and conversely, how environmental change can impact the survival of organisms. The team hope that their work may be applied to gauge and predict how anthropogenic changes can impact animal populations.

This work was supported by a Grant-in-Aid for JSPS (Japan Society for the Promotion of Science) Research Fellows (19J21686), Grants-in-Aid for Young Scientists (17K1597 and 20K15876), the Fund for the Promotion of Joint International Research (Fostering Joint International Research (B)) (20KK0163), and the JST-MIRAI Program (JPMJMI18G1).

In the photo with two specimens, the upper specimen is female, while the lower specimen is male.

Credit

Jun-nosuke Horita

 

New methods for whale tracking and rendezvous using autonomous robots


Project CETI and Harvard have established a new reinforcement learning framework for rendezvous with whales using autonomous robots, combining sensing from diverse sensor streams



Harvard John A. Paulson School of Engineering and Applied Sciences





Project CETI (Cetacean Translation Initiative) aims to collect millions to billions of high-quality, highly contextualized vocalizations in order to understand how sperm whales communicate. But finding the whales and knowing where they will surface to capture the data is challenging — making it difficult to attach listening devices and collect visual information. 

Today, a Project CETI research team led by Stephanie Gil, Assistant Professor of Computer Science at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), have proposed a new reinforcement learning framework with autonomous drones to find sperm whales and predict where they will surface. 

The research is published in Science Robotics. 

This new study uses various sensing devices, such as Project CETI aerial drones with very high frequency (VHF) signal sensing capability that leverage signal phase along with the drone’s motion to emulate an ‘antenna array in air’ for estimating directionality of received pings from CETI’s on-whale tags. It demonstrates that it’s possible to predict when and where a whale may surface by using these various sensor data as well as predictive models of sperm whales dive behavior. With that information, Project CETI can now design algorithms for the most efficient route for a drone to rendezvous—or encounter—a whale at the surface. This also opens up possible conservation applications to help ships avoid striking whales while at the surface.

Presenting the Autonomous Vehicles for whAle Tracking And Rendezvous by remote Sensing, or AVATARS framework, this study jointly develops two interrelated components of autonomy and sensing: autonomy, which determines the positioning commands of the autonomous robots to maximize visual whale encounters; and sensing, which measures the Angle-of-Arrival (AOA) from whale tags to inform the decision-making process. Measurements from our autonomous drone to surfaced tags, acoustic AOA from existing underwater sensors, and whale motion models from previous biological studies of sperm whales are provided as inputs to the AVATARS autonomous decision-making algorithm, which in turn aims to minimize missed rendezvous opportunities with whales. 

AVATARS is the first co-development of VHF sensing and reinforcement learning decision-making for maximizing rendezvous of robots and whales at sea. A well-known application of time-critical rendezvous is used with rideshare apps, which uses real-time sensing to note the dynamic paths and positions of drivers and potential riders. When a rider requests a ride, it can assign a driver to rendezvous with the rider as efficiently and as timely as possible. Project CETI’s case is similar in that they are real-time tracking the whale, with the goal of coordinating the drone’s rendezvous to meet the whale at the surface. 

This research advances Project CETI's goal of obtaining millions to billions of high-quality, highly contextualized whale vocalizations. The addition of diverse types of data will improve location estimates and routing algorithms—helping Project CETI meet that goal more efficiently.

“I’m excited to contribute to this breakthrough for Project CETI. By leveraging autonomous systems and advanced sensor integration, we’re able to solve key challenges in tracking and studying whales in their natural habitats. This is not only a technological advancement, but also a critical step in helping us understand the complex communications and behaviors of these creatures,” said Gil.

“This research is a major milestone for Project CETI’s mission. We can now significantly enhance our ability to gather high-quality and large-scale dataset on whale vocalizations and the associated behavioral context, putting us one step closer to better listening to and translating what sperm whales are saying,” said David Gruber, Founder and Lead of Project CETI.

“'This research was an amazing opportunity to test our systems and algorithms in a challenging marine environment. This interdisciplinary work, that combines wireless sensing, artificial intelligence and marine biology, is a prime example of how robotics can be part of the solution for further deciphering the social behavior of sperm whales,” said Ninad Jadhav, Harvard University PhD candidate and first author on the paper.

“This project provides an excellent opportunity to test our algorithms in the field, where robotics and artificial intelligence can enrich data collection and expedite research for broader science in language processing and marine biology, ultimately protecting the health and habitat of sperm whales,” said Sushmita Bhattacharya, a postdoctoral researcher in Gil's REACT Lab at SEAS.

 

New findings on animal viruses with potential to infect humans



Study shows how virus family gains entry to mammal cells



Ohio State University





COLUMBUS, Ohio – Scientists investigating animal viruses with potential to infect humans have identified a critical protein that could enable spillover of a family of organisms called arteriviruses.

In a new study, researchers identified a protein in mammals that welcomes arteriviruses into host cells to start an infection. The team also found that an existing monoclonal antibody that binds to this protein protects cells from viral infection.

Arteriviruses circulate broadly in many types of mammals around the world that serve as natural hosts – such as nonhuman primates, pigs and horses – but so far have not been detected in humans.

The researchers’ aim is to better understand mechanisms of arterivirus infection to get a handle on how high the infection risk is for humans and what preparation may be needed should a spillover occur in the future.

“It’s important to consider that since we have no known arteriviruses infecting people that we’re essentially immunologically naïve, so we can’t rely on preexisting immunity to help us,” said co-lead author Cody Warren, assistant professor of veterinary biosciences at The Ohio State University.

Warren co-led the work with Adam Bailey, assistant professor of pathology and laboratory medicine at the University of Wisconsin-Madison. The study was published recently in Nature Communications.

Many natural hosts of arteriviruses have no signs of disease, but the virus that infects swine can cause pneumonia, as well as abortions in pregnant pigs, and other strains can cause hemorrhagic fever or encephalitis when they switch animal hosts.

These viruses also have the unusual ability to maintain long-term infections and become more virulent when they find new hosts – which gives them time to evolve and improve their chances of transmission.

The research team set out to find proteins in mammals that arteriviruses use as receptors to gain entry to host cells and make copies of themselves. Bailey used genome-wide CRISPR-knockout screening technology to identify specific genes that, when disrupted, rendered cells resistant to viral infection. Such genes would then be considered essential to the viral infection process. The unbiased screen identified two genes, FCGRT and B2M, whose protein products come together to form the FcRn receptor (neonatal Fc receptor) that is expressed on the surface of cells.

The FcRn receptor molecule has a specific role in shuttling antibodies across the placenta to a fetus, but is also present in immune cells and cells that line blood vessel walls – both of which are targeted by arteriviruses.

Results from this study demonstrated that FcRn is used for host cell entry by at least five arteriviruses that infect monkeys, pigs and horses, respectively: three diverse strains of simian arteriviruses, porcine reproductive and respiratory syndrome virus 2 (PRRSV-2), and equine arteritis virus (EAV).

Knocking out the major component of the FcRn complex – the FCGRT gene – from host cells blocked viral infection, and pre-treating cells with a monoclonal antibody against FcRn protected against infection.

There was also a genetic twist to this story: Some mammal hosts were less susceptible to arterivirus infection based on differences in their species-specific FcRn’s sequence, meaning that in some cases, this protein will function as a barrier to cross-species infections.

“Chimpanzees and humans have pretty much all the same genes, but the sequence of those genes is slightly different,” Bailey said. “All mammals have the FcRn receptor, but their ability to support infection with a given arterivirus may vary.”

The CRISPR screen also identified a gene encoding another surface protein, CD163, which Warren and colleagues previously found to be a gatekeeper for an arterivirus called simian hemorrhagic fever virus (SHFV) to infect a cell.

A series of experiments in different cell types and using multiple viral strains in the new study showed that CD163 does have a role in infection by most arteriviruses, but it cannot act alone – interaction with FcRn is also key to facilitating arteriviral infection of host cells.

Spelling out these arterivirus infection steps is an important milestone, the researchers said.

“If we’re looking at virus biology, one of the most important things we can understand is entry mechanisms. Because if you can stop the ability of a virus to infect a cell through disrupting that initial virus-receptor contact, now you have a potential therapeutic strategy,” Warren said.

One of those “disruptors” could be blocking the receptor – so showing that an existing monoclonal antibody can stop viral infection in cells is also a plus for scientists examining viruses through a lens of pre-pandemic preparedness.

“If one of these viruses emerged in humans, I believe we’d be in big trouble,” Bailey said. “So that is the motivator for me.”

This work was supported by National Institutes of Health grants, University of Wisconsin-Madison startup funds, the G. Harold and Leila Y. Mathers Foundation, and the Burroughs Wellcome Fund Pathogenesis of Infectious Disease Program.

Co-authors included Teressa Shaw, Kylie Nennig, Xueer Qiu, Devon Klipsic and Igor Slukvin of UW-Madison; Devra Huey, Makky Mousa-Makky, Jared Compaleo, Fei Jiang and Haichang Li of Ohio State; Aadit Shah of Stanford University; Raymond Rowland of the University of Illinois Urbana-Champaign; and Meagan Sullender and Megan Baldridge of Washington University in St. Louis.

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Contacts:

Cody Warren, Warren.802@osu.edu
Adam Bailey, ALBailey@wisc.edu

Written by Emily Caldwell, Caldwell.151@osu.edu

 

 

Salton Sea receding at greater rate according to Loma Linda University study



The resulting dried lakebed is creating more polluted dust from dried agricultural runoff that affects nearby communities




Loma Linda University Adventist Health Sciences Center

Balloon mapping 

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Researchers use balloon mapping to track the Salton Sea shoreline.

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Credit: Loma Linda University




The Salton Sea, California’s largest lake by surface area, is experiencing an increasing rate of shoreline retreat following a policy change that shifted more water from the Colorado River to San Diego, according to a newly published study. The resulting dried lakebed is creating more polluted dust from dried agricultural runoff that affects nearby communities, researchers said.

Researchers forecast that parts of the Salton Sea’s North Shore are expected to retreat 150 meters by 2030 and an additional 172 meters by 2041 given the current rate of retreat.

The average rate of retreat between 2002 and 2017 rose from 12.5 meters a year to nearly 38.5 meters per year after 2018. “[W]ithout mitigation, the expanding exposed playa around the Salton Sea is expected to worsen pollutant exposure in local communities,” the study stated.

The study was conducted as a community science program involving local youth and other residents using balloon mapping to record images of coastline.

“This research was a direct response to a request from the community, which wanted to be involved in impactful research questions to understand shoreline reduction,” said Ryan Sinclair, PhD, MPH, associate professor of environmental microbiology at Loma Linda University School of Public Health and primary investigator of the study. “The community wants to be able to live next to a Salton Sea that they’re proud of.”

Sinclair said balloon mapping can cover a larger area compared to using drones, which need to be recharged.

The study was published recently in Geographries. The study authors included students, LLU faculty, staff from the Alianza Coachella Valley, and a researcher from University of California, Riverside.

Sinclair and community members spent numerous days from 2019 to 2021 creating a series of maps using ballons outfitted with cameras suspended 200 feet above the shore. Researchers compared their findings with satellite images from 2002. They now hope their results can be part of efforts to restore the lake’s capacity.

Aerial map of the Salton Sea shows recession of shoreline

aerial map of Salton Sea shoreline shows recession over time

Credit

Loma Linda University

 

Remote control eddies: Upwelled nutrients boost productivity around Hawaiian Islands



University of Hawaii at Manoa
Simulated phytoplankton bloom 

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Example of a high-chlorophyll event simulated in the model in December 2015.

 

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Credit: Feloy, et al. (2024)




Beyond colorful coral reefs and diverse nearshore ecosystems, Pacific Ocean waters surrounding the Hawaiian Islands have comparatively little marine life and low biological productivity. New research published by University of Hawai‘i (UH) at Mānoa oceanographers showed that eddies on the leeward side of the Hawaiian Islands can supply nutrients, not only locally, but also to the opposite side of the island chain and stimulate blooms of phytoplankton, microscopic plant life that lives in the surface ocean. 

The study, published in JGR Oceans, was selected by the American Geophysical Union’s editorial board as a featured article.

“While these eddies are known to impact biological productivity locally, our study reveals that nutrients upwelled by these eddies can also be transported around the islands, counter to the background flow,” said Kate Feloy, lead author of the study, Uehiro graduate fellow, and doctoral candidate in the Department of Oceanography at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). “These results demonstrate how eddies can have far‐reaching, remote impacts on productivity around the Hawaiian Islands.”

Unreported blooms, a trailhead

Nutrient availability is vital for phytoplankton, which form the base of the marine food chain. With waters around Hawai'i typically very low in nutrients, growth is limited. Feloy and co-authors, Brian Powell and Tobias Friedrich, observed in satellite data previously unreported blooms of phytoplankton off the northern coasts of some Hawaiian Islands. 

The researchers used a computer model of the region to simulate the ocean around the Main Hawaiian Islands and conducted a series of experiments to determine the source of the nutrients driving these anomalous events. Initially, they expected to uncover a mechanism that caused local upwelling, on the north side of the island chain. The model accurately reproduced the bloom events; however, the results indicated that the blooms were driven by nutrients supplied from upwelling eddies around 100 miles away.

“Our study reveals that nutrients from the eddies can be transported in waters below the sunlit layer around the islands where local upwelling can lead to phytoplankton blooms,” said Feloy. “This work identifies a new mechanism that can deliver nutrients around Hawai'i.”

These blooms are significant events for biological productivity in the region—productivity that can be transferred through the food chain, potentially impacting fisheries near Hawai‘i. This same mechanism may also impact productivity around islands in other nutrient-poor regions.


Graphic showing elevation of Hawaiian Islands and bathymetry of surrounding ocean. 

Credit

UH Mānoa, Hawai‘i Mapping Research Group

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Friday, November 01, 2024

 

Identifying the genes that viruses ‘steal’ from ocean microbes


Study suggests viruses reprogram at least 1/3 of metabolic processes



Ohio State University





COLUMBUS, Ohio – The microbes that cycle nutrients in the ocean don’t do the work on their own – the viruses that infect them also influence the process. It’s a vital job for the rest of the planet, enabling oceans to absorb half of the human-generated carbon in the atmosphere and produce half of the oxygen we breathe.

A new study gets scientists closer to more fully understanding where viruses fit into the global ocean picture of cycling nutrients such as nitrogen, phosphorous and, of particular interest, carbon. The research broadly expands on a 20-year-old finding that genes can be exchanged between viruses and the photosynthetic cells they infect and consolidates data resulting from more than 100 papers on viruses and metabolism that followed.

The research team, led by The Ohio State University, reports in the journal Microbiome on its creation of a catalog of genes that viruses “stole” from the marine microbes they infected across all of the world’s oceans. Scientists identified and organized almost 23,000 genes known as auxiliary metabolic genes (AMGs), including over 7,000 never previously documented. The analysis suggests that about 1 in 5 ocean virus populations carries at least one AMG.

Adding even more context to the viruses’ role, the researchers mapped 340 metabolic pathways attributed to microbes in the oceans – changes to the nutrient balance resulting from organisms consuming and generating molecules based on their survival needs. Of those, the scientists found that viral AMGs mapped to 128 pathways – meaning viruses affected over 37% of those processes.

“We still don’t know the extent of viruses’ impact. But now that we know the pathways that viruses target via AMGs, we could use metabolic modeling approaches to quantitatively estimate the viral impact on the host communities and ocean functioning,” said first study author Funing Tian, who completed the work as a PhD student in microbiology at Ohio State.

“Future modeling work could involve increasing or decreasing metabolic fluxes occurring through these pathways and seeing how the impact of viruses would change.”

Tian and her co-lead author, former Ohio State microbiology postdoctoral scholar James Wainaina, focused on DNA viruses that infect prokaryotes: bacteria and other single-celled organisms floating throughout the world’s oceans.

Wainaina and Tian were members of the lab led by the study’s senior author, Matthew Sullivan, professor of microbiology and founding director of the Center of Microbiome Science at Ohio State.

Sullivan was the virus coordinator for the Tara Oceans Consortium, a three-year global study of the impact of climate change on the world’s oceans. As part of that international collaboration, he has led previous work to catalog close to 200,000 DNA and 5,500 RNA virus species in the oceans, and to ascertain viruses’ potential to mitigate climate change.

Tian and Wainaina analyzed 7.6 terabytes of Tara Oceans metagenomic sequence data for this study, increasing the known ocean DNA virus populations to 579,904. From these populations, the team took many computational steps to identify the auxiliary metabolic genes located in virus genomes.

They conservatively identified a total of 86,913 AMGs that grouped into 22,779 sequence-based gene clusters. Of those, 7,248 were identified for the first time. Viruses lift these genes from the microbial cells they infect and incorporate the genes into their own genome – giving them the power to reprogram a host cell’s function in a way that ensures viral survival.

“The challenge with auxiliary metabolic genes is that people know they’re there, but the gene is similar to the cellular copy – that makes it important to differentiate between the viral copy and the microbial copy,” Wainaina said.

“To minimize false positives, we undertook curation steps to make sure we focused only on AMGs that were on viral genome segments,” Tian said.

They then further analyzed the genomic data to determine metabolic pathways – each one a series of related actions that alter a cell’s function – that could be traced to specific microbial species, revealing 340 such pathways. With their new catalog of “stolen” genes, the researchers found that 128 of these pathways were targeted by viral AMGs.

“That’s our big finding,” Tian said. “Before this paper, it was unknown how many metabolic pathways were encoded in microbes throughout the global oceans, and even less understood among those how many were targeted by viruses via AMGs.”

Added Wainaina, “It’s not only about the number, but also which specific pathways viruses are involved in – that informs the biogeochemical cycles viruses are reprogramming and manipulating in the ocean.”

The AMG catalog and metabolic pathway mapping provide a foundation for microbiome engineering experimentation and modeling that will help researchers make more accurate predictions about viruses’ roles in ocean biogeochemical processes, Sullivan said.

“Most current models don’t include viruses at all, and only some include microbes,” he said. “It’s exciting that we’ve generated these data that are critical for bringing viruses and their impacts into new predictive models.”

This work was supported by the National Science Foundation, the Gordon and Betty Moore Foundation, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the G. Unger Vetlese and Ambrose Monell Foundations, and the Ohio Supercomputer Center.

Tian is now a bioinformatician at the University of Chicago, and Wainaina is an assistant scientist in the Biology Department at Woods Hole Oceanographic Institution. Additional co-authors include Cristina Howard-Varona, Guillermo Domínguez-Huerta, Benjamin Bolduc, Garrett Smith, Marissa Gittrich, Olivier Zablocki and Dylan Cronin of Ohio State; Maria Consuelo Gazitúa of Viromica Consulting; Damien Eveillard of Nantes Université; and Steven Hallam of the University of British Columbia.

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Contacts:

Funing Tian, funing.tian@bsd.uchicago.edu
James Wainaina, james.wainaina@whoi.edu
Matthew Sullivan, Sullivan.948@osu.edu

Written by Emily Caldwell, Caldwell.151@osu.edu