Friday, February 21, 2025

Hawaiian parasitic flies develop better hearing to locate host crickets

St. Olaf College

image:
A Pacific field cricket and Hawaiian parasitic fly next to each other.
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Credit: Photo courtesy of the University of Denver and St. Olaf College

Research from St. Olaf College and the University of Denver, published in Current Biology, found that a parasitic fly in Hawaii has evolved to eavesdrop on the mating calls of Pacific field crickets. The flies were likely introduced to the Islands by Polynesian settlers and European cargo ships.

The research found that in Hawaii, the acoustic parasitoid fly has quickly evolved more sensitive hearing across a range of sound frequencies that are prominent in recently evolved and rapidly changing cricket calling songs. This adaptation improves the flies’ ability to locate hosts for their larvae, increasing their chances of survival.

“It's important to understand how the sensory systems of eavesdroppers evolve because it reveals the fascinating ways animals adapt to survive and thrive,” said co-corresponding and co-senior author Norman Lee, an associate professor of biology at St. Olaf and the director of the Neuroscience Program. “Eavesdroppers, like flies that listen in on cricket songs, show how some species develop incredible abilities to detect sounds or signals that aren't meant for them.”

In previous studies, co-corresponding and co-senior author Robin Tinghitella, an associate professor of biology at the University of Denver, found that some male Pacific field crickets were evolving new songs through wing mutations, so as not to become prey to carrying the larvae of female Ormia ochracea, the parasitic flies. In turn, the parasitic flies have improved in their ability to find the location of male crickets for the larvae to incubate and develop in –– leading to the decline of crickets that do not have novel songs.

“This now appears to be a classic example of adaptation and counteradaptation, back and forth, between the crickets and flies,” Tinghitella said. “Will the crickets evolve new songs, yet again, to evade the parasitic flies? Will the flies develop new ways of finding hosts? We can’t wait to see what will happen next.”

Building off of previous academic work, the team collected Ormia ochracea flies from Hawaii and Florida as a comparison population. The research team ran two experiment types, behavioral and neural, that focused on measuring the female parasitic flies’ response to cricket song types (such as purring, rattling, and typical). They found that Hawaiian flies had developed a more sensitive auditory system, allowing them to better locate these novel songs. In the field, they found that while the parasitic flies in Hawaii preferred the louder typical cricket songs, they were still able to detect the less intense purring and rattling songs.

“This research also helps us understand broader questions, like how animals navigate their environments, find food, or avoid predators,” Lee said. “Plus, the unique strategies these eavesdroppers use can inspire innovations in technology. In essence, it’s about uncovering the hidden ways nature works and using that knowledge to benefit science and society.”

The research team recommends future studies to compare the neural threshold of the Hawaiian fly and cricket populations. Further research will help to better understand if female crickets’ auditory systems have evolved to better detect new songs by the males.

This research was funded by the National Science Foundation, from their Division of Integrative Organismal Systems and Division of Environmental Biology; an NSF Graduate Research Fellowship; and the Collaborative Undergraduate Research and Inquiry (CURI) program at St. Olaf. The research team was composed of faculty and graduate students from St. Olaf and the University of Denver.

Through CURI, this work received undergraduate research support from Mikayla Carlson ’23 and Mackenzie Farrell ’23 in the summer of 2022 and Quang Vu ’25 in the summer of 2023. “Engaging in cutting-edge, hands-on research allows St. Olaf undergraduates to apply their coursework, develop transferable technical skills, and experience how science is truly done while contributing to meaningful discoveries,” Lee said.

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Previous studies from the research team include:

Journal

Current Biology

DOI

10.1016/j.cub.2025.01.019

Method of Research

Observational study

Subject of Research

Animals

Article Title

Neural and behavioral evolution in an eavesdropper with a rapidly evolving host

Article Publication Date

20-Feb-2025

The rising tide of sand mining: a growing threat to marine life

Michigan State University

image:
Sand Mining Barge on Kuala Langat River, Selangor, Malaysia
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Credit: Khairil Yusof, Creative Commons

In the delicate balancing act between human development and protecting the fragile natural world, sand is weighing down the scales on the human side.

A group of international scientists in this week’s journal One Earth are calling for balancing those scales to better identify the significant damage sand extraction across the world heaps upon marine biodiversity. The first step: acknowledging sand and gravel (discussed as sand in this publication) – the world’s most extracted solid materials by mass – are a threat hiding in plain sight.

“Sand is a critical resource that shapes the built and natural worlds,” said senior author Jianguo “Jack” Liu, Michigan State University Rachel Carson Chair in Sustainability. “Extracting sand is a complex global challenge. Systems approaches such as the metacoupling framework are essential to untangle the complexity. They can help reveal the hidden cascading impacts not only on the sand extraction sites but also other places such as sand transport routes and sites using sand for construction.”

Sand is the literal foundation of human development across the globe, a key ingredient of concrete, asphalt, glass, and electronics. It is relatively cheap and easily extracted.

Unlike critical minerals or deep-sea mining — both of which have attracted significant scrutiny—sand extraction in marine environments remains largely overlooked, despite sand and sediment dredging being the second most widespread human activity in coastal areas after fishing, and its supply is often taken for granted.

Sand mining across the world is being linked to coastal erosion, habitat destruction, the spread of invasive species and impacts on fisheries. Extracting sand can harm marine life by clouding water and riling sediment that can smother seagrasses and coral. Disrupting spans of ocean sand can fragment habitat, change the patterns of waves and other issues that can throw marine life into disarray.

“This resource is often seen as an inert, abundant material, but in reality, it is an essential resource that shapes coastal and marine ecosystems, protects shorelines, and sustains ecosystems and livelihoods,” said lead author Aurora Torres, a researcher at Spain’s University of Alicante. “Since sand extraction is closely linked to coastal erosion, climate adaptation, and biodiversity loss, integrating it into broader environmental policies—such as marine protected areas, blue carbon strategies, climate resilience plans, and strategic natural resource management—is crucial to ensuring it is not treated as an isolated issue.”

Torres and Liu first brought the issues of sand to light in 2017 in the Science paper A looming tragedy of the sand commons. In the One Earth commentary, the two, former and current members of MSU’s Center for Systems Integration and Sustainability, call for sand to be elevated to the attention levels of fishing, aquaculture and tourism in the scale of global attention and action.

“Ultimately, the key to action is making sand extraction visible—through stronger data, improved governance, and direct links to pressing environmental and economic concerns. The more evident and tangible its impacts become, the harder it will be to ignore the need for responsible management,” Torres said, adding sand extraction near fragile populated coastlines can spur action as climate change exacerbates threats to human life.

“Reducing Sand Mining’s Growing Toll on Marine Biodiversity” is also written by Jean-Baptiste

Study highlights successes of Virginia’s oyster restoration efforts

Virginia Institute of Marine Science

Oyster Shells — image:
Spreading oyster shells on top of existing reefs provides new habitat on which juvenile oysters attach and helps maintain the reef’s structure after commercial harvests. Photo by Alexandria Marquardt.
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Credit: Alexandria Marquardt

Virginia has made significant investments in the restoration of oyster reefs in the Chesapeake Bay, and now a study led by William & Mary’s Batten School & VIMS suggests those management practices are literally paying off in the Rappahannock River. The study, recently published in the Journal of Environmental Management, was led by Batten School of Coastal & Marine Sciences Ph.D. student Alexandria Marquardt, who presented the results to the Virginia Marine Resources Commission’s (VMRC) Shellfish Management Advisory Committee on February 19.

In addition to supporting local economies, oysters filter the surrounding water removing algae and excess nutrients while clumping together to form large reefs that serve as habitat for many fish and marine animals. Though once abundant, oyster populations in the Chesapeake Bay collapsed in the mid-1980s due to a combination of overfishing and disease. While Virginia Institute of Marine Science has endeavored to increase wild oysters’ resistance to virulent pathogens, the VMRC regulates the fishery in Virginia and oversees efforts to restore oyster reefs.

“Oyster restoration typically focuses on shell replenishment, in which oyster shells are spread over existing reefs on which juvenile oysters attach and grow. This was an exciting project, because it was the first to evaluate the benefits of replenishment activities both biologically and for the fishery,” said Marquardt, who collaborated on the study with faculty and scientists at the Batten School & VIMS and the VMRC. “Oyster reefs located in public fishing grounds are largely not studied, but we saw significant benefits from even modest replenishment. When combined with rotational harvests, the underlying reef structure was maintained and commercial harvests increased.”

The study showed that the density of juvenile oysters known as spat increased immediately following shell replenishment while the density of market-sized oysters peaked three years after, reinforcing the VMRC’s current 3-year rotational harvest protocol. Spat density, though highly variable, was highest in years coinciding with higher brown shell volumes, a measurement of reef health that refers to the amount of oysters and shell above the bottom sediment layer. Marine protected areas were shown to have higher market oyster densities and offer protection from commercial fishing for larger oysters, which may provide a valuable spawning function for the fishery.

VMRC began their shell replenishment program in 2000 and implemented rotational harvests in 2007. These practices have resulted in steady increases in brown shell volume throughout the Rappahannock River and increased the likelihood of watermen meeting daily harvest limits. Overall, the study showed that oyster harvests steadily increased with the improvement of the oyster reefs, with market oyster densities increasing substantially since 2018.

Since the 2007-2008 harvest season, more than 500,000 bushels of oysters valued at more than $24 million were harvested from the Rappahannock River. The VMRC has invested more than $14 million toward replenishment in the river since 2000.

“It’s rewarding to see that science-based management of this fishery is providing benefits for both the environment and local economies,” said Marquardt. “I’m thankful for the opportunity to work with the VMRC and contribute to a sustainable oyster industry in Virginia.”

View a summary of the study.

The results of the study showed that oyster management practices in the Rappahannock River provide significant biological and commercial benefits.

Credit

Alexandria Marquardt