Haetera species of clearwing butterfly. Credit: Aaron Pomerantz

A team led by Marine Biological Laboratory (MBL) scientists studied the development of one such species, the glasswing butterfly, Greta oto, to see through the secrets of this natural stealth technology. Their work was published in the Journal of Experimental Biology.

Although transparent structures in animals are well established, they appear far more often in aquatic organisms. "It's an interesting biological question because there just aren't that many transparent organisms on land," notes lead author Aaron Pomerantz, a PhD candidate in Integrative Biology at the University of California, Berkeley. "So we asked the question, what is the actual developmental basis of how they create their transparent wings?"

Butterfly wings are known for their colorful patterns, created by tiny, overlapping, chitinous scales that reflect or absorb various wavelengths of light to produce colors. Pomerantz says that although scale coloration has been intensively studied, investigating the developmental origins of transparency in land-based butterflies hadn't been done before. "Transparency is sort of the opposite of color," he says.

Pomerantz and his co-authors, including his PhD advisor and MBL Director Nipam Patel, were inspired by the work of students in MBL's Embryology course, in which Patel teaches. "I decided to bring some of the transparent butterfly and moth species I had in my collection, which I never really looked at in detail, to the course and present it as a challenge for the students to look at how these wings were transparent,” Patel says. “A group of students took that on by imaging the wings with various microscopes. And they realized that pretty much any way you could think to make the wing transparent, some butterfly or moth had figured out how to do it. That's what got us looking in more detail at the development of transparency."

Building on that work, the researchers used confocal and scanning electron microscopy to construct a developmental time scale of how transparency emerges in Greta oto, from the pupal stage to adulthood. They found that the glasswing butterfly's wings develop differently than opaque species, with a lower density of precursor scale cells in the areas that will later develop as transparent. At a very early stage, scale growth and morphologies differed, with thin, bristle-like scales developing in transparent regions and flat, round scale morphologies within opaque regions.

The glasswing butterfly (Greta oto), full body. Credit: Aaron Pomerantz

An array of Cithaerias and Haeterini clearwing species. Credit: Nipam Patel

"What Greta oto does is to make fewer scales and to make them in these very different, bristle-like shapes," Patel explains. "But getting the scales out of the way is only part of the problem of creating transparency. Aaron also made a series of observations about nanostructures on the wing that prevent glare in bright sunlight.

When light hits these little arrays of nanostructures, it doesn't reflect off -- it goes straight through. So that gives much better transparency,” he says.

“As humans, we think we're so brilliant because we figured out how to put anti-glare coating on glass, but butterflies basically figured that out tens of millions of years ago,” Patel says.
 

Clearwing butterflies filmed in Peru and Ecuador. Credit: Aaron Pomerantz

 
Unusual wing scales and nanostructures are only part of the story. A second layer of waxy hydrocarbon nanopillars lies atop the wing surface, providing further anti-reflective properties. The researchers examined the reflectivity of the wings before and after removing the waxy layer with hexane.

"We measured the amount of light that reflected off the wing," says Pomerantz. "Those experiments demonstrated that that upper layer was very important for helping to reduce that glare." Biochemical analysis showed that the waxy layer is mostly composed of long chain n-alkanes, similar to those found in other insect species. "They're primarily thought of as something that helps prevent an insect from drying out or desiccating. But in this case, it seems like they're used for these anti-glare properties as well."

Glasswing butterfly (Greta oto) on notes. Credit: Aaron Pomerantz

Greta oto chrysalis. Credit: Aaron Pomerantz

 

Future research directions may include delving more deeply into the how these transparent structures evolved. Pomerantz points out that "if we can learn more about how nature creates new types of nanostructures, that can be very informative for human applications." The work is making the secrets of natural transparency considerably less opaque.

By Mark Wolverton

Homepage photo: A glasswing butterfly feeding at flowers in Costa Rica. The remarkable transparency of these butterflies allows them to be “invisible”, and the antiglare coating of their wings helps to prevent them from being given away by any glare of sunlight off their wings. Credit: Nipam Patel

Citation: Aaron F. Pomerantz, Radwanul H. Siddique, Elizabeth I. Cash, Yuriko Kishi, Charline Pinna, Kasia Hammar, Doris Gomez, Marianne Elias and Nipam H. Patel (2021) Developmental, cellular and biochemical basis of transparency in clearwing butterflies. J. Exp. Biol., DOI: 10.1242/jeb.237917

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The Marine Biological Laboratory (MBL) is dedicated to scientific discovery – exploring fundamental biology, understanding marine biodiversity and the environment, and informing the human condition through research and education. Founded in Woods Hole, Massachusetts in 1888, the MBL is a private, nonprofit institution and an affiliate of the University of Chicago.

Redirects to https://www.mbl.edu/legacy-of-leadership/.

Contact: Diana Kenney, dkenney@mbl.edu; 508-289-7139

Semester in Environmental Science (SES) Student Claire McGuire prepares to take a sediment core sample in Waquoit Bay, Mass.

WOODS HOLE, Mass. -- Plastics are everywhere. From cell phones to pens and cars to medical devices, the modern world is full of plastic— and plastic waste. New research from scientists at the Marine Biological Laboratory (MBL) Ecosystems Center found that some of that plastic waste has been accumulating in salt marshes for decades. The study was published in Environmental Advances.

Salt marshes are the link between the land and open ocean ecosystems, and — in a way —between urban environments and the wild ocean. Microplastics (plastic particles smaller than 5 millimeters) tend to float on the water surface, but salt marshes fill and empty with the tides, so particles that would normally float get trapped within branches and roots and settle into the marsh soil.

Sediments accumulate in the salt marsh layer after layer, like tree rings, keeping an historical record of sedimentation within the ecosystem. “By accumulating sediments, they are keeping a record in time,” says Javier Lloret, MBL research scientist and co-first author on the paper.

Globally, scientists estimate that about 8 million tons of plastic enter the ocean each year. But until now, there’s been no estimation of the amount of that plastic that gets trapped in salt marsh ecosystems.

By taking core samples of the marsh sediment at six different estuaries in the Waquoit Bay system on Cape Cod, as well as New Bedford, Mass., harbor, the researchers were able to trace the abundance of microplastics dating back decades in areas with very contrasted degrees of land use.

“As you go into the past, the amount of microplastics you find decreases clearly,” says Lloret. “The amount of microplastics you find in sediments is related to the population numbers… but also the amount of plastic that people use.”

A sediment core sample from New Bedford Harbor, Mass. with microplastic debris (blue flecks) clearly visible. Credit: Miriam Ritchie

“Waquoit Bay is the perfect salt marsh system to study plastic pollution because we can contrast one area that is almost pristine… with another area that is highly impacted by human activity,” says Rut Pedrosa-Pàmies, also an MBL research scientist and co-first author on the paper. “We found a broad range of plastic pollution.”

The researchers focused on two types of microplastic pollution: fragments (from the breakdown of larger plastic pieces) and fibers (thread-like plastics which tend to shed from clothing and fishing gear). They found that fragment pollution increased both through time and with urbanization. The more populated the area surrounding the collection site, the more plastic fragments the researchers observed.

One surprise in the data was that microplastic concentration in the sediments wasn’t linear as urbanization grew. Up to 50% development, the concentration of microplastic fragments was relatively unchanged, but once the land was occupied at 50%, the number of microplastics grew exponentially.

Microplastics collected from a sediment core sample in the Childs River area in Waquoit Bay, Mass. under 0.38 x magnification. Credit: Miriam Ritchi, SES student.

"Just a few people in the surrounding area is not going to change much, but when urban uses occupy more than 50% of the land, the number of microplastics goes crazy," says Lloret.

The microplastic fibers didn’t have the same relationship with urbanization. "Even in the more pristine areas that don’t have urbanization, we find fiber plastic pollution" says Pedrosa-Pàmies.

Students from the MBL SES course work together to extract a core sediment sample from the marsh.

The researchers believe the fragments have a local origin (people using and disposing of plastics where they live) whereas fibers can be transported long distances by air or by water from large-scale urban areas.

"When we started, we didn’t know if microplastics were an issue here on Cape Cod, or not. No one had analyzed the marsh sediments on Cape Cod for microplastics before," says Lloret.

Now that the scientists have shown there is microplastic pollution in New England salt marshes, the next step is to gain further insight. How are those particles arriving in the ecosystem? What are the sources? How are they impacting the ecosystem and the food web of the organisms that live there?

"There are still a lot of unanswered questions," says Pedrosa-Pàmies. "This is the first step for management, too.'

This work stemmed from a 2018 student research project in MBL’s Semester in Environmental Science (SES) program. Students from other MBL programs also participated in ongoing sample collection analysis, including SES, the National Science Foundation-sponsored Research Experiences for Undergraduates, and the Jeff Metcalf Summer Internship Program from the University of Chicago.

Citation:

Lloret, J.*, Pedrosa-Pamies, R.*, Vandal, N., Rorty, R., Ritchie, M., McGuire, C., Chenoweth, K., & Valiela, I. (2021). Salt marsh sediments act as sinks for microplastics and reveal effects of current and historical land use changes. Environmental Advances, 4, 100060. DOI: 10.1016/j.envadv.2021.100060 (* These authors share first authorship)

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The Marine Biological Laboratory (MBL) is dedicated to scientific discovery – exploring fundamental biology, understanding biodiversity and the environment, and informing the human condition through research and education. Founded in Woods Hole, Massachusetts in 1888, the MBL is a private, nonprofit institution and an affiliate of the University of Chicago.

Contact: dkenney@mbl.edu; 508-289-7139

A diver measuring the size of a newly outplanted bunch of Eucheumatopis isiformis, a red seaweed native to the Caribbean. The research team will monitor the algae throughout its cultivation to determine which environmental conditions and farm operations lead to optimal algal growth and composition. Credit: Loretta Roberson

WOODS HOLE, Mass. and La Parguera, P.R. – A team of researchers led by Loretta Roberson, associate scientist at the Marine Biological Laboratory, Woods Hole, has installed the first seaweed farm in Puerto Rico and U.S. tropical waters.

The research array furthers the design and development of a system for offshore cultivation of tropical seaweeds to support large-scale production of biomass for biofuels and other valuable bioproducts.

“Puerto Rico has stable warm temperatures and ample sunlight year-round, as well as a wide range of exposure to prevailing winds and waves. These conditions make its southern coastline an ideal test bed for exploring how environmental conditions influence the biological, physiological, and chemical properties of cultivated macroalgae, as well as the impact of seaweed farms on the surrounding environment,” says Roberson, the lead principal investigator on this research effort. Additional farms are being tested in Florida and Belize to assess scalability.

As the site is the first of its kind in the region, authorizations were required from numerous agencies including the U.S. Army Corps of Engineers, the U.S. Coast Guard, and the Puerto Rico Department of Natural and Environmental Resources.

“Facilitating research of this nature will be key for the development of sustainable aquaculture in this area,” says Roberson. “We have tested similar farm designs in New England and Alaska, but this will be the first test of the array in warm tropical waters where we expect higher fouling rates from other marine organisms, UV damage, and threats from hurricanes.” Unlike kelp cultivation, which is usually seasonal, tropical seaweed farming can support year-round harvesting.

The research team includes experts in ocean farm systems design, modeling of nutrient dynamics in ocean systems, environmental impact assessment and stakeholder engagement, and economic analysis.

The team members are affiliated with an additional 16 organizations: Caribbean Coastal Ocean Observing System, University of Puerto Rico Mayaguez, University of Puerto Rico Rio Piedras, Woods Hole Oceanographic Institution, C.A. Goudey & Associates, Tend Ocean, University of Connecticut Stamford, Cascadia Research Collective, Center for Research and Advanced Studies of the National Polytechnic Institute Merida, Makai Ocean Engineering, Pacific Northwest National Laboratory, Rutgers, The Nature Conservancy, Two Docks Shellfish LLC, University of California Irvine, and University of California Santa Barbara.

David Bailey (Woods Hole Oceanographic Institution) and Loretta Roberson (MBL) preparing to dive on the seaweed farm site off Puerto Rico. Divers will conduct frequent ecological monitoring and routine gear assessments throughout the course of the project. Credit: Domenic Manganelli

The researchers are currently targeting commercially valuable red algal eucheumatoid species, which are primarily cultivated in East Africa and Asia. To date, eucheumatoids have been difficult to propagate in a cost-effective manner and production has been limited to easily accessible areas near shore. In addition to developing the best methods for cultivating these species in offshore environments, the project team seeks to further quantify the ecosystem services associated with the farming activities. These likely include habitat provision for a variety of marine species and the improvement of water quality through removal of excess nutrient and buffering of pH.

Cliff Goudey and Domenic Manganelli of C.A. Goudey & Associates/Tend Ocean, transporting the anchors, line, and buoys used for the seaweed farm off Puerto Rico. Credit: Loretta Roberson

MBL received funding for this research from the U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) competitive Macroalgae Research Inspiring Novel Energy Resources (MARINER) program. The MARINER program seeks to develop the tools to enable the United States to become a leading producer of macroalgae, helping to improve U.S. energy security and economic competitiveness.

For additional information about MBL and this project, please visit: mbl.edu/tropical-seaweed/.

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The Marine Biological Laboratory (MBL) is dedicated to scientific discovery – exploring fundamental biology, understanding biodiversity and the environment, and informing the human condition through research and education. Founded in Woods Hole, Massachusetts in 1888, the MBL is a private, nonprofit institution and an affiliate of the University of Chicago.

The MBL’s Rowe Laboratory, where many of the Whitman Center labs are located. Credit: Tom Kleindinst

Due to COVID-19-related restrictions, nearly all of the 2020 Whitman Fellows and Early Career Investigators deferred until this year.

“After last year’s restrictions, we are thrilled welcome this year’s Whitman Fellows,” says David Mark Welch, MBL Director of Research. “The magic of the MBL is its power to bring people together and offer scientists the space, time, and inspiration to pursue their research.”

In a typical year, nearly 300 principal investigators, staff, and research associates from institutions worldwide convene in the Whitman Center, which offers them an unparalleled environment for collaboration. The MBL provides access to a diversity of marine and other organisms for research, state-of-the-art instrumentation, innovative imaging technologies and research, genome sequencing, and modern laboratory facilities.

Due to ongoing social distancing guidelines, the MBL is hosting about two-thirds of the typical number of Whitman investigators this summer.

The Whitman Center scientists interact extensively with the dynamic and creative research environment at MBL, which encompasses its resident scientists and international faculty, students and lecturers who participate in MBL’s Advanced Research Training Courses.

Using a wide range of experimental research organisms, from sea anemones to sea robins and many organisms in between, this year’s Whitman Fellows are pursuing a variety of fundamental research questions related to cell biology and imaging, neuroscience, modeling, regeneration and development, evolution, genomics, marine biology and diversity, microbiomes, and more.

Several of the 2021 fellows are coming to the MBL for the first time to launch new projects and others will continue research established in the Whitman Center in prior years.

The acorn worm (Saccoglossus kowalevskii) is being used as a research organism by one of this year's Whitman Fellows. Credit: Tom Kleindinst

The 2021 Whitman Fellows and their proposed research projects are:

Karen Crawford, St. Mary’s College of Maryland
Beyond proof of concept: using CRISPR-Cas9 genome editing in Doryteuthis pealeii to ask important fundamental biological questions

André Fenton, New York University
Integrating across levels of biology to learn how memory is sustained

Suresh Jesuthasan, Nanyang Technological University
An investigation of the amphibian Leydig cell: from mucosal immunology to conservation biology

Veronica Martinez-Acosta, University of the Incarnate Word
Photoreception in Lumbriculus variegatus, an aquatic annelid

Gerardo Andres Morfini, University of Illinois at Chicago
Axon-specific effects of neuropathogenic proteins on kinase-based signaling and organelle motility

Anthony Moss, Auburn University
Establishing a standardized, reproducible system for the study of geotaxis and mood in ctenophores

Ed Munro, University of Chicago
Dynamics of gastrulation and neurulation in ascidian
Cortical septin dynamics during polarization in early C. elegans embryos
NIKON FELLOW

Indu Sharma, Hampton University
Bacterial cell shape and size as predation avoidance strategy in marine environment
E.E. JUST FELLOW

Ava Udvadia, University of Wisconsin – Milwaukee
Elucidating evolutionarily conserved mechanisms regulating successful optic nerve regeneration in vertebrate species

Gert Jan Veenstra, Radboud University
Evolution and development of cardiac cell types

Trevor Wardill, University of Minnesota – Twin Cities
Encoding 3D space in the cephalopod brain

Fiona Watson, Washington and Lee University
Optic nerve regeneration

Elizabeth Willbanks, University of California – Santa Barbara
Biogeography of rapid evolution in bacterial symbiosis: the pink berries revisited

Ricardo Zayas, San Diego State University
Functional analysis of the transcription factor COE in the regeneration of the nervous system of the sea anemone Nematostella vectensis
 
 
The 2021 Whitman Early Career Investigators are:

Vincent Boudreau, University of California – Berkeley
Stentor pyriformis: a novel cell biological model for uncovering evolutionary mechanics of photosynthetic activity regulation

Amy Herbert, Stanford University
Sea robins as a model for evolutionary trait gain in vertebrates

Dragomir Milovaniovic, German Center for Neurogenerative Diseases (DZNE)
Molecular detriments of synaptic vesicle clustering in the nerve terminals

Tetsuto Miyashita, Canadian Museum of Nature
Functions of the “isthmic organizer” and the head-trunk differentiation of the nervous system in a non-chordate deuterostome (hemichordate) Saccoglossus kowalevskii

Christina Zakas, North Carolina State University
Finding the genetic basis of developmental evolution