If you've ever tried to eat a roasted marshmallow dropped in the sand, you probably said “Yecch!” and threw it away. 

Now UC Davis researchers have found that some plants excrete a stickylike glue to entrap sand so predators won't eat them.

Graduate student Eric LoPresti and his major professor, ecologist Rick Karban, professor in the UC Davis Department of Entomology and Nematology, found that two plants, sand verbena Abronia latifolia and the honeyscented pincushion plant Navarretia mellita appear to deliberately make themselves unappealing with a coat of “sand armor.”

Sand entrapment on plant surfaces is called psammophory or sand armor, they said in newly published research in the journal Ecology.

Thus, herbivores like rabbits and bison, avoid eating them. “Sand and soil are nonnutritive and difficult for herbivores to process, as well as visually identical to the background,” they wrote in their abstract.

They describe it as a “phylogenetically and geographically widespread trait.” Globally, more than 200 species of plants excrete a substance cover themselves in sand, something that scientists don't fully understand. Some think it's a means to trap water and protect from the elements.

LoPresti and Karban set out to investigate whether the sand-coating serves as a camouflage or a shield from predators or both.

“We experimentally investigated whether this sand coating physically protected the plant from herbivores or increased crypsis (or the ability of an animal to avoid observation or detection),” they said. “We tested the former hypothesis by removing entrapped sand from stems, petioles, and leaves of the sand verbena Abronia latifolia and by supplementing natural sand levels in the honeyscented pincushion plant Navarretia mellita. Consistent with a physical defensive function, leaves with sand present or supplemented suffered less chewing herbivory than those with sand removed or left as is.”

They tested the “possible crypsis effect” by coating some sand verbena stems with green sand, matching the stem color, as well as others with brown sand to match the background color. “Both suffered less chewing herbivory than controls with no sand and herbivory did not significantly differ between the colors, suggesting crypsis was not the driving resistance mechanism.”

Since their paper's online publication, the work has been featured in Newsweek, Discover and on CBC Radio.

Links:

• Ecology journal paper
• Newsweek
• Discover
• CBC Radio (Canada)
  
  

Doctoral candidate Roberta Tognon, who studied with integrated pest management specialist Frank Zalom, distinguished professor of entomology, UC Davis Department of Entomology and Nematology, will present a research paper from the Zalom lab at the Brazilian Entomological Society meeting March 16. 

Tognon's presentation is on “Learning and Memory of Telemonus podisi Ashmead (Hymenoptera: Platygastridae) to Chemical Compounds from Halyomorpha halys Stal (Hemiptera: Pentatomidae) eggs. She studies with major professor Josue Sant'Ana of the Universidade Federal do Rio Grande do Sul.

Both of the professors are attending the meeting.

Chemical ecologist Jeff Aldrich, an adjunct faculty member of the UC Davis Department of Entomology and Nematology (now retired from the USDA's Agricultural Research Service lab at Beltsville, MD.), is also a co-author on her paper.

Zalom traveled to Brazil to attend the Zika summit, which just ended. He was on stage at the Brazilian Entomological Society opening session to present a major award, as he did two years ago. Zalom is a past president of the 7000-member Entomological Society of America (ESA).  

Canada's CDC covered the Zika summit and issued this report, headlined "Entomologists Bather in Brazil to Stop Zika Mosquito."  Grayson Brown of the University of Kentucky, also an ESA past president and an organizer of the event, is quoted in the news story.

DAVIS--Noted medical entomologist Matthew Thomas of Pennsylvania State University will speak on “Ecology and Control of Pests and Diseases: from Biblical Plagues to the Most Dangerous Animal on the Planet” at a free public lecture on Thursday morning, April 7 in the Walter A. Buehler Alumni and Visitor Center, UC Davis.

The lecture, to take place at 10:45 a.m. in the Alpha Gamma Rho (AGR) Hall, is sponsored by the College of Agricultural and Environmental Sciences and the Storer Life Sciences Endowment of UC Davis.

At Penn State, Thomas serves as the Huck Scholar in Ecological Entomology and directs the Ecology Institute, in addition to his duties as a professor of entomology in the Department of Entomology and Centre for Infectious Disease Dynamics.

He will be introduced by Professor Shirley Luckhart of the UC Davis Department of Medical Microbiology and Immunology, coordinator of the event.

Thomas researches many aspects of the ecology and evolution of insect pests and diseases in his drive to understand the consequences of global change and to improve the effectiveness and sustainability of pest and disease management. His work involves predicting and understanding the impact of invasive species, and researching biodiversity and ecosystem health, plus many aspects of biological control.

Last December Thomas and his research team at Penn State, in collaboration with partners in Europe and Africa, received a five-year, $10.2 million grant from the Bill and Melinda Gates Foundation to investigate a new method for preventing the transmission of malaria.

“The method involves limiting mosquito access to houses by blocking openings and installing ‘eave tubes' that contain a unique type of insecticide-laced mosquito netting developed by Dutch partner In2Care that kills the insects as they attempt to enter,” according to a Penn State news release.

Thomas was quoted as saying: “Nearly half of the world's population is at risk of contracting malaria, and according to the most recent World Health Organization report, an estimated 438,000 people died from the disease in 2015. The use of insecticides to control mosquitoes has saved millions of lives, but this tactic is increasingly challenged because mosquitoes quickly evolve resistance to the very limited number of insecticides currently used in public health. The eave tube approach presents a novel strategy to help combat this challenge by simultaneously making houses more mosquito proof and providing a novel way of delivering insecticides, which creates opportunities for using a wider range of insecticidal products."  

"The small amount of insecticide used in the tubes means that it is cheap to treat an entire house," said Thomas. "Furthermore, retreatment is easy, as it requires simple replacement of small pieces of netting within the tubes."  

Internationally recognized, Thomas is a recipient of the Commonwealth Scientific and Industrial Research Organization (CSIRO) Medal for Research Achievement, is a fellow of the American Association for the Advancement of Science, and an honorary professor at the University of Witwsatersand, South Africa. He also received Penn State's Alex and Jessie Black Award for Research Excellence.

DAVIS--A small chemical discovered in the Bruce Hammock laboratory at the University of California, Davis, may be a new, innovative tool to control depression, a severe and chronic psychiatric disease that affects 350 million persons worldwide.

The research, published March 14 in the journal Proceedings of the National Academy of Sciences, involves studies of an inhibitor of soluble epoxide hydrolase in rodents. Soluble epoxide hydrolase, or sEH, is emerging as a therapeutic target that acts on a number of inflammatory or inflammation-linked diseases.

“The research in animal models of depression suggests that sEH plays a key role in modulating inflammation, which is involved in depression,” said Hammock, a distinguished professor of entomology with a joint appointment at the UC Davis Comprehensive Cancer Center. “Inhibitors of sEH protect natural lipids in the brain that reduce inflammation, and neuropathic pain. Thus, these inhibitors could be potential therapeutic drugs for depression.”

Researchers from Hammock's laboratory, collaborating with depression expert Kenji Hashimoto and colleagues at the Chiba University Center for Forensic Mental Health, Japan, examined the role of the potent sEH inhibitor known as TPPU, in a rodent model of depression, “social defeat.”

They found that TPPU displayed rapid effects in both inflammation and social defeat-stress models of depression. Expression of sEH protein was higher in key brain regions of chronically stressed mice was higher than in control mice, they found.

“Most drugs for psychiatric diseases target how neurons communicate; here we are targeting the wellness and environment of the neurons,” said UC Davis researcher Christophe Morisseau.

Said UC Davis researcher Karen Wagner: “The rapid antidepressant action of the sEH inhibitor in these murine models of depression is truly noteworthy because current antidepressants used in humans and animal models take weeks to have full effects.”

The researchers also discovered that postmortem brain samples of patients with psychiatric diseases, including depression, bipolar disorder, and schizophrenia, showed a higher expression of sEH than controls.

The researchers found that pretreatment with TPPU prevented the onset of depression-like behaviors in mice after induced inflammation or repeated social-defeat stress. Mice lacking the sEH gene did not show depression-like behavior after repeated social-defeat stress.

“All these findings suggest that sEH plays a key role in the pathophysiology of depression and that epoxyfatty acids, and their mimics as well as sEH inhibitors, are potential therapeutic or prophylactic drugs for depression,” Hashimoto said.

Robert E. Hales, distinguished professor of clinical psychiatry and the Joe P. Tupin Endowed Chair of the Department of Psychiatry and Behavioral Sciences at UC Davis School of Medicine, said new medication treatment approaches are needed to treat depression. Hales, who was not involved in the research, said the new paper represents “an important and novel approach to treating depression.” 

“With lifetime prevalence rates of major depressive disorder being in the range of 16 percent and with nearly two-thirds of patients failing to respond to pharmacologic treatments, there is a pressing need to discover new medication treatment approaches,” Hales said. “Their findings lend support to the potential use of TPPU, a sEH inhibitor, as a new therapeutic medication to prevent and treat depression.”

Other authors on the paper are: Qian Ren, Min Ma, Tamaki Ishima, Ji-chun Zhang, Chun Yang, Wei Yao, Chao Dong, and Mei Han, Chiba University; and Jun Yang at UC Davis.  

Morisseau, Yang and Wagner are inventors on University of California patents related to soluble epoxide hydrolase. Some of these patents have been licensed by EicOsis Human Health, a Davis company founded by Hammock to develop pharmaceuticals to alleviate neuropathic and inflammatory pain.

The research was funded by Grant-in-Aid for Scientific Research on Innovative Areas of the Ministry of Education, Culture, Sports, Science and Technology, Japan to Kenji Hashimoto, (#24116006), and a Research Fellowship for Young Scientists of the Japan Society for the Promotion of Science (Tokyo, Japan) to Qian Ren. 

Partial support was provided by the National Institute of Environmental Health Sciences (NIEHS) R01 ES002710, NIEHS Superfund Research Program grant P42 ES004699,  and NIH U24 DK097154 West Coast Comprehensive Metabolomics Center.

Hammock and Professor Bruce German, UC Davis recently received a National Institutes of Health grant in collaboration with Pei-an Shih, UC San Diego Department of Psychiatry, to investigate the role of bioactive lipids in a related psychiatric disorder, anorexia nervosa.