- Author: Kathy Keatley Garvey
But newly published research by UC Davis agricultural entomologist Christian Nansen and insect physiologist Michael Strand of the University of Georgia reveals a new, non-destructive and quite accurate method to characterize physiological responses to parasitism: proximal remote sensing or body reflectance response data.
They published their research, “Proximal Remote Sensing to Non-Destructive Detect and Diagnose Physiological Response by Host Insect Larvae to Parasitism,” Dec. 4 in the journal Frontiers in Physiology.
Nansen, first author of the paper and an associate professor in the UC Davis Department of Entomology and Nematology, specializes in insect ecology, integrated pest management and remote sensing. Strand, a professor of entomology at the University of Georgia, is an international authority on the physiology of insect parasitism.
The Nansen-Strand project involved soybean loopers without parasitism (control group) and with parasitism, involving both wasp species.
“Based on reflectance data acquired three to five days post-parasitism, all three treatments (control larvae, and those parasitized by either M. demolitor or C. floridanum) could be classified with more than 85 percent accuracy,” they wrote.
Due to parasitism-induced inhibition of growth, “it's easy to differentiate soybean loopers parasitized by M. demolitor from non-parasitized larvae as long as the developmental stage of the host larva is known,” they said. In addition, a single M. demolitor offspring emerges from the host larva 7-9 days post-parasitism to pupate, while non-parasitized larvae continue to increase in size to the final instar.
Copidosoma floridanum minimally alters host growth until late in the final instar, when thousands of wasp progeny complete their development. This wasp is known for having the largest recorded brood—3,055 individuals--of any parasitoidal insect.
Parasitoids are often categorized as either idiobionts--whose hosts cease development after parasitism--or koinobionts--whose hosts continue to develop as the parasitoids offspring grow. “Parasitoids also are commonly divided into ectoparasitic species whose offspring grow by feeding externally on hosts or endoparsitoids, whose offspring grow by feeding internally,” the authors wrote. “Most known idiobionts are either ectoparasitoids that paralyze and lay eggs on the surface of larval stage hosts or are endoparasitoids that lay their eggs inside sessile host stages like eggs or pupae.”
Both of the wasps they studied are idiobionts and endoparasitoids.
Nansen noted that “many species of minute wasps are parasitoids of eggs and larvae of other insects, and parasitism represents one of the most extreme life strategies among animals”
“Living inside the body of another animal,” he said, “poses a series of non-trivial challenges, including how to overcome/suppress the defense response by the host; how to obtain oxygen; how to feed on the host without killing it--because once the host is dead, then microbial organisms and general decomposition will make the host body unsuitable--and how to manage waste.”
Nansen likened the developing parasitoids to astronauts flying in a space capsule. “A developing parasitoid faces a long list of serious practical challenges, so the evolutionary selection pressure has been immense and lead to some of the most extreme cases of co-evolution.”
- Author: Kathy Keatley Garvey
The seminar is from 12:10 to 1 p.m.
"Mosquitoes are well recognized as the most important arthropod vectors of disease-causing pathogens," Strand says in his abstract. "Interest in the gut microbiota of mosquitoes has risen recently as a potential tool for manipulating vector competency. In contrast, much less is known about the role of this community in mosquito growth, development and reproduction. In this talk I will discuss recent results from our lab group regarding the composition of the gut microbiome in different mosquito species and insights we have gained about the function of this community in mosquito biology and evolution."
Strand focuses his research in the areas of parasite-host interactions, virology, immunity and development. Current projects center on virus-host interactions, function of the insect immune system, and regulation of reproduction in mosquitoes and other insects.
Strand was nominated as a seminar speaker by Professor Shirley Luckhart, Department of Medical Microbiology and Immunology, UC Davis School of Medicine and a graduate student advisor, UC Davis Department of Entomology and Nematology; Associate Dean Ed Lewis of the College of Agricultural and Environmental Sciences and professor and vice chair of the UC Davis Department of Entomology and Nematology; and Distinguished Professor James R. Carey, UC Davis Department of Entomology and Nematology.
A native of Norfolk, Va., Strand grew up in Texas. He received both his bachelor's degree in entomology (1980) and his doctorate in entomology (1985) from Texas A&M University, College Station. He accepted a fellowship from the National Science Foundation-North Atlantic Treaty Organization (NATO) as a postdoctoral scholar at the Imperial College, University of London in 1986. He then accepted a position as an assistant professor at Clemson University. In 1987, joined the faculty of the University of Wisconsin-Madison where he advanced to the position of professor. In 2002, Strand moved to the University of Georgia where he holds appointments in the Department of Entomology, the Center for Tropical and Emerging Global Diseases, Faculty of Infectious Diseases, and Department of Genetics.
Strand is a fellow of the Entomological Society of America (selected in 2012) and the American Association for the Advancement of Science (2008). ESA presented him with the national recognition award in the Physiology, Biochemistry and Toxicology Section in 2009. He served as president of the section in 2013.
Plans call for his seminar to be video-recorded and then posted at a later date on UCTV. The departmental seminars are coordinated by Professor Steve Nadler.