Jim McNeil

A Gene for an Extended Phenotype

An insect virus gene controls the behavior of the dying host to increase dispersion of the virus. Manipulation of host behavior by parasites and pathogens has been widely observed, but the basis for these behaviors has remained elusive. Gypsy moths infected by a baculovirus climb to the top of trees to die, liquefy, and “rain” virus on the foliage below to infect new hosts. The viral gene that manipulates climbing behavior of the host was identified, providing evidence of a genetic basis for the extended phenotype.

Contributions of immune responses to developmental resistance in Lymantria dispar challenged with baculovirus

How the innate immune system functions to defend insects from viruses is an emerging field of study. We examined the impact of melanized encapsulation, a component of innate immunity that integrates both cellular and humoral immune responses, on the success of the baculovirus Lymantria dispar multiple nucleocapsid nucleopolyhedrovirus (LdMNPV) in its host L. dispar. L. dispar exhibits midgut-based and systemic, age-dependent resistance to LdMNPV within the fourth instar; the LD(50) in newly molted larvae is approximately 18-fold lower than in mid-instar larvae (48-72h post-molt). We examined the role of the immune system in systemic resistance by measuring differences in hemocyte immunoresponsiveness to foreign targets, hemolymph phenoloxidase (PO) and FAD-glucose dehydrogenase (GLD) activities, and melanization of infected tissue culture cells. Mid-instar larvae showed a higher degree of hemocyte immunoresponsiveness, greater potential PO activity (pro-PO) at the time the virus is escaping the midgut to enter the hemocoel (72h post-inoculation), greater GLD activity, and more targeted melanization of infected tissue, which correlate with reduced viral success in the host. These findings support the hypothesis that innate immune responses can play an important role in anti-viral defenses against baculoviruses and that the success of these defenses can be age-dependent.

Pathogenesis of Lymantria dispar multiple nucleopolyhedrovirus in L. dispar and mechanisms of developmental resistance.

Lymantria dispar has a long historical association with the baculovirus Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV), which is one of the primary population regulators of L. dispar in the field. However, host larvae exhibit strong developmental resistance to fatal infection by LdMNPV; the LD50 in newly moulted fourth instars is 18-fold lower than in the middle of the instar (48-72 h post-moult). Using a recombinant of LdMNPV expressing lacZ, we examined the key steps of pathogenesis in the host to explore mechanisms of developmental resistance. At the midgut level, we observed reduced primary midgut infections in mid-fourth instars, indicating increased sloughing of infected cells. Additional barriers were observed as the virus escaped the midgut. Mid-fourth instars had higher numbers of melanized foci of infection associated with the midgut, apoptotic tracheal epidermal cells and haemocytes, and reduced numbers of infected haemocytes later in infection. Our results show that the co-evolutionary relationship between L. dispar and LdMNPV has resulted in both midgut-based and systemic antiviral defences and that these defences are age-dependent within the instar. This age-related susceptibility may contribute to how the virus is maintained in nature and could influence management of L. dispar by using the virus.

Using Environmental DNA to Connect Lab Science with Field Practice

Abstract Experiential learning helps students make connections between different skill sets and allows them to engage in a deeper level of inquiry. To enhance the connection between field and laboratory practice for undergraduate students in our wildlife ecology curriculum, we developed an exercise using environmental DNA (eDNA) analysis. eDNA sampling involves extracting and amplifying the DNA from specific organisms from an environmental sample, rather than from the organisms themselves, and has been rapidly adopted by conservation practitioners around the world. In our activity, students collect water samples from a local pond and process them to detect the presence of American bullfrogs. Practicing this procedure not only introduces them to professional skills they may utilize in their careers, but also helps create context for how laboratory science and field work support each other and can be used to connect to larger issues of conservation, environmental studies, or ecology.

The Smithsonian-Mason Semester for Conservation Studies: Advancing Innovative Ways to Teach the Practice of Conservation

The Smithsonian-Mason Semester for Conservation Studies is the cornerstone of an innovative partnership between George Mason University and the Smithsonian Institution, established to educate future conservation practitioners in an experiential framework. This 16-credit residential program addresses complex conservation imperatives within diverse disciplines, including the biological, physical, and social sciences. We aim to teach conservation as conservation is practiced, engaging students in real-world experiences. The semester is rooted in an integrative teaching design, focusing on dialogue and problem-solving using case studies in immersive field and laboratory experiences. Students learn from a large number of conservation practitioners and professionals, often up to 50 in one semester, enabling a collaborative atmosphere in which students develop a professional network. Class sizes are kept deliberately small so that students may engage in intensive mentoring with faculty. Since the beginning of the program in 2008, faculty have been using a pre- and post-semester learning gains assessment, including quantitative and qualitative questions, to gauge student understanding of the academic subject matter and their proficiency with professional skills. Data from these assessments will be compiled and reviewed to evaluate student learning gains of complex skills within the field of conservation and investigate long-term career development outcomes of alumni.

The Ecology of Death: Forensic Entomology as a Teaching Tool

ABSTRACT Describing the progression of insects that arrive at a cadaver can be a useful and exciting tool for teaching students about complex concepts such as ecological succession.