Insect Physiology Laboratory
Donnelly Science Room 227a
Loyola College in Maryland
Baltimore, Maryland 21210
Tel (410) 617-2582 (IPL phone)
(410) 617-5967 (Fly Lab)
Email: drivers@loyola.edu
Current
Areas of Interest
„ Evolution of
parasitism in ectoparasitic wasps
„ Modes of action
of parasitic wasp venoms
„ Gene expression
and regulation of venom proteins
„ Biochemical and
physiological adaptations associated with stress
Summary of
Recent Work
My research is directed
toward the evolution of host-parasite relationships. I am interested in the interactions that occur between
parasitic insects and their hosts.
Specifically, I study the
behavioral and biochemical adaptations that result from parasitic invasions of
holometabolous insects. Over the
last several years, my attention has been focused toward 4 areas: 1) parasite
regulation of host developmental and nutritional program in relation to the
reproductive strategy (gregarious versus solitary) employed by ectoparasitic
wasps, 2) acquisition of cold tolerance in ectoparasitic wasps, particularly in
relation to the influence of host species, 3) immunological responses of filth
flies to parasitism by ectoparasitoids, and 4) modes of action of parasitic
wasp venoms.
My current research efforts
are aimed at discovering how parasitic insects "regulate" the
internal environment of their hosts.
In my previous work, I have demonstrated that the gregarious,
ectoparasitic wasp, Nasonia vitripennis, uses a nonparalytic venom to halt development of its fly
host, and then redirects fly lipid metabolism. An elevation of fly lipids is essential for the successful
development of the parasite's offspring. Other wasp species that I have studied are
"less" gregarious or are solitary, and their venoms do not induce the
same host responses. One long-term
goal is to evaluate the regulation of host lipid biosynthesis by these wasp
venoms by examining the synthesis and activity of the fly fatty acid synthetase
complex, as well as parasite incorporation of host lipids. My research will attempt to demonstrate
control of host lipid metabolism through venom-mediated regulation of host
juvenile hormone synthesis. I will
also continue efforts to isolate the active venom fractions and perform
characterization experiments. I
believe the results of these experiments will show that the composition, and
thus activity, of ectoparasitic wasp venoms yield insight into the reproductive
strategy used by the parasites.
Most students that have
worked with me in research have been interested in modes of action studies with
parasitic wasp venom.
Through their efforts, we have established an in vitro method of examining the action of venom
from N. vitripennis on
2 cell lines using fluorescent microscopy and video imaging. Our recent work indicates that
wasp venom induces death in cultured cells by elevating Na+ influx
that appears to trigger a signal transduction response involving both
phospholipase C and phospholipase A2. Measurements of intracellular calcium using fluo-4 AM
has revealed that within 30 minutes after exposure, venom induces an increase
in cytosolic [Ca]i that continues to increase until cell death. This
venom-mediated increase in Ca+2 is apparently due to mobilization of
intracellular stores since the changes occurred in the absence of extracellular
Ca+2. Subsequent
analysis suggests that the membrane potential of mitochondria, as well as
mitochondrial stores of calcium, decline concurrently with elevations in
cytosolic calcium levels. Phospholipase C (PLC) inhibitors, neomycin and
U-73122, can block the venom-induced death temporarily (<3 hours), but by 24
h, all venom-treated cells swell and lyse. Pre-treatment of cells with caffeine or theophylline but not
ryanodine attenuate the induction of oncosis by wasp venom. Anti-inflammatory peptide 1
(antiflammin 1) but not bromophenacyl bromide, agents that block phospholipase
A2 (PLA2) activity, abolish the responsiveness of
BTI-TN-5B1-4 cells to venom. These
results suggest that venom initiates cell death by inducing Ca+2
release from intracellular stores probably via phospholipase C and IP3. Many of the details along the cytotoxic
pathway are still to be worked out, and several student projects can be
developed from this research.
Additionally, the action of this parasitic wasp venom parallels what is
known about the mechanism of mastoparan, a potent toxin from several species of
social wasps. I have initiated
studies comparing the action of the two types of toxins and plan to compare
receptor binding sites once purification of toxins from N. vitripennis venom is completed. Such comparisons will also lead
to evolutionary comparisons of venoms from parasitic and social Hymenoptera, which
use their venoms for entirely different functions (reproduction vs.
defense).
I have also started examining
behavioral and biochemical responses utilized by insects to cope with
environmental stress, such as cold temperatures and food shortage. My initial efforts have demonstrated a
relationship between biochemical mechanisms used for acquisition of cold
tolerance and parasite-mediated alterations in host metabolism. Specifically, the parasitic wasp N.
vitripennis can acquire
glycerol and alanine from its fly host to prevent freezing of wasp
tissues. Wasp venom triggers an
elevation of alanine in host hemolymph, suggesting that host-aided cold
temperature acquisition is an adaptive strategy. The wasp also obtains protection from desiccation and
chilling injury by being physically housed in the hostÕs puparium. Studies will be conducted to determine
if this creates a thermal lag within the puparium or if unstirred air
sandwiched between layers of host tissue can insulate these poikilotherms. Additionally, I plan to test
other species of parasitic wasps, particularly those that are sold commercially
for use as biological control agents, because winter mortality is a major
factor limiting the success of these insects in controlling flies. It may be possible, then, to rear
parasitoids on hosts with elevated cryoprotectent levels in order to increase
cold temperature survivorship.
This work will also aim to place insect parasitism in the context of seasonal
adaptations used by insects. I
believe that this aspect of my research program will be particularly attractive
to students with interests in ecology and environmental physiology.
The most recent initiative
of my laboratory has been to examine the immunological response of flesh fly
pupae to venom from N. vitripennis. Unlike
endoparasitic species that have been extensively studied for their ability to
alter host immune responses, very little is known about what ectoparasitic
wasps may due. Our observations
reveal that venom immediately suppresses the ability of plasmatocytes to
recognize and attach to membranes, beads, or bacteria. The numbers of circulating
plasmatocytes is diminished almost
immediately after envenomation, and the cell numbers never recover
during the entire length of the host-parasite relationship. The second most prominent defense cell
type in flesh flies, granulocytes, also loss the ability to adhere to
substrates, but the cell death is not induced by wasp venom. Staining of both hemocyte types with
phallidicin suggests that altered morphology is due to rearrangement of the
cytoskeleton.
I plan to examine
whether this rearrangement is elicited by changes in intracellular calcium
pools. Additional studies
will be performed to determine whether suppression of host immune responses is
adaptive for N. vitripennis.
This host-parasite relationship
has proven to be a model system for studying metazoan parasitesÕ interactions
with their arthropod hosts. The work of my students and myself will continue to
provide new insight into behavioral and biochemical adaptations associated with
parasitism, and will help elucidate the mechanisms controlling invertebrate
proliferation and development.
Michael Abt
Fall 2005-Spring
2006. Characterization of host cellular
defenses during parasitism.
Bridget Keenan
Fall 2005-Spring
2006. Mode of action of
venom from Pimpla
turionella.
Mark Antonino/
Tom Bujold
Fall 2005-Spring
2006. Role of wasp larvae in suppressing host
cellular
defenses.
Eddie Meinhold
Fall 2005-Spring
2006. Comparison of the insecticidal
properties of venom
from Melittobia digitata and M. australica.
Jackie Francis
Fall 2005-Spring
2007. Construction and characterization of
a
cDNA
library from venom glands of Nasonia vitripennis.
Julianne Viola
Spring 2006. Mitchondrial respiration in envenomated pupae of Sarcophaga
bullata.
Ashley Brogan
Fall-2006-Spring
2007. Role of calrecticulin in the intoxication
pathway of venom
from Nasonia vitripennis.
Mike Reinneman
Fall 2006-Spring
2007. (joint project with
Dr. Donald Keefer) Ultrastructural changes
in
tissues from Sarcophaga bullata parasitized by Nasonia vitripennis.
Rivers, D.B.
2004. Evaluation of host
responses as means to assess ectoparasitic
pteromalid waspÕs potential for controlling
manure-breeding flies. Biological
Control
30: 181-192.
Rivers, D.B.,
J. Zdarek, and D.L. Denlinger 2005. Disruption of pupariation and eclosion
behavior in the flesh fly, Sarcophaga
bullata Parker (Diptera:
Sarcophagidae), by
venom from the ectoparasitic wasp Nasonia
vitripennis (Walker)
(Hymenoptera:
Pteromalidae). Archives of Insect Biochemistry and
Physiology 57:78-91.
Rivers, DB, T. Crawley, and H.
Bauser, 2005 Localization of intracellular calcium
release in cells injured by venom from the ectoparasitoid Nasonia
vitripennis (Walker)
(Hymenoptera: Pteromalidae) and dependence of calcium mobilization on
G-protein
activation. Invited
submission to the special issue of the Journal of Insect Physiology,
Pauline Lawrence, editor.
51: 149-160.
Rivers, D.B., F. Ukan, , and E. Ergin, 2006.
Characterization and biochemical analyses
of venom from the ectoparasitic wasp Nasonia vitripennis (Walker) ((Hymenoptera:
Pteromalidae). Archives of Insect
Biochemistry and Physiology 61: 24-41.
Ergin, E., F. Ukan, D.B. Rivers, O.
Sak. 2006. In vivo and in vitro activity of venom
from
the endoparasitic wasp Pimpla turionellae (L.) Hymenoptera: Ichneumonidae). Archives of
Insect Biochemistry and Physiology, 61: 87-97.
Yoder, J. A., Benoit, J.B., Denlinger,
D.L., and Rivers, D.B 2006. Stress-induced
accumulation of glycerol in the flesh fly, Sarcophaga bullata Parker (Diptera:
Sarcophagidae): Evidence indicating anti-desiccant and cyroprotectant
functions for this
polyol during aseasonal stress. Journal of Insect Physiology 52:
202-214.
Ukan, F. Ergin, E., Rivers, D.B., and
Gencer, N. 2006. Age and diet influence the
composition of venom from the endoparasitic wasp Pimpla turionellae L.
(Hymenoptera: Ichneumonidae).
Archives of Insect Biochemistry and Physiology, 63:
177-187.
Deyrup, L.D., Rivers, D.B. and
Matthews, R.W. 2006. Venom from the ectoparasitic wasp
Melittobia digitata Dahms (Hymenoptera: Eulophidae) induces paralysis and
developmental delay in natural and factitious hosts. Annals of the
Entomological Society of America, 99(6): 1199-1205.
Abt, M. and Rivers, D.B. Characterization of phenoloxidase
activity in venom from the
ectoparasitoid Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae). Journal of
Invertebrate Pathology, In press.
Rivers, D.B.,
Ergin, E. and Ukan, F. 2006.
Cell death in the host-parasitoid relationship.
In: New developments in cell apoptosis
research (A.J. Corvin, Ed.), Nova Science
Publishers, New York.
__ denotes student authors.
Nasonia genome
project: http://www.rochester.edu/College/BIO/labs/WerrenLab/nasonia/genomeprojectindex.html
Nasonia links: http://www.rochester.edu/College/BIO/labs/WerrenLab/nasonia/nasonialinks.html
Werren Lab: http://www.rochester.edu/College/BIO/labs/WerrenLab/
Denlinger Lab: http://www.oardc.ohio-state.edu/entomology/personnelsingle.asp?strid=154
Beckage Lab: http://www.entomology.ucr.edu/people/beckage.html
Vinson Lab: http://vinsonlab.tamu.edu/
Ohio State
University: Entomology: http://www.oardc.ohio-state.edu/entomology/main.asp
North American
Forensic Entomology Association (NAFEA): http://www.nafea.net/
USDA: http://www.usda.gov/wps/portal/usdahome
Journal of
Insect Physiology: http://www.elsevier.com/wps/find/journaldescription.cws_home/231/description#description
Insect
Biochemistry and Molecular Biology: http://www.elsevier.com/wps/find/journaldescription.cws_home/390/description#description
Journal of
Invertebrate Pathology: http://www.elsevier.com/wps/find/journaldescription.cws_home/622883/description#description
Archives of
Insect Biochemistry and Physiology: http://www.wiley.com/WileyCDA/WileyTitle/productCd-ARCH.html
Entomological Association
of America: http://entsoc.org/