Olfactory Cues Are Subordinate to Visual Stimuli in a Neotropical Generalist Weevil

The tropical root weevil Diaprepes abbreviatus is a major pest of multiple crops in the Caribbean Islands and has become a serious constraint to citrus production in the United States. Recent work has identified host and conspecific volatiles that mediate host- and mate-finding by D. abbreviatus. The interaction of light, color, and odors has not been studied in this species. The responses of male and female D. abbreviatus to narrow bandwidths of visible light emitted by LEDs offered alone and in combination with olfactory stimuli were studied in a specially-designed multiple choice arena combined with a locomotion compensator. Weevils were more attracted to wavelengths close to green and yellow compared with blue or ultraviolet, but preferred red and darkness over green. Additionally, dim green light was preferred over brighter green. Adult weevils were also attracted to the odor of its citrus host + conspecifics. However, the attractiveness of citrus + conspecific odors disappeared in the presence of a green light. Photic stimulation induced males but not females to increase their speed. In the presence of light emitted by LEDs, turning speed decreased and path straightness increased, indicating that weevils tended to walk less tortuously. Diaprepes abbreviatus showed a hierarchy between chemo- and photo-taxis in the series of experiments presented herein, where the presence of the green light abolished upwind anemotaxis elicited by the pheromone + host plant odor. Insight into the strong responses to visual stimuli of chemically stimulated insects may be provided when the amount of information supplied by vision and olfaction is compared, as the information transmission capacity of compound eyes is estimated to be several orders of magnitude higher compared with the olfactory system. Subordination of olfactory responses by photic stimuli should be considered in the design of strategies aimed at management of such insects.     

Production,application, and field performance of Abietiv™, the balsam fir sawfly nucleopolyhedrovirus

Beginning in the early 1990s, the balsam fir sawfly (Neodiprion abietis) became a significant defoliating insect of precommercially thinned balsam fir (Abies balsamea (L.) Mill.) stands in western Newfoundland, Canada. In 1997, a nucleopolyhedrovirus (NeabNPV) was isolated from the balsam fir sawfly and, as no control measures were then available, NeabNPV was developed for the biological control of balsam fir sawfly. In order to register NeabNPV for operational use under the Canadian Pest Control Products Act, research was carried out in a number of areas including NeabNPV field efficacy, non-target organism toxicology, balsam fir sawfly ecology and impact on balsam fir trees, and NeabNPV genome sequencing and analysis. As part of the field efficacy trials, approximately 22 500 hectares of balsam fir sawfly-infested forest were aerially treated with NeabNPV between 2000 and 2005. NeabNPV was found to be safe, efficacious, and economical for the suppression of balsam fir sawfly outbreak populations. Conditional registration for the NeabNPV-based product, Abietiv™, was received from the Pest Management Regulatory Agency (Health Canada) in April 2006. In July 2006, Abietiv was applied by spray airplanes to 15 000 ha of balsam fir sawfly-infested forest in western Newfoundland in an operational control program.      

Impact of urban fragmentation on the genetic structure of the eastern red-backed salamander

Urban development is a major cause of habitat loss and fragmentation. Few studies, however, have dealt with fragmentation in an urban landscape. In this paper, we examine the genetic structure of isolated populations of the eastern red-backed salamander (Plethodon cinereus) in a metropolitan area. We sampled four populations located on a mountain in the heart of Montréal (Québec, Canada), which presents a mosaic of forested patches isolated by roads, graveyards and buildings. We assessed the genetic structure of these populations using microsatellite loci and compared it to the genetic structure of four populations located in a continuous habitat in southern Québec. Our results indicate that allelic richness and heterozygosity are lower in the urban populations. Exact differentiation tests and pairwise F _ST also show that the populations found in the fragmented habitat are genetically differentiated, whereas populations located in the continuous habitat are genetically homogeneous. These results raise conservation concerns for these populations as well as for rare or threatened species inhabiting urban landscapes.     

Importance of calcium for the binding of oviductal fluid proteins to the membranes of bovine spermatozoa

Our laboratory has recently shown that in vitro-cultured oviductal cells secrete sperm motility maintaining factor(s). Since the binding of oviductal proteins to spermatozoa (SPZ) has been demonstrated in many species, the motility factor was postulated to bind the membranes of SPZ. Therefore, the current study was performed to evaluate which proteins from in vivo oviductal secretions bind to sperm membranes, to characterize binding conditions, and to evaluate the effect of this binding on sperm survival. Bovine oviducts were dissected, and oviductal cells and fluid were collected by pressing the oviductal tube with a glass slide. This mixture was incubated in Tris-EDTA buffer at 37°C for 30 min, and the cells were washed twice by centrifugation. The supernatant containing oviductal fluid proteins (OFP) was reserved, filtered, frozen (for later motility tests), or lyophilized and labeled with ¹²⁵|. Frozen-thawed SPZ were incubated either immediately, following capacitation, ionophore-induced acrosome reaction, death by heating, or flagellar removal with labeled OFP for 30 min. The resulting pellet after three washes was dissolved in SDS and submitted to 10% SDS-PAGE. An autoradiogram showed that 72, 66, 39, 38, and 36 kDa proteins bind strongly to the five types of SPZ used, and that this binding is very specific, since unlabeled OFP inhibited binding while serum proteins did not. Furthermore, for 39, 38, and 36 kDa proteins, the presence of calcium in the incubation medium was essential for dose-dependent binding, whereas magnesium was not. Preincubation of SPZ for 30 min at 37°C with oviductal fluid, followed by one wash and 6 hr of incubation in control media, showed that the percentage of motile SPZ is significantly higher (52 ± 6%) compared with SPZ not preincubated with oviductal fluid (24 ± 6%: P < 0.01). In summary, a limited number of proteins from oviductal secretions bind to the surface of bovine SPZ only in the presence of calcium, and this binding appears to be important for subsequent sperm viability. © 1996 Wiley-Liss, Inc.     

Season‐long mating disruption of citrus leafminer,Phyllocnistis citrella Stainton,with an emulsified wax formulation of pheromone

The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is a major worldwide pest of citrus. Larval feeding by this insect facilitates proliferation of citrus bacterial canker, Xanthomonas axonopodis pv. citri. Herein, we describe a season‐long disruption trial of P. citrella with a newly developed, emulsified wax dispenser of pheromone (SPLAT‐CLM^TM). A formulation containing a 3 : 1 blend of (Z,Z,E)‐7,11,13‐hexadecatrienal:(Z,Z)‐7,11‐hexadecadienal at a 0.2% loading rate of active ingredient by weight and deployed twice per season (24 weeks total) at 490 g of formulation/ha caused season‐long disruption of male moth catch in pheromone traps as well as reduced leaf infestation. Analysis of pheromone release from dispensers by gas chromatography revealed that effective disruption of P. citrella occurred at a deployment rate of 126 μg of (Z,Z,E)‐7,11,13‐hexadecatrienal/ha/h. Direct observation of moth behaviour in the field suggested that disruption by this formulation occurred by a non‐competitive mechanism. A formulation of the 3 : 1 attractive blend at a 0.02% pheromone loading rate caused only 2–6 weeks of disruption per deployment and did not reduce leaf infestation during mid and end of the season evaluations. A formulation containing 0.2% of (Z,Z)‐7,11‐hexadecadienal alone and deployed at 490 g/ha caused 6–7 weeks of moth disruption to pheromone traps and did not prevent leaf infestation, while an identical formulation loaded with 0.02% (w/w) of (Z,Z)‐7,11‐hexadecadienal alone had no effect on P. citrella orientation to pheromone traps. The SPLAT formulation evaluated herein appears to be an excellent release device for (Z,Z,E)‐7,11,13‐hexadecatrienal given that approximately 100 days of steady release occurred following an initial brief (ca. 7 days) burst of higher release. The advantages of SPLAT as a formulation for P. citrella disruption include low cost of manufacturing, biodegradable and weather resistant characteristics, and flowability allowing machine application. Mating disruption should be an effective alternative to insecticides for management of P. citrella and may reduce the incidence of citrus canker.     

Anti-apoptotic effect of insulin on normal hepatocytes in vitro and in vivo

Liver growth factors are known to be anti-apoptotic for hepatocytes. The potential of insulin, a liver co-mitogen, has not been thoroughly evaluated. We studied the anti-apoptotic role of insulin on primary cultures of rat hepatocytes exposed to transforming growth factor-beta (TGF-beta) as the apoptotic agent and in the left portal vein ligation model (LVPL) of liver atrophy. Results show that insulin decreases apoptosis of TGF-beta-treated hepatocyte cultures by 43% (P < 0.002) and the alanine amino transferase (ALT) release by 49% (P < 0.001). Left lobes of LPVL animals displayed a significant increase in the levels of TGF-beta mRNA. In LPVL rats receiving continuous infusion of insulin in the left lobes, the weight of the atrophic lobes was higher over a 7-day period in comparison to control animals. This was associated with lower levels of serum ALT and with a five-fold decrease in the apoptotic index in the left lobes (P < 0.0001). Induction of Akt phosphorylation and increased expression of Bcl-xl were observed in the left lobes of insulin-treated animals. In conclusion, these results show that insulin is anti-apoptotic for normal hepatocytes both in vitro and in vivo and that the action of insulin is associated with increased Bcl-xl expression and Akt activation.     

Overexpression of Toll-like receptor 4 amplifies the host response to lipopolysaccharide and provides a survival advantage in transgenic mice

Toll-like receptors are transmembrane proteins that are involved in the innate immune recognition of microbial constituents. Among them, Toll-like receptor 4 (Tlr4) is a crucial signal transducer for LPS, the major component of Gram-negative bacteria outer cell membrane. The contribution of Tlr4 to the host response to LPS and to infection with virulent Salmonella typhimurium was studied in four transgenic (Tg) strains including three overexpressing Tlr4. There was a good correlation between the level of Tlr4 mRNA expression and the sensitivity to LPS both in vitro and in vivo: Tg mice possessing the highest number of Tlr4 copies respond the most to LPS. Overexpression of Tlr4 by itself appears to have a survival advantage in Tg mice early during infection: animals possessing more than two copies of the gene survived longer and in a greater percentage to Salmonella infection. The beneficial effect of Tlr4 overexpression is greatly enhanced when the mice present a wild-type allele at natural resistance-associated macrophage protein 1, another critical innate immune gene involved in resistance to infection with SALMONELLA: Tlr4 and natural resistance-associated macrophage protein 1 exhibit functional epistatic interaction to improve the capacity of the host to control bacterial replication. However, this early improvement in disease resistance is not conducted later during infection, because mice overexpressing Tlr4 developed an excessive inflammatory response detrimental to the host.