Blocked stomodeal valve of the insect vector: similar mechanism of transmission in two trypanosomatid models

The regurgitation of metacyclic stages from the sand fly cardia is thought to be the prevailing mechanism of Leishmania transmission. This regurgitation may result through damage of the stomodeal valve and its mechanical block by the parasites. We found this phenomenon in three sand fly-Leishmania models and also in avian trypanosomes transmitted by Culex mosquitoes. Phlebotomus duboscqi, Phlebotomus papatasi, Lutzomyia longipalpis, and Culex pipiens were membrane-fed on blood containing Leishmania major, Leishmania chagasi (syn. infantum) and an unidentified avian Trypanosoma from Trypanosoma corvi clade, respectively. Females with the late-stage infections were processed for the optical and transmission electron microscopy. Localization of the parasites and changes to the stomodeal valve were in some aspects similar in all vector-parasite pairs studied: (i) a large plug of flagellates was observed in cardia region, (ii) parasites were attached to the chitin lining of the stomodeal valve by the formation of zonal hemidesmosome-like plaques. Leishmania promastigotes were found both attached to the valve as well as unattached in the lumen of midgut. The stomodeal valve of infected sand flies was opened, its chitin lining was destroyed and the unique filamentous structures on the apical end of cylindrical cells were degraded. In the Culex-Trypanosoma model, the whole population of epimastigotes was found in close contact with the chitin lining, and degenerative changes of the valve were less pronounced. We suggest that the phenomenon involving a blocked valve facilitating the regurgitation of parasites into the vertebrate host may occur generally in heteroxenous trypanosomatids transmitted by the bite of nematoceran Diptera.     

Influence of parasitism and soil compaction on pupation of the green bottle fly,Lucilia sericata

The influence of parasitoids and soil compaction on pupation behavior of blow flies was examined in a host–parasitoid system involving Lucilia sericata (Meigen) (Diptera: Calliphoridae) and Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae). Larvae of L. sericata were introduced to containers with soil of different compaction levels, with or without parasitoids. Although females of N. vitripennis did not significantly affect the pupation depth of L. sericata, they increased the rate of pupal development by 15.0–23.7 h at 28.4 ± 1.2 °C, and increased the clumping of puparia. Pupation depth of L. sericata was negatively related to soil compaction; mean depth of pupation was 4.4 cm in uncompacted soil and 0.5 cm in high‐compaction soil. In high‐compaction soil, pupal development increased by 10.5–18.8 h at 25.2 ± 0.3 °C, and puparia were clumped. These results provide a framework for locating puparia in forensic investigations and releasing appropriate parasitoids for biological control of blow flies.     

Characteristics of Crataerina pallida (Diptera: Hippoboscidae) populations; a nest ectoparasite of the common swift, Apus apus (Aves: Apodidae)

An essential pre-requisite to understanding the nature of a host-parasite relationship is a good knowledge of the parasite’s ecology, including its life history. Despite removing a significant amount of blood from their common swift (Apus apus) hosts, no detrimental effect of parasitism by the louse fly (Crataerina pallida) has been found. This may be because little is known of the characteristics of the populations of this parasite. We studied the structure of louse fly populations that may influence its pathogenicity. High levels of prevalence were seen, with 100% of nests being parasitized during 2007 and 2008. Louse fly pupae were found to be aggregated, with a frequency distribution best described by the negative binomial model in 2006-2008. The mean parasitic load per nest was 3.72 ± 2.65 in 2007 and 4.21 ± 3.09 in 2008, much higher than that found in comparative studies. Louse fly numbers declined throughout the swift breeding season. Parasite populations were heavily female biased, except for at the initial and final stages of the nestling period.     

Field Release and Establishment of the Decapitating Fly Pseudacteon curvatus on Red Imported Fire Ants in Florida

Decapitating phorid flies in the genus Pseudacteon are being studied as classical biological control agents of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae). Pseudacteon curvatus Borgmeier (Diptera: Phoridae) is a small decapitating fly that attacks small fire ant workers. We released a biotype of P. curvatus from Formosa, Argentina, at three sites near Gainesville, FL. Field releases were conducted in the spring and summer of 2003 and monitored monthly. Flies were discovered within 5 weeks at the spring site and then monthly thereafter. By late spring 2004, flies released at this site had expanded 1.6 km both north and south and about 0.8 km westward. Initially, we found no flies from the two summer 2003 releases but we were successful at finding them 8 months after release during spring 2004. This paper documents the first successful release(s) of P. curvatus on red imported fire ants in the United States.     

Focal adhesions: what's new inside

The cytoplasmic side of focal adhesions is comprised of large molecular complexes that link transmembrane receptors, such as integrins, to the actin cytoskeleton and mediate signals modulating cell attachment, migration, proliferation, differentiation, and gene expression. These complexes are heterogeneous and dynamic structures that are apparent targets of regulatory signals that control the function of focal adhesions. Recent studies using genetic approaches in invertebrate and vertebrate systems have begun to reveal the structure and function of these complexes in vivo.     

Dispersal ability of marked,irradiated olive fruit flies [Bactrocera oleae (Rossi) (Diptera: Tephritidae)] in arid regions

The dispersal of marked, irradiated olive fruit flies originating from a hybrid laboratory strain was studied in an olive groove located in the arid regions of southern Israel. Release–recapture experiments (eight in total) were conducted throughout a period of 5 months (July–December 2008). In each experiment, ca. 5000 flies were released. Recapture of flies was conducted using a grid of 30 yellow sticky traps set in expanding semicircles from the centre of release. Service of traps was conducted 3 and 15 days after the release. Fly quality and adult food type (only sucrose and protein + sucrose) before release was also investigated. Results point at an average dispersal distance of marked, irradiated olive flies of ca. 50 m. Pre‐release adult diet did not affect dispersal ability. Fly recovery averaged ca. 3.5% during summer and ca. 1.5% during autumn. Most of the recovery concentrated during the first 3 days after releases, suggesting low survival of the released flies afterwards. As inferred from circular statistics, direction of dispersal was non‐random with a significant directionality to the north‐west. Results are discussed in view of environmental temperatures and wind direction.     

A field test for host fruit odour discrimination and avoidance behaviour for Rhagoletis pomonella flies in the western United States

Prezygotic isolation due to habitat choice is important to many models of speciation-with-gene-flow. Habitat choice is usually thought to occur through positive preferences of organisms for particular environments. However, avoidance of non-natal environments may also play a role in choice and have repercussions for post-zygotic isolation that preference does not. The recent host shift of Rhagoletis pomonella (Diptera: Tephritidae) from downy hawthorn, Crataegus mollis, to introduced apple, Malus domestica, in the eastern United States is a model for speciation-with-gene-flow. However, the fly is also present in the western United States where it was likely introduced via infested apples ≤ 60 years ago. R. pomonella now attacks two additional hawthorns in the west, the native C. douglasii (black hawthorn) and the introduced C. monogyna (English ornamental hawthorn). Flight tunnel tests have shown that western apple-, C. douglasii- and C. monogyna-origin flies all positively orient to fruit volatile blends of their respective natal hosts in flight tunnel assays. Here, we show that these laboratory differences translate to nature through field-trapping studies of flies in the state of Washington. Moreover, western R. pomonella display both positive orientation to their respective natal fruit volatiles and avoidance behaviour (negative orientation) to non-natal volatiles. Our results are consistent with the existence of behaviourally differentiated host races of R. pomonella in the west. In addition, the rapid evolution of avoidance behaviour appears to be a general phenomenon for R. pomonella during host shifts, as the eastern apple and downy hawthorn host races also are antagonized by non-natal fruit volatiles.     

Barcoding Queensland Fruit Flies (Bactrocera tryoni): impediments and improvements

Identification of adult fruit flies primarily involves microscopic examination of diagnostic morphological characters, while immature stages, such as larvae, can be more problematic. One of the Australia’s most serious horticultural pests, the Queensland Fruit Fly (Bactrocera tryoni: Tephritidae), is of particular biosecurity/quarantine concern as the immature life stages occur within food produce and can be difficult to identify using morphological characteristics. DNA barcoding of the mitochondrial Cytochrome Oxidase I (COI) gene could be employed to increase the accuracy of fruit fly species identifications. In our study, we tested the utility of standard DNA barcoding techniques and found them to be problematic for Queensland Fruit Flies, which (i) possess a nuclear copy (a numt pseudogene) of the barcoding region of COI that can be co‐amplified; and (ii) as in previous COI phylogenetic analyses closely related B. tryoni complex species appear polyphyletic. We found that the presence of a large deletion in the numt copy of COI allowed an alternative primer to be designed to only amplify the mitochondrial COI locus in tephritid fruit flies. Comparisons of alternative commonly utilized mitochondrial genes, Cytochrome Oxidase II and Cytochrome b, revealed a similar level of variation to COI; however, COI is the most informative for DNA barcoding, given the large number of sequences from other tephritid fruit fly species available for comparison. Adopting DNA barcoding for the identification of problematic fly specimens provides a powerful tool to distinguish serious quarantine fruit fly pests (Tephritidae) from endemic fly species of lesser concern.     

Behavior of Moose Relative to a Road Network

Abstract Roads often negatively affect terrestrial wildlife, via habitat loss or fragmentation, noise, and direct mortality. We studied moose (Alces alces) behavior relative to a road network, in an area with a history of moose-vehicle accidents, to determine when moose were crossing roadways or using areas near roads and to investigate if environmental factors were involved in this behavior. We tracked 47 adult moose with Global Positioning System collars in a study area crossed by highways and forest roads. We hypothesized that moose would avoid crossing roads but would make occasional visits to roadsides to feed on sodium-rich vegetation and avoid biting insects. Further, we expected moose avoidance to be greater for highways than forest roads. We recorded 196,710 movement segments but only observed 328 highway and 1,172 forest-road crossings (16 and 10 times lower than expected by chance). Moose usually avoided road proximity up to ≥500 m on each side but 20% of collared moose made visits to areas within 50 m of highways, which might have resulted from moose searching for sodium in vegetation and roadside salt pools. In fact, vegetation along highways had higher sodium concentrations and was browsed in similar proportions to vegetation in adjacent forest, despite moose avoidance of these zones. Moose, however, did not use areas near roads more during periods of biting insect abundance. Our results supported the hypothesis of scale-dependent selection by moose; avoidance of highways at a coarse scale may confer long-term benefits, whereas selection of highway corridors at finer scales may be part of a strategy to overcome short-term limiting factors such as sodium deficiency. We found a positive relationship between home-range size and the proportion of road axes they contained, suggesting that moose either compensated for habitat loss or made specific movements along highways to gather sodium. The presence of sodium along highways likely increases moose-vehicle accident risks. Removal of salt pools or use of a de-icing salt other than sodium chloride should render highway surroundings less attractive to moose.     

Prevention and treatment of tail biting in weaned piglets

The aims of this study were to evaluate four preventive measures and two curative treatments of tail biting. The preventive measures were: chain, rubber hose, straw rack (5 g/pig/day) and the provision of straw on the floor twice daily by hand (2 × 10 g/pig/day). The two curative treatments, which were applied following the onset of tail biting in a pen were: straw twice daily (as in the fourth preventive measure) and the removal of the biter. In total, 960 undocked weaned piglets (10 piglets per pen) were observed during 5 weeks. Tail lesions (none, bite marks and wounds) were recorded daily. The incidence of pens with wounded pig tails was significantly lower when straw was provided twice daily (8% of pens) compared to the chain (58% of pens) and rubber hose (54% of pens) treatment, but did not differ significantly from the straw rack treatment (29% of pens). Tails with bite marks were significantly less common in pens with twice daily straw (16% of pens) compared to chain (88% of pens), rubber hose (79% of pens) and straw rack (75% of pens). No significant difference was found between the curative treatments. Both treatments showed a reduced incidence of red fresh blood on the tails at days 1–9 following curative treatment, compared to day 0. However, neither curative treatment eliminated tail biting entirely. In conclusion, this study indicates that tail biting is best prevented with a small amount of straw, provided twice daily, and to a lesser extent with a straw rack, compared to providing a chain or a rubber hose. Once tail biting has occurred, providing a small amount of straw twice daily and removing the biter appears to be equally effective.