Ultrastructure of the anal sacs in <Emphasis Type="Italic">Thalassema</Emphasis><Emphasis Type="Italic">thalassemum</Emphasis> (Annelida,Echiura)

The anal sacs of Thalassema thalassemum consist of an elongate tubular invagination (end sac) that is uniformly covered with numerous sessile ciliated funnels. While the funnels are composed of multi-ciliated, non-muscular cells and possess a ciliated neck-like constriction, the end sacs are lined by a simple epithelium of large, irregularly formed and sparsely ciliated cells that include masses of secretory granules. Podocytes are incorporated in the peritoneum that surrounds the anal sacs. A muscle grid consisting of inner longitudinal, outer circular and additional diagonal fibres that branch off of the circular fibres is embedded in the matrix between the end sac epithelium and peritoneum. Major structural differences between the hindgut and anal sacs support the hypothesis that the anal sacs are not gut derivatives but are instead part of a modified metanephridial system. Comparison of the anal sac morphology in Echiura reveals that T. thalassemum shares a tubular end sac with all known members of Thalassematinae and Ikedaidae, as well as with some members of Bonelliidae and Echiurinae, while the sessile funnels are apomorphic for the Thalassematinae.     

Temperature-dependent Allee effects in a stage-structured model for <Emphasis Type="Italic">Bythotrephes</Emphasis> establishment

Whether the invasive freshwater cladoceran Bythotrephes longimanus can establish after introduction into a water body depends on several biotic and abiotic factors. Among these, water temperature is important because both development rates and mode of reproduction (parthenogenetic or sexual) in Bythotrephes are influenced by temperature. We built a stage-structured model for the population dynamics of Bythotrephes based on the temperature-dependency of events in its life cycle and used the density of resting eggs at the end of each year to track changes in population density. The model was parameterized using data from published laboratory experiments and data on the Bythotrephes population in Harp Lake, Canada, from 1994 to 2005. The parameterized model was then used to simulate the outcome of invasions with different initial resting egg densities under different temperature regimes. A strong Allee effect emerged from the model, i.e. there is a critical threshold density above which the population can establish and below which it goes extinct. We showed analytically that the existence of an Allee effect arises from the model structure and is therefore robust to the parameter values. An increase in temperature reduces the establishment threshold for introductions in the same year as well as for introductions in the previous years. We therefore hypothesize that climate warming might facilitate Bythotrephes invasions. Finally, we study how the establishment threshold is influenced by the timing of the introduction event and thus identify time periods during the year when lakes may be particularly susceptible to Bythotrephes invasions.     

The presence of <Emphasis Type="Italic">Zygina</Emphasis> sp. and <Emphasis Type="Italic">Puccinia myrsiphylli</Emphasis> reduces survival and influences oviposition of <Emphasis Type="Italic">Crioceris</Emphasis> sp.

A leaf beetle, Crioceris sp. (Coleoptera: Chrysomelidae), was introduced into Australia as a biological control agent of bridal creeper (Asparagus asparagoides L. Druce) during October 2002. Rearing of Crioceris sp. is labour intensive therefore all releases of Crioceris sp. have been under 1000 individuals, which may be too low to ensure establishment if high mortality and high competition with other agents occurs. The aim of this study is to understand how the presence of two well-established biocontrol agents, a rust fungus (Puccinia myrsiphylli (Thuem) Wint [Basidiomycota: Uredinales]) and a leafhopper (Zygina sp. [Hemiptera: Cicadellidae]), might influence Crioceris sp. establishment. Crioceris sp. neonate larvae were placed on bridal creeper plants with or without the leafhopper and/or rust. The number of larvae that pupated was reduced by 38 and 65% in the presence of the rust fungus and leafhopper, respectively and by 45% in the presence of both agents. As the area infected by the rust increased the area damaged by the leafhopper decreased. The rust appeared to be negatively impacted by the presence of the leafhopper. In a second experiment, female Crioceris sp. adults were given a choice between uninfested bridal creeper plants and those infested with the rust or the leafhopper. The females preferred to lay their eggs on plants without leafhoppers but did not seem to be deterred by the presence of the rust. Consequently, the performance and impact of Crioceris sp. on bridal creeper may be reduced if populations overlap with the other biocontrol agents in the field.     

Frequencies of the <Emphasis Type="Italic">DRB1</Emphasis>, <Emphasis Type="Italic">DQA1</Emphasis>, <Emphasis Type="Italic">DQB1</Emphasis> and <Emphasis Type="Italic">TNFA</Emphasis> alleles in immigrant population of west Siberia

Based on population analysis of the DRB1, DQA1, DQB1 and TNFA allele frequency distribution patterns, regional features of immunogenetic structure of the population of West Siberia were investigated. Statistically significant linkage disequilibrium within the HLA class II region, as well as between the TNFA and DRB1, DQA1, and DQB1 was demonstrated. Population frequency distribution patterns of two- and multilocus haplotypes were examined.     

Morphological and molecular characterization of two ITS groups of <Emphasis Type="Italic">Erysiphe</Emphasis> (Erysiphales) occurring on <Emphasis Type="Italic">Syringa</Emphasis> and <Emphasis Type="Italic">Ligustrum</Emphasis> (Oleaceae)

ITS sequences determined for 53 Erysiphe specimens on Syringa and Ligustrum collected in Europe, East Asia, and North and South America were divided into two ITS groups, S and K types. Phylogenetic analysis showed that these two ITS types do not share a common ancestor and form separate clades. The K type on Ligustrum was identified as Erysiphe ligustri based on the three-dimensional branching pattern of appendages. Morphological observations showed that there are some morphological differences—pigmentation of appendages and number of ascospores per ascus—between the S and K types on Syringa. Based on these morphological observations, the S and K types on Syringa were identified as E. syringae and E. syringae-japonicae, respectively. The recent abundant production of chasmothecia by lilac powdery mildew in Europe was caused by E. syringae-japonicae introduced from East Asia. DNA sequence analyses of the rDNA ITS region and the 28S rDNA, tub2, CYP51, and Chs1 genes did not support an interspecific hybrid origin for E. syringae-japonicae. Haplotype analysis suggested that E. syringae originated in North America and independently migrated to East Asia and Europe/South America.     

The influence of <Emphasis Type="Italic">Myriophyllum verticillatum</Emphasis> and artificial plants on some life history parameters of <Emphasis Type="Italic">Daphnia magna</Emphasis>

Submerged macrophytes are known to serve as refuge for zooplankton but also seem to suppress the zooplankton growth. Thus, there is a conflict between the positive and negative role of macrophytes for zooplankton. We tested the influence of physical structure using artificial macrophytes, chemicals released by a macrophyte (Myriophyllum verticillatum), as well as the combined effects of these two factors on the life history of Daphnia magna. Daphnids matured at a smaller size and produced fewer eggs but larger individual offspring in the presence of artificial and real plants. Thus, under conditions with plants, we observed a trade off between number of eggs produced and the individual size of the offspring. Daphnids grown in the presence of exudates without plants were larger at maturity and showed no reduction in clutch size as compared with the control. We suggest that the macrophytes (real and artificial) negatively affected the daphnids in two ways: (1) food particles were settling down faster on the plant structures and this reduced the available food for Daphnia, (2) the plant structures were obstacles for the daphnids causing them to spent more energy during swimming. Both effects resulted in a reduced somatic growth, whereas the increased individual offspring size was probably a response to the reduced food level. Daphnia was not negatively affected by Myriophyllum exudates.     

The influence of predator regime on reproductive traits in <Emphasis Type="Italic">Gammarus</Emphasis> <Emphasis Type="Italic">pulex</Emphasis> populations

Selection on traits conferring reduced predation may be opposed by selection on other traits associated with reproduction. Here, we examined the hypothesis that traits associated with reproduction in Gammarus pulex are driven by predation. We studied G. pulex originating from ponds with two different kinds of predator regimes: (1) ponds with fish—often large, non-gap-limited predators and (2) ponds without fish where invertebrates are the dominant predators—often small, gap-limited predators with a much more restricted prey size range. We examined the body size of males and females in G. pulex amplexus pairs originating from fish and fishless ponds. We also examined, in the laboratory, their mating success, the number of offspring per female and offspring mortality under different rearing conditions, with or without fish cue. Mating success, defined as the percentage of amplexus pairs that produced live offspring, was higher for G. pulex from fishless ponds independent of rearing condition. Individuals from fish ponds were larger and they produced a higher number of offspring which tended to be related to female body size. Offspring mortality was higher in populations from fish ponds compared to populations from fishless ponds. Despite the higher offspring mortality, females from fish ponds had a higher number of offspring alive after 13 weeks, which is the approximate time it takes for G. pulex to reach maturity. Our data imply that no trade-off between reducing body size to reduce mortality caused by fish and maximising reproductive success exist in G. pulex from fish ponds. The strategy with many offspring may be the correct strategy in fishponds where predation pressure generally is higher than in fishless ponds.     

Alternative mating tactics of the gobiid fish <Emphasis Type="Italic">Bathygobius</Emphasis><Emphasis Type="Italic">fuscus</Emphasis>

The reproductive ecology of the gobiid fish Bathygobius fuscus was studied at Nobeoka, Miyazaki, Japan. Males of this species maintain small rock holes as a nest and females spawn an egg mass on the wall of the nest. The males employed two forms of mating tactic: nest holding and sneaking. A nest holder stayed in the nest and waited for a female to visit, whereas a sneaker intruded into a nest while a pair was engaged in reproduction. Males larger than 55 mm standard length were always nest holders; those of smaller size employed both tactics. As the larger males excluded the smaller males, the latter did not occupy a nest hole. With a decrease in the number of larger males, smaller males changed their mating tactic from sneaking to nest holding. The results suggest that male Bathygobius fuscus adopt a conditional strategy whereby they change their tactic depending on their social status. Electronic Publication     

Mating patterns of first-generation hybrids of the roach, <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.), and the silver bream, <Emphasis Type="Italic">Blicca bjoerkna</Emphasis> (L.)

Mating patterns among first-generation hybrids of the roach, Rutilus rutilus, and the silver bream, Blicca bjoerkna, between hybrids or with parent-species males, have been investigated under experimental reproduction conditions. The results reveal that the level of sexual activity of these hybrids is high. Hybrid females mated simultaneously and successively with all types of male, resulting in fertilised eggs. Individual participation of roach males in mating was never observed, however.     

A microsatellite-based test of the <Emphasis Type="Italic">Reticulitermes speratus</Emphasis> genetic caste determination model in <Emphasis Type="Italic">Coptotermes lacteus</Emphasis>

Coptotermes lacteus, a termite found in eastern Australia, is a central-site nester that constructs mounds up to 2 m in height. Mature colonies typically contain the primary king and queen, and up to a million or more worker and soldier offspring. Once a year, male and female nymphs are produced in approximately equal numbers and develop into new alates. Experimental removal of the queen in the field and subsequent mating of the king with a replacement queen, results in an unusual phenomenon whereby the production of female nymphs completely ceases, while the production of male nymphs, and workers of both sexes, continues. The proximate cause of this nymph male-bias is yet to be discovered. The production of male nymphs and workers of both sexes in de-queened C. lacteus colonies is equivalent to offspring production patterns in laboratory crosses of male nymphoid (nymph-derived) with female ergatoid (worker-derived) replacement reproductives in the related species Reticulitermes speratus. An X-linked genetically influenced caste determination (GCD) mechanism has been proposed to account for such offspring patterns in R. speratus. We examined microsatellite genotypes in C. lacteus to test a prediction arising from the R. speratus GCD model: that nymphs should result from reproduction by neotenics, rather than the primary pair. In five of six colonies examined, genotypes indicated that all workers and nymphs were derived from a single reproductive pair. In three of these cases, the primary queen was also located and examined; her genotype matched that inferred from worker and nymph genotypes. These results suggest that the GCD model proposed for R. speratus does not apply to C. lacteus, at least under field conditions. The male-nymph bias following queen removal therefore remains an unresolved issue in C. lacteus.     

Mapping species differences for adventitious rooting in a <Emphasis Type="Italic">Corymbia torelliana</Emphasis> × <Emphasis Type="Italic">Corymbia citriodora</Emphasis> subspecies <Emphasis Type="Italic">variegata</Emphasis> hybrid

Quantitative trait loci (QTL) detection was carried out for adventitious rooting and associated propagation traits in a second-generation outbred Corymbia torelliana × Corymbia citriodora subspecies variegata hybrid family (n = 186). The parental species of this cross are divergent in their capacity to develop roots adventitiously on stem cuttings and their propensity to form lignotubers. For the ten traits studied, there was one or two QTL detected, with some QTL explaining large amounts of phenotypic variation (e.g. 66% for one QTL for percentage rooting), suggesting that major effects influence rooting in this cross. Collocation of QTL for many strongly genetically correlated rooting traits to a single region on linkage group 12 suggested pleiotropy. A three locus model was most parsimonious for linkage group 12, however, as differences in QTL position and lower genetic correlations suggested separate loci for each of the traits of shoot production and root initiation. Species differences were thought to be the major source of phenotypic variation for some rooting rate and root quality traits because of the major QTL effects and up to 59-fold larger homospecific deviations (attributed to species differences) relative to heterospecific deviations (attributed to standing variation within species) evident at some QTL for these traits. A large homospecific/heterospecific ratio at major QTL suggested that the gene action evident in one cross may be indicative of gene action more broadly in hybrids between these species for some traits.     

<Emphasis Type="Italic">Bacillus anthracis</Emphasis>, <Emphasis Type="Italic">Francisella tularensis</Emphasis> and <Emphasis Type="Italic">Yersinia pestis</Emphasis>. The most important bacterial warfare agents — <Emphasis Type="Italic">review</Emphasis>

There are three most important bacterial causative agents of serious infections that could be misused for warfare purposes: Bacillus anthracis (the causative agent of anthrax) is the most frequently mentioned one; however, Fracisella tularensis (causing tularemia) and Yersinia pestis (the causative agent of plague) are further bacterial agents enlisted by Centers for Disease Control and Prevention into the category A of potential biological weapons. This review intends to summarize basic information about these bacterial agents. Military aspects of their pathogenesis and the detection techniques suitable for field use are discussed.     

Potential long-term storage of the predatory mite <Emphasis Type="Italic">Phytoseiulus</Emphasis><Emphasis Type="Italic">persimilis</Emphasis>

Increasing the ability to store mass-reared natural enemies during periods or seasons of low demand is a critical need of the biocontrol industry. We tested the hypothesis that chemicals can enhance long-term cold storage of a predatory mite Phytoseiulus persimilis Athias-Henriot. The research objective was to determine the effect of cryoprotectant and carbohydrate chemicals on in-storage survival of predators. In-storage survival at 8°C was greater for predators sprayed with glycerol (5%, v/v) or glucose (10% and 20%, v/v) than with water spray controls. After 74 days in the cryoprotectant experiment, predator survival declined to 11.5% in the 5% glycerol treatment and 7.8% in the water spray control. After 88 days in the carbohydrate experiment, predator survival declined to 22% in the 20% glucose treatment and 2% in the water spray control. Although many individuals expired within 50 days in both experiments, a few females survived more than 200 days. This research suggests that select cryoprotectants and carbohydrates have a limited capacity to facilitate long-term storage of P. persimilis.     

Biology of <Emphasis Type="Italic">Eretmocerus sudanensis</Emphasis> n. sp. Zolnerowich and Rose,parasitoid of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> Gennadius

Eretmocerus sudanensis = E. nr. emirates was released in 1992 into South Florida from Sudan to control Bemisia tabaci. It has since become the dominant Eretmocerus species in southwest Florida. Specimens were recovered at the Southwest Florida Research and Education Center in Collier County from a population of B. tabaci on collard Brassica oleracea, and the parasitoid described as new species, though as yet unpublished. Here we report results of studies conducted to evaluate the biology of this parasitoid of B. tabaci biotype B under laboratory controlled conditions (26°C ± 0.5, 13 h light, 62% ± 6 HR). No preoviposition period was observed for E. sudanensis. Females lived an average of 13.2 days and in this time deposited an average of 161 eggs at a mean oviposition rate of 13 eggs per day. The total compared favorably with published values for E. melanoscutus (123 eggs) and was similar to E. mundus (171 eggs). E. sudanensis showed the same tendencies of preference and suitability for the intermediate host stages (2nd and 3rd) as reported for these same 2 species. However, parameters such as development time from egg to adult (16 days) and net reproductive rate (Ro = 91.3 eggs/female) were shorter and greater, respectively, compared to published results for either E. melanoscutus or E. mundus under similar conditions. Such differences in demographic parameters could indicate a significantly greater reproductive potential for E. sudanensis.     

Life cycle and mating behavior of <Emphasis Type="Italic">Helicotylenchus multicinctus</Emphasis> (Nematoda: Hoplolaimidae) on excised <Emphasis Type="Italic">Musa cavendishii</Emphasis> roots

The life cycle and mating behavior of Helicotylenchus multicinctus (Nematoda: Hoplolaimidae) were observed in vitro on excised roots of Musa cavendishii in gnotobiotic culture. Eggs hatched into juveniles whose appearance and structure were similar to those of the adults. Juveniles grew in size and each juvenile stage was terminated by a molt. H. multicinctus had four juvenile stages. The first molt occurred outside the egg shortly after hatching. After the final molt the juveniles differentiated into adult males and females. Mating was required for reproduction. After mating, fertilized females began to lay eggs. The life cycle from second stage juvenile to second stage juvenile was completed in 39 days.     

Effective number of breeding adults in Oregon spotted frogs (<Emphasis Type="Italic">Rana</Emphasis><Emphasis Type="Italic">pretiosa</Emphasis>): genetic estimates at two life stages

We used genetic methods to estimate the effective number of breeders (N _b) in a population of Rana pretiosa, an imperiled amphibian in western North America. Microsatellite data was gathered from large samples of adults, eggs, and juveniles collected in 2006. We wished to determine where in the life cycle the greatest reductions in N _b occur, and to compare genetic estimates of N _b to an egg mass count estimate of the number of breeding adults. We predicted that N _b estimated at the metamorph stage would be reduced by increased variance in family size due to egg mass mortality. Contrary to our prediction, estimates of N _b at the egg and metamorph stages were similar. Thus, we found no evidence of inflated variance in family size between the two stages. If our results for this population are typical for R. pretiosa, then increased variance in family size during the egg to metamorph stage may not be a strong factor in reducing the effective population sizes (N _e) relative to the census sizes (N) in this species.     

Detecting spatial interactions in the ragweed (<Emphasis Type="Italic">Ambrosia artemissifolia</Emphasis> L.) and the ragweed beetle (<Emphasis Type="Italic">Ophraella communa</Emphasis> LeSage) populations

We observed a weed (Ambrosia artemissifolia)–beetle herbivore (Ophraella communa) system for three years in a spatially continuous field (≈200 ha). We analyzed our field data in the light of two contrasting theories: the resource-concentration hypothesis and reaction–diffusion theory. For the resource-concentration hypothesis, we calculated the correlation coefficients between weed and beetle abundances for every season in each year. Although we found weak support for resource concentration in some seasons, we could not find any clear relationships in other seasons. We discuss a dispersal-based mechanism to explain the differences observed among seasons in lieu of the resource-concentration hypothesis. For the reaction–diffusion theory, we estimated the nonparametric spatial covariance functions for the spatial autocorrelation of weeds and beetles. Although we could not find any strong spatial structure for the individual species, we found evidence of spatial interactions between weeds and beetles using time lagged cross-correlation functions. Weed abundance enhanced local beetle abundance. Through time, there was evidence of beetle spillover to adjacent locations at roughly the one beetle-generation time scale. Sites with large number of beetles did not seem to reduce subsequent weed abundance.     

Rhizosphere competent <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> in the management of <Emphasis Type="Italic">Heterodera cajani</Emphasis> on sesame

Biological control of the cyst forming nematode Heterodera cajani was studied on sesame using plant growth promoting rhizobacteria (PGPR) Pseudomonas aeruginosa LPT3 and LPT5. Based on plant growth promoting attributes, two fluorescent pseudomonads, LPT3 and LPT5 were evaluated for their efficacy against cyst forming nematode Heterodera cajani that parasitize Sesamum indicum. Pseudomonas aeruginosa LPT5 produced IAA, HCN, chitinase, glucanase and siderophore, and also solubilized inorganic phosphate in vitro. Moreover, LPT5 resulted in mortality of second stage juveniles of H. cajani, which was 13% higher as compared to P. aeruginosa LPT3. Interestingly, when both strains were inoculated together for the management of H. cajani on Sesamum indicum the population of H. cajani was reduced significantly, in field trial. Approximately 60% reduction in cyst and juveniles population was recorded with LPT5 coated seeds, while LPT3 resulted in 49% reduction in cyst and juvenile population as compared to control. Plants grown with seeds bacterized with LPT5 and reduced doses of urea, diammonium phosphate (DAP), muriate of potash (K) and gypsum gave maximum increase in yield, in comparison to that of plants raised under the influence of recommended or full doses of the chemical fertilizers. Pseudomonas aeruginosa LPT5 also showed excellent root colonization.     

A role of <Emphasis Type="Italic">ygfZ</Emphasis> in the <Emphasis Type="Italic">Escherichia coli</Emphasis> response to plumbagin challenge

Plumbagin is found in many herbal plants and inhibits the growth of various bacteria. Escherichia coli strains are relatively resistant to this drug. The mechanism of resistance is not clear. Previous findings showed that plumbagin treatment triggered up-regulation of many genes in E. coli including ahpC, mdaB, nfnB, nfo, sodA, yggX and ygfZ. By analyzing minimal inhibition concentration and inhibition zones of plumbagin in various gene-disruption mutants, ygfZ and sodA were found critical for the bacteria to resist plumbagin toxicity. We also found that the roles of YgfZ and SodA in detoxifying plumbagin are independent of each other. This is because of the fact that ectopically expressed SodA reduced the superoxide stress but not restore the resistance of bacteria when encountering plumbagin at the absence of ygfZ. On the other hand, an ectopically expressed YgfZ was unable to complement and failed to rescue the plumbagin resistance when sodA was perturbed. Furthermore, mutagenesis analysis showed that residue Cys228 within YgfZ fingerprint region was critical for the resistance of E. coli to plumbagin. By solvent extraction and HPLC analysis to follow the fate of the chemical, it was found that plumbagin vanished apparently from the culture of YgfZ-expressing E. coli. A less toxic form, methylated plumbagin, which may represent one of the YgfZ-dependent metabolites, was found in the culture supernatant of the wild type E. coli but not in the ΔygfZ mutant. Our results showed that the presence of ygfZ is not only critical for the E coli resistance to plumbagin but also facilitates the plumbagin degradation.