Salinity adaptation of the invasive New Zealand mud snail (Potamopyrgus antipodarum) in the Columbia River estuary (Pacific Northwest, USA): physiological and molecular studies

In this study, we examine salinity stress tolerances of two populations of the invasive species New Zealand mud snail Potamopyrgus antipodarum, one population from a high salinity environment in the Columbia River estuary and the other from a fresh water lake. In 1996, New Zealand mud snails were discovered in the tidal reaches of the Columbia River estuary that is routinely exposed to salinity at near full seawater concentrations. In contrast, in their native habitat and throughout its spread in the western US, New Zealand mud snails are found only in fresh water ecosystems. Our aim was to determine whether the Columbia River snails have become salt water adapted. Using a modification of the standard amphipod sediment toxicity test, salinity tolerance was tested using a range of concentrations up to undiluted seawater, and the snails were sampled for mortality at daily time points. Our results show that the Columbia River snails were more tolerant of acute salinity stress with the LC₅₀ values averaging 38 and 22 Practical Salinity Units for the Columbia River and freshwater snails, respectively. DNA sequence analysis and morphological comparisons of individuals representing each population indicate that they were all P. antipodarum. These results suggest that this species is salt water adaptable and in addition, this investigation helps elucidate the potential of this aquatic invasive organism to adapt to adverse environmental conditions.     

Cardinium is associated with reproductive incompatibility in the predatory mite Metaseiulus occidentalis (Acari: Phytoseiidae)

Cardinium, a bacterium from the Bacteroidetes group, is associated with reproductive manipulations such as cytoplasmic incompatibility, parthenogenesis, and feminization in some arthropod species. We, and others, have shown that Cardinium, but not Wolbachia, is an endosymbiont in some populations of Metaseiulus occidentalis, a phytoseiid mite that is an important predator of spider mite pests of agricultural crops. However, the precise biological effects that Cardinium may have on M. occidentalis remain unclear. In this study we show, in two sets of crosses between different colonies of Cardinium-free (C-) M. occidentalis females and Cardinium-containing (C+) males, that fecundity was reduced in parental females, F1 progeny survival rates were reduced, and fewer female progeny were produced when compared to the reciprocal and control crosses. There were no differences in these attributes in the reciprocal and two control crosses. Cardinium was transmitted maternally but there was no observed paternal transmission. Finally, Cardinium did not cause asexual (thelytoky) reproduction in M. occidentalis. Thus, Cardinium is associated with nonreciprocal reproductive incompatibility in M. occidentalis and our results support the hypothesis that Cardinium is a reproductive parasite in this agriculturally important predator. Cardinium may therefore affect the evolution and ecology of M. occidentalis and biological control efforts using this mite.     

Distinct roles of specific fatty acids in cellular processes: implications for interpreting and reporting experiments

Plasma contains a variety of long-chain fatty acids (FAs), such that about 35% are saturated and 65% are unsaturated. There are countless examples that show how different FAs impart specific and unique effects, or even opposing actions, on cellular function. Despite these differing effects, palmitate (C16:0) is regularly used to represent "FAs" in cell based experiments. Although palmitate can be useful to induce and study stress effects in cultured cells, these effects in isolation are not physiologically relevant to dietary manipulations, obesity, or the consequences of physiological concentrations of FAs. Hence, authors should avoid conclusions that generalize about "FAs" or "saturated FAs" or "high-fat diet" effects if only a single FA was used in the reported experiments.     

Vibrational Communication in the Cherry Leaf Roller Caterpillar Caloptilia serotinella (Gracillarioidea: Gracillariidae)

The cherry leaf roller (Caloptilia serotinella) produces three distinct types of substrate-borne signals—scraping, plucking, and vibrating—during interactions between conspecifics. Signals were recorded using a piezoelectric sensor, and behavioral experiments tested the hypothesis that signaling functions in territorial disputes over costly leaf shelters. Trials involving the introduction of a conspecific to a resident's leaf shelter demonstrated a significant increase in the amount of scraping by the resident; there was no significant difference in plucking or vibrating. In control trials, general mechanical disturbances such as opening and probing the shelter typically did not elicit signaling. Although both residents and intruders were observed to produce all three signal types, residents most often initiated signaling, and scraped significantly more than intruders. Implications for understanding the diversity of vibrational communication in larval Lepidoptera, particularly shelter-building species, are discussed.     

Determination of self-locompatibility genotypes of Korean apple cultivars based on S-RNase PCR

To prevent self-fertilization, apple has a gametophytic self-incompatibility mechanism, part of a widespread intraspecific system, that is controlled by a multi-allelic locus. This attribute has been exploited in breeding programs for new cultivars. Likewise, many apple orchards depend on artificial pollination. Therefore, molecular analysis and early identification of the self-incompatibility (S) genotype could greatly improve breeding schemes and pollen donors selection. Here, we PCR-amplified the S-RNase PCR fragments from a total of 14 cultivars and parents, using new primers (ASPF3+ASPR3) common to 23 S-alleles in apple. The S-genotypes were determined for the following: ‘Hongro’ (S₁S₃), ‘Gamhong’ (S₁S₉), ‘Saenara’ (S₁S₃), ‘Chukwang’ (S₃S₉), ‘Hwahong’ (S₃S₉), ‘Seokwang’ (S₃S₃), ‘Hwarang’ (S₁S₉), ‘Sunhong’ (S₃S₉), ‘S.E.B.’ (S₁S₁₉), ‘S.G.D.’ (S₂S₃), and ‘Mollie’s Delicious’ (S₃S₇). We also confirmed the characteristics of the S-genotypes for eight Korean apple cultivars by PCR-Southern blot analysis, using seven S-RNases as probes.     

Direct measurement of equilibrium constants for high-affinity hemoglobins

The biological functions of heme proteins are linked to their rate and affinity constants for ligand binding. Kinetic experiments are commonly used to measure equilibrium constants for traditional hemoglobins comprised of pentacoordinate ligand binding sites and simple bimolecular reaction schemes. However, kinetic methods do not always yield reliable equilibrium constants with more complex hemoglobins for which reaction mechanisms are not clearly understood. Furthermore, even where reaction mechanisms are clearly understood, it is very difficult to directly measure equilibrium constants for oxygen and carbon monoxide binding to high-affinity (K(D) < 1 micro M) hemoglobins. This work presents a method for direct measurement of equilibrium constants for high-affinity hemoglobins that utilizes a competition for ligands between the "target" protein and an array of "scavenger" hemoglobins with known affinities. This method is described for oxygen and carbon monoxide binding to two hexacoordinate hemoglobins: rice nonsymbiotic hemoglobin and Synechocystis hemoglobin. Our results demonstrate that although these proteins have different mechanisms for ligand binding, their affinities for oxygen and carbon monoxide are similar. Their large affinity constants for oxygen, 285 and approximately 100 micro M(-1) respectively, indicate that they are not capable of facilitating oxygen transport.     

Discrimination of three Typhlodromalus species (Acari: Phytoseiidae) using random amplified polymorphic DNA markers

We compared the random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) banding patterns obtained from four laboratory cultures representing three phytoseiid mite species (Typhlodromalus limonicus (Garman and McGregor), two cultures of Typhlodromalus manihoti (de Moraes) and Typhlodromalus tenuiscutus (McMurtry and de Moraes). The RAPD-PCR was conducted on the pooled DNA from five adult female mites. For each culture, three samples of five females were analysed with each of eight RAPD-PCR primers. Five of the eight primers could be used individually to distinguish the species. To quantify the within- and between-species variation, genetic distances were calculated based on the proportion of shared scorable bands. The within-species genetic distances (0.072-0.186) were much lower than the between-species genetic distances (0.407-0.656). We believe that this technique could be used effectively to identify other cryptic mite species.     

Toxicity of pesticides to the citrus leafminer and its parasitoid Ageniaspis citricola evaluated to assess their suitability for an IPM program in citrus nurseries

The relative toxicity of pesticides to Phyllocnistis citrella and its parasitoid Ageniaspis citricola was compared by several bioassay methods. A clip-cage bioassay measured survival of adults exposed to fresh residues at 0.25-times (0.25×), 0.5×, 1×, and 2× the lowest recommended rate of each pesticide, a water control (0×), and 24- and 48-h aged residues of oil at 1.5% (1×) rate. A one-species cylinder bioassay determined the effects of pesticides on immature stages of the citrus leafminer after treating young citrus trees with the same rates of pesticides (except for avermectin, tested at 0×, 0.01×, 0.025×, 0.05×, 0.1×, and 0.25× rates). A sublethal rate of petroleum oil (0.4%) was added as an adjuvant in some treatments. The effect of pesticides on immature stages of A. citricola was determined with a two-species cylinder bioassay after treating young citrus trees with the same rates as above. An index of IPM compatibility was developed based on the efficacy of the pesticide as a control agent of the leafminer (or other pests) and its selectivity to the parasitoid at the lowest recommended field rate (0.25× the field rate for avermectin). Azadirachtin (Neemix) + oil, diflubenzuron (Micromite) + oil, fenoxycarb (Eclipse) + oil, and oil alone (FC 435-66) were classified as IPM-compatible insecticides. Sprays of azadirachtin (Align) + oil, neem oil (Neemgard), and drenched imidacloprid (Admire) were ranked as a semi-compatible insecticides. The fungicide copper hydroxide (Kocide 101) and a fish oil-based foliar fertilizer (Zapata HFE) were considered compatible. Avermectin (Agri-Mek) + oil, ethion (Ethion), and imidacloprid (Provado) applied as a spray were IPM-incompatible insecticides. These products should be tested under field conditions to confirm these ratings.