Biology and host preference of Selitrichodes neseri: A potential biological control agent of the Eucalyptus gall wasp,Leptocybe invasa

Selitrichodes neseri (Hymenoptera: Eulophidae) is a parasitoid of the invasive gall-forming wasp Leptocybe invasa (Hymenoptera: Eulophidae), which has caused serious damage to Eucalyptus plantations in many parts of the world. S. neseri is a recently discovered parasitoid considered to be a potentially important biological control agent of L. invasa. The aim of this study was to provide the first basic data on the biology of S. neseri, which is essential for its application in biological control. S. neseri was shown to be a biparental ectoparasitoid. Observation from dissected galls indicated that the parasitoid developed on late larvae, pupae and callow adults, although development did occur in a range of gall ages. Observed nominal parasitism in captivity ranged from 9.7% to 71.8%. Adult S. neseri specimens, fed with honey-water and galled Eucalyptus leaves, survived an average of 26 days at 26 °C. The average developmental time from oviposition to emergence was 19.3 days ± 0.2 days. There was no pre-oviposition period. A single female produced a maximum of thirty-nine offspring, with a maximum of ten per day. Dissection of the ovaries showed that twelve ovarioles were present. The sex ratio of S. neseri observed in this study was 1:3.43 males:females. Galls of native insects most closely related to L. invasa and to galls of similar morphology to L. invasa-induced galls, were not suitable for S. neseri oviposition. S. neseri showed considerable potential as a biological control agent of L. invasa due to its relatively short developmental time, long adult life span when supplemented with carbohydrates, ability to utilize a range of gall ages and the fact that it has a high level of host specificity.     

Mitogenomic analysis of Montipora cactus and Anacropora matthai (cnidaria; scleractinia; acroporidae) indicates an unequal rate of mitochondrial evolution among Acroporidae corals

The complete nucleotide sequence of the mitochondrial (mt) genome was determined for specimens of the coral species Montipora cactus (Bernard 1897) and Anacropora matthai (Pillai 1973), representing two morphologically distinct genera of the family Acroporidae. These sequences were compared with the published mt genome sequence for the confamilial species, Acropora tenuis (Dana 1846). The size of the mt genome was 17,887 bp and 17,888 bp for M. cactus and A. matthai. Gene content and organization was found to be very similar among the three Acroporidae mt genomes with a group I intron occurring in the NADH dehyrogenase 5 (nad5) gene. The intergenic regions were also similar in length among the three corals. The control region located between the small ribosomal RNA (ms) and the cytochrome oxidase 3 (cox3) gene was significantly smaller in M. cactus and A. matthai (both 627 bp) than in A. tenuis (1086 bp). Only one set of repeated sequences was identified at the 3′-end of the control regions in M. cactus and A. matthai. A lack of the abundant repetitive elements which have been reported for A. tenuis, accounts for the relatively short control regions in M. cactus and A. matthai. Pairwise distances and relative rate analyses of 13 protein coding genes, the group I intron and the largest intergenic region, igr3, revealed significant differences in the rate of molecular evolution of the mt genome among the three species, with an extremely slow rate being seen between Montipora and Anacropora. It is concluded that rapid mt genome evolution is taking place in genus Acropora relative to the confamilial genera Montipora and Anacropora although all are within the relatively slow range thought to be typical of Anthozoa.     

Estimating survival of the shortfin mako Isurus oxyrinchus (Rafinesque) in the north-west Atlantic from tag-recapture data

Survival was estimated for shortfin mako Isurus oxyrinchus in the north-west Atlantic from tag-recapture data. The data used in this study were collected by the National Marine Fisheries Service Cooperative Shark Tagging Programme from 1962 to 2003. In total, 6309 shortfin mako sharks were tagged, of which 730 were recaptured. The high recapture rate of 11·6% for this species provided adequate recapture data to carry out survival analyses. Estimates of survival were generated with the computer software MARK, which provided a means for estimating parameters from tagged animals when they were recaptured. The results of several models are presented with various combinations of constant and time-specific survival and recovery rates. A parametric bootstrap and the median variance inflation factor ( ) approach were used to test the fit of the general model to the data. The estimated indicated a very good model fit. The models with time invariant survival rate had the most support from the data and no group or time period effects were found. Recovery rate ( f ) appeared to increase from 0·043 in the early years to 0·056 in the later years. The nominal survival rate of 0·59 year⁻¹ was adjusted with an estimated tag-shedding rate of 0·26 year⁻¹ to generate a final corrected annual survival estimate of 0·79 with a 95% CI of 0·71–0·87.     

Size-scaling of zooplankton foraging in Arctic charr

Prey capture rate (number of prey s⁻¹) and the mode of feeding of Arctic charr Salvelinus alpinus were studied by performing foraging experiments with two sizes (1·1 and 1·8 mm) of Daphnia longispina prey. Arctic charr were particulate feeders at all densities tested. Adjusted for the effect of prey density, the capture rate showed a hump-shaped relationship with Arctic charr size for both sizes of D. longispina . Estimated attack rates ( a ) also tended to show a hump-shaped relationship with fish size. The estimated size-scaling exponent of the attack rate function, however, was relatively small, implying small changes in attack rate over fish sizes. Simultaneous estimations of a and handling time were used in combination with published data on fish metabolism and dry mass rations of prey to estimate maintenance resource density of prey as a function of Arctic charr mass. Maintenance resource densities increased monotonically with Arctic charr size, and rapidly as optimum fish size relative to attack rate on prey was passed.     

EFFECTS OF ARSENATE ON GROWTH OF NITROGEN-AND PHOSPHORUS-LIMITED CHLORELLA VULGARIS (CHLOROPHYCEAE) ISOLATES1

The effects of arsenate on the growth characteristics of five isolates of the freshwater alga, Chlorella vulgaris Beij., were examined. Two field isolates originated from arsenic-contaminated sites in Yukon, Canada and Kyushi, Japan; two reference isolates were obtained from the University of Texas Culture Collection. One isolate was selected for arsenic-tolerance in the laboratory. All five strains survived in culture solutions containing high arsenate concentrations. Arsenate (1–25 mM As) reduced photosynthesis and cell growth, as reflected by induced lag periods, slower growth rates, and lower stationary cell yields. Field isolates had shorter lag periods, higher growth rates, and enhanced cell yields compared to lab isolates when exposed to the same arsenic concentrations. Growth of the phosphorus-limited field strains was stimulated by the addition of arsenic. The cell yield of phosphorus-limited C. vulgaris Yukon, when treated with arsenic, was two times that of the phosphorus-limited control. This pattern was not evident when photosynthesis was used as a measure of cell response.     

Effect of Temperature on the Formation of Microsclerotia of Verticillium dahliae

Microsclerotium formation by six isolates of Verticillium dahliae was studied at different temperatures both in vitro and in Arabidopsis thaliana . In vitro mycelial growth was optimal at 25°C, but microsclerotium formation was greatest at 20°C (two isolates) or 15–20°C (one isolate). Seedlings of A. thaliana were root-dipped in a conidial suspension, planted, and either placed at 5, 10, 15, or 25°C, or left at 20°C until the onset of senescence, after which some of the plants were placed at 5, 10, 15, or 25°C. The amount of microsclerotia per unit of shoot weight was assessed in relation to isolate and temperature. The optimal temperature for production of microsclerotia was 15–25°C. Two isolates each produced about 10 times more microsclerotia than each of the other four isolates. For these isolates, high R ²_adj.-values of 0.77 and 0.66 were obtained, with temperature and its square as highly significant (P   < 0.001) independent variables. R ²_adj.-values for the other isolates varied between 0.28 and 0.39. Moving plants to different temperatures at the onset of senescence led to microsclerotial densities that were intermediate between densities on plants that had grown at constantly 20°C and plants grown at other temperatures. This suggests that vascular colonization rate and rate of microsclerotium formation are similarly affected by temperature. The senescence rate of plants appeared unimportant except for plants grown at 25°C, which showed the highest amounts of microsclerotia per unit of plant weight in the most rapidly senescing plants.     

Rheological properties of guar gum and hydroxyethyl guar gum in aqueous solution

The rheological properties of aqueous solutions of guar gum (GG) and hydroxyethyl guar gum (HEG) have been investigated. The flow properties of these polysaccharide solutions were studied at the shear rate in the range 1.5–1310s⁻¹ using a Rheotest-2 viscometer. The flow of these polysaccharide solutions was described by equation of state based on Cross model. The basic rheological parameters, like zero shear rate viscosity (η_o), elasticity modulus (G_o) and relaxation time (gl_o) were calculated using simple and established relations. Master viscosity curves indicated that the molecular weight distribution of native guar gum has been changed by hydroxyethylation under specified reaction conditions. The effect of concentration and temperature on η_o and λ_o has been studied, and the relations among these were established by simple equations.     

Participation of capsaicin-sensitive neurons in the cardiovascular effects of neurotensin in guinea pigs

Intravenous (IV) infusions of neurotensin (NT) in anesthetized guinea pigs elicited dose-dependent pressor effects and tachycardia. Both effects were significantly reduced or abolished in guinea pigs given a chronic treatment with the neurotoxin capsaicin. In guinea pig isolated atria NT evoked a positive inotropic and chronotropic effect. Both effects were completely abolished in atria derived from capsaicin-treated guinea pigs. The positive inotropic and chronotropic effects of NT in guinea pig atria were mimicked by capsaicin and calcitonin gene-related peptide (CGRP). These results were interpreted as an indication that NT produces its cardiovascular effects in guinea pigs by activating capsaicin-sensitive sensory neurons.