Population density ofMonochamus alternatus adults (Coleoptera: Cerambycidae) and incidence of pine wilt disease caused byBursaphelenchus xylophilus (Nematoda: Aphelenchoididae)

Summary The seasonal occurrence ofMonochamus alternatus and newly weakened trees were investigated in aPinus thunbergii stand for 4 years. Adult beetles were present between June and September with a peak in their population occurring in early July followed by a decline then a period of about one month being in a steady number. The average number ofBursaphelenchus xylophilus (Nematoda), which is the causal agent of pine wilt disease, within beetles decreased as the season advanced. Pine trees newly weakened byB. xylophilus appeared between June and October, especially from August to October. The proportion of weakened or killed trees was directly proportional to the average beetle density per tree from June to August.     

Temporal and spatial relationships between an herbivorous lady beetleEpilachna niponica and its predator,the earwigAnechura harmandi

The relationships between egg predation of an herbivorous lady beetle Epilachna niponica (Lewis ) and its predator, the earwig Anechura harmandi (Burr ), were examined in both time and space. In spite of little annual, changes in egg densities, egg mortality due to predation varied considerably. There was no, clear relationship between the earwig density and the proportionate predation over the five years. The seasonal occurrence of earwig nymphs on thistle plants, however, was closely synchronized with that of egg predation. Predator attacks on the beetle occurred in a time-restricted manner. Thus, later cohorts mostly escape from heavy predatory pressure. No spatially density-depent egg predation was detected at the level of either thistle plants or thistle patches. Furthermore, there was no indication of aggregative behaviour of the earwig in response to local egg density. The earwig density was more likely to be associated with particular localities with sandy deposits available for its nest site.     

Isolation and Characterization of Mustard (Sinapis alba L.) Seed Storage Proteins

A total storage protein fraction was prepared from mustard (Sinapis alba L.) seeds via isolated protein bodies and characterized by sedimentation, immunological, and electrophoretic techniques. Mustard seed storage protein consists of three fractions (1) a “legumin-like” 13-S complex composed of two pairs of disulfide-linked polypeptides (16.5 + 28.5 kDa and 19.5 + 34 kDa, respectively) and two single polypeptides (18 kDa and 26 kDa), (2) a “vicilin-like” 9-S complex composed of two glycoproteins (64 kDa and 77 kDa), and (3) two small polypeptides (10 kDa and 11 kDa) which probably represent the 1.7-S complex found in other Cruciferae. In contrast to related species, no glycosylated polypeptide was found in the 13-S complex. Immunological relationships were found between the paired polypeptides of the 13-S complex but not between polypeptides of the 13-S complex and polypeptides of the 9-S complex. Pulse-chase labeling and in vitro translation of polysomal RNA from young embryos demonstrated that the polypeptides of the 13-S complex originate from high molecular mass precursors, except for the 18 kDa polypeptide which appears to be synthesized in its final size. The amino-acid composition of the major polypeptides of the mustard storage protein is given.     

Purification and characterization of antifreeze proteins from larvae of the beetle Dendroides canadensis

Summary Four antifreeze proteins (AFPs) were purified from larvae of the beetle Dendroides canadensis. The AFPs are similar in amino acid compositions, having high contents of hydrophilic amino acids (45–55 mol%) and cysteine (16 mol% Cys). Approximately half of the Cys residues form disulfide bridges, and both the disulfide bridges and free sulfhydryls are essential for activity. The N-terminals of the AFPs are blocked. The pH optimum of the AFPs is 7.8, but major loss of activity occurred only at very high pH (12.0). The detergents SDS and Triton X-100 did not inactivate the AFPs. Circular dichroism spectra indicate the presence of both and secondary structures in the AFPs, in addition to a large random structure component.Abbreviations AFP antifreeze protein - CD circular dichroism - DTT dithiothreitol - HPLC high pressure liquid chromatography - PAGE polyacrylamide gel electrophoresis - PAS periodic acid Schiff - SDS sodium dodecyl sulfate - TFA trifluoroacetic acid     

Contagious egg-distribution on host pods and avoidance of pods received eggs in a wild bruchidKytorhinus sharpianus

The present study investigated the way a wild bruchid, Kytorhinus sharpianus, distributes its eggs on host pods. First, we counted the number of eggs per pod on the host plant (Sophola flavescens) in the field. The egg-distributions by the overwintered-generation adults in July and by the second-generation adults in mid October did not deviate from Poisson distribution because of small numbers of eggs laid. However, the egg-distribution in late August when many first-generation adults emerged was significantly contagious. The deposition of eggs was determined for three types of pods: (A) clean pods, (B) pods with eggs, and (C) those which eggs had been laid on but were removed from later. The numbers of eggs laid newly on three types of pods were significantly different; A>C>B, suggesting that an oviposition marker pheromone (O.M.P.) caused females to avoid pods on which eggs were deposited. Egg-shells reinforced that response. Monte Carlo simulations for the egg-distribution on pods predicted that even if females avoid pods with heavy egg-load through O.M.P., the egg-distribution becomes contagious when there is a large heterogeneity in quality of the pods.     

Flight metabolism in the African fruit beetle,Pachnoda sinuata

Metabolite concentrations in flight muscles and in abdomen of beetles (Pachnoda sinuata) were measured after various periods of tethered flight and subsequent rest. Three distinct phases of energy metabolism are found in active flight muscles: (1) during the first minutes of flight proline is used as main substrate and concomitantly alanine accumulated as an end product; (2) the second phase is characterized by a large-scale degradation of glycogen; (3) after about 8 min of flight the metabolite levels stabilize, while flight performance appears unchanged. After the termination of flight the preflight proline concentration (70 mol·g^-1 fw) is re-established in less than 60 min, whereas restoration of resting levels of other metabolites requires longer. The pattern of maximal enzyme activities and the respiratory rates of mitochondria with different substrates confirm the significance of proline and carbohydrates as the main fuels of working flight muscles.Abbreviations CS citrate synthetase - Cytox cytochrome c oxidase - EDTA ethylenediaminetetra-acetate - fw fresh weight - GluDH glutamate dehydrogenase - GPT alanine aminotransferase - HOAD hydroxyacyl-coenzyme A dehydrogenase - HPLC high pressure liquid chromatography - ME malic enzyme - PCA perchloric acid - RQ repiratory quotient - TRA triethanolamine     

Na+-dependent medium-affinity uptake of L-glutamate in the insect epidermis

It is proposed that the activity of an epidermal cotransport system for Na⁺ and dicarboxylic amino acids accounts for the small amounts of L-glutamate and L-aspartate in the otherwise amino-acid-rich blood plasma of insects. This Na⁺-dependent transport system is responsible for more than 95% of the uptake of these amino acids into the larval epidermis of the beetle Tenebrio molitor. Kinetic analysis of uptake showed that the Na⁺-dependent co-transporter has medium affinity for L-glutamate and L-aspartate. The K _m for L-glutamate uptake was 146 mol·l^-1, and the maximum velocity of uptake (V _max) was 12.1 pmol·mm^-2 of epidermal sheet per minute. The corresponding values for L-aspartate were 191 mol·l^-1 and 8.4 pmol·mm^-2·min^-1. The Na⁺/L-glutamate co-transporter has a stoichiometry of at least two Na⁺ ions for each L-glutamate-ion transported (n=217). The co-transporter has an affinity for Na⁺ equivalent to a K _m of 21 mmol · l^-1 Na⁺. Na⁺ is the only external ion apparently required to drive L-glutamate uptake. Li⁺ substitutes weakly for Na⁺. Removal of external K⁺ or addition of ouabain decreases uptake slowly over 1 h, suggesting that these treatments dissipate the Na⁺/K⁺ gradient by inhibiting epidermal Na⁺/K⁺ ATPase. Several structural analogues of L-glutamate inhibit the medium-affinity uptake of L-glutamate. The order of potency with which these competitive inhibitors block glutamate uptake is L-cysteatethreo-3-hydroxy-Dl-aspartate > D-aspartateL-aspartate> L-cysteine sulphinate > L-homocysteateD-glutamate. L-trans-Pyrrolidine-2,4-dicarboxylate, a potent inhibitor of L-glutamate uptake in mammalian synaptosomes, is a relatively weak blocker of epidermal uptake. The epidermis takes up substantially more L-glutamate by this Na⁺-dependent system than tissues such as skeletal muscle and ventral nerve cord. The epidermis may be a main site regulating blood L-glutamate levels in insects with high blood [Na⁺]. Because L-glutamate and L-aspartate stimulate skeletal muscle in insects, a likely role for epidermal L-glutamate/L-aspartate transporter is to keep the level of these excitatory amino acids in the blood below the postsynaptic activation thresholds.Abbreviation ac acetate - Ch choline - CNS central nervous system - cpm counts per minute - CDTA trans-1,2-diaminocyclohexane-N,N,N,N-tetraacetic acids - HPLC high performance liquid chromatography - K _m Michaelis constant - n _app apparent number - NMG N-methyl-D-glucamine - Pipes Piperazine-N,N-bis-[2-ethanesulfonic acid] - SD standard deviation - TEA tetraethyl-ammonium - V velocity of uptake - V _max maximum velocity of uptake     

Macro nutrient cation uptake by plants

Summary In pot experiments with barley, mustard, leek, lettuce and spinach, and in a field experiment with 30 cultivars of barley uptakes of K, Mg, Ca, Na and N were studied at varying concentrations and activities of these cations in the soil solution.The sum of macro cations (K, Mg, Ca, Na) in meq per 100 g aerial plant parts were independent of the chemical composition of the soil solution, but dependent on plant species and on the N concentration in the plant.The ratios of mean net inflows of Mg, Ca and K into plants and corresponding cation activity ratios (a_Mg/a_Ca and ) in the soil solution were linearly related and highly correlated under conditions in which growth rate and/or rate of incorporation into new tissues constituted the rate determining step of cation uptake. Consequently, mean net inflows of K, Mg and Ca were independent of ion concentration and ion activity of K, Mg or Ca in the soil solution under the conditions of constant activity ratio.The results agree with the concept that plants have a finite cation uptake capacity, and that plants are in a equilibrium-like state with the activities of K, Mg, and Ca ions in the soil solution. The results indicate that both ratios and content of exchangeable cations should be considered in our evaluation of soil test data.     

Density-related mortality of the flour beetle,Tribolium confusum duval

Life tables were constructed to assess the relative importance of some factors causing mortality of Tribolium confusum and to gauge their response to increasing population density. Observations focussed on three population densities (100, 400 and 800 individual/8 g medium) from the egg to the adult stage. The medium was not renewed in order to maximize predatory interactions. Generation mortality at densities 100, 400 and 800 was 42%, 50% and 74% respectively, i. e. density-dependent. Mortality in the first 10 days was also density-dependent reaching a maximum of 27% at density 800: predation by small larvae on eggs seemed the principal causative factor. The overall pattern of larval mortality was density-independent. Data on the mortality of pupae and callows were ultimately consistent with an inversely density-dependent pattern. Apparently, only mortality occurring within the first 10 days was capable of population regulation.