Larval food affects oviposition preference,female fecundity and offspring survival in Yponomeuta evonymellus

1. Yponomeuta evonymellus is a monophagous moth that feeds on Prunus padus which is native to Europe. In recent years, larval feeding and egg clusters have also been observed on non‐native Prunus serotina plants; however, survival of larvae on this new host is very low. 2. The objective of the present study was to determine how the feeding of larvae on each of the two host plants impacts oviposition, offspring survival and fecundity in Y. evonymellus. Our hypothesis was that, under controlled conditions, females will lay eggs on the host on which they fed as larvae. We also hypothesised that the lower survival of young larvae feeding on P. serotina was due to the smaller buds and leaves present in this species, relative to those of P. padus. 3. A dual‐choice experiment conducted under laboratory conditions demonstrated that females preferentially chose to oviposit on the plant species on which they fed as larvae. In the experiment, potential fecundity and offspring survival were significantly higher on P. padus than on P. serotina. The reduced performance of Y. evonymellus on P. serotina was correlated with a smaller bud mass and volume, lower leaf mass and surface area, and difficulty in constructing a protective tent against unfavourable weather conditions. 4. In summary, the identity of the host plant species during larval feeding determines adult oviposition preference for that host species. The survival of larvae on P. serotina growing in the nature is low, but for phenology‐related reasons.     

EFFECT OF SUBLETHAL DOSES OF CADMIUM, INORGANIC MERCURY AND METHYLMERCURY ON THE CELL MORPHOLOGY OF AN INSECT CELL LINE (AEDES ALBOPICTUS, C6/36)

The effect of CdCl₂(44 μ ), HgCl₂(3.7 μ ), and MeHgCl (2 μ ) on the morphology ofAedes albopictusC6/36 cells was studied at the light microscopical level. Treatment times and metal concentrations were in the sublethal range as determined by a fluorometric dye exclusion test. The three metal species had profound effects on the cell morphology. MeHgCl treatment induced the development of a large number of short, actin-supported, tangled filopodia. Both CdCl₂and HgCl₂induced long extensions. Pretreatment with colchicine but not with cyto-chalasin B prevented formation of these extensions which suggests that they were supported by microtubules. This was confirmed by immunostaining for microtubules. The extensions were relatively stable towards colchicine post-treatment. To authors’ knowledge, this effect has not yet been described for heavy metals. The similarity with 20-hydroxyecdysone-treated cells and the occurrence of cytoplasmic feet in insect cells is discussed.     

Exogenously applied sulphate as a tool to investigate transport and reduction of chromate in the duckweed Spirodela polyrhiza

The accumulation of chromium in Spirodela polyrhiza was investigated in the presence and absence of exogenously applied sulphate. Precultivation (10 d) at minimum sulphate concentration (0.013 m m versus 1 m m in controls) enhanced the rate of chromium accumulation. This effect was caused by the increased number of sulphate transporters which transport chromate into cells. Chromate and sulphate compete for the available sulphate transporters. The kinetics of reduction Cr(VI)→Cr(V) was investigated by l -band electron paramagnetic resonance (EPR) spectroscopy. The kinetic model developed previously (Appenroth et al., Journal of Inorganic Biochemistry 78, 235–242, 2000) was refined and extended to include chromate transport and reduction in the presence of competing ions. The following conclusions were drawn from the fitting procedure: without simultaneously applied sulphate, the rate constant of Cr(VI) transport from apoplast into plant cells and the rate constant of Cr(VI) to Cr(V) reduction within the apoplast are comparable (7.0 versus 5.7 h⁻¹) demonstrating that these two processes are competing. Moreover, the rate constant of reduction Cr(V)→Cr(III) is much lower within cells than in apoplast (0.39 versus 7.0 h⁻¹) showing that Cr(V) is stabilized in the symplast. The rate of transport of Cr(VI) into plant cells is at least one order of magnitude higher than that of Cr(V) or Cr(III). The treatment with sulphate (10 m m ) decreases the rate constant of the transport of Cr(VI) into cells (2.0 h⁻¹) confirming the competition of chromate and sulphate for the same transporters. Simultaneously, the rate constant of Cr(V)→Cr(III) reduction is increased in the apoplast (by the factor of 3) and decreased in the symplast (by the factor of 5). Treatment with higher sulphate concentrations (100 m m ) increases the accumulation of chromium by enhancing the rate constant of Cr(VI) transport into cells leaving other processes essentially unchanged. We suggest that 100 m m sulphate opens a new pathway for chromate transport into cells.     

Paramecium Has Two Regulatory Subunits of Cyclic AMP-Dependent Protein Kinase, One Unique to Cilia

ABSTRACT. The subunit composition and intracellular location of the two forms of cAMP-dependent protein kinase of Paramecium cilia were determined using antibodies against the 40-kDa catalytic (C) and 44-kDa regulatory (R₄₄) subunits of the 70-kDa cAMP-dependent protein kinase purified from deciliated cell bodies. Both C and R₄₄ were present in soluble and particulate fractions of cilia and deciliated cells. Crude cilia and a soluble ciliary extract contained a 48-kDa protein (R₄₈) weakly recognized by one of several monoclonal antibodies against R₄₄, but not recognized by an anti-R₄₄ polyclonal serum. Gel-filtration chromatography of a soluble ciliary extract resolved a 220-kDa form containing C and R₄₈ and a 70-kDa form containing C and R₄₄. In the large enzyme, R₄₈ was the only protein to be autophosphorylated under conditions that allow autophosphorylation of R₄₄ The subunits of the large enzyme subsequently were purified to homogeneity by cAMP-agarose chromatography. Both C and R₄₈ were retained by the column and eluted with 1 M NaCl; no other proteins were purified in this step. These results confirm that the ciliary cAMP-dependent protein kinases have indistinguishable C subunits, but different R subunits. The small ciliary enzyme, like the cell-body enzyme, contains R₄₄, whereas R₄₈ is the R subunit of the large enzyme.