CORRESPONDENCE BETWEEN PHYLOGENY AND MORPHOLOGY OF SNOWELLA SPP. AND WORONICHINIA NAEGELIANA,CYANOBACTERIA COMMONLY OCCURRING IN LAKES1

In this study, the first reported isolates of the genera Snowella and Woronichinia were characterized by 16S rRNA gene sequencing and morphological analysis. Phylogenetic studies and sequences for these genera were not available previously. By botanical criteria, the five isolated strains were identified as Snowella litoralis (Häyrén) Komárek et Hindák Snowella rosea (Snow) Elenkin and Woronichinia naegeliana (Unger) Elenkin. This study underlines the identification of freshly isolated cultures, since the Snowella strains lost the colony structure and were not identifiable after extended laboratory cultivation. In the 16S rRNA gene analysis, the Snowella strains formed a monophyletic cluster, which was most closely related to the Woronichinia strain. Thus, our results show that the morphology of the genera Snowella and Woronichinia was in congruence with their phylogeny, and their phylogeny seems to support the traditional botanical classification of these genera. Furthermore, the genera Snowella and Woronichinia occurred commonly and might occasionally be the most abundant cyanobacterial taxa in mainly oligotrophic and mesotrophic Finnish lakes. Woronichinia occurred frequently and also formed blooms in eutrophic Czech reservoirs.     

Reaction mechanism of surfactant‐sensitized chemiluminescence of bis(2,4,6‐trichlorophyenyl) oxalate and hydrogen peroxide induced by gold nanoparticles

The chemiluminescence (CL) of bis(2,4,6‐trichlorophyenyl) oxalate with hydrogen peroxide in the present of cationic surfactant and gold nanoparticles was studied. The CL emission was obviously enhanced in the presence of surfactant at a suitable concentration, with a synergetic catalysis effect exhibited. Different sizes of gold nanoparticles (15 and 50 nm) showed different effects on CL intensity. Mechanisms of the CL reaction and sensitization effect are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Scale-dependent interactions between intrinsic and extrinsic processes reduce variability in protist populations

Interactions between intrinsic processes and extrinsic fluctuations can positively impact population persistence in ways often not predicted by classic ecological models. These interactions only arise when the intrinsic and extrinsic processes operate on the proper relative scales in time or space. Both metapopulation theory and resonance/attenuation theory suggest that interactions which lower population variability will occur when the intrinsic and extrinsic process occur on similar time scales. I performed an aquatic protist microcosm experiment to investigate how the relative frequencies of extrinsic density perturbations and intrinsic resource pulses impacted population variability. Population variability was lowest in the treatments of intermediate frequency, in which the extrinsic fluctuations and intrinsic processes were on the same time scale. This result is consistent with general theoretical predictions, and empirically documents the importance of considering scale in interactions between intrinsic and extrinsic processes that positively impact population persistence.     

Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.     

Calcium-Dependent Release of Tyrosine in Brain Elicited by Stimulation of Neuropeptide Receptors

We sought to establish whether the endogenous opiate-receptor agonist Met-enkephalin (m-ENK) selectively modulates the release of endogenous tyrosine (Tyr) from brain slices prepared from the corpus striatum (CS). Amino acids (AAs) released from slices of CS and, for comparison, cerebral cortex (Cx) were measured by HPLC. Incubation of slices with m-ENK (1-10 microM) increased the basal release of Tyr (up to 293% of control) from CS, but not Cx, whereas other nonneurotransmitter AAs, phenylalanine (Phe) and valine (Val), were unchanged. The release of the putative neurotransmitter AAs glutamate (Glu), taurine (Tau), and glycine (Gly) were similarly increased by 50-150% with m-ENK in slices of CS, but not Cx. The enhanced release of AAs by m-ENK was prevented by removal of extracellular Ca2+ or by preincubation with the opiate receptor antagonist naloxone. Neuronal depolarization by potassium (5-55 mM) in the presence of Ca2+ did not affect the release of Tyr, whereas release of neurotransmitter AAs such as gamma-aminobutyric acid (GABA) were markedly increased. The increase in basal Tyr release by m-ENK was not the result of a decreased uptake of Tyr. Relative to slices, the basal release of Tyr, Phe, and Val from a synaptosomal (P2) preparation of CS was small (8-51%) compared to that of GABA, Gly, Glu, and Tau (49-123%). Nonetheless, m-ENK (10 microM) markedly increased the release of Tyr (to 833%), but not Glu, Gly, and Tau from the P2 fraction.(ABSTRACT TRUNCATED AT 250 WORDS)