Dispersal and dormancy strategies among insect species competing for a pulsed resource

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Cross-Modal Stimulus Conflict: The Behavioral Effects of Stimulus Input Timing in a Visual-Auditory Stroop Task

Cross-modal processing depends strongly on the compatibility between different sensory inputs, the relative timing of their arrival to brain processing components, and on how attention is allocated. In this behavioral study, we employed a cross-modal audio-visual Stroop task in which we manipulated the within-trial stimulus-onset-asynchronies (SOAs) of the stimulus-component inputs, the grouping of the SOAs (blocked vs. random), the attended modality (auditory or visual), and the congruency of the Stroop color-word stimuli (congruent, incongruent, neutral) to assess how these factors interact within a multisensory context. One main result was that visual distractors produced larger incongruency effects on auditory targets than vice versa. Moreover, as revealed by both overall shorter response times (RTs) and relative shifts in the psychometric incongruency-effect functions, visual-information processing was faster and produced stronger and longer-lasting incongruency effects than did auditory. When attending to either modality, stimulus incongruency from the other modality interacted with SOA, yielding larger effects when the irrelevant distractor occurred prior to the attended target, but no interaction with SOA grouping. Finally, relative to neutral-stimuli, and across the wide range of the SOAs employed, congruency led to substantially more behavioral facilitation than did incongruency to interference, in contrast to findings that within-modality stimulus-compatibility effects tend to be more evenly split between facilitation and interference. In sum, the present findings reveal several key characteristics of how we process the stimulus compatibility of cross-modal sensory inputs, reflecting stimulus processing patterns that are critical for successfully navigating our complex multisensory world.     

Cold‐induced expression of diapause in Praon volucre: fitness cost and morpho‐physiological characterization

Cold exposure (2°C for 7 days) in constant darkness at mummy stage induces diapause expression in 9% of the Praon volucre Haliday population. Diapausing parasitoids show a significant delay in emergence time compared with nondiapausing counterparts. A diapause‐mediated polyphenism is observed in mummy colour, with diapausing mummies being clearly darker than nondiapausing ones. The diapause status of dark mummies is confirmed by a significant reduction in metabolic rate. Diapausing parasitoids also display specific morphological characteristics: they are heavier (fresh and dry mass) and accumulate larger fat reserves than nondiapausing counterparts. The diapause status is associated with a fitness cost in terms of adult longevity. There is no evidence of diapause‐related change in supercooling ability.     

One hundred years of instability in ensiferan relationships

Although Ensifera is a major insect model group, its phylogenetic relationships have been understudied so far. Few phylogenetic hypotheses have been proposed, either with morphological or molecular data. The largest dataset ever used for phylogeny reconstruction on this group is molecular (16S rRNA, 18S rRNA and 28S rRNA sequences for 51 ensiferan species), which has been used twice with different resultant topologies. However, only one of these hypotheses has been adopted commonly as a reference classification. Here we re‐analyse this molecular dataset with different methods and parameters to test the robustness and the stability of the adopted phylogeny. Our study reveals the instability of phylogenetic relationships derived from this dataset, especially for the deepest nodes of the group, and suggests some guidelines for future studies. The comparison between the different classifications proposed in the past 70 years for Ensifera and our results allows the identification of potential monophyletic clades (katydids, mole crickets, scaly crickets + Malgasia, true crickets, leaf roller crickets, cave crickets) and the remaining unresolved clades (wetas, Jerusalem crickets and most of the highest rank clades) in Ensifera phylogeny.     

Zebrafish serotonin-N-acetyltransferase-2 gene regulation: pineal-restrictive downstream module contains a functional E-box and three photoreceptor conserved elements

Pineal function is defined by a set of very narrowly expressed genes that encode proteins required for photoperiodic transduction and rhythmic melatonin secretion. One of these proteins is serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT), which controls the daily rhythm in melatonin production. Here, pineal-specific expression of the zebrafish aanat-2 (zfaanat-2) was studied using in vivo transient expression analyses of promoter-reporter constructs; this revealed that specificity is determined by two regions located 12 kb away from each other. One is the 5'-flanking region, and the other is a 257-bp sequence, located 6 kb downstream of the transcribed region. This 3'-sequence, designated pineal-restrictive downstream module (PRDM), has a dual function: enhancement of pineal expression and inhibition of extrapineal expression. The former is an autonomic property of PRDM whereas the later function requires interaction with the upstream regulatory region of zfaanat-2. Functional analyses of the PRDM sequence revealed that three photoreceptor conserved elements (TAATC) and a single perfect E-box (CACGTG) are crucial for the dual function of PRDM. These results indicate that pineal specificity of zfaanat-2 is determined by the dual functionality of the PRDM and the interaction between upstream regulatory region and downstream photoreceptor conserved elements and E-box element.     

Speciation and the establishment of zonation in an intertidal barnacle: specific settlement vs. selection

The tropical barnacle Tetraclita forms a belt on hard substrates in the intertidal zone of the Red Sea. Based on morphological data, three distinct species were suggested to exist, occupying different vertical levels - T. barnesorum, T. rufotincta and T. achituvi. In this study we used molecular (12S mitochondrial ribosomal DNA) and ecological data to examine whether this morphological variability reflects genetic differences, or is a result of environmental factors. Adults and spats, collected from settlement plates, were censused and screened genotypically using single strand conformation polymorphism (SSCP) analysis, and settlement dynamics was recorded. We provide evidence for the existence of only two distinct species, and point out both phenotypic plasticity and convergence within and between the proposed species. Cyprids of T. achituvi settle specifically at the lower part of the Tetraclita belt, and feature one phenotype. In contrast, T. rufotincta, occupying the upper and middle portions of the Tetraclita belt, settles throughout the range, shows phenotypic plasticity (three variants), and presumably undergoes selection at the lower part. Thus, the vertical zonation of Tetraclita is produced by the combination of pre-settlement and post-settlement factors, in T. achituvi and T. rufotincta, respectively. The examined system may offer a model in which to study the mechanisms underlying sympatric speciation.     

Three-color versus four-color multiparameter cell cycle analyses of primary acute myeloid leukemia samples

Checkpoint alterations that impact cell cycle and apoptosis responses to therapeutic treatments may produce drug resistance in acute myeloid leukemia (AML). To study these, we have developed flow cytometry assays of checkpoint function that also allow quantitation of key molecular regulators of apoptosis and cell cycle. We have used three-color (3C) assays, with FITC-labeled anti-BCL-2 and PE-labeled anti-proliferating cell nuclear antigen (PCNA) antibodies, and the DNA dye 7-aminoactinomycin, to characterize primary leukemia cells identified in DNA x side light scatter (SSC) histograms. We showed that 3C assays are accurate and reproducible in analyses of leukemia cell lines and of primary AML and normal bone marrow samples (Banker et al.: Blood 89: 243-255, 1997; Banker et al.: Leukemia Res 22: 221-239, 1998; Banker et al.: Clin Cancer Res 4: 3051-3062, 1998). To further confirm the validity of our SSC leukemia cell gating and to address whether immunophenotypic AML subsets might have different biologic properties, we have now designed four-color (4C) flow assays to characterize checkpoint status in leukemic blasts specifically identified by surface immunostaining. In modeling this assay strategy, PE/Cy5-labeled anti-CD34 antibody was used to detect blasts, with FITC-labeled anti-BCL-2, PE-labeled anti-PCNA antibodies, and Hoechst 33342 (H33342) DNA dye. Four-color CD34-gated data was concordant with 3C, SSC-gated data for leukemia cell lines and for most primary AML samples with high and intermediate blast counts. BCL-2 and PCNA immunopositivity and sub-G1 apoptosis determinations were different in the CD34-gated versus SSC-gated blasts in particular samples with smaller CD34(+) subsets, suggesting that leukemia samples can contain blast subsets with different biologic properties. On the other hand, PCNA-gated cell-cycle distributions in untreated cells and G1 versus S phase cell-cycle arrests after cytosine arabinoside treatments were completely concordant in 4C and 3C assays. We conclude that both 3C and 4C assays can be used to characterize protein expression and cell-cycle drug response patterns in leukemia blasts, but that 4C assays may additionally allow discrimination of these properties in immunophenotypic leukemia subsets.