Frequency as a releaser in the courtship song of two crickets,Gryllus bimaculatus (de Geer) and Teleogryllus oceanicus: a neuroethological analysis

1. The courtship behavior of male field crickets, Gryllus bimaculatus (De Geer) and Teleogryllus oceanicus, is a complex, multimodal behavioral act that involves acoustic signals (a courtship song; Fig. 1A,B). The dominant frequency is 4.5 kHz for T. oceanicus song (Fig. 1A) and 13.5 kHz for G. bimaculatus (Fig. IB).
2. When courting males are deprived of their courtship song by wing amputation, their courtship success declines markedly but is restored when courting is accompanied by tape-recordings of their courtship songs or a synthetic courtship song with only the dominant frequency of the natural song; other naturally occurring frequency components are ineffective for restoring mating success (Figs. 4, 5).
3. It has been suggested that an identified auditory interneuron, AN2, plays a critical role in courtship success. Chronic recordings of AN2 in an intact, tethered female show that AN2's response to the natural courtship song and synthesized songs at 4.5 and 13.5 kHz is similar in T. oceanicus. By contrast, in G. bimaculatus, AN2's response to the natural courtship song and synthesized song at 13.5 kHz, but not at 4.5 kHz, is similar (Figs. 2,3).
4. In behavioral experiments, playback of a 30 kHz synthetic courtship song in G. bimaculatus does not restore courtship success, yet this same stimulus elicits as strong a response from AN2 as does the normal courtship song (Fig. 6). Thus, contrary to earlier work by others, we conclude AN2 is not, by itself, a critical neural link in the courtship behavior of these two species of crickets.

     

Bromodeoxyuridine/DNA analysis of replication in CHO cells after exposure to UV light

The effects of ultraviolet light on cellular DNA replication were evaluated in an asynchronous Chinese hamster ovary cell population. BrdUrd incorporation was measured asa function of cell-cycle position, using an antibody against bromodeoxyuridine (BrdUrd) and dual parameter flow cytometric analysis. After exposure to UV light, there was an immediate reduction ( 50%) of BrdUrd incorporation in S phase cells, with most of the cells of the population being affected to a similar degree. At 5 h after UV, a population of cells with increased BrdUrd appeared as cells that were in G1 phase at the time of irradiation entered S phase with apparently increased rates of DNA synthesis. For 8 h after UV exposure, incorporation of BrdUrd by the original S phase cells remained constant, whereas a significant portion of original G1 cells possessed rates of BrdUrd incorporation surpassing even those of control cells. Maturation rates of DNA synthesized immediately before or after exposure by alkaline elution, were similar. Therefore, DNA synthesis measured in the short pulse by anti-BrdUrd fluorescence after exposure to UV light was representative of genomic replication. Anti-BrdUrd measurements after DNA damage provide quantitative and qualitative information of cellular rates of DNA synthesis especially in instances where perturbation of cell-cycle progression is a dominant feature of the damage. In this study, striking differences of subsequent DNA synthesis rates between cells in G1 or S phase at the time of exposure were revealed.     

Heterochromatinization,chromatin elimination and haploidization in the parahaploid mite Metaseiulus occidentalis (Nesbitt) (Acarina: Phytoseiidae)

Embryogenic mitoses, mitoses in females and spermatogenesis are described in the predatory mite Metaseiulus occidentalis (Nesbitt). At 22° C, egg development lasts approximately 4 days. Six chromosomes are seen in mitotic metaphases and anaphases of 0–24 h eggs. Toward the end of this period some embryo squashes have patches of cells containing nuclei which are partially heteropycnotic. These patches of cells apparently increase in size with the age of the embryo. In approximately 1/2 of all 24–48 h-old eggs they encompass all or most cells of the embryo. In these embryos metaphases involved 6 chromosomes, anaphases 3. Either prior to, or following metaphase, a pairing of chromosomes appeared to take place to form 3 units which resembled meiotic diplotene chromosomes where there is opening out between homologues. At metaphase, two sets of 3 chromosomes were slightly differentially stained. One, designated the H set, was darker and slightly more contracted than the other, the E set. At anaphase, 3H and 3E chromosomes segregated in a reductional division retaining the differential contraction until telophase. No cytokinesis appeared. The H set appeared to remain contracted while the E set decontracted to assume the appearance of an interphase nucleus. Both of these entities, side-by-side, created the partially heteropycnotic nucleus mentioned above. The H set then appeared to be excluded from the cell. Mitotic meta and anaphases involving 6 chromosomes were noted in female deutonymphs. Spermatogenesis appeared to encompass an equational division of 3 chromosomes, with the formation of a binucleate spermatid. Two tail structures appeared juxtaposed at the edge of each spermatid and thereafter a separation into two individual sperms occurred. —While mitosis was not studied in known males, we believe that the embryos exhibiting heterochromatinization and elimination of chromosomes in most or all cells were in fact demonstrating parahaploidization.This paper is dedicated to the memory of Professor S.W. Brown and is presented to Professor H. Bauer in honor of his 75th birthday     

Response of cabbage head weight to simulated Lepidoptera defoliation

Studies were conducted to determine the effects of continuous constant amounts of artificial defoliation through the preheading and heading growth stages on head weight of cabbage. High levels of continuous artificial defoliation caused a reduction in head weight in all three years of the study, but the highest yield was always attained at some low level of preheading or heading defoliation. These results demonstrate that cabbage is tolerant to some levels of continuous defoliation before and after head formation. Results from this study are incorporated into a cost-benefit analysis to estimate an economic threshold.

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Résumé L'étude a porté sur le poids des pommes de choux (Brassica oleracea) soumis à différentes intensités de défoliations répétées avant et pendant la formation des pommes. Pendant les trois années de l'étude, huit intensités de défoliation continue ont réduit le poids des pommes, mais le poids le plus élevé a toujours été obtenu avec une faible défoliation avant et pendant la formation des pommes. Ceci montre que le chou tolère une certaine défoliation avant et pendant la formation des pommes. Les résultats de cette étude ont été utilisés dans une analyse coût-bénéfice pour estimer le seuil économique de défoliation.

     

Phonotaxis in flying crickets: Neural correlates

Tethered, flying crickets perform stereotyped steering movements when stimulated with sound. Electrophysiological recordings show that identifiable motoneurones respond to acoustic stimulation in a manner which reflects the phonotactic behaviour of the intact cricket. Both steering behaviour and its neural correlates reflect the fine temporal structure of the acoustic stimulus. Decapitation of the cricket eliminates steering movements in response to sound.     

Audition in the praying mantis,Mantis religiosa L.: identification of an interneuron mediating ultrasonic hearing

1. The praying mantis possesses a single ear located in the ventral midline of the metathorax. We have studied the mantis' auditory nervous system using both extracellular and intracellular techniques and have identified anatomically and physiologically a mirror-image pair of interneurons (MR-501-T3) in the metathoracic ganglion that mediates ultrasonic hearing. 2. MR-501-T3 is tuned broadly to ultrasound with best sensitivity (55-60 dB SPL) between 25 and 45 kHz. Its tuning matches closely that of the whole tympanal nerve. 3. The physiological responses of MR-501-T3 are characterized by: (1) a phasic-tonic firing pattern with a distinctive initial burst at 500-800 spikes/s; (2) minimum latencies of 8-12 ms; (3) no spontaneous activity; (4) sigmoid intensity response curves with a small (10 dB) dynamic range; (5) accurate coding of stimulus duration and of repetition rates up to 60 pps. 4. The ascending axon of MR-501-T3 conducts action potentials at 4 m/s, a rate comparable with some giant fiber systems. 5. MR-501-T3 shows no directional capability. Sound from right and left produce identical responses in both cells of the pair. Neither cutting one tympanal nerve nor removing one hemi-ear leads to different responses in the two cells indicating that they must receive a common input, either from the auditory afferents or from interneurons. We present evidence that the two cells are not directly connected. 6. MR-501-T3 is a large, symmetrical cell with its processes primarily in the intermediate neuropil (lateral ring tract). Its integration segment crosses the midline in the supramedian commissure, and the cell body lies dorsally near the entrance of the leg nerve. The axon travels in the dorsal lateral tract and is one of the largest (17 microns) in the connective. 7. Given the strong anatomical similarities between MR-501-T3 and the G and B cells of the locust, these cells may be homologous. 8. We present arguments based on our physiological results and existing behavioral data that MR-501-T3 is part of an ultrasonic warning/escape system in the mantis. As in moths, lacewings, and crickets, this system may provide a defense against nocturnally foraging bats.     

Rates and Factors Associated with Major Modifications to First-Line Combination Antiretroviral Therapy: Results from the Asia-Pacific Region

Background

In the Asia-Pacific region many countries have adopted the WHO’s public health approach to HIV care and treatment. We performed exploratory analyses of the factors associated with first major modification to first-line combination antiretroviral therapy (ART) in resource-rich and resource-limited countries in the region.

Methods

We selected treatment naive HIV-positive adults from the Australian HIV Observational Database (AHOD) and the TREAT Asia HIV Observational Database (TAHOD). We dichotomised each country’s per capita income into high/upper-middle (T-H) and lower-middle/low (T-L). Survival methods stratified by income were used to explore time to first major modification of first-line ART and associated factors. We defined a treatment modification as either initiation of a new class of antiretroviral (ARV) or a substitution of two or more ARV agents from within the same ARV class.

Results

A total of 4250 patients had 961 major modifications to first-line ART in the first five years of therapy. The cumulative incidence (95% CI) of treatment modification was 0.48 (0.44–0.52), 0.33 (0.30–0.36) and 0.21 (0.18–0.23) for AHOD, T-H and T-L respectively. We found no strong associations between typical patient characteristic factors and rates of treatment modification. In AHOD, relative to sites that monitor twice-yearly (both CD4 and HIV RNA-VL), quarterly monitoring corresponded with a doubling of the rate of treatment modifications. In T-H, relative to sites that monitor once-yearly (both CD4 and HIV RNA-VL), monitoring twice-yearly corresponded to a 1.8 factor increase in treatment modifications. In T-L, no sites on average monitored both CD4 & HIV RNA-VL concurrently once-yearly. We found no differences in rates of modifications for once- or twice-yearly CD4 count monitoring.

Conclusions

Low-income countries tended to have lower rates of major modifications made to first-line ART compared to higher-income countries. In higher-income countries, an increased rate of RNA-VL monitoring was associated with increased modifications to first-line ART.     

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 August 2012 – 30 September 2012

This article documents the addition of 83 microsatellite marker loci and 96 pairs of single‐nucleotide polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Bembidion lampros, Inimicus japonicus, Lymnaea stagnalis, Panopea abbreviata, Pentadesma butyracea, Sycoscapter hirticola and Thanatephorus cucumeris (anamorph: Rhizoctonia solani). These loci were cross‐tested on the following species: Pentadesma grandifolia and Pentadesma reyndersii. This article also documents the addition of 96 sequencing primer pairs and 88 allele‐specific primers or probes for Plutella xylostella.