L'élevage en laboratoire,sur un hote de substitution dePhanerotoma flavitestacea [Hym.Braconidae] récolté dans le milieu naturel: conséquences sur le potentiel biotique de l'espèce

Résumé Des individus issus d'une population dePhanerotoma flavitestacea Fisher élevée dequis 1962 sur un h?te de substitutionAnagasta kühniella Zell., ont été réacclimatés avec succés, en 1968, à leur h?te naturelEctomyelois ceratoniae,Zell. dans la région de Nice où ce parasite n'existait pas jusqu'alors. Quatre ans après l'introduction, cette souche ?de plein air” ramenée au laboratoire et élevée dans les mêmes conditions que la souche d'origine, présente par rapport à celle-ci un certain nombre de particularités biologiques; le nombre d'ovocytes contenus dans les ovaires des jeunes femelles, le rythme de ponte et la ponte totale sont plus faibles, la maturité sexuelle est plus lente à s'établir. Par contre la durée de la période de ponte, la longévité et le nombre d'anomalies ovariennes ne sont pas modifiées.

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Summary Individuals from a population ofP. flavitestacea, reared from 1962 on the substitute hostAnagasta kuehniella, were successfully re-acclimatised in 1968 on their natural hostEctomylois ceratoniae, in the Nice region, were the parasite was hitherto unknown. Four years after the introduction, this “open air” strain, returned to the laboratory and raised under the same conditions as the original strain, showed certain biological pecularities: the number of ovocytes in the ovaries of the young females, the oviposition rhythm and the total oviposition were all reduced, and sexual maturity was delayed. On the other hand, duration of oviposition, longevity and number of ovarian aberrations were not affected.

     

Influence d'une alimentation préalable et du jeûne sur l'apparition de la recherche intensive des proies chez Semiadalia undecimnotata

Résumé Les prédateurs qui vivent aux dépens de ressources alimentaires groupées, modifient leur mode de déplacement après la capture et l'ingestion d'une proie. Ils passent de la recherche extensive (déplacements rapides et linéaires) à la recherche intensive (déplacements lents et sinueux). Chez les adultes et les larves de dernier stade de la coccinelle Semiadalia undecimnotata Schn. (Col., Coccinellidae), dans les premières heures qui suivent leur naissance ou leur mue, l'ingestion d'un premier puceron ne modifie pas les caractéristiques locomotrices individuelles: les déplacements restent de type extensif. Au début de chaque stade, cette coccinelle présente une période de sensibilisation à la proie rencontrée. Durant ces laps de temps, elle doit consommer plusieurs proies avant d'être capable d'adopter la recherche intensive. L'existence d'une période de jeûne avant cette première prise alimentaire favorise, au contraire, l'adoption de la recherche intensive.

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The ladybird, Semiadalia undecimnotata, like all other entomophagous insects feeding on relatively sedentary prey, exhibits two types of walking pattern during the search for prey: xtensive and intensive search. The latter is engaged following detection of visual or chemical cues. Changes in the ladybird search pattern: extensive search—a single prey capture—intensive search, were investigated in relation to experience of prior feeding-periods (experienced coccinellids) or to lack of such experience (naïve coccinellids) and with respect to changes in duration of fasting. The analysis of their pathways was performed initially by comparison of three locomotory paramètres: the number of stops (number/s), the walking speed (mm/s) and the turning-rate (degrees/s), and subsequently by statistical classification (principle components analysis). Unlike experienced coccinellids, observations of naïve coccinellids, indicate that a single feeding session during the three to five hours after emergence of an adult, or ecdysis of the larva, will change the walking pattern slightly. These animals will maintain extensive search or adopt a particular, intermediate locomotory pattern which is a development of extensive search but do not adopt intensive search. Fasting, for periods over twelve hours, favoured intensive search in populations studied. It is probable that the requirement to feed on more than one prey item before adopting intensive search involves concepts such as forms of learning (sensitization).

     

Chronic hyperammonemia alters in opposite ways membrane expression of GluA1 and GluA2 AMPA receptor subunits in cerebellum. Molecular mechanisms involved

Hyperammonemia contributes to altered neurotransmission and cognition in patients with hepatic encephalopathy. Hyperammonemia in rats affects differently high- and low-affinity AMPA receptors (AMPARs) in cerebellum. We hypothesized that hyperammonemia would alter differently membrane expression of AMPARs GluA1 and GluA2 subunits by altering its phosphorylation. This work aims were: 1) assess if hyperammonemia alters GluA1 and GluA2 subunits membrane expression in cerebellum and 2) analyze the underlying mechanisms.Hyperammonemia reduces membrane expression of GluA2 and enhances membrane expression of GluA1 in vivo. We show that changes in GluA2 and GluA1 membrane expression in hyperammonemia would be due to enhanced NMDA receptors activation which reduces cGMP levels and phosphodiesterase 2 (PDE2) activity, resulting in increased cAMP levels. This leads to increased protein kinase A (PKA) activity which activates phospholipase C (PLC) and protein kinase C (PKC) thus increasing phosphorylation of GluA2 in Ser880, which reduces GluA2 membrane expression, and phosphorylation of GluA1 in Ser831, which increases GluA1 membrane expression. Blocking NMDA receptors or inhibiting PKA, PLC or PKC normalizes GluA2 and GluA1 phosphorylation and membrane expression in hyperammonemic rats.Altered GluA2 and GluA1 membrane expression would alter signal transduction which may contribute to cognitive and motor alterations in hyperammonemia and hepatic encephalopathy.     

Nursing biocrusts: isolation,cultivation, and fitness test of indigenous cyanobacteria

Biological soil crusts (biocrust) are microbial communities that develop at the soil surface of drylands and play an important role in erosion control and fertility. Soil surface disturbance from a broad range of natural and human processes (e.g. fire, livestock grazing, off‐road traffic) cause significant losses in biocrust cover and associated ecosystems services. Hence, biocrust restoration is emerging as an important intervention strategy to rehabilitate degraded dryland soils. In a multistep process, we designed protocols for the establishment of “microbial nurseries” to produce photosynthetic cyanobacterial inoculum for biocrust seeding at scale. We first report on the strategy for isolation, directly from the target site, of a large culture collection of cyanobacteria that included multiple representatives of the five most common biocrust taxa. After genetic pedigreeing of these isolates, we could select those that best matched field populations genetically for scale‐up cultivation. We then developed protocols for effective cyanobacterial biomass production to obtain sufficient inoculum. This was followed by conditioning treatments (hardening off) to preacclimate this inoculum to the stressful conditions expected in the field. Finally, we show that the inoculum obtained was fit to thrive in its original soil under natural outdoor conditions if sufficient water was available. We repeated this process successfully for four sites, two in the hot Chihuanuan desert and two in the cooler Great Basin Desert, and on two textural types of soils in each. The cyanobacterial biocrust nursery approach represents a versatile, viable, and safe tool for the rehabilitation of dryland soils.     

Performance of runners and swimmers after four weeks of intermittent hypobaric hypoxic exposure plus sea level training.

This double-blind, randomized, placebo-controlled trial examined the effects of 4 wk of resting exposure to intermittent hypobaric hypoxia (IHE, 3 h/day, 5 days/wk at 4,000-5,500 m) or normoxia combined with training at sea level on performance and maximal oxygen transport in athletes. Twenty-three trained swimmers and runners completed duplicate baseline time trials (100/400-m swims, or 3-km run) and measures for maximal oxygen uptake (VO(2max)), ventilation (VE(max)), and heart rate (HR(max)) and the oxygen uptake at the ventilatory threshold (VO(2) at VT) during incremental treadmill or swimming flume tests. Subjects were matched for sex, sport, performance, and training status and divided randomly between hypobaric hypoxia (Hypo, n = 11) and normobaric normoxia (Norm, n = 12) groups. All tests were repeated within the first (Post1) and third weeks (Post2) after the intervention. Time-trial performance did not improve in either group. We could not detect a significant difference between groups for a change in VO(2max), VE(max), HR(max), or VO(2) at VT after the intervention (group x test interaction P = 0.31, 0.24, 0.26, and 0.12, respectively). When runners and swimmers were considered separately, Hypo swimmers appeared to increase VO(2max) (+6.2%, interaction P = 0.07) at Post2 following a precompetition taper and increased VO(2) at VT (+8.9 and +12.1%, interaction P = 0.007 and 0.006, at Post1 and Post2). We conclude that this "dose" of IHE was not sufficient to improve performance or oxygen transport in this heterogeneous group of athletes. Whether there are potential benefits of this regimen for specific sports or training/tapering strategies may require further study.     

Abundance and chromosomal distribution of six Drosophila buzzatii transposons: BuT1, BuT2, BuT3, BuT4, BuT5, and BuT6

The abundance and chromosomal distribution of six class-II transposable elements (TEs) of Drosophila buzzatii have been analyzed by Southern blotting and in situ hybridization. These six transposons had been previously found at the breakpoints of inversions 2j and 2q ⁷ of D. buzzatii. These two polymorphic inversions were generated by an ectopic recombination event between two copies of Galileo, a Foldback element. The four breakpoints became hotspots for TE insertions after the generation of the inversion and the transposons analyzed in this work are considered to be secondary invaders of these regions. Insertions of the six transposons are present in the euchromatin but show an increased density in the pericentromeric euchromatin–heterochromatin transition region and the dot chromosome. They are also more abundant in the inverted segments of chromosome 2 rearrangements. We further observed that the accumulation of TE insertions varies between elements and is correlated between dot, proximal regions, and inverted segments. These observations fully agree with previous data in Drosophila melanogaster and support recombination rate as the chief force explaining the chromosomal distribution of TEs.Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.Sequence data from this article have been deposited in the EMBL/GenBank Data Libraries under accession number DQ402469.