Changes in the proportion of endogenous osmotic solutes accumulated by Chlorella emersonii in the light and dark

Abstract. The type of endogenous osmotic solute accumulated by Chlorella emersonii grown at high external osmotic pressure (π_ext) depended on the light/dark conditions: proline accumulated to high concentrations in cells in the light, while sucrose accumulated to high concentrations in the dark. These findings were made during the alternating light dark cycles used to obtain synchronized cultures, i.e. cultures containing cells at only one stage of development at any one time. Similar decreases in proline and increases in sucrose in the dark were found for cells previously grown in continuous light to obtain non-synchronized cultures, i.e. cultures containing cells at all stages of development.
In cultures synchronized at 200 mol m ⁻³ NaCl (π_ext= 1.01 MPa), recently divided 'daughter cells' at the beginning of the light periods contained 60 mol m⁻³ proline and 100mol m⁻³ sucrose, while mature cells towards the end of light periods contained 130 mol m proline and 20 mol m⁻³ sucrose. The changes in proline and sucrose which occurred in synchronized cultures were due mainly to light/dark conditions and to a much lesser extent to different stages of cell development. The proportion of proline to sucrose in daughter cells collected from non-synchronized cultures in continuous light was not different from the proportion in heterogeneous populations of cells.
Results are discussed in relation to the accumulations of two, rather than one, endogenous osmotic solute and to growth reductions of C. emersonii exposed to high external osmotic pressures.     

A comparative study of the effects of NaCl salinity on respiration, photosynthesis, and leaf extension growth in Beta vulgaris L. (sugar beet)

Abstract. Three parameters influencing the capacity for carbon accumulation, i.e. photosynthesis, respiration, and leaf extension growth, were studied in Beta vulgaris L. (sugar beet) cultured in nutrient solution containing 0.5 to 500 mol m⁻³ NaCl. Leaf extension growth was the parameter most sensitive to salinity: the initial rate of leaf extension and final leaf length each declined linearly with increase in external NaCl concentration. Photosynthetic O₂ evolution of thin leaf slices did not decline until salinity levels reached 350 to 500 mol m⁻³ NaCl, while respiratory O₂ consumption was not affected by salinity throughout the range. The results suggest that the influence of salinity on the capacity for carbon accumulation in B. vulgaris occurs primarily through reduction in the area of photosynthetic surface.     

Anin vitro rearing system for the propagation of the ectoparasitoidCatolaccus grandis

An experimental ‘closed’ rearing system, where egg and larval manipulations were eliminated, was developed for the in vitro rearing of Catolaccus grandis (Hymenoptera: Pteromalidae) Burks, an important ectoparasitoid of the cotton boll weevil, Anthonomus grandis Boheman. In this rearing model, n-hexane (a synthetic ovipositional stimulant for this parasitoid), was smeared on the Parafilm® cover of a modified rearing chamber (a Multiwell®) tissue culture plate) to induce the deposition of uncontaminated eggs, on the inner side of this waxy membrane, and on or around an agar retained diet that had been dispensed into the individual chamber wells. When the efficiency of the in vitro rearing system was compared to the current in vivo rearing method for this species, the duration of the life cycle was significantly shorter in parasitoids reared in vivo, but this difference was less than one day (17.8 vs 17.1 days, respectively). On the other hand, the number of eggs laid in the in vitro rearing chamber during a 4 h period was c. 2.5 times greater than in the conventional in vivo rearing apparatus, and adult yields were c. 25% greater when using the in vitro closed rearing method. Male to female ratios were c. 1:9 when reared in vitro as compared to 1.0:1.5 for those reared in vivo. There were no apparent adverse effects of this in vitro rearing system on the parasitoid's general behavior and reproduction after two consecutive generations.     

Provisioning by captive yellow-tufted honeyeaters (Lichenostomus melanops gippslandicus) acting as foster parents for helmeted honeyeater chicks (L. m. cassidix)

A captive breeding program is being conducted with the endangered helmeted honeyeater (Lichenostomus melanops cassidix). Establishment of breeding stock involved cross fostering helmeted honeyeater chicks to breeding yellow-tufted honeyeaters (Lichenostomus melanops gippslandicus). Data were collected on provisioning rates and food preferences of the foster parents in feeding chicks of the helmeted subspecies. Feeding rates varied from 5–6 each hour per chick in the first week to 8–10 per chick in week 3 and were similar for both one- and two-chick broods. Chicks were considered independent by 6 weeks. Provisioning by the foster parents was evenly divided between the sexes. Insects were the main food item fed to nestlings (89.9%). Moths and mealworms were the two most frequently selected items and were the two largest items available. The continued increase of the captive population may provide individuals for release to the wild population, and techniques developed through captive management will help conserve wild populations. © 1994 Wiley-Liss, Inc.     

The biology of the predatory miteHypoaspis miles (Acari: Laelapidae), a potential biological control agent ofBradysia paupera (Dipt.: Sciaridae)

The following aspects ofHypoaspis miles' biology were investigated; development rate of egg to adult at different temperatures, fecundity, longevity and rate of predation on sciarids. With an increase in temperature the time taken for development decreased from 33.7 days at 15°C to 9.2 days at 28°C. The threshold temperature forH. miles to complete its life cycle was between 10° and 12°C. When fed onAcarus siro, H. miles laid 2–3 eggs a day and unfertilized eggs only developed into males. Adults ofH. miles (0–1 day old) survived for 24.0±1.4 days without food and if fed for 6 days and then starved, females lived for 65.4±2.6 days which was significantly longer than males (45.2±3.0 days). With food, 60% of males and females survived for 142 days. All larval instars of sciarids were attacked byH. miles although the numbers consumed were dependent on the size of the larvae. Egg predation was negligible and pupae were not attacked. In productivity studies ofH. miles in culture (fed onA. siro), the time taken for the mites to reach a density of 45–65,000/litre ranged from 76 to 23 days at 15° and 28°C respectively.

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Résumé Différents aspects de la biologied'Hypoaspis miles sont examinés: vitesse de développement de l'oeuf à l'adulte à différentes températures, fécondité, longévité et voracité sur les sciarides. Avec une augmentation de la température, la durée du développement passe de 33,7 jours à 15°C à 9,2 jours à 28°C. La température minimale qui permet le développement complet deH. miles est située entre 10 et 12°C. Quand il est nourri d'"itAcarus siro, H. miles pond 2 à 3 oeufs par jour et seuls les oeufs non fécondés donnent des males. Les adultes deH. miles (agés de 0 à 1 jour) survivent pendant 24±1,4 jours sans nourriture et si elles sont nourries pendant 6 jours puis privées de nourriture, les femelles vivent 65,4±2,6 jours, ce qui est significativement plus long que les males (45,2±3 jours). Avec de la nourriture, 60% des males et des femelles vivent pendant 142 jours. Toutes les larves de sciarides sont attaquées parH. miles, mais le nombre de proies consommées dépend de la taille des larves. La prédation des oeufs est négligeable et les pupes ne sont pas attaquées. Dans des études sur la productivité deH. miles en élevage (nourri deA. siro), la durée nécessaire aux acariens pour atteindre une densité de 45–65 000/1 est de 76 et 23 jours à 15°C et 28°C respectivement.

     

Light, dark and growth regulator involvement in groundnut (Arachis hypogaea L.) pod development

Gynophore elongation and pod formation were studied in peanut plants (Arachis hypogaea L.) under light and dark conditions in vivo. The gynophores elongated until pod formation was initiated. Pod (3–20 mm length) development could be totally controlled by alternating dark (switched on) and light (switched off) conditions, repeatedly. Gynophore elongation responded conversely to light/dark conditions, compared to pods. In this study we aimed to correlate the light/dark effects with endogenous growth substances. The levels of endogenous growth substances were determined in the different stags of pod development. Gynophores shortly after penetration into the soil, white gynophores, released twice the amount of ethylene as compared to the aerial green ones, or to gynophores bearing pods. Ethylene inhibitors had no effect on the percent of gynophores that developed pods, but affected pod size which were smaller compared to the control. A similar level of IAA was extracted from gynophore tips of green gynophores, white gynophores and pods. ABA levels differed between the three stages and were highest in the green gynophores and lowest in the pods.Abbreviations ABA abscisic acid - AOA aminooxyacetic acid - ELISA enzyme linked immunosorbent assay - Ethrel 2-chloroethanephosphonic acid - GC gas chromatography - HPLC High Performance Liquid Chromatography - IAA indole-3-acetic acid - NAA naphthalene acetic acid - RIA radioimmunoassay - STS silver thiosulfhate - TIBA 2,3,6-triiodobenzoic acid     

Using parthenogenesis‐inducing Wolbachia for the selection of optimal lines of the egg parasitoid Trichogramma pretiosum for use in biocontrol

Trichogramma wasps (Hymenoptera: Trichogrammatidae) are egg parasitoids commonly employed in augmentative biological control releases against a variety of mainly lepidopteran pests. By exploiting the mechanism by which the endosymbiotic bacterium Wolbachia induces parthenogenesis in this genus, we created a set of completely homozygous Wolbachia‐infected recombinant isofemale lines (RILs), each consisting of a different combination of the genome of two well‐characterized lines of Trichogramma pretiosum Riley. We subsequently use 16 of these RILs to investigate the effect of genetic variation on various measures associated with offspring production under laboratory conditions. Unsurprisingly, substantial differences were found between the RILs in their propensity to parasitize hosts, the number of hosts they parasitize, and the levels of mortality in their offspring. Such measures can be used to choose an optimal line for biological control purposes. A method was also developed to characterize the 16 RILs using their allelic state at five loci. Essentially, this binary system uses high‐resolution melt analysis to resolve identity at each locus, with alleles originating from either the grandmaternal or grandpaternal line, and is such that each RIL can be distinguished from each other RIL by their allelic state at one or more loci. The method facilitates the easy diagnosis of line origin when two or more lines are competing with each other in competition assays, allowing for the design of more complicated tests of parasitoid quality. Future field experiments will determine which genetic line performs best under more realistic biological control conditions. The fact that these lines are infected with parthenogenesis‐inducing Wolbachia will allow for prolonged rearing without appreciable change in their genetic makeup, which should lead to a predictable biological control performance.     

Effects of diet on female fecundity and larval development in the carrion beetle Necrophila japonica

The carrion beetle subfamily Silphinae (Coleoptera: Silphidae) contains dominant macroinvertebrates of soil ecosystems in temperate zones. However, their feeding habits, which determine the role of each species in the ecosystem, have not been sufficiently studied. Moreover, although a diet shift from necrophagy on vertebrate carcasses to predatory feeding on invertebrates is known to occur in this subfamily, the processes and mechanisms of this shift have also been inadequately addressed. We examined female fecundity and larval development on various diets in a Silphinae species, Necrophila (Eusilpha) japonica (Motschulsky). The experimental diets included a meat diet and various invertebrate diets, which reflect the ‘ancestral’ feeding habit in Silphinae, necrophagy, and the ‘derivative’ feeding habit, predatory feeding. Female fecundity was significantly higher on the meat diet (minced beef) than on an insect larvae diet (mealworms and dipteran larvae) but did not significantly differ from that on an earthworm diet. Larval developmental performance was significantly higher on the earthworm diet than on the meat and insect larvae diets. Our results for larval development were consistent with those of previous stable isotope analyses of the same species, in which isotopic values of larval samples agree with those of hypothetical consumers that utilize earthworms. The consistency of results among different methods indicates that N. japonica larvae are most likely earthworm feeders. In contrast, our results for the female fecundity experiment differed from those of previous stable isotope analyses, in which vertebrate carcasses unlikely serve as the staple diet of adults in the field; thus, the feeding habits of N. japonica adults remain unresolved. Our observations that females and larvae performed best on the meat and earthworm diets, respectively, may indicate that, in Silphinae, the diet shift from necrophagy to predatory habits occurs earlier in larvae than in adults.     

黑水虻幼虫的耐饥力及饥饿幼虫复食后的生物学特性

【目的】旨在明确黑水虻Hermetia illucens幼虫的耐饥力及饥饿幼虫复食后的发育、生殖力等生物学特性,为评估饥饿对黑水虻后续发育的影响并指导生产实践提供依据。【方法】将不同日龄或不同体重黑水虻幼虫进行不同时长的饥饿处理,测定和分析其耐饥力与日龄、百头重的关系;对7日龄幼虫进行不同时长的饥饿处理后再复喂,测定不同饥饿时长对其预蛹出现时间、总预蛹率、预蛹重、成虫繁殖等的影响。【结果】黑水虻幼虫饥饿后的半数致死时间(LT₅₀)与日龄成指数关系,与体重呈线性相关。7日龄幼虫的耐饥力较强,LT₅₀超过了50 d,饥饿30 d时存活率仍然达到了95%。百头重小于0.5 g的个体,其LT₅₀小于30 d;百头重在2～2.5 g的个体,其LT₅₀在45～70 d。幼虫超过8日龄时或百头重超过4.5 g时,多数个体在饥饿5 d时就提前进入了后续发育阶段。7日龄幼虫饥饿40 d内复食,其预蛹率未受到影响,但预蛹重显著增加;短期饥饿(0～10 d)对其成虫产卵量无显著影响,长期饥饿(30～40 d)使其成虫产卵量显著下降;饥饿长达30 d以上时,卵孵化率也显著降低。【结论】本研究明确了不同体重或不同日龄的黑水虻幼虫都具有一定的耐饥力;饥饿幼虫复食后预蛹重显著增加。     

镉对一株深色有隔内生真菌生长、矿质营养与草酸分泌的影响

【背景】深色有隔内生真菌(dark septate endophyte,DSE)广泛定殖于镉(Cd)污染生境的植物根系,具有增强植物镉耐性的重要生态功能,但人们关于DSE对镉胁迫的生理响应的了解有限。【目的】研究一株DSE嗜鱼外瓶霉(Exophiala pisciphila)对镉胁迫的矿质营养与低分子量有机酸分泌的响应。【方法】采用液体培养法,研究不同浓度(0、25、50、100、200、400 mg/L)镉胁迫对DSE菌丝生长、矿质元素(氮、磷、钾、硫、镁、铁、钙)与镉含量、草酸分泌的影响。【结果】随着镉胁迫浓度增加,菌丝生物量显著下降,降幅为22.8%−90.6%,菌丝的氮、钾和铁含量分别减少26.0%−52.8%、53.8%−92.9%和12.8%−34.3%,而磷、镁和钙含量分别增加15.4%−111.4%、20.4%−31.4%和35.1%−62.5%,硫含量在100 mg/L镉胁迫时增加25.1%。镉胁迫还导致培养液pH值下降,草酸浓度及单位菌丝草酸分泌量显著增加。相关分析发现,菌丝镉含量与硫呈显著负相关(P<0.05),与菌丝钾含量呈极显著负相关(P<0.01),与草酸分泌量呈极显著正相关(P<0.01)。【结论】镉胁迫显著抑制DSE的生长,改变矿质元素的吸收,促进草酸分泌。