Seed viability of five wild Saudi Arabian species by germination and X-ray tests

Our objective was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of five wild species (Moringa peregrina, Abrus precatorius, Arthrocnemum macrostachyum, Acacia ehrenbergiana and Acacia tortilis) from Saudi Arabia. Usually several days were required to determine the viability of all five species via germination tests. However, X-ray test will give immediate results on filled/viable seeds. Seeds of all species, except Acacia ehrenbergiana and Acacia tortilis showed high viability in both germination (96–72% at 25/15 °C, 94–70% at 35/25 °C) and X-ray (100–80%) test. Furthermore, there was a general agreement between the germination (19%, 14% at 25/15 °C and 17% and 12% at 35/25 °C) and X-ray (8%, 4%) tests in which seed viability of Acacia ehrenbergiana and Acacia tortilis was very low due to insect damaged embryo as shown in X-ray analysis. Seeds of Abruspreca torius have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (83% at 25/15 °C and 81% at 35/25 °C) and X-ray (96%) tests. Most of the nongerminated seeds of the five species except those of Acacia ehrenbergiana and Acacia tortilis, were alive as judged by the tetrazolium test (TZ). Thus, for the five species examined, the X-ray test was proved to be a good and rapid predictor of seed viability.     

Rhodobacteraceae on the marine brown alga Fucus spiralis are abundant and show physiological adaptation to an epiphytic lifestyle

Macroalgae harbour specific microbial communities on their surface that have functions related to host health and defence. In this study, the bacterial biofilm of the marine brown alga Fucus spiralis was investigated using 16S rRNA gene amplicon-based analysis and isolation of bacteria. Rhodobacteraceae (Alphaproteobacteria) were the predominant family constituting 23% of the epibacterial community. At the genus level, Sulfitobacter, Loktanella, Octadecabacter and a previously undescribed cluster were most abundant, and together they comprised 89% of the Rhodobacteraceae. Supported by a specific PCR approach, 23 different Rhodobacteraceae-affiliated strains were isolated from the surface of F. spiralis, which belonged to 12 established and three new genera. For seven strains, closely related sequences were detected in the 16S rRNA gene dataset. Growth experiments with substrates known to be produced by Fucus spp. showed that all of them were consumed by at least three strains, and vitamin B₁₂ was produced by 70% of the isolates. Since growth of F. spiralis depends on B₁₂ supplementation, bacteria may provide the alga with this vitamin. Most strains produced siderophores, which can enhance algal growth under iron-deficient conditions. Inhibiting properties against other bacteria were only observed when F. spiralis material was present in the medium. Thus, the physiological properties of the isolates indicated adaption to an epiphytic lifestyle.     

长白山针阔混交林不同演替阶段群落系统发育和功能性状结构

群落构建一直是生态学研究的热点,基于系统发育和功能性状量化生境过滤、竞争排斥以及随机过程在群落构建中的作用,能够深入理解群落构建机制。本研究以长白山针阔混交林不同演替阶段的3个5.2 hm~2样地(次生杨桦林、次生针阔混交林、原始椴树红松林)为平台,基于被子植物分类系统Ⅲ(Angiosperm Classification System,APGⅢ)构建的系统发育树和7个关键功能性状(叶面积、比叶面积、叶片厚度、叶片氮含量、叶片磷含量、氮磷比、最大树高),结合环境数据,分析不同演替阶段群落系统发育和功能性状结构。研究表明:(1)各演替阶段7个植物功能性状都表现出显著的系统发育信号,表明植物功能性状受系统发育历史影响;(2)系统发育和功能性状结构在不同演替阶段和不同径级均为非随机状态。随着演替的推进群落系统发育和功能性状结构由聚集走向发散;随着径级的增加,系统发育和功能性状结构的聚集程度减小,表明随着演替阶段的进行和径级增大,竞争性排斥的作用逐渐明显;(3)各演替阶段系统发育和功能性状的周转都为非随机且不同因子对两者的解释力度存在差异。演替早期空间距离的解释力度小于环境距离,说明生境过滤在群落构建中的重要性,而在演替后期空间距离的解释力度大于环境距离,验证了扩散限制在群落构建中的重要性。     

Adipokinetic hormone of the true armyworm, Pseudaletia unipuncta: immunohistochemistry, amino acid analysis, quantification and bioassay

Abstract A cluster of five to seven AKH-like immunoreactive cells lie in each lobe of the paired corpora cardiaca of the true armyworm, Pseudaletia unipuncta. These cells form a mesh work of immunoreactive processes within the corpora cardiaca, and immunoreactive tracts projecting posteriorly over the aorta.
Reversed-phase high performance liquid chromatography of extracts of the corpora cardiaca of P.unipuncta revealed a single large U.V. absorbent peak with a retention time identical to synthetic Manduca- AKH. Amino acid analysis of the contents of this peak yielded a composition identical to that of synthetic Manduca-AKH which was analysed in a parallel manner. Furthermore the material within the peak possessed adipokinetic activity when bioassayed in day 2 adult male P. unipuncta. The corpora cardiaca of similar individuals were found to contain approximately 17.6ng (17.6pmol) of Manduca-AKH equivalents per pair.
Injection of Manduca-AKH into 2-day-old adult male P.unipuncta resulted in a dose-dependent elevation in haemolymph lipid levels with a maximum level of 80–90μmg/μl obtained with 5–10 ng of Manduca-AKH. Continuous flight also elevated haemolymph lipid levels in day 4 adult males with a significant elevation evident in the first samples taken after 15 min of flight and lipid levels plateauing at approximately 100 μg/μl by about 60 min of flight.     

Body temperatures of Namib Desert tenebrionid beetles: their relationship in laboratory and field

Abstract The body temperatures of six apterous species of Namib Desert tenebrionid beetles were measured continuously with indwelling thermocouples under laboratory conditions and in the field. The range of body temperatures selected was within the upper half of their 'tolerated range', which we defined as the temperatures lying between measured critical thermal maximum and critical thermal minimum. In the field, individuals also maintained their body temperatures within the upper half of the 'tolerated range'. These beetles maintained higher body temperatures than those recorded for any other ectothermic insect. Three of the six species maintained lower body temperatures in the field than they selected in the laboratory. The other three species showed no significant difference between field and laboratory body temperatures. We conclude that these beetles are not forced by biotic or abiotic factors to adopt thermal niches which present them with physiological difficulties.     

The effects of unilateral antennectomy on the flight behaviour of male Heliothis virescens in a pheromone plume

Abstract .Unilaterally antennectomized Heliothis virescens (F.) males flying close to the central axis of a plume of sex pheromone display no significant differences in behaviour compared to sham-operated males in course angles, track angles, airspeed and groundspeed. This demonstrates that right/left antennal information is not necessary for normal orientation movements in response to pheromone, but rather that it is 'blended' within the moth's central nervous system before pheromone-mediated manoeuvres are made. However, some unilaterally antennectomized moths (36%) make repetitive, asymmetrical, saw-tooth-shaped tracks during pheromone-mediated upwind progress, whereas control moths never make such tracks. Unilaterally antennectomized moths made such tracks on the side of the plume contralateral to the missing antenna. We hypothesize that these occasional asymmetrical tracks in unilaterally ablated males are the result of reiterative asymmetrical pheromone stimulation of a higher probability on track legs going toward rather than away from the long axis of the plume on males with a single antenna remaining on the 'away from axis' side. Combined with a greater propensity for treated moths to lock onto the plume away from the central axis on one side rather than the other, repetitive successive asymmetrical track legs (resulting in a saw-tooth-shaped track) are commonly observed in these moths. Control moths do also make asymmetric successive track legs but they rarely are repeated and thus are not readily observed.