Host preference and suitability of some selected crops for two biotypes of Bemisia tabaci in Ghana

The economic importance of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is mainly due to its wide host range, variable kinds of damage, and great intraspecific variation. The delineation of two African biotypes of this pest has been carried by molecular, ecological, and host‐affiliation approaches, with largely consistent results. However, an understanding of its intricate host–pest interaction is necessary as a basis of its sustainable integrated control. This study investigated the host preference and suitability of cassava and okra biotypes of B. tabaci, based on multiple‐choice landing and oviposition preference assays and stage‐specific survival on eight common whitefly hosts. The cassava biotype significantly preferred cassava, Manihot esculenta, for landing and oviposition, but did not oviposit on okra, Abelmoschus esculentus. The okra biotype preferred okra, oviposited on eggplant, Solanum melongena, tomato, Lycopersicon esculentum, garden egg, Solanum integrifolium, and cowpea, Vigna unguiculata, but did not oviposit on cassava. The okra biotype developed on all hosts except cassava, but only survived marginally on cabbage, Brassica oleracea, and pepper, Capsicum annum var. grosum, while the cassava biotype did not develop on okra, cabbage, or pepper. Thus the observed host acceptance of the two biotypes is wider than earlier reported by host transfer experiments and molecular genetic surveys. Mortality was highest in the first instar nymphal stage, during which total mortality occurred on non‐hosts. Development time was slightly longer on marginal hosts than on the preferred hosts. Cowpea, garden egg, and tomato are additional common hosts of the two biotypes, whose role as reservoir hosts and biotype interbreeding grounds should be investigated further.     

Effects of temperature and delayed initial feeding on the survival and growth of Japanese flounder larvae

The effects of the timing of initial feeding (0, 1, 2, 3 and 4 days after yolk exhaustion) and temperature (15, 18 and 21° C) on the point‐of‐no‐return (PNR), survival and growth of laboratory‐reared Japanese flounder Paralichthys olivaceus larvae were studied under controlled conditions. The larvae reached PNR on 7·7, 5·2 and 4·2 days‐post‐hatching (dph) at 15, 18 and 21° C, respectively. At each temperature, larval growth did not differ significantly among the delayed initial feedings 1 day before PNR but decreased significantly in larvae first fed after that. In the treatments where initial feeding was equally delayed, larvae grew significantly faster at 18 and 21° C than at 15° C. The larvae survived apparently better at 15 and 18° C than at 21° C when initial feeding was equally delayed. At each temperature, survival of the larvae first fed before PNR did not differ noticeably, while delayed initial feeding after that apparently reduced their survival. These results indicated that there existed a negatively temperature‐dependent PNR in the Japanese flounder larvae. Survival and growth of the larvae strongly depended on temperature as well as the timing of initial feeding. High temperature accelerated the yolk exhaustion and growth of the larvae and thus reduced their starvation tolerance and survival. To avoid potential starvation mortality and obtain good growth, the Japanese flounder larvae must establish successful initial feeding within 2 days after yolk exhaustion at 15° C and within 1 day at both 18 and 21° C.     

MULE DEER SURVIVAL AMONG ADJACENT POPULATIONS IN SOUTHWEST IDAHO

Abstract: We investigated survival and cause-specific mortality of mule deer (Odocoileus hemionus) on 3 distinct winter ranges in southwest Idaho from 1992 to 1997 to identify demographic variation and potential limiting factors based on a sample of 447 radiocollared deer. During winters 1995–1996 and 1996–1997, we modeled overwinter fawn mortality based on early winter mass, sex, activity, and habitat use variables. Annual survival rates of adult mule deer varied among the 3 adjacent study areas (χ₂² = 10.93, P = 0.004). Overwinter deer survival also varied among study areas (χ₂² = 8.00, P = 0.018), and the study area X year, study area X sex, and study area X age interactions were all significant (P ≤ 0.018). Overwinter survival differences among the study areas were not consistent over time or among sexes and ages of deer. Winter malnutrition was the main cause of mortality for both adults and fawns during the severe winter of 1992–1993, when overall survival was low. Excluding harvest, predation was the major proximate cause of deer mortality during 1993–97 when overall survival was higher. The probability of winter fawn mortality increased with lower mass (χ₂¹ = 7.38, P = 0.007), being male (χ₂¹ = 5.61, P = 0.018), smaller group sizes (χ₂¹ = 3.62, P = 0.057), and using steeper slopes (χ₂¹ = 3.05, P = 0.081). Smaller group sizes and use of steep slopes corresponded to conditions where predators were more successful. Our findings suggest that coyote (Canis latrans) predation was largely compensatory whereas mountain lion (Puma concolor) predation was apparently independent of animal condition and dependent more on deer habitat use. Early winter fawn mass was a better predictor of overwinter fawn survival than a suite of winter resource use variables, lending further support for use of fawn mass to predict winters where fawn mortality may be high. No single population in this study could be used to make reliable inferences regarding deer survival in the other populations. Survival rate measurements should be used cautiously to make inferences in populations where survival has not been directly measured.     

Ontogenesis of catabolic and energy metabolism capacities during the embryonic development of spotted wolffish (Anarhichas minor)

The catabolic and energy metabolism capacities during spotted wolffish (Anarhichas minor) embryogenesis were investigated. We assessed the embryo's ability to catabolize proteins (trypsin-like proteases) and lipids (triglyceride lipase) and examined the development of metabolic capacities using enzymatic assays: ability to use carbohydrates (pyruvate kinase), amino acids (aspartate aminotransferase) and fatty acids (hydroxyacyl-CoA dehydrogenase) for energy production, and aerobic (citrate synthase) and anaerobic (lactate dehydrogenase) energy production. Functional enzymatic systems were detected from the eyed stage (350 degree-days), except for fatty acids, which was detected from 540 degree-days. To compare the development of 1) aerobic and anaerobic pathways and 2) the capacity to mobilize the different energy substrates, enzymatic ratios were calculated. Anaerobic capacity appeared to increase at a significantly higher rate than the aerobic capacity. Ratios revealing the relative capacity to use specific energy substrates showed a significantly slower increase during development in the capacity to use carbohydrates than amino acids and fatty acids. The end of embryogenesis was characterized by a significant decrease in the use of carbohydrates for aerobic energy production but an increasing capacity to use amino acids. Egg survival as affected by the variability in metabolic parameters is discussed.     

Survival capacity in water of Arcobacter species under different temperature conditions

Aims:  To assess the survival capacity in vitro of arcobacters in water at temperatures applied in the food industry.
Methods and Results:  Four strains of each Arcobacter species were inoculated in potable water and water with 1% organic material and stored at 4, 7, 20, 52, 56 and 60°C. Samples were taken at known time points and the numbers of bacteria were determined on Arcobacter -selective medium. All Arcobacter species remained viable for a temperature-dependent period of time, although Arcobacter butzleri displayed a significant longer survival and heat resistance . No significant intraspecies differences were detected, resulting in no definite identification of origin or strain dependency. The survival period for all species was prolonged in the presence of the organic material only for the low temperatures.
Conclusions:  The present study demonstrates that water can act as a reservoir and as a potential source of Arcobacter contamination to humans and animals.
Significance and Impact of the Study:  This study assessed for the first time the survival of all human-related Arcobacter species in water. Particularly A. butzleri showed to be the most robust species with regard to temperature which is interesting as that species is often found in human clinical specimens.     

Functional analysis of the Drosophila immune response during aging

One of the most dramatic changes associated with aging involves immunity. In aging mammals, immune function declines and chronic inflammation develops. The biological significance of this phenomenon and its relationship with aging is a priority for aging research. Drosophila is an invaluable tool in understanding the effects of aging on the immune response. Similar to the state of chronic inflammation in mammals, Drosophila exhibits a drastic up-regulation of immunity-related genes with age. However, it remains unclear whether immune function declines with age as seen in mammals. We evaluated the impact of aging on Drosophila immune function by examining across age the ability to eliminate and survive different doses of bacterial invaders. Our findings show that aging reduces the capacity to survive a bacterial infection. In contrast, we found no evidence that aging affects the ability to eliminate bacteria indicating that the mechanisms underlying immune senescence are not involved in eliminating bacteria or preventing their proliferation.     

白马雪山阴坡林线长苞冷杉(Abies georgei)种群结构特征

长苞冷杉（Abies georgei）是青藏高原特有林线树种。对白马雪山阴坡海拔4 400 m以上林线0.8 hm2样地长苞冷杉种群进行每木调查,分析其种群结构、数量特征及空间分布格局。结果表明：(1）结构呈典型金字塔型,幼苗和幼树在种群中所占比重大,表现为增长型种群,种群个体数随径级的增加而减少,密度为幼苗>幼树>成年树;(2）存活曲线接近Deevy-III型,高径级种群趋于稳定,种群具两个死亡高峰,低径级种群尤其幼苗死亡率高达90％,这是林线区的气候条件如低温、强光照、积雪及冬季冻害等综合作用的结果,种群另一死亡高峰出现于V~VI龄级,种内和种间对空间、光照和养分等生存因子的激烈竞争引起自疏,导致死亡率再度上升;(3）长苞冷杉种群各龄级空间点格局在不同尺度上表现为聚集、随机和均匀分布,以聚集分布为主,由于幼苗来源于种子库且依赖成年树的微生境,幼苗聚集强度和尺度都最大;各龄级关系密切,在不同尺度上表现出显著的相关性。