微藻趋向运动及其靶向运输应用研究进展

微藻主要是指一类能进行光合自养的微生物,且很多藻株还兼具运动特性.因而将微藻与微流控芯片结合,实现精确靶向,或用于分子药物递送,在生物医学治疗和药效学分析等领域有重要的潜在应用价值,也是当今的研究热点之一.然而,目前关于微藻趋向运动的研究及潜在的应用的综述报道却相对较少.本文主要以模式微藻莱茵衣藻为例,概述基于微藻细胞...     

Predation risk and alternative mating tactics in male Trinidadian guppies (Poecilia reticulata)

In the guppy (Poecilia reticulata), males have two alternative mating tactics. Individual males may either display to a receptive female prior to attempting to copulate with her or attempt to quickly sneakcopulate with a female without first displaying to her or without a prior receptive response from her. In this study, I experimentally investigated the effects of simulated local increases in the risk of predation (in the form of a cichlid fish predator model in situ) on the mating tactics used by free-ranging male guppies in two typical macrohabitats (riffle and pool) of a Trinidadian river. Focal male guppies displayed to females significantly less often on average, and conversely attempted sneak copulations more often, in the presence of the predator model than in its absence; this pattern was similar for both habitats. These fish therefore performed a lower proportion of sigmoid displays and increased their sneaky mating attempts when the apparent risk of predation had increased locally. This predator-mediated response is consistent with a trade-off between mating success and risk of mortality due to predation. The results are the first to confirm risk-sensitive mating behaviour in free-ranging male guppies within a population, and demonstrate the potential importance of predators in influencing the relative use of alternative mating tactics in this species on a microgeographical scale in the wild.     

Regulation of Yolk-Androgen Concentrations by Plasma Prolactin in the American Kestrel

The concentrations of maternally derived androgens in the yolks of avian eggs vary within and among clutches, but a mechanistic basis for this variation has not been elucidated. We investigated in the American kestrel, Falco sparverius, whether changes in plasma-prolactin concentrations induced by changes in photoperiod and food supply affect yolk-androgen concentrations. Over the course of a photoinduced breeding period in the laboratory, we measured concentrations of plasma immunoreactive prolactin (ir-prolactin) in female kestrels with ad libitum food availability (control) or food availability that was reduced during the early breeding period. In a second laboratory study, we administered via osmotic mini-pumps ovine prolactin (o-prolactin) to females beginning on the day they laid their first egg of a clutch (egg-day 1) to determine the effects of high prolactin concentrations on yolk-androgen concentrations. In both this study and one on free-living kestrels, we quantified changes in yolk-androgen concentrations with date of clutch initiation. Concentrations of ir-prolactin in nonlaying females rose with date, irrespective of food treatment. Egg-day 1 ir-prolactin concentrations were higher in control females laying late during the breeding phase than in those laying early. This increase was absent in food-reduced females. Yolk-androgen concentrations in eggs 3 and 4 but not eggs 1 and 2 of the clutch were higher in clutches initiated late than in clutches initiated early in the breeding phase in both the field and laboratory. o-prolactin treatment elevated yolk-testosterone but not androstenedione concentrations. These findings suggest that, in American kestrels, seasonal and laying-associated increases in plasma-prolactin concentrations elevate yolk-testosterone concentrations. Food availability and other factors may interact with date to regulate the effects of prolactin on yolk-testosterone deposition.     

Behavioral responses to prey density by three acarine predator species with different degrees of polyphagy

Behavioral responses by three acarine predators, Phytoseiulus persimilis, Typhlodromus occidentalis, and Amblyseius andersoni (Acari: Phytoseiidae), to different egg and webbing densities of the spider mite Tetranychus urticae (Acari: Tetranychidae) on rose leaflets were studied in the laboratory. Prey patches were delineated by T. urticae webbing and associated kairomones, which elicit turning back responses in predators near the patch edge. Only the presence of webbing affected predator behavior; increased webbing density did not increase patch time. Patch time increased with increased T. urticae egg density in the oligophagous P. persimilis, but was density independent in the polyphagous species T. occidentalis and A. andersoni. Patch time in all three species was more strongly correlated with the number of prey encounters and attacks than with the actual prey number present in the patch. Patch time was determined by (a) the turning back response near the patch edge; this response decayed through time and eventually led to the abandonment of the patch, and (b) encounters with, and attacks upon, prey eggs; these prolonged patch time by both an increment of time spent in handling or rejecting prey and an increment of time spent searching between two successive prey encounters or attacks. Although searching efficiency was independent of prey density in all three species, the predation rate by P. persimilis decreased with prey density because its searching activity (i.e. proportion of total patch time spent in searching) decreased with prey density. Predation rates by T. occidentalis and A. andersoni decreased with prey density because their searching activity and success ratio both decreased with prey density. The data were tested against models of predator foraging responses to prey density. The effects of the degree of polyphagy on predator foraging behavior were also discussed.     

Mate acquisition tactics in polyandrous spotted sandpipers (Actitis macularia): the role of age and experience

We consider resource-defense polyandry and mate-access polyandryas female mating tactics in spotted sandpipers (Actitis macularia).These tactics can be distinguished by the resource females defend,female interclutch movement, expected reproductive success aftermoving, and male and female dispersion. We examine these characteristicsrelative to patterns observed in a 17-year study of spottedsandpipers, a species traditionally considered resource-defensepolyandrous. On average, 26% of spotted sandpiper females eachyear were monogamous. Older females were more likely to be polyandrous,and polyandrous females of each age employed different matingtactics. Yearlings were typically sequentially resourcedefensepolyandrous. Two-year-olds were primarily simultaneously polyandrous,exhibiting equivalent proportions of resource-defense and mate-accesspolyandry. Older females were primarily simultaneously resource-defensepolyandrous. Females tended to stay on territories where theyand/or their mates had greater breeding experience (i.e., manyclutches laid for females, many clutches diat hatched for males);females that moved went to territories where their mates hada history of breeding success. Location changes between clutchesby polyandrous females were better described by breeding experienceon a territory than by age.     

季节性和综合害虫管理策略实施时间对害虫控制的影响(英文)

通过建立具有季节变化和综合脉冲控制效应的非自治捕食与被捕食模型,我们得到了保证害虫根除的临界条件,即得到了保证害虫根除周期解全局稳定的充分条件.进而我们讨论了季节性变化以及最优的害虫控制策略实施时间对临界条件的影响.结论显示当害虫种群数量具有季节波动时,系统存在使得临界值达到最小的最优控制策略实施时间.     

Configuration of daily grazing and searching of growing beef cattle in grassland: observational study

Many of the studies in Campos grasslands focus on management aspects such as the control of herbage allowance, and application of nutrients and/or overseeding with legumes. However, there is little literature on how the Campos grassland resource is utilised, especially regarding the grazing pattern and the relationship between pasture quantity and quality on daily grazing activities. The study of the ingestive behaviour in species-rich and heterogeneous native grasslands during daylight hours, and understanding how animals prioritise quality or quantity of intake in relation to pasture attributes, are important to comprehend the ingestive-digestive processes modulating the energy intake of animals and to achieve a better grazing management. Therefore, the objective was to describe and quantify the daily grazing behaviour of growing cattle grazing native pasture with different structures as a result of different management practices, and study the relationship of pasture attributes and intake through multivariate analysis. The study was carried out at the Faculty of Agronomy, Paysandú, Uruguay. Treatments were native grassland, overseeding with Trifolium pratense and Lotus tenuis + phosphorus, and native pasture + nitrogen-phosphorus. Grazing activities were discriminated into grazing, searching (defined when animals take 1–2 bites in one feeding station and then change to another feeding station and so on), ruminating and idling. The probability of time allocated to each activity was continuously measured during daylight hours (0700–1930) and was related to pasture structure and forage quality using regression tree models, while the bite rate was determined every 2 h. The diurnal pattern of growing cattle showed grazing and searching sessions, followed by ruminating and idling sessions. The length of sessions (as the probability of time allocated to each activity) varied throughout the day. The grazing probability was greater during afternoon than morning and midday (0.74 vs 0.45 vs 0.46, respectively), and it was associated with higher bite rate (34.2 bites/min). Regression tree models showed different grazing, searching and ruminating strategies according to pasture attributes. During the morning, animals modified grazing, searching, ruminating and idling strategies according to bite rate, crude protein in diet and herbage allowance. At midday, they only adjusted ruminating and idling, while during afternoon sessions, grazing activities were modified by pasture quantity attributes such as herbage mass and herbage allowance. By controlling the herbage allowance, herbage mass and pasture height, animals prioritise quality in the morning and quantity in the afternoon, integrating and modifying the grazing-searching and ruminating-idling pattern.     

Experience does not alter alternative mating tactics in the burying beetle Nicrophorus vespilloides

Alternative male mating tactics are widespread, but the cuesthat determine which tactic is adopted remain unclear. Sizeis commonly associated with alternative mating tactics, butit is not known how individuals gauge their size effectively,especially given that size is relative and frequency dependent.One possibility is that interactions with conspecifics are usedto assess size, relative to potential competitors, and thusfine-tune tactics. Success in mating might also influence matingtactics given that this should indicate the potential availabilityof mates in the population. We tested these ideas in the buryingbeetle Nicrophorus vespilloides, examining whether individualsuse the outcome of larval or adult interactions as cues to adjustthe tactics used to acquire mates. Male N. vespilloides employ2 tactics; search for a carcass, a resource required for reproduction,or release a pheromone (call) to attract a mate. Males are plasticin the amount of time they invest in each tactic, and in a relatedspecies (Nicrophorus orbicollis), male size influences the tacticadopted. We examine the potential effects of parental care,sibling competition, relative size within a brood, and adultexperience of agonistic interactions and mating on tactic adoption.Absolute size was consistently the best predictor of callingrate, with smaller males calling more often than larger males.We suggest that the lack of a response to adult cues may reflectunpredictability in the occurrence of social interactions orstable size distributions in this population.