杜鹃对两种远距离的近缘苇莺的巢寄生:一个平行协同进化的案例?(英文)

大杜鹃(Cuculus canorus)通常寄生小型雀形目鸟类。由于杜鹃雏鸟的排他性拱卵或拱雏,导致宿主繁殖失败,因此宿主进化出如卵识别能力的反寄生策略。反过来,杜鹃也同时进化出如模拟宿主卵的寄生策略。于是两者之间的相互作用可形成类似军备竞赛的协同进化关系。在匈牙利,大苇莺(Acrocephalus arundinaceus)是大杜鹃的主要宿主,寄生率可高达约 40-65%。以往被认为是大苇莺一个亚种的东方大苇莺(A. orientalis)在日本的种群也被大杜鹃寄生(25-40%)。通过采用光纤光谱仪量化大杜鹃及其宿主的卵色特征,我们比较了东、西半球大杜鹃对两种苇莺的寄生模拟程度。鸟类视觉模型显示,对于可见光颜色,杜鹃与宿主之间卵色的模拟程度在匈牙利高于日本,但匈牙利杜鹃和宿主均较大的卵色变异程度可导致卵色模拟困难。杜鹃与苇莺卵色的量度差异在日本较低,这被证明是宿主拒卵行为的一个重要影响因素。苇莺对大杜鹃卵的拒绝率在日本(35%)和匈牙利(37%)相似。与匈牙利不同,在日本,宿主对杜鹃寄生的应对策略如拒卵行为,先于杜鹃的反适应对策。我们认为,两种近缘物种大苇莺对杜鹃寄生的不同反寄生行为,代表了协同进化军备竞赛的不同演化阶段。     

基于人眼评估的灰喜鹊卵色的窝内变异程度与宿主对模拟或非模拟寄生卵的拒绝行为无关(英文)

杜鹃与其宿主之间的协同进化竞赛理论预测,当卵模拟程度较高时,较低的窝内变异(即宿主自己的卵之间差异很小)有利于宿主识别外来寄生卵。这个假说还进一步预测当宿主识别寄生模拟卵时,窝内卵的变异程度在卵识别中所起到的作用将会增加。本研究利用与宿主的卵匹配程度截然不同的人工和天然寄生卵,在大斑凤头鹃(Clamator glandarius)可能的前宿主、同时具备较强的卵识别能力的灰喜鹊(Cyanopica cyanus)中进行实验,通过人工评估宿主窝内卵的变异程度和宿主对卵的区分程度来验证上述推断。西班牙伊比利亚的灰喜鹊依靠寄生卵与自身卵的不相似程度来识别寄生卵:杜鹃模型卵(73.7%)通常比天然的杜鹃卵(44.4%)以及具有更高模拟程度的宿主同种卵(35.5%)更易被拒绝。然而,卵的窝内变异程度与宿主识别这些模拟或非模拟的寄生卵并没有显著相关性。与理论预期相反,本研究发现无论寄生卵的模拟程度如何,对于那些在卵大小方面变异更大的宿主个体来说,更倾向拒绝卵而不是接受。本研究结果表明,该寄生系统中卵的窝内变异程度在卵识别中所起的作用随着寄生卵的模拟程度而变化的假说不成立。在以往研究的基础上,我们还认为卵的窝内变异程度增加,而不是减小,可能会更有利于宿主识别大斑凤头鹃的非模拟卵。     

新西兰寄生性杜鹃对短波光的视觉敏感性(英文)

不同类群的鸟类对于光线中紫外波长部分的敏感程度存在差异。在一些专性巢寄生鸟类的寄生者 - 宿主体系中,寄生卵所反射出来的紫外光对于宿主区分外源鸟卵与自己的卵具有重要作用。反过来说,对于雌性寄主而言,宿主巢中的卵能够最大程度接近自己的卵是非常有利的。虽然视觉敏感性在大多数杜鹃和牛鹂的宿主中都有描述,这些特征在寄主中却少见报道。视觉敏感性能帮助我们理解巢寄生者与宿主之间潜在的感知共进化过程的相关机制以及更好地了解每个物种相应的视觉感知生态。本研究测定了短波长敏感型(SWS1)视蛋白基因的序列来预测两种新西兰专性巢寄生杜鹃——金鹃(Chalcites [Chrysococcyx] lucidus)和长尾噪鹃(Urodynamis[Eudynamis]taitensis)的紫外光敏感性。结果表明两种杜鹃都具有SWS1视蛋白基因,而其最大敏感度集中在短波长光谱中人类可见的紫光部分,而不是紫外光。未来的研究应该关注在鸟类视觉系统下所测的巢寄生者和宿主卵的相似性以及宿主拒绝寄生卵的行为后果这两个方面,来集中探究巢寄生者与宿主之间的视觉敏感度是否匹配。     

澳大利亚的杜鹃及其寄生适应性(英文)

长期以来,人们一直对寄生性繁殖的杜鹃所采用的种种计谋惊叹不已。本文对澳大利亚的寄生杜鹃如何增加寄生巢的可获得性、如何寻找和接近巢以及如何让宿主接受它们的寄生卵与雏鸟进行了综述。这些杜鹃所采用的对策,有一些是世界上其他杜鹃种类也采用的,但有一些对策,如产隐蔽的卵和模拟的雏鸟,却似乎仅见于澳大利亚的杜鹃。泛性寄生的杜鹃因为要应对较多种类的宿主,难度自然远大于专一性寄生的杜鹃种类,这同时也解释了为什么不同种类的杜鹃进化出不同的寄生策略,以避免不同宿主的识别。     

为什么寄生性繁殖的鸟类产厚壳卵?(英文)

鸟类巢寄生是研究协同进化的模式系统。寄生性繁殖的鸟类进化出非常独特、且相对要厚很多的卵壳。关于厚卵壳的进化,主要有以下假说:1)防止产卵损坏假说,即寄生者在巢上将卵产至宿主的巢中时避免损坏;2)防止宿主啄破假说,即厚卵壳可以有效防止宿主对寄生卵的啄破,使其无法扔掉寄生卵;3)雏鸟生长能量假说,即雏鸟具有排他性,由于其较大的身体肌肉骨骼系统发育需要大量钙质,导致卵壳的钙富集而变得较厚;4)抗菌保护假说,即较厚的卵壳有利于保护寄生者的胚胎免于被宿主巢内的微生物所侵害。本文综述了目前关于寄生性繁殖鸟类的厚卵壳进化机制的研究,认为这些假说之间并非相互排斥,但都缺乏足够的实验证据,尽管防止产卵损坏假说和防止宿主啄破假说得到了较多的支持。对于防止宿主啄破假说,如何去量化宿主对寄生卵的拒绝方式如口吞式扔卵、啄破式扔卵和弃巢等,均直接影响到该假说的检验。对此,我们给出了具体的研究建议。     

大杜鹃(Cuculus canorus)与其宿主灰喉鸦雀(Paradoxornis alphonsianus)的卵色模拟(英文)

卵色多态性在大杜鹃(Cuculus canorus)与其宿主灰喉鸦雀(Paradoxornis alphonsianus)中非常明显,在同一地理种群内,大杜鹃和宿主灰喉鸦雀均分别对应出现了蓝色、浅蓝色和白色的卵。已有研究表明这很可能是两者协同进化过程中分裂选择的结果。然而,仅仅基于人眼评估的卵色分析结果是不够的,一是无法准确量化,二则由于人眼无法探测到鸟类所能感知的紫外光(UV)部分。本研究采用光纤光谱仪,量化比较了大杜鹃与其宿主灰喉鸦雀卵色的多态性及模拟程度。结果表明,光谱仪量化结果与基于人眼评估的卵色模拟情况大致吻合,同时发现大杜鹃与灰喉鸦雀二者卵色在紫外光部分也相当模拟。然而,产白色卵的杜鹃与产白色卵的鸦雀之间的模拟程度,要低于产蓝色卵的杜鹃和鸦雀。这表明,灰喉鸦雀产白色卵很可能是由于杜鹃寄生压力所导致的后进化结果。     

南美牛鹂宿主的反寄生防御行为(英文)

牛鹂(Molothrus属,拟鹂科)是一个单起源的类群,包括现存的5种寄生性繁殖鸟类。啸声牛鹂(M.rufoaxillaris)、巨牛鹂(M.oryzivorus)和紫辉牛鹂(M.bonariensis)主要分布在南美。其中,啸声牛鹂与紫辉牛鹂分别代表较古老和最近进化的两个支系,因此有着各自不同的与宿主协同进化的历史。本文研究了紫辉牛鹂的宿主莺鹪鹩(Troglodytes aedon)的拒卵行为,同时综述了以上3种牛鹂的不同宿主的反寄生防御行为。3种牛鹂的宿主均能识别和拒绝非模拟的寄生卵,其中巨牛鹂和紫辉牛鹂的大部分宿主用嘴叼卵,而啸声牛鹂的主要宿主栗翅牛鹂(Agelaioides badius)则用脚扔掉寄生卵。比紫辉牛鹂小的宿主,在遭遇寄生时则不扔卵,也不弃巢。有些宿主比另一些宿主种类对寄生的牛鹂更具有攻击行为。啸声牛鹂的宿主还能够识别非模拟的寄生雏鸟。我们的结果说明,尽管与牛鹂协同进化的历史不同,大部分牛鹂的宿主已经进化出不同类型的反寄生防御对策。     

对大杜鹃30多年研究的综述:知识积累和未来展望(英文)

在欧洲,有超过125种宿主鸟类的巢里都发现有大杜鹃(Cuculus canorus)的卵,但其实常被大杜鹃寄生和利用的宿主种类并不多。寄生不同宿主的大杜鹃可分成显著不同的宿主专一类群(gentes),迄今欧洲已有超过20种宿主专一类群被报道。每一类群的大杜鹃雌鸟所产的卵的颜色和卵形(如斑点)都较为一致,并专门寄生某一特定的宿主鸟。宿主专一类群可同域出现,也可因为地理隔离而不同,甚至仅局限于宿主分布区的某一区域。不同的宿主专一类群可通过卵的不同而加以区分,在大多数情况下,每一宿主专一类群的卵都模拟其寄生的宿主的卵。为什么一些雀形目鸟类被寄生,而另一些却不被利用?为什么同一宿主种群内一些个体能识别和拒绝杜鹃卵,而另一些个体却接受?为什么同一宿主鸟的不同地理种群对杜鹃卵的识别和拒绝变化很大?大杜鹃不同的宿主专一类群之间的差异到底有多大?本文根据目前已有的知识探讨了这些问题,并对未来的研究进行了展望。     

中国的寄生性杜鹃及其宿主多样性(英文)

通过多年的调查资料、观鸟爱好者所提供的图片和文献整理,我们对多杜鹃寄生系统下的中国寄生性杜鹃及其宿主的多样性进行了系统研究。在中国分布的17种寄生性杜鹃中,迄今已发现11种杜鹃的宿主达55种,均为雀形目鸟类,隶属于15科,其中莺科、鸫科和画眉科分别占到寄生记录总数的 22.6%、20.8% 和 17.0%。大杜鹃(Cuculus canorus)的宿主种类最多(45.5%),是中国最常见、宿主多样性最丰富的寄生性杜鹃。不同种类的寄生性杜鹃的卵色不同,而且杜鹃与其宿主之间均呈现明显的卵色多态性,为典型的卵色协同进化。基于人眼观察,大杜鹃、小杜鹃(C. poliocephalus)和八声杜鹃(Cacomantis merulinus)的卵色均与其宿主高度模拟,而鹰鹃(Cuculus sparverioides)、中杜鹃(C. saturatus)和翠金鹃(Chrysococcyx maculatus)则产非模拟的卵。目前仍有6种寄生性杜鹃的宿主不详,亟待加强研究。     

景观格局对牛鹂泛性寄生的长期维持有影响么?(英文)

与大多数巢寄生鸟类不同,一些牛鹂(Molothrus spp.)可以广泛寄生于其分布区内的以及同一群落内的多种宿主;也没有证据表明,同一种群内的寄生个体对宿主物种有专一性。对此,进化滞后假说认为,与其他专性寄生的杜鹃和牛鹂相比,泛性寄生牛鹂是新近才进化的一支;而进化平衡假说则认为,由于寄生牛鹂的"黑手党"效应,宿主识别和拒绝牛鹂寄生卵的代价太大。然而,北美的许多宿主鸟类已进化出特定的反寄生防御行为,这些鸟类几乎都栖息在开阔地带,如草地、灌丛和溪流边。我们认为,北美鸟类生境的景观格局,对长期维持牛鹂的泛性寄生非常重要,同时也很好地解释了为什么北美森林宿主鸟类没有进化出反寄生行为。寄生性的牛鹂需要开阔草地觅食,因而很少见于森林。森林作为"源栖息地"产生的许多宿主,仅由于一些个体的扩散才进入寄生率和捕食风险都较高的片段化森林斑块,即"汇栖息地"。如此,宿主的反寄生行为的进化将非常缓慢,因为大部分个体都来自牛鹂寄生率很低的生境。此外,生境片段化、宿主繁殖扩散和集合种群的动态变化也进一步阻止了宿主反寄生行为的进化。只要北美大片的森林景观依然存在,这种状况就能持续,森林鸟类宿主对牛鹂寄生的反寄生行为就无法快速进化,反过来,牛鹂的泛性寄生也就得以维持。     

Phase I evaluation of CCNU (lomustine) in tumor-bearing cats

1-(2-Chloroethyl)3-cyclohexyl-1-nitrosourea (CCNU) is an alkylating agent in the nitrosourea subclass. A prospective evaluation of CCNU was done to determine the maximally tolerated dosage of CCNU in tumor-bearing cats. Response data were obtained when available. Twenty-five cats were treated with CCNU at a dosage of 50-60 mg/m3 body surface area. Complete hematologic data were available for 13 cats. Neutropenia was the acute dose-limiting toxicity. The median neutrophil count at the nadir was 1,000 cells/microL (mean, 2,433 cells/microL; range, 0-9,694 cells/microL). The time of neutrophil nadir was variable, occurring 7-28 days after treatment, and counts sometimes did not return to normal for up to 14 days after the nadir. Based on these findings, a 6-week dosing interval and weekly hematologic monitoring after the 1st treatment with CCNU are recommended. The nadir of the platelet count may occur 14-21 days after treatment. The median platelet count at the nadir was 43,500 cells/microL. No gastrointestinal, renal, or hepatic toxicities were observed after a single CCNU treatment, and additional studies to evaluate the potential for cumulative toxicity should be performed. Five cats with lymphoma and 1 cat with mast cell tumor had measurable responses to CCNU. Phase II studies to evaluate antitumor activity should be completed with a dosing regimen of 50-60 mg/m3 every 6 weeks.     

Furosemide continuous rate infusion in the horse: evaluation of enhanced efficacy and reduced side effects

Continuous rate infusion (CRI) of furosemide in humans is considered superior to intermittent administration (IA). This study examined whether furosemide CRI, compared with IA, would increase diuretic efficacy with decreased fluid and electrolyte fluctuations and activation of the renin-angiotensin-aldosterone system (RAAS) in the horse. Five mares were used in a crossover-design study. During a 24-hour period, each horse received a total of 3 mg/kg furosemide by either CRI (0.12 mg/kg/h preceded by a loading dose of 0.12 mg/kg IV) or IA (1 mg/kg IV q8h). There was not a statistically significant difference in urine volume over 24 hours between methods; however, urine volume was significantly greater after CRI compared with IA during the first 8 hours ([median 25th percentile, 75th percentile]: 9.6 L [8.9, 14.4] for CRI versus 5.9 L [5.3, 6.0] for IA). CRI produced a more uniform urine flow, decreased fluctuations in plasma volume, and suppressed renal concentrating ability throughout the infusion period. Potassium, Ca, and Cl excretion was greater during CRI than IA (1,133 mmol [1.110, 1,229] versus 764 mmol [709, 904], 102.7 mmol [96.0, 117.2] versus 73.3 mmol [65.0, 73.5], and 1,776 mmol [1,657, 2.378] versus 1,596 mmol [1,457, 1,767], respectively). Elimination half-lives of furosemide were 1.35 and 0.47 hours for CRI and IA, respectively. The area under the excretion rate curve was 1,285.7 and 184.2 mL x mg/mL for CRI and IA, respectively. Furosemide CRI (0.12 mg/kg/h) for 8 hours, preceded by a loading dose (0.12 mg/kg), is recommended when profound diuresis is needed acutely in horses.     

The Epidemiology of Gastrointestinal Nematodes of Dairy Cattle in Central Kenya

The epidemiology of H. placei and of other gastrointestinal nematodes in yearling dairy cattle was examined on two farms in Kiambu District, central Kenya during each of 13 one-month periods from April 1993 to April 1994. On each farm, 32 newly weaned dairy calves were given a single dose of albendazole and then placed on experimental pastures. Twelve of the animals were designated for bi-monthly slaughter (n = 2) and analysis of worm population characteristics and 20 were designated for blood and faecal collection and for weighing. Two parasite-free tracer calves were grazed alongside the weaner calves each month throughout the study period and were also slaughtered for analysis of worm populations. Faecal egg counts, haematological and serum pepsinogen determinations, herbage larval counts, and animal live weight changes were recorded monthly. The study revealed that Haemonchus placei, Trichostrongylus axei, Cooperia spp. and Oesophagostomum radiatum were responsible for parasitic gastroenteritis and that H. placei was the predominant nematode present in the young cattle on both farms. Faecal egg counts from resident cattle and necropsy worm counts revealed that pasture larval levels were directly related to the amount of rainfall. The total worm burdens in the animals were highest during the rainy season (March–June and October–December) and lowest during the dry seasons (July–September and January–February). The very low recovery of immature larvae of H. placei from the tracer calves indicated that arrested development is not a feature of the life cycle of this parasite in central Kenya. The maintenance of the parasite population depended on continuous cycling of infection between the host and the pasture. The agroclimatic conditions of the study area were such that, in general, favourable weather conditions for the development and survival of the free-living stages of gastrointestinal nematodes existed all year round.     

Diversity of Ectoparasites in Sheep Flocks in Sa~o Paulo,Brazil

The occurrence of ectoparasites in sheep flocks is frequently reported but seldom quantified. Sheep production used to be a predominantly family activity in the state of Sa~o Paulo (Brazil), but it began to become a commercial activity in the past decade. Thus, information about the ectoparasites existing in sheep flocks has become necessary. The present data were obtained by means of questionnaires sent to all sheep breeders belonging to the `Associaça~o Paulista de Criadores de Ovinos' (ASPACO; Sa~o Paulo State Association of Sheep Breeders). Response reliability was tested by means of random visits paid to 10.6% of the respondents. Most of the properties (89.5%) reported the presence of one or more ectoparasites. Screw-worm (Cochliomyia hominivorax) was the most frequent ectoparasite (72.5%), followed by bot fly larvae (Dermatobia hominis, 45.0%), ticks (Amblyomma cajennense) and Boophilus microplus, 31.3%) and finally lice (Damalinia ovis, 13.8%). Combined infestations also occurred, the most common one being screw-worm with bot fly larvae (36.0%) followed by bot fly larvae with ticks (13.9%), screw-worm with ticks (9.3%), bot fly larvae with lice (6.9%), and ticks with lice (5.0%). The most common triple combination was screw-worm, bot fly larvae and ticks (12.8%). Breeds raised for meat or wool were attacked by bot fly larvae and ticks more often than other breeds. Lice were only absent from animals of indigenous breeds. The relationships among these ectoparasites are discussed in terms of sheep breeds, flock size, seasonality and the ectoparasitic combinations on the host.     

Evaluation of biohydrogenation rate of canola vs. soya bean seeds as unsaturated fatty acids sources for ruminants in situ

An experiment was conducted to study disappearance of C14 to C18 fatty acids, lag times and biohydrogenation (BH) rates of C18 fatty acids of ground soya bean and canola seeds in situ. Three ruminally fistulated Dallagh sheep were used to determine ruminal BH of unsaturated fatty acids (UFAs). Differences in the disappearance of fatty acids through the bags and lag times were observed between the oilseeds. We saw that the longer the incubation time of the oilseeds in the rumen, the lower the content of C18:2 and C18:3. Significantly higher lag times for both C18:2 and C18:3 were observed in ground canola compared to ground soya bean. BH rates of C18:2 and C18:3 fatty acids in soya bean were three times higher than those of canola. These results suggest that the fatty acid profile of fat source can affect the BH of UFAs by rumen micro‐organisms. So that UFAs of canola had higher ability to escape from ruminal BH. It seems that fatty acid profile of ruminant products is more affected by canola seed compared to soya bean seed.     

Serum biochemical values and mineral element contents of tissues in yaks

Serum biochemical values and the wet weight to dry weight ratios of tissues were determined in yaks in Shandan county of Gansu province. The liver, kidney, heart and muscle contents of seven elements in yaks were also analysed. Most serum biochemical values were similar to those of cattle, camels and sheep, but the calcium concentration was considerably above the normal range for other ruminants. The liver contained the highest concentrations of copper, manganese and cobalt and the kidney of selenium, iron and calcium.Abbreviations Alb albumin - ALT alanine aminotransferase - AST aspartate aminotransferase - BUN blood urea nitrogen - Chol cholesterol - Glob globulin - -GT -glutamyl transpeptidase - IP inorganic phosphorus - TP total protein     

Evaluation of the Microbiological Status of Milk and Various Structures in Mammary Glands from Naturally Infected Dairy Cows

A knowledge of the microbiological status of milk and of the different structures in the mammary glands has great importance in elucidating the pathogenesis of mammary gland infections. The objective of this study was to evaluate the microbiological status of various structures in the mammary glands from naturally infected dairy cows following slaughter. A total of 94 samples of milk, 184 samples of mammary parenchyma, 168 samples of gland cisterns, and 168 samples of teat cisterns were collected for microbiological examination. Microorganisms were detected in 59.9% of all samples, 67.0% of the milk samples, 70.1% of the mammary parenchymas, 55.9% of the gland cisterns and 48.8% of the teat cistern samples. When all samples were considered, coagulase-negative Staphylococcus were the most prevalent (35.7%) followed by coagulase-positive Staphylococcus (12.2%), Corynebacterium bovis (2.4%), Prototheca sp. (1.9%), and Streptococcus dysgalactiae (1.5%). There was a significantly higher occurrence of microorganisms in the milk and mammary parenchyma compared to the gland cisterns and teat cisterns. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development and survival of free-living stages of gastrointestinal nematodes of sheep and goats on pasture in the Nigerian derived savanna

Four grass plots were sequentially contaminated with goat faeces containing known numbers of unembryonated eggs of predominantly Haemonchus contortus and Trichostrongylus spp. between October 1982 and April 1983. Four other plots were similarly contaminated with sheep faeces between February and May 1987. An additional plot was repeatedly contaminated with sheep faeces from February to April 1987. Populations of free-living stages in faeces and of infective larvae (L₃) in the herbage were subsequently monitored until the end of April and June of 1983 and 1987 respectively. During February and May 1987 two control cultures of sheep faeces were incubated in the laboratory at 25°C–30°C and at a constant temperature of 50°C and the free-living development was also monitored. L₃ developed very readily in the faeces cultured at 25°C–30°C and in those spread on a grass plot in October, at the end of the wet season, but developed less on the plot contaminated in May at the start of the wet season. Worm eggs in faeces deposited on plots during the hot dry season (December to April) or incubated at 50°C died and disintegrated after 24–48 h exposure to the high environmental temperatures. The results indicate that it is unlikely that gastrointestinal nematodes of sheep and goats can develop or survive on open pasture during the dry season in the Nigerian derived savanna zone.