T-RFLP方法分析城市污水处理厂中细菌群落的动态变化

采用基于16SrRNA基因的末端限制性片段长度多态性技术(T-RFLP),分析了功能稳定的2个城市污水处理系统中(系统A及系统B),细菌群落结构在105d中的动态变化.在研究中,系统A和系统B功能稳定,BOD出水浓度均在8mg/L左右,总氮(TN)出水浓度分别在25mg/L和23mg/L之下.T-RFLP图谱分析表明,系统A中,115、118、123、471、482和835bp等T-RFs的相对丰度变化显著,系统B中,123、471、750和835bp等T-RFs的相对丰度变化显著.移动窗口分析表明,系统A中细菌群落的平均变化率Δt(15d)为21.5%±5.7%,系统B的平均变化率Δt(15d)为22.6%±5.0%.洛伦兹曲线分析表明,系统A中20%的微生物的累积相对丰度为43%～50%;系统B中20%的微生物的累积相对丰度为47%～52%.结果表明,在城市污水处理厂中,稳定的功能并没有藕联着稳定的细菌群落结构.     

2008年南黄海西部浒苔暴发区有机碳的分布特征及浮游植物的固碳强度

根据2008-08-09～2008-08-13在南黄海西部绿潮(浒苔)暴发区取得的溶解有机碳(DOC)、颗粒有机碳(POC)和颗粒氮(PN)的分析数据,结合同步获得的水文环境要素资料,研究了该区域有机碳的分布特征、来源、影响因素以及浮游植物的固碳强度.结果表明,DOC的浓度范围为1.55～3.22mg/L,平均值为2.44mg/L;POC的浓度范围为0.11～0.68mg/L,平均值为0.27mg/L.DOC与POC的分布特征基本一致,呈现近岸高,外海低;表层高,底层低的趋势.POC与TSS的相关分析表明,POC与TSS整体上呈显著正相关,表明TSS的浓度和来源是控制POC浓度高低的重要因素.通过建立POC与PN的一元线性回归模型,估算了样品中PIN的含量.扣除样品中PIN的影响后,沿岸大部分海域POC/PON的平均值8,结合POC/Chl-a比值,表明沿岸海域POC主要是海洋有机质来源,并且存在降解有机物,这可能是调查期间处于绿潮暴发后期,部分浒苔开始腐烂被降解所致.应用初级生产力估算的浮游植物固碳强度的结果表明,南黄海西部绿潮(浒苔)暴发区浮游植物的固碳强度变化范围为167～2017mg/(m2·d),平均为730mg/(m2·d),该区域日固碳量达到2.95×104t.换算至整个黄海,日固碳量为28.03×104t.     

Infanticide by a solitary koinobiont ichneumonid ectoparasitoid of spiders

When encountering an already parasitized host, a parasitoid’s optimal choices (superparasitism, host rejection, host feeding or infanticide) seem to depend on the individual species’ life history, because the same choice may have different fitness consequences. We demonstrate infanticide under laboratory conditions by a polysphinctine, Zatypota albicoxa, which is a solitary koinobiont ectoparasitoid of spiders. The female always removed any previously attached egg or larva from the body of the host spider, Parasteatoda tepidariorum, with a rubbing behaviour. She rubbed her ovipositor back and forth toward the undersurface of the attached egg or of the saddle under the attached larva to pry it off and laid an egg after removal. When removing a larva, the infanticidal female engaged exclusively in unfastening the ‘saddle’ which fastens the larva to the body of the spider. All larvae were removed with the ‘saddle’ attached to the ventral surface of the body. The female invested more time to remove the medium second and the large penultimate instar larvae than to remove eggs and first instar larvae because of the labour involved in unfastening the saddle. Oviposition with infanticide of the medium second and the penultimate instar larvae imposed more time upon the female than that on an unparasitized host. Removal of any previous occupant in spite of the associated labour costs suggests that infanticide will always be adaptive, no matter the time costs to Z. albicoxa, because so much is invested in attacking the host and because the parasitoid cannot detect whether the spider is already parasitized until she achieves subjugation.     

Nuptial coloration of red shiners (<Emphasis Type="Italic">Cyprinella lutrensis</Emphasis>) is more intense in turbid habitats

Communication is shaped and constrained by the signaling environment. In aquatic habitats, turbidity can reduce both the quantity and quality of ambient light and has been implicated in the breakdown of visual signaling. Here, we examined the relationship between turbidity (quantified with long-term data) and the expression of carotenoid-based nuptial coloration in the red shiner (Cyprinella lutrensis), a small-bodied cyprinid. Males in more turbid habitats displayed redder fins, and an experimental manipulation of adult diet suggested that carotenoid intake alone did not explain among-population color differences. These results run counter to similar studies where signal expression decreased in turbid conditions, and may be explained by the non-territorial red shiner mating system, interactions between the mechanism of coloration and the signaling environment, or reduced cost of color expression in turbid habitats (e.g., reduced predation risk). Our results highlight how the behavioral and ecological contexts in which signals function can shape evolutionary responses to the environment.     

The end of the fat dodo? A new mass estimate for <Emphasis Type="Italic">Raphus cucullatus</Emphasis>

A new mass estimate for the dodo (Raphus cucullatus), based on the lengths of the femur, tibiotarsus and tarsometatarsus, is attempted. The obtained mean mass is 10.2 kg, which is less than previous estimates based on other methods, which ranged from 10.6 to 21.1 kg, and much lower than the 50 lbs reported by a seventeenth-century eyewitness. The new estimated mass, which is similar to that of a large wild turkey, seems more realistic than previous ones and supports the hypothesis that contemporary illustrations of extremely fat dodos were either exaggerations, or based on overfed specimens. Pictures of “fat” dodos may also have been based on individuals exhibiting a display behaviour with puffed out feathers.     

Ultrastructure of spermatozoa of <Emphasis Type="Italic">Onthophagus taurus</Emphasis> (Coleoptera,Scarabaeidae) exhibits heritable variation

Sperm competition is thought to be an important selective pressure shaping sperm form and function. However, few studies have moved beyond gross examinations of sperm morphology. Sperm length is subject to sexual selection via sperm competition in the scarab beetle Onthophagus taurus. Here, the structure and ultrastructure of spermatozoa in this species were investigated using light and electron microscopy. Spermatozoa were found to be filiform, measuring about 1,200 mm in length. The sperm head consists of a three-layered acrosome and a nuclear region bearing the anterior extension of the centriole adjunct. Acrosome and nuclear regions are bilaterally symmetric, with their axes of symmetry being orthogonal to each other. Head and flagellar structures are connected by a well-developed centriole adjunct. The sperm heads are asymmetrically surrounded by accessory material and embedded into the cytoplasm of the spermatocyst cell. The accessory material is produced inside the spermatids and then transferred to the outside due to a new membrane formed around the sperm’s organelles. The old spermatid membrane separates the accessory material from the cyst cell. The flagellum contains a 9+9+2 axoneme, two accessory bodies, and two mitochondrial derivatives of unequal size. The major mitochondrial derivative is significantly larger than the minor one. The axoneme is arranged in a sinusoidal manner parallel along the major mitochondrial derivative. The spermatozoa show no progressive motility when released in buffer solution which is likely to be the result of the flagellar arrangement and the structure of the major mitochondrial derivative. The cross-sectional area of the minor and the major mitochondrial derivatives show different patterns of genetic variation. The data provide the first estimates of genetic variation in sperm ultrastructure for any species, and give evidence for the persistence of genetic variation in ultrastructure required for the rapid and divergent evolution that characterizes spermatozoa generally.     

Bone histology of the titanosaur <Emphasis Type="Italic">Lirainosaurus astibiae</Emphasis> (Dinosauria: Sauropoda) from the Latest Cretaceous of Spain

The titanosaur Lirainosaurus astibiae is the only sauropod species known from the Late Cretaceous of the Iberian Peninsula. Lirainosaurus did not reach a gigantic body size and is one of the smallest sauropods discovered to date. Histological analysis of Lirainosaurus bones, focused on diaphyseal transverse sections of appendicular elements, reveals that Lirainosaurus did not exhibit the osseous microstructure typical for large sauropods, but is comparable with that of the coeval titanosaurs Alamosaurus sanjuanensis, Ampelosaurus atacis, and Magyarosaurus dacus, and also shares histological traits with other small to medium-sized sauropodomorph dinosaurs. Lirainosaurus limb bones exhibit a laminar fibrolamellar bone microstructure interrupted by growth marks, fully obliterated in adulthood by intense secondary remodeling processes which tend to replace completely the primary cortex. Lirainosaurus attained smaller sizes than typical sauropods reducing the rate of primary periosteal osteogenesis and developing an extensive secondary remodeling well before the adult size was reached. Histological organization of Lirainosaurus long bones is more mature than observed in basal neosauropods at similar ontogenetic stage, documenting a case of peramorphosis by pre-displacement. This heterochronic growth would be a reversal of the accelerated pattern of bone deposition typical for the sauropod lineage.     

The earliest record of birch mice from the Early Miocene Nei Mongol,China

The earliest species of birch mouse, Sicista primus sp. nov., was recovered from the 17-Ma-old (Early Miocene) Gashunyinadege locality, central Nei Mongol, China. It is ~9 Ma older than the previous first appearance datum of Sicista in Eurasia. This study indicates that North American Macrognathomys is a synonym of Eurasian Sicista, having 12 shared dental characters. As a result, the biogeography of dipodids indicates that Asian Sicista dispersed to North America as opposed to the hypothesis that Sicista originated from the North American clade. Sicista is one of the few extant rodent genera that originated as early as the Early Miocene.     

First Castorid (Mammalia,Rodentia) from the Middle Miocene of Southeast Asia

Today and in the Tertiary, the geographical distribution of castorids is limited throughout all of the northern continents. Fossils of the Castoridae genus Steneofiber are abundant in many localities of Eurasia from the late Oligocene to Pliocene period. Recently, Steneofiber fossils were discovered in two localities of northern Thailand, Mae Moh and Chiang Muan coal mines, in layers of late middle Miocene age. These discoveries represent the first records of castorids from Southeast Asia and correspond to their southernmost known range. The focus of this study is to describe this new Thai species of Steneofiber and to define its wear stages from the molar occlusal surfaces by using micro-CT scan analysis. The CT scan technique permits the analysis of the virtual occlusal surface changes from wear, allowing easier comparison to related species of Steneofiber cheek teeth without destroying the teeth. The new species, Steneofiber siamensis n. sp., can be distinguished from the other species of Steneofiber by several distinct characters, longer mesostriid on p4, presence of premesostria and metastria on P4, which are smaller than most of the other known species. The occurrence of this new castorid also supports a subtropical to tropical paleoclimate for these two localities of northern Thailand.     

Loss of legs: is it or not a handicap for an orb-weaving spider?

Leg loss is a common phenomenon in spiders, and according to the species 5% to 40% of the adults can present at least one missing leg. There is no possibility of regeneration after adult moult and the animal must manage with its missing appendages until its death. With the loss of one or more legs, female orb-weaving spiders can be penalized twice: firstly, because the legs are necessary for web construction and secondly, the legs are essential for the control of the prey after its interception by the web. During development, spiders may be also penalized because regeneration has energetic costs that take away resources for survival, growth and reproduction. All these consequences should influence negatively the development of the spider and thus its fitness. We investigated the impact of leg loss in the orb-weaving spider, Zygiella x-notata by studying its frequency in a natural population and web building and prey capture behaviours in laboratory. In field populations, 9.5% to 13%, of the adult females presented the loss of one or more legs; the majority of individuals had lost only one leg (in 48% of cases, a first one). Leg loss seems to affect all the adult spiders, as there is no difference of mass between intact spiders and those with missing leg. Data obtained with laboratory-reared spiders, showed that the loss of legs due to the moult is rare (less than 1%). Considering changes in web design, spiders with missing legs decreased their silk investment, increased the distance between spiral turns but did not change the capture surface of the web. Under our laboratory experimental conditions, spiders with one or two lost legs did not present any difference in prey capture efficiency. In laboratory conditions, spiders with lost leg(s) did not show any difference in egg sac production or in longevity (adult lifespan) compared to intact spiders.