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1.
Preserved skin of small dinosaurs is rare. Here, a specimen of the ceratopsian dinosaur, Psittacosaurus, presents some of the best preserved epidermal scales observed to date in a relatively small dinosaur, over wide areas extending from the head to the tail. We study the preserved epidermis of SMF R 4970, the different types of scales, color, and patterns, and their respective locations in the body. We use modern application of high-power digital imaging for close-up analysis of the tubercles and fragments of preserved color. Three types of scales are preserved, large plate-like scales, smaller polygonal scales or tubercles, and round pebble-like scales. The sizes of the plate-like scales vary in different parts of the body and vanish altogether posteriorly. Light and dark cryptic patterns are created by the associations of the tubercle and plate-like scales, and there is also evidence of countershading in the proximal caudal region, the body darker dorsally and lighter ventrally. Perhaps most impressive are the distinctive pigmented impressions of scales over most of the skeletal elements. The pigmentation follows the curvature of the bones implying that when it was deposited, the skin was still pliable and able to wrap around the visible parts of the elements. The present record of color is the first in a non-theropod dinosaur and only the second record in a non-avian dinosaur. Because of its resistance to degradation and ability to produce various color tones from yellows to blacks, we suggest that melanin was the dominant chemical involved in the coloration of Psittacosaurus. The data here enable us to reconstruct the colors of Psittacosaurus as predominantly black and amber/brown, in cryptic patterns, somewhat dull, but useful to a prey animal. Indeed, skin pigment within a partially degraded bone indicates that Psittacosaurus was scavenged shortly after death. The theropod dinosaur Sinosauropteryx has recently been reported to have naturally pigmented integumental structures, which the authors interpret as proof that they are protofeathers and not support fibers of collagen. Our findings in Psittacosaurus, on the other hand, indicate a more parsimonious and less profound alternative explanation, i.e., decomposition of the skin releases pigments that readily permeate underlying structures.  相似文献   

2.
The early origin of birds is a hotly disputed debate and may be broadly framed as a conflict between paleontologists and ornithologists. The paleontological emphasis has shifted from Archaeopteryx and its origins to recent finds of Cretaceous birds and feathered dinosaurs from China. The identification of alleged feathers has, however, relied principally on the visual image. Some workers have interpreted these integumentary structures as collagen fibers. To test the latter hypothesis, using light microscopy, collagen from the hypodermis (blubber) and subdermal connective tissue sheath was examined from a dolphin that had been buried for a year as part of an experiment. Within the blubber, toward the central thicker parts of the material, the collagen fibers had compacted and the three-dimensional latticework of normal blubber had more or less collapsed. Chromatographic analysis of the blubber revealed pronounced oxidation of the unsaturated lipids, probably accounting for the collapse of the latticework. Fibers normally bound together in bundles became separated into individual fibers or smaller bundles by degradation of the glue-like substance binding them together. These degraded collagen fibers show, in many instances, feather-like patterns, strikingly reminiscent of many of those identified as either protofeathers or modern feathers in dromaeosaurid dinosaurs. The findings throw serious doubt on the virtually complete reliance on visual image by supporters of the feathered dinosaur thesis and emphasize the need for more rigorous methods of identification using modern feathers as a frame of reference. Since collagen is the main fiber type found in most supporting tissues, the results have wide implications regarding the degradation and fossilization of vertebrate integument, such as that of the ichthyosaurs, dinosaurs and birds.  相似文献   

3.
Agustinia ligabuei is an Early Cretaceous sauropod dinosaur from the northwest of Patagonia that is currently the topic of debate with respect to its phylogenetic position and atypical dermal armor. The presence of four morphotypes of laminar and transversely elongated putative osteoderms was used to consider Agustinia as an armored sauropod. Regarding the different hypotheses about the identity of the bony structures of Agustinia (e.g., osteoderms, cervical or dorsal ribs, hypertrophied elements), a comparative histological analysis has been carried out. Histological evidence is presented herein and reveals that none of the morphotypes of Agustinia shows a primary bone tissue formed by structural fiber bundles as in other sauropod dinosaur osteoderms. Furthermore, on the basis of their gross morphology and microstructure, the bony structures originally classified as types 1 + 4 and 3 are more comparable respectively with dorsal and cervical ribs than any other kind of dermal or bony element. Due to poor preservation, the nature of the type 2 cannot be assessed but is here tentatively assigned to a pelvic girdle element. Although a phylogenetic reassessment of Agustinia is not the purpose of this paper, our paleohistological analyses have broader implications: by not supporting the dermal armor hypothesis for Agustinia, its inclusion in Lithostrotia is not justified in the absence of other diagnostic features.  相似文献   

4.
Diversification of sperm morphology has been investigated in the context of sperm competition, but the adaptive significance of sperm bundles is still unclear. In analyzing 10 taxa of the genus Carabus subgenus Ohomopterus and one related Carabus ground beetles, we found that dimorphic sperm bundles occurred in most species with varied degrees of bimodality, whereas sperm were generally monomorphic. Comparative analyses with phylogenetically independent contrasts revealed that the sizes of large and small sperm bundles evolved more rapidly than, and were not correlated with, the length of sperm, suggesting more intense selection on sperm bundle sizes and their independent responses to different evolutionary forces. The size of large sperm bundles was positively correlated with male genital morphology (pertinent to displacement of rival spermatophores) and postcopulatory guarding duration as well as male body length, suggesting that larger sperm bundles have been favored when the risk of spermatophore displacement is high. Larger sperm bundles may be advantageous because of their ability to migrate more rapidly into the spermatheca. In contrast, no clear association was detected between the small sperm bundle size and mating traits despite its rapid diversification. The present study provides the first record of heteromorphic sperm bundles, the diversity of which may be promoted by sperm competition.  相似文献   

5.
陈平  胡琰茹  刘晓莉 《环境科学研究》2017,30(11):1739-1745
为了观察SO2污染环境下运动对大鼠心功能的影响,从心脏局部肾素-血管紧张素系统(renin-angiotensin system,RAS)核心成员——血管紧张素Ⅱ(angiotensin Ⅱ,AngⅡ)Ⅰ型受体(AT1R)介导的心肌胶原纤维形态结构重塑的角度出发,应用心脏插管技术观察大鼠的心脏功能;采用放射免疫技术(ELISA)、免疫组织化学和胃酶酸解法等方法对心肌局部ρ(AngⅡ)、AT1R蛋白表达水平、w(HYP)(HYP为羟脯氨酸)及胶原容积分数进行检测.结果表明:①单纯运动组(EG)大鼠主动脉收缩压、左室内压峰值、±dp/dtmax(左室内压最大上升速率/下降速率)显著升高(P < 0.01),舒张压、AT1R蛋白表达显著降低(P < 0.01),w(HYP)、w(CC)(心肌胶原浓度)、PVCA(血管周围胶原面积)、CVF(心肌胶原容积分数)及ρ(AngⅡ)有升高趋势(P>0.01);②单纯SO2污染组(SRG)大鼠左室末期舒张压显著升高(P < 0.01),左室内压±dp/dtmax显著降低(P < 0.01);w(HYP)、w(CC)、PVCA、CVF、ρ(AngⅡ)及AT1R蛋白表达水平均显著升高(P < 0.01);③SO2污染+运动组(SEG)大鼠左室末期舒张压显著升高(P < 0.01),主动脉收缩压、左室内压峰值、左室内压±dp/dtmax显著降低(P < 0.01),w(HYP)、w(CC)、PVCA、CVF、ρ(AngⅡ)及AT1R蛋白表达水平均显著升高(P < 0.01),并且较SRG大鼠升高更显著(P < 0.01).研究显示,SO2污染导致运动大鼠心肌胶原纤维形态结构发生异常重塑,最终使大鼠的心功能产生显著的负性变力性效应,其机制可能与心脏局部RAS系统的激活有关.   相似文献   

6.
The peculiar biogeography of the so-called Lost World, i.e. the summits of sandstone tableaux (tepuis) in the Neotropical Guyana region of Venezuela, has generated a debate regarding the factors that are thought to account for modern vegetation patterns in the region. Some argue that plant communities on these high-elevation summits reflect a long history of evolution in isolation, while others surmise that there has been substantial biotic interchange with the surrounding lowlands during glacial times. Until now, these apparently competing hypotheses have not been tested using palaeoecological methods. I used pollen analysis of Quaternary sediments and documented past vertical migrations of vegetation in response to climate changes, which supports the second hypothesis. Physiographical analysis, however, shows that about half the tableaux summits are too high for their flora to have reached the lowlands during the last glaciation, suggesting that a portion of the tableaux vegetation has always experienced some degree of biotic isolation. Thus, a component of the summit vegetation evolved in isolation, whereas other taxa experienced interchange, as reflected in endemism patterns among the tableaux summits. Biogeographical patterns on the summits are the result of complex evolutionary processes. The two hypotheses invoked to explain the vegetation patterns are not mutually exclusive, but instead complement one another.  相似文献   

7.
絮凝条件对絮体分形结构的影响   总被引:20,自引:3,他引:17  
在85kg/m3的含沙高浊水中投加阳离子高分子聚合物,借助图像分析技术与沉降技术分析探讨了不同絮凝条件下泥沙絮凝形态学参数:絮体粒径、絮体有效质量密度、絮体自由沉速、浑液面沉速与上清液余浊等的变化规律.利用表征参数“分维”定量控制不同絮凝条件(如搅拌速率、搅拌时间、高分子浓度等)对含沙高浊水絮体结构分形特性的影响.实验证明,不合适的絮凝条件将导致絮体分形构造疏松脆弱,分维值低.絮凝条件合适时(快速絮凝强度为:r1=300r/min,t1=10s;慢速絮凝强度:r2=120r/min,t2=180s;CP浓度:0.1%),絮体分形结构处于最佳状态.该状态下的絮体具有粒径较大、沉速快、有效质量密度高、粒度分布均匀,分维值最高(D3=2.16)的特点.而且,由静沉实验测得浑液面沉速高,上清液余浊也低.泥沙絮体分形结构达最佳时的混凝性能、沉降性能与结构密实性均较理想.  相似文献   

8.
The locomotor activity rhythm of different castes of the ant species Camponotus compressus was monitored individually under laboratory light/dark (LD) cycles, and under continuous darkness (DD). The colony of this ant species comprises two sexual castes, the queens and the males, and three worker castes, namely the major, media, and minor workers. The virgin males and virgin queens display rhythmic activity patterns, but the mated queens were arrhythmic while laying eggs, with the rhythmicity resuming soon after egg-laying. Under the LD regime, major workers showed nocturnal patterns, while about 75% of the media workers displayed nocturnal patterns and about 25% showed diurnal patterns. Under the DD regime, most major workers exhibited circadian rhythm of activity with a single steady state, whereas media workers displayed two types of activity patterns, with activity patterns changing after 6–9 days in DD (turn-arounds). The pre-turn-around of the ants that showed nocturnal activity patterns during LD entrainment was <24 h after release into DD, which then became >24 h, after 6–9 days. On the other hand, the pre-turn-around of those ants that exhibited diurnal patterns during LD entrainment was first >24 h after release into DD, and then became <24 h, after 6–9 days. The activity of the minor workers neither entrained to LD cycles nor showed any sign of free-run in DD. It appears that the circadian clocks of the ant species C. compressus are flexible, and may perhaps depend upon the tasks assigned to them in the colony.  相似文献   

9.
Kapok fibers have been acetylated for oil spill cleanup in the aqueous environment. The structures of raw and acetylated kapok fiber were characterized using Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Without severe damage to the lumen structures, the kapok fibers were successfully acetylated and the resulting fibers exhibited a better oil sorption capacity than raw fibers for diesel and soybean oil. Compared with high viscosity soybean oil, low viscosity diesel shows a better affinity to the surface of acetylated fibers. Sorption kinetics is fitted well by the pseudo second-order model, and the equilibrium data can be described by the Freundlich isotherm model. The results implied that acetylated kapok fiber can be used as the substitute for non-biodegradable oil sorption materials.  相似文献   

10.
The larvae and pupae of the ladybird Thalassa saginata develop inside colonies of the dolichoderine ant Dolichoderus bidens. This association is the first specific and obligatory relationship recorded between ants and ladybirds. The ants provide shelter and protection to the larvae but the diet of the latter remains unclear. The integration of T. saginata larvae into the ant colonies is achieved by mimicking the cuticular patterns of the ants brood. Moreover, the larvae secrete substances from their hairs and anal gland that are likely to enhance their attractiveness.  相似文献   

11.
Ingestion of antioxidants has been argued to scavenge circulating reactive molecules (e.g., free radicals), play a part in mate choice (by mediating access to this important resource), and perhaps increase life span. However, recent work has come to question these relationships. We have shown elsewhere in the polychromatic lizard, Ctenophorus pictus, that diet supplementation of carotenoids as antioxidants does not depress circulating natural reactive oxygen species (ROS) levels and leads to no corresponding improvement of color traits. However, a much stronger test would be to experimentally manipulate the ROS levels themselves and assess carotenoid-induced ROS depression. Here, we achieve this by using carbonyl cyanide 3-chlorophenylhydrazone, which elevates superoxide (SO) formation approximately threefold at 10 μM in this model system. We then look for depressing effects on ROS of the carotenoids in order to assess whether ‘super-production’ of SO makes carotenoid effects on elevated ROS levels detectable. The rationale for this treatment was that if not even such elevated levels of SO are reduced by carotenoid supplementation, the putative link carotenoids, ROS depression, and mate quality (in terms of antioxidant capacity) is highly questionable. We conclude that there is no significant effect of carotenoids on mean SO levels even at the induced ROS levels. However, our results showed a significant interaction effect between carotenoid treatment and male color, with red males having higher ROS levels than yellow males. We suggest that this may be because different pigments are differently involved in the generation of the integumental colors in the two morphs with concomitant effects on ROS depletion depending on carotenoid uptake or allocation to coloration and antioxidation.  相似文献   

12.
三江平原湿地开垦对土壤微生物群落结构的影响   总被引:13,自引:10,他引:3  
王娜  高婕  魏静  刘颖  庄绪亮  庄国强 《环境科学》2019,40(5):2375-2381
过度开垦会导致湿地生态系统的快速退化,湿地土壤微生物能够敏感地反映湿地土壤质量及湿地生态系统功能的演变.为研究土地利用变化对湿地微生物群落结构的影响,以黑龙江抚远三江湿地保护区为研究对象,采集其中的原始泥炭湿地、开垦后改种豆科植物及水稻的3种湿地土壤.采用基于细菌16S rRNA基因的高通量测序技术研究上述土壤细菌的群落结构,并探讨其与土壤环境因子间的关系.结果表明,不同土地利用方式湿地土壤中的优势菌门均为变形菌门(Proteobacteria)、放线菌门(Actinobacteria)及酸杆菌门(Acidobacteria),但土地利用方式明显改变了湿地土壤细菌属的组成.改种豆科植物土壤中Blastocatella、Coxiella、Rickettsia丰度较高,水稻田土中Massilia、Nitrosomonas、Bradyrhizobium聚集较多,而泥炭湿地中含较高丰度的Rhizomicrobium、Arthrobacter、Bacillus.结合Chao值与Shannon指数,水稻田土微生物多样性高于改种豆科植物土壤及泥炭湿地土壤,而后两种土壤细菌群落多样性则未见明显差异.相关性分析表明,土壤p H及含水率是影响微生物群落组成的重要驱动因子,说明湿地土壤开垦后改变了土壤p H、含水率及土壤养分,从而对微生物群落结构产生影响.  相似文献   

13.
In ancient Lake Baikal (East Siberia), freshwater sponges have diversified to an extraordinary degree. The skeleton of Lubomirskia baicalensis, which attains a size of up to 1 m, is constructed from spicules, which are cemented into longitudinal bundles. Our X-ray analysis revealed that the architecture of the specimens follows a highly ordered radiate accretive growth pattern. The spicules have a central axial canal with an axial filament inside. This organic filament is composed of silicatein, the major enzyme involved in silica formation of the spicules. We found that the specific activity of silicatein in samples from the non-growing (basal) zone is much lower than in those from the growth zone (tips) and that even the composition of this molecule differs in these regions. The present study shows for the first time that the turnover of silicatein, the major element of the axial canal of sponge spicules, changes within a sponge specimen depending on the region in which it is found.  相似文献   

14.
Caterpillars have many natural enemies and, therefore, have evolved a diversity of antipredator strategies. Most research focuses on those strategies (crypsis, countershading, and warning coloration) targeting visually guided predators. In contrast, defensive sounds, although documented for more than a century, have been poorly studied. We report on a novel form of sound production—chirping—in caterpillars of the common European Great Peacock moth (Saturnia pyri). Chirps are broadband, with dominant peaks ranging between the sonic (3.7 kHz) and ultrasonic (55.1 kHz) and are generated by a rapid succession of mandibular “tooth strikes.” Chirp trains are induced by simulated predator attacks and precede or accompany the secretion of a defensive chemical from integumental bristles, supporting our hypothesis that these sounds function in acoustic aposematism. We propose that these caterpillars generate multimodal warning signals (visual, chemical, and acoustic) to target the dominant sensory modalities of different predators, including birds, bats, and invertebrates. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

15.
Sex ratios of ants have been shown to vary with food resource levels in several studies, but it is not known whether forest clear-cutting has any effect on sex ratio of aphid-tending forest-dwelling ants. We investigated whether the offspring sex ratio of the forest dwelling ant Formica aquilonia varied as a response to clear-cutting. We found that the proportion of males was smaller in clear-cuts than in adjacent forests. Our results are among the first showing that anthropogenic changes in forest structures may have a potential to modify sex ratios of social insects and other forest-dwelling animals.  相似文献   

16.
稻秸还田对水稻土CH4排放有重要影响.本研究通过微宇宙厌氧培养,研究了两种水稻土[江西(JX)和广东雷州半岛(GD)]在稻秸(RS)添加条件下经相对较长时间的厌氧培养后产甲烷古菌及细菌菌群的响应.结果表明,不同RS添加量对JX水稻土产甲烷古菌群落结构有一定的影响,而对GD水稻土产甲烷古菌群落的影响不大. RS添加量与mcr A基因拷贝数之间存在显著正相关关系,JX水稻土的mcr A基因拷贝数变化对RS添加量的响应更敏感.相同RS添加条件下,JX水稻土mcr A基因拷贝数大于GD水稻土.相同稻秸量添加条件下两种水稻土的产甲烷古菌群落结构也有差异. JX水稻土共检测到的产甲烷古菌有Methanosarcinaceae、Methanocellaceae、Methanomicrobiaceae、Methanobacteriaceae以及未知菌群(494 bp). GD水稻土中仅有3大类产甲烷古菌,分别为Methanobacteriaceae、Methanosarcinaceae和Methanocellaceae.对2%RS处理培养第270 d的细菌菌群进行了测序,发现两种水稻土的细菌菌群明显不同,GD水稻土的细菌多样性高于JX水稻土,而其优势细菌数量(共有Longilinea、Acidobacteria/Gp6、Bellilinea及Thermosporothrix)低于JX水稻土(共有Bacillus、Desulfovirgula、Thermosporothrix、Acidobacteria/Gp1、Acidobacteria/Gp3及Ktedonobacter). RS作为底物促进产甲烷古菌的生长.不同类型的水稻土经相对较长时间的厌氧培养后其产甲烷古菌及细菌菌群结构也不同.  相似文献   

17.
Ichthyosaurs have been compared with the fast-swimming thunniform groups of marine vertebrates, tuna, lamnid sharks, and dolphins, based on similarity of shape of the body and locomotory organs. In addition to shape, high-tensile stiffness of the control surfaces has been shown to be essential in maximizing hydrodynamic efficiency in extant thunniform swimmers. To date, there has been no evidence of a stiffening support system for the dorsal fin and dorsal lobe of the caudal fin in ichthyosaurs, the sole stiffening structure of the ventral lobe being an extension of the vertebral column along its leading edge. Stenopterygius SMF 457 is arguably the best soft-tissue preserved ichthyosaur specimen known. Here, we examine soft-tissue preservation in this specimen in the control surfaces and provide the first evidence of a complex architecture of stiff fibers in the dorsal and caudal fins. We find by comparisons and by analogy that these fibers provided a remarkable mechanism for high tensile stiffness and efficiency of the locomotory organs virtually identical to that of the great white shark, Carcharodon carcharias. It is the first mechanostructural study of the control surfaces of a Jurassic ichthyosaur that adds essential evidence in support of the view that these forms were high-speed thunniform swimmers.  相似文献   

18.
The sensilla of insects are integumental units that play a role as sensory structures and are crucial for the perception of stimuli and for communication. In this study, we compared the antennal sensilla of females (workers and queens), males (haploid (n) and diploid (2n)), and queen-like males (QLMs, resulting from 2n males after juvenile hormone (JH) treatment) in the stingless bee Melipona quadrifasciata. Images of the dorsal antenna surfaces were acquired using a scanning electron microscope. As reported for other hymenopterans, this species exhibits a heterogeneous sensillar distribution along the antennae. Thirteen different types of sensilla were found in the antennae of M. quadrifasciata: trichodea (subtypes I to VI), chaetica (subtypes I and II), placodea, basiconica, ampullacea, coeloconica, and coelocapitula. Sensilla trichodea I were the most abundant, followed by sensilla placodea, which might function in olfactory perception. Sensilla basiconica, sensilla chaetica I, sensilla coeloconica, and sensilla ampullacea were found exclusively in females. In terms of the composition and size of the sensilla, the antennae of QLMs most closely resemble those of the 2n male, although QLMs exhibit a queen phenotype. This study represents the first comparative analysis of the antennal sensilla of M. quadrifasciata. The differences found in the type and amount of sensilla between the castes and sexes are discussed based on the presumed sensillary functions.  相似文献   

19.
河岸混合植物带处理受污染河水中试研究   总被引:21,自引:0,他引:21  
利用2种混合植物带(香根草+沉水植物、湿生植物+香蒲+芦苇)对受污染河水进行中试研究,并与无植物空白带进行了对比.结果表明,混合植物带对污染物的降解效果优于无植物空白带,其中香根草+沉水植物带效果最好,它在整个运行期间对COD、NH4+-N和TP的去除率分别为43.5%、71.1%和69.3%.对出水溶解氧及水温进行了考察,结果表明混合植物带水域中水的溶解氧比无植物带稳定,且在夏季水温低于无植物带水域的水温.说明在河道修复中植物带对平衡河岸带环境条件、改善河流局部小气候有重要作用.  相似文献   

20.
The Posidonienschiefer Formation (Toarcian) of Holzmaden, Baden-Württemberg in southwestern Germany has yielded several excellently preserved plesiosaurian specimens and received considerable research attention. The plesiosaurians found within these deposits are always significantly outnumbered by ichthyosaurs, and close examination of these rare specimens is crucial to a better understanding of the diversity and palaeoecology of Plesiosauria in this very peculiar ecosystem. The plesiosaurian specimen SMNS 51945 found in this area is a juvenile individual consisting of a partial, crushed skull and an exquisitely preserved post-cranial skeleton. Its anatomical characters seem to differ from the long-necked plesiosauroids Microcleidus brachypterygius and Seeleyosaurus guilelmiimperatoris that are the most abundant taxa within the plesiosaurian assemblage. The post-cranial skeleton preserves very likely soft tissues composed of buff-coloured and dark-coloured structures around the vertebral column and hindlimb of the animal. A network of buff-coloured fibres located posterior to the hindlimb most likely represents phosphatised collagen fibres as already found in some ichthyosaur specimens, confirming that wing area in plesiosaurians was much larger than that suggested by skeletal remains alone. The specimen also contains gastroliths (sand-sized grains mainly composed of quartz) in the stomach cavity suggesting the animal spent at least some of its time in shallow coastal waters, tens or hundreds of kilometres from the final place of burial.  相似文献   

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