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In cold-temperate climates, overwintering aquatic ranid frogs must survive prolonged periods of low temperature, often accompanied by low levels of dissolved oxygen. They must do so with the energy stores acquired prior to the onset of winter. Overwintering mortality is a significant factor in their life history, occasionally reaching 100% due to freezing and/or anoxia. Many species of northern ranid frogs overwinter in the tadpole stage, which increases survival during hypoxic episodes relative to adults, as well as allowing for larger sizes at metamorphosis. At temperatures below 5 degrees C, submerged ranid frogs are capable of acquiring adequate oxygen via cutaneous gas exchange over a wide range of ambient oxygen partial pressures (PO(2)), and possess numerous physiological and behavioural mechanisms that allow them to maintain normal rates of oxygen uptake across the skin at a relatively low PO(2). At levels of oxygen near and below the critical PO(2) that allows for aerobic metabolism, frogs must adopt biochemical mechanisms that act to minimise oxygen utilisation and assist in maintaining an aerobic state to survive overwintering. These mechanisms include alterations in mitochondrial metabolism and affinity, changes in membrane permeability, alterations in water balance, and reduction in cellular electrochemical gradients, all of which lead to an overall reduction in whole-animal metabolism. Winter energetic requirements are fueled by the energy stores in liver, muscle, and fat depots, which are likely to be sufficient when the water is cold and well oxygenated. However, under hypoxic conditions fat stores cannot be utilised efficiently and glycogen stores are used up rapidly due to recruitment of anaerobiosis. Since ranid frogs have minimal tolerance to anoxia, it is untenable to suggest that they spend a significant portion of the winter buried in anoxic mud, but instead utilise a suite of behavioural and physiological mechanisms geared to optimal survival in cold, hypoxic conditions.  相似文献   

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Although behavioral studies have been conducted at zoos and aquaria for years, documentation concerning the effectiveness of environmental enrichment has dealt primarily with terrestrial animals and marine mammals. Few enrichment studies have been conducted on reptiles. For this study, behavioral observations were made on four captive sea turtles (three loggerhead, Caretta caretta, and one blind green, Chelonia mydas) with enrichment present and absent. Enrichment devices were modified for the special needs of the blind turtle. Behaviors were classified as Resting, Pattern Swimming, Random Swimming, Focused Behavior, Aggression, Hiding, Orientation, and Noncategorized Behavior. It was hypothesized that, when enrichment was present, a decrease in Resting and stereotypic Pattern Swimming would be seen along with an increase in Random Swimming and Focused Behavior. It was found that, when no enrichment devices were present, 77% of the turtles' time was spent in Resting and Pattern Swimming. When enrichment devices were provided, 88% of their time was spent in Random Swimming and Focused Behavior with only 8% spent in Pattern Swimming and Resting. Statistically, there were significant increases in Random Swimming (three of the four turtles) and Focused Behavior (4/4) and significant decreases in Resting (3/4) and Pattern Swimming (3/4) when enrichment devices were present. These results suggest that environmental enrichment is as effective with marine reptiles as has been found with other animals and should be encouraged for all captive sea turtles. Zoo Biol 26:407–416, 2007. © 2007 Wiley‐Liss, Inc.  相似文献   

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Global warming could threaten over 400 species with temperature-dependent sex determination (TSD) worldwide, including all species of sea turtle. During embryonic development, rising temperatures might lead to the overproduction of one sex and, in turn, could bias populations’ sex ratios to an extent that threatens their persistence. If climate change predictions are correct, and biased sex ratios reduce population viability, species with TSD may go rapidly extinct unless adaptive mechanisms, whether behavioural, physiological or molecular, exist to buffer these temperature-driven effects. Here, we summarize the discovery of the TSD phenomenon and its still elusive evolutionary significance. We then review the molecular pathways underpinning TSD in model species, along with the hormonal mechanisms that interact with temperatures to determine an individual's sex. To illustrate evolutionary mechanisms that can affect sex determination, we focus on sea turtle biology, discussing both the adaptive potential of this threatened TSD taxon, and the risks associated with conservation mismanagement.  相似文献   

5.
吴平  周开亚  杨群 《动物学报》1999,45(3):260-267
对亚洲产淡水和陆生龟鳖4科23个种进行了DNA序列水平的分子系统学研究,用PCR技术扩增约400bp的线粒体12SrRNA基因片段进行了序列分析,合并从GenBank中检索到的其它龟鳖类的序列数据,在基于二级结构的对位排列基因上用邻结法地系统发生研究。结果表明,潮龟科与陆龟简拼要缘关系比龟科与陆龟科的近;支持将平胸龟属归为鳄龟上属;潮产是并系起源,从12SrRNA基因序列得到的系统发生关系不支持根  相似文献   

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Electroretinographic recordings were made from hatchling loggerhead and leatherback sea turtle eyecup preparations to generate dark-adapted spectral sensitivity curves. Both species were maximally sensitive to wavelengths between 500 and 540 nm, with a secondary peak near 380 nm. The spectral sensitivity curve for leatherbacks was attenuated at the long wavelength end of the spectrum relative to that of the loggerheads. This difference may reflect adaptations to lighting available at the relatively shallow (loggerhead) versus deeper (leatherback) sites where each species forages. The broad spectrum of wavelengths detected by both species (near UV to yellow–orange) indicates that vision is likely mediated by more than one photopigment, potentially rendering these turtles capable of color vision.  相似文献   

7.
东海浙江海域分布着5种海龟, 分别为棱皮龟(Dermochelys coriacea)、绿海龟(Chelonia mydas)、红海龟(Caretta caretta)、玳瑁(Eretmochelys imbricata)和太平洋丽龟(Lepidochelys olivacea), 均被列为国家一级重点保护野生动物。目前, 针对浙江海域的海龟种群现状调查较为缺乏。为此, 本研究通过搜集互联网平台上1981年4月1日至2022年12月31日的浙江海域海龟发现记录, 尤其是整合了短视频平台渔民上传的影像记录这一新颖来源的数据, 对浙江海域海龟种群现状进行评估。共搜集到互联网上浙江海域海龟报道109笔, 共计234只, 其中红海龟个体数占79.1%, 绿海龟占9.4%, 棱皮龟占6.0%, 太平洋丽龟占4.3%, 玳瑁占1.3%。5种海龟所有个体均为成体。同时, 通过短视频平台获取的记录案例数最多, 占总记录案例的66.1%, 占近10年所有记录案例的93.6%。本研究结果表明浙江海域红海龟数量最多, 绿海龟、棱皮龟和太平洋丽龟相对较少, 玳瑁最少。同时, 短视频数据从2020年开始急剧增多, 这提示短视频数据可能是未来海洋爬行动物种群数量调查的重要数据源。  相似文献   

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Survival of the sea louse Lepeophtheirus salmonis on juvenile Pacific salmon Oncorhynchus gorbuscha and Oncorhynchus keta was examined with respect to salinity (0, 7, 14, 21 and 28). Rapid mortality was observed in fresh water (0) but motile stage sea lice tolerated higher salinities (7, 14, 21 and 28) for up to 7 days. These findings suggest that salinities juvenile Pacific salmon typically encounter during early marine residence have little affect on motile sea louse survival.  相似文献   

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Among ladybirds, diapause has evidently been most studied in Coccinella septempunctata L. adults. Coccinella septempunctata (C‐7), the seven spot, has attracted attention both in Europe and the USA for being heterogeneous as to the induction of diapause. A polyphenic character of diapause is a prominent feature in C. septempunctata and this phenomenon generally and often generates voltinism heterogeneity within populations. A greater part of the C‐7 population shows an obligatory univoltine cycle, whereas a smaller proportion is facultatively polyvoltine. Coccinella s. bruckii in Japan is bivoltine, in which the first generation of adults aestivate while the second generation hibernates. This paper reviews this heterodynamic cycle and its importance in the life history of C‐7, as reported from different regions of the world. Heterogeneous voltinism and diapause smooth the progress of a portion of C‐7 populations to take benefit of aphids well into late summer and autumn. Understanding such variation and plasticity in the life history of this species can help in organizing proper biological control attempts using it as a biocontrol agent.  相似文献   

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小菜蛾在温带地区越冬研究进展   总被引:2,自引:0,他引:2       下载免费PDF全文
马春森  马罡  杨和平 《生态学报》2010,30(13):3628-3636
小菜蛾是世界性重要害虫。在热带和亚热带地区冬季的十字花科植物上能正常发育繁殖,可见到各种虫态。但在温带冬季十字花科植物不能生长的地区,小菜蛾的越冬成为一个重要生态学问题。综述了亚洲、北美洲和欧洲小菜蛾越冬的研究进展。小菜蛾在日本的北海道、本州岛的北陆和东北大部分地区不能越冬,越冬北限相当于冬季积雪覆盖时间为60d的区域;在中国,小菜蛾不能在寒冷的东北地区越冬,在长江中下游以南地区冬季可见各虫态,但越冬北限尚不清楚;小菜蛾在冬天气候温和的韩国以及澳大利亚东南部继续发生;北美洲的加拿大西部和安大略地区大量的试验证明小菜蛾不能成功越冬,在美国南部小菜蛾冬季可正常发生,北部小菜蛾的越冬尚未见系统研究报道,但确认春季从南部运输的受小菜蛾感染的甘蓝等种苗是美国北部的重要虫源。小菜蛾在欧洲各地越冬的系统研究未见报道,没有证据表明在英国小菜蛾会发生有显著意义的越冬。目前小菜蛾越冬研究主要采用冬季直接试验观察和基于耐寒性试验的越冬预测两种方法。冬季直接试验观察法包括:(1)利用人工饲养的小菜蛾在田间各种潜在的越冬场所的越冬试验;(2)在秋播、野生或残留的十字花科植物上进行冬季种群的系统抽样调查;(3)越冬前后在前茬为十字花科植物的田块广泛搜寻普查小菜蛾的存活个体。基于耐寒性试验的越冬预测法:在获取小菜蛾越冬场所温度的基础上设计低温处理模式,试验低温处理后小菜蛾的存活率及后续发育和生殖。将试验数据和各地气温或小气候相结合,对小菜蛾在的越冬可能性进行推断。  相似文献   

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Freshwater turtle hatchlings primarily use visual cues for orientation while dispersing from nests; however, hatchlings rapidly develop a relationship between a sun or geomagnetic compass and a dispersal target that allows them to maintain an established direction of movement when target habitats are not visible. We examined dispersal patterns of hatchling snapping turtles (Chelydra serpentina) and Blanding's turtles (Emydoidea blandingii) dispersing in large arenas in a mowed field and in dense corn. The dispersal of three categories of hatchlings were examined: (1) naïve individuals (no previous dispersal experience), (2) arena‐experienced (limited dispersal experience in arenas in natural habitat), and (3) natural‐experienced hatchling Blanding's turtles (captured after extensive experience dispersing W in natural habitats toward wetlands). Experienced hatchlings were assigned to treatments consisting of having a magnet or a non‐magnetic aluminum sham or nothing glued to their anterior carapace before release in the corn arena. Dispersal patterns of naïve hatchlings of both species were strongly directional in the field arena with visible target horizons and primarily random in the corn arena where typical target horizons were blocked. When released in corn, dispersal patterns were similar for arena‐experienced hatchlings with magnets or shams attached and differed from their prior dispersal headings in the field arena as naïve hatchlings. Natural‐experienced hatchling Blanding's turtles with and without magnets were able to accurately maintain their prior headings to the WNW while dispersing in the field or corn arenas (i.e., the presence of a magnet did not disrupt their ability to maintain their prior heading). Based on the assumption that no other type of compass exists in hatchlings, we conclude that they were not using a geomagnetic compass, but by default were using sun compass orientation to maintain dispersal headings in dense corn where no typical target habitats were visible.  相似文献   

12.
A declining population of the freshwater turtle Mauremys rivulata (Chelonia, Geoemydidae) living in a human-impacted area along the Strymon River, just upstream from Kerkini Lake (Prefecture of Serres, northern Greece), was investigated by capture–recapture and radio-tracking. Fyke nets placed along the river and in ponds lying on the riparian lowland gave about 2000 catches in 6 years, permitting us to assess major inter-habitat movements during ontogenesis and throughout the seasons. Annual intensive radio-tracking of 15 females and 10 males gave finer details of movement patterns between different river-wetland habitats. Younger specimens, including yearlings, inhabited the ponds almost exclusively, whereas the adult population shifted seasonally from the ponds during the mating season to a marsh area lying on the opposite side of the river for aestivation and overwintering. The river served mainly as a corridor for transit between the two habitats. Moreover, longitudinal movements along the river were observed, particularly in the males, which probably allow dispersal and gene flow between subpopulations living in the area. One major threat to the viability of M. rivulata in the study area is the diversion of water for irrigation during the summer, drying up the Strymon completely, which reduces the water level in the ponds. Livestock crossing the area for grazing and watering in the ponds is also of impact, as turtles in the ponds are trampled on and nests are disturbed.  相似文献   

13.
龟脑的强抗氧化功能可能与龟类的长寿相关   总被引:6,自引:0,他引:6  
龟脑防御缺氧和再供氧伤害的过程可能与龟类的长寿相关,研究表明龟体内有特别的保护各种离子通道和受体功能的机制,龟脑在缺氧条件下,可以抑制兴奋性神经递质的毒害作用,其机制也许是通过维持多巴胺和谷氨酸的释放与再吸收之间的平衡来实现的,此外,它通过胞外的γ-氨基丁酸(GABA)浓度的持续升高和其受体密度的相应增加而抵抗活性氧基团的生成,并且免受其伤害.这样的机制可能在缺氧和再供氧的 状态下被选择性的激活,因此龟类可作为研究衰老和抗衰老生理机制的动物模型。  相似文献   

14.
Sea turtles undertake long migrations in the open ocean, during which they rely at least partly on magnetic cues for navigation. In principle, sensitivity to polarized light might be an additional sensory capability that aids navigation. Furthermore, polarization sensitivity has been linked to ultraviolet (UV) light perception which is present in sea turtles. Here, we tested the ability of hatchling loggerheads (Caretta caretta) to maintain a swimming direction in the presence of broad-spectrum polarized light. At the start of each trial, hatchling turtles, with their magnetic sense temporarily impaired by magnets, successfully established a steady course towards a light-emitting diode (LED) light source while the polarized light field was present. When the LED was removed, however, hatchlings failed to maintain a steady swimming direction, even though the polarized light field remained. Our results have failed to provide evidence for polarized light perception in young sea turtles and suggest that alternative cues guide the initial migration offshore.  相似文献   

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A wild population of the European pond turtle, Emys orbicularis (L.), has been studied using visual inspection and radiotracking of tagged animals inhabiting a pond inside the Monte Rufeno Natural Reserve, a wooded hilly area in central Italy. A sudden decrease in the number of the females inhabiting the pond was observed during a 1-week period, in June 1994. Radiotracking of seven females leaving the pond revealed the occurrence of overland movements toward two distinct areas, for nesting at 150 and 600 m from the home pond. Details on the nesting migrations of this species are given for the first time in the present paper. Laying was also observed: seven nests were identified and two of them were enclosed to prevent predation. Three out of five non-protected nests were destroyed within a few days of laying. Incubation time (83–89 days) was determined on a clutch protected from predation.  相似文献   

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Communal nesting is a behaviour that involves multiple females laying eggs in the same nest or nesting site. This behaviour may be a consequence of a shortage of preferable nest sites (constraint hypothesis) or an adaptation generated by fitness benefits associated with egg aggregation (adaptive hypothesis). Experimental tests of these hypotheses require information about maternal nest site choice and its fitness consequences. To address these, we studied a lizard (brown anole; Anolis sagrei) that produces single-egg clutches, but often aggregates eggs in nest sites. In a lab study, females were given the option of nesting in (a) soil previously used as nest substrate vs. fresh soil and (b) soil with eggshells vs. without eggshells. We also experimentally examined the effects of egg aggregation by incubating eggs singly, in groups of four, and in groups of nine. We recorded egg surface temperature, water uptake, and hatchling morphology. Females were more likely to nest in pots with used soil and with eggshells than in pots with fresh soil or without eggshells. We observed no effects of egg aggregation on egg survival, egg temperature, or most measures of hatchling morphology. However, singly-incubated eggs absorbed more water than eggs incubated in the four and nine egg aggregations and this resulted in offspring with greater body condition (i.e. heavier for their length) at hatching. The behavioural experiment demonstrates that females actively choose nest sites that have been used previously (as expected under the adaptive hypothesis), but the egg-aggregation experiment shows no benefits to offspring based on the variables measured. Thus, results of the behaviour study support the adaptive hypothesis; however, results from our egg-incubation study do not. Likely, the adaptive and constraint hypotheses are not mutually exclusive, and a diversity of factors influence the evolution of communal nesting behaviour.  相似文献   

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The Convention on International Trade of Endangered Species (CITES) is the primary mechanism for controlling international wildlife trade and preventing overexploitation, but measuring its efficacy is difficult, which complicates management efforts. We examined the effects of CITES listings on the trade of freshwater turtles from the US and compared spatiotemporal trends and dynamics of trade across 16 genera using 20 years of export data, triangulated with mixed qualitative data. For each CITES-listed genus, we analyzed the average changes, immediate changes, and changes in trends of export volumes and spatial diversity of trade. Boom-and-bust trends of exports for different taxa were driven by several factors, including CITES listings, but CITES had mixed effects on export volumes for both Appendix II and III species while the diversity of spatial trade networks consistently declined for CITES and non-CITES listed genera. These results point to differences in demand and species' availability from captive breeders, farms, or wild harvest which are important to consider in future listing decisions. However, a lack of reliable data on the source of turtles limited our ability to understand these drivers as well as the efficacy of CITES listings in preventing overexploitation.  相似文献   

19.
Recovery of sea turtle populations requires addressing: multiple sources of mortality; nonmarket, diffuse benefits with costs localized on the poor; and a transboundary resource with incomplete jurisprudence, markets, and institutions. Holistic recovery strategies include: beach conservation protecting nesting females, their eggs, and critical breeding habitat to maximize hatchling production; enhanced at-sea survival of turtles on the high seas and in commercial coastal fisheries; and reduced artisanal coastal fisheries mortality of turtles. The traditional approach of focusing long-term sustained conservation efforts on the nesting beaches has by itself led to increases in several sea turtle populations. However, current conservation is inadequate to reverse declines in other cases such as the critically endangered leatherback populations in the Pacific. This article discusses policy instruments comprising a holistic recovery strategy that reconciles fishing with biodiversity conservation.  相似文献   

20.
Arsenic in the liver, kidney and muscle of three species of sea turtles, e.g., green turtles (Chelonia mydas), loggerhead turtles (Caretta caretta) and hawksbill turtles (Eretmochelys imbricata), were determined using HG-AAS, followed by arsenic speciation analysis using HPLC-ICP-MS. The order of arsenic concentration in tissues was muscle > kidney > liver. Unexpectedly, the arsenic concentrations in the hawksbill turtles feeding mainly on sponges were higher than the two other turtles primarily eating algae and mollusk which accumulate a large amount of arsenic. Especially, the muscles of the hawksbill turtles contained remarkably high arsenic concentrations averaging 153 mg kg–1 dry weight with the range of 23.1–205 mg kg–1 (n=4), even in comparison with the data from other organisms. The arsenic concentrations in the tissues of the green turtles were significantly decreased with standard carapace length as an indicator of growth. In arsenic compounds, arsenobetaine was mostly detected in the tissues of all the turtles. Besides arsenobetaine, a small amount of dimethylarsinic acid was also observed in the hawksbill turtles.  相似文献   

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