First record of mosquitofish,Gambusia holbrooki,in Tasmania,Australia: Stock structure and reproductive biology     

John P. Keane  Francisco J. Neira 《新西兰海洋与淡水研究杂志》2013,47(5):857-867

The first population of mosquitofish, Gambusia holbrooki, was discovered in a wetland area of the upper Tamar Estuary, northern Tasmania, Australia, in November 2000. We report aspects of the structure and reproductive biology of this population, based on 1567 fish collected between August 2001 and January 2002. Females dominated most catches. Maximum lengths were 48.9 and 23.6 mm standard length (SL) for females and males, respectively. Growth of the over‐wintered cohort was evident from October, when temperatures reached >19°C; growth rates in the young‐of‐season cohort from length frequency plots were 0.38 mm/ day for females and 0.19 mm/day for males. Estimated SL at 50% maturity for females (25.0 mm) and males (17.4 mm) were attained within 7 weeks of birth. Developing embryos were present from mid October and offspring from mid November; average number of stage III embryos was 55.5 (3–144). Given their rapid reproductive turnover (c. 34‐day gestation period) and resilience to broad environmental conditions, it is likely that this exotic pest will spread to other Tasmanian localities, as it has already been discovered in areas near the wetlands since the completion of this study.  相似文献   

Nematode diversity in different microhabitats in a mangrove region     

Taciana K. Pinto  Melanie C. V. Austen  Richard M. Warwick  Paul J. Somerfield  André M. Esteves  Francisco J. V. Castro  Verônica G. Fonseca‐Genevois  Paulo J. P. Santos 《Marine Ecology》2013,34(3):257-268

Mangroves are highly productive environments that play important ecological and socioeconomic roles; however, they have been impacted to different degrees in most countries worldwide. The knowledge of which organisms inhabit this environment and their ecological interactions is the first step towards its conservation. The natural variability of environmental factors in mangroves provides numerous niches available to different species. Meiofauna have patchy patterns of distribution that are related to the availability of resources. Hence, meiofauna are expected to present a high diversity of different taxa occupying the different microhabitats offered by mangroves. This work aims to test the hypothesis that the assemblage structure of Nematoda varies significantly among mangrove microhabitats and to contribute knowledge on the meiofauna diversity in mangrove environments. This work was carried out in a mangrove region at Pernambuco state, Northeastern Brazil. Qualitative samples were collected in nine microhabitats which show different characteristics mainly in terms of presence of vegetation or another organism and sediment grain size. Univariate and multivariate analysis were applied to Nematoda genera abundance data. Our results demonstrate the existence of significant differences among microhabitats regarding nematode assemblage structure corroborating the hypothesis. Different Nematoda assemblages are present in at least seven microhabitats. These assemblages are composed of nematode genera with different trophic and morphological features, demonstrating a strong relationship between morphological diversity and ecological plasticity. Furthermore, this study also demonstrates the importance of the conservation of this ecosystem and its attributes.  相似文献   

Magnetic field modulated dust streams from Jupiter in interplanetary space     

Alberto Flandes  Harald Krüger  Douglas P. Hamilton  J. Francisco Valdés-Galicia  Linda Spilker  Rogelio Caballero 《Planetary and Space Science》2011,59(13):1455-1471

High speed dust streams emanating from near Jupiter were first discovered by the Ulysses spacecraft in 1992. Since then the phenomenon has been re-observed by Galileo in 1995, Cassini in 2000, and Ulysses in 2004. The dust grains are expected to be charged to a potential of , which is sufficient to allow the planet's magnetic field to accelerate them away from the planet, where they are subsequently influenced by the interplanetary magnetic field (IMF). A similar phenomenon was observed near Saturn by Cassini. Here, we report and analyze simultaneous dust, IMF and solar wind data for all dust streams from the two Ulysses Jupiter flybys. We find that compression regions (CRs) in the IMF – regions of enhanced magnetic field – precede most dust streams. Furthermore, the duration of a dust stream is roughly comparable with that of the precedent CR, and the occurrence of a dust stream and the occurrence of the previous CR are separated by a time interval that depends on the distance to Jupiter. The intensity of the dust streams and their precedent CRs are also correlated, but this correlation is only evident at distances from the planet no greater than 2 AU. Combining these observations, we argue that CRs strongly affect dust streams, probably by deflecting dust grain trajectories, so that they can reach the spacecraft and be detected by its dust sensor.  相似文献   

Alteration of platinum-group minerals and dispersion of platinum-group elements during progressive weathering of the Aguablanca Ni–Cu deposit, SW Spain     

Saioa Suárez  Hazel M. Prichard  Francisco Velasco  Peter C. Fisher  Iain McDonald 《Mineralium Deposita》2010,45(4):331-350

The distribution, mineralogy and mobility of the platinum-group elements (PGE) in the surface environment are poorly understood. This study of the lower, less altered and upper, more altered gossan, overlying the Aguablanca Ni–Cu-(PGE) magmatic deposit (Spain), has shown that the platinum-group minerals (PGM) are progressively oxidised and dispersed into iron oxides that form the gossan. A combination of the characterization of PGE in host PGM, using a scanning electron microscope, and measurement of PGE at lower concentrations in host iron oxides, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), has for the first time allowed the total distribution of the PGE within a gossan to be documented. This study has revealed a complete in situ alteration and dispersion sequence of the PGM including (1) breakdown of both the more stable Pt-arsenides, Pt/Pd-tellurides and the less stable bismuthotellurides, (2) formation of partially oxidised PGM, (3) development of a wide range of oxidised Pt- and Pd-bearing phases, (4) subsequent formation of Fe–PGE-oxides and PGE-hydroxides, (5) incorporation of PGE into ferruginous supergene products and lastly (6) concentration of PGE at the edges of veins and iron oxides. Dispersion of Pd is greater than for the other PGE with Pd being widely distributed throughout the iron oxides. This oxidising environment produced PGE-oxides rather than PGE-alloys, also commonly found in the surface environment, especially in placers. These results provide critical evidence for the stages of mineralogical change from PGE host mineralogy in magmatic ores to surface weathering producing PGE-oxides.  相似文献   

Acid drainage at the inactive Santa Lucia mine,western Cuba: Natural attenuation of arsenic,barium and lead,and geochemical behavior of rare earth elements     

Francisco Martín Romero  Rosa María Prol-Ledesma  Carles Canet  Laura Núñez Alvares  Ramón Pérez-Vázquez 《Applied Geochemistry》2010

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Using ichnofossils to characterize chert tools: A preliminary study from Southern Iberia     

Francisco J. Rodríguez‐Tovar  Antonio Morgado  Jos A. Lozano 《Geoarchaeology》2010,25(4):514-526

Characterizing raw material of stone tools used by Late Neolithic and Copper Age communities is important for interpreting access to available sources and establishing regional routes of distribution. Ichnological analysis may be used to help characterize lithic material and determine the source of artifacts. Here we report for the first time the existence of trace fossils in artifacts from the Late Neolithic and Copper Age of southern Spain. Ichnological analysis indicates a trace fossil assemblage consisting of relatively scarce small‐sized Chondrites and abundant Phycosiphon. A regional survey of natural outcrops and chert quarries indicates the presence of discrete trace fossils only in the samples from geological formations that are part of the Campo de Gibraltar Complex. Ichnological composition in these samples is similar to that discerned in the artifacts and suggests that this was the probable source of the chert used in tool manufacture. © 2010 Wiley Periodicals, Inc.  相似文献   

Lateglacial and Holocene palaeoenvironments at Sierra La Madera,northwestern Mexico: Sharp signals of Younger Dryas and North American monsoon     

Carlos Alberto Galaz-Samaniego  M. Cristina Peñalba  Francisco Abraham Paz-Moreno  Iván Rosario Espinoza-Encinas  Kinardo Flores-Castro  Rogelio Monreal  Carlos Lizárraga-Celaya 《第四纪科学杂志》2023,38(1):76-91

During the last glacial termination, the climate system experienced intense global variations whose causes and impacts are not fully defined, particularly for low latitudes. The northwestern Mexico Sky Islands present a climate-sensitive ideal setting to record palaeoecological and palaeoclimatic changes due to their physiographic complexity and location in the ecotone between temperate and tropical ecosystems. High-resolution pollen analysis and a detailed sedimentological study were conducted at the Ciénega Tonibabi tropical thorn scrub site. The 15 540–0 cal a bp nearly continuous record shows that the North Atlantic Ocean did have a cold and humid climatic influence during the glacial stages of the end of the Pleistocene, including a sharp pulse during the Younger Dryas. However, a shift to the Pacific Ocean influence occurred during the Holocene, which led to the development of the El Niño conditions prevailing today. Colder and warmer phases follow one another with higher or lower winter precipitation, including a sharp Bølling–Allerød and development and intensification of the North American monsoon. They are reflected in hydrological changes as well as in the advances, retreats and intermingling of coniferous forests and tropical thorn scrub.  相似文献