A long-snouted predatory dinosaur from africa and the evolution of spinosaurids     

PC Sereno  AL Beck  DB Dutheil  B Gado  HCE Larsson  GH Lyon  JD Marcot  OWM Rauhut  RW Sadleir  CA Sidor  DD Varricchio  GP Wilson  JA Wilson 《Science (New York, N.Y.)》1998,282(5392):1298-1302

Fossils discovered in Lower Cretaceous (Aptian) rocks in the Tenere Desert of central Niger provide new information about spinosaurids, a peculiar group of piscivorous theropod dinosaurs. The remains, which represent a new genus and species, reveal the extreme elongation and transverse compression of the spinosaurid snout. The postcranial bones include blade-shaped vertebral spines that form a low sail over the hips. Phylogenetic analysis suggests that the enlarged thumb claw and robust forelimb evolved during the Jurassic, before the elongated snout and other fish-eating adaptations in the skull. The close phylogenetic relationship between the new African spinosaurid and Baryonyx from Europe provides evidence of dispersal across the Tethys seaway during the Early Cretaceous.  相似文献   

Possible functions of the octavolateralis system in fish schooling     

Matz Larsson 《Fish and Fisheries》2009,10(3):344-353

The development of the octavolateralis system in fish ancestors created the phenomenon of sensory reafference associated with the fish's own locomotion. Particularly in fish species living and moving in groups, there is a potential to produce complex pressure waves and other water movements interfering with the octavolateralis perception of critical environmental signals. The hypothesis presented is that the development of the octavolateralis system may have initiated, or been a factor in, the evolutionary development of synchronized group locomotion, eventually leading to schooling behaviour. Theoretical models suggest that schooling may be related to a reduction in masking of environmental signals, as well as to survival mechanisms, e.g. confusion of the lateral line and electro-sensory systems of predators by overlapping pressure waves and overlapping electrical fields. The combined effects of reduced masking and predator confusion may help explain why schooling became an evolutionary success. Including pressure waves and other water movements in the model of join, stay or leave decisions might shed some light on fish shoal assortment. A model encompassing the complex effects of synchronized group locomotion on octavolateralis and electro-sensory perception of both prey and predator fish might increase the understanding of schooling behaviour.  相似文献   

Genetic differentiation between and within ecotypes of pike (Esox lucius) in the Baltic Sea     

Oscar Nordahl  Per Koch‐Schmidt  Johanna Sunde  Yeerin Y&#x;ld&#x;r&#x;m  Petter Tibblin  Anders Forsman  Per Larsson 《水产资源保护:海洋与淡水生态系统》2019,29(11):1923-1935

The long-term effects of catchment liming and reduced sulphur deposition on forest soils and runoff chemistry in southwest Sweden     

Stefan Löfgren  Neil Cory  Therese Zetterberg  Per-Erik Larsson  Veronika Kronnäs 《Forest Ecology and Management》2009

Whole catchment liming or forest liming has been proposed and implemented as a countermeasure to the effects of elevated sulphur deposition. Since the end of the 1980s the Swedish Forest Agency has undertaken experimental forest liming experiments in selected catchments in southern Sweden. These studies were with low doses (3 tonnes ha⁻¹) of lime (CaCO₃) and dolomite (CaMg(CO₃)₂). Data from both soil samples and stream water samples have been collected for the 16 years following treatment. The stream data has been complemented with data from untreated catchments, from the Swedish monitoring stream network. Significant differences due to treatment were seen for Ca, cation exchange capacity (CEC) and base saturation (BS) in the humus layer, none of these variables showed a statistically significant change in the mineral soil due to treatment alone. Soil samples from both the treated and untreated sites showed temporal changes in both the humus layer and the mineral soils with increases in pH, Ca and CEC and decreases in BS and Al which were independent of treatment. A combination of treatment and time, gave significant changes in BS and TA down to 10 cm in the mineral soil. In the stream water samples no statistically significant differences were observed between treated and untreated sites. Regardless of treatment, the streams exhibited a general pattern of declining concentrations of SO₄, Ca, sum of base cations (BC) and increasing acid neutralizing capacity (ANC). In summary, the application of a low dose of lime (3 tonnes ha⁻¹) did not result in significant changes in surface water chemistry in the study catchments and changes in soil chemistry were mainly restricted to the humus layer during the 16 years following treatment. The natural recovery, as a result of reductions in sulphur deposition, dominated the effects and was clearly seen in both the treated and untreated study sites. MAGIC simulations indicate that this recovery will continue in the coming decades.  相似文献   

INFLUENCE OF NITROGEN SUPPLY ON CADMIUM ACCUMULATION IN POTATO TUBERS     

E. Helene Larsson Jönsson  Håkan Asp 《Journal of plant nutrition》2013,36(3):345-360

The effect of different levels and forms of nitrogen (N) fertilizer on cadmium (Cd) concentrations in potato (Solanum tuberosum L.) tubers, a large component of the northern European diet, was investigated with the aim of decreasing the Cd content. A high and a low Cd-accumulating cultivar were used in two field trials and a pot experiment. The N fertilizers tested were balanced N- phosphorus (P)- potassium (K) 11-5-18 + micronutrients, alkaline calcium nitrate and acidic ammonium sulfate at levels of 60, 160, and 240 kg N ha^?1 at planting or (for the higher N doses) split between two or three occasions. The Cd concentration in tubers of both cultivars decreased when increasing the N fertilizer from 60 to 160 or 240 kg N ha^?1, indicating that Cd uptake and translocation are not positively correlated to the growth rate of the potato plant. A strong positive linear correlation was found between the Cd concentration in leaves at 77 days after planting and the Cd concentration in tubers at harvest, irrespective of N treatment, although the Cd concentration was three-fold higher in the leaves. The genetic variation in leaf and tuber Cd accumulation was consistent, regardless of the form of N fertilizer used. Ammonium sulfate decreased soil pH and increased tuber Cd concentration in both cultivars compared with NPK fertilizer, possibly due to increased amounts of plant-available Cd arising from the pH decrease after ammonium sulfate application. The tuber Cd concentration in the low Cd-accumulating cultivar increased when fertilized with calcium nitrate, an effect attributed to Cd availability being influenced by the increased Ca²⁺ concentration.  相似文献   

Studies of Enteric Pathogens and γ-Globulin Levels of Neonatal Calves in Sweden     

S. Viring  S.-O. Olsson  S. Alenius  U. Emanuelsson  S.-O. Jacobsson  B. Larsson  N. Linde  A. Uggla 《Acta veterinaria Scandinavica》1993,34(3):271

Viring, S., S.-O. Olsson, S. Alenius, U. Emanuelsson, S.-O. Jacobsson, B. Larsson, N. Linde and A. Uggla: Studies of enteric pathogens and γ-globulin levels of neonatal calves in Sweden. Acta vet. scand. 1993, 34, 271-279.– Faecal and blood samples were taken from 10-30% of calves, 36 hours to 14 days old, in 47 dairy herds in different regions of Sweden from September 1987 to October 1988 (Olsson et al 1993). Faecal samples from 279 calves were analysed for the presence of Escherichia coli (K99⁺), rotavirus and Cryptosporidium sp. Twenty (7.2%) of these samples were from diarrhoeic calves. An ELISA was developed and used for the rotavirus analysis. E. coli K99⁺ was detected in 11.5%, Cryptosporidium sp. in 6.1% and rotavirus in 5.4% of the faecal samples. The presence of rotavirus alone and the combination rotavirus and E. coli (K99⁺) was found to be associated with diarrhoea (p<0.001 and p<0.01 respectively).Blood samples from 327 calves were analysed for the level of total protein and γ-globulin. In 43 of these samples (13%) γ-globulin did not separate from the ß₂-region by electrophoresis. The mean total protein concentration was 53.6 g/1 in calves free from diarrhoea. The mean γ-globulin concentration, adjusted to 7 days age was 5.9 g/1. The 20 diarrhoeic calves had lower levels of both total protein and γ-globulin, compared with calves without diarrhoea, but the difference was not significant. One litre more of colostrum at the first feed increased the level of total protein of the calves’ sera by 1.4 g/1 (p = 0.05). Calves born between May and September had a 2.0 g/1 higher (p<0.001) serum concentration of γ-globulin than calves born between October and April.  相似文献   

Remote straying of salmon (Salmo salar L.) from the Swedish west coast and possible effects on sea ranching operations     

Per-Olov Larsson 《Aquaculture (Amsterdam, Netherlands)》1984,38(1):83-87

Some 6500 recaptures of salmon tagged as smolts on the Swedish west coast in 1966–1980 were reviewed for remote strayers. Only 27 (0.43%) were found, meaning no risk for the profitability of sea ranching activities. Along the Swedish west coast at least 450 kg salmon per 1000 released smolts can be expected to be caught by Swedish commercial fishermen, which makes public sea ranching highly profitable there.  相似文献   

Embryonic mortality in heifers after artificial insemination and embryo transfer: differences between virgin and repeat breeder heifers     

H Gustafsson  K Larsson 《Research in veterinary science》1985,39(3):271-274

Embryos were collected from repeat breeder heifers and virgin heifers seven days after insemination, classified and transferred to the uterine horn contralateral to the corpus luteum of synchronised inseminated recipients. Altogether 35 transfers were performed, all reciprocally between repeat breeder heifers and virgin heifers. The recipients were slaughtered either 16 to 17 days or 32 to 35 days after insemination. The survival rate of the native embryos was lower among the repeat breeder heifers than among the virgin heifers both at 16 to 17 days (six of nine vs six of six) and at 32 to 35 days (three of 10 vs seven of 10) after insemination. A higher proportion of embryos transferred from repeat breeder heifers to virgin heifers than from virgin heifers to repeat breeder heifers survived to days 16 to 17 (five of six vs two of nine), while the same proportion of embryos survived to days 32 to 35 (two of 10) in both heifer categories. The results suggest that the uterine environment in repeat breeder heifers is suboptimal for the support of normal embryonic development.  相似文献   

A new thawing fluid for deep frozen boar spermatozoa.     

K Larsson  S Einarsson 《Acta veterinaria Scandinavica》1975,16(1):143-145

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Electrocardiographic parameters of captive lions (Panthera leo) and tigers (Panthera tigris) immobilized with ketamine plus xylazine     

Maria Helena M A Larsson  Fernanda M Coelho  Valéria M C Oliveira  Fernanda L Yamaki  Guilherme G Pereira  Elaine C Soares  José Daniel L Fedullo  Roberto C Pereira  F H Ito 《Journal of zoo and wildlife medicine》2008,39(3):314-319

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