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221.
Venkatesan G. Subramani T. Karunanidhi D. Sathya U. Li Peiyue 《Environmental science and pollution research international》2021,28(15):18539-18551
Environmental Science and Pollution Research - In the present study, impact of precipitation disparity on groundwater level fluctuation was carried out in Vellore district, Tamil Nadu, India, using... 相似文献
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Conservation Genetics of the Endangered Isle Royale Gray Wolf 总被引:5,自引:0,他引:5
R. K. WAYNE N. LEHMAN D. GIRMAN P.J.P. GOGAN D. A. GILBERT K. HANSEN R. O. PETERSON U. S. SEAL A. EISENHAWER L. D. MECH R.J. KRUMENAKER 《Conservation biology》1991,5(1):41-51
Abstract. The small group of wolves on Isle Royale has been studied for over three decades as a model of the relationship between large carnivores and their prey. During the last ten years the population declined from 50 individuals to as few as 12 individuals. The causes of this decline may be food shortages, disease, or reduced genetic variability. We address the issues of genetic variability and relationships of Isle Royale wolves using allozyme electrophoresis, mtDNA restriction-site analysis, and multilocus hypervariable minisatellite DNA analysis (genetic fingerprinting). Our results indicate that approximately 50% of the allozyme heterozygosity has been lost in the island population, a decline similar to that expected if no immigration had occurred from the mainland. The genetic fingerprinting data indicate that the seven sampled Isle Royale wolves are as similar as captive populations of siblings. Surprisingly, the Isle Royale wolves have an mDNA genotype that is very rare on the mainland, being found in only one of 144 mainland wolves ThFF suggests that the remaining Isle Royale wolves areprobably derived from a single female founder 相似文献
224.
Hydrolytic enzyme activities were determined in tissue extracts of the two North Sea ctenophores Pleurobrachia pileus and Beroe gracilis. The following activities were measured in field samples and characterized according to their mean specific activities and their pH optima: protease, aminopeptidase, amylase, N-acetylglucosaminidase, -glucosidase, chitinase, carboxylesterase, phosphatase. Many of the enzyme activities are correlated, indicating their control by the same factors (i.e. nutritional conditions). Differences found between the phosphatase activities and the apparent lack of the chitinolytic system in B. gracilis reflect the differences in body composition and food specialization in both ctenophores, respectively. The low amylase and -glucosidase activities in both ctenophores agree with the low carbohydrate content of their prey. In spite of high carboxylesterase activities, no lipolytic activity was detected in either of the ctenophores. In a laboratory feeding experiment with P. pileus, the enzyme activities increased but did not reach the activities found in the field samples. In B. gracilis, seasonal variations of some enzyme activities are discussed in relation to the seasonal abundance of its prey, P. pileus. 相似文献
225.
Change in a bacterial population during the process of degradation of a phytoplankton bloom was investigated at Lake Hamana, Japan in June 1981. The predominant phytoplankton were Prorocentrum micans Ehrenberg and P. triestinum Schiller. While most phytoplankton cells were living and moving actively, most bacteria were those in a free-living state (free-living bacteria) and the number of bacteria associated with particulate materials (attached bacteria) was less than a few percent of the total bacterial number. As the decline process proceeded, the number of free-living bacteria remained almost constant or decreased slightly; on the other hand, the number of attached bacteria increased gradually and reached about 40% of the total bacterial number. These results indicate that some of the free-living bacteria become attached to particulate organic matter and grow on the surface of the particles. 相似文献
226.
The evaporation of organic contaminants of different volatility from a porous sandfill was investigated in laboratory experiments. A significant decrease of the evaporation rate was observed under conditions of compacted fill, at high concentrations of the low-volatile component. This can be explained by the formation of a layer with a low mass fraction of the solvent near the gas-phase boundary of the contaminated zone. The term ?self-encapsulation” is suggested for this phenomenon. Theoretical considerations show that this effect can occur if a volatile component evaporates from a mixture with a substance of low volatility and if the total mass transfer resistance is mainly within the contaminant phase. The formation of a solid layer at the surface can enhance this encapsulating effect for the remaining volatile material. A similar behaviour can be expected for contaminants consisting of components of different solubility which get in contact with flowing water. 相似文献
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Pumping rates in the soft clamMya arenaria, collected in June 1987 in the Great Belt, Denmark, were determined as rates at which clams cleared suspensions of algae,Dunaliella marina. The frictional resistance of the siphons to water flow was estimated by studying the effect of excision of the siphons at the base on the rate of water pumping. The frictional resistance was also calculated from the Poiseuille equation. Excision of the siphons had no measurable effect on the pumping rate, and calculations indicated pressure losses ranging between 0.3 to 1.2 mm H2O. This is consistent with the conception that the capacity of filter feeding bivalves to process large amounts of water depends upon a low resistance to water flow in the siphons. 相似文献
229.
In a Baltic herring (Clupea harengus membras L.) spawning ground study, carried out in summer 1982 in the northern Baltic proper, spawning herring were encountered on two line transects on June 14. The spawning behaviour of minor groups as well as of a large school was studied in situ by four divers for approximately three hours. No behavioural differences or systematic coordinated behaviour between the sexes could be detected. Most of the spawning took place in a limited depth interval, 0.5 to 4 m, and Ceramium tenuicorne was the substrate most used. 相似文献
230.
Microscope video graphs of particle paths near one-filament-thick mussel gill preparations, stimulated with a nerve transmitter (10–6
M serotonin which restores normal ciliary activity), were used to disclose the capture of 6 m algal cells. Suspended algal cells carried with the water were stopped for a while at the entrance to the interfilament gap by the action of the latero-frontal cirri (Ifc), and transferred to the frontal side of the filament to be transported towards the marginal food groove. The event of transfer took place during approximately a time interval of 1150 to 1/25 s. To gain a better understanding of the capture mechanism and retention efficiency versus particle size, the flow through and around the Ifc was theoretically estimated. Normally beating Ifc create periodic, unsteady, three-dimensional flows at the entrance to the interfilament canal. During the active beat most of the water is deflected to flow around the branching cilia of the Ifc while some of the water is strained by these. Large particles (> 4 m) are stopped and transferred to the frontal current, whereas smaller particles either follow the flow around the Ifc and escape or they are stopped by the branching cilia. 相似文献