Food,feeding and digestion in streptocephalus dichotomus baird (Crustacea: Anostraca)

Summary Gut analysis of Streptocephalus dichotomus revealed that the main source of food is phytoplankton. S. dichotomus is a non-selective filter feeder, taking in all the food-items carried in the feeding currents and passed through the midventral groove. The feeding currents are produced by the thoracic limbs.Feeding experiments have shown that the time taken for the passage of food is directly proportional to the number of days of starvation. Food intake of males did not significantly differ from that of females when fresh animals were used, as well as animals used after one day of starvation.Fresh males as well as females took in significantly more food than starved animals.The digestive enzymes such as carbohydrases, proteases and lipases are present in the gut. The optimal pH for amylase ranged between, 5.8 to 6.6, for protease 7.4 to 8.0 and for lipase 5.2 to 6.5.This work formed a part of the thesis submitted to the University of Madras, in 1970 for the award of the Degree of Doctor of Philosophy.     

Two new species of Cladoceran crustaceans of the genera macrothrix baird and Alona baird from Malaysia

Two new species of Cladocera were found during an intensive study of Malaysian zooplankton. Macrothrix malaysiensis sp. nov. is unique in the genus in possessing a characteristic posterodorsal spine on the carapace. The structure of the antennules is also diagnostic. Alona freyi sp. nov. closely resembles A. verrucosa Sars and A. rigidicaudis (Smirnov). However, it can be diagnosed by the characteristic head shield, labral plate, ventral setae and the structure of the postabdomen.     

Ecological studies on Meikle Kilrannoch Serpentines

Summary

Of the five ultrabasic rock outcrops in the Glen Clova district of Scotland two, near Meikle Kilrannoch hill, bear distinctive vegetation and are unusually toxic amongst serpentines. Soil analyses showed a very high Mg:Ca ratio with low calcium and relatively high nickel and chromium levels.

Plant analyses for a range of species have shown some with a high tissue Mg:Ca ratio and others with a much lower excess of magnesium over calcium. Moderately high concentrations of nickel and chromium occur, while there is evidence of high sodium levels in two species of maritime affinity and instances of high aluminium, iron, potassium and zinc concentrations. Comparisons with the Lime Hill serpentine confirm the view that the high soil Mg:Ca ratio is a major chemical cause of their extreme character.     

Ecological studies on ectomycorrhizal fungi: an introduction

Abstract

The characteristics of mycorrhizal associations in general and of different kinds of mycorrhizas are briefly indicated. The morphology, functional relationships, distribution, host specifity, succession and decline of ectomycorrhizas are concisely treated. Methods, advantages and limitations of four main approaches to ectomycorrhizal research are discussed. At the end an example of an attempt to an integrated approach is given.     

环境中基因工程微生物生态学研究

详细阐述了基因工程微生物(GEM)在环境释放中需考虑的主要问题：GEM的构建、基因转移、适合度、扩散、转运和潜在的生态影响等,并针对GEM特定的生态学特征和生态影响。提出了基因工程微生物生态学研究宜采取“具体问题具体分析”的策略。制定相应的研究方案,为安全有效地在非受控条件下应用GEM铺平道路．     

Ecological studies on algal-lysing bacteria in fresh waters

Algal-iysing bacteria are present in five lochs, two reservoirs, one sewage works and five alkaline soils whieh were examined. Nine out of thirty-six isolates have been studied in detail and all are gram-negative non-fruiting myxobaeteria. All are aero-philic, require a neutral or alkaline pH (optimum 7.0–9.0) for good growth, have temperature optima of 28–37°C, require contact with the host for lysis to oecur, and are so similar in morphology and host range that they all appear to be strains of a single genus. They lyse all bloom-forming Cyanophyeeae on whieh they have been tested, including species of Anabaena, Aphanizomenon, Gloeotrichia, Microcystis and Oscillatoria. Their abundance is usually correlated direetly with the abundance of Cyanophyeeae in eutrophic waters and it is probable that in most ecosystems the algae and the bacteria co-exist, although if the equilibrium changes markedly as a result of change in environmental conditions situations may arise where the bacteria may play an important role in the lysis of algal blooms. The available evidence suggests, however, that this is likely to be a rare occurrence in natural ecosystems.     

Ecological studies on potato mop-top virus in Scotland

Plants with symptoms of potato mop-top virus (PMTV) occurred in many commercial seed stocks of Arran Pilot and Red Craig's Royal potato in Scotland, but their incidence rarely exceeded 5%. In nuclear stocks of seed potatoes, most varieties examined in 1967 and 1968 were infected at one or more locality, but infected plants did not occur in all clones or at all stages of propagation of any one variety. infection of nuclear stocks resulted both from propagation on virus-infested land and from unwitting selection of infected plants to start new clones. PMTV was detected in farm soils ranging from light sands to heavy loams, in five Scottish counties. Soil was infested throughout the ploughed layer but the severity of infestation varied greatly within any one field; some sites of former potato clamps were heavily infested. PMTV was detected in field soil 12 years after potatoes were grown. In glasshouse tests many British crop and wild plants were colonized by Spongospora subterranea. Within some families all species tested were moderate to good hosts. (Solanaceae, Chenopodiaceae and Cruciferae), in others, species differed greatly in susceptibility (Compositae and Umbelliferae), and in a few, species were poor hosts or were not infected (Caryophyllaceae and Gramineae). Of the British crop and weed species that were moderate to good zoosporangial hosts of S. subterranea, only Solanum nigrum, potato, spinach and sugar beet were hosts of vector-borne PMTV. Potato probably survives between potato crops mainly in the resting spores of S. subterranea. PMTV was probably first brought to Europe with potatoes from South or Central America.     

The succinic dehydrogenase activity of eptocephalus dichotomus Baird

Summary The succinic dehydrogenase activity in Streptocephalus dichotomus in the entire animals as well as in the different regions of the body, increased with increase in temperature up to 30°C and at 33°C it decreased.In both males and females there exists a linear relationship between body weight and enzyme activity.Analyses of covariance revealed that the F ratios are not significant in the case of rate of succinic dehydrogenase activity between the two sexes or when the comparison is made within the sexes at the different temperatures.The succinic dehydrogenase activity in the thoracic region is higher than in the head and abdominal regions.This work formed a part of a thesis submitted for the Degree of Doctor of Phylosophy to the University of Madras in 1970.     

Ecological studies of freshwater rhizopods

Information on the distribution of 55 species of rhizopods from 585 waters in southern Sweden was analyzed for preference of temperature, oxygen content, pH, water colour, conductivity and phosphorus content. Some species showed no particularly strong demands for any physical or chemical factor, while others had a narrow range of tolerance. The habitat choice of rhizopods was investigated by examining 29 substrates and habitats that were found to be of varying importance to different species.     

Respiration of Streptocephalus dichotomus Baird (Crustacea : Anostraca)

Summary The Rate-temperature (R-T) curve for S. dichotomus tends to reach a peak at 30°C in both sexes in all the weight groups. As the temperature increases above 30°C the metabolic rate decreases considerably.The proportionate weight specific rate of oxygen uptake is the same for all sizes.There is no significance in the relationship between oxygen lethal levels and body weight.This work formed part of the thesis submitted for the award of the Degree of Doctor of Philosophy to the University of Madras, in 1970.     

Ecological studies on the timberline of Mt. Fuji

An ecological study of dry matter production was made in a dwarf forest dominated byAlnus maximowiczii at the timberline of Mt. Fuji. Annual gross production was estimated by two methods, namely the summation method using stem analysis and total photosynthesis calculated from leaf area and photosynthetic rate per leaf area. Seasonal changes in relative light intensity and in leaf area were measured in a quadrat. Photosynthesis and respiration rates of samples were measured in temperature-regulated assimilation chambers. The phytomass was 2,989 g d.w.m^?2, and those of stems and branches, leaves, and roots were 1,672 g, 293 g, and 1,024 g respectively. The growing period of this plant was about four months and this plant expanded leaves quickly. The maximum gross photosynthetic rate was 21 mg CO₂dm^?2 h^?1 on September 1. Annual net production estimated by examining the annual rings was 922 g d.w.m^?2 year^?1 and annual respiration was 735 g. Annual gross production estimated from photosynthetic rates was 1,747 g d.w.m^?2 year^?1. The sum of annual net production by stem analysis and respiration agree closely with gross production estimated from photosynthetic rate. Gross production of this dwarf forest is comparable to the beech forest of the upper cool temperate zone owing to the high photosynthetic rate ofAlnus maximowiczii.     

Ecological studies on the timberline of Mt. Fuji

To compare the nutrient economy of woody plants at timberline of Mt. Fuji, seasonal changes in nitrogen content in leaves were examined. There was remarkable difference in seasonal changes in leaf nitrogen content betweenAlnus maximowiczii and other deciduous trees at same habitat.A. maximowiczii scarcely withdrew the leaf nitrogen to woody part during the shedding period, while the other species withdrew about half of the leaf nitrogen to woody part.     

Ecological studies on the timberline of Mt. Fuji

The distribution of the meadow above the timberline and the structure of the forest at and below the timberline were investigated on the southeast slope of Mt. Fuji. At the same time, soil profiles, water content and nutrients in the soil as related to change in the structure of the plant community were examined to obtain the data regarding soil development with the course of succession. In the course of change in structure of forest, the plant community was classified into three types:Salix/Alnus dwarf forest,Larix forest andAbies/Picea forest. The change in the soil profile, from immature to mature soil, was observed. At the timberline the water content increased rapidly from about 10% of bare land to about 25% of timberline. The nitrogen and carbon contents also increased at timberline as compared with bare land. Relationships between successional stage and soil development were clarified on the area from bare land to climax forest. The present state of the timberline at the investigated area is discussed with reference to the course of change in forest structure and soil development. It was concluded that the timberline of the investigated area is in the process of moving to a higher altitude. This conclusion was reasonable in view of the factor of air temperature.     

Ecological studies on the Lime Hill serpentine,Scotland

Summary

Lime Hill is an example of a serpentine outcrop which shows only to a limited extent the features of vegetation often associated with ultrabasic rock. Plant and soil analyses from this site are presented and compared with those from other Scottish serpentines. Substantial quantities of heavy metals are present at Lime Hill. It is suggested that the cause of the absence of serpentine-characteristic plants lies in a relatively low soil Mg : Ca ratio and/or high P and K levels.     

Ecological studies on the microorganic population of usar soils

Summary Soils with pH varying from 7.1 to 11.0 were randomly selected for investigation of the microorganic population in relation to certain ecological factors. The number of microorganisms was highest at the upper horizon of soil. While no definite correlation was obtained between the average number of bacteria per gram of soil and the soil-pH, the fungi showed a progressive decrease in the number from 7.1 to 10.8, beyond which they were absent. The number of fungi increased during rains and that of the bacteria during winter. One hundred twenty-three fungi were isolated and their frequency percentage varied during different months of the year. Aspergilli were the dominant forms in alkaline soils. During the course of these investigations, one genus and six new species were discovered; twenty-two species of fungi isolated for the first time from Indian soils and five species from soil in general.A portion of the thesis submitted during July of 1962 in conformity with the requirements for the degree of Doctor of Philosophy in the University of Lucknow, Lucknow, India.