摘要:

SUMMARY.Analysis of sub‐fossil chironomid remains in the top of Lough Neagh sediments shows a change from a mainlyTanytarsusfauna to a mainlyChironomusone. This has been accompanied by an exponential increase in numbers of head capsules deposited per m2per year. Tentative dating places this change within the last 130 years, with the most rapid increase in numbers post‐

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01690.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.A sampler designed to provide a quantitative estimate of the benthic invertebrates of littoral/sub‐littoral zones dominated bySphagnummoss is described. Data obtained from a small oligotrophic lake at a depth of 1 m using this sampler are presented. Optimum sample size was determined and samples comprising five sampling units were found to be adequate in terms of the number of invertebrate species present and their relative abundance. Similarity of such samples was greater than 90

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01691.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.Gut extracts fromGammarus pulexhydrolysed native and other cellulose substratesin vitro.Digestive fluid cellulase is probably endogenous as cell‐free fluid mediated cellulose hydrolysis, but no bacteria were isolated from the fluid which produced a detectable extra‐cellular cellulase. There was no apparent digestion of plant cell walls during their passage along the digestive tract, which took about 5–7 h at 10°C. The pH sensitivities of the digestive enzymes and the pH of the various regions of the gut suggest that carbohydrate digestion occurs in the proventriculus, midgut glands and anterior midgut, but protein digestion may be largely limited to the posterior midgut. The pH of the digestive fluid was altered slightly, but significantly, by the consumption of different natural and artificial test diets and by starvation. The most probable reason for the non‐digestion of plant cell‐walls is the lack of necessary enzymes other than cellulase. The role of cellulase may be confined to digesting the many small, non‐cellular particles which are presen

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01692.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.The development of marginal (shore‐line), sub‐littoral (3–6 m) and profundal (15–18 m) fauna was followed using timed collections in shallow water and artificial substrata in deeper regions.The reservoir started filling in July 1970 and was close to top water level in the autumn of that year. Samples in the marginal zone contained drowned terrestrial organisms and some Cladocera (Chydoridae) in February 1971 but by October, Chironomidae and Oligochaeta became abundant and micro‐crustaceans (copepods and cladocerans) formed about 98% of the total catch. Peak densities of micro‐crustaceans in the marginal zone were reached in the summer of 1971, but chironomids and oligochaetes were most abundant in the second year after filling. The numbers of marginal zone animals were greatest at the most sheltered site, and lowest at a site on the windward shore. At a stream mouth the rheophilic fauna present in April 1971 was replaced with limnophilic organisms (Chironomidae and Tubificidae) by September 1971.In the sub‐littoral,Hydra, Enchytraeidae, Orthocladiinae Tanytarsini and oribatoid mites were the most abundant taxa, whereas Naididae, Hirudinea, Ostracoda,Gammarus pulex, Chironomini andPisidiumspp. were numerous in the profundal zone.Total faunal numbers and biomass were greatest in the profundal zone in all years. The highest annual mean estimate of biomass in the sub‐littoral was 3.07 g (wet wt)m−2in the second year after filling, thereafter both numbers and biomass fell. In the profundal the maximum biomass (about 29 gm−2) was observed in the third and fourth years after filling. An estimate of total standing crop of benthic organisms below the drawdown limit, made in July 1974, gave a figure of about 43 tonnes, wet weight.Biomass estimates at Cow Green were compared with those in eighteen other reservoirs and were found to be high especially in relation to those from

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01693.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.Growth rates ofAmphinemura sulcicolliswere investigated at five main stations in the upper River Wear, Northern England. Retardation of growth was noted during November, December and January and comparison was made of the degree of such retardation at high and low stations.

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01694.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.The seasonal distribution ofParartemia zietzianaandArtemia salinawas studied in a South Australian saltfield.P. zietzianaoccurred alone at salinities from 112 to 214%‰ andA. salinaoccurred alone at salinities above 285%‰; the two species overlapped in the range 214 to 285%‰. Respiration experiments indicated thatA. salinahad a lower ‘critical’ oxygen concentration thanP. zietziana, apparently due to the presence of haemoglobin inA. salina. This may result in an adaptive advantage at high salinity and low dissolv

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01695.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.The feeding habits ofCobitis taeniawere studied by means of monthly samples taken over a 2‐year period, October 1972‐October 1974, from two sites, one on the River Great Ouse at Newport Pagnell and the other at some neighbouring gravel pits. Dietury components, seasonal variation in these components, and seasonal and diurnal variation in feeding intensity were examined. The ecological niche of the food items and their size range are discussed, since both these factors appeared important in governing the micro‐habitat of the fish.The feeding activity followed a seasonal cycle with little or no feeding in the winter and a high level of feeding activity in mid‐summer.The diet showed a predominance of small food items, such as chydorids. copepods and rhizopods. These items varied in occurrence during the feeding period which appeared to be related to their own abundance, pointing to non‐seleclive feeding by the fish. The small size and benthic habits of the food items, many of which are closely associated with surface layers of mud and weed, indicated a preference byCobitis taenia(L.) for feeding in this type ot habitat and on this type of food, in contrast to the stone loach.Noemacheilus barbatulus(L.), which is believed to inhabit stony areas and take larger f

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01696.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.Geometric mean (GM) shell shape in populations of limpets from three rivers was compared with that of populations from two lakes in England. The GM ratio of width on length was 0.78 in both river and lake limpets, but they respectively had GM ratios of 0.55 and 0.47 for height on width. The difference was compared statistically by prediction of mean values for height and width using linear logarithmic regressions. Shell height was significantly different (P0.05) in river limpets, which were about 20% taller than lake limpets at shell widths of 5.0–6.0 mm. The relationship between shell height and width or length was allometric in limpets from two rivers and isometric in a lake population. Similar results and conclusions were obtained using the GM regression (Teissier, 1948; Ricker, 1973) and the ordinary predictive regressio

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01697.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.Sediment quality and meiofauna distribution were investigated in the Shatt Al‐Arab near Basrah (Iraq). Four stations were fixed in a transect reaching from the eulittoral to the main channel of the river. The sediment was investigated with respect to wet mud density, dry mud density, water content, organic matter, calcareous substances, and allochthonous inorganic materials. There were no major differences between the sediments taken at the different stations. Sediment quality was not a limiting factor for the distribution of meiofauna; important factors were water current, light penetration and temperature. The current has a great influence on sediment structure, the main channel of the river had harder sediment consisting of clay. Because of high turbidity, light can reach the bottom only in shallow water at stations I and II; macrophytes were present only at these two stations. The highest numbers of invertebrates were found at station II (0.5 m depth). As water depth increased, the abundance of meiofauna decreased. Nevertheless, the number of individuals at station I (0.05 m) in the tidal zone was lower than at station II. This fact can be explained by the magnitude of changes of the environmental conditions, especially temperature and insolation. There were very large diurnal temperature fluctuations, fluctuating between 10 and 25°C on a single day. Many meiofauna species cannot tolerate such fluctuations and colonize mainly the deeper reaches of the river, which are continuously covered by water. Stronger currents in the middle of the river prevent the settlement of large numbers of animals in this ar

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01698.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARY.Axenic cultures ofPediastrum duplex, a green alga prominent in Lake Kinneret, Israel, assimilated and respired amino acids, acetate, glucose, glycollate and glycerol under conditions of light or darkness. Increased rates of uptake and respiration were observed in nutrient (P and N) depleted medium. Although ineffective in moderate light (30–100 μ Einstein m−2s−1) glycerol, glucose and leucine, but not glycollate, stimulated growth and yields under faint light (∼ 2 μ Einstein m−2s−1). In the dark, glycerol (and sometimes leucine) permitted growth. Kinetic studies with leucine indicated an active uptake mechanism effective at substrate concentrations from 0.5

ISSN:0046-5070    

DOI:10.1111/j.1365-2427.1977.tb01699.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY