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Notes: SUMMARY. Gill structure and function are brietly considered, as are the main factors affecting the oxygen content of water. The review deals with quantitative, analytical aspects of oxygen uptake related to body size, temperature, oxygen content of water, salinity, water velocity, substratum and activity of Cammarus. A theoretical model relates oxygen uptake to growth and life-span of individuals. Several aspects of regression analysis, as applied to measurements of oxygen uptake, are examined and constructively criticized. The energetic cost of osmoregulation is calculated for G. pulex. The review concentrates on freshwater species of Gammarus but work on brackish-marine species is also included. A more detailed summary and conclusions are given at the end of the review.

Notes: SUMMARY. 〈list xml:id="l1" style="custom"〉1Mean tarnwater concentrations of CI- and other ions (Na +, K+, Ca2+, Mg2+, SO42-+ NO3-) decrease with increasing distance from the sea and altitude but are also related to solid geology. Lowest concentrations occur on slow-weathering igneous rocks (Borrow-dale Volcanics); minima of c. 100 μequiv. CI-I-1 are similar to the volume-weighted mean for bulk precipitation. At least 10–20% of Na+ is leached from upland catchments, giving Na+/CI- ratios greater than the equivalent ratio (0.86) in seawater and precipitation. Evapotranspiration at 20–30% annual rainfall accounts for CI- concentrations in many tarns on igneous rocks but not all; some CI- may be leached from the rocks in upland catchments and come from groundwaters at low altitudes near the sea. Sea-spray has little influence on tarnwaters near the coast.2On sedimentary rocks overall mean CI- concentrations are 27–73% higher than equivalent means on Borrowdale Volcanics; concentrations of other ions are also higher. A 5-fold to 10-fold range of CI-concentrations is not simply due to increased evapotranspiration. Na+/CI- ratios are 〈 0.86, especially on Skiddaw Slates where tarnwaters contain 10% or more excess CI- balanced by Ca2+, apparently derived from groundwaters rich in CaCI2. On other sedimentary rocks (Silurian Slates and Carboniferous, Triassic and Permian series) tarn waters display a similar but less pronounced excess of CI- and Ca2-+ relative to Na+. Some extra CI- may be captured by dry deposition on vegetation but a portion, perhaps 15–30% of the total, apparently comes from the rocks or from groundwaters via deep aquifers in contact with seawater or connate water.3Anthropogenic sources on the catchments are also considered: deicing salt used on highways in winter accounts for a 27% increase of CI- in Windermere South Basin over a 20-year period.

Notes: Sodium and potassium in streamwater were measured over a period of 2 years, and concentrations of other major ions were occasionally monitored. The supply of sodium, potassium and calcium in rainfall was measured over a period of 1 year. A tentative budget is given for annual income and output of sodium, potassium and calcium in the Duddon catchment. Sodium and potassium concentrations in streamwater were independent of stream discharge; both ions displayed an annual cycle of high concentrations in winter and low concentrations in summer. The input of sodium was dependent on rainfall, wind direction and wind speed; 40% of the annual supply in rain was precipitated in the autumn. Sodium income in rainfall during the remaining 9 months of the year was insufficient to balance the output in streamwater. Annual income of potassium in rainfall was equal to annual output in streamwater. But potassium was retained on the catchment during spring and summer and was slowly released to the streams in autumn and winter. Only about 10% of the annual calcium output was derived from atmospheric sources.

Notes: Comparisons are made of pH and the concentrations of major ions in streamwater from Brownrigg Well (the source of Whelpside Ghyll) and from the River Duddon. pH in Brownrigg Well is usually 〉5.7, but the concentrations of sodium, potassium and possibly calcium are near to the minima required to support the amphipod Gammarus pulex. In contrast most insect taxa are not affected by low ionic concentrations. It is postulated that these had a wider distribution in mountain streams prior to the acidification of poorly buffered waters by acid rainfall resulting from large-scale combustion of fossil fuels.

Notes: Individuals of Gammarus pulex were kept at 15°C for periods of 23–70 days on diets comprised of elm or oak leaves, Tricladium and Clavariopsis (Hyphomycete fungi), Molinia (grass), Zygogonium (alga), Nardia (liverwort). Both the mean interval between moults (mi), and daily increments in body wet weight, were related to diet. The lowest value for mi was 14·6 days on a diet of naturally decaying elm and oak leaves. The largest weight gains also occurred on this diet; the average daily gain in weight (Dw) = 130·8 μg/day, the mean specific gain in weight (Gw) = 1·69 μg %/day. On green Molinia and fungi diets Dw ranged from nil to 60·7 μg/day, and mi= 17·4–18·4 days was significantly (P〈0·01) longer than mi on leaf diets. Survival and growth were poor on brown Molinia. Nardia did not support growth or survival. A mixed diet of Tricladium, Zygogonium, Nardia and decaying grasses was not sufficient to promote an increase in body weight, and mi= 21·8 days. This diet represents the commonly available food materials in Mosedale Beck, an acid stream in the upper Duddon catchment. Survival and growth of G. pulex on fungi and leaf diets in media containing low concentrations of potassium ions are also described and discussed briefly in relation to the distribution of G. pulex in the upper catchment of the R. Duddon.

Notes: SUMMARY. 1. The distribution of softwater and acid tarns and streams in central Cumbria is briefly summarized and compared for the periods 1983-85 and 1949-56.2. Fifty-three upland tarns (altitude 〉350m) and forty lowland tarns (altitude 〈320m) were sampled on Skiddaw Slates, the Borrowdale Volcanic Series, and igneous intrusions. On these bedrocks, tarns and streams would be highly sensitive to further acidification if acid deposition increases above current levels. Twenty-six upland and seven lowland tarns are permanently acid with zero or negative alkalinity values throughout the year; mean pH ranged from 5.3 to 4.2. The other sixty upland and lowland tarns had positive mean Alk in the summers of 1983-85, ranging from 7 to 1227μequiv. I−1 Alk and mean pH5.7 to 〉7.0. Thirty-one of the sixty tarns had mean Alk 〈 100μequiv. I−1 in summer (May-September); sixteen became temporarily acid (negative Alk) for varying periods in winter. Acid episodes also occurred in the tarns in 1949-56.3. Acid and very low alkalinity tarns and streams commonly occur on the high western, central and northern fells. Few occur on the high eastern felts, where there are veins of calcite in exposed rocks.4. Seventy-five lowland tarns were sampled on Silurian Slates in southern Lakeland. On these bedrocks, tarns and streams are not highly sensitive to further acidification. Only six tarns had summer mean Alk 〈100μequiv. 1−1. No permanently acid tarns or streams were found.5. Over a mean span of about 30 years. Eel Tarn appears to have become slightly more acid and Harrop Tarn slightly less acid. The remainder of all tarns surveyed in 1983-85 have altered little, although there is a heavy load of acidic deposition on to the catchments and some tarns contain very low concentrations of Alk. Rapid acidification in recent years has been prevented by the neutralizing capacity of volcanic and sedimentary rocks. These rocks produce relatively high concentrations of Alk, up to 650μequiv.l−1 in some spring-fed streams on the central fells and even more at lower altitudes. Absence of coniferous

Notes: SUMMARY. Increase in body wet weight of Gammarus pulex fed on decaying elm leaves was followed to senescence and death. Growth in juveniles was approximately exponential; from birth to death it conformed to a logistic growth curve, with maximum absolute increments in weight about half-way through a life span of 350–450 days at 15°C. Some individuals lived longer, for up to 640–700 days. The instantaneous or specific growth rate was maximal near birth, at c. 5–6% wet wt day−1, and declined exponentially with increasing size and age. Over the range 4.7–14.8°C there was a log-log relationship between temperature and specific growth rate. Growth was maximal at 20°C in newborn animals and at 15°C in 6–9-mg animals.The specific growth rate of young individuals was fastest on decaying leaves of elm with a well developed flora of fungi and other microorganisms. Leached elm leaves without this flora supported growth at a lower rate. The latter diet was sufficient for survival and growth of newborn individuals; detritus, faeces or other food items were not needed. Isolated specimens grew as fast as those kept in groups. Growth was generally slower on leached leaves of oak and sycamore. In newborn animals fed on the fine roots of aquatic plants (Veronica, Rorippa and Glyceria), growth was as fast as on decaying elm leaves; growth on the green living leaves of the plants was slower, as on detritus from two streams and on a pure culture of an aquatic fungus.Consumption of leached elm leaves was related to leaf thickness. In a full gut the wet weight (1.34–1.37 mg) and volume (3.8–4.1 mm3) (for 20-mg animals) was independent of leaf thickness but dependent on animal size, increasing 4-fold over the range 2–50 mg body wt. Daily consumption (dry wt) was approximately equivalent to 50% body dry wt at 5 mg and 20% at 50 mg body wet wt. Individuals fed on thick leaves ingested 50% more dry weight per day and absorbed more in the gut than when fed on thin leaves, but the relative efficiency of absorption was the same at 36–59% for 10–20-mg animals. Weight-specific absorption in the gut was highest in juveniles and decreased with increasing body weight; relative efficiency of absorption was generally lower in the larger individuals. Assuming an energy value of 5 cal mg−1 dry wt for elm leaves, daily mean energy intake by absorption in thegutof G. pu/ex was2.2 cal mg−1 animaldry wt (9.2 J mg−1) in individuals of 0.4 mgdry wt (2 mg wet wt), decreasing to 0.3 cal mg−1 (1.3 J mg−1) at 10 mg dry wt (50 mg wet wt).Growth in Gammarus is briefly reviewed in the hght of work on other animals and it is emphasized that all aspects of feeding, growth and metabol-ism should be specifically related to size and age of the individuals, using well defined diets.

Notes: SUMMARY. In the laboratory, Asellus aquaticus devoured intact green leaves from growing shoots of the aquatic macrophyte Elodea canadensis. In four collections of A. aquaticus on Elodea in a lake (Windermere), c. 20% of the specimens contained in their guts fragments of green Elodea leaves; this material and pieces of oak (Quercus) were identified from characteristic leaf hairs. Some specimens had also eaten the filamentous alga Oedogonium. Fluorescence microscopy is a useful aid for screening invertebrates that may have eaten living plant tissues.Immature A. aquaticus, with an initial mean body length of c. 3 mm, wet weight c. 1 mg, were grown through sexual maturity over a 49-day period at 15°C in a series of twenty-two experiments (six to twelve isolated specimens in each experiment) comparing growth rates on different foods, including instances where no food was given. Animals were fed on a variety of items collected from the littoral of Windermere, plus some laboratory cultures of algae and bacteria. The highest mean specific growth rate (5.8% day−1) was obtained on young Elodea leaves mechanically shaken to remove epiphytes. Other diets yielding fast growth rates (3.7–5.3% day−1) were young growing leaves of Elodea with few epiphytes and older green and brown living leaves covered with a thick growth of epiphytic algae, epiphytic algae removed from Elodea, plastic imitation Elodea immersed in the lake until covered with attached algae, epilithic algae on stones, Oedogonium, and decaying oak leaves. Slower growth (1.3–2.2% day−1) and poorer survival was obtained on the following: a pure culture of the bacterium Sphaerotilus natans; cultured bacteria from lakewater; the filamentous algae Cladophora and Stigeoclonium both with and without epiphytes; faecal matter from Asellus; freshly killed Asellus; lake sediment. Some growth (mean = 0.7% day−1) and 50% survival for 21 days occurred in ‘starved’ animals kept in filtered, sterilized lakewater. Better survival and slightly faster growth (1.0–1.5% day−1) occurred in ‘starved’ animals kept in filtered and unfiltered lakewater.Growth of A. aquaticus was also experimentally determined from birth in animals fed on young green Elodea leaves and on decaying oak leaves. On both diets, growth was curvilinear and approximately exponential from birth to sexual maturity reached at c. 2mg wet weight in 46–60 days at 15°C. In older specimens the relative growth rate gradually fell over a period of 50 days, representing a more linear phase of growth during sexual maturity.

Notes: 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 (P 0.05) 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 regression.