Macro-invertebrate communities associated with the macrophytes of Lake Vechten: structural and functional relationships

The macro-invertebrates associated with eight species of emergent, floating-leaved and submerged macrophytes were recorded in May-June 1979. The plant species were: Phragmites australis, Sparganium erectum, Typha angustifolia, Polygonum amphibium, Ceratophyllum demersum, Elodea sp., Myriophyllum spicatum and Nitella mucronata.All macrophytes had a high number of macro-invertebrate species in common; however, some animals were also species-specific, particularly those occurring on the emergent plants. As regards the food source and feeding mechanism, the detritivores, periphytiscrapers and omnivores predominated, followed by predatory carnivores. The seston-filtrators also form a significant part of the community biomass. The macrofaunal distribution depended strongly on colonizable plant surface area and vegetation density. The macrofaunal communities of the Elodea, Ceratophyllum and Phragmites stands contributed mainly to the lake's carbon cycle. Being poorly represented by herbivores, the macro-invertebrate communities will affect the lake's primary production only slightly.     

Size spectra and abundance of planktonic ciliates within various habitats in a macrophyte-dominated lake (Eastern Poland)

Body size, community structure, abundance and biomass of ciliates were compared in various stands of macrophytes in a macrophyte-abundant shallow lake in Eastern Poland. Samples were collected in belts of Phragmites, Typha, Ceratophyllum, Elodea, Stratiotes and Chara. Additionally, protozooplankton was collected from the open water zone surrounding the vegetation belts. Differences in numbers of ciliate taxa between micro-sites were statistically significant. The highest numbers were found in Chara and Ceratophyllum stands, lower numbers in Stratiotes and Elodea stands and the lowest in the open water, Phragmites and Typha areas. Ciliate biomass was, like density, significantly higher in submerged macrophytes than in emergent macrophytes and open water zones. Based on differences in macrophyte structure, two groups of habitats with similar patterns of size-related ciliate distribution were distinguished. The first group consisted of two vegetated zones of sparse stem structure (Phragmites and Typha) and the open water zone, the second group comprised submerged macrophyte species, which were more dense and complex. Generally, the abundance of ciliates correlated positively with total suspension solid (TSS) and total organic carbon (TOC) concentrations. In the Chara and Ceratophyllum stands, relations between ciliate numbers, TSS and TOC were stronger.     

GENETIC DIVERSITY IN THE MONOECIOUS HYDROPHILE CERATOPHYLLUM (CERATOPHYLLACEAE)

This study surveys genetic variation in two clonal, monoecious, water-pollinated species that differ in their extent of sexuality and distributional range. Electrophoresis was used to quantify allozyme variability in 12 Wisconsin populations of the widespread Ceratophyllum demersum and the rare C. echinatum. Electrophoretic data indicate that populations of both species have low levels of sexual recombination, low levels of variation, and are structured genetically like inbreeding terrestrial plants. Ceratophyllum populations differ from “typical” clonal terrestrial plants by lower genetic diversity, lower proportions of multiclonal populations, and fewer genotypes per population. In two populations where sexual recombination is documented, heterozygosity is low with significant deficiencies. Monoecy in Ceratophyllum may be related to historical evolutionary factors, whereas vegetative reproduction has a greater influence on the genetic population structure of extant populations. The low genetic identity between C. demersum and C. echinatum supports their recognition as distinct species.     

Development of a zooplankton community including <Emphasis Type="Italic">Heterocope saliens</Emphasis> Lillijeborg in an experiment with hydrophytes

The influence of the submerged plants Ceratophyllum demersum L. and Elodea canadensis Michx. and the floating plant Hydrocharis morsus-ranae L. on the species composition and quantitative parameters of a zooplankton community was studied experimentally. Among submerged vegetation, the development of the predaceous calanid Heterocope saliens Lilljeborg was suppressed. An increase in the number of zooplankter species was observed in all experimental ecosystems with hydrophytes. The species similarity of zooplankton was higher between communities with plants of the same ecological group than with plants of different groups. The highest average zooplankton biomass, as determined by the abundance of Daphnia longispina O.F. Müller and Simocephalus vetulus (O.F. Müller), was observed in experiments with Elodea. The highest average abundance over the experimental period was recorded among Ceratophyllum, where the abundance of Rotifera, chydorids, and copepods common in hydrophyte beds was higher than in other versions of the experiment.     

Impacts of a submerged plant (Elodea canadensis) on interactions between roach (Rutilus rutilus) and its invertebrate prey communities in a lake littoral zone

1. Using 5‐m² field enclosures, we examined the effects of Elodea canadensis on zooplankton communities and on the trophic cascade caused by 4–5 year old (approximately 16 cm) roach. We also tested the hypothesis that roach in Elodea beds use variable food resources as their diet, mainly benthic and epiphytic macroinvertebrates, and feed less efficiently on zooplankton. Switching of the prey preference stabilises the zooplankton community and, in turn, also the fluctuation of algal biomass. The factorial design of the experiment included three levels of Elodea (no‐, sparse‐ and dense‐Elodea) and two levels of fish (present and absent). 2. During the 4‐week experiment, the total biomass of euplanktonic zooplankton, especially that of the dominant cladoceran Daphnia longispina, decreased with increase in Elodea density. The Daphnia biomass was also reduced by roach in all the Elodea treatments. Thus, Elodea provided neither a favourable habitat nor a good refuge for Daphnia against predation by roach. 3. The electivity of roach for cladocerans was high in all the Elodea treatments. Roach were able to prey on cladocerans in Elodea beds, even when the abundance and size of these prey animals were low. In addition to cladocerans, the diet of roach consisted of macroinvertebrates and detrital/plant material. Although the biomass of macroinvertebrates increased during the experiment in all Elodea treatments, they were relatively unimportant in roach diets regardless of the density of Elodea beds. 4. Euplanktonic zooplankton species other than Daphnia were not affected by Elodea or fish and the treatments had no effects on the total clearance rate of euplanktonic zooplankton. However, the chlorophyll a concentration increased with fish in all the Elodea treatments, suggesting that fish enhanced algal growth through regeneration of nutrients. Thus, our results did not unequivocally show that Elodea hampered the trophic cascade of fish via lowered predation on grazing zooplankton. 5. In treatments with dense Elodea beds (750 g FW m^?2), chlorophyll a concentration was always low suggesting that phytoplankton production was controlled by Elodea. Apparently, the top‐down control of phytoplankton biomass by zooplankton was facilitated by the macrophytes and operated simultaneously with control of phytoplankton production by Elodea.     

Long‐term allelopathic control of phytoplankton by the submerged macrophyte Elodea nuttallii

相似文献   

Can allelopathically active submerged macrophytes stabilise clear-water states in shallow lakes?

Inhibition of phytoplankton by allelochemicals released by submerged macrophytes is supposed to be one of the mechanisms that contribute to the stabilisation of clear-water states in shallow lakes. The relevance of this process at ecosystem level, however, is debated because in situ evidence is difficult to achieve. Our literature review indicates that allelopathically active species such as Myriophyllum, Ceratophyllum, Elodea and Najas or certain charophytes are among the most frequent submerged macrophytes in temperate shallow lakes. The most common experimental approach for allelopathic interference between macrophytes and phytoplankton has been the use of plant extracts or purified plant compounds. Final evidence, however, requires combination with more realistic in situ experiments. Such investigations have successfully been performed with selected species. In situ allelopathic activity is also influenced by the fact that phytoplankton species exhibit differential sensitivity against allelochemicals both between and within major taxonomic groups such as diatoms, cyanobacteria and chlorophytes. In general, epiphytic species apparently are less sensitive towards allelochemicals than phytoplankton despite living closely attached to the plants and being of key importance for macrophyte growth due to their shading. Light and nutrient availability potentially influence the sensitivity of target algae and cyanobacteria. Whether or not additional stressors such as nutrient limitation enhance or dampen allelopathic interactions still has to be clarified. We strongly propose allelopathy as an important mechanism in the interaction between submerged macrophytes and phytoplankton in shallow lakes based on the frequent occurrence of active species and the knowledge of potential target species. The role of allelopathy interfering with epiphyton development is less well understood. Including further levels of complexity, such as nutrient interference, grazing and climate, will extend this ecosystem-based view of in situ allelopathy.     

Biology of excessive weed growth in the hydro-electric lakes of the Waikato River,New Zealand

In 1965 a massive growth of Ceratophyllum demersum caused the shut-down of one power station (Ohakuri) on the Waikato River. As a result a study was commenced of the biology of the weeds in the Waikato hydro-electric lakes. There are four major exotic weeds, Ceratophyllum, Lagarosiphon major, Egeria densa and Elodea canadensis, all of which form extensive beds. The first three have only appeared in the lakes since 1960 but Elodea was probably present earlier. Efforts to control the excessive growth by diquat have not proved successful and booms protecting the intake fail when a massive amount of weed is liberated after storms. Reasonable control can be obtained by means of lake lowering in mid-summer. Studies of Lagarosiphon, Egeria and Ceratophyllum have enabled the water temperature range, compensation points and certain nutrient requirements to be established under New Zealand conditions. Significant regions in the upper Waikato River are highly thermal and these waters are rich in arsenic. The weeds accumulate this arsenic and values of over 1000 ppm dry wt. have been recorded. This makes them very unsuitable for stock feed if mechanical harvesting were to be employed. Ceratophyllum and Lagarosiphon both appear to be shade plants, the former existing in a coarse winter form and a finer summer form. Day length affects growth rate as also does light quality, dissolved bicarbonate and rate of water flow. Limnological data show a gradual nitrogen enrichment of the lakes as one passes downstream, with periodic local phosphate enrichment after pasture top-dressing activities. Soluble iron is present in the waters and this appears to be important for massive growth. In quieter waters massive Lagarosiphon growth can result in temporary oxygen depletion of the water as compared with open lake water.     

Experiments on growth interactions between two invasive macrophyte species

Abstract. The success of invasive species has been attributed to the ability to displace other species by direct competition. We studied growth and possible competition between the two macrophyte species Elodea nuttallii and E. canadensis, because the former has been observed to replace the latter in the field. Additional experiments were conducted in aquaria with mixed plantings of Elodea species. Species growth was measured and competitive abilities of each species determined by applying the reciprocal yield model to mean plant weight and length. In monocultures the growth rates of the two species were similar, while in mixtures the growth rate of E. canadensis was significantly lower than that of E. nuttallii. E. canadensis was more sensitive to intraspecific than to interspecific neighbours, whereas E. nuttallii was indifferent to the presence of neighbours. Differential growth characteristics of Elodea species can explain the displacement of E. canadensis by E. nuttallii under eutrophic field conditions.     

Morphological and Chemical Changes Induced by Herbivory in Three Common Aquatic Macrophytes

The Dry Matter Content (DMC), the total phenolic content, the production of new branches and the plant fragmentation were compared in three macrophyte species (Elodea canadensis, Elodea nuttallii and Myriophyllum spicatum) exposed or not to snail herbivory. Grazing significantly reduced the DMC of M. spicatum and E. canadensis, but had no effect on the DMC of E. nuttallii. The phenolic contents of Elodea species were not modified by snail herbivory, whereas that of M. spicatum significantly increased when exposed to grazers. The number of new branches produced by M. spicatum and E. canadensis plants, and the fragmentation of E. canadensis also increased in response to herbivory. Chemical defences are therefore probably constitutive in Elodea and induced in M. spicatum, and morphological changes can be related to species growth form and synthesis of phenolic compounds. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Allelopathic influence of Hydrilla verticillata (L.F.) Royle on the distribution of Ceratophyllum species

Ceratophyllum demersum L. and C. muricatum Chamisso are not found to grow together with Hydrilla verticillata (L.f.) Royle in India. An experimental study shows that Hydrilla is allelopathic to the two species of Ceratophyllum and inhibits their growth. Thus, the distribution of Ceratophyllum species is limited by the presence of Hydrilla.     

Population changes in aquatic invertebrates living on two water plants in a tropical man-made lake

Summary In the Gorge region of the Man-made Volta Lake in Ghana the submerged weed Ceratophyllum and the floating Pistia were collected with their associated macroscopic invertebrates between February and November 1965. These collections were studied in order to determine the difference in animal population in both plants and their changes over the year during which they experience a tropical climate with one flood season.During the course of the study 12718 plant-associated water invertebrates were collected, from which 7920 were found on the inshore Ceratophyllum, 484 on the off shore Ceratophyllum, and 4314 on Pistia.A sample of each plant was arbitrarily selected from which animals were collected and their abundance and standing crop calculated.Nearly all animals collected occurred to some extent in both plants, but some groups differed greatly in their densities. Diptera were most abundant on the inshore Ceratophyllum while on Pistia Diptera and Crustacea were most numerous, followed by Oligochaeta. As regards the standing crop, in Ceratophyllum Diptera and Hemiptera were equally important, but in Pistia Odonata were predominant.In the off-shore Ceratophyllum Ephemeroptera were the most abundant group, followed by Diptera and Mollusca, compared with Diptera, Crustacea and Odonata for the inshore Ceratophyllum. In standing crop the habitats are dominated by the same groups respectively.While in numerical abundance microphagous organisms predominate in both Pistia and Ceratophyllum, by weight predators, represented by large anisopteran nymphs and Diplonychus (Hemiptera) formed more than 70% of the total population in Pistia, compared to 37% in Ceratophyllum. Ceratophyllum offers more adequate protection and hiding places for animals as well as a better feeding surface especially for microphagous forms than does Pistia. The habitat in both plants is greatly influenced by physical and chemical properties of water during the season of harmattan winds in February and March and during the flood season, the latter resulting in an increase in Lake level. During the floods the animal population responded by a sharp decrease both in number and weight of animals present. The possible reasons for this phenomenon are discussed in relation to other limnological changes at this time.     

Growth limitation of submerged aquatic macrophytes by inorganic carbon

1. This study determined the effects of CO₂ and HCO₃- enrichment on in situ growth of two submerged macrophytes, Elodea canadensis and Callitriche cophocarpa, in two Danish lakes: Lake Hampen and Lake Væng. Lake Hampen is an oligotrophic low-alkaline lake (0.4 meq ^?1) and Lake Væng is mesotrophic with an alkalinity of 1.1 meq 1-^?1. In Lake Hampen experiments were carried out throughout the growth season, whereas experiments in Lake Væng were restricted to late summer. The CO₂ and HCO₃-enrichment procedures used increased the concentration of free-CO₂ by 500–1000 μM and the concentration of HCO₃- by about 80 μM. 2. The concentration of free-CO₂ in Lake Hampen was about five times atmospheric equilibrium concentration (55 μM) in early summer declining to virtually zero at the end of summer. 3. Under ambient conditions Callitriche, which is restricted to CO₂ use, was unable to grow and survive in both lakes. In contrast, Elodea, which has the potential to use HCO₃- in photosynthesis, grew at rates varying from 0.046 to 0.080 day^?1 over the season. 4. Under CO₂ enrichment the growth rate of Callitriche varied from 0.089 to 0.124 day^?1 and for Elodea from 0.076 to 0.117 day^?1 over the season. Enrichment with HCO₃-affected Elodea only and only to a limited extent. This may be a result of insufficient increase in [HCO₃-] upon enrichment or to a limited capacity of the plants to take up HCO₃-. 5. The substantial stimulation of in situ growth of Elodea and Callitriche by enhanced concentrations of free-CO₂ shows that inorganic carbon is an important determinant of growth of submerged macrophytes and that inorganic carbon limitation of in situ growth may be a common phenomenon in nature, even in lakes with an alkalinity as high a 1 meq 1-^?1. Inorganic carbon, however, is only one of many parameters important for growth, and the growth rates of Elodea at both ambient and high free-CO₂ were closely coupled to day length and photon irradiance, indicating that light had an ultimate control on growth.     

Representation of aquatic vegetation change by plant macrofossils in a small and shallow freshwater lake

We explored spatial and temporal relationships between contemporary aquatic vegetation and surface sediment macrofossil remains in a small, shallow, English lake (Green Plantation Pond). The aquatic vegetation of Green Plantation Pond underwent a marked compositional change after 2005 with a shift from Elodea spp.-Potamogeton pusillus-Chara spp. to Ceratophyllum spp.-Chara spp.-Potamogeton crispus dominance. By comparing macrophyte and plant macrofossil distributions at multiple, closely spaced points in Green Plantation Pond for 2000 and 2008–2009, we studied the ability of macrofossils to track this major aquatic vegetation change. Representation of macrophytes by macrofossils was high with 63 and 76 % of extant plant species recorded by macro-remains in the 2000 and 2009 sediment surveys respectively. Nevertheless, plants were both over-represented (Nitella flexilis, Chara spp. and Zannichellia palustris) and under-represented (Ranunculus sect. Batrachium, Potamogeton spp.) in the sediment record in terms of relative macrofossil abundances and the number of occupied sample points. The study also revealed a lack of preservation of Elodea spp. leaf remains in the second (2009) survey compared to the first (2000) probably due to a longer time interval (5 vs. 10 months) between macrophyte and sediment sampling. Nevertheless, the macrofossils reliably recorded both the main shift in the contemporary vegetation (e.g. especially increases in Ceratophyllum spp. and P. crispus abundance) and other more subtle floristic changes (e.g. increases in Myriophyllum spicatum and Lemna spp.) exceptionally well. This study highlights the huge potential of macrofossils for tracking sub-decadal changes in the aquatic vegetation of small, shallow lakes.     

FOSSIL CERATOPHYLLUM (CERATOPHYLLACEAE) FROM THE TERTIARY OF NORTH AMERICA

Fossil fruits and a vegetative axis assignable to the extant genus Ceratophyllum are described from four North American Tertiary localities. Fossil fruits assignable to the extant species C. muricatum and C. echinatum are reported from the Eocene Green River and Claiborne formations, and the Miocene Esmerelda Formation, respectively. An extinct species, C. furcatispinum, is described from the Paleocene Fort Union Formation and represents the oldest published report of Ceratophyllum in the fossil record. The existence of extant angiosperm species in the Eocene is very unusual and may be attributable in this case to slow evolutionary rates and unusual evolutionary properties associated with hydrophily in the genus Ceratophyllum.     

Strong growth limitation of a floating plant (Lemna gibba) by the submerged macrophyte (Elodea nuttallii) under laboratory conditions

1. The asymmetric competition for light and nutrients between floating and submerged aquatic plants is thought to be key in explaining why dominance by either of these groups can be stable and difficult to change. 2. Although the shading effect of floating plants on submerged plants has been well documented, the impact of submerged plants on floating plants has been poorly explored hitherto. 3. Here, we used laboratory experiments to examine how submerged plant (Elodea nuttallii) alter nutrient conditions in the water column and how this affects the growth of floating plants (Lemna gibba). 4. We demonstrate that, at higher nutrient concentrations, Lemna is increasingly likely to outcompete Elodea. 5. Under low nutrient concentrations (0.1–2 mg N L^?1) Elodea can strongly reduce the growth of Lemna. Growth of floating plants virtually stopped in some of the experiments with Elodea. 6. Extremely reduced tissue N, Mn, chlorophyll and elongated roots indicated that the growth inhibition of Lemna by Elodea was predominantly caused by the latter’s impact on the nutrient conditions for floating plants. 7. These results strengthen the hypothesis that submerged plants can prevent colonization of a lake by floating plants.     

Can snail herbivory influence the outcome of competition between Elodea species?

Elodea nuttallii is more competitive than Elodea canadensis but is also more palatable to herbivores. We tested if grazing by generalist invertebrate herbivores could modify the competitive abilities of E. nuttallii, and thereby influence the outcome of the competition between the two Elodea species. The influence of snail herbivory on the competitive interactions between the two Elodea species cultivated together in indoor tanks was tested for 2 months. The presence of Lymnaea stagnalis in the tanks reduced significantly the final number of rootings, as well as the final biomass of E. nuttallii, but not the surface colonised by this species, whereas only the final number of rootings of E. canadensis was reduced. However, E. nuttallii remained the dominant species. We conclude that snail herbivory can influence the outcome of competition between Elodea species. However, snails are probably not an effective biological control agent of E. nuttallii.     

Die Photosynthese plasmolysierter Wasserpflanzen

• 1 . Mit Hilfe der elektrochemischen Sauerstoffbestimmung war es möglich, die Photosynthese dreier submerser Wasserpflanzen — Ceratophyllum demersum, Elodea canadensis und Riccia fluitans — in verschieden konzentrierten Zuckerlösungen kontinuierlich zu bestimmen. Überführt man die Pflanzen von Leitungswasser in 0,5 mol Mannitlösung (ebenfalls mit Leitungswasser angesetzt), plasmolysieren zwar die drei Arten sehr rasch, doch nur bei Riccia zeigte sich eine leichte Depression der Photosynthese
• 2 . Bei der Überführung in 1 mol Glucoselösung reagierten die drei Arten mit einer deutlichen Schockwirkung (Abb. 2), die jedoch bei Ceratophyllum vollständig überwunden wurde
• 3 . Eine schrittweise Überführung von Elodea in ansteigende Glucosemolaritä-ten zeigte zwischen 0,6 und 0,7 mol Glucose ein schrittweises Absinken der Photosynthese zu O. Eine Überführung in normales Leitungswasser zeigte bei jenen Sprossen, die plasmolysiert waren, keine Erholung. Bei an starkes Sonnenlicht angepaßten Elodea-Pflanzen war der kritische Bereich mit sofortigem Abfall der Photosynthese auf 1,8 bis 2 mol Glucose verschoben
• 4 . a) Es können also in hypertonischen Lösungen zwei Reaktionen unterschieden werden; eine Langzeitreaktion bei Konzentrationen der Grenzplasmolyse ohne sofortige Senkung der Photosynthese, jedoch gefolgt vom völligen Zusammenbruch des Lebenszustandes nach einigen Stunden b) Eine sofortige Hemmung der Photosynthese bei höheren Konzentrationen
• 5 . Die Atmung war weit weniger empfindlich gegenüber dem osmotischen Wasserverlust als die Photosynthese

     

Growth enhancement of the macrophyte Ceratophyllum demersum in the presence of the snail Planorbis planorbis: the effect of grazing and chemical conditioning

• 1 The effects of epiphyton grazing and nutrient recycling by the freshwater snail Planorbis planorbis on the growth of the macrophyte Ceratophyllum demersum were examined in laboratory experiments.
• 2 Ceratophyllum plants grown in the presence of snails, or in water chemically conditioned by snails, were significantly longer, had more healthy nodes of leaves, and more growing tips than Ceratophyllum plants grown in isolation. There were no significant differences between the growth of plants that were grazed by snails, and those plants which received water chemically conditioned by snails.
• 3 Adult P. planorbis released 3.74 × 10^?4μg phosphate, 23.9 × 10^?4μg nitrate, 4.38 × 10^?4μg ammonia, and 0.79 × 10^?4μg of urea mg^?1 wet weight of snail h^?1. Measurements of these chemicals in the experimental systems suggested that ammonia was an important nutrient in stimulating the growth of Ceratophyllum.
• 4 Removal of epiphyton by grazing snails significantly prolonged the life of individual Ceratophyllum leaves compared to ungrazed leaves.

     

Feeding and growth of Asellus aquaticus (Isopoda) on food items from the littoral of Windermere, including green leaves of Elodea canadensis

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.