Energy requirements of the red kangaroo (<Emphasis Type="Italic">Macropus rufus</Emphasis>): impacts of age,growth and body size in a large desert-dwelling herbivore.

Generally, young growing mammals have resting metabolic rates (RMRs) that are proportionally greater than those of adult animals. This is seen in the red kangaroo (Macropus rufus), a large (>20 kg) herbivorous marsupial common to arid and semi-arid inland Australia. Juvenile red kangaroos have RMRs 1.5–1.6 times those expected for adult marsupials of an equivalent body mass. When fed high-quality chopped lucerne hay, young-at-foot (YAF) kangaroos, which have permanently left the mother's pouch but are still sucking, and recently weaned red kangaroos had digestible energy intakes of 641±27 kJ kg^–0.75 day^–1 and 677±26 kJ kg^–0.75 day^–1, respectively, significantly higher than the 385±37 kJ kg^–0.75 day^–1 ingested by mature, non-lactating females. However, YAF and weaned red kangaroos had maintenance energy requirements (MERs) that were not significantly higher than those of mature, non-lactating females, the values ranging between 384 kJ kg^–0.75 day^–1 and 390 kJ kg^–0.75 day^–1 digestible energy. Importantly, the MER of mature female red kangaroos was 84% of that previously reported for similarly sized, but still growing, male red kangaroos. Growth was the main factor affecting the proportionally higher energy requirements of the juvenile red kangaroos relative to non-reproductive mature females. On a good quality diet, juvenile red kangaroos from permanent pouch exit until shortly after weaning (ca. 220–400 days) had average growth rates of 55 g body mass day^–1. At this level of growth, juveniles had total daily digestible energy requirements (i.e. MER plus growth energy requirements) that were 1.7–1.8 times the MER of mature, non-reproductive females. Our data suggest that the proportionally higher RMR of juvenile red kangaroos is largely explained by the additional energy needed for growth. Energy contents of the tissue gained by the YAF and weaned red kangaroos during growth were estimated to be 5.3 kJ g^–1, within the range found for most young growing mammals.Abbreviations BMR basal metabolic rate - DEI digestible energy intake - MER maintenance energy requirement - MER_g maintenance plus growth energy requirement - PPE permanent pouch exit - RMR resting metabolic rate - YAF young-at-foot Communicated by I.D. Hume     

Optimization of cell density and dilution rate in <Emphasis Type="Italic">Pichia pastoris</Emphasis> continuous fermentations for production of recombinant proteins

This paper provides an approach for optimizing the cell density (X_c) and dilution rate (D) in a chemostat for a Pichia pastoris continuous fermentation for the extracellular production of a recombinant protein, interferon (INF-). The objective was to maximize the volumetric productivity (Q, mg INF- l^–1 h^–1), which was accomplished using response surface methodology (RSM) to model the response of Q as a function of X_c and D within the ranges 150 X_c 450 g cells (wet weight) l^–1 and 0.1 _mD0.9 _m (_m=0.0678 h^–1, the maximum specific growth rate obtained from a fed-batch phase controlled with a methanol sensor). The methanol and medium feed rates that resulted in the desired X_c and D were determined based on the mass balance. From the RSM model, the optimal X_c and D were 328.9 g l^–1 and 0.0333 h^–1 for a maximum Q of 2.73 mg l^–1 h^–1. The model of specific production rate (, mg INF- g^–1 cells h^–1) was also established and showed the optimal X_c=287.7 g l^–1 and D=0.0361 h^–1 for the maximum (predicted to be 8.92×10^–3 mg^–1 g^–1 h^–1). The methanol specific consumption rate (, g methanol g^–1 cells h^–1) was calculated and shown to be independent of the cell density. The relationship between and (specific growth rate) was the same as that discovered from fed-batch fermentations of the same strain. The approach developed in this study is expected to be applicable to the optimization of continuous fermentations by other microorganisms.     

Feeding rates and energy deficits of juvenile and adult Japanese monkeys in a cool temperate area with snow coverage

Japanese monkeys, Macaca fuscata, living in a cool temperate forest experienced energy crises in winter. We measured feeding times and feeding rates (mass of foods eaten per unit time of feeding) in six different-sized, age–sex classes (1.2–12.6 kg body mass) in autumn and winter. One-, 2- and 3~4-year-olds spent 34–35% and 44–46% of the day feeding in autumn and winter, respectively. Monkeys less than 0 years old spent less time feeding (16–28%) than average in winter and autumn; adult females spent less (41%) in winter; and adult males spent less (25%) in autumn. All age–sex classes ate mainly fruits in autumn and the heavier classes fed more on tree bark than buds in winter. The feeding rate for fruits (2.3–53.5 g min^–1) was nine to 12 times faster than those for buds (1.0– 4.8 g min^–1) and bark (0.5–4.4 g min^–1), and energy content did not differ among fruits (22.1 kJ g^–1 dry mass), buds (19.9 kJ g^–1 dry mass) and bark (23.2 kJ g^–1 dry mass). Energy base feeding rates increased with body mass where the body mass exponent for buds (0.29) was smaller than those for bark (0.64) and fruits (0.63), which might be attributable to the unit size of food items and mass dependency of masticatory apparatus. Our monkeys obtained two to five times more energy in autumn (1567–1150 kJ day^–1) than in winter (604–3020 kJ day^–1). Adult females obtained 60% of expected energy expenditure and other classes obtained 77–88% of that in winter.     

Living conditions, abundance and biomass of under-ice fauna in the Storfjord area (western Barents Sea, Arctic) in late winter (March 2003)

The under-ice habitat and fauna were studied during a typical winter situation at three stations in the western Barents Sea. Dense pack ice (7–10/10) prevailed and ice thickness ranged over <0.1–1.6 m covered by <0.1–0.6 m of snow. Air temperatures ranged between –1.8 and –27.5°C. The ice undersides were level, white and smooth. Temperature and salinity profiles in the under-ice water (0–5 m depth) were not stratified (T=–1.9 to –2.0°C and S=34.2–34.7). Concentrations of inorganic nutrients were high and concentrations of algal pigments were very low (0.02 g chlorophyll a l^–1), indicating the state of biological winter. Contents of particulate organic carbon and nitrogen ranged over 84.2–241.3 and 5.3–16.4 g l^–1, respectively, the C/N ratio over 11.2–15.5 pointing to the dominance of detritus in the under-ice water. Abundances of amphipods at the ice underside were lower than in other seasons: 0–1.8 ind. m^–2 for Apherusa glacialis, 0–0.7 ind. m^–2 for Onisimus spp., and 0–0.8 ind. m^–2 for Gammarus wilkitzkii. A total of 22 metazoan taxa were found in the under-ice water, with copepods as the most diverse and numerous group. Total abundances ranged over 181–2,487 ind. m^–3 (biomass: 70–2,439 g C m^–3), showing lower values than in spring, summer and autumn. The dominant species was the calanoid copepod Pseudocalanus minutus (34–1,485 ind. m^–3), contributing 19–65% to total abundances, followed by copepod nauplii (85–548 ind. m^–3) and the cyclopoid copepod Oithona similis (44–262 ind. m^–3). Sympagic (ice-associated) organisms occurred only rarely in the under-ice water layer.     

Influence of soil temperature on methane emission from rice paddy fields

Methane emission rates from an Italian rice paddy field showed diel and seasonal variations. The seasonal variations were not closely related to soil temperatures. However, the dieL changes of CH₄ fluxes were significantly correlated with the diel changes of the temperature in a particular soil depth. The soil depths with the best correlations between CH4 flux and temperature were shallow (1–5cm) in May and June, deep (10–15cm) in June and July, and again shallow (1–5 cm) in August. Apparent activation energies (E_a) calculated from these correlations using the Arrhenius model were relatively low (50–150 kJ mol^–1) in May and June, but increased to higher values (80–450 kJ mol^–1) in August. In the laboratory, CH₄ emission from two rice cultures incubated at temperatures between 20 and 38°C showed E . values of 41 and 53 kJ mol^–1) Methane production in anoxic paddy soil suspensions incubated between 7 and 43°C showed E values between 53 and 132 kJ mol^–1 with an average value of 85 kJ mol^–1) and in pure cultures of hydrogenotrophic methanogenic bacteria E _a values between 77 and 173 (average 126) kJ mol^–1. It is suggested that diel changes of soil properties other than temperature affect CH₄ emission rates, e.g. diel changes in root exudation or in efficiency of CH⁴ oxidation in the rhizosphere.     

Nodularin in feathers and liver of eiders (Somateria mollissima) caught from the western Gulf of Finland in June–September 2005

Nodularins are cyanobacterial hepatotoxins, which may cause intoxication at very low exposure levels. The nodularin-producing cyanobacterium Nodularia spumigena usually forms massive blooms in much of the Baltic Sea during the summer season. Breast feathers and liver samples from common eider (Somateria mollissima) were analysed for nodularins by liquid chromatography–mass spectrometry (LC–MS) and enzyme-linked immunosorbent assay (ELISA). Fifteen eiders from the western Gulf of Finland were caught by hunters between June and September 2005. Blue mussels (Mytilus edulis), a dietary component of the birds, were also obtained by diving near the same marine area and time as the collection of the ducks. Eider breast feathers contained 6–52 μg nodularin-R (Nod-R)/kg dry weight (dw) by ELISA, and 8–43 μg Nod-R/kg dw by LC–MS. No Nodularia filaments were adhered to feather samples according to light microscopy assessment. Liver samples from the same individuals contained Nod-R between 3 and 48 μg/kg dw by LC–MS. Mussel samples from the area contained Nod-R at concentrations of 12–80 μg/kg dw by LC–MS. Analysis of bird feathers offers a facile and non-invasive means of assessing the exposure of birds to nodularins.     

A model for growth of Artemia franciscana cultures based on food ration-dependent gross growth efficiencies

Laboratory cultures of Artemia franciscana grown under batch regimes at constant temperatures (28 °C) and salinity (35 g l^–1), three initial food concentrations (0.1, 0.4 and 1 M cells ml^–1), various daily food rations (0.1–9M Dunaliella tertiolecta cells Artemia ^–1), and different population densities (1–16 ind ml^–1) were used to develop a model of population growth. Growth rates and gross growth efficiencies (K ₁) were largely independent of population densities and initial food concentrations but determined by age and daily amount of food ingested. While maximum growth rates were found with the highest rations, K _{1 max} peaked at rations of 0.5 million cells d^–1 and decreased at feeding levels above this. A contour plot showing the trend relating K ₁ to Artemia size and ingestion rate in combination and was used to model growth in analogous controlled feeding conditions. Computer simulations using this model paralleled published results of final 15-day average individual sizes of Artemia. Optimal results for near constant food utilization are predicted for high initial population densities (100 Artemia nauplii ml ^–1) and daily culls of enough animals to equilibrate food demand with food availability. This strategy could permit a range of Artemia sizes harvested, maximize final individual sizes and retain high total yields (> 1.2 kg dry wt 1^–1). Effects of different culture strategies are discussed.     

Diurnal vertical distribution of rotifers (Rotifera) in the Chara zone of Budzyńskie Lake,Poland

Diurnal vertical distribution of rotifers was investigated in the Chara bed and the water immediately above it in the shallow region (ca. 1 m depth) of Budzyskie Lake (Wielkopolski National Park, Poland) in early September 1998. Eighty one rotifer species were identified – 71 among Chara and 59 in the open water. Significant differences in rotifer densities were observed in the Chara, with highest numbers during the day (2316 ind. l^–1) and lowest numbers early morning (521 ind. l^–1) and at dusk (610 ind. l^–1). Above the Chara, the numbers of rotifers did not change significantly (615–956 ind. l^–1). Littoral- or limnetic-forms differed in their diel vertical distribution between both zones. One group of littoral species was characterized by increased densities in the Chara in the daytime, while a second group increased in density during the night. The densities of limnetic species, which were much higher in open water, decreased in the morning or daytime in this zone. These differences in the diel behaviour of particular groups of rotifers may be dependent on microhabitat and may also be related to different kinds of predation, the exploitative competition for shared food resources between rotifers and crustaceans, as well as typical adaptation to littoral or limnetic life.     

High density culture of the freshwater rotifer,Brachionus calyciflorus

The freshwater rotifer, Brachionus calyciflorus is one of the live food organisms used for the mass production of larval fish. In this study possibility of obtaining high density cultures of the freshwater rotifer B. calyciflorus were investigated. The two culture systems used differed in their air and dissolved oxygen supplies using three temperatures in each case: 24, 28 and 32 °C. Rotifers were batch-cultured using 5 l-vessels and fed with the freshwater Chlorella. The growth rate of rotifers significantly increased with an increase in temperature. The maximum density of the rotifers with air-supply at 24 °C, 6500 ind. ml^–1, was significantly lower than those cultured at 28 and 32 °C, i.e. 8600 and 8100 ind. ml^–1, respectively. Dissolved oxygen levels decreased with time and ranged from 0.8 to 1.4 mg l^–1 when the density of freshwater rotifer was the highest at each temperature. The highest density (19200 ind. ml^–1) of freshwater rotifer was obtained in cultures with a supply of oxygen at 28 °C. Densities of 13500 and 17200 ind. ml^–1 were found at 24 and 32 °C, respectively. Levels of NH₃-N increased with time and a dramatic increase of NH₃-N was observed at high temperatures. Levels of NH₃-N at 24, 28 and 32 °C were 13.2, 18.5 and 24.5 mg l^–1, respectively. These levels coincided with the highest rotifer density at each of the three temperatures. When rotifers were cultured with an oxygen-supply and pH was adjusted to 7, the maximum density of rotifer reached 33500 ind. ml^–1 at 32 °C . These results suggested that high density culture of freshwater rotifer, B. calyciflorus could be achieved under optimal conditions with DO value of exceeding 5 mg l^–1 and NH₃-N values of lower than 12.0 mg l^–1.     

The meiobenthos of five mangrove vegetation types in Gazi Bay,Kenya

The vertical distribution of meiofauna in the sediments ofAvicennia marina,Bruguiera gymnorrhiza,Ceriops tagal,Rhizophora mucronata andSonneratia alba at Gazi Bay (Kenya), is described. Seventeen taxa were observed, with highest densities in the sediments ofBruguiera (6707 ind. 10 cm^–2), followed byRhizophora (3998 ind. 10 cm^–2),Avicennia (3442 ind. 10 cm^–2),Sonneratia (2889 ind. 10 cm^–2) andCeriops (1976 ind. 10 cm^–2). Nematodes accounted for up to 95% of total densities; other common taxa were copepods, turbellarians, oligochaetes, polychaetes, ostracods and rotifers. High densities occurred to about 20 cm depth in the sediment. EspeciallyCeriops sediments show still high densities of nematodes (342 ind. 10 cm^–2) and copepods (11 ind. 10 cm^–2) in the deepest layer (15–22 cm). Particle size and oxygen conditions were major factors influencing meiobenthic distribution;Uca burrows had a major impact on distribution and abundance of meiofauna.     

A laboratory study of feeding and assimilation in Euchlanis dilatata lucksiana

Feeding of Euchlanis dilatata lucksiana, a brachionid rotifer isolated from the Loosdrecht Lakes (The Netherlands), was examined in the laboratory using ¹⁴C-labelled food. The gut-filling time at a food concentration of 9.6 µg C ml^–1 was about 15 minutes. Animals which were fed on 3 size fractions of the lake seston (< 7 µm, 7–15 µm, and 15–33 µm) showed a clear preference (Jacobs' selectivity index) for the largest size fraction. This fraction was composed predominantly of filamentous cyanobacteria. For animals weighing 0.37–0.49 µm C ind.^–1 the daily ration (daily food consumption per unit body weight × 100) ranged from 50 to 100% at food levels of 2 mg C l^–1 and below, but increased to 150–250% at food concentrations of 5 mg C l^–1 and above. The assimilation efficiency was 100% up to 5 mg C l^–1 of food, but decreased to about 80% at higher food levels.     

Bioenergetics and thermal physiology of American water shrews (<Emphasis Type="Italic">Sorex palustris</Emphasis>)

Rates of O₂ consumption and CO₂ production, telemetered body temperature (T_b) and activity level were recorded from adult and subadult water shrews (Sorex palustris) over an air temperature (T_a) range of 3–32°C. Digesta passage rate trials were conducted before metabolic testing to estimate the minimum fasting time required for water shrews to achieve a postabsorptive state. Of the 228 metabolic trials conducted on 15 water shrews, 146 (64%) were discarded because the criteria for inactivity were not met. Abdominal T_b of S. palustris was independent of T_a and averaged 38.64±0.07°C. The thermoneutral zone extended from 21.2°C to at least 32°C. Our estimate of the basal metabolic rate for resting, postabsorptive water shrews (96.88±2.93 J g^–1 h^–1 or 4.84±0.14 ml O₂ g^–1 h^–1) was three times the mass-predicted value, while their minimum thermal conductance in air (0.282±0.013 ml O₂ g^–1 h^–1) concurred with allometric predictions. The mean digesta throughput time of water shrews fed mealworms (Tenebrio molitor) or ground meat was 50–55 min. The digestibility coefficients for metabolizable energy (ME) of water shrews fed stickleback minnows (Culaea inconstans) and dragonfly nymphs (Anax spp. and Libellula spp.) were 85.4±1.3% and 82.8±1.1%, respectively. The average metabolic rate (AMR) calculated from the gas exchange of six water shrews at 19–22°C (208.0±17.0 J g^–1 h^–1) was nearly identical to the estimate of energy intake (202.9±12.9 J g^–1 h^–1) measured for these same animals during digestibility trials (20°C). Based on 24-h activity trials and our derived ME coefficients, the minimum daily energy requirement of an adult (14.4 g) water shrew at T_a = 20°C is 54.0 kJ, or the energetic equivalent of 14.7 stickleback minnows.     

Combined effects of food level and inoculation density on competition between Brachionus patulus (Rotifera) and the cladocerans Ceriodaphnia dubia and Moina macrocopa

Competition among cladocerans and rotifers is of considerable interest not only due to their close similarity in life history strategies, but also due to the considerable overlap they exhibit in their feeding habits. In tropical waterbodies, several genera of cladocerans, including Ceriodaphnia and Moina occur, simultaneously with rotifers. We tested over a period of 3 weeks the combined effects of food (0.5×10⁶ and 1.5×10⁶ cells ml^–1 of Chlorella) level and rotifer density on the competition between B. patulus and C. dubia and M. macrocopa using population growth experiments. For each cladoceran species we used 30 test jars of 50 ml capacity. The initial density of cladocerans was 0.2 ind ml^–1, while for B. patulus it was either 1 ind ml^–1 or 5 ind ml^–1. Neither the maximal population density nor the rate of population increase (r) of C. dubia was significantly affected by B. patulus. However, for M. macrocopa, both these variables were negatively affected by the rotifers. The combined effects of low food level and high initial density of B. patulus resulted in a 50% reduction in the peak population density of M. macrocopa. The population growth of B. patulus was negatively influenced by the presence of C. dubia and M. macrocopa. The results of the competition experiments conducted in the present study between cladocerans and rotifers suggest the existence of a more complex and delicate interaction than is generally thought.     

Induction of diapausing amictic eggs in Synchaeta pectinata

Amictic females of a clone of S. pectinata from Star Lake (Norwich, Vermont) may produce diapausing as well as non-diapausing (subitaneous) eggs. The proportion of diapausing eggs produced in cultures was unaffected by temperature (12 vs 19 °C) or rotifer population density (minima of 0.33 vs 3 ind. ml^–1) at 19 °C. However, at 19 °C this proportion was higher in cultures maintained at a low food level suppressing reproduction (5 × 10³ cells ml^–1 Cryptomonas erosa) than in those maintained at a high food level (2 × 10⁴ cells ml^–1); the treatment effect was marginally significant (p=0.067). Consistent with the effect of low food availability, a period of starvation was very effective in inducing the development of diapausing eggs. None of 19 females cultured individually from hatching at 19 °C on C. erosa (2 × 10⁴ cells ml^–1) in 1-ml volumes produced any diapausing eggs in 4 days (0 out of 349 eggs), while 13 out of 16 females subjected to a 15-hour starvation period 6 hours after birth produced one or more diapausing eggs during that time (34% of the 158 eggs produced by the 16 females were diapausing). Diapausing eggs produced and left at 19 °C hatched after 4 to 13 days. Those produced in cultures with a low food level took significantly longer to hatch (9.7 days) than those produced in cultures with a high food level (8.1 days) (p=0.022). In natural communities, S. pectinata should be able to respond directly and rapidly to poor food conditions by producing eggs that undergo an obligatory dormant period before resuming development.     

Feeding of Burbot, Lota lota, at Different Temperatures

Daily food intake of adult burbot, Lota lota, fed on vendace, Coregonus albula, were estimated experimentally at four different water temperatures (2.4, 5.1, 10.8 and 23.4°C). Mean daily food intake (MDI; g d^–1) and relative daily food intake (RDI; g g^–1 d^–1) increased with temperature from 2.4 to 10.8°C and decreased at 23.4°C. Temperatures of maximum daily food intake values were 13.6°C for MDI and 14.4°C for RDI. No correlation between food intake values and burbot weight was observed. RDI values were used to estimate annual food consumption of burbot population. Annual food consumption estimates were 9.7kg ha^–1 and 24.3kg ha^–1 when burbot biomass was 2.0 or 5.0kg ha^–1, respectively.     

Crustacean assemblage and environmental characteristics of a man-made solar saltwork in southern France,with emphasis on anostracan (Branchiopoda) population dynamics

Physical and chemical variables, anostracan populations (Artemia parthenogenetica and Branchinella spinosa) and other biota were studied during 1996–1997 in a Camargue saltern (max. depth 1 m). The taxonomic composition and density of macroinvertebrates were investigated twice monthly, based on benthic substrate and water column samples. Fauna was composed of three groups in terms of numerical importance. The benthic macroinvertebrates were represented only by nematodes (< 50 ind. m^–2 to > 500 ind. m^–2 in November–December and May respectively). The zooplankton was dominated by crustaceans, one cladoceran, Moina salina (ranging from 670 to 2350 ind. m^–2 in spring), two anostracans, Artemia parthenogenetica (< 50 ind. m^–2 in autumn), and Branchinella spinosa (max. 190 ind. m^–2 in December to absent in April), and two copepods, Cletocamptus retrogressus (max. density 2000 ind. m^–2 in November), and Eurytemora velox (max. density 650 ind. m^–2 in February–March). Insects (Chironomidae, Culicidae) were rare, with mean densities < 1 ind. m^–2. The phenology of each crustacean population is discussed in relation to physical and chemical water variables. Salinity appeared to be of greatest importance regulating the population abundance.     

Contemporary state of the zooplankton in Lake Peipsi

L. Peipsi is one of the richest fish lakes in Europe. Planktivorous smelt dominates in the fish fauna. The abundance of zooplankton fluctuates between 43 600–2241 500 ind m^–3, with the average 974 000 ind m^–3, biomass ranges from 0,09–3,69 g m^–3, with the average 1,86 g m^–3. Since the 1960s the abundance of rotifers has risen considerably while the mean zooplankter weight (B/N) has decreased from 0.005 mg to 0.004 mg. Zooplankton production (herbivores 20.6, predators 1.8, whole zooplankton community 22.4 g C m^–2 per period between May and October) can be considered high. Predatory zooplankton eats on an average 50% of the production of herbivorous zooplankton; about 50% of the whole zooplankton production (P_{Filt + Pred}) reaches fishes. The production of herbivorous zooplankton constitutes 10.1% of primary production. This ratio indicates a direct relationship between zoo- and phytoplankton in the food chain; the detrital food chain seems of little importance. About 6% of phytoplankton energy reaches fishes. The transformation of energy in the food web is efficient. On the basis of zooplankton L. Peipsi can be considered a moderately eutrophic or meso-eutrophic lake.     

Energy expenditure in relation to activity of lesser mouse deer (Tragulus javanicus)

Heat production (HP) of male and female mouse deer during eating, standing and sitting was determined using the open circuit respiration chamber (RC). The time taken for similar activities was also determined in an outdoor enclosure (OD). The animals were fed kangkong (Ipomoea aquatica), sweet potato (Ipomoea batatas) and rabbit pellet ad libitum. Male mouse deer consumed more dry matter (DM), organic matter (OM) and gross energy (GE) than female. The time for each activity of male and female mouse deer kept in RC and OD was similar. The average time spent in RC and OD for both male and female, respectively, for sitting (956 and 896 min/day) was significantly (P<0.01) longer than standing (463 and 520 min/day) and eating (21 and 24 min/day). Heat production for male and female mouse deer, respectively, during eating was the highest (0.44 and 0.43 kJ/kg W^0.75/min) followed by standing (0.37 and 0.33 kJ/kgW^0.75/min) and sitting (0.26 and 0.26 kJ/kg W^0.75/min). The difference in HP per min during standing between male and female was significant (P<0.05). The HP for 08.00–14.00 h and 14.00–20.00 h periods were higher than 20.00–02.00 h and 02.00–08.00 h periods. The overall HP for males during 08.00–14.00 h and 14.00–20.00 h periods were significantly (P<0.05) higher (114.8 and 119.2 kJ/kg W^0.75) than female (107.5 and 110.4 kJ/kg W^0.75), respectively.     

On the distribution patterns and population dynamics of sublittoral and profundal oligochaeta fauna from Lake Banyoles (Catalonia,NE Spain)

Oligochaeta assemblages from Lake Banyoles were composed of one species of Naididae and eight species of Tubificidae, Potamothrix heuscheri (8–1350 ind. m^–2) being the most abundant and widely distributed species, followed by Limnodrilus hoffmeisteri (25–858 ind. m^–2) and Psammoryctides barbatus (12–792 ind. m^–2). The remaining species were Potamothrix hammoniensis, Potamothrix bavaricus, Limnodrilus claparedeanus, Branchiura sowerbyi, Aulodrilus pigueti and Dero digitata, all of which occurred at lower densities and with restricted distributions.Regardless of sampling depth, maximum densities of oligochaetes were found in winter (up to 5,142 ind. m^–2 in December) and secondarily in June. Immature Tubificidae with hair setae and mature P. heuscheri were present and dominant throughout the year. Cestode parasites were recorded infesting L. hoffmeisteri and P. heuscheri populations.Oligochaeta densities increased with depth, but low oxygen concentrations (less than 1 mg l^–1) during a long period (4 months) in some basins of the lake acted as a key factor in reducing the density of worms and the species richness to one species, Potamothrix heuscheri.     

Feeding kinetics of Brachionus plicatilis fed Isochrysis galbana

Clearance and ingestion rates of Brachionus plicatilis were measured using ¹⁴C-labeled Isochrysis galbana Tahiti. Experiments were conducted at 20–22 °C, 20 ppt salinity, and algal concentrations ranging from 0.13–64 mg C 1^–1. Clearance rates were constant and maximal at concentrations <2 mg C 1^–1, with maximum rates ranging from 3.4–6.9 µl ind.^–1 hr^–1. The ingestion rate varied with food concentration, and was described by a rectilinear model. The maximum ingestion rate varied considerably, and was dependent on the growth rate of the rotifers. Depending on the pre-conditions, B. plicatilis ingested about 0.5 to 2 times its body carbon per day at saturating food concentrations.