Interactions between developmental processes,growth, and food selection in the larvae and juveniles of Rutilus rutilus (L.) (Cyprinidae)

Summary The aim of this study was to assess the effects of developmental events, occurring in fish during the first weeks after hatching, on the quantity and quality of the ingested food and on growth. The investigation was carried out with the larvae and juveniles of Rutilus rutilus, the single cyprinid species occurring in an oligotrophic subalpine lake in Tirol, Austria. Comparison between availability of prey in the water and gut contents suggests that the selection of food by the young fish is strongly influenced by developmental processes. For example, the prevalence of indigestible phytoplankton in the gut of young larvae can be taken as a sign of the not yet fully developed sensory and locomotory capacities of the young fish (El-Fiky et al. 1987). Furthermore, quantitative and qualitative changes in the gut contents correlate strongly with changes in the form and relative length of the gut, but reflect only weakly the availability of prey in the water. In the Seefelder See population of R. rutilus the switch from a phytoplankton to a cladoceran dominated diet is accompanied by an increase in relative growth rate by nearly one order of magnitude (Wieser et al. 1988).     

Effect of water temperature,salinity, and their interaction on growth,plasma osmolality,and gill Na,K-ATPase activity in juvenile GIFT tilapia Oreochromis niloticus (L.)

We used a central composite rotatable experimental design and response surface methodology to evaluate the effects of temperature (18–37 °C), salinity (0–20‰), and their interaction on specific growth rate (SGR), feed efficiency (FE), plasma osmolality, and gill Na⁺, K⁺-ATPase activity in GIFT tilapia juveniles. The linear and quadratic effects of temperature and salinity on SGR, plasma osmolality, and gill Na⁺, K⁺-ATPase activity were statistically significant (P<0.05). The interactive effects of temperature and salinity on plasma osmolality were significant (P<0.05). In contrast, the interaction term was not significant for SGR, FE, and gill Na⁺, K⁺-ATPase activity ⁽P>0.05). The regression equations for SGR, FE, plasma osmolality, and gill Na⁺, K⁺-ATPase activity against the two factors of interest had coefficients of determination of 0.944, 0.984, 0.966, and 0.960, respectively (P<0.01). The optimal temperature/salinity combination was 28.9 °C/7.8‰ at which SGR (2.26% d¹) and FE (0.82) were highest. These values correspond to the optimal temperature/salinity combination (29.1 °C/7.5‰) and the lowest plasma osmolality (348.38 mOsmol kg⁻¹) and gill Na⁺, K⁺-ATPase activity (1.31 µmol Pi. h⁻¹ g⁻¹ protein), and resulted in an energy-saving effect on osmoregulation, which promoted growth.     

Influence of oxygen and temperature on growth and metabolic performance of Paralichthys lethostigma (Pleuronectiformes: Paralichthyidae)

In this study, we apply Fry's classification of environmental factors to demonstrate the limiting effects of oxygen and its interaction with temperature on the growth of juvenile P. lethostigma. We also evaluated the properties of two metabolic indices, marginal metabolic scope (MMS) and limiting oxygen concentration (LOC), as indicators of metabolic scope. We found that oxygen limitation has its greatest impact near the optimum temperature for growth of the species. At 29 °C a reduction from 6.00 mg/L to 4.00 mg/L caused a 50% reduction in growth rate while at 27 °C the reduction had no significant effect on growth rate. The results are particularly relevant because these temperatures and oxygen concentrations are commonly observed in nursery areas during summer months. At all temperatures fish from the lowest oxygen treatment (1.75 mg/L) had negative growth rates. Comparisons between daily oscillating oxygen treatments and constant treatments failed to demonstrate significant effects. At temperatures past the optimum, growth rates between the 6.00 mg/L and 4.00 mg/L treatments were not statistically different. LOC was significantly affected by temperature, oxygen, and their interaction. Estimates were positively correlated with oxygen treatment (R² > 0.71) and negatively correlated with temperature at moderate and low oxygen concentrations (R² > − 0.84). MMS was significantly affected by temperature and oxygen and was significantly correlated with oxygen treatment (R² > − 0.91), but correlations with temperature were not as clear. In conclusion, oxygen and temperature interactions have significant effects on metabolic scope and growth rates of fish, well above the accepted hypoxia threshold of 2.00 mg/L and MMS has proved a useful estimator of the metabolic scope of the organism within an environment.     

Effects of food concentration on clearance rate and energy budget of the Arctic bivalve Hiatella arctica (L) at subzero temperature

The influence of food concentration on clearance rate, respiration, assimilation, and excretion at −1.3 °C was studied on individuals of the bivalve Hiatella arctica (L.) from Young Sound, NE Greenland. Clearance rate, assimilation efficiency, respiration, and excretion rates were determined over a range of food concentrations using the microalga Rhodomonas baltica as food source. Physiological rates were generally low but responded significantly to increased food levels. Clearance rates and assimilation efficiency were reduced at increased food levels, whereas respiration and excretion increased. Assimilation efficiency was generally high, which may be an adaptation to the low food concentration during most of the year in NE Greenland. Low filtration rates limited ingestion rates and resulted in a low maximum assimilation of 3 J h⁻¹. Despite the low food intake, very low food concentrations were required for individual specimens to obtain a positive energy budget. Predicted growth based on rates of assimilation and respiration were compared to published estimates of annual growth in Young Sound. We estimate that 3 weeks of growth in the laboratory under optimal food conditions could match annual growth in situ. We interpret this as evidence that food limitation is the primary impediment to growth in this Arctic population.     

Brown shrimp (Crangon crangon, L.) functional response to density of different sized juvenile bivalves Macoma balthica (L.)

Variability in infaunal bivalve abundance in the Wadden Sea is largely determined by recruitment variability. Post-settlement, but pre-recruitment bivalve mortality is high and related to the occurrence of their most abundant predator, the brown shrimp Crangon crangon. To investigate if the mortality patterns of newly settled bivalves can be explained by the foraging behavior of brown shrimp, we carried out experiments on shrimp functional response to three size classes of juveniles of the Baltic Tellin Macoma balthica. The functional response curves for all three prey sizes (0.62 mm, 0.73 mm, and 0.85 mm) were the hyperbolic Holling's type II. The attack rate was highest for the smallest prey size (a = 0.31, medium and large prey a = 0.22); the handling time was longest for the largest prey size (T_h = 29 s, small and medium prey T_h = 15 s). Thus, a large body size is advantageous for the bivalves over the whole density range. Knowledge of individual foraging behavior is needed to model predation mortality of bivalves. The consumption rates in the experiment were theoretically high enough to account for M. balthica mortality in the field.     

Seasonal growth dynamics of Laurencia papillosa and Gracilaria coronopifolia from a highly eutrophic reef in southern Taiwan: temperature limitation and nutrient availability

Both field and laboratory studies were used to investigate the effects of temperature limitation and nutrient availability on seasonal growth dynamics of Laurencia papillosa and Gracilaria coronopifolia from a nearshore coral reef in the southern tip of Taiwan during 1999-2000. L. papillosa was a summer blooming alga abundant in August-November and G. coronopifolia was abundant year round except April-May. L. papillosa blooms in the summer were attributed to its preference for high temperatures and highly sensitivity to low temperatures. A wider temperature range and a significant stimulation of growth by high N inputs can explain the appearance of G. coronopifolia year round and also its maximum growth in November-March. Levels of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) in water column were extremely high, but the growth of these two rhodophytes still suffered nutrient limitation that the type and severity of nutrient limitation were variable over time and also between two species. The growth of L. papillosa was limited by P in the early growth stage (August-September) as indicated by decreased tissue P contents, increased C/P and N/P molar ratios and increased alkaline phosphatase activity (APA) and in the later growth stage, it was subjected to N-limitation, evidenced by decreased tissue N contents and C/P and N/P molar ratios and increased tissue P contents. The growth of G. coronopifolia was also P-limited as indicated by increased tissue N contents and concomitantly decreased tissue P contents, while marked drops in tissue P contents below the subsistence level in mid September and December 1999 reveal severe P limitation, which was supported by increased alkaline phosphatase activity. Higher critical nutrient contents and nutrient thresholds for maximum growth of G. coronopifolia suggest that G. coronopifolia faced more frequent nutrient limitation compared to L. papillosa. In conclusion, the results from these laboratory and field studies provide evidence that the seasonal abundance of L. papillosa and G. coronopifolia from southern Taiwan was determined by seasonal variations in seawater temperatures and nutrient concentrations as well as different physiological growth strategies. Seawater temperature and nutrient availability were important determinants of seasonal abundance of L. papillosa while the seasonal abundance of G. coronopifolia was influenced by nutrient availability.     

Effect of somatic and otolith growth rate on stable isotopic composition of early juvenile cod (Gadus morhua L) otoliths

The relative amounts of the stable isotopes of carbon and oxygen in fish otoliths can be used to reveal the environmental history experienced by the fish. This requires that the relative amounts of the isotopes are deposited in equilibrium with the surrounding environment, or that the offset from this equilibrium is known and can be quantified. It is known that carbon isotopes in biogenic carbonates are a mixture of carbon from the seawater and metabolically derived carbon, but the effect of the somatic growth rate of the fish is still unclear. The possible effect of otolith growth rate and fractionation of both carbon and oxygen isotopes are also not established. We carried out a controlled laboratory experiment where we reared cod (Gadus morhua L.) larvae and early juveniles at two temperatures (6 and 10 °C) and generated different growth rates within each temperature by manipulation of prey levels. The otoliths of the resulting fish were analysed for carbon and oxygen isotopes. We found no effect of otolith precipitation rate on fractionation of either carbon or oxygen isotopes. However, there was a depletion of ¹³C in the otoliths of fish with elevated metabolism. The proportion of metabolically derived carbon in the otoliths was estimated to be 28-32%. Our results suggest that measurements of oxygen isotopes in otoliths can be a reliable tool to estimate ambient temperature since the oxygen isotopes seem to be deposited in the otoliths independently of kinetic and metabolic effects. Fractionation of carbon isotopes in otoliths on the other hand can give valuable insight into metabolism and feeding pattern of fish.     

Survival,osmoregulation and ammonia-N excretion of blue swimmer crab, Portunus pelagicus, juveniles exposed to different ammonia-N and salinity combinations

Ammonia-N toxicity to early Portunus pelagicus juveniles at different salinities was investigated along with changes to haemolymph osmolality, Na⁺, K⁺, Ca²⁺ and ammonia-N levels, ammonia-N excretion and gill Na⁺/K⁺-ATPase activity. Experimental crabs were acclimated to salinities 15, 30 and 45‰ for one week and 25 replicate crabs were subsequently exposed to 0, 20, 40, 60, 80, 100 and 120 mg L^− 1 ammonia-N for 96-h, respectively. High ammonia-N concentrations were used to determine LC₅₀ values while physiological measurements were conducted at lower concentrations. When crabs were exposed to ammonia-N, anterior gill Na⁺/K⁺-ATPase activity significantly increased (p < 0.05) at all salinities, while this only occurred on the posterior gills at 30‰. For crabs exposed to 20 and 40 mg L^− 1 ammonia-N, both posterior gill Na⁺/K⁺-ATPase activity and ammonia-N excretion were significantly higher at 15‰ than those at 45‰. Despite this trend, the 96-h LC₅₀ value at 15‰ (43.4 mg L^− 1) was significantly lower (p < 0.05) than at both 30‰ and 45‰ (65.8 and 75.2 mg L^− 1, respectively). This may be due to significantly higher (p < 0.05) haemolymph ammonia-N levels of crabs at low salinities and may similarly explain the general ammonia-N toxicity pattern to other crustacean species.     

Effects of temperature, salinity, and irradiance on the growth of the dinoflagellate Akashiwo sanguinea

The effects of temperature, salinity, and irradiance on the growth of the dinoflagellate Akashiwo sanguinea were examined in the laboratory. The irradiance at the light compensation point (I₀) was 14.40 μmol m^− 2 s^− 1 and the irradiance at growth saturation (I_s) was 114 μmol m^− 2 s^− 1. We exposed A. sanguinea to 48 combinations of temperature (5-30 °C) and salinity (5-40) under saturating irradiance; it exhibited its maximum growth rate of 1.13 divisions/day at a combination of 25 °C and salinity of 20. A. sanguinea was able to grow at temperatures from 10 to 30 °C and salinities from 10 to 40. This study revealed that A. sanguinea was a eurythermal and euryhaline organism; in Japan it should have formed blooms in early summer, when salinity was relatively low. In addition, it was noteworthy that A. sanguinea had markedly cold-durability, retaining the motile form of vegetative cells for more than 50 days at 5 °C and at salinities of 25-30.     

A simple equation for describing the temperature dependent growth of free-floating macrophytes

Temperature is one of the most important factors determining growth rates of free-floating macrophytes in the field. To analyse and predict temperature dependent growth rates of these pleustophytes, modelling may play an important role. Several equations have been published for describing temperature responses of macrophytes and algae. But they are often complex or are only applicable in a limited range of temperatures. In this paper, we present a simple three-parameter equation for describing the temperature dependent growth rates of pleustophytes. The equation that we developed is tested using results from laboratory growth experiments conducted with three different species of pleustophytes (Lemna minor, Salvinia molesta and Azolla filiculoides). The equation is simple and demonstrates reliable fits (adjusted R² reaching from 0.89 to 0.95). Additionally, our equation primarily uses parameters of biological significance, resulting in estimates of useful cardinal temperatures (minimum and maximum).     

Development and mortality of the first naupliar stages of Eurytemora affinis (Copepoda, Calanoida) under different conditions of salinity and temperature

As a prevalent species complex in temperate estuaries and salt marshes of the Northern Hemisphere, populations of Eurytemora affinis that inhabit these environments must be adapted to salinity fluctuations. Some populations have invaded freshwater environments. In this work, we focus on the combined effects of temperature and salinity fluctuations on mortality rates and development time of the first naupliar stages under starvation. Two temperatures (10 and 15 °C) and eight salinities, ranging from 0 to 35 psu are investigated. We show (i) that among all experimental conditions the optimal temperature and salinity for naupliar survival and development are 15 psu and 15 °C, and (ii) that only the most extreme salinities (i.e. 0 and 35 psu) have a negative effect on naupliar survival. Nauplii develop faster and reach a higher developmental stage at 15 than at 10 °C, independent of salinity. The relevance of this metabolic adaptive pattern is discussed in the general framework of in situ behavior, tidal forcing and biogeographic variability, as well as the potential sources of the observed individual variability.     

Growth of Nyctiphanes (Euphausiacea) on different diets

To determine the effects of diet on the growth rate of Nyctiphanes australis (Euphausiacea), metanauplii were reared to mature adults in the laboratory. Sibships (siblings from the same mother) were raised on different food items collected from the field and cultured in the laboratory. A sibship was divided at the calyptopis stage and 50% of the siblings were fed one of three experimental diets (Thalassiosira, Heterocapsa, or Phaeocystis); the balance of the siblings were fed a control diet of Tetraselmis chuii and Artemia larvae.The growth rate of siblings was not altered by the different diets. Siblings developed asynchronously, however, from egg to adult.Some animals were always at a more advanced developmental phase and by day 100, up to 25% larger than their siblings (p<0.001). A possible implication of this result is that the larval growth of N. australis is strongly influenced by genotype.     

Effects of water temperature on growth and sex ratio of juvenile Nile tilapia Oreochromis niloticus (Linnaeus) reared in geothermal waters in southern Tunisia

Growth of juvenile Nile tilapia, Oreochromis niloticus (Maryut strain) was studied under laboratory conditions. Four thermal regimes (22, 26, 30, and 34 °C) were tested on 480 20-day-old fry.     

Thermal performance of juvenile Atlantic salmon (Salmo salar L.) of Baltic Sea origin

1. The effect of temperature on food intake, growth and energetic growth efficiency of Atlantic salmon of Baltic Sea origin was studied in tanks.     

The reproductive response of the sea urchins Paracentrotus lividus (G.) and Psammechinus miliaris (L.) to a hyperproteinated macrophytic diet

The sea urchins Paracentrotus lividus and Psammechinus miliaris are submitted to the same environmental conditions in the Bay of Brest. The relationship between seasonal changes in food source quality and their gonad production was investigated in reproducing experimentally these conditions. In a first stage two macroalgae (Palmaria palmata and Laminaria digitata) were tested. P. miliaris showed a stronger preference for P. palmata and over a year-long experiment both urchins progressively preferred P. palmata. Seasonal variations in the chemical composition of P. palmaria were observed in the Bay of Brest: total carbohydrates were important and the relative maximum (about 50%) was reached between February and August; the lipid level was low and had a relative maximum of about 1% in June and August. Total protein in P. palmaria was high compared to other seaweeds: the maximum value (25%) was observed in June, which was probably due to the maintenance of nitrogen nutrient in the bay.In the second stage of the study, seasonal changes in biochemical components of ingestion and absorption of the two sea urchins were followed in the laboratory using a monospecific diet of P. palmaria. The patterns of total carbohydrates and lipid absorption were very similar for both sea urchin species. Carbohydrates were absorbed strongly and uniformly, year round. Lipid absorption mimicked the lipid nutrient pattern in the food source. Only changes in protein absorption varied slightly between the two urchin species. Protein absorption was maximal for both species in February and June, but the quantity of absorbed protein was significantly higher in P. miliaris than in P. lividus during February. This increase was concomitant with protein storage in the sea urchin gonads, which peaked in February for P. miliaris and in June for P. lividus. P. lividus had a higher gonad production efficiency, based on gonad yield. The comparison between in situ data and the experimental results suggests that an algal diet more nitrogenous than the in situ algal food source would benefit the herbivorous P. lividus, rather than the more omnivorous species P. miliaris. Although P. milaris has been described as a species with large gonad production potential, P. lividus appears to be a more suitable species for echiniculture conditions.     

Zooid size and growth rate of the bryozoan Cryptosula pallasiana Moll in relation to temperature, in culture and in its natural environment

The size of cheilostome bryozoan zooids has been widely discussed for its potential in inferring palaeotemperatures, based on correlations between zooid size and temperature. Studies in both the natural environment and under experimental laboratory conditions have shown that an increase in temperature significantly decreases zooid size in a range of bryozoan taxa. In order to test the effect of temperature on zooid size, the cheilostome bryozoan Cryptosula pallasiana was for the first time successfully cultured under laboratory conditions. C. pallasiana was grown at 14 °C and 18 °C using Rhodomonas sp. as a food organism. Zooid size, tentacle number and growth rate were measured over a period of 26 days. For comparison, zooids from colonies of C. pallasiana collected from the natural environment were measured in winter and summer months. Results showed that colonies grown in laboratory culture had significantly longer and wider zooids at 14 °C than at 18 °C. The specific growth rate of C. pallasiana doubled from 14 °C to 18 °C. Comparison of tentacle number in culture showed a significantly higher value at lower temperatures. This may be related to differing food availability, longer polypide life spans, or a shift of energy use at colder temperatures. In nature the zooids were significantly longer in colonies sampled in July than in January, a clear difference from laboratory results. The utility of cheilostome Bryozoa as indicators of environmental change and their potential for studies of paleotemperature are highlighted.     

Metabolic readjustment in juvenile South African abalone (Haliotis midae) acclimated to combinations of temperature and dissolved oxygen levels

When ectotherms are exposed to high temperatures, cellular oxygen demand increases. When oxygen demand exceeds oxygen availability, animals may experience functional hypoxia regardless of environmental oxygen levels.     

Dormancy of Medicago marina (L.) seed

Medicago marina (L.) is a Mediterranean species whose seeds show strong dormancy that prevents germination. We used an integrated approach of physiological analyses and proteomics to investigate the mechanisms that control M. marina dormancy/germination and that underlie stress tolerance. First, we evaluated the effects on dormancy breaking of the following treatments: mechanical scarification, freezing at −20 °C, storage for 4 months and heating at 100 °C for 1 h. Mechanical scarification and freezing were the most effective treatments in overcoming dormancy. The role of abscisic acid (ABA) in M. marina dormancy was studied by ELISA immuno-enzymatic assay. The ABA content of germinated and non-germinated mature (control) and treated seeds was determined. The level of ABA was higher in treated seeds than in control seeds; the most significant increase occurred in the heated seeds. A comparison of the ABA level in the germinated, control and treated seeds suggests that different mechanisms modulate ABA content in response to different stresses, and that a specific ABA-signalling pathway regulates germination. Proteomic analysis revealed 46 proteins differentially expressed between treated and untreated seeds; 14 of these proteins were subsequently identified by mass spectrometry. Several of the proteins identified are important factors in the stress response, and are involved in such diverse functions as lipid metabolism, protein folding and chromatin protection. Lastly, an analysis of the phosphoproteome maps showed that the function of many proteins in seeds subjected to temperature treatment is modulated through post-translational modifications.     

Coexistence of Abies alba (Mill.) - Fagus sylvatica (L.) and climate change impact in the Iberian Peninsula: A climatic-niche perspective approach

Abies alba Mill. (European silver fir) and Fagus sylvatica L. (beech) are Eurosiberian species dispersed over the Iberian Peninsula. Climate change predictions indicate a rise in temperature and a decrease in precipitation in this region, threatening the future existence of these species. In the present study we analyzed the future topo-climatic suitability of Abies alba and Fagus sylvatica and the mixed forests of these two species, using the General Linear Models technique and data from the third National Forest Inventory (Ministerio de Agricultura PyA, 2007). We considered two modeling approaches based on niche theory: modeling community (Abieti-Fagetum) and overlapping individual species models. General trends showed an overall decrease in both species’ topo-climatic suitability and indicated that the Pyrenees will play a crucial role as a climatic refuge. The modeling approaches markedly differed, however, in their current and future spatial agreement. Despite good accuracy results, community modeling through co-occurrence does not encompass the environmental space of individual species prejudicing future assessments in new environmental situations, suggesting a need for future studies in community modeling.