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1.
The influence of environmental parameters (temperature, salinity and available food) on the condition, reproductive activity and biochemical composition of a native population of Ostrea edulis L. in San Cibran (Galicia, Spain) was studied between September 1988 and December 1989. Histological preparations of gonads showed that gametogenesis started when temperature was at its lowest in winter. The water temperature in San Cibran never fell low enough to interrupt it. Gametogenesis proceeded slowly and spawning took place in May–June, although the predicted time of ripening was early March. Salinity in San Cibran was relatively stable throughout the year; it did not seem to have any influence on gametogenesis. Available food appeared to be a very important factor in controlling gonad growth, once gametogenesis was initiated. The major concentration of suspended organic particulate matter was present in the spring at the time of rapid gonadal maturation. Only one spawning period was observed. Larvae were released when the food in the water was high. Seasonal changes in the main biochemical components of this oyster were determined for a standard individual. Lipids and carbohydrates presented a similar time-course whereas proteins were constant. When food was abundant, energy reserves were built up. Spawning produced a decrease in biochemical constituent levels, and recovery coincided with the phytoplankton bloom. The stored reserves, mainly lipids, were used to overcome a state of energy imbalance in late autumn associated with low food availability. Results show this oyster to be an opportunist organism which concentrates its reproductive effort during a short period of favourable conditions and which is directly dependent on nutritive availability in the environment.  相似文献   

2.
Oxygen consumption of 3 species of Patella was measured in air and water at various temperatures. Measurements at constant temperature over a full tidal cycle showed no tidal or light-dark rhythms. Measurements under conditions simulating natural tidal, temperature and day-night cycles allowed calculation of daily respiratory energy budgets. P. cochlear occurs low on the shore, but experiences a food shortage due to intense intraspecific competition. Its rate of respiration is moderate, but metabolic expenditure is kept low because exposure to air is brief and body temperatures seldom rise above 23°C. P. cochlear has a respiratory rate-temperature (R-T) curve which peaks at 20°C and forms a plateau between 20° and 32.5°C. The midshore P. oculus has abundant food and adopts an exploitative strategy. Growth rate is very high, and this high turnover of energy is linked with a high metabolic rate, high Q10 (temperature coefficient) values, high body temperatures during the day-time low tide, and a respiratory R-T curve peaking at 32.5°C. Small P. oculus occur mainly in intertidal pools and respire faster in water, while larger individuals occur on bare rocks and respire faster in air over the upper temperature range. In contrast, the upper-shore P. granularis has little food, and conservation of energy is essential, particularly as its growth rate is moderate and its reprocurve output high. Respiratory losses are reduced by suppression of the R-T curve and low Q10 values, resulting in relative independence of temperature. Small P. granularis occur low on the shore and respire slower in water. Larger individuals occur at high levels due to migration, and respire slower in air. This further reduces respiratory energy losses. The patterns of respiration in these 3 species are thus related to food availability, resulting in exploitative or conservationist strategies.  相似文献   

3.
Juvenile oysters (Crassostrea gigas) (produced in November 2009) reared under uniform hatchery conditions for 4 months were selected for extreme growth rate differences by repeatedly taking larger and smaller individuals to achieve weight differences >30× between fast (F) and slow (S) growers. The physiological basis of differential growth was analyzed in experiments in June 2010, where components of energy gain (clearance and ingestion rates and absorption efficiency), energy loss (metabolic rates) and resulting scope for growth (J h?1) were compared for groups of F and S oysters fed three different ration levels (≈0.5, 1.5 and 3.0 mg of total particulate matter L?1). In both F and S oysters, a higher food ration promoted asymptotic increases in energy gain rates through regulatory adjustments to clearance rates, which maintained similar absorption efficiencies across the food concentrations. No significant differences were found between growth groups in mass-specific physiological rates (i.e., per unit of body mass). However, the scaling of these rates to a common size in both groups using allometric coefficients derived for C. gigas revealed higher energy gain rates coupled with lower metabolic costs of growth in fast growers. Thus, appropriate size-standardization is essential in accounting for observed differences in growth rate. Present results are in accordance with previous reports on other bivalve species on the physiological processes underlying endogenous growth differences, suggesting that the same interpretation can be applied to the extremes of these differences.  相似文献   

4.
On the eastern shore of Nova Scotia late summer atmospheric systems cause upwelling of shelf water; the associated temperature variations of 10 °C with a 6 to 8 d period are comparable in magnitude to the seasonal variation. A laboratory study was undertaken to assess the effects of these temperature fluctuations on sea scallop (Placopecten magellanicus) growth and metabolism. In a factorial design, scallops were subjected to constant (10 °C) or a variable (6 to 15 °C) 8 d temperature cycle, and either a low (seston in filtered seawater) or high (seston supplemented with cultured phytoplankton) food diet. During the 48 d experiment scallop mortality was low and growth positive in all treatments. Shell and total tissue growth rate did not differ between temperature treatments, but growth in the high food treatments was 40 to 50% higher than in the low food treatments. However, soft tissue (excluding adductor) growth did show a temperature treatment effect; growth rates were significantly higher in the fluctuating temperature treatment, due in part to greater gonad development. Weight-standardized rates of scallop oxygen consumption (V sO2 , μmol O2 g−1 h−1) were 20 to 25% higher in high food than in low food treatments, consistent with the expected increase in respiration due to the higher growth rates. Scallop metabolism did not acclimate to the fluctuating temperature cycle; V sO2 and ammonium excretion (V sNH+ 4, μmol O2 g−1 h−1) remained dependent on ambient temperature throughout the experiment. V sNH+ 4 Q10 (2.77) was higher than V sO2 Q10 (2.01) which was reflected in a decrease in the O:N ratio at 15 °C, indicating a shift toward increased protein catabolism and a stressed state. At 10 °C, V sO2 and V sNH+ 4 in the variable temperature treatments were 15 to 18% lower than in the constant temperature treatments, a difference that was not detected in growth measurements. Results demonstrate that the metabolism of Placopecten magellanicus, unlike some bivalve species, is tightly coupled to fluctuations in ambient temperature. Although an absence of compensatory acclimation had a minimal effect on growth in this study, if high temperatures were combined with low food conditions a reduction in scallop production could result. Received: 23 June 1998 / Accepted: 8 February 1999  相似文献   

5.
Mytilus edulis L. occupies a habitat in eastern Newfoundland, Canada, which is characterised by low temperatures and a lower concentration of particles in suspension than is found in estuarine locations. Gametogenesis occurs in the spring, and energy reserves from the previous year are not utilised in the synthesis of gametes. Oxygen uptake is not elevated during the winter, in contrast to most European populations, which undergo gamete development at that time. There is little seasonal variation in clearance rate. This may be attributable in part to the absence of the high particulate load which has been shown to depress feeding activity in some estuarine populations. Energy balance is positive at all times of the year, and conversion efficiency is high, suggesting that conditions are favourable. A number of physiological comparisons are made between Newfoundland mussels and those from European waters.  相似文献   

6.
Meretrix meretrix L. was held in the laboratory under simulated natural conditions to measure specific physiological parameters of its energy budget. O2 consumption rate, NH3 excretion rate (NR), ingestion rate, faeces excretion rate and scope for growth (SFG) were negatively related in an exponential manner to the fresh weight of the clams at all water temperatures, while almost all metabolic rates of the clams were positively related in an exponential or e-exponential manner with water temperature. However, the co-relationship between metabolic rates and water temperature was not as close as that between metabolic rates and fresh weight of the clam. The combined effect of fresh weight and water temperature was observed on all metabolic rates except for NR and SFG. At all culture temperatures and for all fresh weights of clams used, respiration took the largest percentage of ingested energy (41.5–51.2%), faeces excretion was second (31.0–42.3%), growth third (12.1–15.5%) and urine production last (2.1–5.6%).  相似文献   

7.
At least 19 hypotheses have been proposed to explain the evolutionary significance of avian hatching asynchrony, and hatching patterns have been suggested to be the result of several simultaneous selective pressures. Hatching asynchrony was experimentally modified in the black kite Milvus migrans by manipulating the onset of incubation during the laying period. Delayed onset of incubation reduced egg viability of first-laid eggs, especially when ambient temperature during the laying period was high. Brood reduction (nestling mortality by starvation or siblicide) was more commonly observed in asynchronous nests. The growth rate was slower in synchronous broods, probably due to stronger sibling rivalry in broods with high size symmetry. Last-hatched chicks in synchronous broods fledged at a small size/mass, while in control broods, hatching order affected growth rates, but not final size. Brood reduction, variable growth rates, and the ability to face long periods of food scarcity are probably mechanisms to adjust productivity to stochastic food availability in a highly opportunistic predator. The natural pattern of hatching asynchrony may be the consequence of opposing selective forces. Extreme hatching synchrony is associated with slow growth rates, small final size of last-hatched chicks, and low viability of first-laid eggs, while extreme hatching asynchrony is associated with high mortality rates. Females seem to facultatively manipulate the degree of hatching asynchrony according to those pressures, because hatching asynchrony of control clutches was positively correlated with temperature during laying, and negatively correlated with the rate of rabbit consumption. Received: 25 October 1999 / Revised: 30 May 2000 / Accepted: 25 June 2000  相似文献   

8.
We investigated the feeding habits and growth of juvenile stone flounder (Platichthys bicoloratus) in several estuarine nurseries in Sendai Bay, Japan. Prey abundance and composition and juvenile diet varied largely among sites. However, polychaete palps (mostly Pseudopolydora kempi) and bivalve siphons (mostly Nuttallia olivacea) were positively selected and frequently consumed by juveniles, indicating the generality of sublethal feeding of juvenile stone flounder in estuarine nurseries. Recent growth rates determined by otolith microstructure analyses were dependent on juvenile body size and water temperature, but independent of juvenile density and food abundance. Growth rates were nearly maximal from March to May, suggesting that food conditions are nearly optimal in these estuarine nurseries. Sublethal tissue cropping of benthic invertebrates is thought to contribute largely to these high growth rates.  相似文献   

9.
Omnivorous feeding behavior of the Antarctic krill Euphausia superba   总被引:5,自引:0,他引:5  
Feeding experiments were conducted at Palmer Station from December 1985 to February 1986 to examine the potential role of copepod prey as an alternative food source for Euphausia superba. Copepod concentration, copepod size, phytoplankton concentration, the duration of krill starvation and the volume of experimental vessels were altered to determine effects on ingestion and clearance rates. Krill allowed to feed on phytoplankton and copepods in 50-litre tubs showed greatly increased feeding rates relative to animals feeding in the much smaller volumes of water traditionally used for krill-feeding studies. Clearance rates on copepods remained constant over the range of concentrations offered, but clearance rates on phytoplankton increased linearly with phytoplankton concentration. Feeding rates increased when larger copepods were offered and when krill were starved for two weeks prior to experiments. Clearance rates of krill feeding on copepods were higher than, but not correlated with, their clearance rates on phytoplankton in the same vessel. E. superba may have a distinct mechanism for capturing copepods, perhaps through mechanoreception. Although our observed clearance rate of 1055 ml krill-1 h-1 indicates that krill can feed very efficiently on copepod prey, such feeding would meet less than 10% of their minimum metabolic requirements at the typical copepod concentrations reported for Antarctic waters. However, substantial energy could be gained if krill fed on the patches of high copepod concentrations occasionally reported during the austral summer, or if krill and copepods were concentrated beneath the sea ice during the winter or spring months. Our results, indicating efficient feeding on zooplankton and higher clearance rates on phytoplankton than previously believed, represent a step towards balancing the energy budget of E. superba in Antarctic waters.  相似文献   

10.
Physiological responses of suspended cultured mussels, Mytilus edulis L., in two Scottish sea lochs (Lochs Etive and Leven) were investigated in their native and transplanted environments, after 15 d, 4.5 mo and 1 yr acclimatization, during the main growing season of May to September 1992. These measurements were integrated by means of the balanced energy equation, and scope for growth was calculated to assess the performance of each stock. Transplanted mussels showed clear signs of stress during the first 15 d after transfer, with low clearance rates and energy retention and high rates of respiration and nitrogen excretion. There were significant differences in some of the physiological responses (clearance, respiration and excretion rates), scope for growth and growth efficiency between the native populations, with the responses of mussels in Loch Etive being more favourable than those in Loch Leven. With newly transplanted mussels after 15 d acclimatization, almost all these measurements also differed significantly from native mussels in their host site and the original stocks but, with the exception of ammonia excretion rates, all the variables of cross-transplanted mussels after 4.5 mo acclimatization were the same as those of the native stock at the host site. Good agreement between observed long-term growth rates and estimated scope for growth suggests that, like growth rate, differences in physiological responses are mainly controlled by environmental factors; i.e., stock or origin had no significant influence on variations in physiological response (except ammonia excretion). The results further indicate that scope for growth estimated during the main growing season can be used to assess the actual growth rate and to compare sites for on-growing.  相似文献   

11.
D. Rosell  M. J. Uriz 《Marine Biology》1992,114(3):503-507
Massive specimens of Cliona viridis, collected off the coast of Blanes (North-Western Mediterranean Sea) in January 1987, were exposed to different light (natural day-night irradiance/constant darkness) and substrata (calcareous/siliceous) conditions to assess their influence on growth, survival and attachment rates. Sponges cultured under natural irradiance displayed higher growth rates with increasing temperature; those cultured in the dark did not respond to increased temperature, but adapted faster to laboratory conditions. Differences in growth rates between these two culture conditions are ascribed to the presence of a healthy symbiotical zooxanthellae population on individuals cultured under conditions of natural irradiance. Attachment rates of the cut sides of the sponges which were in direct contact with the substratum, also increased with increasing temperature, whilst sponge survival was not significantly dependent on temperature. The chemical nature of the substratum clearly affected survival rates, which were higher on calcified than on siliceous substrata.  相似文献   

12.
Experiments were carried out to determine growth and development rates of the herbivorous copepod Calanus finmarchicus (Gunnerus) under natural conditions during the phytoplankton spring bloom in the northern North Sea. From 28 April to 25 May 1983 copepodite stages I, IV and V were incubated for a 3-d period on board a ship in vessels with naturally occurring phytoplankton or cultured algae as food. Highest rates of growth and development were achieved while the diatom Chaetoceros sp. was the dominant phytoplankton organism. These rates decreased considerably when this chain-forming diatom was succeeded after one week by the small-celled diatom Thalassiosira conferta. Again one week later, during the bloom of the succeeding colonial microflagellate Corymbellus aureus, copepodite stage IV still managed to maintain moderate rates of growth and development, but these rates dropped to almost zero in CV, suggesting the start of a resting stage. Nevertheless, brood collected from this generation and from Calanus helgolandicus (Claus) was raised in the laboratory to the adult stage at high speed. Since temperature and the total phytoplankton concentration in the sea remained almost constant it seems that the retardation and arrestment of growth and development were an immediate response to a qualitative change of the food composition related to the successive blooms of different algal species.  相似文献   

13.
The amount of food and when it is available affect both the timing of reproduction and the number of gametes produced by purple sea urchins, Strongylocentrotus purpuratus. To investigate this further, the effects of food availability on feeding rates, gonad growth, and gamete development were examined in S. purpuratus collected from the Point Loma kelp forest near San Diego, California, USA (32.69° N, 117.26° W) in September (Fall) 2007, and February (Spring) and July (Summer) 2008, using laboratory mesocosms. Each seasonal laboratory feeding experiment lasted 3 months, and different levels of food availability were established with different feeding frequencies (from 1 to 7 days week−1). Gonad tissues of male and female urchins were staged at the end of each experiment using histological analyses. Reduced food availability resulted in increased daily consumption rates, especially in the Fall when gamete development began. Food limitation at this time resulted in failure to produce viable gametes, suggesting there is a critical period early in gonad development when food limitation affects reproductive competency. Food limitation later in gonad development did not stop viable gamete production, although it did reduce gamete output.  相似文献   

14.
The population of Corophium multisetosum Stock, 1952 in Areão displayed a semiannual, iteroparous life history. Mean longevity was ~6?mo, with the estimated life span longer for overwintering individuals born in autumn than for individuals born in spring. Length-frequency data indicated that the length increment per moult is probably higher in males than females; however females moulted more frequently and achieved a larger body size. Preliminary growth rates were 100?μm?d?1 for juveniles and 19 to 29?μm?d?1 for mature females, with the lower values occurring during the winter. It was estimated that under favourable conditions females may attain reproductive size and mature within 1?mo. Although incubating females were present all year round, recruitment occurred in spring, almost ceased during the summer, peaked in autumn, and decreased again during the winter. Extreme temperatures and very low salinities during winter and summer may have deterred breeding, while moderate temperatures (15 to 20?°C) and salinities > 1?psu in spring and autumn were apparently favourable for reproduction. The unfavourable summer conditions constrained breeding and synchronised the timing of reproduction. In late-autumn and during the winter, as temperature decreased and brooding time increased, synchrony was progressively lost. Brood size varied as a function of embryonic developmental stage, size of incubating females, and season. The life-history pattern and reproductive features of C. multisetosum in Areão are closely related to temperature and salinity; other environmental conditions such as oxygen content of the water and food availability may also be relevant.  相似文献   

15.
More than a half century ago, the British ornithologist David Lack suggested that parent birds may use brood reduction to track uncertain food, a process facilitated by the asynchronous hatching of their young. Lack sketched the logic of asymmetric sibling rivalry: the phenotypic handicap imposed upon last-hatched marginal offspring renders their growth and survival conditional upon uncertain ecological conditions while buffering first-hatched core offspring from the inimical effects of overcrowding during periods of stringency. Though subjected to numerous indirect tests in short-term studies, the central prediction of Lack's hypothesis - that parents use marginal offspring to track unpredictable brood-rearing conditions and thus achieve a secondary adjustment of clutch size - has never been tested directly. Here we present the results of a 7-year study of marsh-nesting red-winged blackbirds (Agelaius phoeniceus) showing that (1) brood size tracks interannual variability in growth and survival of nestlings, (2) the growth and mortality of marginal but not core offspring is contingent upon stochastic environmental conditions (mean air temperature) during brood rearing, (3) the mortality of marginal but not core offspring is strongly affected by developmental uncertainty in the form of both experimental and natural alterations of brood size, (4) the phenotypic handicap of hatching asynchrony buffers core offspring from poor growth conditions, but (5) its effects upon marginal nestlings are reversible when growth conditions are favourable and especially when brood size is reduced either experimentally or via hatching failure. The presence of marginal offspring ensures that blackbird parents are not left with a too small brood when brood-rearing conditions are favourable. Parents create two castes of progeny: marginal offspring that are strongly affected by both ecological and developmental stochasticity, and core offspring that are not.  相似文献   

16.
Postlarval and juvenile Penaeus merguiensis de Man from the Embley River estuary on the north-eastern Gulf of Carpentaria were sampled every 2 wk from September 1986 until August 1989, using a small beam trawl. Settlement of planktonic postlarvae peaked during the pre-wet season (October to December), and declined through the wet season (January to March). Using length-frequency analysis between 12 and 14 cohorts of juvenile prawns were identified each year. Length-frequency analysis and modal progression were used to derive growth rates during the estuarine phase of the life cycle. Growth rates, which could be described by a linear model, ranged from 0.63 to 1.65 mm CL (carapace length) wk-1. Growth rates were positively influenced by water temperature and negatively influenced by prawn density. Salinity had no effect on growth rates. Prawns spent between 6 and 20 wk in the Embley River before emigrating offshore from the estuary. Weekly instantaneous rates of natural mortality (M) ranged from 0.23 to 0.94, and in general were lowest during the dry season (July to September) and highest during the pre-wet and wet seasons. Only temperature significantly influenced mortality rates, with mortality rates increasing with temperature. By projecting juvenile growth rates forward through time, we established which cohorts contributed to the offshore fishery each year. In 1987 and 1988 the April fishery consisted of prawns which had settled in the river before the end of January each year. Slow growth rates during the pre-wet season of 1988 meant that only cohorts that were settled before early December 1988 contributed to the fishery in April 1989. Whether a cohort contributes to the fishery depends on the settlement date, water temperature and prawn density.  相似文献   

17.
S. Choe 《Marine Biology》1971,9(1):31-37
Individuals of the oriental brown shrimp Penaeus japonicus Bate, were raised separately (1 shrimp per rearing cage) with surplus food, in almost dark, non-sediment conditions. Results were obtained regarding growth of each part of the body in conjunction with exuviation and molting cycle. Increases in carapace, body length and body weight conformed to the general pattern discribed by Hiatt (1948), with no difference in growth resulting from sex, or inflexion point in juvenile stage. The molting cycle of shrimp weighing 1.5 to 15 g was 6 to 17 days at a water temperature of 20° to 28°C. The molting cycle was prolonged in proportion to the size of the shrimp; shortened as the water temperature increased.  相似文献   

18.
We measured the clearance rates of the filter-feeding bivalve Corbicula fluminea over a period of 2?years. Strong seasonal variations, such as a 50-fold increase from February to July, were observed. These variations were only poorly linked to temperature, as they could be found at both the ambient field temperature and a constant temperature of 15°C. Instead, peaks in the filtration activity corresponded to the spawning activity. Additionally, a strong interannual variability with much lower clearance rates in 2009 than in 2008 was identified. The low clearance rates were linked to a preceding period of low winter temperatures close to the lethal temperature of 2°C and the associated reduced reproduction rates. Our findings demonstrate that other factors besides temperature and body mass can strongly affect clearance rates. These results should be considered when predicting the effects of changing temperatures on the ecosystem impact of filter-feeding bivalves.  相似文献   

19.
The dependency of in situ weight-specific fecundity of adult females (as egg production) and growth of juveniles (as somatic production) upon individual body weight in marine planktonic copepods was examined. A compilation was made of results where wild-caught individuals were incubated in natural seawater (often pre-screened to remove large organisms), at near in situ temperatures, over short periods of the order of 24 h. The results demonstrate that for the adult broadcast-spawning group weight-specific fecundity rates are dependent upon body weight, but independent of temperature. We postulate this may be the result of global patterns in available phytoplankton. Weight-specific growth rates are dependent upon individual temperature and body weight in juvenile broadcast-spawners, with rates declining as body weight increases. Sac-spawners have growth/fecundity rates that are independent of body weight in adults, juveniles, and both combined, but which are temperature-dependent. Globally applicable equations are derived which may be used to predict growth and production of marine copepods using easily quantifiable parameters, namely size-distributed biomass and temperature. Some of the variability in growth which remained unaccounted for is the result of variations in food quantity and quality in the natural environment. Comparisons of the rates compiled here over the temperature range 10 to 20 °C with previously compiled food-saturated rates over the same temperature interval, revealed that in situ rates are typically sub-optimal. Adults appear to be more food-limited than juveniles, adult rates in situ being 32 and 40% of those under food saturation in broadcasters and sac-spawners, respectively, while juvenile in situ rates are on average ∼70% of those at food saturation in both broadcasters and sac-spawners. Received: 18 September 1997 / Accepted: 13 May 1998  相似文献   

20.
The success that the putative alien species Oculina patagonica is able to survive under different environmental conditions may be benefiting its establishment and spreading along the Mediterranean Basin. Our objectives were to determine the response of this species, in terms of growth and bleaching, under different environmental conditions. Field data on colony growth and bleaching were obtained for a period of 18 months (from June 2010 to December 2011), in the Alicante Harbour (38°20′11″N, 00°29′11″W) and the Marine Protected Area of Tabarca (38°09′59″N, 00°28′56″W). Additionally, data on sedimentation rates, chlorophyll a concentration and organic matter were also collected. Moreover, the role of light over growth and bleaching of the coral was also studied with a field experiment. Our results showed that growth rates were similar among localities (eutrophic and oligotrophic environments), decreasing with increasing perimeter of the colony. Growth rates were at a minimum during cold months (13 °C) and enhanced during warm months until a threshold temperature; thereafter, bleaching was observed (>28 °C), being adverse for coral growth. In addition, light attenuation could act such as local stress, increasing the coral bleaching with the increase in seawater temperature. Our findings confirmed that O. patagonica has a broad tolerance to seawater temperature, irradiance and trophic water conditions, in addition to its ability to thrive through bleaching events, mainly in eutrophic environments, probably related to food availability.  相似文献   

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