Carbaryl-induced alterations in biochemical metabolism of the prawn,Macrobrachium malcolmsonii

The present study was performed to investigate the toxic impact of carbaryl on biochemical metabolism in the hemolymph, brain, hepatopancreas, gills and muscle of intermoult juveniles of the economically important prawn, Macrobrachium malcolmsonii. The concentration of glutathione S-transferase (GST) was found to be higher in test prawns when compared with controls. This suggests that a mechanism of detoxification was in operation to neutralise carbaryl toxicity. However, the toxic effect of carbaryl was not fully neutralised, and hence, alterations were recorded in basic biochemical metabolism of test prawns. The concentration of acetylcholinestrase (AchE) was found to be lower in test prawns than that of controls. Carbaryl toxicity resulted in utilisation of major biochemical constituents, such as total carbohydrate, glycogen, protein and lipid to generate required energy as an attempt to withstand the toxic stress. Glycogenolysis resulted in elevation of total free sugar level in the hemolymph of test prawns. While proteolysis led to elevation of total free amino acid level in test prawns. The content of total lipid have also been found lower in test prawns than that of controls. This suggests that carbaryl toxicity resulted in severe energy crises in test prawns. In the present study, toxic effects of carbaryl impair basic metabolic functions and hence pose a threat to the life of M. malcolmsonii.     

Experimental evaluation of the energy balance in Octopus vulgaris, fed ad libitum on a high-lipid diet

A complete energy balance equation was estimated for the common octopus Octopus vulgaris at a constant temperature of 20°C, fed ad libitum on anchovy fillet (Engraulis encrasicolus). Energy used for growth and respiration or lost with faeces and excreted ammonia was estimated, along with total energy consumption through food, for six specimens of O. vulgaris (with masses between 114 and 662 g). The energy balance equation was estimated for the specimens at 10-day intervals. During each 10-day interval, food consumed, body mass increase and quantity of faeces voided were measured. The calorific values of octopus flesh, anchovy flesh and faeces were measured by bomb calorimetry. Oxygen consumption and ammonia excretion rates were monitored for each specimen during three 24-h experiments and daily oxygen consumption and ammonia excretion were estimated. It was found that 58% of the energy consumed was used for respiration. The amount of energy invested in somatic and gonadal growth represented 26% of the total energy budget. The energy discarded through faeces was 13% of consumed energy. The estimated assimilation efficiency (AE) values of O. vulgaris feeding on anchovy (80.9–90.7%) were lower than the AE values estimated for other cephalopod species with different diets of lower lipid content such as crabs or mussels. Specific growth rates (SGR) ranged 0.43–0.95 and were similar to those reported for other high-lipid diets (bogue, sardine) and lower than SGR values found for low-lipid, high-protein diets (squid, crab, natural diet). Ammonia excretion peak (6 h after feeding) followed the one of oxygen consumption (1 h after feeding). The values of atomic oxygen-to-nitrogen (O:N) ratio indicated a protein-dominated metabolism for O. vulgaris.     

Profiles of acid and alkaline phosphatases in the prawn Macrobrachium malcolmsonii exposed to endosulfan

The present study was performed to determine the toxic effects of endosulfan on the quantitative and qualitative aspects of acid and alkaline phosphatases (ACP and ALP) in Macrobrachium malcolmsonii. Intermoult juvenile prawns were exposed to 32.0 ng/l of endosulfan for a period of 21 days. Samples were taken from the hemolymph, hepatopancreas, gills and muscle of test prawns on the 21st day. The content of ACP and ALP in the hepatopancreas of test prawns were found to be higher in comparison to respective controls. The levels of these enzymes in the hemolymph, gills and muscle of test prawns were found to be lower than in the same tissues of controls. In non-denaturing PAGE, phosphatases appeared as white bands. The intensity of white bands in the hepatopancreas of test prawns were found to be higher when compared to controls. In the hemolymph, gills and muscle of test prawns, the intensity of white bands were found to be lower in comparison to controls. The results of the present study suggest that endosulfan affects the quantity and quality of ACP and ALP in the tissues of M. malcolmsonii.     

Effects of Hg and Cu on hemocytes-mediated functions in the prawn,Macrobrachium malcolmsonii

Sublethal effects of Hg (9.6, 14.5 and 24.1 microg/l) and Cu (60.5, 90.8 and 150.5 microg/l) on the hemocytes-mediated functions in the juveniles of the economically important freshwater prawns, Macrobrachium malcolmsonii were investigated. The population of total hemocytes, percentile phagocytosis and superoxide anion production were found to be increased in test prawns exposed to the lowest sublethal concentration of these two metals in comparison to controls. This indicates the fact that a mechanism of host-defence was in an active state to encounter metal toxicity. The total hemocytes population, percentile phagocytosis and superoxide anion production were found to be decreased in test prawns exposed to intermediate as well as the highest sublethal concentrations of Hg and Cu when compared with controls. This suggests that high concentrations of both Hg and Cu have inhibitory effects on the immune functions of the hemocytes in the prawn, M. malcolmsonii.     

Nitrogen and energy loss via nonfaecal and faecal excretion in the marine teleost Lithognathus lithognathus

Nitrogen excretion and assimilation efficiencies of individual Lithognathus lithognathus (Cuvier 1830), a marine teleost from high energy surf zones in Algoa Bay, South Africa, were determined under laboratory conditions in 1985. Nonfaecal-nitrogen excreted by starved and fed L. lithognathus consists mainly of ammonia with urea and amino acids as secondary excretory products. Ammonia excretion rates were temperature dependant with the excretion rate of starved fish significantly lower than those of fed fish, at all three experimental temperatures. The mass component b of the mass/ammonia excretion equation was temperature independent and ranged from 0.651 to 0.700 and 0.589 to 0.635 for starved and fed fish respectively. The mean percentage of food energy lost via dissolved nonfaecal excretory products (exogenous plus endogenous) was 6.11±6.07%. Assimilation efficiencies ranged from 70.75 to 99.29% for dry matter and from 95.72 to 99.58% on an energy basis. The combined nonfaecal and faecal energy loss was calculated at 11.87% of the ingested energy. The benthic feeding ichthyofauna recycle 255 g total nitrogen per metre strip per year which constitutes 2% of total phytoplankton nitrogen requirements of the surf zone.     

阿维菌素对意大利蜜蜂(Apis mellifera L.)的毒性影响

通过单次饲喂高浓度阿维菌素药液以及连续饲喂亚致死浓度阿维菌素药液进行意大利蜜蜂的经口染毒,从而探讨阿维菌素对意大利蜜蜂的急性及慢性毒性影响。结果表明,阿维菌素对意大利蜜蜂急性经口毒性48 h半数致死剂量(48 h-LD50)为0.00700μg a.i.·蜂-1,慢性经口毒性240 h每日半数致死剂量(240 h-LDD50)为0.000308μg a.i.·蜂-1·天-1。在亚致死效应方面,0.0233 mg a.i.·L-1和0.0467 mg a.i.·L-1处理组在168 h后摄食量出现明显的减少,说明阿维菌素中毒已经严重影响意大利蜜蜂的觅食和摄食能力。同时,由于摄食量的下降以及阿维菌素的毒性作用,造成了0.0467 mg a.i.·L-1处理组意大利蜜蜂体重的大幅度下降,试验前后的体重变化率达到-54.84%。意大利蜜蜂爬行能力的测定结果显示,各处理组的爬行通过率均低于对照组,特别是0.0117 mg a.i.·L-1处理组、0.0233 mg a.i.·L-1处理组和0.0467 mg a.i.·L-1处理组(P0.05)。综上所述,阿维菌素对意大利蜜蜂的急性经口毒性为高毒,较高剂量染毒会引起意大利蜜蜂的直接死亡;此外,长期接触较低浓度的阿维菌素,一方面会损害意大利蜜蜂的运动能力,如爬行、飞行能力的减弱;另一方面意大利蜜蜂生理方面也会遭到威胁,表现为摄食量下降、体重减轻,甚至死亡。因此,在施用该农药时应尽量避开蜜蜂栖息地,同时避免在蜜源植株花期时施用。     

Nitrogen regeneration by the surf zone penaeid prawn Macropetasma africanus

Nitrogen excretion of individual Macropetasma africanus (Balss) from an exposed beach/surf zone in Algoa Bay, South Africa was monitored under laboratory and field conditions in relation to body mass, temperature and feeding during 1985. Excretion rate experiments were performed on starved prawns at 15°, 18°, 20° and 25°C, as well as on individuals fed on four different diets (mussel, fish, shrimp and natural diet) at 15° and 20°C. The ratios of the excreted compounds to total nitrogen excreted were similar for the four diets despite differences in their nitrogen content and in the amount of food consumed. At 15° and 20°C, ammonia excretion rates of fed individuals were four to seven times higher than in starved prawns. the excretion rates were not correlated with nitrogen content of diets. M. africanus recycles 1 557 g NH₄–N per metre strip per year or 1 832 g total nitrogen m^-1 yr^-1, which constitute 12 and 14%, respectively, of total phytoplankton requirements of the surf zone. This study indicates that large motile crustaceans, when abundant, can play an important role in nutrient recycling in turbulent marine environments.     

Energy investment in the annual reproduction cycle of female red porgy, <Emphasis Type="Italic">Pagrus pagrus</Emphasis> (L.)

Seasonal cycle in energy content of gonad, perivisceral fat, liver, and muscle was used to estimate the energy cost of spawning of female red porgy (Pagrus pagrus) from Buenos Aires coasts, Argentina. Spawning was observed primarily between November and January, although a low-intensity spawning was also observed at the beginning of this period. The energy required for gonad development of female red porgy (the difference between the maximum and minimum energy content of ovaries along the year) was 2,652 J g⁻¹ dry weight or 558 kJ. Female red porgy expend 22.8% of their total body energy (3,481 kJ) during the spawning period. Of this energy, relative contributions from different sources were as follows: ovaries 62.5% (496 kJ), perivisceral fat 17.8% (142 kJ), liver 10.3% (82 kJ), and muscles 9.4% (75 kJ). Female spawners lost about 7.2% (119 g) of their total body weight (1,654 g) in the spawning period. From the 7.2% of the total weight lost, female gonad represented a relative reduction of 73.8% (87.6 g), the perivisceral fat declined by 5.7% (6.8 g), the liver declined by 10.6% (12.5 g), and muscle tissue exhibited a 10% loss in total weight (11.9 g). Reproductive effort represented 7.6% of food energy, while resting metabolism accounted for almost 38% of food energy. Despite the fact that red porgy females feed throughout the entire spawning period, it is shown that between pre-spawning (September, water temperature 15°C) and mid-spawning (December, water temperature 19°C) they lost 45 and 38% of their muscle and liver lipids, respectively, and 89% of the perivisceral fat associated with the gut and body cavity. Red porgy used both their energy reserves and food energy during ovarian maturation. This asynchronous species have a strategy of a lower energy allocation and a higher dependence of food during the spawning time (late-spring and summer) for successful reproduction.     

Effects of ambient ammonia levels on blood ammonia, ammonia excretion and heart and scaphognathite rates of Nephrops norvegicus

During commercial handling of Nephropsnorvegicus (L.) there are a number of situations when the prawns may be exposed to very high ambient ammonia levels. These experiments evaluated the effects of increased levels of ambient total ammonia (TA = NH₃ + NH₄ ⁺) on␣blood ammonia, ammonia efflux rates and on the cardio-ventilatory performance of N. norvegicus. When prawns were taken from <1 to 2000 μmol TA l⁻¹ medium, blood TA concentrations increased rapidly for the first 2 h but tended to drop thereafter. Original blood TA levels were restored 6 h after the prawns were transferred back from seawater containing 2000 to <1 μmol TA l⁻¹. Sudden exposure to 500, 1000, 2000 or 4000 μmol TA l⁻¹ medium induced blood TA concentrations to increase respectively to 50, 30, 33 and 36% of external concentrations (normally, internal TA values are much higher than external levels). Immediately after transfer back to seawater with low ammonia concentration ( <1 μmol TA l⁻¹), excretion rates were higher than those of control prawns, and the absolute amounts of TA excreted were considerably higher than those calculated to have accumulated in the haemolymph. Heart rate (HR) and scaphognathite rate (SR) were not altered when prawns were subjected to sudden alterations in ambient ammonia ( <1 to 2000 to <1 μmol TA l⁻¹). When water ammonia concentrations were altered more gradually, both rates increased, but only at 4000 μmol TA l⁻¹. These results show that N. norvegicus is able to remove ammonia from the haemolymph and/or transform ammonia into some other substance when subjected to increased levels of ambient ammonia. Possible mechanisms involved (e.g. active transport across the gills; storage in some other tissue; glutamate synthe sis) are discussed. Received: 20 May 1996 / Accepted: 1 July 1996     

Effects of some trace heavy metals on Poecilia reticulata (Peters)

Three trace heavy metals viz., nickel, copper and zinc were studied for their toxic action against Poecilia retriculata (Peters). Among these, copper was found to be most active followed by zinc and nickel. Accumulations of these metals as well as behavioural studies were carried out after exposing fish to sub-lethal concentration of LC20. It was found that the highest quantity of nickel was accumulated in the fish body followed by zinc and copper. After exposure to sub-lethal concentration of metals some behavioural changes in fish were observed due to stress, such as mucus like secretion over gills, excessive excretion, anoretic condition and increased distance between gills and operculum. In all the cases fin movement was observed. Role and use of such changes as biological indicators or as biological early warning system in water quality assessment has been discussed.     

Bioenergetics and survival of the marine snail Thais lima during long-term oil exposure

The carnivorous snail Thais lima was fed Mytilus edulis during a 28-d exposure to the water soluble fraction (WSF) of Cook Inlet crude oil. The LC-50 of T. lima declined from >3000 ppb aromatic hydrocarbons on Day 7 to 818±118 ppb on Day 28. The LC-50 of M. edulis declined from >3 000 ppb aromatic hydrocarbons on Day 7 to 1 686±42 ppb on Day 28. Predation rate declined linearly with increasing aromatic hydrocarbon concentration up to 302 ppb; little predation occurred at 538 ppb and none at 1 160 or 1 761 ppb. Snail absorption efficiency averaged 93.5% and did not vary as a function of WSF dose. Total energy expenditure (R+U) increased at 44 ppb aromatics and declined at lethal WSF exposures. At sublethal WSF exposures, percentages of total energy expenditure were: respiration (87%), ammonia excretion (9%) and primary amine loss (4%). These percentages did not vary as a function of WSF dose or time. Oxygen:nitrogen ratios were not affected by WSF concentration or time and indicated that T. lima derived most of its energy from protein catabolism. The uptake of aromatic hydrocarbons into the soft tissues of snails and mussels was directly related to the WSF concentration. Naphthalenes accounted for 67 to 78% of the aromatic hydrocarbons in T. lima and 56 to 71% in M. edulis. The scope for growth was negative above 150 ppb WSF aromatic hydrocarbons and above 1 204 ppb soft-body aromatic hydrocarbons. These snails were physiologically stressed at an aromatic hydrocarbon concentration which was 19% of the 28-d WSF LC-50 (818±118 ppb) and/or 48% of the 28-d LC-50 of soft tissue aromatics (2 502 ppb).     

Significance of small-scale spatio-temporal heterogeneity in phytoplankton abundance for energy flow in Mytilus edulis

The effect of small-scale heterogeneity of phytoplankton abundance on mussel (Mytilus edulis L.) energy flow was studied by comparing filtration rate, consumption and assimilation efficiency in two groups of mussels fed under constant (control) and fluctuating (24 min) seston regimes of the same average. The experiment was carried out twice. Mussels appeared to regulate their filtration rate in response to varying seston concentration in one experiment, but not in the other. This behavioral difference may have been caused by differences in mean food level. Mean consumption was not different in the two feeding regimes, but assimilation efficiency was probably lower under fluctuating seston concentration. This suggests that small-scale heterogeneity in phytoplankton abundance would not affect the total transfer of energy between plankton and benthos. However, since a higher proportion of consumed energy was probably lost as faeces and/or pseudofaeces under the fluctuating seston regime, it may be expected that growth rate of mussels is depressed by small-scale heterogeneity in phytoplankton availability.Contribution to the programme GIROQ (Groupe interuniversitaire de recherches océanographiques du Québec)     

The influence of fresh weight and water temperature on metabolic rates and the energy budget of Meretrix meretrix Linnaeus

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%).     

Studies on the uptake of cadmium by the crab Carcinus maenas in the laboratory. I. Accumulation from seawater and a food source

The crab Carcinus maenas (L.) was exposed to radioactively labelled cadmium dissolved in seawater at concentrations of 0.1, 1 and 10 ppm, the latter concentration being toxic to the crabs (50% mortality after 12.3 days). Net accumulation of cadmium from solution was proportional to the level and time period of cadmium exposure. Total absorbed cadmium levels reached 0.0043 and 0.0412 mg Cd g^-1 dry weight after 40 days exposure to 0.1 and 1 ppm Cd, respectively, and 0.1115 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The highest tissue concentration was found in the midgut gland, reaching 0.786 mg Cd g^-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The midgut gland only contained about 10% of the total cadmium absorbed from solution, while the exoskeleton contained the bulk of obsorbed cadmium (59 to 80%) probably passively adsorbed onto the surface. When cadmium was absorbed by the crabs from a food source, the midgut gland contained 16.9% of the total absorbed cadmium whereas the exoskeleton now contained only 22.2%. Ten percent of the cadmium available in the food source (Artemia salina) was accumulated by the crabs. When placed in cadmium-free seawater, crabs that had accumulated cadmium from solution lost 69% of the absorbed cadmium in 10 days, mostly from the exoskeleton which lost 78% of its original absorbed cadmium concentration.     

Metabolic characteristics of midwater zooplankton: Ammonia excretion,O:N rations,and the effect of starvation

The nature of protein catabolism in a wide range of species of midwater zooplankton was investigated. The weight-specific ammonia excretion rates (g NH₃–N g^–1 dry wt h^–1, y) decline exponentially with minimum depth of occurreece (MDO, x), y=163.4 x^{–0.479±0.212} (95%ci) (CI=confidence interval), when temperature is held constant. The change in ammonia excretion can be partially explained by the decrease in percent protein (%P) with MDO, %P=80.17 MDO^{–0.148±0.122 (95%ci)} The atomic O:N ratio of freshly caught zooplankters ranged from 9.1 to 91, with most measurements between 9 and 25. Detailed studies were carried out on the response of one of the species studied (Gnathophausia ingens) to starvation (28 d). After 14 d of starvation the average ammonia excretion rate declined by more than 75% to less than 1 g NH₃–N g^–1 wet wt h^–1, although the average oxygen consumption declined by only 13% within the first 7 d of starvation and then remained stable. This differential response of oxygen consumption and ammonia excretion to starvation resulted in an increase in the average O:N ratio of starved animals from an initial 33 to 165 after 21 d. The average O:N ratios of fed mysids remained below 38 during the experiment. G. ingens maintains a relatively uniform metabolic rate during starvation by relying more heavily on its large lipid stores than when being fed.     

温度、体重对皱纹盘鲍耗氧量和排氨量的影响

皱纹盘鲍的耗氧量和排氨量的实验结果表明：温度和体重对鲍的耗氧量和排氨量有明显的影响,且两固子间存在着交互作用,皱纹盘鲍的个体耗氧量「Ｑ（Ｏ）／ｍｇｈ＾－１」和排氧量「Ｑ（Ｎ）／μｍｏｌｈ＾－１」与温度（θ／℃）和湿重（ｍ／ｇ）存在下列关系：Ｑ（Ｏ）＝０．０１２４ｍ＾０．８５５６１．０８５３＾θ,Ｑ（Ｎ）＝０．０２０７ｍ＾０．８５５６１．０８５３＾θ。２０℃皱纹盘鲍存在代谢的转变点。     

Metabolism of proline by the tiger prawnPenaeus esculentus

The distribution and fate of¹⁴C-proline were investigated in immature tiger prawns,Penaeus esculentus Haswell, collected in Moreton Bay, Cleveland, Australia, by trawling during 1986/1987. Initially the prawns were fed¹⁴C-proline in food pellets to follow the pathway of proline absorption and distribution in the body.¹⁴C-proline was also injected directly into the prawn to provide sufficient tracer to follow the incorporation of¹⁴C into other amino acids and into proteins. A comparison was made of the metabolism of injected¹⁴C-proline over 48 h in prawns that had been fed and those that had been starved for 10 d. Free amino acids (FAA) in the muscle and protein-bound amino acids were analysed separately. Labelled proline was completely absorbed and distributed within the body 3 h after ingestion, about 80% being in the tissues, mostly in muscle. There was no significant difference between the total CO₂ output in fed and starved prawns, but the latter metabolised about twice the amount of labelled proline over 48 h. At this time, in abdominal muscle of fed prawns, about 95% of the total muscle label was in the FAA; of the label in the FAA, 78% was proline and 18% glutamic acid, with the remainder in hydroxyproline, aspartic acid, glutamine, alanine and Kreb's cycle intermediates. In the starved prawns, proline was 58%, glutamic acid 24%, with correspondingly higher amounts in the other compounds. In the muscle protein, the distribution of label was similar in fed and starved prawns, with 72 to 74% as proline. The experiments showed that proline is not very labile in the tiger prawn and its rate of synthesis is slow. It does not appear to be an important source of energy as in some insects and cephalopods, but during starvation is only slowly oxidised for energy.     

Metabolic rates of epipelagic marine copepods as a function of body mass and temperature

Metabolic rates (oxygen consumption, ammonia excretion, phosphate excretion) have been calculated as a function of body mass (dry, carbon, nitrogen and phosphorus weights) and habitat temperature, using multiple regression. The metabolic data used for this analysis were species structured, collected from Arctic to Antarctic seas (temperature range: -1.7°C to 29.0°C). The data were further divided into geographical and/or seasonal groups (35 species and 43 data sets for oxygen consumption; 38 species and 58 data sets for ammonia excretion; 22 species and 31 data sets for phosphate excretion). The results revealed that the variance attributed to body mass and temperature was highest (93-96%) for oxygen consumption rates, followed by ammonia excretion rates (74-80%) and phosphate excretion rates (46-56%). Among the various body mass units, the best correlation was provided by the nitrogen unit, followed by the dry weight unit. The calculated Q₁₀ values varied slightly according to the choice of body mass units; overall ranges were 1.8-2.1 for oxygen consumption rates, 1.8-2.0 for ammonia excretion rates and 1.6-1.9 for phosphate excretion rates. The effects of body mass and temperature on the metabolic quotients (O:N, N:P, O:P) were insignificant in most cases. Although the copepod metabolic data used in the present analysis were for adult and pre-adult stages, possible applications of the resultant regression equations to predict the metabolic rates of naupliar and early copepodite stages are discussed. Finally, global patterns of net growth efficiency [growth (growth+metabolism)^-1] of copepods were deduced by combining the present metabolic equation with Hirst and Lampitt's global growth equation for epipelagic marine copepods.     

Influence of sex and age on the feeding habits of the common soleSolea solea

The lethal concentration of cadmium was determined for the mysidLeptomysis lingvura G.O. Sars, a Mediterranean species from surface coastal waters, and the effect of sublethal doses on respiration, ammonia excretion, and feeding efficiency at different temperatures, and on activities of 19 hydrolases was tested. Experiments were carried out on individuals collected in spring 1987 near Marseille. At 18°C, respiration rate was significantly affected only by concentrations >0.05 mg Cd l^–1. At 0.1 mg Cd l^–1, respiration rate was more significantly depressed at 20°C than at 10°C. There was a concomitant decrease in the Q₁₀ rate (by 23 to 59%, according to the particular experiment), indicating a strong synergistic effect of temperature. Ammonia excretion was likewise affected by cadmium, also with a concomitant decrease in the Q₁₀ rate (by 34%). Daily faecal pellet production was maximum at 18°C; it was inhibited by cadmium at temperatures between 14 and 20°C, and enhanced at extreme temperatures (10 and 22°C). The assimilation efficiency of contaminated individuals was reduced by 9%. These decreases in faecal pellet production and assimilation efficiency reflect a significant decrease in energy (by about 43%) which could rapidly lead to an unbalanced energy budget with a consecutive lowering of the reproductive potential. Generally, hydrolase activities usually increased initially in the presence of 0.2 mg Cd l^–1, but after 48 h they declined, reaching very low values at 72 h. Most physiological processes are therefore affected by exposure to cadmium and the unbalanced energy budget arises from the inability to utilize environmental food. These results are consistent with the literature data on cadmium contamination in marine organisms. Physiological and biochemical changes appear to be very informative in studies of in vitro sublethal effects of micropollutants and in situ environmental modifications.     

Effects of prolonged starvation on O2 consumption,NH 4 + excretion,and chemical composition of the bathypelagic mysid Gnathophausia ingens

The large bathypelagic mysid Gnathophausia ingens was collected in January 1980 at 400 to 700 m depth from the San Clemente Basin off southern California. Instars 7-8 and Instars 10-12 were starved in the laboratory for up to 19 wk. Oxygen consumption and ammonia excretion rates, and water, protein, lipid, and ash contents were determined periodically during starvation. Protein and lipid were metabolized in approximately equal amounts by starved individuals after the initial weeks of food deprivation. Unidentified components (probably non-protein nitrogenous compounds) apparently were oxidized within the first 7 wk of starvation. Oxygen consumption and ammonia excretion by Instars 7-8 decreased steadily during 19 wk of starvation. In contrast, stable or increasing respiration and excretion rates were observed for fed mysids. The mean respiration rate of Instars 10-12 did not change significantly during 13 wk of starvation, although ammonia excretion rates decreased. Low metabolic rates and large lipid reserves probably help G. ingens to withstand long periods of starvation in the mesopelagic environment. Calculations based on the laboratory data demonstrate that small, infrequent meals could account for the rates of metabolism and growth observed for G. ingens in the field.