Oxygen consumption of the West African blood clamAnadara senilis

The West African blood clamAnadara senilis (L.) is one of a small number of bivalve species which have haemoglobin in their haemolymph. In the investigation reported here, in which the musselMytilus edulis (L.) was also studied for comparative purposes, it was shown thatA. senilis was an oxygen regulator between oxygen tensions corresponding to 50 and 100% air saturation. Oxygen uptake increased by about 128% after 24 h at zero pO₂; although the haemoglobins ofA. senilis were found to be responsible for about 34% of oxygen uptake at 25°C (a proportion unaffected by pO₂), there was clearly insufficient haemoglobin present in the haemolymph to act as an effective oxygen store during prolonged exposure to anoxic conditions.     

Effects of environmental parameters on the oxygen consumption of four marine invertebrates: a comparative factorial study

The oxygen consumption curves of two decapod crustaceans (Palaemon serratus, Penaeus monodon) and two prosobranch molluscs (Trunculariopsis trunculus, Nassarius mutabilis) have been detected in the entire pO₂ interval from 0 to 160 mmHg, under different conditions of temperature and salinity. From the experimental curves, physiological parameters such as the initial oxygen consumption velocity, the Q ₁₀ values and the oxygen independence indices have been measured. The latter parameters have been obtained using normalised plots which allow their better evaluation. The effects of temperature, salinity and oxygen partial pressure on the oxygen-consumption features have been studied using a factorial experimental plan which allows measurement of the effects of each experimental variable as well as the effects of synergistic interactions between different variables. Received: 27 March 2000 / Accepted: 13 November 2000     

Effect of oxygen and salt on haemolymph oxygen binding in the brine shrimp Artemia franciscana

The oxygen-binding properties of haemolymph from laboratory-reared Artemia franciscana were investigated in vitro. Adult female brine shrimp without eggs were acclimated to seven different combinations of salinity and oxygen. The oxygen affinity (P₅₀) of unprocessed haemolymph rises with acclimation oxygen partial pressure (PO₂) up to normoxic values, after which no influence of oxygen occurs. The increase in P₅₀ with acclimation PO₂ can be explained by the change in proportion of each of three different haemoglobins in the haemolymph. Salinity acclimation has no effect on haemolymph P₅₀. The effects of the different major salts [NaNO₃, NaCl, Ca(NO₃)₂, Mg(NO₃)₂], pH, and the metal-binding ligand EGTA on the oxygen-binding properties of buffered haemolymph (of shrimp acclimated to 10 salinity) were also studied. Little or no effect of these salts could be found. A small Bohr effect (pH 6.5 to 9.1, =-0.11) was noted. Addition of EGTA caused a significant decrease of the oxygen affinity at concentrations up to 50 mmoll^-1.     

Some mechanisms of salinity acclimation in the euryhaline teleost,Etroplus maculatus

Mechanisms of salinity acclimation in the euryhaline freshwater living teleost, Etroplus maculatus (Bleeker), were studied. Brain water content decreased steadily with increasing salinity of the medium. Liver and muscle water content increased initially in 30% sea-water but in higher salinities decreased markedly, approximating control levels. Osmotic pressure of tissue fluid increased by 33% from 0.45% NaCl equivalent in freshwater to 0.60% NaCl equivalent in 100% sea-water. K and Mg decreased in dilute saline media but in 100% sea-water increased markedly approximating control levels; this is especially so in regard to Mg. Na decreased steadily and Ca increased with increasing salinity. Cl increased in 60% sea-water but decreased in 100% sea-water; however, its concentration in 100% sea-water exceeded that in freshwater. Free amíno acids increased by 11% in 30% sea-water but decreased in 60% and 100% sea-water, such that their concentration was lower by 28% in 60% sea-water and by 34% in 100% sea-water relative to the control level. Ascorbic acid decreased by 37% in 30% sea-water but in 60% and 100% sea-water increased steadily approximating the control level. The significance of these changes in the physiology of salinity acclimation is discussed and a correlation suggested between acclimation to salinity and to high temperature.     

Effect of ionizing radiation on haemoglobin of marine lamellibranchs

The effect of ionizing radiation on the iron-linked protein (haemoglobin) of the marine lamellibranchs Anadara granosa (Linn.) and Cardita antiquata (Lam.) from Bombay waters, India is discussed. Purified haemoglobin solutions were exposed to a ⁶⁰Cobalt source delivering a dose of about 4,600 rad/min, at the sample irradiation point. Radiation damage or degradation was measured spectrophometrically by studying changes in the absorption spectra following irradiation in the presence and absence of oxygen. Exposure to ionizing radiation in general caused a decrease in absorption of both haemoglobins, irrespective of location, viz extra-versus intracellular, at Soret (412 m), (540 to 42 m) and (574 to 76 m) peaks, and an increase in absorption at 510 and 630 m. Upon exposure to a higher dose, O₂Hb of C. antiquata showed an increase in absorption at the protein peak (280 m); exposure to a lower dose, however, resulted in decreased absorption. Furthermore, the changes following irradiation were dependent upon the initial state of the pigment. Oxyhaemoglobin, when exposed to radiation, oxidized to hemiglobin, and hemiglobin reduced to oxyhaemoglobin. The extracellular haemoglobin of high molecular weight (3x10⁶) of the false cockle C. antiquata was found to be extremely radio-resistant, whereas intracellular haemoglobin of low molecular weight (74,000) of the arcid clam A. granosa was highly radiosensitive, since it could not be exposed to doses exceeding 18,000 r.     

The influence of hyperbaric oxygen therapy on intestinal mucosal barrier function in rats with acute carbon monoxide poisoning

Hyperbaric oxygen increases the partial pressure of O₂ in arterial blood and tissues and thereby relieves cellular hypoxia. We investigated whether this treatment changes biochemical parameters and intestinal mucosal barrier function in rats exposed to toxic levels of CO. Groups of ten Sprague–Dawley rats were treated with CO, with hyperbaric oxygen, or with CO followed by hyperbaric oxygen. A fourth group maintained under normal atmospheric conditions served as a control. CO poisoning increased red blood cell distribution width and the amount of alanine aminotransferase, urea nitrogen, and tight junction creatine kinase but decreased the mean corpuscular hemoglobin (Hb). These changes were reversed after hyperbaric oxygen therapy, which increased the number of red blood cells, hematocrit level, total protein, and Hb level. Hyperbaric oxygen therapy also increased tight junction protein 1 expression and reduced toll-like receptor 4 expression in the rat colon. In conclusion, hyperbaric oxygen resulted in an improved oxic condition in CO-poisoned rats and restored energy metabolism by repairing, to some extent, the organs injured by CO. The therapy may also improve the function of the intestinal mucosal barrier.     

Parthenogenetic reproduction of Diaphanosoma celebensis (Crustacea: Cladocera): influence of salinity on feeding, survival, growth and neonate production

 Effect of salinity on the feeding rate and parthenogenetic reproduction of asexual females of the cladoceran Diaphanosoma celebensis Stingelin was studied. Short-term (10 h) grazing experiments were conducted using Isochrysis galbana as feed at 5, 17, 25 and 30 psu salinity. Gut pigment concentration showed a significantly higher rate of feeding at lower salinities. Survival, growth, maturity attainment and neonate production of asexual females reared in the above four test salinities indicated preference for lower salinities (5 and 17 psu). The mean size of adult females decreased from 909 to 593 μm, mean life span from 24 to 5 d, mean neonate production from 12 to 2 and mean size of neonates from 434 to 400 μm as the salinity increased from 5 to 30 psu. Salinity variations also affected the size and age of primiparous females. Resting egg formation and sexual reproduction did not occur at the tested salinities. The results indicate that D. celebensis is adapted to low saline, estuarine environments. Received: 14 January 2000 / Accepted: 24 March 2000     

Respiration,pumping activity and heart rate in Ciona intestinalis exposed to fluctuating salinities

Specimens of Ciona intestinalis L. were exposed to both gradual (sinusoidal) and abrupt (square-wave) salinity fluctuations and the changes in pumping activity and oxygen sonsumption monitored. Heart rate was monitored under steady state conditions using a new in vivo method, and pumping activity was monitored as spontaneous squirting by use of a pressure transducer. Oxygen consumption was also monitored under steady state conditions and under conditions of declining oxygen tension. It was found that during periods of regular beating the mean heart rate for 5 ascidians was 13.2 beats min^-1 for the branchial pacemaker and 32.6 beats min^-1 for the visceral pacemaker. Regular periods of beating lasted for approximately 1 min, followed by periods of irregular activity prior to heart beat reversal. The heart beat became irregular and reversal occurred sporadically when the ascidians were exposed to dilute seawater. The ascidians showed a pumping rate of 14 squirts per hour in full-strength seawater. This rate declined during decreasing salinity and ceased entirely when the external seawater concentration reached approximately 60% seawater (100%=32% S). During periods of decreased salinity, the siphons were tightly closed and oxygen consumption was zero. The rate of oxygen consumption by C. intestinalis decreased during decreasing salinities and there was no evidence of an oxygen debt. Oxygen consumption under steady state conditions varied with body weight according to the following: oxygen consuption =0.515 W ^0.831 (where W is body weight). The rate of oxygen consumption was found to be dependent on the external oxygen tension.     

Haematological evaluation of naphthalene intoxication in the tropical arcid blood clam Anadara granosa

In vertebrates haematological parameters are of considerable importance in the diagnosis of pathological disorders due to pollutants. Similar haematological studies in invertebrates are lacking. This is partly because a very few species have erythrocytes; arcid clams, however, are unique in having erythrocytes. Our experiments were designed therefore to evaluate the effect of naphthalene (N) on haematological parameters in the tropical arcid blood clam Anadara granosa L. The parameter studied were haemoglobin (Hb), erythrocyte sedimentation rate (ESR), haematocrit, erythrocyte fragility, haemolymph cations, free amino acids and osmolality. On exposure to naphthalene (N) in the sublethal range (5 to 15 g ml^-1) Hb content decreased appreciably (P<0.001) compared with controls. Although ESR increased significantly (P<0.001), haematocrit decreased by 17 to 37%. Treatment with N for 96 h increased erythrocyte fragility and haemolysis; the latter by more than 40%. Both inorganic phosphate and free fatty acids increased with ambient concentration of N. Haemolymph cations — K, Ca and Mg increased significantly in relation to control. Na decreased, but not significantly. Free amino acids decreased significantly (P<0.001) with the ambient concentration of naphthalene, but haemolymph osmolality was not effected.     

Oxygen supply in aquatic ectotherms: partial pressure and solubility together explain biodiversity and size patterns

Aquatic ectotherms face the continuous challenge of capturing sufficient oxygen from their environment as the diffusion rate of oxygen in water is 3 x 10(5) times lower than in air. Despite the recognized importance of oxygen in shaping aquatic communities, consensus on what drives environmental oxygen availability is lacking. Physiologists emphasize oxygen partial pressure, while ecologists emphasize oxygen solubility, traditionally expressing oxygen in terms of concentrations. To resolve the question of whether partial pressure or solubility limits oxygen supply in nature, we return to first principles and derive an index of oxygen supply from Fick's classic first law of diffusion. This oxygen supply index (OSI) incorporates both partial pressure and solubility. Our OSI successfully explains published patterns in body size and species across environmental clines linked to differences in oxygen partial pressure (altitude, organic pollution) or oxygen solubility (temperature and salinity). Moreover, the OSI was more accurately and consistently related to these ecological patterns than other measures of oxygen (oxygen saturation, dissolved oxygen concentration, biochemical oxygen demand concentrations) and similarly outperformed temperature and altitude, which covaried with these environmental clines. Intriguingly, by incorporating gas diffusion rates, it becomes clear that actually more oxygen is available to an organism in warmer habitats where lower oxygen concentrations would suggest the reverse. Under our model, the observed reductions in aerobic performance in warmer habitats do not arise from lower oxygen concentrations, but instead through organismal oxygen demand exceeding supply. This reappraisal of how organismal thermal physiology and oxygen demands together shape aerobic performance in aquatic ectotherms and the new insight of how these components change with temperature have broad implications for predicting the responses of aquatic communities to ongoing global climate shifts.     

Consequences of maternal isolation from salinity stress for brooded embryos and future juveniles in the estuarine direct-developing gastropod Crepipatella dilatata

At reduced salinities, brooding females of some gastropods and bivalves may isolate their mantle cavities from the environment for several days, maintaining internal osmotic concentration but causing severe declines in dissolved oxygen and pH, and increases in ammonia and other toxic substances in the mantle fluid. This study in November–December examined the immediate consequences of such stresses for brooded embryos of Quempillén estuary gastropod Crepipatella dilatata, in terms of time to juvenile emergence and rates of embryonic growth [measured as shell length (SL)]. Juveniles were also monitored for latent effects on feeding rates, oxygen consumption, and growth for the first 4 weeks after emergence into normal salinity seawater. An acute salinity stress lasting 3 days applied to females that were brooding pre-shelled or intermediate-shelled stages increased embryonic incubation periods, but without affecting SL at emergence. Growth rates were reduced for encapsulated embryos regardless of the stage at which the salinity stress was applied. Latent effects on juvenile development included slower shell growth and reduced rates of oxygen consumption and feeding. These effects were sustained for the first month after release from the female. The results suggest that marked reductions in salinity lasting for several days indirectly but negatively affect the development of brooded embryos of C. dilatata and also affect the juveniles for at least several weeks following their release, even after salinity has returned to normal.     

Living in the front: Neomysis americana (Mysidacea) in the Río de la Plata estuary, Argentina-Uruguay

The Río de la Plata is one of the main estuarine systems of South America. It is characterized by a salt wedge regime, a well-developed bottom salinity front, and a maximum turbidity zone associated with it. We described, for the first time, the spatial distributional patterns of Neomysis americana, the most abundant mysid and the main food item for juvenile fishes in this estuary. We analyzed the link between mysid distribution and abundance and the bottom salinity gradient. A total of 242 plankton samples were taken from the Río de la Plata estuary in spring and fall between 1991 and 2001. Bottom salinity gradient was quantified from grids created on the basis of 348 oceanographic stations. The N. americana population was characterized by high abundances (up to 2500 ind. m⁻³), with juveniles, males, gravid and non-gravid females present in both spring and fall of different years. N. americana distribution followed the position of the bottom salinity front in different years and seasons. Pearson’s correlation analysis between mysid abundance and bottom salinity gradient confirmed the association of mysids with the bottom salinity front (maximum salinity gradient). No correlation was detected between mysid abundance and salinity per se or temperature (neither in spring nor in fall). We speculate that mysids concentrated at the front could take advantage of the high concentration of detrital material for feeding. The results of our work highlight the importance of the magnitude of salinity gradient for the ecological processes of a salt-wedge estuary like the Río de la Plata. The analysis of the spatial distribution of gradient values presented in this work also constitutes a useful tool to locate key ecological areas such as fronts.     

Respiratory responses of the estuarine mysid Neomysis integer (Peracarida: Mysidacea) in relation to a variable environment

The euryhaline mysid Neomysis integer (Peracarida: Mysidacea) is a common member of the hyperbenthos of the upper reaches of European estuaries. In the East Looe River Estuary (Cornwall, England), this species experiences extensive tidal and seasonal changes in temperature (3 to 15 °C) and salinity (1 to 34‰). In this investigation, the effects of temperature (5, 10 and 15 °C) and salinity (1, 10, 20 and 30‰) on the oxygen consumption of male and female N. integer are reported, and are related to field measurements to identify the adaptive responses of the respiratory physiology to such a variable environment. The general responses were similar for each sex; however, at any given temperature/salinity combination, male N. integer consumed more oxygen than females. The general trends were increased oxygen consumption with increasing temperature (Q₁₀ values ranged from ∼1.7 to 2.5) and decreased oxygen consumption with increasing salinity. Temperature and salinity interacted at high water antagonistically to minimise changes in mysid oxygen-consumption. When related to tidal fluctuations in temperature and salinity experienced by N. integer inhabiting the East Looe River Estuary, the results reveal how the respiratory physiology of this species is adapted to its variable environment. Received: 16 June 1998 / Accepted: 15 December 1998     

Toxicity of cadmium to Parachanna obscura : As evidenced by alterations in hematology,histology, and behavior

Fish of species Parachanna obscura are exposed to four concentrations of cadmium (Cd) (0.02, 0.06, 0.18, or 0.54?mg?L^?1). Acute toxicity test results after 96?h showed marked hematological, histological, and behavioral changes. Quantitative blood analysis revealed that white blood cell (WBC), packed cell volume (PCV), and platelets counts were linearly correlated with increasing Cd concentrations; however, blood haemoglobin (Hb) showed an inverse relationship, with higher Hb levels at lower Cd concentrations. Histological changes of the liver showed hepatic separation, bloody appearance, and deposition of a brownish-yellow substance, which increased with rising concentrations of metal. Behavioral changes observed included reduced activity, avoidance response, and deposition of a slimy-whitish film on the body of the fish, which increased with concentration and exposure time.     

Effect of salinity on hypoxia tolerance of resting green crabs, Carcinus maenas, after feeding

Mechanisms that can influence the tolerance of hypoxia in brackish waters were studied in resting and fed crabs, Carcinus maenas, at 15?°C. Mortality, blood oxygenation, acid-base status and lactate concentration were analysed in fed crabs held in full-strength normoxic seawater (32.5‰?S) and then transferred for 24?h to a partial pressure of oxygen (P_o2) of 3?kPa (1.4?mg?l^?1) and various salinities (17, 12.5, 10, 8‰?S). At salinity levels >10‰, fed crabs tolerated P_o2 values as low as 3?kPa in the ambient water and 0.5?kPa in their arterial blood for 24?h without switching to anaerobic metabolism. Only below 10‰?S did their blood-lactate content rise, leading to their death despite the fact that their blood O₂-content was twice the control value measured in full-strength normoxic seawater and their blood P_o2 did not decrease below values recorded at higher salinity levels. Addition of CO₂ to 8‰?S water (CO₂ partial pressure increasing from 0.1 to 0.3?kPa) decreased blood-lactate production and mortality, suggesting that at 10‰?S impairment of the O₂ supply is limited by an excessive blood O₂-affinity. The results are discussed in terms of the distribution (?10‰?S) of C. maenas along salinity gradients in estuaries and bays.     

Inorganic skeleton of the demosponge Halichondria panicea. Seasonality in spicule production in the Baltic Sea

Seasonality in spicule production of the demosponge Halichondria panicea (Pallas, 1766) was studied in the Western Baltic from July 1992 to July 1993. Spicule production increased in parallel with increasing temperatures in spring, being most pronounced during summer after release of larvae. Large proportions of up to 30% immature spicules occurred in the population during skeleton production peaks, and this resulted in reduction of mean spicule dimensions by ≃20%. Effects on spicule width were more obvious than on spicule length. In winter, when wave forces were largest, higher percentages of mineral skeleton were observed: 50% of dry weight compared to 40% in summer. Enhanced spicule densities in the tissues were not attained by marked spicule production but through a reduction in organic content by shrinking. In spring, growth of body tissue was faster than the build-up of skeleton, so that the relative amount of the latter was reduced. The indirect, growth-related developments of the skeleton were inversely proportional to temperature and directly to salinity, silicate concentrations and wave energy. Spicule size and the number of immature spicules were correlated with temperature and only slightly with salinity. No correlation with oxygen concentration or pH could be detected. Received: 3 April 1997 / Accepted: 8 August 1997     

Role of the free amino acid pool of the copepod Acartia tonsa in adjustment to salinity change

The free amino acid pool of the calanoid copepod Acartia tonsa was reduced in proportion to the decrease in external salinity within 24 h, with a corresponding increase in ammonia excretion and a transient rise in oxygen consumption. The free amino acid pool was not increased in response to increased salinity. Catabolism of free amino acids is important in the reduction of cellular osmotic pressure in reduced salinities. Antagonistic demands of osmotic preservation and nutritional metabolism on the free amino acid pool may limit the production of the species in waters of higher salinity.     

Mercury stress on juvenile bay scallops,Argopecten irradians,under various salinity-temperature regimes

Survival of juvenile bay scallops, Argopecten irradians, after 96 h of exposure to mercury at various salinity and temperature regimes was studied. Scallop survival was significantly affected by mercury concentration and by salinity, as well as by the interaction between temperature and concentration and between temperature and salinity. Toxicity of mercury at low concentrations was enhanced by high temperature and low salinity, whereas at high mercury concentrations this effect diminished.     

Haematological responses to exposure to sublethal concentration of cadmium in air breathing fish, Channa punctatus (Bloch)

The effect of sublethal concentration (29 mg/l) of cadmium on haematological parameters of Channa punctatus after the exposure periods of 7, 15 and 30 days were studied. In treated groups of cadmium exposed fish have been found to significantly decreased in total erythrocyte count, haemoglobin content, packed cell volume, mean corpuscular haemoglobin concentration and oxygen carrying capacity of blood, and at the same time the white blood cell count, mean cell volume and mean corpuscular haemoglobin were found to significantly increased. Both increasing and decreasing of the above mentioned haematological characteristics of blood cells of cadmium intoxicant are mainly with time dependent effects. With regard to the pathological characteristics of blood cells of cadmium intoxicant fish shows fragility and rupture of erythrocytic membrane and leads to haemolysis, which are very severe on 30 day of exposure group.     

Bioenergetics of ephyra larvae of the scyphozoan jellyfish Aurelia aurita in relation to temperature and salinity

The body mass of Aurelia aurita ephyrae was better correlated with the diameter of the central disc than with the distance between opposite rhopaliae or distance between opposite lappet tips. Body dry weight (y, in μg) related to the disc diameter (x, in mm) through the equation y = 22.33 x ^1.99. The exponent 1.99 was significantly lower than that for the medusa stage, indicating a tendency to grow in diameter rather than in weight through the ephyra stage. The average ash-free dry weight (AFDW) of ephyrae was 38.0% of the dry weight. The AFDW/diameter relationship was used to convert measured diameters to body AFDW and calculate succession in body mass, daily ration, daily growth rate and gross growth efficiency. Effects of temperature (6, 9.5, 12, 15 and 18 °C) and salinity (17.5, 22, 26, 30.5 and 35 PSU) on these parameters and feeding were studied at saturated prey concentration (222 Artemia nauplii l⁻¹ initial concentration) by daily measurements over 10 d. There was a strong effect of temperature for total ingestion, growth rate, growth efficiency and final body mass of individual ephyrae, whereas the daily ration was not significantly different between the different temperatures. The experimental group kept at the highest temperature (18 °C) diverged the most, and ephyrae at this temperature ingested 2.7 times more and increased in weight 5.4 times more than at 6 °C. The average daily growth rate and gross growth efficiency of these ephyrae were 34.5% and 25.1%, respectively, significantly higher than at 6, 9.5 and 15 °C. Significant effects of salinity were shown for total ingestion, daily ration, daily growth rate and final weight, although only total ingestion and daily ration diverged sufficiently to show effects in a post-hoc test. This test showed that total ingestion was significantly different for all salinities except between 22 and 35 PSU and between 17.5 and 26 PSU. The daily ration for 35 PSU diverged from all other salinities, whereas none of the other salinities showed any significant differences. Thus, provided food in excess A. aurita can double its weight every 2 to 4 d, dependent on temperature and can therefore develop to the medusa stage in short time. Differences in environmental salinity in the range 17.5 to 35 PSU have little or no effect on growth rate and growth efficiency, whereas our results indicate that the full seawater salinity (35 PSU) causes significantly higher ingestion rate compared to lower salinities. Received: 11 January 1999 / Accepted: 11 May 1999