Responses Of Mytilus-Edulis On Exposure To The Water-Accommodated Fraction Of North-Sea-Oil

Individuals of Mytilus edulis L., collected from the Erme estuary (S.W. England) in 1978, were exposed to low concentrations (7 to 68 μg l-1) of the water-accommodated fraction (WAF) of North Sea crude oil. The pattern of accumulation of petroleum hydrocarbons in the body tissues was affected by the presence of algal food cells, the period of exposure, the hydrocarbon concentration in seawater, the type of body tissue and the nature of the hydrocarbon. Many physiological responses (e.g. rates of oxygen consumption, feeding, excretion, and scope for growth), cellular responses (e.g. lysosomal latency and digestive cell size) and biochemical responses (e.g. specific activities of several enzymes) were significantly altered by short-term (4 wk) and/or long-term (5 mo) exposure to WAF. Stress indices such as scope for growth and lysosomal latency were negatively correlated with tissue aromatic hydrocarbons.

Some Ecological Consequences Of The Physiological And Biochemical Effects Of Petroleum Compounds On Marine Mollusks

The problems of relating the results of experiments in the laboratory to events in nature are twofold: to equate the response to a single variable (hydrocarbons) with the natural variability in the biological material in a multivariate environment, and to consider whether the response established experimentally has any relevance to the animal's chances of survival and reproduction (i.e. its fitness) in the natural population. Recent studies of the effects of petroleum hydrocarbons on marine invertebrates are reviewed, with an emphasis on the physiological and cytochemical responses by bivalve molluscs. The dose-response relations that emerge suggest the intensity of the 'signal' that must be detected in nature if the chronic, sublethal effects of petroleum pollution are to be measured. The natural variability in these physiological and cytochemical processes are then reviewed and the main causes of variability in natural populations, both endogenous and exogenous, discussed. These results indicate the extent of the `noise' above which the signal from possible pollution effects must be detected. The results from recent field studies on the common mussel, Mytilus edulis, are discussed. The results are as complex as expected, but it proves possible to reduce the variance in the measured responses so that pollution effects, including those due to hydrocarbons, can be detected. The ecological consequences of the observed effects of petroleum hydrocarbons are then discussed in terms of reproductive effort and reproductive value. Considerable variation between populations exists here also and this can be used to help in the interpretation of the extent of the impact of the environment on the ecology of the population. The result is to place the findings of the laboratory experiments in an ecological context of natural variability and of the physiological costs of adaptation.

Some Practical Considerations In The Measurement Of Pollution Effects On Bivalve Mollusks And Some Possible Ecological Consequences

A consideration of some physiological (rates of oxygen consumption, the scope for growth) and cellular (the cytochemical latency of a lysosomal enzyme) processes in bivalve molluscs suggests that animal size and seasonal changes related to the gametogenic cycle are important sources of natural variability. Correcting for size using regression techniques, and limiting measurements to one part of the gametogenic cycle, reduces observed natural variability considerably. Differences between populations are then still apparent, but the results of laboratory experiments with hydrocarbons from crude oil suggest that it should be possible to detect sub-lethal effects due to pollution (the ‘signal’) in the presence of the remaining natural variability (the ‘noise’). Statistical considerations, taken together with results from current studies on Mytilus edulis and Scobicularia plana, indicate that sample sizes of 10–15 individuals should suffice for the detection of possible pollution effects. The physiological effects to be expected in the presence of sub-lethal levels of polluting hydrocarbons are on a scaie that can cause significant ecological damage to a population through a reduction in fecundity and the residual reproductive value of the individuals.

Invivo Changes In The Activity Of Gill ATPases And Hemolymph Ions Of Carcinus Maenas Exposed To p p'-DDT And Reduced Salinities

1. Haemolymph osmoregulation by the shore crab, Carcinus maenas was confirmed over a range of salinities. 2. Na+K+-ATPase and Mg2+-ATPase activities in gill tissue increased with a decrease in salinity. 3. Na+K+-ATPase and Mg2+-ATPase activities were inhibited after exposure to p,p′-DDT. 4. K+ ion levels of the haemolymph remained unchanged, but Na+ ion levels were affected after 7 hr when transferred from 100 to 5% SW after exposure to DDT.

Lysosomes And The Response By Mytilus-Edulis-L To An Increase In Salinity

Cytochemical observations and measurements on cell-free suspensions of lysosomes from the digestive gland of Mytilus edulis showed a reduced latency of the lysosomal enzyme beta -N-acetyl-hexosaminidase 12h after mussels were transferred from 21 to 35%o salinity, but showed no change up to 6 h after transfer. There was a transient alteration in the form of the latency curve after 6 h at high salinity, signifying a gradual change in membrane integrity. Free hexosaminidase activity increased, 12 h after the salinity rise. The lysosomes were permeable to amino acids when ATP was present; permeability increased following the rise in salinity. The concentration of ninhydrin-positive substances in the lysosomes increased 6 h after transfer and then, between 6 and 12 h, the concentration declined. The results are consistent with the hypothesis that lysosomal hydrolysis is a source of free amino acids during the adaptation of mussels to increased salinity.

Mixed-Function Oxygenases And Xenobiotic Detoxication-Toxication Systems In Bivalve Mollusks

Components of a xenobiotic detoxication/toxication system involving mixed function oxygenases are present inMytilus edulis. Our paper critically reviews the recent literature on this topic which reported the apparent absence of such a system in bivalve molluscs and attempts to reconcile this viewpoint with our own findings on NADPH neotetrazolium reductase, glucose-6-phosphate dehydrogenase, aldrin epoxidation and other reports of the presence of mixed function oxygenases. New experimental data are presented which indicate that some elements of the detoxication/toxication system inM. edulis can be induced by aromatic hydrocarbons derived from crude oil. This includes a brief review of the results of long-term experiments in which mussels were exposed to low concentrations of the water accommodated fraction of North Sea crude oil (7.7–68 µg 1−1) in which general stress responses such as reduced physiological scope for growth, cytotoxic damage to lysosomal integrity and cellular damage are considered as characteristics of the general stress syndrome induced by the toxic action of the xenobiotics. In addition, induction in the blood cells of microsomal NADPH neotetrazolium reductase (associated with mixed function oxygenases) and the NADPH generating enzyme glucose-6-phosphate dehydrogenase are considered to be specific biological responses to the presence of aromatic hydrocarbons. The consequences of this detoxication/toxication system forMytilus edulis are discussed in terms of the formation of toxic electrophilic intermediate metabolites which are highly reactive and can combine with DNA, RNA and proteins with subsequent damage to these cellular constituents. Implications for neoplasms associated with the blood cells are also discussed. Finally, in view of the increased use of mussel species in pollutant monitoring programmes, the induction phenomenon which is associated with microsomal enzymes in the blood cells is considered as a possible tool for the detection of the biological effects of environmental contamination by low concentrations of certain groups of organic xenobiotics.

Leucine Aminopeptidase (Aminopeptidase-I) N-Acetyl-Beta-Hexosaminidase And Lysosomes In The Mussel Mytilus-Edulis-L In Response To Salinity Changes

The intracellular distribution of aminopeptidase-I in the intestinal and digestive cells of Mytilus edulishas been shown to be the same as the lysosomal marker enzymes β-glucuronidase and N-acetyl-β-hexosaminidase. Activity for these enzymes was also associated with the intestinal apical cytoplasm and microvillous border where there was pronounced staining for aminopeptidase-I. Experimental alterations of salinity induced changes in both microdensitometrically and spectrophotometrically determined aminopeptidase-I activity, as an increase with raised salinity and a decrease with lowered salinity. Lysosomal hexosaminidase showed similar changes in activity with altered salinity. Cytochemically determined lysosomal stability was also responsive to salinity changes, indicative of alterations in lysosomal functional capability. The lysosomal distribution of aminopeptidase-I is discussed in terms of the function of lysosomes in intracellular protein turnover, their high concentrations of free amino acids, and the possible roles which these might play in intracellular osmoregulation in response to salinity change.

Seasonal-Changes In The Physiology Reproductive Condition And Carbohydrate Content Of The Cockle Cardium (=Cerastoderma) Edule (Bivalvia Cardiidae)

Pronounced seasonal cycles in the rates of oxygen consumption and feeding were found for Cardium (=Cerastoderma) edule L. measured in the field under ambient conditions. The cockles had a maximum rate of oxygen consumption (0.89 ml O2 g-1 h-1) in April which declined to a minimum of 0.35 ml O2 g-1 h-1 in March. Their feeding rate was variable but had a maximum value (3.91 l g-1 h-1) in April and a minimum value (0.73 l g-1 h-1) in October. There was no apparent seasonal variation in absorption efficiency, with a mean value of 67.6%. Gametogenesis was initiated in January and the population reached a peak in reproductive condition in April/May, followed by a 3 month spawning period. Carbohydrate reserves were synthesised during spawning, and were then utilised during the winter and early spring. An adaptive function for a reduction in time spent feeding is postulated, and correlations between the rates of certain physiological processes and some exogenous and endogenous variables are discussed.

Physiological And Biochemical Responses Of Bivalve Mollusks To Exposure To Air

1. Aerial rate of oxygen consumption by Mytilus edulis and M. galloprovincialis is 4–17% of the aquatic rate. 2. For Cardium edule and Modiolus demissus the aerial rate of oxygen uptake is between 28 and 78% of the aquatic rate. 3. These species differences are related to the degree of shell gape during air exposure. 4. All species show an apparent oxygen debt after exposure to air, the extent of which is not simply related to either the level of aerobic respiration or the degree of anaerobiosis during exposure. 5. Anaerobic end-products accumulate in the tissues of Mytilus during aerial exposure, but not in Cardium. 6. The relative energy yields by aerobic and anaerobic means in M. edulis are discussed.

Measurement Of The Responses Of Individuals To Environmental-Stress And Pollution - Studies With Bivalve Mollusks

Certain physiological differences between individuals in different populations of the mussel, Mytilus edulis, are described. In particular, the scope for growth differs in space and time and may be used to assess the animals' physiological condition. When the required measurements are made in the field, the rates of growth predicted from the physiological data agree well with observed rates of growth. An alternative approach utilizes mussels transplanted to various waters, with indices of condition then measured in the laboratory under standard conditions; an example of this approach is illustrated. Laboratory experiments are used to equate various levels of physiological condition with fecundity, in an attempt to equate physiological effects on the individual with likely population damage. A cytochemical index of stress is described, based on the latency of lysosomal enzymes; spatial variability in this index, and its relation with the scope for growth, are discussed. Finally, the results of some experiments on the effects of petroleum hydrocarbons on mussels are described and the presence of inducible activity of NADPH-dependent tetrazolium reductase in the blood cells is demonstrated. Certain considerations that apply in adopting similar measurements of biological effects of pollution in environmental monitoring programmes are discussed.

Physiological-Responses Of Mytilus-Edulis L To Parasitic Infestation By Mytilicola-Intestinalis

Various levels of infestation by Mytilicola had no effect on the rates of oxygen consumption by Mytilus edulis in laboratory experiments. However, high levels of infestation (> 10 parasites per mussel) caused a depression in the feeding rate of the host at high temperatures (22° or 23° C) and low ration (maintenance or sub-maintenance). This depression of feeding resulted in a decline in the scope for growth, which would result in time in a decline in the “condition” of the host. It is concluded that similar effects may occur in the field when large numbers of small parasites are present at a time of high metabolic demand and low food availability.

Physiological Ecology Of 2 Populations Of Mytilus-Edulis-L

Seasonal cycles in the rates of oxygen consumption, feeding, absorption efficiency and ammonia-nitrogen excretion in two populations of Mytilus edulis were measured in the field under ambient conditions and related to body size, the gametogenic cycle, the concentration of suspended particulate matter in the water and temperature. Relationships between the various physiological variables are also considered and protein and energy budgets estimated. Both the “scope for growth” and the “relative maintenance cost” were seasonally variable, demonstrating a minimum capacity for growth in the winter and a maximum capacity in the summer. In one population subjected to abnormally high temperatures in the winter the scope for growth was negative for four or five months between January and May. These population differences are discussed and the potential for using physiological integrations in intra-specific comparisons of fitness is identified.

Responses Of Mytilus-Edulis L To Low Oxygen-Tension - Acclimation Of Rate Of Oxygen-Consumption

1. Mytilus edulis acclimated its rates of oxygen consumption when maintained at reduced oxygen tensions for periods in excess of five days. 2. Acclimation was complete down to approximately 55 mm Hg PO2 at slightly lower oxygen tensions (51, 49 and 43 mm Hg) acclimation was complete in one experiment and partial in two others. 3. The capacity to acclimate oxygen consumption was not affected by a reduction in ration nor by an increase in temperature (10 to 22 °C). 4. Mussels that were acclimated to reduced oxygen tension (40–80 mm Hg), and then exposed to P O 2 of less than 20 mm Hg for two or five hours, had depressed rates of oxygen uptake when subsequently “recovered” to 40–80 mm Hg. 5. These results are discussed in the context of biochemical studies of anaerobic metabolism in mussels from the same experiments.