The occurrence and in vitro effects of molecules potentially active in the control of growth in the marine mussel Mytilus edulis L

A molecular with a molecular weight, estimated by gel filtration, of approximately 22 kDa and immunoreactive to anti-human hypophysial growth hormone (hGH) has been identified by radioimmunoassay in the digestive gland and hemolymph of the mussel Mytilus edulis L. The dilution curve of this molecule was parallel to that of hGH, suggesting that the antigenic site of the Mytilus molecule is similar to that of hGH. Immunoreactive fractions resulting from gel filtration failed to stimulate protein synthesis in dispersed mantle-edge cells in vitro. No hGH-immunoreactive material was detected in the cerebral ganglia. It is thus clear that a small protein-synthesis-stimulating factor (PSSF), identified in the cerebral ganglia and hemolymph by its action in vitro on dispersed mantle-edge cells, is not analogous to the Mytilus hGH-immunoreactive molecule. Likewise, a somatostatin-immunoreactive molecule present in the hemolymph of Mytilus did not coelute with PSSF. Evidence is presented that PSSF is a hydrophilic peptide that stimulates DNA, RNA, and protein synthesis and that is not tissue specific. These characteristics suggest that PSSF is a growth hormone.

Comparative effects of the water accommodated fraction of three oils on mussels—1. Survival, growth and gonad development

1. Mussels, Mytilus galloprovincialis, were exposed to the water accommodated fraction (WAF) of two crude oils (types Ural and Maya) and of a commercial lubricant oil for 91 days. Synchronous spectrofluorometry showed that the aromatic hydrocarbon composition of the WAFs obtained from the three oils were significantly different (Maya-WAF heaviest, Ural-WAF lightest). 2. No significant mortality occurred in mussels exposed to the WAFs of the two crude oils, while all the animals exposed to lubricant-WAF died after 49 and 77 days in intermediate and high doses respectively. 3. Flesh and shell growth of mussels exposed to the WAFs was reduced significantly with respect to controls as demonstrated by several size, condition and allometric parameters. The response to petroleum hydrocarbon exposure is not dose-dependent, maximal responses being measured in low (Ural) and intermediate (Maya) doses. This seems to depend on a behavioural reaction (shell valve closure) against high doses of pollutants which may avoid the sublethal damage to some extent. 4. Shell abnormalities or changes in shell thickness were not detected. 5. The histological study of gonad tissue revealed that gamete release is retarded and hemocytic infiltration of mature gonad tissue is increased after exposure to low and intermediate doses of the WAFs. On the other hand, spawning is readily induced under exposure to high doses of the WAFs.

Pharmacology of the serotonin-induced meiosis reinitiation in Spisula solidissima oocytes

Germinal vesicle breakdown (GVBD) is the first visible response of the oocyte of Spisula solidissima to the neurohormone serotonin. Pharmacological characterization of this response was performed by using 24 serotonin-related compounds. Dose-response curves were assessed by quantification of GVBD. Rank orders of potency obtained were among agonists: serotonin greater than 8-hydroxy-2-(di-N-propylamino)tetralin hydrobromide greater than 2-methyl-serotonin greater than 1-(3-trifluoromethylphenyl)piperazine; among antagonists; ritanserin ritanserin greater than ICS205930 greater than mianserin = ketanserin = propranolol greater than metoclopramide = yohimbine greater than spiperone. Various other monoaminergic compounds tested were inefficient, demonstrating the specificity of the oocyte response to serotonin. Transduction mechanisms underlying this response were then investigated. Ca2+ appeared to be involved since serotonin induced an increase in the uptake of 45Ca2+ and since it was inefficient in calcium-free sea water. The absence of synergy between serotonin and KCl suggested that both compounds use a common transduction pathway. Exposure of the oocyte to the protein kinase C activator TPA inhibited serotonin-dependent maturation. Our data thus point to an original, previously uncharacterized pharmacological profile and transduction mechanism by which serotonin induces oocyte meiosis reinitiation in Spisula solidissima.

Mussel culture and the accumulation of domoic acid

The cultured mussel industry of Prince Edward Island had never experienced a toxic disease problem until November of 1987. With the successful use of the long-line culture system, the yearly production of fresh mussels to the gourmet food market had risen to close to 3.2 million pounds (1.46 million kg) of product. The physiology of this sessile bivalve and its method of feeding and location in the estuary leave it prone to the accumulation of a widely distributed biotoxin. Eastern Prince Edward Island became the epicentre of domoic acid-intoxicated mussels as early as 10 November 1987 (retrospective samples) during an intense bloom of the diatom Nitzschia. Mussels were able to accumulate large amounts of the domoic acid with little effect on their own well-being. Despite being in low water temperatures (below 4 degrees C) and under thick ice cover, the levels of the toxin decreased and were undetectable in about 6 weeks. The following year the toxin was detected in much smaller amounts, and the levels of toxin accumulation demonstrated a variable lag time with the increase in concentration of Nitzschia available in the water column. The sales of Prince Edward Island cultured mussels have rebounded to about 140% of the pre-domoic acid crisis.

Interrelationships of heterozygosity, growth rate and heterozygote deficiencies in the coot clam, Mulinia lateralis

Allozyme surveys of marine invertebrates commonly report heterozygote deficiencies, a correlation between multiple locus heterozygosity and size, or both. Hypotheses advanced to account for these phenomena include inbreeding, null alleles, selection, spatial or temporal Wahlund effects, aneuploidy and molecular imprinting. Previous studies have been unable to clearly distinguish among these alternative hypotheses. This report analyzes a large data set (1906 individuals, 15 allozyme loci) from a single field collection of the coot clam Mulinia lateralis and demonstrates (1) significant heterozygote deficiencies at 13 of 15 loci, (2) a correlation between the magnitude of heterozygote deficiency at a locus and the effect of heterozygosity at that locus on shell length, and (3) a distribution of multilocus heterozygosity which deviates from that predicted by observed single-locus heterozygosities. A critical examination of the abovementioned hypotheses as sources of these findings rules out inbreeding, null alleles, aneuploidy, population mixing and imprinting as sole causes. The pooling of larval subpopulations subjected to varying degrees of selection, aneuploidy or imprinting could account for the patterns observed in this study.

The differential contribution by individual enzymes of glycolysis and protein catabolism to the relationship between heterozygosity and growth rate in the coot clam, Mulinia lateralis

The locus-specific effects of heterozygosity upon individual growth rate were determined for 15 polymorphic enzymes among 1906 individuals from a single cohort sample of the marine bivalve Mulinia lateralis. Two measures of individual growth rate (total wet weight and shell length) were made at collection and after a period of growth in the laboratory. The correlation between heterozygosity and growth rate was independently determined for each locus using multiple linear regression, thereby providing a rank of individual locus effects; these differed significantly. The four estimated rankings of relative locus effects (initial length, initial weight, length added in the laboratory, and added weight) were not statistically different. That is, a locus with a large effect of heterozygosity on growth rate in nature had a similarly large effect on laboratory growth rate. The effect of a locus was not related to heterozygosity per se; some highly heterozygous loci had no detectable correlation with growth rate. The data contained two pairs of relatively tightly linked loci; in both cases one locus of a pair had significant effects on growth rate, while the other had no effect. Loci with large and significant correlations with growth rate synthesize enzymes which function in protein catabolism or glycolysis; heterozygosity in enzymes of the pentose shunt, redox balance, or other miscellaneous metabolic roles was not correlated with growth rate. Since the metabolic basis for the correlation is known to derive from individual differences in net energy status, particularly energetic costs of whole-body protein turnover, these data indicate that phenotypic effects (e.g., variation in growth rate) are determined by heterozygosity at the studied genes, not other linked loci.

Aging alterations in the modulation of central dopaminergic cilioinhibition by etorphine in the marine mussel, Mytilus edulis: decrease in the inhibition of presynaptic dopamine release

1. This report further demonstrates that etorphine influences presynaptic dopamine release, which in turn centrally modulates peripheral cilioinhibition. 2. In older animals cilioinhibition has become enhanced due to a lack of responsiveness to endogenous opioids which results in greater dopamine release, causing a higher level of cilioinhibition as demonstrated by challenging the visceral ganglia with etorphine or destroying the dopaminergic component with 6-hydroxydopamine. 3. Only the central cilioinhibitory, not the peripheral inhibitory response, mechanism appears to be altered in older animals. Thus, the alteration appears in the central integrative mechanisms involved with regulating ciliary activity. 4. The KCl-stimulated release of dopamine is unaltered in both young and old organisms, whereas the opiate inhibition of the KCl-stimulated release of dopamine is reduced in older organisms. Thus, the aging-associated alteration is associated with a specific process. 5. The reduction of opioid influence and the resulting enhanced cilioinhibitory activity may make the organisms more susceptible to environmental stress.

Multiple-locus heterozygosity and the physiological energetics of growth in the coot clam, Mulinia lateralis, from a natural population

The relationship between individual energy budgets and multiple-locus heterozygosity at six polymorphic enzyme loci was examined in Mulinia lateralis. Energy budgets were determined by measuring growth rates, rates of oxygen consumption, ammonia excretion and clearance rates. Enzyme genotypes were determined using starch gel electrophoresis. Growth rate and net growth efficiency (the ratio of energy available for growth to total energy absorbed) increased with individual heterozygosity. The positive relationship between observed growth and multiple-locus heterozygosity was associated with a negative relationship between routine metabolic costs and increasing heterozygosity. Reduction in routine metabolic costs explained 60% of the observed increased growth of more heterozygous individuals. When routine metabolic costs were standardized for differences in feeding rates, these standard metabolic costs explained 97% of the differences in growth rate. Lower standard metabolic costs, associated with increasing heterozygosity, have been proposed as a physiological mechanism for the relationship between multiple-locus heterozygosity and growth rate that has been reported for a variety of organisms, ranging in diversity from aspens to humans. This study demonstrates that reduction of standard metabolic costs, at least in clams, accounts for virtually all of the differences in growth rate among individuals of differing heterozygosity.

[Different shell development in Mytilus galloprovincialis in 2 different populations from the Gulf of Naples]

The size frequency distribution, the shell weight, the semilogarythmic growth, the carbonic anhydrase activity has been investigated between two populations of mussels from different sampling zones. Significative differences were found in the parameters investigated between the two populations. The authors conclude that the reason of this morphological and biochemical differences may arise from different natural hydrobiological factors and/or from different pollution of their habitat.

Decrease in the number of high-affinity opiate binding sites during the aging process in Mytilus edulis (Bivalvia)

As Mytilus edulis (Bivalvia) ages, the number of stereospecific opiate binding sites in the visceral ganglia significantly decreases. The number of high-affinity etorphine sites decreased by 30%; the number of naloxone sites decreased by 23%. The affinity of the ligands did not vary with age. In addition, the augmentation by opioids of dopamine levels in the visceral ganglia was less in older animals and was accompanied by a reduced sensitivity of the ganglia to etorphine and DAMA (D-Ala2,Met5-enkephalin-amide).

Glochidiosis of salmonid fishes. IV. Humoral and tissue responses of coho and chinook salmon to experimental infection with Margaritifera margaritifera (L.) (Pelecypoda: Margaritanidae)

Coho salmon (Oncorhynchus kisutch) are more resistant than chinook salmon (O. tshawytscha) to experimental infection with the glochidia of the freshwater mussel Margaritifera margaritifera. Histological sections of gills from coho salmon 16 hr postinfection (p.i.) showed that parasite encystment either did not occur or had progressed incompletely, which accounted for the loss of many glochidia from the gills. The remaining encysted glochidia were sloughed within 2 days (p.i.) by a well-developed hyperplasia. On chinook salmon, the parasites developed normally with no sloughing or hyperplasia. Analysis of blood samples taken from coho salmon at intervals during the infection showed significant increases in hematocrit, hemoglobin, the mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and leukocyte numbers when compared with control fish. In infected chinook salmon only the hematocrit, erythrocyte numbers, and MCV increased while the MCHC decreased. Total plasma protein increased in coho salmon but decreased in chinook salmon during infection. Glochidial antibodies were demonstrated in the blood plasma of coho and chinook salmon 8 to 12 wk p.i. Fewer glochidia attached to the excised gills of coho salmon than to the gills of chinook salmon. Also, the in vitro survival time of parasites in mucus and plasma from coho salmon was less than in the same chinook salmon fluids.

Measurement of the responses of individuals to environmental stress and pollution: studies with bivalve molluscs

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 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.

Glochidiosis of salmonid fishes. II. Comparison of tissue response of coho and chinook salmon to experimental infection with Margaritifera margaritifera (L.) (Pelecypoda: Margaritanidae)

Coho salmon (Oncorhynchus kisutch) are more resistant to experimental infection with the glochidia of the freshwater mussel (Margaritifera margaritifera) than are chinook salmon (Oncorhynchus tshawytscha). Histological sections made at intervals during the infection showed that coho salmon sloughed the parasites from their gills by 4.5 days postinfection, but the parasites remained encysted in the gills of chinook salmon for 12 weeks, when metamorphosis to juvenile mussels was complete. Coho salmon sloughed the parasites by a well-developed hyperplasia. No such pronounced hyperplastic reaction was seen in the gills of chinook salmon.

In situ morphology of nitrifying-like bacteria in aquaculture systems

The in situ microbiota from several aquaculture facilities with active nitrification was examined by transmission electron microscopy of thin sections for the presence of bacteria that contained intracytoplasmic membranes characteristic of the nitrifying bacteria. Colonies of bacteria with the cellular morphology of a species of Nitrosomonas were found to be present in both the culture water and in the biological filter slime of a freshwater chinook salmon (Oncorhynchus tshawytscha) culture system. bacteria in the water possessed the normal nitrosomonas type of ultrastructure, whereas similar bacteria in the slime had an aberrant morphology due to multiple invaginations of the cell wall and cyto-membranes and a significantly greater number of ribosomes. These nitrosomonas-like bacteria lysed during enrichment in commonly used media. Bacteria with the morphology of species of Nitrosomonas and Nitrosococcus were also observed in colonies in the surface slimes of marine culture systems for striped bass (Morone saxatilis) and quahaug (Mercenaria mercenaria).

Slow growth rate of a deep-sea clam determined by 228Ra chronology

The age of a deep-sea clam, Tindaria callistiformis, from 3803 m depth has been determined by 228Ra (6.7 year half-life) chronology of separated size fractions of a captured population. A length of 8.4 mm is attained in about 100 years. Shells of this size fraction show about 100 regularly spaced bands, indicating that the growth feature may be an annual one.

[The toxicity of different crude oils on mussel larva]

Five natural oils of varied origins, mixed with sea water by stirring, have been shown to be toxic for mussel larvae, which have been contaminated during one hour. This toxicity, expressed by the mortality percentage and the growth rate after contamination, was dependent on the type and the concentration of oil. The tests were carried out on 20 h old and 5 days old larvae, and were similar and complementary.