Mytilus Galloprovincialis Lmk Research Articles

Variation of the defence mechanisms in two groups of mussels, Mytilus galloprovincialis Lmk. Seasonal and environmental effects — preliminary results

Hemolymph parameters of mussels from two locations in the Ria de Vigo (N.W. Spain) were studied. Hemolymph proteins, lysozyme, agglutinin levels, and the total number of hemocytes varied according to the season and the locality.

Fructose-1,6-bisphosphatase in mantle of the sea mussel Mytilus galloprovincialis Lmk.—III. Seasonal variation of enzymatic activity

1. 1. Fructose-1,6-bisphosphatase (FBPase-1) from the mantle and the posterior adductor muscle (PAM) of Mytilus galloprovincialis Lmk. was investigated over almost 2 years for changes in specific activity and the apparent Michaelis constant ( K m) for Fru-1,6-P 2 (purified enzyme preparations). 2. 2. The specific activity of the mantle changed, peaking in a period between August and November. 3. 3. The K m values for the substrate changed seasonally being low during the first part of the year (January–May) and high in the period between October and November. 4. 4. The changes in mantle FBPase-1 activity were discussed in relation to the effect of modulators and the possible seasonally covalent modification of the enzyme. 5. 5. No statistical changes were detected in posterior adductor muscle FBPase-1, which is in keeping with the glycolytic role suggested for the tissue.

Influence of stock and culture site on growth rate and mortality of mussels ( Mytilus galloprovincialis Lmk.) in Galicia, Spain

The influence of stock and culture site on growth rate and mortality was investigated in populations of Mytilus galloprovincialis Lmk. cultivated in the area of greatest mussel production in the world (Galicia, N.W. Spain). The experimental results indicate that variations in mortality, from May to August, of mussel seed are mostly determined by the populations selected as source of seed. On the other hand, differences in growth rate over this 3-month period are mainly explained by two components of spatial variation; a site component (variation among rafts) and a micro-site component (variation within raft). In addition, differences in growth rate between the fore and the aft part of the rafts (micro-site component) were clearly higher than differences among rafts placed in distinct growing sites (site component). These results are discussed in connection with the role of both the selection of the source of seed and the management of rafts in the improvement of mussel aquaculture in Spain.

Fructose-1,6-bisphosphatase in the mantle of the sea mussel Mytilus galloprovincialis Lmk—II. Regulation by its effectors

1. 1. Fructose-2,6-bisphosphate and AMP each acted as mixed inhibitors of FBPase 1 from mussel mantle, whereas the mechanism of inhibition in each case is different. 2. 2. The joint action of Fru-2,6-P 2 and AMP is a synergistic inhibition of FBPase 1. 3. 3. In the absence of effectors, EDTA activated FBPase 1 from the mantle of mussels. The inhibitors cancel the activation processes performed by EDTA. 4. 4. The results suggested that in vivo mussel mantle FBPase 1 displays a reduced enzymatic activity. This result is in keeping with the supposed regulatory role played by the enzyme.

Consequences of keepingMytilus in the laboratory as assessed by different cellular condition indices

Mytilus galloprovincialis Lmk. were maintained in the laboratory for three months in a semicontinuous water flow system. Animals were fed a commercial filter-feeder food and sampled after 0, 21, 35, 49, 77, and 91 days. In order to establish whether laboratory conditions and the food used were deleterious to mussels, their health status was assessed by quantifying different histological parameters of the digestive gland tissue. It was concluded that mussels kept for more than 35 days under the described laboratory conditions showed signs of stress presumably caused by the reproductive state of the mussels investigated. The food used and the nutrition-related health status of the animals were adequate, as shown by transmission electron microscopical studies after the 91-day maintenance period. A stress response was also evoked by a 10-day starvation period, which was reflected by an increased proportion of type I and type IV digestive tubules, and a reduced “Mean Epithelial Thickness” (MET). Finally, the results demonstrate the sensitivity of quantitative histological diagnosis in comparison to subjective tubule grading procedures in the assessment of the degree of stress experienced by mussels.

Diseases and parasites of rafted mussels (Mytilus galloprovincialis Lmk): preliminary results

A detailed histopathology-based survey of a total of 330 cultured mussels collected from three locations on mussel rafts in the Ria de Arosa (NW, Spain) was carried out over a 1-year period between 1985 and 1986. The populations were “healthy” at the time of sampling. The commonest parasites found in histology were Rickettsiae (up to 50% of histological samples demonstrated clear “inclusions”), the AscetosporanMarteilia (possiblyM. maurini) (up to 35%), and the “redworm” copepodMytilicola intestinalis (up to 80%). A gill ciliate similar toAncistrum mytili was found on all samples examined, ranging in frequency from 60–95%. Specific host-tissue reponses were detected in association with the plasmodial and spore stages ofMarteilia sp. infections, as well as with ovarian infection by the microsporidian parasiteSteinhausia mytilovum, and there was a marked haemocyte encapsulation response to tissue penetration by a copepod. No tissue responses could be detected in association with the other parasites observed.

ACTH-like molecules in gastropod molluscs: a possible role in ancestral immune response and stress

The presence of immunoreactive ACTH molecules on phagocytic cells from the freshwater snails Planorbarius corneus and Lymnaea stagnalis was shown by cytofluorimetric analysis. The role of ACTH in phagocytosis and in the release of biogenic amines, two biological responses that may be taken as ancestral types of immune response and stress, respectively, has also been evaluated. ACTH markedly increased the phagocytosis of Staphylococcus aureus by P. corneus haemocytes and caused the release of biogenic amines from such cells into the serum. These data, as well as tracing the ancestral physiological role of ACTH, favour the hypothesis that immune and neuroendocrine systems share a common evolutionary origin.

The physiological energetics of mussels ( Mytilus galloprovincialis Lmk) from different cultivation rafts in the Ria de Arosa (Galicia, N.W. Spain)

Physiological components of growth (clearance and ingestion rates, absorption efficiencies and metabolic rates) were determined in specimens of mussels ( Mytilus galloprovincialis) from several cultivation rafts in the Ria de Arosa (Galicia, Spain). Choice of raft location within the estuary was intended to provide an oceanic-terrestrial gradient of conditions. Experiments were performed directly on the raft, under natural conditions of food availability. Water was pumped to feeding trays from two different points (front and back) to account for the variability in seston concentration associated with the filtering activity of the hanging culture. Food concentration was found to be highly variable (0.35 to 1.01 mg POM l −1), the main differences being accounted for by site characteristics. Conversely, food quality (here defined as mg POM per mm 3 of packed particles) experienced minor variations (0.59 to 0.71), with the sole exception of the innermost site studied (quality 0.43). Absorption efficiencies were clearly dependent on food quality and could be adequately modelled as an exponential function of that viriable. The scope for growth (SFG) measured at the front of the raft was consistently higher than at the back and confirmed empirical evidence on growth rates. This result does not merely reflect improved feeding conditions in the input area but associated effects of increased clearance rates and absorption efficiencies exhibited by mussels from the front of the raft. On the other hand, raft positioning within the estuary appears to induce noticeable differences in the feeding behaviour of mussels, as evidenced by higher clearance rates determined in more oceanic areas.

Evidence of selective mortality in favour of the Mytilus galloprovincialis Lmk phenotype in British mussel populations

Samples of mussels (Mytilus) were collected from 17 localities within hybrid zones of Mytilus edulis and Mytilus galloprovincialis in south-west and north-east England. The study of two polymorphic allozyme loci (esterase-D and octopine dehydrogenase), which are partially diagnostic for the two forms of mussel, reveal the existence of widespread length-dependent allele frequency variation. Larger mussels tend to have a higher frequency of alleles characteristically at high frequency in Mytilus galloprovincialis. Also at a given shell length galloprovincialis alleles have a higher frequency higher up the shore. Computer simulation is used to demonstrate that length-dependent variation may be generated not only by differential mortality but also by differential growth and in models including or excluding immigration. Evidence supports the hypothesis that selective mortality acting in favour of the galloprovincialis phenotype within hybrid populations in Britain is balanced by immigration of the more abundant Mytilus edulis.

Modulation of glycolysis in mantle tissue of Mytilus galloprovincialis Lmk

1. 1. The influence of physical and nutritional factors on the glycolytic pathway in the mantle of the sea mussel Mytilus galloprovincialis Lmk, was studied. 2. 2. The most sensitive markers of the flow throughout the pathway, were the energy charge and the concentrations of glucose and fructose 2,6-bisphosphate. 3. 3. Glycolysis was clearly stimulated by adding glucose to the seawater and by reducing the environmental temperature to 4°C. Glyconeogenesis was stimulated by adding succinate, propionate or alanine to the seawater.

Fructose-1,6-bisphosphatase in mantle of the sea mussel Mytilus galloprovincialis Lmk—I. Purification and ion requirements

1. 1. The enzyme fructose-1,6-bisphosphatase was purified from the mantle of the sea mussel Mytilus galloprovincialis Lmk. The purified enzyme showed a single band in SDS-polyacrylamide gel electrophoresis. The mol. wt and subunit mol. wt of the enzyme were 105,000 and 27,000, respectively. 2. 2. Divalent cations are essential for the enzyme activity. In the absence of chelating agents, FBPase 1 exhibits hyperbolic kinetics with respect to Mn 2+, Zn 2+ and Mg 2+. The K m for Mg 2+ is lower than the physiological concentration of cation in the tissue, whereas its K m for Mn 2+ and Zn 2+ is greater than the respective in vivo concentrations. 3. 3. The joint action of Mg 2+ and Zn 2+ increases the affinity of the enzyme for the substrate Fru-1,6-P 2, though V max is reduced. 4. 4. Na + strongly inhibits the enzyme even at very low concentrations. K + has no effect whatsoever.

Phosphofructokinase in the mantle of the sea mussel Mytilus galloprovincialis Lmk.

AbstractPhosphofructokinase (PFK) from the mantle of Mytilus galloprovincialis Lmk. was purified 302‐fold with a yield of 27%. The enzyme proved to be a 340,000‐dalton oligomer comprising four identical 85,000‐dalton subunits.Like other phosphofructokinases, the enzyme behaved cooperatively with fructose 6‐phosphate and was inhibited by high concentrations of ATP.The fall in pH value produces a decrease of enzyme affinity for Fru 6‐P and for the activator AMP, together with a greater inhibition by ATP.AMP, cyclic AMP, and fructose 2,6‐bisphosphate increased the affinity of mussel mantle PFK for Fru 6‐P and decreased the inhibition by ATP, while ammonium ions activated the enzyme increasing only the Vmax. Phosphoenolpyruvate acted as an inhibitor, decreasing the affinity of the enzyme for Fru 6‐P.

Seasonal variations in glycolysis in Mytilus galloprovincialis Lmk

1. 1. In the hepatopancreas and mantle of the sea mussel Mytilus galloprovincialis Lmk glycolysis shows seasonal variations. 2. 2. In both these tissues, glycolytic activity shows a maximum in winter and a minimum in summer. 3. 3. Smaller fluctuations also take place in the posterior adductor muscle. 4. 4. In all three tissues, Fru 2,6-P 2 indicates the direction and strength of glycolysis, correlating well with other parameters such as energy charge or the phosphoenolpyruvate/pyruvate ratio. 5. 5. In the posterior adductor muscle, however, Fru 2,6-P 2 does not correlate with the MAR/K eq ratio from phosphofructokinase owing to the synergic activation of the enzyme by both Fru 2,6-P 2 and AMP.

Kinetic studies on the reaction catalysed by phosphofructokinase from Mytilus galloprovincialis (Lamarck)

The dependence of the initial rate on the concentration of MgATP 2− and fructose-6-phosphate, its behaviour with the alternative substrates MgGTP 2− and MgITP 2- and the inhibition patterns by its products, suggest that the reaction catalysed by phosphofructokinase from the mantle tissue of the mussel Mytilus galloprovincialis Lmk, involves a Theorell-Chance mechanism in which MgATP 2− is the first substrate to bind to the enzyme.

Sister-chromatid exchange in developing eggs of Mytilus galloprovincialis Lmk. (bivalvia)

A simple and rapid experimental technique for detecting SCE in developing eggs of Mytilus galloprovincialis Lmk. (Bivalvia) was set up. Eggs, fertilized in the laboratory, were treated with nitrilotriacetic acid (NTA), HgCl 2 and HgCl 2 plus NTA (1 : 1). Results confirm the high genotoxicity of mercury, indicating an absence of activity by NTA and a lack of interaction between NTA and the metal. Eggs from mussels collected in two stations characterized by different levels of sea-waste and hydrocarbon pollution presented a significant difference in their SCE frequencies. This indicates that a genetic effect can also be produced in gametes. This system may be used for laboratory studies as well as for monitoring the environmental genotoxicity of marine pollutants.

A Comparative Study of the Chromosomes of Mytilus Edulis and Mytilus Galloprovincialis

The exact form of the taxonomic relationship between the common or blue mussel, Mytilus edulis L., and Mytilus galloprovincialis Lmk, the Mediterranean mussel, has been the subject of considerable scientific interest in recent years (for a review see Gosling, 1984). While the origins of this separation into two species rests with the original descriptions by Linnaeus and Lamarck (e.g. Soot-Ryen, 1955), interest was stimulated in recent times through the discovery by Hepper (1957) of an ‘unusual’ type of mussel at Padstow in Cornwall which, on the basis of morphological criteria, he identified as M. galloprovincialis (see also Lewis & Seed, 1969). This discovery was followed by a series of electrophoretic investigations providing evidence that the so-called ‘Padstow mussel’ exhibits genetic affinities with M. galloprovincialis from the Mediterranean (Ahmad & Beardmore, 1976; Skibinski, Ahmad & Beardmore, 1978; Skibinski, Cross & Ahmad, 1980). In her recent review paper on the systematic status of M. galloprovincialis in western Europe, Gosling (1984) considers information from morphological, cytological, immunological, electrophoretic and hybridization studies and concludes that M. galloprovincialis is a ‘form’ or ecotype of M. edulis.

Sexual differences in the composition and metabolism of lipids in the mantle of the mussel Mytilus galloprovincialis LMK (Mollusca: Bivalvia)

Studies carried out on the different species of lipids in the mantle of mussels ( M. galloprovincialis) during the prespawning period have revealed significant differences between males and females. 1. 1. The total lipid content of female mantle is twice as high as in the male mantle, the difference resulting from the triacylglycerides (lipidic granules in oocytes). Total phospholipids and cholesterol are similar in both sexes as is the occurrence of fatty acids 16:0, 20:5ω3 and 22:6ω3. 2. 2. The differences between 16:0/16:1 ratio in the phospholipids of females and males show that the desaturase enzyme may not have the same activity in both sexes. The acylation-deacylation cycle for the phospholipid biosynthesis is probably highly active in this tissue. 3. 3. Experiments carried out with labeled glycerol have shown that in the male mantle, phosphatidylinositol (PI) and triacylglycerols have a higher and phosphatidylcholine (PC) a lower renewal rate compared to female mantle. The ratio of the specific activities of PI/PC is correlated with sexual stages in the female mantle and increases during vitellogenesis.

Seasonal variations in biochemical composition and condition index of cultured mussels ( Mytilus galloprovincialis Lmk) in the Lagoon of Venice (North Adriatic)

Seasonal changes in the main biochemical components and in the condition index of cultured mussels ( Mytilus galloprovincialis Lmk) from the Venice Lagoon have been followed during the period October 1979–August 1981. Carbohydrates (2–32%) show winter minima and summer maxima, while proteins (30–52%) have a rather irregular pattern. Lipids (2–13%) and condition index exhibit an annual cycle with two minima (late spring; autumn-winter) and two maxima (early spring; summer). Seasonal variations of biochemical composition and condition index are discussed in connection with the reproductive cycle and some environmental parameters such as temperature and phytoplankton availability. The comparison between the present data and those from other geographic areas confirms the peculiarity of the environment of the Venice Lagoon.

Mytilus galloprovincialis Lmk. in Southern Africa

The Mediterranean mussel, Mytilus galloprovincialis Lmk. has been identified on the west coast of southern Africa using morphological and biochemical-genetic comparisons with samples of “pure” M. edulis L. from Denmark and M. galloprovincialis from the Mediterranean coast of Spain. Our results show that the southern African Mytilus more closely resembles M. galloprovincialis in anterior adductor, posterior adductor and hinge size. It also has a more ventrally located maximal shell width like the Mediterranean mussel. The electrophoretic examination of 23 proteins showed that many alleles diagnostic for M. galloprovincialis appeared in the southern African Mytilus. Nei's genetic distance between the southern African Mytilus and M. galloprovincialis was 0.010 ± 0.004 and the average genetic distance between these samples and M. edulis was 0.162 ± 0.077. The presence of M. galloprovincialis in southern Africa could be explained by biogeographic dispersal along the west coast of Africa during Pleistocene cooling, or by a recent inadvertant or intentional introduction by man. To test these two hypotheses, we examined ≈750 mussel shells collected from Koi-san middens and ≈350 shells from a raised-beach deposit all located on the west coast of Cape Province, South Africa. The ages of these deposits range from 1500 yr to 120000 yr and pre-date the arrival of Europeans to the Cape. This examination did not reveal any shells of Mytilus. We, therefore, conclude that the introduction of M. galloprovincialis to southern Africa was a recent event. We suggest that, since the first confirmed reference to Mytilus in southern Africa was made from a 1972 collection, the introduction occurred within the last two decades.

Reproductive cycle of the mussel (Mytilus galloprovincialisLmk) in Venice Lagoon (North Adriatic)

Abstract The reproductive cycle of Mytilus galloprovincialis Lmk cultured in Venice Lagoon has been studied from 1979 to 1982. Histology of the gonads shows that the gametes are ripe from September to May, when several spawnings occur with a peak at the end of winter (January -February). Reproductive activity is quiescent between July and August but release of gametes is possible even in summer, if only to a limited extent.