Byssus production rate of the White Sea blue mussel <Emphasis Type="Italic">Mytilus edulis</Emphasis> (Linnaeus, 1758) in the presence of metabolites of some hydrobionts

The byssus production of the blue mussel Mytilus edulis L. was studied in the laboratory in the presence of the metabolites of the following animals: a predator (a starfish Asterias rubens L.) and several species competing with the mussel in White Sea fouling communities (a bivalve Hiatella arctica L. and a solitary ascidian Styela rustica L.). The byssus threads and attachment plaques produced by each mussel per day were counted. The number of byssus threads and plaques was smallest in pure sea water and in the presence of metabolites produced by conspecific individuals.     

Morphology of the Bivalve Mollusks Crenomytilus grayanus and Mytilus coruscus in Relation to Their Spatial Distribution in the Upper Subtidal Zone

The morphology of the shell and byssus threads was studied in two closely related mussel species Crenomytilus grayanus and Mytilus coruscus. The two species differ significantly from each other in the shell shape and in the degrees of development and deformation of byssus threads. These differences, in turn, determine (either directly or indirectly) the differences in strength of the byssal attachment and are discussed in terms of their functional morphology with respect to the spatial distribution of the mussels in marine coastal zones.     

Le collagène du byssus de Mytilus edulis L.

Résumé L'autoradiographie révèle, au niveau du pied, une incorporation massive et sélective de la ³H-Proline dans la glande blanche de Mytilus edulis. Cette étude a permis de suivre le processus qui mène de la synthèse de la sécrétion dans la partie basale des cellules jusqu'a son émission dans le sillon pédieux où elle participe à la formation du filament. La collagénase détruit la presque totalité du marquage, attestant ainsi la nature collagénique du produit sécrété. Les autres glandes pédieuses ainsi que la glande du byssus proprement dite, située à la base du pied, montrent une incorporation très faible, sans commune mesure avec celle de la glande blanche. Ceci démontre de façon définitive que le collagène présent dans le filament prend naissance dans cette glande et justifie la dénomination de glande du collagène. Des contrôles réalisés dans différentes régions (bords du manteau, manteau, branchies) montrent que l'injection du précurseur dans le bord palléal constitue une méthode satisfaisante pour marquer de façon relativement rapide et différentielle le collagène de la glande.

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The collagen of the byssus in Mytilus edulis L.II. Autoradiographic study on the incorporation of ³H-Proline

Summary Autoradiographic studies reveal a strong specific incorporation of ³H-Proline in the white gland in the foot of Mytilus edulis. The author could trace the radioactive secretory product from its synthesis in the basal part of the cells down to its outflow into the pedial groove where it takes part in the formation of the filament. Purified collagenase takes out radioactivity from the sections. This observation confirms the collagenous nature of the secretion.The other foot-glands as well as the main byssus gland located at the base of the foot show but a very weak labelling not comparable with that of the white gland. This clearly evidences that the collagen occuring in the filament originates from the latter. The white gland may be properly called: collagen gland.Control sections through different parts of the body (mantle-edge, mantle, gills) confirm that our injection technique of the precursor into the palleal margin is a suitable method for a rather quick and specific labelling of the glandular collagen.

Cette note fait partie d'un travail pour l'obtention d'une thèse de doctorat.     

Mutual effects of several fouling organisms of the White Sea (<Emphasis Type="Italic">Mytilus edulis,Styela rustica</Emphasis>, and <Emphasis Type="Italic">Hiatella arctica</Emphasis>) on their growth rate and survival

The mutual effects of several fouling species (the bivalves Mytilus edulis and Hiatella arctica and a solitary ascidian Styela rustica) on their growth rate and mortality were studied through field experiments. The interactions between S. rustica and H. arctica appeared to be the least antagonistic. In contrast, the mussel was the most “aggressive” species with regard to both competitors. It was observed that the ascidians died, because they were intensively braided and gummed up with the byssus threads of the mussels. However, in some cases the intraspecific competition was stronger than the interspecific one.     

The ultrastructure of the byssal apparatus of Mytilus galloprovincialis

The ultrastructure of the byssus of Mytilus galloprovincialis was analysed by transmission electron microscopy in thin sections of either embedded or frozen samples. All parts of the byssus (stem core laminae, stem outer laminae, threads proximal and distal parts) appear to be formed by the same basic filamentous components organized in different ways at the submicroscopic level and embedded in a variable quantity of matrix. The filaments appear to consist of a central electron-lucent zone (3 nm in diameter), surrounded by an electron-dense rim (total diameter 7 nm). The matrix has a granular or microfilamentous structure. The stem and the threads differ greatly in their submicroscopic organization, but their basic constituents (filaments and matrix) are similar. Peculiar filamentous banded elements (FBE) were found mainly in the stem outer laminae. A relation between the ultrastructure and mechanical properties of the different parts of the byssus was established. The presence of collagen is discussed; since no morphological evidence of any of the known forms of collagen organization was revealed by electron microscopy, it is suggested that byssus collagen may be localized in the matrix and in the FBE.     

Electron probe analysis of strontium in mussel (Bivalvia,Mytilidae) shells: Feasibility of estimating water temperature

Electron microprobe step-scan analyses across the inner nacreous layer of a sectionedMytilus edulis shell revealed no long-term periodic (e.g., seasonal) variation in the concentration of strontium. Similarly, no significant difference was found between a specimen sampled in February (water temperature = 1.3 °C) and one sampled in August (water temperature = 18.0 °C) with regard to the concentration of strontium within the most recently deposited aragonite. Correlation of the amount of strontium within various nacreous regions of the shells of living or fossil mytilids with water temperatures (present or past) is probably not possible through the use of an electron probe, at least to the extent that strontium variation within the nacre ofMytilus edulis is representative of that in nacreous layers of all mytilids.     

Genotypes of<Emphasis Type="Italic"> Mytilus</Emphasis> from waters of different salinity around Bergen,Norway

Samples of Mytilus were collected at eight sites located in and around Bergen, Norway, and analysed by starch gel electrophoresis for the two highly polymorphic loci PGM* and PGI*. The genotype distribution and allele frequencies varied significantly among samples from the different locations. The variations were most significant between localities with full strength seawater and brackish water, and this difference was so large that it indicated the presence of two populations, possibly representing two species. The brackish water mussels may represent the species Mytilus trossulus, while the species Mytilus edulis may be distributed on the outer shores where salinity is normally around 30. Differential survival, as a result of specific adaptation to different salinities, may be the mechanism that maintains the populations (or species) and prevents gene flow between them.Communicated by H.-D. Franke     

Immunocytochemical demonstration of neurotransmitters in the nerve plexuses of the foot and the anterior byssus retractor muscle of the mussel,Mytilus galloprovincialis

Summary Immunocytochemical methods were applied to study the distribution of putative neurotransmitters (5-HT, substance P, GABA, glutamate and aspartate) in the nerve plexuses of the foot and the anterior byssus retractor muscle (ABRM) of Mytilus galloprovincialis (Mollusca, Bivalvia). The foot presents extensive nerve plexuses containing 5-HT and substance P-like immunoreactive material with a similar distribution beneath the surface epithelium, around the vessels and in the glandular regions. Coexistence of the two putative neurotransmitters was observed in a few nerve fibers, Conversely, muscle fibers, both in the foot and in the ABRM, are innervated only by 5-HT-positive fibers, while substance P-like material is present only in the networks of the ABRM epimysial sheath. Immunoreactivity for glutamate and aspartate was not demonstrated, while rare GABA-positive nerve cells and fibers were found only in the foot. The results of this investigation provide a morphological background to previous physiological studies on 5-HT in the nervous system of bivalve molluscs. Moreover, they confirm that the nervous system of Mytilus contains a remarkable amount of a substance related to the vertebrate tachykinin family.     

小黑山岛海域刺参、魁蚶和紫贻贝生境适宜性分析

以小黑山岛临近海域为研究对象,利用生境适宜性指数(habitat suitability index,HSI)模型选划适宜刺参(Stichopus japonicas)、魁蚶(Scapharca broughtonii)和紫贻贝(Mytilus edulis)增殖修复的区域。分别针对每个修复物种筛选出7个生境评价因子,结合专家赋值法和层次分析法确定每个评价因子的权重,利用GIS空间分析模块将现状调查数据进行插值、重分类和栅格计算,绘制研究区域目标种群生境适宜性地图。结果表明:对于刺参和紫贻贝,研究区域均适宜其生长繁殖,同一物种,相同季节在空间上无站位差异,但各季节的生境适宜性分区变化明显;对于魁蚶来说,东北部海域较适宜增殖,其次为西部海域,四季均以较适宜生境为主,仅冬季出现基本适宜生境。水温是造成季节差异的主要因素,底质类型则是引起生境站位差异的重要原因。可为后续的生物多样性保育和生态修复提供基础资料参考。     

Genetic Divergence Detected by ISSR Markers and Characterization of Microsatellite Regions in Mytilus Mussels

The wide distribution of microsatellites in mussels of the Mytilus edulis complex (Mytilidae) enables the analysis of inter-simple-sequence repeat (ISSR) markers. The aim of this investigation was to assess genetic differentiation in six sampling localities distributed along the European Atlantic coast to expose the potential of these markers in genetic studies requiring the detection of low polymorphism and as a source of sequences for developing microsatellite markers. We detected low genetic structuring within each member of the Mytilus edulis complex. Nei and Li distances and AMOVA clustered the individuals studied into two groups. On the basis of these results two sampling localities coming from the M. edulis × M. galloprovincialis mosaic hybrid zone in Western Europe were assigned to one species. On the other hand, mussels of a sampling locality in the Baltic Sea were not significantly different from a pure M. edulis locality supporting an extensive introgression of M. edulis in these individuals. Finally, 148 microsatellites were found in the sequences of 51 ISSR markers, and two polymorphic microsatellite markers were developed.     

Mussel glue fromMytilus californianus Conrad: a comparative study

Summary Marine mussels secrete a byssus in order to attach to solid surfaces in the sea. The polyphenolic protein is the glue in the adhesive plaques of the byssus. InMytilus californianus, the polyphenolic protein has an apparent molecular weight of 85,000±5,000 and is rich in the amino acids lysine, 3,4-dihydroxyphenylalanine, serine, threonine, and hydroxyproline. In composition it resembles the polyphenolic protein ofM. edulis (M _r=125,000), although theM. edulis protein contains significantly less isoleucine and more alanine. Tryptic digestion ofM. californianus polyphenolic protein revealed two types of repeating decapeptides (1) (Ser/Thr)-Thr-(Tyr/Dopa)-Hyp-Hyp-Thr-Dopa-Lys-Hyp-Lys and (2) Ile-(Thr/Ser)-(Tyr/Dopa)-Hyp-Hyp-Thr-Dopa-Lys-Hyp-Lys. Residues 2 to 8 are identical with residues 4–10 inM. edulis decapeptides.Abbreviation Dopa 3,4hydroxyphenylalanine     

On the ultrastructure of polypeptide hormone-producing cells in the gut of the ascidian,Ciona intestinalis L. and the Bivalve,Mytilus edulis L.

Summary Ultrastructural evidence has been found for the presence of polypeptide hormone-producing cells in the gut of Ciona intestinalis L. and Mytilus edulis L. which do not appear to have been described before. Due to their localization and ultrastructural characteristics, it is suggested that the cells in Mytilus edulis probably produce an insulin-like substance and that some of these cells in Ciona intestinalis may produce 5-HT (5-Hydroxytryptamine). In each species only one granulated cell type can be observed. The granules, which are electron dense and membrane bound, also show a halo. The average diameter of the granules is 100–200 nm for Ciona and 200–400 nm for Mytilus.I thank Mr. G. Bargsten, M.A., Dept. of Marine Zoology, University of Kiel, for the supply of the animals     

Phenoloxidase (E.C. 1.14.18.1) from the byssus gland of Mytilus edulis: Purification,partial characterization and application for screening products with potential antifouling activities

Although a total ban on the use of TBT coatings is not expected in the short term, there is a growing need for environmentally safe antifouling systems. To assist in the rapid screening of a large number of potential antifouling substances, a method that is simple, efficient and inexpensive is required. The production of byssus threads by the blue mussel, Mytilus edulis, has often been studied for testing the antifouling efficacy of various compounds. The present study reports a new antifouling assay based on the inhibition of purified M. edulis phenoloxidase activity. The method has the advantage of being specific, reliable, sensitive and rapid.     

Effects of temperature,salinity and agitation on byssus thread formation of zebra musselDreissena polymorpha

Byssus thread production ofD. polymorpha under different conditions of temperature, salinity and agitation were studied in the laboratory. The acclimation to salinity and temperature greatly affects the byssus production ofD. polymorpha. Byssus production of mussels was significantly reduced when temperature increased beyond 20°C and decreased below 10°C. Mussels with cut threads (for counting), produced a substantially increased number of threads. However, mussels with uncut byssus threads were comparatively more mobile. Byssus production of mussels did not vary significantly at salinities up to 3. Beyond this salinity byssus production was reduced significantly. Mussels increased their byssus production with increasing frequency of agitation.     

Monoamine-containing structures in the intestines of bivalve molluscs and a polychaete annelid revealed by fluorescence histochemistry

Summary Monoamine-containing elements in the intestines of Bivalvia and Polychaeta species have been found by use of histochemical fluorescence methods according to Falck and Furness. Catecholamine-containing perikarya and fibers are seen within the epithelium and subepithelial layers of the midgut of the bivalves Mytilus edulis, Mya arenaria, Arctica islandica, as well as the polychaete Harmothoe imbricata. In addition, intraepithelial cell bodies and fibers containing serotonin-like substance are present in Mytilus edulis. Results obtained with the Furness method, applied earlier to vertebrates, correlate with those obtained with the Falck method.     

Investigation of the loss of byssus in Mytilus galloprovincialis from mussel farms in the Adriatic Sea

A fungal infection has been found in the mussel Mytilus galloprovincialis from Adriatic Sea mussel farms. The infection ultimately results in the loss of the byssus, with serious consequences for mussel farming yield. The pathogen provokes the progressive destruction of the foot muscles, also damaging related structures such as the intra-organism part of the byssus apparatus, resulting in loss of the thread component. The affected health status of the animal is also sustained by modifications in the digestive gland structure, ranging from hyperactivity to extreme cell death in the tubula. At present, the identity of the harmful fungus is unknown.     

Occurrence ofDinophysis spp. and toxic shellfish in the Northern Adriatic

The dynamics of the toxicity of the musselMytilus galloprovincialis was compared between two different shellfish farms, 5 km apart, but using the same cultivation technique. The main differences concerned the freshwater influx and the open aspect to the Gulf of Trieste. It is suggested that a deep closed bay and abundant fresh water inflow are the two main conditions for the low toxicity levels in mussels and for shorter periods of danger. A detailed study of the phytoplankton samples revealed the presence of eight species ofDinophysis in the area of both shellfish farms. During the period of the DSP outbreak in Slovenia (autumn and winter 1989).D. fortii andD. acuminata were the most frequentDinophysis species. There was a high positive correlation between the onset of mussel toxicity and the appearance ofDinophysis spp.     

Protection against suspended sand: the function of the branchial membrane in the blue mussel Mytilus edulis

Blue mussels (Mytilus edulis) living in estuaries have to cope with varying concentrations of suspended sand. Sand flowing through the inhalant siphons comes into the infrabranchial chamber. The inhalant siphon can be partially closed by the branchial membrane. As a result the inward flow decreases, and suspended sand sinks and can be eliminated. Experiments with mussels from three ecologically different locations showed about the same response of the branchial membrane on contact with suspended sand. The presence and function of the branchial membrane appears to be an adaptation of mussels to their estuarine environment.     

MECHANICAL PROPERTIES OF MUSSEL BYSSUS THREADS

The byssus threads of the common mussel, Mytilus edulis L.,have been tested mechanically and the results from the testsrelated to the ecology of the animal. The threads are mechanicallysimilar to other crystalline polymers such as polyethylene havinga modulus of about 10⁸N m^–2 and a long relaxation time.Resilience of 60% is similar to tendon; ultimate strain is aboutfive times that of tendon at 0.44. The thread is laid down witha prestrain of 10% and so guys the mussel in position. Calculationshows that a mussel with 50 byssus threads would be able toresist all but severe winter storms (Received 1 December 1978;     

A comparative study on the influence of manganese on the bactericidal response of marine invertebrates

Manganese, Mn, is a naturally abundant metal in marine sediments. During hypoxic conditions the metal converts into a bioavailable state and can reach levels that have been shown immunotoxic to the crustacean Nephrops norvegicus. For this species it has previously been shown that exposure to 15 mg L⁻¹ of Mn decreased the number of circulating haemocytes while it for the echinoderm Asterias rubens increased the number of coelomocytes. Here, we compared if five days of exposure to the same concentration of Mn affects the bactericidal capacity of these two species and the mollusc Mytilus edulis when inoculated with the bacterium Vibrio parahaemolyticus. Viable counts of the bacteria were investigated at a time-course post-injection in the blood and the digestive glands of Mn-exposed and un-exposed (controls) animals. Accumulation of Mn was also analyzed in these tissues. When exposed to Mn the haemocyte numbers were significantly reduced in M. edulis and it was shown that the bactericidal capacity was impaired in the mussels as well as in N. norvegicus. This was most obvious in the digestive glands. These two species also showed the highest accumulation of the metal. In A. rubens the bactericidal capacity was not affected and the metal concentration was similar to the exposure concentration. After a recovery period of three days the concentration of Mn was significantly reduced in all three species. However, in M. edulis and N. norvegicus it was still double that of A. rubens which could explain the remaining bactericidal suppression observed in N. norvegicus. This study pointed out that exposure to such Mn-levels that are realistic to find in nature could have effects on the whole organism level, in terms of susceptibility to infections. The effect seemed associated to the accumulated concentration of Mn which differed on species level.