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Morphology of byssal thread in (a, d, g, j) Mytilus coruscus, (b, e, h, k) Crenomytilus grayanus, and (c, f, i, l) Modiolus modiolus (SEM): (a-c) external surface of attachment disk; (d-f) bottom surface of attachment disk; (g-i) distal part of byssal thread; (j-l) proximal part of byssal thread. Scale bar is in μm.
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The adaptation of sessile bivalves to the attached mode of life has been studied using three common mytilid species, Mytilus coruscus, Crenomytilus grayanus, and Modiolus modiolus. This study has shown similar features of organization of byssus and some of its structures associated with their functional significance in these bivalves. Myt. coruscus...
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... exerted on the shell by the environmental hydrodynamic activity (Denny, 1987;Denny et al., 1998). The proximal part of the thread begins behind the cuff (Figs. 1, 2b). According to the microscopy data obtained in this work, a rupture of byssal threads in the studied mytilids most frequently occurs in the proximal part (Figs. 1, 2). In Fig. 4, it is clearly seen that the surface of the thread is covered with numerous transverse folds and furrows oriented almost perpendicular to the thread's longitudinal axis. The thread width varies along its length in each individual and differs both within each species and between them (Figs. 2c, 4). The greatest thread width in the ...
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... (Table 3); the smallest width was in Mod. modiolus, only 50 μm (Table 3). The folded surface of the thread proximal part is outlined by a corrugated edge on both sides. The edge has the form of small, closely spaced folds of a smaller order and can be expressed much more weakly or be absent on one side in some cases, for example, in Mod. modiolus (Fig. 4l). Myt. coruscus (Fig. 4j) has the widest edge, reaching on average 9-30 μm. In C. grayanus and Mod. modiolus, its width varies within 5-16 and 2-5 μm, respectively (Figs. 4k, 4l). The longitudinal furrow runs between the main and small folds, separating the edge (Fig. 4). The degree of compactness of the folds varies along the proximal ...
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... was in Mod. modiolus, only 50 μm (Table 3). The folded surface of the thread proximal part is outlined by a corrugated edge on both sides. The edge has the form of small, closely spaced folds of a smaller order and can be expressed much more weakly or be absent on one side in some cases, for example, in Mod. modiolus (Fig. 4l). Myt. coruscus (Fig. 4j) has the widest edge, reaching on average 9-30 μm. In C. grayanus and Mod. modiolus, its width varies within 5-16 and 2-5 μm, respectively (Figs. 4k, 4l). The longitudinal furrow runs between the main and small folds, separating the edge (Fig. 4). The degree of compactness of the folds varies along the proximal thread part in all three ...
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... edge has the form of small, closely spaced folds of a smaller order and can be expressed much more weakly or be absent on one side in some cases, for example, in Mod. modiolus (Fig. 4l). Myt. coruscus (Fig. 4j) has the widest edge, reaching on average 9-30 μm. In C. grayanus and Mod. modiolus, its width varies within 5-16 and 2-5 μm, respectively (Figs. 4k, 4l). The longitudinal furrow runs between the main and small folds, separating the edge (Fig. 4). The degree of compactness of the folds varies along the proximal thread part in all three mytilid species. Thus, in Myt. coruscus the width of the main transverse folds in the central segment of the proximal part varies, on average, within ...
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... weakly or be absent on one side in some cases, for example, in Mod. modiolus (Fig. 4l). Myt. coruscus (Fig. 4j) has the widest edge, reaching on average 9-30 μm. In C. grayanus and Mod. modiolus, its width varies within 5-16 and 2-5 μm, respectively (Figs. 4k, 4l). The longitudinal furrow runs between the main and small folds, separating the edge (Fig. 4). The degree of compactness of the folds varies along the proximal thread part in all three mytilid species. Thus, in Myt. coruscus the width of the main transverse folds in the central segment of the proximal part varies, on average, within 10-34 μm; in C. grayanus, 3-13 μm; in Mod. modiolus, 2-8 μm (Table 3). For example, in the ...
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... to the comparative analysis, Myt. coruscus has the widest and longest, and better reinforced proximal part of the thread than the other two species (Fig. 4; Table 3). The proximal part apparently damps the mechanical stresses ( Bell and Gosline, 1996;Gos- line et al., 2002;Carrington and Gosline, 2004) caused by the wave impact (Denny, 1987;Denny et al., 1998). Thus, Myt. coruscus is better adapted to habitats in the marine coastal zone with high wave action than C. grayanus and Mod. ...
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... thread is observed in this segment in all three mytilid species. The byssal thread width varies here (Table 3). The distal part begins after the transitional zone (Fig. 2c), immediately behind the proximal part, and ends with the site of transition of the distal part into the attachment disk. The byssal thread surface in the distal part is smooth (Fig. 4). A clearly discernible, dense, rounded longitudinal cord, occupying a lateral position, extends on the surface of one side of the byssal thread (Figs. 2d, 4). In cross section, the byssal thread is flattened in the form of an ellipse (Fig. 2d). A longitudinal furrow runs down the distal part of the byssal thread (Figs. 4g, 4h, 4i). In ...
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... the distal part is smooth (Fig. 4). A clearly discernible, dense, rounded longitudinal cord, occupying a lateral position, extends on the surface of one side of the byssal thread (Figs. 2d, 4). In cross section, the byssal thread is flattened in the form of an ellipse (Fig. 2d). A longitudinal furrow runs down the distal part of the byssal thread (Figs. 4g, 4h, 4i). In Myt. coruscus, the byssal threads have a thicker longitudinal cord and a deeper longitudinal furrow, which are least pronounced in the byssal threads of C. grayanus and Mod. modiolus. The presence of barely noticeable small tubercles and smaller furrows on the thread surface is characteristic of the mussels Myt. coruscus and C. ...
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... a thicker longitudinal cord and a deeper longitudinal furrow, which are least pronounced in the byssal threads of C. grayanus and Mod. modiolus. The presence of barely noticeable small tubercles and smaller furrows on the thread surface is characteristic of the mussels Myt. coruscus and C. grayanus, while in Mod. modiolus the surface is smoother (Figs. 4g, 4h, 4i). The distal part, as a rule, has a variable width in each individual and is the widest in the mussel Myt. coruscus and the thinnest in Mod. modiolus (Table ...
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... site of transition of the distal thread part into the attachment disk is wide and slightly flattened, with furrows and reinforcing cords on the surface being most pronounced in Myt. coruscus; in C. grayanus, the furrows and cords are smaller and much shorter; in Mod. modiolus, they are weakly expressed (Figs. 4a, 4b, 4c). Myt. coruscus has the widest byssal thread in this part as compared to the byssal thread width in the other two mytilid species under study (Table 3). Table 3. Some parameters of byssal threads in Crenomytilus grayanus, Mytilus coruscus, and Modiolus modiolus from the Sea of Japan, as inferred from data of LM and SEM 30 threads were ...
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... is clearly visible to the naked eye (Figs. 1a-1c; 4a-4c). It has the shape of a flattened ellipse-like plate. This ellipse has its longitudinal axis oriented in the direction of the maximum mechanical stress exerted on the byssal thread by wave impact. In Myt. coruscus, the longitudinal axis of the thread is located at an angle to the disk plane (Fig. 4a). In C. grayanus and Mod. modiolus, the disk plane is typically oriented perpendicular to the thread's longitudinal axis (Figs. 4b, 4c). The lower surface of attachment disks repeats the contour of the substrate and by its external structure resembles hardened foam (Figs. ...
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... longitudinal axis oriented in the direction of the maximum mechanical stress exerted on the byssal thread by wave impact. In Myt. coruscus, the longitudinal axis of the thread is located at an angle to the disk plane (Fig. 4a). In C. grayanus and Mod. modiolus, the disk plane is typically oriented perpendicular to the thread's longitudinal axis (Figs. 4b, 4c). The lower surface of attachment disks repeats the contour of the substrate and by its external structure resembles hardened foam (Figs. ...
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... longitudinal axis of the thread is located at an angle to the disk plane (Fig. 4a). In C. grayanus and Mod. modiolus, the disk plane is typically oriented perpendicular to the thread's longitudinal axis (Figs. 4b, 4c). The lower surface of attachment disks repeats the contour of the substrate and by its external structure resembles hardened foam (Figs. ...
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... the disk surface, there are discernible rounded cords (Figs. 4a-4c). All three mytilid species typically have one thick cord running on the disk surface to its edge and oriented anteriorly, towards the shell umbo (Figs. 4a-4c). In addition, the posterior cord, oriented symmetrically to the anterior cord but not reaching the edge of the disk plate, is also usually clearly visible (Figs. 4a-4c). In ...
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... the disk surface, there are discernible rounded cords (Figs. 4a-4c). All three mytilid species typically have one thick cord running on the disk surface to its edge and oriented anteriorly, towards the shell umbo (Figs. 4a-4c). In addition, the posterior cord, oriented symmetrically to the anterior cord but not reaching the edge of the disk plate, is also usually clearly visible (Figs. 4a-4c). In addition, there are one to four lateral, less pronounced thin, short cords. These mytilid species typically differ in the number of cords (Figs. 4a-4c). In Myt. ...
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... rounded cords (Figs. 4a-4c). All three mytilid species typically have one thick cord running on the disk surface to its edge and oriented anteriorly, towards the shell umbo (Figs. 4a-4c). In addition, the posterior cord, oriented symmetrically to the anterior cord but not reaching the edge of the disk plate, is also usually clearly visible (Figs. 4a-4c). In addition, there are one to four lateral, less pronounced thin, short cords. These mytilid species typically differ in the number of cords (Figs. 4a-4c). In Myt. coruscus, there can be up to six of them; in C. grayanus and Mod. modiolus, no more than four. In the former species, attachment disks with two, three, four, five, and six ...
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... towards the shell umbo (Figs. 4a-4c). In addition, the posterior cord, oriented symmetrically to the anterior cord but not reaching the edge of the disk plate, is also usually clearly visible (Figs. 4a-4c). In addition, there are one to four lateral, less pronounced thin, short cords. These mytilid species typically differ in the number of cords (Figs. 4a-4c). In Myt. coruscus, there can be up to six of them; in C. grayanus and Mod. modiolus, no more than four. In the former species, attachment disks with two, three, four, five, and six cords are found, respectively, in 2, 38, 43, 7, and 10% of cases. In C. grayanus, disks with two, three, and four cords account for, respectively, 30, 50, ...
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... results of detailed study have convincingly shown (Fig. 4) that C. grayanus, Myt. coruscus, and Mod. modiolus substantially differ in the byssus structure. In the mytilids studied, these differences are expressed as the intensity of development of certain parts of byssal threads and reinforcing cords on the surface of attachment disks and byssal threads that determine the strength of mussel ...
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... exerted on the shell by the environmental hydrodynamic activity (Denny, 1987;Denny et al., 1998). The proximal part of the thread begins behind the cuff (Figs. 1, 2b). According to the microscopy data obtained in this work, a rupture of byssal threads in the studied mytilids most frequently occurs in the proximal part (Figs. 1, 2). In Fig. 4, it is clearly seen that the surface of the thread is covered with numerous transverse folds and furrows oriented almost perpendicular to the thread's longitudinal axis. The thread width varies along its length in each individual and differs both within each species and between them (Figs. 2c, 4). The greatest thread width in the ...
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... (Table 3); the smallest width was in Mod. modiolus, only 50 μm (Table 3). The folded surface of the thread proximal part is outlined by a corrugated edge on both sides. The edge has the form of small, closely spaced folds of a smaller order and can be expressed much more weakly or be absent on one side in some cases, for example, in Mod. modiolus (Fig. 4l). Myt. coruscus (Fig. 4j) has the widest edge, reaching on average 9-30 μm. In C. grayanus and Mod. modiolus, its width varies within 5-16 and 2-5 μm, respectively (Figs. 4k, 4l). The longitudinal furrow runs between the main and small folds, separating the edge (Fig. 4). The degree of compactness of the folds varies along the proximal ...
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... was in Mod. modiolus, only 50 μm (Table 3). The folded surface of the thread proximal part is outlined by a corrugated edge on both sides. The edge has the form of small, closely spaced folds of a smaller order and can be expressed much more weakly or be absent on one side in some cases, for example, in Mod. modiolus (Fig. 4l). Myt. coruscus (Fig. 4j) has the widest edge, reaching on average 9-30 μm. In C. grayanus and Mod. modiolus, its width varies within 5-16 and 2-5 μm, respectively (Figs. 4k, 4l). The longitudinal furrow runs between the main and small folds, separating the edge (Fig. 4). The degree of compactness of the folds varies along the proximal thread part in all three ...
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... edge has the form of small, closely spaced folds of a smaller order and can be expressed much more weakly or be absent on one side in some cases, for example, in Mod. modiolus (Fig. 4l). Myt. coruscus (Fig. 4j) has the widest edge, reaching on average 9-30 μm. In C. grayanus and Mod. modiolus, its width varies within 5-16 and 2-5 μm, respectively (Figs. 4k, 4l). The longitudinal furrow runs between the main and small folds, separating the edge (Fig. 4). The degree of compactness of the folds varies along the proximal thread part in all three mytilid species. Thus, in Myt. coruscus the width of the main transverse folds in the central segment of the proximal part varies, on average, within ...
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... weakly or be absent on one side in some cases, for example, in Mod. modiolus (Fig. 4l). Myt. coruscus (Fig. 4j) has the widest edge, reaching on average 9-30 μm. In C. grayanus and Mod. modiolus, its width varies within 5-16 and 2-5 μm, respectively (Figs. 4k, 4l). The longitudinal furrow runs between the main and small folds, separating the edge (Fig. 4). The degree of compactness of the folds varies along the proximal thread part in all three mytilid species. Thus, in Myt. coruscus the width of the main transverse folds in the central segment of the proximal part varies, on average, within 10-34 μm; in C. grayanus, 3-13 μm; in Mod. modiolus, 2-8 μm (Table 3). For example, in the ...
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... to the comparative analysis, Myt. coruscus has the widest and longest, and better reinforced proximal part of the thread than the other two species (Fig. 4; Table 3). The proximal part apparently damps the mechanical stresses ( Bell and Gosline, 1996;Gos- line et al., 2002;Carrington and Gosline, 2004) caused by the wave impact (Denny, 1987;Denny et al., 1998). Thus, Myt. coruscus is better adapted to habitats in the marine coastal zone with high wave action than C. grayanus and Mod. ...
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... thread is observed in this segment in all three mytilid species. The byssal thread width varies here (Table 3). The distal part begins after the transitional zone (Fig. 2c), immediately behind the proximal part, and ends with the site of transition of the distal part into the attachment disk. The byssal thread surface in the distal part is smooth (Fig. 4). A clearly discernible, dense, rounded longitudinal cord, occupying a lateral position, extends on the surface of one side of the byssal thread (Figs. 2d, 4). In cross section, the byssal thread is flattened in the form of an ellipse (Fig. 2d). A longitudinal furrow runs down the distal part of the byssal thread (Figs. 4g, 4h, 4i). In ...
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... the distal part is smooth (Fig. 4). A clearly discernible, dense, rounded longitudinal cord, occupying a lateral position, extends on the surface of one side of the byssal thread (Figs. 2d, 4). In cross section, the byssal thread is flattened in the form of an ellipse (Fig. 2d). A longitudinal furrow runs down the distal part of the byssal thread (Figs. 4g, 4h, 4i). In Myt. coruscus, the byssal threads have a thicker longitudinal cord and a deeper longitudinal furrow, which are least pronounced in the byssal threads of C. grayanus and Mod. modiolus. The presence of barely noticeable small tubercles and smaller furrows on the thread surface is characteristic of the mussels Myt. coruscus and C. ...
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... a thicker longitudinal cord and a deeper longitudinal furrow, which are least pronounced in the byssal threads of C. grayanus and Mod. modiolus. The presence of barely noticeable small tubercles and smaller furrows on the thread surface is characteristic of the mussels Myt. coruscus and C. grayanus, while in Mod. modiolus the surface is smoother (Figs. 4g, 4h, 4i). The distal part, as a rule, has a variable width in each individual and is the widest in the mussel Myt. coruscus and the thinnest in Mod. modiolus (Table ...
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... site of transition of the distal thread part into the attachment disk is wide and slightly flattened, with furrows and reinforcing cords on the surface being most pronounced in Myt. coruscus; in C. grayanus, the furrows and cords are smaller and much shorter; in Mod. modiolus, they are weakly expressed (Figs. 4a, 4b, 4c). Myt. coruscus has the widest byssal thread in this part as compared to the byssal thread width in the other two mytilid species under study (Table 3). Table 3. Some parameters of byssal threads in Crenomytilus grayanus, Mytilus coruscus, and Modiolus modiolus from the Sea of Japan, as inferred from data of LM and SEM 30 threads were ...
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... is clearly visible to the naked eye (Figs. 1a-1c; 4a-4c). It has the shape of a flattened ellipse-like plate. This ellipse has its longitudinal axis oriented in the direction of the maximum mechanical stress exerted on the byssal thread by wave impact. In Myt. coruscus, the longitudinal axis of the thread is located at an angle to the disk plane (Fig. 4a). In C. grayanus and Mod. modiolus, the disk plane is typically oriented perpendicular to the thread's longitudinal axis (Figs. 4b, 4c). The lower surface of attachment disks repeats the contour of the substrate and by its external structure resembles hardened foam (Figs. ...
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... longitudinal axis oriented in the direction of the maximum mechanical stress exerted on the byssal thread by wave impact. In Myt. coruscus, the longitudinal axis of the thread is located at an angle to the disk plane (Fig. 4a). In C. grayanus and Mod. modiolus, the disk plane is typically oriented perpendicular to the thread's longitudinal axis (Figs. 4b, 4c). The lower surface of attachment disks repeats the contour of the substrate and by its external structure resembles hardened foam (Figs. ...
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... longitudinal axis of the thread is located at an angle to the disk plane (Fig. 4a). In C. grayanus and Mod. modiolus, the disk plane is typically oriented perpendicular to the thread's longitudinal axis (Figs. 4b, 4c). The lower surface of attachment disks repeats the contour of the substrate and by its external structure resembles hardened foam (Figs. ...
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... the disk surface, there are discernible rounded cords (Figs. 4a-4c). All three mytilid species typically have one thick cord running on the disk surface to its edge and oriented anteriorly, towards the shell umbo (Figs. 4a-4c). In addition, the posterior cord, oriented symmetrically to the anterior cord but not reaching the edge of the disk plate, is also usually clearly visible (Figs. 4a-4c). In ...
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... the disk surface, there are discernible rounded cords (Figs. 4a-4c). All three mytilid species typically have one thick cord running on the disk surface to its edge and oriented anteriorly, towards the shell umbo (Figs. 4a-4c). In addition, the posterior cord, oriented symmetrically to the anterior cord but not reaching the edge of the disk plate, is also usually clearly visible (Figs. 4a-4c). In addition, there are one to four lateral, less pronounced thin, short cords. These mytilid species typically differ in the number of cords (Figs. 4a-4c). In Myt. ...
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... rounded cords (Figs. 4a-4c). All three mytilid species typically have one thick cord running on the disk surface to its edge and oriented anteriorly, towards the shell umbo (Figs. 4a-4c). In addition, the posterior cord, oriented symmetrically to the anterior cord but not reaching the edge of the disk plate, is also usually clearly visible (Figs. 4a-4c). In addition, there are one to four lateral, less pronounced thin, short cords. These mytilid species typically differ in the number of cords (Figs. 4a-4c). In Myt. coruscus, there can be up to six of them; in C. grayanus and Mod. modiolus, no more than four. In the former species, attachment disks with two, three, four, five, and six ...
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... towards the shell umbo (Figs. 4a-4c). In addition, the posterior cord, oriented symmetrically to the anterior cord but not reaching the edge of the disk plate, is also usually clearly visible (Figs. 4a-4c). In addition, there are one to four lateral, less pronounced thin, short cords. These mytilid species typically differ in the number of cords (Figs. 4a-4c). In Myt. coruscus, there can be up to six of them; in C. grayanus and Mod. modiolus, no more than four. In the former species, attachment disks with two, three, four, five, and six cords are found, respectively, in 2, 38, 43, 7, and 10% of cases. In C. grayanus, disks with two, three, and four cords account for, respectively, 30, 50, ...
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... results of detailed study have convincingly shown (Fig. 4) that C. grayanus, Myt. coruscus, and Mod. modiolus substantially differ in the byssus structure. In the mytilids studied, these differences are expressed as the intensity of development of certain parts of byssal threads and reinforcing cords on the surface of attachment disks and byssal threads that determine the strength of mussel ...
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... Mytilus coruscus Gould 1861, commonly found along the coast of East Asia, is distinguished by its robust, ribbed shell, which is predominantly black but can sometimes vary to shades of brown (Vekhova, 2019). This characteristic has earned it the nickname "hard-shell mussel" or "thick-shell mussel". ...
The hard-shell mussels Mytilus coruscus have been extensively employed in pollution biomonitoring. Earlier studies indicated that metal concentrations in Mytilus coruscus may not accurately reflect the true metal contamination levels in the sampling areas, possibly due to their modified metal uptake and efflux. Given the likelihood of mussels in the field being exposed to intermittent metal contaminants, this study investigated whether different Cu pre-exposures significantly affected its uptake and efflux upon Cu exposure. We found significant reduction in Cu uptake rate constant (ku) and efflux rate constant (ke) in the mussels with varying Cu pre-exposure regimes. Specifically, the ku decreased from 1.55 ± 0.37 L g−1 d−1 in the control group to 0.65 ± 0.19 after 5 days and 0.53 ± 0.28 after 15 days of exposure to 20 μg L−1 Cu, respectively, and then was further reduced to as low as 0.096 ± 0.046 L g−1 d−1 following a 5-day exposure at 50 μg L−1 Cu. Similarly, the ke decreased from 0.18 ± 0.020 to 0.15 ± 0.015 d−1 following 5 to 15 days of exposure to 20 μg L−1 Cu, and further decreased to 0.081 ± 0.023 d−1 after a 5-day exposure at 50 μg L−1 Cu. Our subcellular distribution analysis underscored the critical role of the metallothionein-like protein (MTLP) fraction in modifying both Cu ku and ke during the rapid-depuration phase (ke1), whereas the metal-rich granule (MRG) fraction influenced the ke during the second depuration phase (ke2). This study demonstrated that environmental assessments utilizing biomonitoring species should consider the exposure of these organisms to ensure accurate interpretations of metal contamination in marine ecosystems and enhance the effectiveness of these species in environmental monitoring. This crucial factor is often overlooked, potentially skewing data and leading to misinterpretations of environmental health and pollution levels.
... Under optimal temperature and salinity, the byssus secretion of thick-shell mussels is vigorous. This species has been shown to have the shortest and hardest byssus threads and the largest and strongest gum spots among sessile bivalves, indicating its adaptability to marine coastal zones with high hydrodynamic activity (Vekhova, 2019a(Vekhova, , 2019b). The mussels are a model species for marine environmental monitoring (Wang, 1959;Beliaeff et al., 1997;Qu et al., 2019). ...
Morphological features of the byssal groove of the foot have been studied in the common mytilid species Mytilus coruscus, Crenomytilus grayanus and Modiolus modiolus from the Sea of Japan. A comparative analysis has shown interspecies differences in the length, width, and depth of the byssal groove and in the
specificity of its structure, as well as in the size and shape of the distal fossa, where the byssal thread and the attachment disk are formed. The characteristics found in the morphological structure of the byssi in Myt. coruscus, C. grayanus, and Mod. modiolus are explained by the structural differences in their secretory organ.
In the commercial Pacific mussel species, Mytilus trossulus, from the Sea of Japan, features of the morphological structure of the byssal apparatus, byssal threads, and pedal groove are studied. Steps in the process of byssal threads formation and characters of the morphological structure of the byssal groove related to this process are described in M. trossulus. The byssal apparatus is shown to consist of a root, a stem, and byssal threads, the latter in cross section being ellipsoid in shape. A byssal thread consists of a corrugated proximal part located immediately behind the cuff and is one-third of its length, and a relatively smooth and flexible distal part taking up two-thirds of the thread length and ending with an attachment disk at the distal end. On the surface of the attachment disk, three reinforcing cords are situated. The morphological features observed in these structures are discussed in terms of the spatial distribution of mytilids in marine coastal zones, a successful habitat of M. trossulus being rocky shores with active wave activities.
