RELATIVE GROWTH OF SHELL AND MUSCLE AND POSITIONAL CHANGES OF MUSCLE SCARS DURING SHELL GROWTH OF GREEN MUSSEL, PERNA VIRIDIS L.

THYON CHENTANEZ, SONGSAK KUANPITAK,^a VILAI CHENTANEZ,^a SRITIEN USANAVARONG, and ORAPIN KOMONPHUNPORN

ABSTRACT: Relative growth of shell and muscle of the green mussel (Perna viridis L.), along with muscle scar displacement during growth, have been studied in detail. Parameters of 70 small and large mussel valves (2-10 cm) were measured and compared to obtain the following conclusions:
          1. The relative growth rate is faster in the antero-posterior direction than in the dorsoventral and lateral direction of a single mussel shell.
          2. Length/depth (L/T) and length/width (L/W) ratios of mussel shell gradually increase with increase in shell length.
          3. Maximum depth point (T_max) of the shell displaces laterally relatively fast in smaller mussel shells (2-4 cm) and displaces laterally relatively slowly in larger mussel shells (4.5-10 cm) at a constant angle of 30 degrees with respect to shell margin plane (Y-axis).
          4. There are exponential increases in mussel shell margin plane area, single shell weight and single shell volume with respect to increase in shell length.
          5. The specific gravity of smaller mussel shell (2-3 cm) is lower than that of larger shell (4.5-10 cm).
          6. There is a specific direction and mognitude of displacement for each muscle scar on the mussel shell. The posterior adductor (p) displaces posteriorly relatively faster than dorsally in all mussel shells studied. The dorsal retractor (d) displaces dorsally relatively faster than posteriorly in the smaller mussel (2-3 cm) and displaces posteriorly relatively faster than dorsally in the larger mussel (3.5-10 cm). The anterior rerractor (a) displaces dorsally relatively faster than posteriorly in all the mussel shells studied.
          7. The p displaces away from the umbo (u) at a relatively faster rate than the d and the d displaces away from the umbo at a relatively faster rate than the a.
          8. The distance from the umbo to each muscle scar and the pallial line tip and the distances between the muscle scars increases linearly proportional to the increase in mussel shell length.

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Departments of Physiology and^a Anatomy, Faculty of Science, Mahidol University, Bangkok, Thailand.

Received 5 November 1981

RELATIVE GROWTH OF SHELL AND MUSCLE AND POSITIONAL CHANGES OF MUSCLE SCARS DURING SHELL GROWTH OF GREEN MUSSEL, PERNA VIRIDIS L.

THYON CHENTANEZ, SONGSAK KUANPITAK,a VILAI CHENTANEZ,a SRITIEN USANAVARONG, and ORAPIN KOMONPHUNPORN

THYON CHENTANEZ, SONGSAK KUANPITAK,^a VILAI CHENTANEZ,^a SRITIEN USANAVARONG, and ORAPIN KOMONPHUNPORN