Final answer:
In gastropods like snails and slugs, the control of shell coiling is separate from the developmental process of torsion. Torsion involves the rotation of internal organs, while the coiling of the shell, made from calcium carbonate, may occur in either direction independently.
Step-by-step explanation:
Control of Shell Coiling in Gastropoda
Gastropods, commonly known as snails and slugs, have a distinctive development process called torsion. This process involves the rotation of the visceral mass and mantle around an axis over the center of their foot during embryonic development. The resulting effect of torsion is a noticeable asymmetry in the adult gastropod where anatomical features such as the anus are brought forward above the head. Coiling of the shell, however, is not the same as torsion. The shell, primarily made of calcium carbonate, may coil independently in either direction and is not directly caused by the torsion of the visceral mass.
Gastropods have complex anatomical adaptations including a modified foot for crawling, a well-defined head with tentacles and eyes, and a mantle cavity that may house ctenidia or act as a lung in terrestrial species. More than half of all molluscan species are gastropods, thriving in varied environments from oceans and freshwater to land habitats. Their adaptive success is partly due to their asymmetrical bodies and in many cases, a coiled or spiraled shell, which could be planospiral or conispiral in configuration.