Swirl is one complete coil of snail shell tube. Swirl is counted from the tip (vertex) of the shell after half a swirl to the mouth of the shell.
What is the function of the snail swirl?
Embryo Swirl — The first part of the snail shell, formed in the egg. Also called a nuclear swirl. Epifram — A film of dry mucus that forms over the opening of the snail's shell and helps prevent it from drying out when the snail is inactive for extended periods of time.
Why is there a swirl in the shell?
The main factor is how quickly the conical tube expands (or flares out) over time. If the expansion rate is low and each subsequent swirl is not much wider than the previous swirl, there are numerous swirls in the adult shell.
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