Nerite snails are common on the rocky shore. On warm days, they are usually gathered in a shady nook, sometimes in large groups. On a cool morning or evening, you might see them creeping about.
Tough Nerite to Crack: The Nerite has a thick shell. A sturdy chalky operculum provides a secure seal. The operculum has an internal peg to lock firmly in place against the teeth at the shell opening. This makes it difficult for a crab to stick a pincer in and dig out the snail. It also protects against water loss during low tide.
Nerites usually stay above the high tide line. This is probably to avoid being eaten by crabs and fish. The Common Nerite (Nerita lineata) appear to return to the same spot after a feeding bout.
Some colourful Nerites are hard to spot as they blend well with the rocks they are found on.
Nerite food: Nerites graze the algae that thrive on the rocks, scraping this off with their radula. They also eat lichen growing there.
Nerite babies: Nerites have separate genders and engage in internal fertilisation. So they actually have to make body contact to reproduce. Sometimes you can see mating nerites, especially early in the morning, near wet spots on a rock. They have a complex reproductive system to achieve this, and to produce nutrition-packed eggs in protective capsules. The white circular egg capsules are sometimes seen in rock pools, under rocks and in moist crevices. Each egg capsule may have more than 30 eggs. These hatch into free-swimming larvae that only later settle down to develop into snails.
Here is a recent WildSingapore blogpost on some Singapore nerites
The colours and variety are simply amazing!
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