I am not a great fan of biology, especially when it comes to worms. However, in one good day when wandering across an intertidal zone near Loughshinny in Ireland I stumbled upon thousands of casts created by lugworms. This sight was really spectacular.
An overview of the beach near Loughshinny which is underwater in a high tide. All these little dots are lugworm casts.
Closeup of these casts. They are composed of beach sand which lugworms pushed through their body to extract nutrients from the sand. It seems to be a pretty painful way to eat.
The worms live in sand in a U-shaped burrow. You can see here both casts and holes. One end of the worm is beneath the hole, that’s the place where it takes in sand and another end is beneath the sand squiggle which resembles toothpaste pressed out of a tube.
I was even patient or lucky enough to see how one of these things came to be. I saw about a centimeter of sand suddenly pushed out of the beach sand. Hence, the formation process is most likely intermittent — about a centimeter at a time and takes some time during the low tide conditions. During high tide all these squiggles are wiped away by waves and worms have to take a rest and wait for the next low tide to eat again.
I preferred to leave the worms themselves alone. So, there will be no photos of the authors of these sand sculptures but they should resemble other common earthworms which are highly valued by fishermen who use them as a fish bait.