31/05/2026
π Week 22 of 2026 from the Broome Shells deck is...
Trochus shell in the Gastropod suit β¦
The Trochus or top-shell is cone shaped like a spinning top toy or witch's hat. I like to say that the mollusc animal (like a snail) grows the shell spiral on top of itself. It's a familiar form worldwide, and are also known in the Kimberley for being harvested (now farmed), then cut and polished by Bardi Jawi people at Ardyaloon (One Arm Point) Hatchery, up the Dampier Peninsula, about 220km North of Broome. They grow to as big as your hand and quite heavy because the shell is thick, containing layers of nacre (mother-of-pearl) which was used for making buttons (recently) and Indigenous tools and adornments for thousands of years. Trochus are herbivores, living on the seabed or coral reef, eating algae (eg. seaweed) and plants such as seagrass. The base of the shell is nearly flat. When alive the mollusc has an operculum attached to its foot, the part that helps the snail move around, which can retract into the shell to protect itself. In the photo you can see the colour changes as the shell gets bigger. It started life as a teeny tiny shell, just the top tip of this shell which is almost transparent. The animal achieves reproductive maturity around 2 years old and can live for more than 10 years, they have internal growth rings that can be seen when cut open. Reproduction happens via 'nocturnal broadcast spawning' and external fertilisation. As the animal grows, it adds calcium carbonate from its environment to the edge of its shell in a right-handed, clockwise / dextral direction. Growing around, bigger, heavier and older.
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