We live in a bustling metropolis. Every morning, commuters wait at BART stations, bus stops, and traffic lights launching towards a new work day. Radios blast, televisions blare, children laugh, and parents rush. Amidst our many distractions and abundant responsibilities, we may forget to stop and appreciate the hidden habitats that exist along our shorelines. Not far from shore, in the intertidal zones of the bay, lives a peculiar, prehistoric-looking creature: the chiton.
Chitons are marine mollusks whose origins have been traced back 500 million years. They are related to more familiar watershed inhabitants such as clams, mussels and oysters. There are thousands of species of chiton, all of which are oval-shaped with 8 overlapping valves (or shells) that can range in color from brick red to muted gray.
These amazing marine mollusks use their foot to attach to the top or the underside of rocks that are situated between the low and high tide lines. This zone is certainly a tiring habitat to survive in for these small animals, often averaging only three to 12 cm in length. Their foot also enables them to move slowly along the tops of rocks in search of food at night.
Some chitons have demonstrated “homing” tendencies. When they leave their habitat to go look for food, they are able to return back to the exact same spot. While many chitons only eat vegetation such as algae, there are some carnivorous chitons that also eat small crustaceans. Since chitons often eat large amounts of algae, they play an important role in regulating algae growth in intertidal zones.
But that’s not the only impressive feat chitons perform on a daily basis! The chiton can roll up into a small ball, like a roly-poly, to fend off predators. Many chitons do not have eyes and must rely on nerve endings to help them detect predators. However, some chitons have evolved to grow eyes that allow them to see fuzzy outlines of approaching predators. These eyes are especially unusual because they are made of aragonite– the same material that comprise chitons’ shells. Aragonite is actually a type of rock forming mineral, meaning that some chitons literally have eyes made of stone! This hard material is helpful for protecting the chitons’ eyes because they are regularly exposed to rough waves and rocky waters.
This ancient marine mollusk, with its unique an interesting attributes, is an example of one of the important forms of life that we might find but not regularly notice in our watershed. If you get a change to explore the local shoreline, like students do in our Living Shoreline program, it may be possible for you too, to spot a chiton!