Weekly Sea Discovery: Bubble Snails

As we continue our eelgrass surveys in our local waters, I am always amazed at the diversity of exciting creatures we encounter. Last week, we mapped an area by Montague Harbour and came upon hundreds of egg deposits in the eelgrass bed (see photo). Though I couldn’t track down what was laying these eggs, our biologist Rob Underhill identified them as bubble snail eggs.

Bubble snail eggs found in eelgrass beds around Parker Island, British Columbia.

A bubble snail is a type of marine gastropod that is between a sea slug (nudibranch) and a snail. They have fragile, small shells that often do not cover the snail’s entire body. These marine snails use their large heads, called headshields, to burrow through the sand. They also secrete a layer of mucus surrounding their body so they can move smoothly through the grains.

Here you can see the two black eyespots on this blister glassy-bubble. Photo: Karolle Wall

There are a few types of bubble snails found in the Strait of Georgia: the blister glassy-bubble (or white bubble snail, Haminoea vesicula), the green bubble snail (Haminoea virescens) and the Japanese bubble snail (Haloa japonica). These tiny invertebrates (usually around 2 cm long) can be hard to spot and are challenging to differentiate from each other.  

The Japanese bubble snail (Haloa japonica) has a dark line running through the centre of its head. Photo: Robin Agarwal

Commonly found in mudflats and eelgrass beds, bubble snails move to shallow waters in July and August to lay their eggs. These productive snails can deposit multiple gelatinous ribbons filled with eggs during reproduction. Our local bubble snail species are herbivorous and feed on various types of green seaweeds.

A bister glassy-bubble deposits its eggs on a blade of eelgrass. Photo: Karolle Wall

The amount of life sustained by eelgrass beds is incredible and continues to show us the importance of monitoring and understanding these crucial ecosystems.


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