ScallopTV, Season 2

Unlike most bivalves (e.g. mussels, oysters, and clams), scallops have eyes. Indeed, most species have dozens to hundreds of them. These eyes are arrayed along the thin strips of mantle tissue that ring the edges of both valves. In the bay scallop Argopecten irradians, the eyes are a brilliant shade of blue.

It's known that scallop use their eyes to detect approaching predators. There is also evidence that scallops use their eyes to select preferred habitats, such as dark crevices for some species and grass beds for others. A few years ago – in a study we like to call ScallopTV – we found that bay scallops responded to dots moving across the screen of a computer monitor. As long as these particles were not moving too quickly, scallops responded to their presence by spending more time with their valves open than they did when no virtual particles were present. Because scallops feed by opening their valves and filtering small organic particles from the water column with their gills, we think that scallops may be using their eyes to monitor feeding conditions.

As a follow up to ScallopTV, I’d like to see if scallops use their eyes to assess the direction of flow. The direction of flow might matter to scallops because they prefer to filter-feed with their anterior (inhalant) opening turned to face oncoming flow. One way to test this would be to ask if scallops orient themselves in accordance with the direction of moving, virtual particles. My prediction is that scallops will turn so that their inhalant opening faces the on-coming virtual particles. Such an observation would strongly suggest that scallops are using visual cues to help guide their feeding behavior.

As a second experiment, I would like to see how the size of passing objects influences behavior in scallops. It is clear that large moving objects cause scallops to close their valves as a defensive response. What are the differences (e.g. size, speed, etc) between virtual objects that cause scallops to either close or open their valves? How scallops determine the size of objects may tell us something about how they process visual input. This would be a big step forward because we know a fair amount about how the eyes of scallops work, but we know very little about their brains.

behavior biology eye invertebrates marine molllusk scallops vision

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