When giving tours of the shellfish hatchery, I find that scallops attract the greatest attention. Most people are thrilled to learn that scallops can swim but get even more excited when I show them the 40 or so glistening blue eyes positioned in the mantle tissue along the margin of the shell. Eyeless, less animated quahaugs and oysters are less likely to elicit this love-at-first-sight response. Granted, multiple stalked eyes staring out of a headless creature is pretty alien however the presence of any eyes seems to encourage engagement. Vision is an important human trait and it is not surprising that we find it easier to bond with life forms that share it and may be looking back at us.

Scientists too are fascinated by scallop vision. How, what and why do they see? Scallop eyes are unique. Unlike human eyes that function like a camera using a lens to focus an image on the retina, scallops are equipped with a complex system of mirrors not unlike a reflecting telescope. Incoming light is focused by the mirrors onto two different retinas providing both forward and peripheral images. Despite their sophisticated eyes, scallops lack a brain in the true sense only having more simple nerve clusters called ganglia and as such are limited in interpreting what they see. It is believed that scallops are capable of detecting shadows and some clearer imaging. They likely use their vision to avoid predators, and to locate suitable habitat and food within their immediate environment.

In one neat experiment, scallops were shown “movies” of food particles on a computer screen and were found to open their shells to feed when shown proper sized food particles moving at the right speed. Not bad for a brainless invertebrate.

Bay scallops are generally more delicate than their sightless, sessile bivalve cousins. Unlike quahaugs and oysters they cannot completely close their shells for long periods. Their shells are thinner and they are more likely to expose more of their soft tissues to the environment outside of protective shells. They do not burrow into the bay bottom like quahaugs nor live in protective reefs like oysters. They must find eelgrass beds and other protected habitats to survive. Unlike quahaugs and oysters, they have a short life span, rarely living past two years. The loss of a single year class can remove the spawning population and impact the populations for years to come. It is not surprising that bay scallop stocks have dramatically declined throughout their range. Reliable commercial scale populations are now limited to Martha’s Vineyard, Nantucket and Long Island.

At the hatchery we produce millions of scallops annually to assure that broodstock are maintained. We are vigilant in supporting good water quality. Please join us in our mission.

Scallops will be watching you.

Rick Karney is shellfish biologist and director emeritus for the Martha’s Vineyard Shellfish Group.