Scallops, also known as מסרקיים in Hebrew, are part of the ocean’s exquisite organisms. They are bivalve mollusks of the family Pectinidae, with beautiful, fan-shaped shells. They are far more interesting than your typical shelled animal. They have sophisticated propulsion systems as well as sensory systems. Their unique biology has fascinated researchers for years.
The Biology of Scallops: Eyes and Swimming Shells
Scallops are unique. Approximately fifty to two hundred of their eyes are located on the outer edge of the mantle. The mantle constitutes the soft body of the mollusk located inside the two shells. The eyes are a brilliant blue and function with a mirror-based optic system. The system is designed like a powerful telescope. Each eye has miniature mirrors composed of guanine, and the mirrors are structured like a true mirror and not a reflective surface. When light enters through the eye’s pupil, it passes through a lens, reflective mirror, and two retina. The mirror causes the light to reflect and not to the surface of the mirror but beyond. Scallops have an interesting system to see and recognize light and moving objects, and consequently, evading potential predators.
Scallop eyes are able to do a lot more than just form an image around them. They are able to respond to changes in light by dilating or contracting. This process, which takes several minutes to do, is much slower than a human’s eye response. However, scientists are still learning how scallops see the world around them despite the process being so slow.
Jet propulsion is an uncommon form of movement for bivalves, and scallops are the first bivalves to be able to do so. Using rapid movements from their adductor muscle, scallops can expel water from their shell and move through the water. This millisecond-long clap consists of three main phases: region of closing, region of gliding, and region of opening. When at maximum velocity, the clap can reach an angular velocity of 182 degrees per second. This entire process is incredibly energy efficient and allows scallops to move through the water freely.
Habitat and Nature: Dwellers of the Seafloor
Scallops can be found in most of the world’s coastal and offshore waters, and are usually found on sandy or gravel seafloors. They are filter feeders, and help ecosystem by pulling seawater, and removing the phytoplankton, other organic particles, and detritus. This feeding behavior contributes to the upkeep of water quality and facilitates the movement of nutrients, in a process called benthic-pelagic coupling.
The inner layer of a scallops shell is called the mantle, and it has many parts, one of which is the eyes, and then there are the gills, and then there is part of the water jet propulsion mechanism. This combination of senses and movement makes scallops more mobile than many other bivalves. This helps escape predators like starfish and crabs.
Scallops Through Time and Culture
For centuries, scallop shells have had symbolic significance for a variety of cultures. Probably most famously, they symbolized the Camino de Santiago, the ancient pilgrimage route to Santiago de Compostela in Spain. Scallop shells, or Vieira as the Galician and Spanish term suggests, were collected by medieval pilgrims as a souvenir of the journey. There is a legend where a knight was saved by Saint James, and to signify the knight’s defiance of a sea crossing, he was covered in scallop shells. The pilgrimage then became a spiritual journey to the Knights of Saint James. The many lines on the shell represent the many different routes taken to Santiago, and the unity and purpose along the way.
Scallops are also used in other forms of cultural expression such as literature and art. Scallops remain some of the most sought-after shellfish in the world due to their mild sweet taste and tenderness. The adductor muscle or “eye” is the part of the scallop that is most commonly eaten, although some cultures also enjoy the gonads (roe) and other parts.
Sustainability and Conservation
Sustainable harvesting has become a growing concern for harvested scallops. Environmental impacts differ among fishing practices. A scraping dredge can wreak havoc on marine habitats by dragging metal cages on the ocean floor. Eelgrass beds are especially affected as they are home to a diverse range of marine life. Seafood Watch at the Monterey Bay Aquarium classifies bay scallops harvested by dredge in Massachusetts as a “yellow” and “Good Alternative” option. Fisheries managers have undertaken restoration efforts to address the problem; however, this is insufficient as vertebrate historical levels still remain. There are other efforts to address the problem by collecting wild adult scallops, which they call “spat” and then raising them in hatcheries to reseed them. There are also efforts being made to regulate the impacts of dredging on eelgrass beds as well as on the overall ecosystem.
Diver scallops are a much better caught option as there is far less habitat degradation than with other fishing methods. Aquaculture is a sustainable option as well, as it alleviates the pressure on wild scallop populations. Consumers are also able to do their part by purchasing scallops from certified fisheries like the Marine Stewardship Council, or by checking the Seafood Watch to see recommend scallop fisheries.
A Marvel Worth Protecting
Scallops— מסרקיים — are more than just a delicious food item. Their elaborate eyes, the way they propel themselves through the water, and their important role in the ecosystem, all show these creatures are extremely well adapted to their environment. The scallop shell also illustrates the deep history of human interaction with nature, having emerged from ancient sea floors. As we keep harvesting and enjoying scallops, we can assist in their sustainable harvesting and ensure these amazing marine organisms will continue to flourish.
