Most of us are probably familiar with the seafood dish, scallops. This is just the end point of a long journey that the bivalve species of the same name embarks on. The meat of the scallop – the part we eat – is actually just part of a whole mollusk that resembles any other bivalve species like a clam. With that in mind, it becomes a bit more plausible that a scallop can swim, though it’s still difficult for us to imagine.
They don’t have fins, so they can’t push the water around themselves, and they can’t walk around like crabs. So how do scallops and other similar bivalves get around?
Well, as you may have guessed there is another method of movement that many sea creatures use which is akin to jet propulsion. Bivalves – which is the fancy name for mollusks enclosed in an outer shell – suck in the water around them like a vacuum and then spit it out behind themselves to push them forward.
Some bivalves, like scallops, have advanced to the point where speed is no longer an issue. Others remain mostly sedentary and use their “feet” to push them short distances across the floor of the ocean. All of them use the same propulsion method, but species like scallops have simply evolved to do it better and faster. They are able to push themselves throughout the open water, much higher than most other types of bivalves.
The whole process is quite interesting and seems to be unique to mollusks of the sort. So interesting, that many in the scientific community are attempting to recreate it for practical uses. Teams of developers are working to implement this form of jet propulsion – which can reach staggering speeds if done right – into small robotic recreations of scallops and other bivalves with the hope of utilizing it for further endeavors.
How Eating Has Evolved to Movement
The process that enables most bivalves to move in this manner is similar to that of their eating methods. For centuries mollusks of the sort would utilize the vacuum they had created within their shells to suck in small prey that was within distance. This enabled them to eat while not having to move too much. This method was perfect for bivalves as it used their tools to aid in the eating process without having to do much movement.
The same can be said for their digging habits. Bivalves dig holes in the sand for a various number of reasons, the most common being shelter and safety. They might need to dig a hole in a matter of seconds with predators approaching, and so speed was of the essence. With the speed at which the opening and closing of their shells enabled them to move the sand and create a space in which they could hide, bivalves slowly advanced.
Some bivalves advanced their shell movements in a new fashion that would come to separate them from the pack. The scallop specifically discovered how this technique could assist them in movement and so evolution took hold of the process. After centuries, the scallops perfected this method of movement and are now some of the fastest bivalves in the ocean today. It all stemmed from the need for food and shelter.
A Scallop Faster than Most Bivalves
The reason why this method of movement has been attributed so heavily to the scallop is because of the speed at which they are able to accelerate. Other species of bivalves are able to essentially hop across the ocean floor with this technique, but very few can actually “swim” like the scallop can. Most mollusks live rather sedentary lives with plankton growing around their shell. The scallop, however, is able to react to its environment and run when necessary.
In terms of pure speed, the queen scallop takes the cake as she can reach up to 37 cm/second. On a human scale, that would equate to us running our body length five times in under a second which is impossible to do. So what makes them so fast? How can they reach such incredible speeds without fins or legs in the typical sense? The jet propulsion method of movement slowly builds on itself which only creates more speed as it is used.
This essentially means that once the scallop has been moving for a few seconds, the propulsion of their technique has built up the amount of speed they are able to reach. Eventually, a queen scallop – after a few pushes – will be going her top speeds. As long as she gets the jump on her opponents, no one will be able to catch the scallop. They can also switch directions in an instant creating an erratic, but effective method of escape.
Quite the Tiring Process
For the scallop, the opening and closing of their shells requires the use of muscle which, after a while, can get rather tiring. This method of movement is not automatic and is rather labor intensive which can lead to a quick burn out for many scallops. If you think about it, they’re opening and closing their shells – which are much bigger than their bodies – at a rate akin to that of a bird wing. That takes a lot of strength to do, let alone to do at the speed at which they are doing it.
It’s for this reason that scallops only use this method for short distance swimming. Even though they are the most active species of bivalve, they still are rather sedentary, not moving too far from their habitat at any point in their lives. They continue to utilize the vacuum method of eating and their hole digging techniques. However, when it comes down to a race to get away from a predator, the scallop will always beat out other mollusks.
It certainly is an interesting method of movement that is not found in many other species in the world. When the scallop wants to move, they can move quite fast. Through pure strength and maneuverability, the scallop has made this jet propulsion their own.