Eyes Under Puget Sound's Critter of the Month
Mmmm….scallops. It’s amazing how just one word can conjure up the taste and smell of pan-seared, buttery deliciousness. If you’ve ever been to a fancy seafood restaurant or watched the show, “Top Chef,” you know the important role that scallops play in the culinary world. But do you know what role they play in the sediment ecosystem at the bottom of Puget Sound?
Pretty in pinkThe spiny pink scallop spends its days doing what most scallops do: lying on its right side on the sea floor with its fan-shaped shell open, filtering from the water that passes over its gills. This particular scallop is known for its bright color and the prominent spines that adorn the ribs running down its shell.
What’s interesting about this species is that the type of sea floor it lives on can influence what it looks like! Individuals found on rocky or shelly bottoms (the more typical habitat) generally have the pink and spiny characteristics. However, individuals found on the muddy sea floor in more protected areas are drab in color, with less pronounced spines. The difference can be so drastic that taxonomists once thought these two “morphotypes” were actually different species.
|The spiny pink scallop on the right has the sponge (Myxilla|
incrustans) covering; the one on the left doesn't. Photo
courtesy of Dave Cowles, wallawalla.edu.
Imagine you are a sea star, sensing a tasty scallop lunch nearby. You reach out and touch… a slimy, unappealing sponge! It’s no surprise that sea stars have been observed rejecting the sponge-covered scallops. This benefit makes carrying the extra weight of the sponge worthwhile, even if the burden may impact the scallop’s growth rate.
Just keep swimmingSpiny pink scallops also have to worry about predation by sea otters, octopuses, and humans — creatures not so easily fooled by the sponge disguise. This is where its “swimming” ability, used by many mobile scallop species, comes into play. When the scallop senses a predator approaching, it can quickly clap the two valves of its shell together, squeezing water out and causing a jet propulsion effect that allows it to swim to safety.
How does the scallop know when danger is near? It can detect predators by smell using chemoreceptors in the margins of the fleshy body wall membrane known as the mantle.
|At 1 cm across, this little spiny pink scallop is already big enough to|
fall into the "hundreds of eyes" category! I stood it up on its side in
a petri dish to get a better look at them as the valves slowly opened.
The eyes have itIf you look closely at the mantle, you will see the scallop has another sense as well — sight. Those bright blue-green dots scattered around the mantle are actually tiny, adorable eyes! These eyes can’t see images, but they can detect changes in light that might mean a predator approaching. A baby scallop might have just a few, but an older individual can have hundreds.
Coming to a plate near you?
|This spiny pink scallop rests on the sea|
floor, valves fully open in feeding mode.
Photo by Jim Nestler, July 2005 (from
By: Dany Burgess, Environmental Assessment Program
Critter of the Month
Dany is a benthic taxonomist: a scientist who identifies and counts the benthic (sediment-dwelling) organisms in our samples as part of our Marine Sediment Monitoring Program. We track the numbers and types of species we see in order to understand the health of Puget Sound and detect changes over time.
Dany shares her discoveries by bringing us a Benthic Critter of the Month. These posts will give you a peek into the life of Puget Sound’s least-known inhabitants. We’ll share details on identification, habitat, life history, and the role each critter plays in the sediment community. Can't get enough benthos? See photos from our Eyes Under Puget Sound collection on Flickr.