The spiny pink scallop: Ready for sweater weather

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 pink

The 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 microscopic algae 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.

Sweater weather

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.

Spiny pink scallops that live on the hard, rocky sea floor also tend to be covered with a layer of yellow sponge on their upper (left) valve. This is a symbiotic relationship that benefits both parties — the sponge gets a comfy place to live, and the scallop uses its sponge “sweater” as protection from predators.

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 swimming

Spiny 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 it

If 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
wallawalla.edu).

The spiny pink scallop has somehow managed to avoid being a target of commercial fisheries (although some are harvested each year by diver or trawl in Canada). This is partially due to its small size; maxing out at about 6 cm, the spiny pink scallop barely makes a mouthful compared to the giant Pacific scallop or weathervane scallop (Patinopecten caurinus) found on Pacific Northwest dinner menus. However, its smaller (and less common) cousin Chlamys rubida, the Pacific pink scallop or smooth pink scallop, has made a comeback in Seattle restaurants in recent years. Perhaps the smooth pink scallop is prized over the spiny pink scallop for its delicate flavor? Someone needs to do a taste test — I’ll volunteer to be the judge!


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.