The dozens of eyes of scallops are quite intricate. They have a lens up top like ours, but that doesn't do most of the focusing. Instead the light passes through to a mirrored retina, covered with a field of guanine crystals (yes, that guanine, the G in the ATCG bases of DNA!). The reflective layer is used to focus the light back towards the second retina where the rod cells are. In this way, the eyes of scallops work more like our mirror telescopes than the eyes of most other creatures. Using these eyes, scallops can resolve images in surprising detail, allowing them to discern the shape of predators, navigate while swimming, and even figure out the good places to seek food (they tend to reach out to smell/feel objects based on what they are seeing!) #clamFacts

Fingernail clams (Sphaeriidae), aka pea clams, are seriously underrated bivalves. They live in freshwater, being transported upstream and to new lakes by clamping onto birds, the feet of salamanders, or even in the digestive tract of fish. Some species even live in vernal pools: seasonally dry, isolated puddles. How does an aquatic water-breathing bivalve manage to survive when their pools dry up? Turns out they can use their muscular foot to dig down into the dirt, up to 8 inches, to stay under the water table, where they wait for months for the rains to return and refill the pool! Life finds a way! https://www.oriannesociety.org/faces-of-the-forest/woodland-clams-are-a-thing/?v=f69b47f43ce4
#clamFacts

Many bivalve species exhibit sequential hermaphroditism, meaning they start as one sex and transition to another during life. This is advantageous because many can't move, so if they change during their lifetime, they can have twice as many mates! Most species showing sequential hermaphroditism are protandric (starting as males, and transitioning to be female or both as they grow in body size), but some less common examples of protogyny (starting as females) have been reported! #clamFacts

Bivalves are generally most mobile in their larval stage, when planktonic larvae can be spread to new regions by currents, then settling down to a sessile adult life. The Southern Ocean bivalve Gaimardia trapesina is one of the exceptions: adults attach to strands of floating kelp, where they may float thousands of kilometers, riding the Antarctic Circumpolar Current! This was one group observed by iNaturalist user boldenowml in the Falkland Islands. https://www.inaturalist.org/observations/39296276 #clamFacts

Western snowy plovers are threatened shorebirds along the US Pacific Coast. One way we can help the plovers is by spreading oyster shell! Researchers have figured out the plovers prefer to nest on oyster shell. The white, reflective shells help thermoregulate the eggs, and also provide cover and camouflage for the chicks (which are adorable and vulnerable to predation). Restaurants often donate used shells to restoration groups working in SF Bay!
https://journal.wildlife.ca.gov/2024/11/04/the-importance-of-oyster-shells-in-the-breeding-success-of-western-snowy-plover/
#clamFacts

I'm not a beer expert. But I have had oyster stouts, and they can be tasty! Techniques behind oyster stouts vary but often involve adding crushed oyster shell as a filter bed to clarify the beer, or even whole oysters in the kettle, where tissue and fluid in the shell (called liquor, or extrapallial fluid if you really want to impress your barmates) add even more ocean flavor. This adds a briny, marine tinge to the toasty flavor of the dark beer. https://newschoolbeer.com/home/2022/3/oyster-stouts-schucking #clamFacts

Many bivalves are what we call "ecosystem engineers": they make habitat for everyone! Mussels attach to rocks in the intense surf zone, helping break up wave energy to make it habitable for other life. Oysters do the same by trapping sediment between their shells to make huge piles called reefs. Other clams dig into the substrate, oxygenating the sediment and freeing nutrients to generate more plankton growth! Clams are the change they want to see in the world! #clamFacts

The ocean quahog has been confirmed from shell growth lines to live 507 years, making it the longest-lived non-colonial animal! But other bivalve species also can outlive us, like the European bittersweet at 192 years and the Pacific geoduck at 168 years. Most long-lived bivalves (with some exceptions) are found at high latitudes, where metabolism is slower due to lower temperatures, and living longer gives them more chances to pass on their genes in an extreme environment! #clamFacts

The shells of snails and clams look quite different, but every clam shell actually contains a hidden spiral, hinting at their shared ancestry. In a classic series of papers in the 1960s, David Raup figured out that all mollusk shell shapes are governed by a logarithmic spiral model. Varying four parameters, a vast variety of shapes can be made. Others built on the model since, but the Raup model was an important advance in reverse engineering the brilliance of the mollusk shell. #clamFacts

@emmadavidson I recommend following the #ClamFacts hashtag

Spanish aquaculturists in Galicia have reported a crash in stocks of several types of bivalve in the area. The die-off in mussels, cockles and other economically important species in the area is thought to be due a crash in salinity in the estuary after record-setting rains. Such intense precipitation events are expected to grow in frequency and intensity in many Mediterranean climate regions as the atmosphere warms. #clamFacts

https://www.theguardian.com/world/2025/jan/28/spanish-fishers-in-galicia-report-catastrophic-collapse-in-shellfish-stocks