October 05, 2022

Alaska bivalve guide - feet and siphons

Keller, K., K. Brown, S. Atkinson, and R. Stone. 2017. Guide for identifying select bivalve species common to
southeast Alaska. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-341, 25 p.
Document available: http://www.afsc.noaa.gov/Publications/AFSC-TM/NOAA-TM-AFSC-341.pdf

Posted on October 05, 2022 12:16 AM by clauden clauden | 0 comments | Leave a comment

September 27, 2020

Useful resource for identifying siphons

Posted on September 27, 2020 05:05 PM by clauden clauden | 0 comments | Leave a comment

May 31, 2020

Photo Credits

Thanks to @cspirrone and @zahnerphoto for letting us use their photos for our icon and banner photos, respectively!

Our icon photo is a wrinkled rock borer (Hiatella arctica). This is a cosmopolitan species that may have been spread through anthropogenic means. It lives in crevices of rock, kelp, and other substrates from the intertidal zone to depths exceeding 1000 m. It is easily identified by its scarlet-tipped siphons. A recent genetic study suggested that this "species" is actually a species complex of at least 13 different species!

Our banner photo is a small giant clam (Tridacna maxima). It is an inhabitant of the Indo-Pacific region, living in coral reefs and sand. The mantle is often brilliantly colored and houses symbiotic algae called zooxanthellae. These algae produce much of the energy the clam needs. This species is popular in the aquarium trade due to its smaller size and bright colors.

Posted on May 31, 2020 08:42 PM by thomaseverest thomaseverest | 0 comments | Leave a comment

May 29, 2020

How to Find and Photograph Live Bivalves

Historically, bivalves have almost exclusively been identified by their shells. Preserving soft parts is much more difficult than keeping shells and soft parts are not present in the fossil record. Furthermore, species identification is frequently impossible without a view of the inside of the shell, which is only possible with dead individuals. Today, however, photography of bivalves in situ is getting much easier and much more common. When shells and soft parts are correlated, we may discover ways to identify species in their natural habitats. Yet, many species cannot be identified in situ from their shells because of their burrowing habits, making them hard to extract or catch. Frequently, these species cannot burrow back into their substrates as adults, in which case they can only be identified by their siphons and other visible organs without killing them in the process. Here are some different habitats where you can find bivalves and what to do if you find them. For all bivalve shells, it's helpful to get photos of them lying flat with an indication of scale. One easy way to do this is by holding it in your hand and taking a photo from directly above. Get several photos from different angles, especially of the inside of the shell if the animal is dead. To see siphons and other soft parts, bivalves usually need to be underwater.

Sandy Beaches

Species here are burrowers, and some are very quick! Species like bean clams can be found in the sand or waves, especially during a low tide. Many bivalve species leave holes visible on the surface of the sand and can be dug up. This should only be done with the proper permits and where it is allowed; some species are protected and some cannot burrow back into the sand once they are removed. That being said, we'd love to get observations from clammers! When found alive, place bivalves in some water and let them sit still for a minute or two. Bring a bucket to keep them in temporarily. Glass works well, but it's often not advisable (or permitted) to bring glass to most beaches. Pretty soon after submerging them, you'll see their siphons. If you add some sand, they might stick out their foot and begin burrowing.

Tidepools and Reefs

Tidepools and rocky reefs are common along rocky coasts. Coral reefs provide similar habitats in the tropics. Boring clams can be found in hard substrates, and nestlers can be found living in their empty burrows. Some species can be found cemented to a substrate or attached with a byssus. Others can be found nestling in piles of rubble or pockets of sand. Still others can be found attached to the underside of large rocks or coral slabs. Given the rough surf common in these habitats, it is often difficult to get photos of bivalves underwater. Pools are a great place to look. Individuals out of the water that are not attached to a substrate can be placed in a bucket or pool of water. Many species that are attached with a byssus can reform one if they are dislodged, so it is possible to gently remove some species and place them underwater. However, reforming a byssus takes time and dislodging is often fatal because of rough surf, so this is generally not advisable. Burrowing and nestling species cannot survive outside their burrows and they cannot make new ones, so their burrows should be left intact. Fortunately, the careful observer can sometimes find protruding siphons even from individuals that are not submerged. Smaller species can be found by sifting sand and gravel. Many species found in tidepools are also biofoulers and can be found on pier pilings, harbors, and boats.

Beached Bivalves

Sometimes, live or fresh dead bivalves wash ashore. This can happen after storms when any number of substrates wash ashore. These instances provide a great opportunity to learn about more inaccessible species. If the animals are still alive, they will probably not survive even if they are returned to the ocean, unless they are shallow water burrowers. Boring clams can be carefully extracted from their substrate with a chisel and kelp holdfasts can be torn apart looking for a variety of nestlers. Shipworms can be found by splitting open driftwood. Animals should be placed in water for photographing and possibly donated to a museum for preservation (feel free to message me if you're interested in details on how to collect specimens). Fresh dead bivalves are those that are alive but still have remains of the animal attached to the shell. These can be helpful if parts of the animal are still identifiable. It helps to put them in water, and after getting some photos of the animal, you can clean the shell and get some photos of the inside of the shell.

Subtidal Habitats

Lots of species live completely underwater and can only be found by SCUBA diving. Subtidal habitats are similar to those on the shore, with soft and hard substrates. Bivalves here often have their siphons out. Smaller species can be found by sifting sand and gravel. Other bivalves live far beyond the reach of divers and are only accessible by submersibles and ROVs. If you find any deep-water bivalves, we'd love to hear about it!

Freshwater Habitats

Freshwater clams and mussels are widespread around the world. Some are highly invasive; many are at risk of extirpation because of habitat loss and pollution. Most species live in the sediment on the bottom of streams, lakes, and rivers. These can be found by sifting the sediment or by watching closely for siphons. Hunting for many species is highly regulated, even if you are just interested in taking pictures, so make sure you are aware of what is and isn't allowed. Some freshwater mussels, such as the invasive zebra and quagga mussels, attach to a substrate with a byssus and have become notorious biofoulers.

What Isn't a Bivalve

Some animals can look like bivalves, especially their siphons. Note that bivalves always have 2 siphons, so anything that appears to have more or less than that probably isn't a bivalve. Tunicates also have 2 siphons, but they are typically translucent while bivalves have opaque siphons. If the siphons are submerged, look for frills on the tips of one or both of the siphons, which is characteristic of bivalves. Brachiopods are marine animals with 2 shells like bivalves, but they are actually in their own phylum. Anatomically they have a top and a bottom shell, whereas bivalves have a left and a right shell. Some crustaceans also have 2 shells, such as ostracods and water fleas. These can be confused with a small bivalve, especially pea clams in freshwater environments, but they are usually very round and smooth. If you put them in water, you can see them scurry around with their appendages. And don't be fooled by the classic pistachio shell! More than one naturalist (including myself) has picked up a nutshell, only to realize it was left over from somebody's lunch.


Biofouler: an organism that lives on or in artificial structures, frequently impeding efficiency of movement and/or undermining structural support.
Boring clam: a type of burrower that lives in a hard substrate, such as rock, concrete, or other shells.
Burrower: a type of bivalve that makes burrows in a soft or hard substrate. If it is a hard substrate, it is called a boring clam and nestlers often live in these burrows after the original burrower dies.
Byssus: a mass of byssal threads that certain bivalves, such as mussels, use to anchor themselves to hard substrates. It is made of protein and is well-studied as a potential for biomimicry. In cooking, this is called a beard.
Foot: a wedge shaped organ that bivalves use to dig in soft substrates or attach themselves to hard substrates with a byssus. Some species can even climb.
Mantle: an organ in mollusks that encloses the internal organs. It deposits the shell and is often seen on the edge of the shell. Siphons are actually just folds of the mantle, but those are kept as distinct observation fields because of their frequent differences in appearance.
Nestler: a type of bivalve that lives in cracks and holes in a substrate, but does not make the hole itself. They often can be found living in empty burrows of boring clams. Shells of these species are often distorted from irregular habitats and other nestlers.
Siphons: paired tubes of the mantle coming out of the posterior end of the shell. One siphon takes in water, and the other squirts it back out. This is how many bivalves generate a current to get oxygen and food.
Substrate: a material that provides a surface on or in which an animal can live. Examples include sand, mud, rock, coral, seaweed, wood, shells, other animals, concrete, and trash.

Posted on May 29, 2020 10:19 PM by thomaseverest thomaseverest | 0 comments | Leave a comment