What do clams eat? 5 Foods They Eat

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Clams are bivalve molluscs that typically thrive in both freshwater and saltwater environments. Although they resemble other molluscs such as oysters and mussels, clams have some unique characteristics that make them worth studying. For example, the way they move "on their feet" and their method of eating are just two interesting aspects of clams. Looking at these creatures, it's hard to imagine them eating, so let's answer the question, what do clams eat?

Discover what foods they like, how they handle a meal, and what creatures want to eat them too!

What food do clams eat?

what clams eat
Clams eat plankton, algae, and other organic matter.

© AZ-Animals.com

Clams eat algae, zooplankton, phytoplankton, and other organic matter that passes through their filtration systems. These molluscs are omnivores, eating both plants and animals, albeit the smallest ones. These bivalves don't have huge appetites, but they will eat all of the following:

  • algae
  • by-products of symbiotic algae
  • Zooplankton
  • Phytoplankton
  • Organic Matter Flowing in Aquatic Habitats

While this wide variety of foods may give the impression that clams don't eat many foods, the truth is that clams have a diverse diet. As filter feeders, clams will eat whatever is produced through the siphon with nutritional value.

This could be organic matter from decaying plants or even the excrement of aquatic organisms. In this sense, clam diets can be very diverse under the umbrella of these five foods.

How do clams eat?

Animals without brains - clams
Clams obtain their food through filter feeding, also forming a symbiotic relationship.

©maya_parf/Shutterstock.com

Clams use very interesting methods to obtain and eat their food. For one thing, the clam can move a little bit with the help of its "feet". They use this conical muscle to better position themselves in the water for nutrition. They don't tether themselves to the substrate like oysters do; they'll find an area where food is plentiful and dig enough holes to stay in place while they feed.

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Clams obtain food by filtering water through intake siphons and expiratory siphons in their bodies. Food that passes through the gills becomes trapped in a thick mucus that moves by ciliary action to the lip and then into the clam's mouth. This is how plankton, algae and organic matter are consumed.

Clams have another way of getting their nutrients. Certain species of clams form a symbiotic relationship with algae, such as zooxanthellae. These algae live in the clam's mantle. The mollusks absorb and provide the algae with the nitrogen it needs to thrive, and the algae provide the clams with various nutrients.

All told, clams can process about 24 gallons of water per day in search of food.

What do clams eat in winter?

dig clams
Clams bury themselves dormant over winter, but are ready to be harvested at this time.

©knelson20/Shutterstock.com

The clam's "feet" help the creature move around to a more habitable location, or find safety by burrowing into the sand. Typically, they only dig deep enough in the sand or mud to protect themselves from predators, but not so deep that their siphons can't bring in nutrient-rich water.

During the winter, the clam uses this muscle to dig an ultra-deep hole for itself. This burrow is slightly deeper than their siphon length, effectively burying them during the winter months. Clams go dormant for the season when temperatures drop below freezing.

In other words, clams eat very little, if any, during the winter because they are too busy trying to survive the cold that comes with the season.

How does a clam diet affect other people?

A giant giant clam (Tridacna gigas) grows on the sea floor of the Republic of Palau
Large clams help remove excess nutrients from waterways and improve the environment.

How a clam filters and feeds has a major impact on the waters it inhabits. Specifically, they can help prevent eutrophication, the process in which excess nutrients in water bodies lead to suffocating algal blooms, increased phytoplankton populations and low oxygen levels.

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Eutrophication can lead to massive fish kills and cascade damage to ecosystems. Fortunately, clams and other molluscs, such as oysters, help remove a lot of excess nutrients through filter feeding. From this perspective, the symbiotic relationship between the clam and the zooxanthellae is even more beneficial, removing nitrogen from the environment while also creating food for itself.

A single large clam can filter as much as 24 gallons of water per day, so areas with thousands of clams can remove a considerable amount of nitrogen and phosphorus from water bodies over the course of the year. This results in cleaner waterways and thriving ecosystems.

All in all, the food eaten by clams has a significant and measurable impact on the environment, and this impact may be used purposefully to restore waterways in the future.

What predator eats clams?

Largest Eel - California Moray
Eels can crack open the shells of clams and eat the molluscs inside.

©SunflowerMomma/Shutterstock.com

Clams are invertebrates with soft bodies encased in a hard shell. Unfortunately for them, their shells and ability to bury themselves in sand and mud are the only means of protection available to them. These creatures are easy prey, and many animals around the world take advantage of the clam's helplessness.

Although they have a rudimentary foot protrusion, even when they are buried, it is not enough to help them escape from predators.

The most common clam predators include:

  • Humanity
  • oyster drill
  • black oystercatcher
  • Crab
  • eel
  • Angelfish
  • octopus
  • squid
  • Puffer fish
  • black skimmer

Each of these creatures can pry open the shell or otherwise gain access to the clam's soft body. Humans are the most dangerous to clams because they often catch and eat them as part of their diet, or kill them and keep their shells for garnish.

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In a way, clams are kind of unlucky because they can't fight back against predators or spot them in time to close their shells often. Their environment does help to a certain extent, though. Fortunately, the most common clams are not threatened.

Clams may not be exciting creatures at first glance, but they have many interesting aspects. Their contribution to the environment, symbiotic relationship with algae, and the presence of their "feet" all make clams worth looking at and curious about. A clam's diet isn't particularly exciting, but it's varied and helps keep waterways clean.

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clam filter feed
Clams filter water for food

© Greg Amptman/Shutterstock.com


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I'm a freelance writer with 8 years of experience. I've written in various fields such as Managed Service Providers, Animals and Retail Distribution. I graduated from Rowan University in 2014. When I'm not working, I enjoy playing video games, reading and writing.

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