Donax
Donax is a genus of small, edible, saltwater clams, marine bivalve molluscs in the family Donacidae. They are commonly known as “coquina” or “wedge clams” and are found in sandy beaches worldwide, often forming dense populations. They are characterized by their distinctive wedge-shaped shells, which are typically white, tan, or brown in color with intricate markings and ridges.
Characteristics
Donax clams are small, typically measuring less than 2 inches in length. Their shells are thick and strong, with a prominent umbo (the highest point of the shell). The anterior (front) end of the shell is rounded, while the posterior (rear) end is more pointed. The exterior surface of the shell is often ornamented with concentric ridges or grooves, while the interior surface is smooth and pearly. The color of the shell can vary depending on the species and the environment, ranging from white to tan to brown, with some species exhibiting colorful patterns or markings.
Environment
Donax clams are found in intertidal and shallow subtidal zones, typically in sandy beaches with moderate wave action. They are burrowing bivalves, living just beneath the surface of the sand. Their shells provide protection from predators and the harsh environment. They are often found in large numbers, forming dense populations that can play an important role in the local ecosystem.
Diet and Behavior
Donax clams are filter feeders, using their siphons to draw in water and extract microscopic algae and other food particles. They are active during the day, extending their siphons to filter food from the surrounding water. During low tide, they burrow deeper into the sand to avoid desiccation.
Species
The genus Donax includes over 100 species, which are distributed worldwide. Some of the most common species include:
- Donax variabilis (Variable Coquina)
- Donax serra (Serra Coquina)
- Donax denticulatus (Toothed Coquina)
- Donax gouldii (Gould's Coquina)
- Donax vittatus (Striped Coquina)