Darwinellidae
Darwinellidae is a family of marine bivalve molluscs in the order Veneroida. They are commonly known as “cockle clams“. These are small, mostly infaunal bivalves with a generally oval or rounded shell. They are typically found in soft substrates, such as sand and mud, and can range in size from a few millimeters to several centimeters. The family is named after Charles Darwin, who collected many of the species in the family during his voyages.
Characteristics
Darwinellidae possess several distinctive characteristics that set them apart from other bivalves. Most notably, these clams have a distinct "umbo" (the oldest part of the shell, where the two valves meet) that is prominent and located near the anterior end of the shell. They also have a characteristic "pallial sinus" (a groove in the shell's interior) which is typically deep and rounded.
Their shells are generally thin and fragile, with a smooth or slightly textured surface. They can range in color from white to brown, and are often covered with periostracum (a thin, outer layer of organic material). Darwinellidae have well-developed, siphons that are used to filter food from the water and breathe. They also have a foot that is used for burrowing into the sediment.
Environments
Darwinellidae are found in a wide range of marine habitats, including shallow water, intertidal zones, and deep-sea environments. They are often abundant in areas with high sedimentation rates. They prefer soft substrates such as sand, mud, and silt. Darwinellidae are an important food source for various marine animals, including fish, crabs, and seabirds. They are also considered to be a valuable component of the marine ecosystem, playing a role in nutrient cycling and sediment stabilization.
Classification
The family Darwinellidae includes a number of genera, with a high degree of diversity in terms of species. Here are some of the most commonly known genera:
- Darwinella
- Tellinella
- Lioconcha
- Eurytellina
- Macoma
The classification of Darwinellidae has undergone revisions over time, with new species and genera being discovered and reclassified.
References
For further information and detailed taxonomic data, consult the following references: