caption: The image shows a group of four different types of freshwater mussels on a black background. The mussels are arranged in a cluster, with each one having a unique shell shape and color. The shells are of varying sizes and shapes, with some having a smooth, glossy finish and others having a more rounded shape. The colors range from light brown to dark brown, and the shells have a glossy sheen. The background is a deep black, providing a stark contrast to the mussels and shells.