How are Sea Dollars Made?
Sea dollars, also known as sea biscuits, are fascinating marine invertebrates that belong to the class Echinoidea. These unique creatures are known for their flat, dollar-shaped shells, which are often adorned with intricate patterns and spines. But how are these captivating sea dollars made? Let’s delve into the fascinating process behind their creation.
The life cycle of a sea dollar begins with a larval stage, known as a bipinnaria. This larva is free-swimming and has a distinct, cup-shaped body with five rows of tube feet. During this stage, the bipinnaria feeds on plankton and searches for a suitable substrate to settle on. Once the larva finds a suitable spot, it undergoes a series of transformations to develop into an adult sea dollar.
The first step in the process is the formation of the shell, which is made up of calcium carbonate. As the larva attaches itself to the substrate, it starts secreting a layer of spicule-rich material called the endoskeleton. This endoskeleton is composed of tiny needle-like structures called ossicles, which are made of calcium carbonate. These ossicles provide the sea dollar with support and protection.
As the larva grows, it continues to secrete more ossicles, gradually forming the characteristic dollar-shaped shell. The shell is covered with a thin layer of soft tissue called the epidermis, which gives the sea dollar its unique color and texture. The epidermis is also responsible for the intricate patterns and spines that are so characteristic of sea dollars.
Once the shell is fully formed, the larva undergoes a metamorphosis, transforming into an adult sea dollar. During this process, the larval tube feet are reabsorbed, and new adult tube feet emerge. The adult sea dollar also develops a mouth and digestive system, allowing it to feed on a variety of marine organisms, such as plankton, algae, and small invertebrates.
The growth and development of a sea dollar are influenced by various factors, including water temperature, nutrient availability, and the presence of predators. As the sea dollar matures, it may reproduce by releasing eggs and sperm into the water, starting the cycle anew.
In conclusion, the process of making a sea dollar is a remarkable series of transformations that begin with a free-swimming larva and culminate in the formation of a unique, dollar-shaped shell. This fascinating marine invertebrate showcases the incredible complexity and adaptability of life in the ocean.
