Brissus gigas, commonly known as the giant heart urchin, is a species of sea urchin belonging to the family Brissidae. This distinctive species is characterized by its heart-shaped test (shell) and its unique adaptations for burrowing in sandy substrates.
Description & Characteristics
Brissus gigas is a medium-sized sea urchin, typically reaching a maximum size of around 15 centimeters in diameter. The test, or shell, of this species is heart-shaped, with a flattened ventral (bottom) surface and a more rounded dorsal (top) surface. The ambulacral areas, which are the radial channels running along the test, are clearly defined and are typically slightly raised. The test is covered in numerous spines, which are relatively short and blunt, and are used for locomotion and defense. Brissus gigas is a burrowing species, and its adaptations for burrowing are evident in the shape of its test, its spines, and its unique tube feet, which are modified for digging.
Habitat and Occurrence
Brissus gigas is a widespread species found in the tropical and subtropical waters of the Indo-Pacific region. This sea urchin is commonly found in shallow to moderate depths, typically inhabiting sandy or muddy substrates in the neritic zone. The neritic zone encompasses the coastal waters extending from the shoreline to the edge of the continental shelf. Brissus gigas is frequently encountered in areas with seagrass beds, coral reefs, and lagoons. The species’ preference for soft, sandy substrates allows it to burrow effectively, seeking refuge and protection from predators.
Taxonomy
Brissus gigas is a member of the Class: Echinoidea, Order: Spatangoida, and Family: Brissidae. These classifications reflect the evolutionary relationships and shared characteristics of this species with other sea urchins. The Echinoidea class includes all sea urchins, which are characterized by their radial symmetry, spiny body, and five-part symmetry. The Spatangoida order encompasses the heart urchins, which are specialized for burrowing and have a flattened, heart-shaped test. The Brissidae family includes a diverse group of heart urchins, and Brissus gigas is one of its notable members.
Feeding
Brissus gigas is an opportunistic deposit feeder. It feeds primarily on detritus, organic matter, and small organisms found in the sediment. The sea urchin’s feeding apparatus, called Aristotle’s lantern, is adapted for scraping and ingesting these materials. The spines and tube feet are used to move sediment and bring food particles to the mouth. Brissus gigas‘s role in marine ecosystems is significant as it contributes to the recycling of nutrients and organic matter.
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