Gracilechinus
Gracilechinus is a genus of sea urchins in the family Echinometridae. It is characterized by its relatively gracile (slender) test (the hard shell that encloses the urchin), which gives the genus its name. The genus contains only two recognized species, both of which are found in the Indo-Pacific region: Gracilechinus acutus and Gracilechinus echinatus.
Common Names
Common names for Gracilechinus species include "slender sea urchin" and "spiny sea urchin," although these names may also be used for other urchin species with similar appearances.
Characteristics
Sea urchins in the genus Gracilechinus are characterized by the following traits:
- Test shape: The test is typically somewhat flattened and oval, with a relatively slender and delicate appearance compared to other echinoids.
- Spines: The spines are long and slender, often with a sharp point. They can be of various colors, including shades of brown, black, and white.
- Tube feet: Gracilechinus urchins have numerous tube feet, which they use for locomotion, feeding, and respiration.
- Mouth: The mouth is located on the ventral surface of the test, and it is surrounded by five teeth that form the "Aristotle's lantern," a specialized structure used for feeding.
- Anus: The anus is located on the aboral (upper) surface of the test.
Environments
Gracilechinus species are typically found in shallow, rocky intertidal and subtidal environments, often in areas with high wave action. They are also known to inhabit coral reefs and seagrass beds.