Lifeform of the week: Vibrant and resilient sea urchins

Sea urchins are fascinating creatures that have been around for millions of years, making them one of the best-preserved groups of animals in the fossil record. Despite their lack of brains or blood, sea urchins are still considered animals, thanks to their unique characteristics and adaptations.

Sea urchins belong to the echinoderm group, along with starfish and sea cucumbers, and there are around 950 species of sea urchins in existence. These marine invertebrates come in a variety of colors, from red to purple and green, making them a visually striking presence on the seafloor. Sea urchins typically live in groups of five to ten individuals among rocks and on the seabed, with some individuals living for over 30 years and even reaching ages of over 200 years.

One of the most distinctive features of sea urchins is their hard shell made of calcareous plates fused together to form a protective covering. This shell, along with their sharp spines, provides them with defense against predators. Despite their heavy shell, sea urchins are able to move using tube feet, which are tentacles with suction cups that allow them to grip surfaces and capture prey. Sea urchins also have the ability to regenerate their spines and tentacles if they are damaged.

While sea urchins are not typically aggressive, their spines can be venomous, and getting stung by a sea urchin can be painful. It is important to remove the spines promptly to prevent further complications. Some species, like the flower sea urchin found in the Indian Ocean, are particularly dangerous due to their venomous spines.

Sea urchins play a crucial role in maintaining the balance of marine ecosystems by feeding on algae, small animals, and other marine organisms. They are also an important food source for various predators, including seabirds, fish, otters, and even humans. Sea urchins reproduce sexually, with females releasing millions of tiny eggs into the water that are fertilized by male sperm. The young sea urchins spend time in the plankton before descending to the seabed and reaching sexual maturity at around five years of age.

In conclusion, sea urchins are remarkable creatures with unique adaptations that have allowed them to thrive for millions of years. Their hard shells, colorful appearance, and important role in marine ecosystems make them a fascinating subject of study and observation. Despite their prickly exterior, sea urchins are an essential part of the diverse and complex world beneath the waves.