There are approximately 2,000 species of sea stars that can be found in both tropical and cold oceans.
Echinoderms, which are marine invertebrates without a backbone, have a skeleton made up of hard calcite plates. Most sea stars exhibit pentameral symmetry, meaning they have five rays or arms.
While sea stars live in water, their similarities to fish end there. They lack gills, scales, and fins and are exclusively found in saltwater habitats. Interestingly, sea stars do not rely on lungs or gills for breathing; instead, they absorb oxygen directly from the surrounding water through a process called osmosis.
Sea stars utilize small tube feet located on the undersides of their bodies to move. Adult sunflower sea stars can achieve an impressive speed of one meter per minute by using their 15,000 tube feet.
Sea stars have a bony and calcified skin, which can feel rough or leathery. However, this outer layer serves as protection against predators. Additionally, their vibrant colors often serve to intimidate potential threats or help them blend into their surroundings. Despite these adaptations, sea stars are slow movers, making them vulnerable to a wide range of marine animals, including marine birds, crabs, fish, sharks, and even humans.
Sea Star Characteristics
