Starfish (properly called sea stars) are marine invertebrates belonging to the phylum Echinodermata. There are roughly 2,000 species of sea stars living throughout the world’s oceans. They are entirely marine animals; none live in fresh water. These resilient creatures lack a brain, true blood, and a heart, relying instead on a highly sophisticated water vascular system. Fascinating Types of Sea Stars
While the classic five-armed shape is the most common, sea stars feature immense physical diversity:
Sunflower Sea Star (Pycnopodia helianthoides): One of the largest and fastest species, featuring 16 to 24 limbs and an impressive one-meter arm span.
Crown-of-Thorns Sea Star (Acanthaster planci): A large, venomous predator covered in sharp spikes that primarily feeds on coral polyps.
Multi-Armed Variants: Some deep-sea and tropical species can grow up to 40 arms. Unique Anatomy and Behaviors
Sea stars operate through a series of bizarre biological adaptations: National Geographic Starfish (Sea Stars) | National Geographic