Starfish, often known as sea stars, are echinoderms with a star-shaped body that belong to the Asteroidea class. These names are commonly attributed to ophiuroids, which are appropriately referred to as brittle stars or basket stars in common usage. Because they belong to the Asteroidea class, starfish are sometimes known as asteroids. Starfish may be found on the bottom in all of the world’s seas, from the tropics to the icy depths of the polar regions. They may be found from the intertidal zone to 6,000 meters (20,000 feet) below the surface.

Starfish are invertebrates that live in the sea. They normally have a center disc and five limbs, however some species have more. The aboral or top surface is covered with overlapping plates and can be smooth, granular, or spiny. Many species are vividly colored, ranging from red to orange, while others are blue, grey, or brown in color. A hydraulic system powers the tube feet of starfish, which have a mouth in the center of the oral or bottom surface. They are primarily predators on benthic invertebrates and are opportunistic eaters.

Several species have unique eating habits, such as stomach eversion and suspended feeding. They have complicated life cycles and are capable of both sexual and asexual reproduction. Most have the ability to regrow injured or lost limbs, as well as shed arms to defend themselves. The Asteroidea play a number of important ecological roles.

The ochre sea star (Pisaster ochraceus) and the reef sea star (Stichaster australis) are two starfish species that have become well-known as instances of the keystone species concept in ecology. The tropical crown-of-thorns starfish (Acanthaster planci) is a voracious coral predator across the Indo-Pacific area, and the northern Pacific sea star is one of the world’s top 100 invasive species.

Starfish have a long fossil record, reaching back to the Ordovician period approximately 450 million years ago, although it is scant since starfish disintegrate after death. Only the animal’s ossicles and spines are likely to be retained, making remains difficult to find. Starfish have been featured in literature, folklore, design, and popular culture due to their attractive symmetrical form. They are occasionally collected as curios, utilized in design or as logos, and, despite their toxicity, consumed in some civilizations.

A thin cuticle, an epidermis made up of a single layer of cells, a thick dermis made up of connective tissue, and a thin coelomic myoepithelial layer that supplies longitudinal and circular musculature make up the body wall. Ossicles are calcium carbonate components that form an endoskeleton in the dermis.

These are honeycombed formations made up of lattices of calcite microcrystals. They come in a variety of shapes and sizes, with some having external granules, tubercles, and spines, but the majority are tabular plates that fit together neatly in a tessellated pattern to create the aboral surface’s primary covering. The madreporite (the water vascular system’s entry), pedicellariae, and paxillae are examples of specialized structures. Pedicellariae are complex ossicles with jaws that resemble forceps.

Download Starfish Silhouette PNG transparent background images