The starfish belongs to a group of echinoderms characterized by their flattened, star-shaped bodies and hollow arms.

Typically, adults exhibit symmetry, with five arms radiating from a central disc. Their mouth is located on the underside of the central disc, forming the oral surface along with the arms.

Each arm features a groove with tiny tube feet extending from it, known as ambulacral grooves and tube feet, respectively. Beneath the skin, starfish have a skeletal structure composed of calcareous ossicles and muscular layers that enable movement of the tube feet.

Starfish are widely distributed in oceans worldwide, with the highest concentration found in the North Pacific. They prefer living in colonies and commonly inhabit seabeds with sand, rocks, or coral.

As carnivorous animals, their diet consists mainly of slow-moving marine organisms such as mollusks, sea urchins, crabs, and anemones, and they may even consume colorful corals. They exhibit strong reproductive capabilities, typically spawning in summer, with fertilization of eggs and sperm occurring in the seawater, leading to the formation of new offspring.

Body Wall and Skeleton

The body wall of echinoderms consists of the epidermis and dermis. The outermost layer is a thin epidermis overlaid with a single layer of ciliated columnar epithelial cells.

Interspersed among these epithelial cells are sensory nerve cells and mucous gland cells, whose secretions can trap debris on the body surface, which is then swept away by cilia. Below the epidermis lies a layer of nerve cells and fibrous tissue, forming the subepidermal nerve plexus of echinoderms.

This is followed by the dermis, which includes a thick layer of connective tissue and muscle. The muscles consist of an outer circular layer and an inner longitudinal layer, with well-developed longitudinal muscles on the oral side, facilitating arm movement. Inside the muscle layer lies a layer of the peritoneum.

The skeleton of echinoderms is derived from the mesoderm, constituting an endoskeleton located within the connective tissue of the body wall. It consists of a mesh-like structure formed by numerous separate ossicles of various shapes, connected by the connective tissue. These ossicles, which contain calcium carbonate with 10% magnesium carbonate, have perforations to reduce weight and increase strength.

Each ossicle begins with the secretion of a crystal by a cell in the dermis, surrounded by the accumulation of calcium carbonate secreted by surrounding cells, allowing ossicles to grow with the animal. The size, shape, and arrangement of ossicles are determined by the structure and arrangement of dermal cells.

In addition to ossicles, other skeletal components such as spines, and pedicellariae are dispersed on the body surface, serving defensive and sediment-clearing functions.

Value

In terms of medical value, starfish components have shown promising effects in treating hyperlipidemia and cardiovascular diseases.

Starfish can also yield collagen for capsule production. Ecologically, they play a crucial role in maintaining ecological balance. Economically, they possess high nutritional value, being rich in fats and proteins. In agriculture, they can be used for composting, while in industry, they are commonly processed into powdered feed.

In summary, the starfish stands out in the marine world with its unique features and critical ecological role. Our ongoing exploration and admiration of these captivating marine animals not only deepen our knowledge of oceanic life but also underscore the complex interdependence of all living beings within these vast ecosystems.