Common Amur starfish
As a rule,
a flattened body characterizes these echinoderms, smoothly passing into
radial arms (5-40) called rays. The ray shape and structure are highly
diverse, from broad and short to impart the animal pentagonal contours
to thin and long, reminiscent of feelers. Unlike in lilies, the starfish
mouth and ambulacral grooves are situated on the lower body surface facing
In cases when starfish have anal openings, it is situated, like also the madrepore plate of the ambulacral system, on the upper (dorsal) body surface.
All starfish are mobile organisms moving along the substrate by means of their ambulacral legs situated in ambulacral grooves. Alike lilies, starfish have no pronounced anterior=posterior axis, nor any head end. Starfish are perfect radial animals.
Their skeletal plates and spines are highly diversified, occasionally transforming into specific surface organs, pedicillaria . Under a microscope, you can see that the pedicellaria represents a group of several elongated bones that function as scissors or pincers, with which the starfish can clean their body surface of various overgrowing organisms, always wanting to saddle such convenient hosts.
Most starfish are predators and corpse-eaters, but some are also known to be detritus-eaters and filters. Nor is cannibalism infrequent. When a starfish captures a large victim, its stomach can turn inside out to seize its prey.
Starfish larvae are called bipinnaria and brachyolaria; however, there are starfish characterized by direct development and capable of bearing their own young and caring of their offspring. Larvae that can feed during development in plankton are called planktonophorous, and those that do not feed on plankton larvaeЧlecitotrophous.
Today, approximately 1,500 starfish species
are known to biologists, most of them inhabitants of tropical seas.
We know of twenty-five starfish species that live in the waters of Southern Primorye, and our story is about the most typical and frequently occurring representatives of this class of Echinodermata.