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Starfish have no distinct excretory organs; waste ammonia is removed by diffusion through the tube feet and papulae. [22] The body fluid contains phagocytic cells called coelomocytes, which are also found within the hemal and water vascular systems. These cells engulf waste material, and eventually migrate to the tips of the papulae, where a ...
A brachiolaria is the second stage of larval development in many starfishes. It follows the bipinnaria. Brachiolaria have bilateral symmetry, unlike the adult starfish, which have a pentaradial symmetry. Starfish of the order Paxillosida (Astropecten and Asterina) have no brachiolaria stage, with the bipinnaria developing directly into an adult.
The Asterozoa are a subphylum in the phylum Echinodermata, within the Eleutherozoa.Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the classes Asteroidea (the starfish or sea stars), Ophiuroidea (the brittle stars and basket stars), Somasteroidea (early asterozoans from which the other classes most likely evolved), and Stenuroidea ...
Echinoderms have secondary radial symmetry in portions of their body at some stage of life, most likely an adaptation to a sessile or slow-moving existence. [15] Many crinoids and some seastars are symmetrical in multiples of the basic five; starfish such as Labidiaster annulatus possess up to fifty arms, while the sea-lily Comaster schlegelii ...
In being multiple-armed, it has lost the five-fold symmetry (pentamerism) typical of starfish, although it begins its lifecycle with this symmetry. The animal has true image-forming vision. [3] Adult crown-of-thorns starfish normally range in size from 25 to 35 cm (10 to 14 in). [4] They have up to 21 arms.
Internal features can also show symmetry, for example the tubes in the human body (responsible for transporting gases, nutrients, and waste products) which are cylindrical and have several planes of symmetry. Biological symmetry can be thought of as a balanced distribution of duplicate body parts or shapes within the body of an organism.
The unusual animals have unique body plans arranged in five equal sections that differ greatly from the symmetric head-to-tail bodies of bilateral animals, which have left and right sides ...
In being multiple-armed, it has lost the five-fold symmetry (pentamerism) typical of starfish, although it begins with this symmetry in its life cycle. Acanthaster brevispinus is readily distinguished from A. planci in that it has: dense blunt spines over the upper (aboral) surface of its disc; short pedicellaria on its aboral surface