Development & Growth

Morgan Hunt

Science Period A

Asteroidean Development and Growth



Asteroids are deuterostomes. When eggs become fertilized they become larvae. They live in the ocean as plankton. They are free-swimming organisms, moving through the ocean by using beating cilia. They are bilaterally symmetric but one side of the body grows more than the other in the beginning; meaning you can tell which side is the left and which side is the right, unlike adults where everything looks the same. Eventually the bigger side absorbs the smaller side. After that, the body is formed into five parts around a central axis; resulting in radial symmetry. Soon, they go through a complete metamorphosis, settle to the bottom, and grow into adults

Although a lot of information about the metamorphosis that they go through to become adults has not been documented, A. Ruben’s go through a period without a functional metanephridial system (excretory gland found in many types of invertebrates) where it also lacks other vital functions. Also, madreporite (opening used to filter water into the water vascular system of echinoderms) papulae (skin gills) and pedicellariae (they perform necessary cleaning functions) only first appear after metamorphosis has been completed.

Not a lot is known about what affects survival during the planktonic phase of Acanthaster planci (Linnaeus), the crown of thorns starfish, besides the fact that sometimes fish eat newly released eggs.



Freeman, S. (n.d). Asteroidea (Sea Stars). In Answers. Retrieved February 2009, from http://www.answers.com/topic/asteroidea-sea-stars-biological-family.



GONDOLF Annette L The aboral surface of Asterias rubens L. retrieved February 2009
From http://cat.inist.fr/?aModele=afficheN&cpsidt=13964217