An international team of scientists including Albert Poustka from the Max Planck Institute for Molecular Genetics in Berlin has discovered that Xenoturbellida and the acoelomorph worms, both simple marine worms, are more closely related to complex organisms like humans and sea urchins than was previously assumed.

Two groups of lowly marine worms are related to complex species including vertebrates (such as humans) and starfish.

The impact on levels of carbon dioxide in the Earth's atmosphere by the decaying remains of a group of marine creatures that includes starfish and sea urchin has been significantly underestimated.

By Alvarado, Juan Jose Abstract: Between October 2003 and July 2005, aggregation behavior of the sea urchin Astropyga pulvinta Lamarck was studied in Bahia Culebra, Costa Rica. This sea urchin forms aggregations during part of the year and then disappears.

By Crawford, Terry J Crawford, Bruce J Abstract: In Rarotonga, Linckia multifora (Lamarck) exists in two forms: a blue gray type that is found on the reef intertidally and a red form that is found subtidally.