Fossil steroids record the advent of earliest known animals

February 05, 2009

Demosponges appeared 635 million years ago in era of climatic extremes and evolutionary developments

Using compounds preserved in sedimentary rocks more than 635 million years old, researchers have found some of the earliest evidence for the existence of animals.

Demosponges thrived in the shallow coastal waters of what is now Oman, according to scientist Gordon Love of the University of California at Riverside and colleagues from MIT and other institutions.

They report the results of their research in this week's issue of the journal Nature.

"Demosponges appeared during the Neoproterozoic era, 1,000 to 542 million years ago, an era of climatic extremes and biological evolutionary developments culminating in the emergence of animals and new ecosystems," said Love.

"These sponges currently represent the oldest evidence for animals in the fossil record."

The preserved compounds Love and colleagues discovered in these sponges, called steranes, exist in a wide variety of biochemical configurations, according to Stephen Macko, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

"The compounds are also known as 'biomarkers,' indicating that they can be traced directly to living organisms," said Macko.

The biomarker Love and colleagues identified, 24-isopropylcholestane, is found in living demosponges, and now has been observed in 635 million-year-old rocks, but was not seen in older samples of the same rock formation.

"The fact that these biomarkers were found in samples associated with sedimentary rocks that formed in shallow waters," said Macko, "lends support to the hypothesis that demosponges arose in warm shallow coastal seas."

Feeding on dissolved and particulate organic debris in the water, these animals eventually migrated to the deep sea. They now reside there, as well as in shallower coastal waters.

National Science Foundation

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	Lower and Middle Ordovician Lithistid Demosponges from the Mingan Islands, Gulf of St. Lawrence, Quebec, Canada by J. J. and Desrochers, A. Rigby (Author)
	Microscleres in demosponge classification by Robert Edward Hay. Reid (Author)
	Lower and Middle Ordovician Lithistid Demosponges from the Mingan Islands, Gulf of St. Lawrence, Quebec, Canada by The Paleontological Society (Publisher)
	HOW BODY PLANS LIMIT ACCLIMATION: RESPONSES OF A DEMOSPONGE TO WAVE FORCE by Stephen R Palumbi (Author)
	Silurian (wenlock) Demosponges From The Avalanche Lake Area Of The Mackenzie Mountains, Southwestern District Of Mackenzie, Northwest Territories, Canada (Palaeontographica Canadiana) by J. K. Rigby (Author), B. D. E. Chatterton (Author)
	Vintonia Doris: A new Mississippian demosponge from Arkansas by Matthew H Nitecki (Author)
	The Comparative Embryology of Sponges by Alexander V. Ereskovsky (Author) One of the major questions in the evolution of animals is the transition from unicellular to multicellular organization, which resulted in the emergence of Metazoa through a hypothetical Urmetazoa. The Comparative Embryology of Sponges contains abundant original and literary data on comparative embryology and morphology of the Porifera (Sponges), a group of 'lower Metazoa'. On the basis of this material, original typization of the development of Sponges is given and the problems concerning origin and evolution of Porifera and their ontogenesis are discussed. A morphogenetic interpretation of the body plan development during embryogenesis, metamorphosis and asexual reproduction in Sponges is proposed. Special attention is given to the analysis of characteristic features of the ontogenesis...
	Marine Invertebrates and Plants of the Living Reef by Patrick I. Colin (Author)
	Advances In Marine Biology, Volume 52 by D.W. Sims (Series Editor) Advances in Marine Biology was first published in 1963. Now edited by David W. Sims (Marine Biological Association, UK), the serial publishes in-depth and up-to-date reviews on a wide range of topics which will appeal to postgraduates and researchers in marine biology, fisheries science, ecology, zoology, oceanography. Eclectic volumes in the series are supplemented by thematic volumes on such topics as The Biology of Calanoid Copepods and Restocking and Stock Enhancement of Marine Invertebrate Fisheries. * More than 350 pages of reviews from leading researchers in marine biology * Includes over 90 images * Offers reviews on the biology of the glass sponge * Reviews protein metabolism in marine animals