![]() ![]() Medusan morphospace: phylogenetic constraints, biomechanical solutions, and ecological consequences. Recent insights into cnidarian phylogeny. Solenoid: a new aquiferous system to Porifera. New York: Academic Press 1974.Ĭavalcanti FF, Klautau M. Reproduction of marine invertebrates, Volume I: acoelomate and pseudocoelomate metazoans. Cold Spring Harbor: Cold Spring Harbor Laboratory Press 2004.Ĭampbell RD. Gastrulation in the Cnidaria and Ctenophora. Sunderland: Sinauer Associates 2003.īyrum CA, Martindale MQ. Class-level relationships in the phylum Cnidaria: molecular and morphological evidence. ![]() Paris: Muséum national d’Histoire naturelle 2006.īridge D, Cunningham CW, DeSalle R, Buss LW. Berkeley: University of California 1978.īlunt JW, Copp BR, Keyzers R, Munro MHG, Prinsep M. Intrigued by the mystery, Nickel decided to use an X-ray technique to take a close look at contracted and relaxed Tethya wilhelma sponges to find out how they contract without muscles ( p. However, no one had ever tested these ideas and crucially, neither hypothesis could explain how contracted sponges return to their full size. Competing hypotheses had suggested that either the connective tissue between sponge cell layers – the mesohyl – might mediate the contraction or the outer cell layer – the pinacoderm – could produce squeezing contractions. Michael Nickel from the Friedrich-Schiller-Universität, Germany, explains that despite lacking muscles, sponges are able to contract, but no one knew how. Lacking digestive, nervous and muscular systems, it is sometimes difficult to imagine that they are animals, yet sponges could hold the key to the debate about how muscles evolved. Travelling back in time along the evolutionary tree you eventually reach sponges possibly the earliest modern animals. ![]()
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