Nephridial Systems

Project Title: Adaptations and evolution of nephridial systems in Annelida

Funding Source: University

Principle Investigator: Günter Purschke with Leonard Breitsprecher; in cooperation with Katrine Worsaae, Univ. Copenhagen, Alexander Tzetlin, Moscow State University

Investigations on evolution, systematics, phylogeny and functional morphology are in the focus of interest. Currently these investigations are carried out on annelids, the segmented worms, and those taxa which are presumed to be closely related to them. Special emphasis is laid to the phylogenetic relationships within and validity of Lophotrochozoa.

Typical annelids have a life cycle comprising an acoelomate larva and a coelomate adult. As such larvae should possess protonephridia and adults metanephridia and a blood vascular system. As several lineages show small body dimensions including a reduced coelom and blood vascular system and sometimes acoelomate body cavities in adults as well, the question arises what happened to the nephridial systems during these regressive evolutionary processes? Current investigations focus on two taxa, Protodriliformia and Nerillidae (see light micrographs below), which most likely evolved convergently into small body dimensions.

Nerilla antennata; mature female

Protodriloides chaetifer

Protodrilus adhaerens

Protodriloides chaetifer, TEM cross section showing almost completely absent body cavity