Evolutionary and Phylogenetic Effects in Meiobenthology

Discussions of phylogenetic links between animal groups often center on small animals, particularly when remote habitats such as deep-sea bottoms, aquatic caves, and groundwater systems are envisaged. Their body organization is often simple; does this simplification and the small size result from derived or progenetic trends, or does it reflect an archaic and evolutionary primitive trait? The analysis of genetic similarities through PCR methods, new and powerful tools in our attempts to disentangle the evolution of animal taxa, is increasingly being used in studies of meiofauna, especially since new methods are being developed that can process the DNA from even very small animals. The systematic interrelationships resulting from these analyses have been considered in the previous taxonomic account (Chap. 5). Here, we will examine the role of structural specializations, paleontological findings, and distributional processes related to the evolution of meiofauna.