ABSTRACT
Abstract Present knowledge of polychaete reproduction, developmental mode, gametogenesis patterns, sperm structure, and larval morphology are reported. Based on published data, some life-cycle and life-history traits are also examined and reviewed across families, in order to summarize the main lifestyle patterns. Polychaetes show a great diversity in reproductive traits, but some patterns can be found, and the families can be grouped within long-living iteroparous forms, semelparous forms, and short-living iteroparous forms, the first being the most common strategy. Phylogenetic constraints seem to be present especially at family level, influencing the egg-size and/or the developmental mode. Each family shows a characteristic range of egg-size and a more common developmental mode, even though different developmental modes can be found within single families, reflecting the high plasticity of this group, and the probable independent evolution of developmental mode at family level. The importance of morphological constraints is also discussed.
