Muscle formation during embryogenesis of the polychaete Ophryotrocha diadema (Dorvilleidae) – new insights into annelid muscle patterns

摘要: The standard textbook information that annelid musculature consists of oligochaete-like outer circular and inner longitudinal muscle-layers has recently been called into question by observations a variety complex muscle systems in numerous polychaete taxa. To clarify the ancestral arrangement this taxon, we compared myogenetic patterns during embryogenesis Ophryotrocha diadema with available data on oligochaete myogenesis. This work addresses conflicting views ground pattern annelids, adds to our knowledge evolution lophotrochozoan Somatic can be classified trunk, prostomial/peristomial, parapodial complexes. trunk muscles comprise strong bilateral pairs distinct dorsal ventral strands. latter are first differentiate They originate within peristomium grow posteriorly through continuous addition myocytes. Later, also expand anteriorly form prostomial muscles. Four embryonic parapodia an anterior-to-posterior progression, significantly contributing somatic musculature. Several diagonal transverse present dorsally. Some situated external muscles, which implies they homologous oligochaetes. These fibers only weakly developed, do not appear complete circles. Comparison showed similarities between processes those species, allows us relate diverse adult arrangements these taxa each other. findings provide significant clues for interpretation evolutionary changes