Figure 7
From: Comparative neuroanatomy suggests repeated reduction of neuroarchitectural complexity in Annelida
Neuroarchitecture in terebellid polychaetes. (a, b) Horizontal sections through the brain of Eupolymnia nebulosa. While the ribbon-shaped brain does not contain distinct neuropil compartments, an anterior-posterior stratification is revealed by FMRF-like (a) and histamine (b) immunoreactivity (anterior is towards the top of the picture). (c-h) Consecutive horizontal sections (proceeding ventrad in reading direction) showing serotonin immunoreactivity in the brain of the terebellid polychaete Thelpus cincinnatus. Similar to the condition in E. nebulosa, the brain in this species is confluent with the circumesophageal connectives, forming a ring-like band around the esophagus. Neuronal somata are located at the outer perimeter of the brain. Scale bars: 200 μm.