Figure 3
Variation in position of the brain and ciliary sense organs, as represented by 4 naidid species. Images are intensity sum projection of sagittal Z-stacks. Brain boundaries are shown by paired brackets; approximate prostomium/peristomium and peristomium/segment 1 boundaries are marked by dashed lines; ciliary sense organs are indicated by arrowheads. The brain is located almost completely within the prostomium and peristomium in Tubifex tubifex (A), peristomium and segment 1 in Allonais paraguayensis (B), segment 1 in Chaetogaster diaphanus (C) and back in segments 1 and 2 in Paranais litoralis (D). Specimens were stained for DNA (blue), serotonin (red), acetyl-tubulin (green), and F-actin (white). The dense acetyl-tubulin staining near the center of the animal in A, B, and D corresponds to the heavily ciliated pharynx. Scale bars: 25 μm.