Fig. 4. Whole-mount zebrafish larvae labelled with antibodies against Hu (human neuronal protein) and acetylated tubulin (AcT). (A) Whole larva at 7 d.p.f. The asterisk indicates the region of the gut where both retrograde and anterograde contraction waves originate. (B) At 4 d.p.f. (before onset of exogenous feeding) the distal part of the intestine (DI) is already densely innervated by nerve fibres as well as nerve cell bodies. (C) The number of Hu-positive nerve cell bodies showed a marked decrease between the middle intestine and the posterior part of the intestinal bulb (proximal intestine) compared to the more anterior part of the bulb at the stages investigated. PI, proximal intestine; MI, middle intestine; DI, distal intestine.