Figure 9

Ultrastructure of the main tentacular neurite bundle in competent larvae of Phoronopsis harmeri . Thin cross sections. (A) A panorama of the two dorsolateral groups of perikarya (indicated by boxes), which are located near the youngest tentacles. The dorsal side of the larva is at the top. (B) Ultrastructure of a portion of the dorsolateral group of perikarya, which includes sensory (blue) and nonsensory (pink) cells. (C) One of the sensory cells (blue), which are scattered along the tentacular neurite bundle. (D) Details of the organization of the nonsensory perikaryon, which is located between neurites of the main tentacular neurite bundle on the lateral side of the larva. (E) Two large nonsensory prikarya associated with the tentacular neurite bundle. The synaptic contacts are indicated by arrowheads. Abbreviations: bb – basal body; bc – blastocoel; bl – basal lamina; G – Golgi apparatus; mc – muscle cell; mi – microvilli; n – nucleus; nf – nerve fibers; p – perikaryon; sr - striated rootlet.