Figure 11

Some nerve elements of the trunk in 3-day-old juvenile of Phoronopsis harmeri. Cross semithin (A) and thin (B-F) sections of the anterior body part. (A) Whole section with formed definitive digestive tract and blood vessels. (B) The giant nerve fiber, which is completely enveloped by two cells and accompanied by several nerve fibers of common diameter. (C) Group of nerve fibers (arrowheads) in the epithelium of descending branch of the digestive tract. (D) Large projection of nerve cell contains synaptic vesicles and located in the epithelium of descending branch of the digestive tract. (E) Projection of neurosecretory cell (arrowheads) in the epithelium of ascending branch of the digestive tract. (F) Neuron (pink) with dense-core synaptic vesicles and nerve fibers, some of which contain clear (electron-lucent) vesicles in the epithelium of the esophagus. Abbreviations: ab – ascending branch of digestive tract; am – anal mesentery; bc – blastocoel; bl – basal lamina; c3 – trunk coelom; cc – coelomic lining; cv – clear (electron-lucent) synaptic vesicle; db – descending branch of digestive tract; dcv – dense-core vesicle; ec – enveloping cell; ep – epidermis; llv – left lateral blood vessel; lm – longitudinal muscles; m – mitochondria; mc – muscle cells; mv – median blood vessel; n – nucleus; nf – nerve fiber; sv – synaptic vesicles.