ИСТИНА

Trypanorhynchean tapeworms possess complicated attachment organs that include twin dorsoventral bothria and a specialized rhyncheal apparatus with four tentacles. Trypanorhyncha are able to evert instantaneously the tentacles as a response to mechanical stimulation of the bothrial margin (Biserova et al 2017) and, thus, control by the nervous system is most likely. Recently in trypanorhynchean, only Grillotia erinaceus nervous system was study by ICC methods (Halton et al 1994; Crangle et al 1995). Immunocytochemistry of the brain in Progrillotia sp. from the spiral valve of Raja clavata have been studied with using indirect immunofluorescent labeling for α-tubuline and for serotonin (5-HT). Anti-5-HT immunoreaction (IR) was detected in the brain and outgoing nerves. The 5-HT-IR compartment of the brain consists of 4 large anterior lobes, 4 lateral lobes and a central unpaired lobe. Rich 5-HT-IR occurs in paired neuropiles in anterior and lateral lobes; the central lobe had less 5-HT-IR. Anterior lobes had a bigger size and richer 5-HT-IR in comparison with the lateral lobes. From the brain, anterior and lateral 5-HT-IR nerves extend to the level of the tentacle openings and bothrial lateral surface. Backward, the 5-HT-IR lateral nerves exit from lateral lobes and join the pair of main lateral nerves. 13-15 serotonergic neurons were found in the brain, 3-5 per lobe. 5-HT neurons had often three neurites and a large perikaryon with round nucleus. In the central unpaired lobe we detected 3 asymmetrically situated neurons. These neurons had one main neurite extended to the center of lobe, exactly in the X-shape crisscross commissure. For the first time we found the 5-HT neurons which are innervating the tentacle retractors; one neuron per retractor. Somas (7x12µm) locate in the apical retractor part and possess short distal and long proximal neurites. Anti-α-tubuline-IR was detected in the brain, nerves and protonephridial cells. Intensive α-tub-IR occurred in the large processes around neuropils, and in the nerves of bothria muscle and tentacle sheathe muscles. In one half of a scanned brain, 13 large α-tub-IR neurons are found which are separate cluster from 5-HT neurons. In the central lobe we found neurons with unusual rich α-tub-IR present in both somas and neurites. The neurons had large soma and two thick and long diagonally directed anterior and posterior neurites, and accessorial slim processes bifurcating from the anterior neurite. Main anterior and posterior neurites are diagonally directed from the dorsal to the ventral brain area, and most probably form the X-shape commissure of the brain. Unlike the brain structure of G. erinaceus, in the brain of Progrillotia sp. we found that a) 5-HT neurons are innervating the tentacle retractors; b) the X-shape commissure is including α-tub- and 5-HT-IR neurons; c) an asymmetrical position of 5-HT neurons in the central unpaired lobe.