MORPHOMETRIC PROPERTIES OF SEROTONERGIC NEURONS IN CESTODA MESOCESTOIDES VOGAE LARVAE

The immunocytochemical study of cestode larvae, Mesocestoides vogae tetrathyridia (Cestoda, Mesocestoididae) detected serotonin-immunopositive neurons and fibers in the central and peripheral nervous system. The wholemounts were analyzed by confocal laser scanning microscopy. The size of serotonergic neurons, and the distance between the lateral nerve cords, and between the commissures were measured for the first time in the head, middle, and posterior regions of the larvae. Serotonergic nerve components of the M. vogae larvae were detected in the nerve ganglia in the head located between four suckers on the anterior part, as well as between clearly visible three pairs of lateral, dorsal, and ventral longitudinal nerve cords connected by transverse commissures. The distance between the lateral nerve cords was 130.90±33.92 µm, and between the commissures, 24.66±6.02 µm. Sizes of M. vogae’s neurons were as follows: length, 9.84±1.97 µm, and width, 7.19±1.50 µm. The largest serotonergic neurons were observed in the head region of the cestodes. The neurons in the head and middle regions of the body demonstrated the most intensive staining. The results indicate wide spreading serotonin in flatworms which is already found in the early stages of their life cycle.