New type of gland discovered in cestodes: neurosecretory neurons release a secret into the fish host

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Abstract

In 5 species of cestode plerocercoids parasitizing fish, free endings of peripheral neurosecretory neurons were found in the tegument in the ultrastructural study. These free terminals secreted vesicles on the tegument surface and into the host body. An increase in secretion under the influence of the blood serum of a fish host has been experimentally shown. In the body of cestodes, neurosecretory neurons (NN) form paracrine-type contacts near the cell membranes of the frontal glands, tegument, and muscles, performing the function of endocrine glands. Simultaneously, NN function as exocrine glands and secrete so-called manipulative factors that influence the physiology of the host.

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N. M. Biserova

Lomonosov Moscow State University

Author for correspondence.
Email: nbiserova@yandex.ru
Russian Federation, Moscow

I. A. Kutyrev

Institute of General and Experimental Biology, Siberian Branch of the Russian Academy of Sciences

Email: nbiserova@yandex.ru
Russian Federation, Ulan-Ude

V. V. Malakhov

Lomonosov Moscow State University

Email: nbiserova@yandex.ru

Academician of the RAS

Russian Federation, Moscow

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2. Fig. 1. Free terminals in the tegument and neurosecretory neurons (NN). a is a diagram of the structure of the ciliary and cup–shaped endings of neurons in the cestode tegument. b – scheme of exo- and endocrine secretion by peripheral NN: 1 – neuromuscular paracrine contact; 2 – exocrine secretion to the surface of the tegument; 3 – contact with the frontal glands of the paracrine type; 4 – secretion in the zone of the basal plate of the tegument. c, d, d – L. alternans: a group of cup-shaped endings (arrows) with secretory vesicles in the tegument (c, d) and a longitudinal section (e) of the neurosecretory terminal (NST) included in the tegument. e – P. phocarum: NST in contact with the tegmental process (T). g – D. dendriticus: paracrine contact of NST with muscles under the tegument (arrows); cv, light vesicles. z – P. phocarum: a neurosecretory neuron (NSN) in contact with the processes of the frontal glands (FG) and muscles (arrows).

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