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Diseases of Aquatic Organisms

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DAO 51:27-35 (2002)  -  doi:10.3354/dao051027

Effect of Pomphorhynchus laevis (Acanthocephala) on putative neuromodulators in the intestine of naturally infected Salmo trutta

Bahram Sayyaf Dezfuli1,*, Flavio Pironi1, Luisa Giari1, Cinzia Domeneghini2, Giampaolo Bosi2

1Department of Biology, University of Ferrara, Via Borsari 46, 44100 Ferrara, Italy
2Institute of Domestic Animals Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, Via Celoria 10, 20133 Milan, Italy

ABSTRACT: Immunohistochemical and pathological studies were carried out on the digestive tract of parasitized and uninfected specimens of Salmo trutta (L.). A total of 124 brown trout were collected on several occasions from 3 tributaries of the Brenta River, northern Italy. Twenty-eight individuals of S. trutta (22.6%) were parasitized with Pomphorhynchus laevis (Müller, 1776). The occurrence of P. laevis in the trout gut significantly increased the number of endocrine cells immunoreactive to calcitonin gene-related peptide (CGRP), β-endorphin, met-enkephalin, neuropeptide Y (NPY) and Substance P (SP) antisera. Moreover, bombesin-, cholecistokinin-8- (CCK-8), leu-enkephalin- and serotonin- (5-HT)-like immunoreactive cells were less numerous in the intestine of the parasitized brown trout. A strong positive immunoreactivity was observed in nerve fibres and neurones of the myenteric plexus of the parasitized fish; the antisera involved in this positive reactivity were bombesin, met-enkephalin, SP and vasoactive intestinal peptide (VIP). More neurones immunoreactive to anti-CGRP and anti-5-HT sera were noted in the myenteric plexus and in the inner layer of the tunica muscularis of the infected fish. Most of the above-mentioned neuromodulators are known to control gut motility, digestive/absorptive processes, as well as the immune response. The changes induced by parasites in the neuroendocrine system of the brown trout are discussed.

KEY WORDS: Acanthocephalan infection · Immunohistochemical · Neuromodulators · Digestive tract · Salmo trutta

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