Accacoelium contortum (Trematoda : Accacoeliidae) a trematode living as a monogenean: morphological and pathological implications
Ahuir-Baraja, Ana Elena (Universitat de València. Institut Cavanilles de Biodiversitat i Biologia Evolutiva)
Padrós, Francesc 1965- (Universitat Autònoma de Barcelona. Departament de Biologia Animal, de Biologia Vegetal i d'Ecologia)
Palacios-Abella, Jose Francisco (Universitat de València. Institut Cavanilles de Biodiversitat i Biologia Evolutiva)
Raga, Juan Antonio (Universitat de València. Institut Cavanilles de Biodiversitat i Biologia Evolutiva)
Montero, Francisco Esteban (Universitat de València. Institut Cavanilles de Biodiversitat i Biologia Evolutiva)

Date:	2015
Abstract:	Accacoelium contortum (Rudolphi, 1819) Monticelli, 1893 is a frequent but poorly known trematode found on gills, pharynx and digestive tract of the ocean sunfish Mola mola (L. ). Although the morphology of A. contortum agrees with that of a typical endoparasitic trematode, with two relatively small suckers and no large holdfasts, this parasite is normally ectoparasitic. The main objective of this paper is to explore this peculiar host-parasite relationship. A total of 106 ocean sunfish were examined for the presence of A. contortum. The oropharyngeal chamber (gills and pharynx) and the digestive tract were analysed. As the previous descriptions of this species seem to be based on contracted specimens, for the morphological study the parasites were killed using two methods: with hot 70 % ethanol (with relaxed bodies) and with 70 % ethanol at room temperature (with contracted bodies). For histological studies, samples from fresh fish with parasitised left gills, pharynx and digestive tract were fixed in buffered 10 % formalin. For molecular studies the 18S, 28S and ITS-2 sequences were provided and compared with the available data in GenBank®. New information on the morphology of A. contortum and on the parasite-related response and pathological alterations in the host are given. New diagnostic traits for some structures are provided: e. g. tegumental papillae of the forebody with apical digitiform swellings and mouth surrounded by a circum-oral crown of simple papillae. The length of the ventral sucker peduncle and the position of the vitellarium were found to be associated with the contraction degree of the specimen. Immature individuals of this species are described for the first time. An intense proliferative inflammatory response of host gill and pharynx epithelium at the host-parasite interface was detected and parasites became partially covered by overgrowths of host tissues. The induction of prominent histological alterations associated with A. contortum seems to be an adaptation to the external environment, an unusual location for trematodes.
Grants:	Ministerio de Ciencia e Innovación AGL 2012-20892
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Mola mola ; Accacoeliid ; Ectoparasitism ; Morphology ; Immature specimens ; Pathology ; Adaptation
Published in:	Parasites & vectors, Vol. 8 (October 2015) , art. 540, ISSN 1756-3305

DOI: 10.1186/s13071-015-1162-1
PMID: 26471059

11 p, 3.8 MB

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