Evaluación de daños histológicos por parásitos en chame Dormitator latifrons (Richardson, 1844) silvestres y en producción de la provincia de Manabí, Ecuador

Abstract

The Dormitator latifrons chame is considered an important fishing and aquaculture resource in Ecuador, the only country that grows it, identifying itself as a product in the daily diet of the population of the Ecuadorian coast. Knowledge of the pathogens and / or diseases that affect species with potential for cultivation is necessary for the development of aquaculture, not only to reduce mortalities, but also to reduce injuries that could cause rejection of the post-harvest product. Therefore, the objective of this investigation was to evaluate the histological damage by parasites in chame D. latifrons (Richardson, 1844) wild and under culture conditions in the province of Manabí, Ecuador. A total of 225 organisms were collected in three sites of the Rio Chone estuary (Larrea, La Segua wetland and Chamera), in the months of January to May 2018. Each individual was recorded the total length (Lt), the Weighed (g) and sex, and were checked externally and internally for parasites and / or clinical signs of tissue alterations. Small fragments (<3 mm3) of tissues and organs without alterations and with presence of parasites and / or tissue alterations without evident parasites, were fixed in 10% neutral formalin and processed by the histological technique of inclusion in paraffin, cut into sections of 5 μm, stained with the routine dyes Hematoxylin-Eosin and mounted with Entellan® resin (Humason, 1979). The obtained lamellae were observed in an Olympus® BX53 microscope and the images captured with a 9.1 MP AmScope® camera adapted to the microscope. The microanatomy of the main chame organs (gills, heart, liver, intestine, kidney and spleen) and the tissue alterations caused by the parasite species found were described. The main histological finding, in this species considered agastric, is the presence of a well-developed stomach with abundant secretory glands and folds. Ascocotyle sp. was the most prevalent parasitic species (58.67%) while Southwellina sp. it was the least prevalent species (0.89%). Regarding the affected organs and tissues, the highest prevalences of parasites were observed in gills (52.00%) followed by the intestine (34.67%), while the lowest prevalence was observed in gonads (1.33%). The main histological damages were caused by Ascocotyle sp. in gills and Contracaecum sp. in intestine and liver; with deformations of arches and branchial filaments in the case of gills, and foci of necrosis, extensive areas of chronic inflammation and loss of the parenchyma, in the case of intestine and liver. The results present in this research not only lay the foundations for the prevention and diagnosis of possible diseases in chame aquaculture, but also contribute to the development of their culture based on the anatomical histological information that it provides.