Efeito do parasita dinoflagelado Amyloodinium ocellatum em ostras Crassostrea gigas em cultivos multitróficos
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2021
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A aquacultura é hoje uma atividade muito praticada e com previsões de expansão, de modo a
acompanhar o crescimento da população humana e a consequente necessidade de produção de
alimentos. Uma das grandes ameaças, capaz de causar perdas enormes em explorações,
particularmente, em produções semi-intensivas e intensivas de peixes marinhos e que exige
medidas atempadas, é a ocorrência de parasitas, tais como o dinoflagelado Amyloodinium
ocellatum, em peixes. Sendo a ostra um organismo filtrador, muitas vezes co-produzida com os
peixes, em cultivos multitróficos, surge o interesse de verificar o efeito deste organismo,
nomeadamente da espécie Crassostrea gigas, comum na costa portuguesa. Neste trabalho, as
ostras foram expostas ao parasita A. ocellatum e os efeitos desta exposição foram observados
através da utilização de 2 metodologias (histologia e biologia molecular) e ainda identificado por
sedimentação de fezes. As hipóteses colocadas antes da realização deste estudo foram (1) as ostras
(C. gigas) poderem funcionar como elemento mitigador da infeção com A. ocellatum, funcionando
como possível alternativa para combater a amiloodiniose e (2) as ostras funcionarem como vetor
disseminador da infeção provocada pelo parasita A. ocellatum. Este trabalho consistiu na (1)
realização de um ensaio experimental com vista à determinação dos efeitos da incidência
parasitária de A. ocellatum na ostra, e (2) impacto da presença de ostras na capacidade infetante
do parasita. Segundo os exames de sedimento de fezes, análises histológicas e de biologia
molecular, o parasita aparenta ter provocado lesões nas branquias e trato digestivo da ostra, embora
sem que cause, obrigatoriamente a sua morte. Posteriormente, é libertado nas fezes, revelando
capacidade locomotiva, o que nos levou a acreditar que preservou o sentido de busca por um
hospedeiro, utilizando a ostra como reservatório e vetor em caso de transporte de ostras infetadas
com A. ocellatum para outras explorações aquícolas. Este resultado pode revelar-se importante na
medida em que a ostra ao conter e transportar A. ocellatum no seu interior, liberta-o em
tanques/explorações diferentes causando surtos em zonas indemnes e consequentemente perdas
económicas elevadas.
Aquaculture is nowadays a widely practiced activity and with projected growth, in order to keep up with the increase of the human population and the consequent need for food production. One of the major threats that can cause huge losses on fish farms, particularly in semi-intensive and intensive marine fish farms, when not prevented, is parasitation by Amyloodinium ocellatum in fishes. As the oyster is a filtering organism, often co-produced with fish, in multitrophic cultures, there is interest in verifying the effect of this organism, namely the specie Crassostrea gigas, common on the Portuguese coast. In this work, oysters were exposed to the parasite A. ocellatum and the effects of this exposure were observed through the use of 2 methodologies (histology and molecular biology) and further identified by fecal sedimentation. The hypotheses proposed before conducting this study were (1) oysters may act as a mitigating factor for A. ocellatum infection, functioning as a possible alternative to prevent amyloodiniosis and (2) oysters function as a vector for the spread of infection caused by parasite A. ocellatum. This work consisted of (1) carrying out an experimental test to determine the effects of the parasitic incidence of A. ocellatum on the oyster, and (2) evaluating the impact of the presence of oysters on the parasite's infective capacity. According to oyster feces sediment, histological and molecular biology methodologies, the parasite appears to have caused damage to the gills and digestive tract of the oyster, although without necessarily causing its death. It is subsequently released from feces, revealing locomotive capacity, which led us to believe that it preserved the sense of searching for a host, using the oyster as a reservoir and vector in the case of transport of oysters infected with A. ocellatum to other aquaculture farms. This result can prove to be important as the oyster, when containing and transporting A. ocellatum inside, releases it in different tanks/farms causing outbreaks in free areas and consequently high economic losses
Aquaculture is nowadays a widely practiced activity and with projected growth, in order to keep up with the increase of the human population and the consequent need for food production. One of the major threats that can cause huge losses on fish farms, particularly in semi-intensive and intensive marine fish farms, when not prevented, is parasitation by Amyloodinium ocellatum in fishes. As the oyster is a filtering organism, often co-produced with fish, in multitrophic cultures, there is interest in verifying the effect of this organism, namely the specie Crassostrea gigas, common on the Portuguese coast. In this work, oysters were exposed to the parasite A. ocellatum and the effects of this exposure were observed through the use of 2 methodologies (histology and molecular biology) and further identified by fecal sedimentation. The hypotheses proposed before conducting this study were (1) oysters may act as a mitigating factor for A. ocellatum infection, functioning as a possible alternative to prevent amyloodiniosis and (2) oysters function as a vector for the spread of infection caused by parasite A. ocellatum. This work consisted of (1) carrying out an experimental test to determine the effects of the parasitic incidence of A. ocellatum on the oyster, and (2) evaluating the impact of the presence of oysters on the parasite's infective capacity. According to oyster feces sediment, histological and molecular biology methodologies, the parasite appears to have caused damage to the gills and digestive tract of the oyster, although without necessarily causing its death. It is subsequently released from feces, revealing locomotive capacity, which led us to believe that it preserved the sense of searching for a host, using the oyster as a reservoir and vector in the case of transport of oysters infected with A. ocellatum to other aquaculture farms. This result can prove to be important as the oyster, when containing and transporting A. ocellatum inside, releases it in different tanks/farms causing outbreaks in free areas and consequently high economic losses
Descrição
Orientação: Ana Maria Duque de Araújo Munhoz ; Florbela Maria Benjamin Soares ; Cátia Andreia Lourenço Marques
Palavras-chave
MESTRADO INTEGRADO EM MEDICINA VETERINÁRIA, MEDICINA VETERINÁRIA, AQUICULTURA, MOLUSCOS MARINHOS, PARASITAS, PATOLOGIA, VETERINARY MEDICINE, AQUACULTURE, MARINE MOLLUSCS, PARASITES, PATHOLOGY