Latin American & Caribbean Aquaculture 2019

November 19 - 22, 2019

San Jose, Costa Rica

IS Amyloodinium ocellatum A TOXIN-PRODUCING PARASITIC DINOFLAGELLATE?  A TOXICOLOGICAL STUDY

Márcio Moreira*, Lucía Soliño, José I. Navas, Pedro Rodrigues, Florbela Soares, Pedro Reis Costa
IPMA - Portuguese Institute for the Ocean and Atmosphere, EPPO - Aquaculture Research Station, Av. Parque Natural da Ria Formosa s/n, 8700-194 Olhão, PORTUGAL; CCMAR - Centre of Marine Sciences, University of Algarve, Campus de Gambelas, 8005-139 Faro, PORTUGAL. E-mail: marcio.moreira@ipma.pt

Amyloodiniosis is a parasitic disease caused by the dinoflagellate Amyloodinium ocellatum. This parasitosis affects more than one hundred species of aquacultured fish, with fast and asymptomatic outbreaks that results in high morbidity and mortality in brackish and marine warm water fish. This disease is considered a serious impediment to several warm water aquaculture species.

Fish mortalities are usually attributed to anoxia and osmoregulatory impairment due to heavy infestations or to opportunistic bacterial infections. However, the severe histopathological changes observed in fish spleen, in several blood parameters after 18-24h of A. ocellatum infestation and its phylogenetic proximity to Pfiesteria, Parvodinium and Paulsenella genera, known toxin producing dinoflagellates that affects finfish and shellfish, lead us to the hypothesis of  a possible toxin production by A. ocellatum.

To test this, we injected 50±1.25 g gilthead seabream (Sparus aurata) with lipophilic and hydrophilic extracts from A. ocellatum tomonts and compared it with a negative control injected with saline solution, and a positive control with A. ocellatum infested gilthead seabream (in triplicate, 15 per treatment). After 24 hours, we observed that gilthead seabream injected with the lipophilic extract presented spleen histopathological changes and blood haemolysis similar to the ones observed in A. ocellatum infested gilthead seabream.

After this, we tested several solid phase extraction (SPE) fractions obtained from the three life stages of A. ocellatum (tomonts, dinospores and trophonts) for haemolytic capacity and calcium channel inhibition. The results indicated a strong haemolytic capacity of the less polar fractions of the infesting (dinospore) and parasitic (trophont) stages of A. ocellatum (Figure 1).

This data strengthens the hypothesis of A. ocellatum as a toxin-producing dinoflagellate. Additional studies are being performed to elucidate the possible toxin produced by this parasite.

< Return to Session<< All Meeting Sessions