AME 66:183-197 (2012)  -  DOI:

Infection dynamics of Amoebophryidae parasitoids on harmful dinoflagellates in a southern Chilean fjord dominated by diatoms

Catharina Alves-de-Souza1,2,3,8,*, Daniel Varela4, José Luis Iriarte5,6,7, Humberto E. González1,6,7, Laure Guillou2,3

1Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, PO Box 567, Valdivia 5090000, Chile
2Université Pierre et Marie Curie, Paris 6, Station Biologique de Roscoff, Place Georges Teissier, Roscoff 29680, France
3Centre National de la Recherche Scientifique (CNRS), UMR 7144, Laboratoire Adaptation et Diversité en Milieu Marin, Place Georges Teissier, Roscoff 29680, France
4Centro de Investigación I-mar, Universidad de los Lagos, Casilla 557, Puerto Montt 5480000, Chile
5Instituto de Acuicultura, Universidad Austral de Chile, Los Pinos s/n, Puerto Montt 5480000, Chile
6Centro COPAS y COPAS Sur Austral, Universidad de Concepción, PO Box 160-C, Concepción 4030000, Chile
7Centro de Investigación de Ecosistemas de la Patagonia (CIEP), Coyhaique 5950000, Chile
8Present address: Laboratório de Ficologia, Departamento de Botânica, Museu Nacional/Universidade Federal do Rio de Janeiro, Quinta da Boa Vista S/N, São Cristóvão, Rio de Janeiro, RJ 20940-040, Brasil

ABSTRACT: Parasitoids belonging to Amoebophryidae (Marine ALVeolate Group II or MALV II) infecting dinoflagellates were investigated in Reloncaví Fjord (southern Chile) in the austral summer 2009. Of the 12 dinoflagellate species recorded during monthly sampling, Prorocentrum micans, Dinophysis acuminata, and Phalacroma rotundata were infected by Amoebophrya spp. To assess parasitoid control of host populations, the short-term dynamics of Amoebophrya spp. were followed for 21 d during a bloom of P. micans. Host mortality induced by Amoebophrya spp. (% hosts killed per day) was estimated by dividing prevalence by the generation time of these parasitoids. Parasitism by Amoebophrya spp. was responsible for ~10% of P. micans mortality between 8 and 17 March. The small subunit rDNA genes of individual parasitoids infecting different host cells were sequenced, and like most environmental sequences retrieved from this ecosystem in January and February, all belonged to the MALV II Clade 4. However, as soon as the P. micans bloom was detected, the MALV II genetic composition changed drastically, with the detection of Clades 1, 4 (a different sub-cluster than before), 5, 6, and 12. Our results suggest that different types of parasitoids belonging to Amoebophryidae likely infect dinoflagellates in Reloncaví Fjord, offering the first demonstration of the presence of important genetic diversity in MALV II inhabiting an ecosystem where dinoflagellate hosts are not the usual dominant phytoplanktonic organisms.

KEY WORDS: Amoebophrya · MALV II · Parasitism · Harmful algal blooms

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Cite this article as: Alves-de-Souza C, Varela D, Iriarte JL, González HE, Guillou L (2012) Infection dynamics of Amoebophryidae parasitoids on harmful dinoflagellates in a southern Chilean fjord dominated by diatoms. Aquat Microb Ecol 66:183-197.

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