title: HOMOTHALLIC AUXOSPORULATION IN PSEUDO-NITZSCHIA BRASILIANA (BACILLARIOPHYTA)(1).
abstract: Most pennate diatoms are allogamous, and various types of mating systems have been described. In Pseudo-nitzschia, reproductive stages have been identified in some species, and it is generally accepted that the genus is mainly heterothallic. Here we report homothallic auxosporulation of Pseudo-nitzschia brasiliana Lundholm, Hasle et G. A. Fryxell. To our knowledge, this is the first verified description of homothallic sexual reproduction in the genus. Auxospore formation was observed in all 16 subclones derived from three initial clonal cultures of P. brasiliana. Pairing was followed by production of two gametes per gametangium, which fused to give two zygotes. Each zygote (early auxospore) was initially spherical and adhered to one girdle band of the parental frustule. The two auxospores tended to expand parallel to each other and perpendicular to the parental frustule. Elongation was synchronous, slightly asynchronous, or totally asynchronous. The entire process of sexual reproduction, from gamete formation to the appearance of the initial vegetative cells, took 2-4 d. The occurrence of sex in a homothallic species seems an advantageous life strategy for this species in that any encounter between cells of the right size class is potentially sexual.
authors.affiliation: Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-49, E08003 Barcelona, SpainIRTA, Institut de Recerca i Tecnologia Agroalimentaries-Centre d'Aqüicultura, 43540 Sant Carles de la Ràpita, SpainDepartament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-43, E08003 Barcelona, Spain.
authors.forename: Sonia
authors.initials: S
authors.lastname: Quijano-Scheggia
authors.affiliation: Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-49, E08003 Barcelona, SpainIRTA, Institut de Recerca i Tecnologia Agroalimentaries-Centre d'Aqüicultura, 43540 Sant Carles de la Ràpita, SpainDepartament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-43, E08003 Barcelona, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Garcés
authors.affiliation: Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-49, E08003 Barcelona, SpainIRTA, Institut de Recerca i Tecnologia Agroalimentaries-Centre d'Aqüicultura, 43540 Sant Carles de la Ràpita, SpainDepartament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-43, E08003 Barcelona, Spain.
authors.forename: K
authors.initials: K
authors.lastname: Andree
authors.affiliation: Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-49, E08003 Barcelona, SpainIRTA, Institut de Recerca i Tecnologia Agroalimentaries-Centre d'Aqüicultura, 43540 Sant Carles de la Ràpita, SpainDepartament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-43, E08003 Barcelona, Spain.
authors.forename: Jose Manuel
authors.initials: JM
authors.lastname: Fortuño
authors.affiliation: Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-49, E08003 Barcelona, SpainIRTA, Institut de Recerca i Tecnologia Agroalimentaries-Centre d'Aqüicultura, 43540 Sant Carles de la Ràpita, SpainDepartament de Biologia Marina i Oceanografia, Institut de Ciències del Mar-CMIMA, CSIC, P. Marítim de la Barceloneta, 37-43, E08003 Barcelona, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Camp
keywords: Pseudo-nitzschia; auxosporulation; homothallic; sexual reproduction