12th International Conference on Harmful Algae

INTERNATIONAL SOCIETY FOR THE STUDY OF HARMFUL ALGAE12 th <strong>International</strong> <strong>Conference</strong> on Harmful Algae, Copenhagen, Denmark, 4-8 September 2006stage cells. In general, diatomresting stages are able to germinateunder a wider temperature rangethan dinoflagellates cysts, whereasdinoflagellate cysts are able togerminate under lower light intensitylevels than diatom resting stages. Inthis talk, the different physiologicalresponses to environmental factorswithin dinoflagellate/diatom restingstages will be examined and thesignificance of different seedingstrategies will be discussed.O.13-02The life cycle of Pyrodiniumbahamense var. compressum(Dinophyceae) in cultureSession: O.13 - Life cyclesPresentation time: 09:30 - 09:50Setsuko Sakamoto 1 , M Yamaguchi 1 ,EF Furio 21 FEIS, Fisheries Research Agency,HIROSHIMA, Japan2 NFRDI, QUEZON, PhilippinesPyrodinium bahamense var.compressum has resting cyst stagein its life cycle. However, severalprocesses in the life cycle areobscure, because most of previousstudies based on observation of thenatural populations. In presentstudy, we investigated cystformation and germinationprocesses of P. bahamense inculture and revealed that the cystswere formed by sexual reproductionand the sexuality was homothallic.Resting cysts were spherical toovoid and covered with many longprocesses. The cysts were formedin not only the crossing cultures butin the clonal cultures after over 35days of incubation under 30 °C.Both crossing and clonal cysts werenot able to distinguish by the cellsize and the external morphologyeach other. Relative DNA contentsof the resting cysts were 2C DNAwhile the vegetative cells were 1CDNA. Both crossing and clonalcysts germinated at 30 °C underlight and dark cycle after 2.5-5months. Therefore dormancy periodis necessary at least 2.5 months forgermination of P. bahamense cyst.On the basis of the results,schematic representation of the lifecycle of P. bahamense var.compressum will be presented.O.13-03Life cycle traits and populationdynamics of Pseudo-nitzschiamultistriata in the Gulf of Naples(Mediterranean Sea)Session: O.13 - Life cyclesPresentation time: 09:50 - 10:10D D'Alelio, A Amato, A Lüdeking, MRibera d’Alcalà, D Sarno, A Zingone, MMontresorStazione Zoologica 'Anton Dohrn', NAPOLI,ItalyThe potentially toxic diatomPseudo-nitzschia multistriata hasbeen recorded in the Gulf of Naplessince 1996. The species occursfrom late summer to early spring,with two periods of majorabundance (up to 200 cells ml -1 ) inlate summer-autumn and in earlywinter. Within the EU Project SEED,the potential role of life cycle traits inthe population dynamics of thespecies is investigated. In thispaper, data are presented ongenetic diversity, size reduction andmode of sexual reproduction. Withinthe species two ITS genotypes areidentified, which co-occur in thesame period of the year. Sexualreproduction requires the pairing ofdistinct mating types. Theauxospore allows the reestablishmentof the maximum size(ca. 80 µm), while progressive cellsizereduction down to 30 µm58