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Data of Dissertation


Author: Renato José Reis Molica

Title: Contribution to the knowledge of ecology, toxicology and phylogeny of Cylindrospermopsis raciborskii (Cyanobacteria).

Year: 2003.    Full text (in Portuguese)


The increasing concern about Cylindrospermopsis raciborskii is due to the potential of this cyanobacterium to produce toxins and form blooms and mainly due to the raise of reports on its occurrence in aquatic ecosystems of many countries, including Brazil. In this sense, the objectives of this work were: 1) to evaluate the limnological characteristics of two drinking water suppliers - Tapacurá and Ingazeira reservoirs both located in Pernambuco State -, where C. raciborskii blooms are frequent, 2) to characterize the saxitoxins produced by a C. raciborskii strain (ITEP-018), 3) to identify the neurotoxins present during C. raciborskii and Anabaena spiroides bloom in Tapacurá reservoir and 4) to examine the genetic diversity of C. raciborskii strains. The results have shown that an environmental stability associated with a high level of nutrients and low light availability favored C. raciborskii blooms in Tapacurá and Ingazeira reservoirs. The strain ITEP-018 produces six saxitoxins, including a new analogue. The neurotoxins identified during a cyanobacterial bloom in Tapacurá reservoir were saxitoxins and an acetilcholinesterase inhibitor, probably anatoxin-a(s), produced by C. raciborskii and A. spiroides, respectively. The phylogenetic analyses have shown a high homology between Cylindrospermopsis sp. strains from the same geographical origin and those could be assembled in three different clusters: strains of European, American and African/Australian origins. The results show the necessity of continuous monitoring of toxic cyanobacterial blooms and implementation of management plans to diminish the trophic state of aquatic ecosystems.