Neurotoxicity of two Cylindrospermopsis raciborskii (cyanobacteria) strains to mice, Daphnia, and fish

Abstract

In recent decades, toxic cyanobacterial blooms have become frequent in the drinking water supply and have caused serious deleterious effects to domestic and wild animals, as well as to humans. Two strains of the cyanobacterium species Cylindrospermopsis raciborskii (T2 and T3) were isolated from the Billings Reservoir (São Paulo, Brazil) and cultured in the laboratory for use in acute toxicity tests with mice, micro crustaceans, and fish. The results showed high toxicity of both strains in mouse bioassays (median lethal dose [LD50]; 24 h = 9.6 and 27 mg/kg; intraperitoneal injections). The symptomatology presented by mice was typical of neurotoxicosis, such as trembling, ataxia, convulsions and death by respiratory arrest. Acute and chronic effects were observed in Daphnia similis and Ceriodaphnia dubia, such as immobilization and reduced fitness, respectively. Although acute effects were not detected on the adult fish Danio rerio, chronic toxicity was observed for its larval stage. Although both strains showed high toxicity to all organisms, no consistent pattern was seen between the different bioassays and strains. The results also showed that C. raciborskii toxins are stable to heat and to extreme pH variations. Because of high toxicity of these strains and the potential risk to human health, the authors propose a revision of the legislation regarding safety factors for drinking water supply.

Effects of Cylindrospermopsis raciborskii (cyanobacteria) on the swimming behavior of Daphnia (cladocera)

“…Although this hypothesis has been mainly directed toward microcystins and much of the research to date has been dedicated to this toxin, some evidence also points to strong grazerimpairing effects of other toxins, such as STX [15,16]. The aim of the present study was to test the hypothesis that natural water samples containing different classes of cyanotoxins as well as an STX-producing strain of C. raciborskii, isolated from the same reservoir, affect the swimming activity of 2 Daphnia species: D. pulex and D. similis, both previously known to be sensitive to STX-producing C. raciborskii strains [15,16,35]. To test this hypothesis, we used 2 approaches: 1) acute toxicity bioassays specially designed to detect the effects of neurotoxins [16], and 2) behavioral assays using an automated movement tracking system, which is able to track and measure continuously the swimming activity parameters of Daphnia.…”

Effects of Cylindrospermopsis raciborskii strains (Woloszynska, 1912) Senayya & Subba Raju on the mobility of Daphnia laevis (Cladocera, Daphniidae)

“…According to Kaebernick and Neilan (2001) Saxitoxins are also known as paralytic shellfish toxins (PSTs) or poisons (PSPs) (Zagatto et al, 2012). These alkaloids are a group of neurotoxin carbamates that inhibit the propagation of nerve impulses in mammals through the blockage of sodium channels, which causes neuromuscular paralysis (Chorus and Bartram, 1999).…”

Acute Effects of a Cylindrospermopsis Raciborskii (Cyanobacteria) Strain on Mouse, Daphnia and Fish

“…In acute tests with strain CYRF-01 (non-published data), D. rerio was not sensitive to concentrations as high as 5×10 5 cells ml -1 of intact cells and to 100 mg l -1 of lyophilized cell extracts. Zagatto et al [37], on the other hand, showed that D. rerio fish larvae were senstitive to two other STXs-producer strains of C. racibosrskii in chronic exposures (7 days). Therefore, these data show that fish larvae seem to be more sensitive to toxins produced by C. raciborskii than adult fish.…”