Isolation and characterization of potentially toxic or harmful cyanobacteria from Oaxaca and Chiapas, Mexico

Abstract

The toxic effects of 7 coastal cyanobacterial strains isolated from Oaxaca and Chiapas, Mexico were evaluated. Growth was determined by dry weight. Toxicity bioassays were done in Artemia sp., juvenile white shrimp Litopenaeus vannamei and mice Mus musculus (ICR strain). In shrimp, three feeding methods were implemented: cyanobacterial biomass plus commercial food, cyanobacteria only, and biomass at different concentrations (18, 9, 4.5 and 2.2% w/v). In Artemia sp., Limnothrix amphigranulata (LIMA-3 strain) caused 100% mortality, and in the other organisms mortality was less than 30%. In the treatment L. vannamei with the food mix, mortality was less than 40%, but there was weight gain (6.2% ± 1.03). With the biomass concentration treatment, the highest and the least mortality were 66.7% with Limnothrix amphigranulata (LIMA-3) and 26.7% with L. majuscula—all groups lost weight (3–5%). The last experiment showed no mortality. Shrimps showed gill damage evidenced by color changes and filament accumulation. Mouse bioassays exhibited 100% mortality with LIMA-3 extracts at every concentration (LD₅₀ 150 mg kg^{− 1}, i.p. mouse). Necropsies showed hemorrhage and increases in liver weight, indicating hepatotoxin. LIMA-3 strain was considered a medium-toxicity cyanobacteria. Weight-loss in L. vannamei could indicate the presence of a toxin. Therefore, a critical examination of the toxicity role in overall cyanobacteria ecotoxicology is needed.

Keywords:

• Cyanobacteria
• subacute and acute toxicity
• shrimps
• mouse biossay

Acknowledgments

We thank Arturo Sierra-Beltrán (Centro de Investigaciones Biológicas del Noroeste, La Paz, BCS.) for reviewing the manuscript, Antonio Pineda-Alcázar (Laboratorio Estatal de Salud Pública, Chiapas) for assistance in mouse bioassay, Rosalía Cartas Martínez (Instituto Tecnológico de Salina Cruz, Oaxaca) for shrimp analyses, Ocean. Pablo A. Pintos Terán (UMAR) for shrimp donated, as well as the members of the Laboratory of Microalgae Biotechnology at UMAR for their technical assistance, Diana Dorantes for English editing. This research was partially supported by the PROMEP Program and UMAR Project (2II0004), Oaxaca, Mexico.

Notes

*Synechococcus elongatus (SYNE-3), Oscillatoria sp. (BAOs-3), Oscillatoria limnetica (OSCIL-3), Limnothrix amphigranulata (LIMA-3, MLCH-3), Spirulina sp. (BASp-3), Lyngbya majuscula (LYNM-3).

*Values are expressed as the percentage average for each of the strains (n = 10 in Artemia, n = 6 for shrimps juveniles). Control = fed with D. salina (for Artemia bioassay), commercial food (for juvenile shrimp subacute and acute bioassays). w v^{− 1} = weight volume. GSR = Growth specific rate. CF+CB = Commercial food plus cyanobacteria biomass, CB = cyanobacteria biomass, CBC = cyanobacteria biomass concentrations.