EFECTO TÓXICO DE CEPAS DE Chattonella spp. (RAPHIDOPHYCEAE) SOBRE LAS FASES INICIALES DE VIDA DE Paralabrax maculatofasciatus (TELEOSTEI: SERRANIDAE) Y Litopenaeus vannamei (DECAPODA: PENAEIDAE)

Abstract

ABSTRACT Raphidophyceans have been linked to the production of brevetoxins (PbTx), reactive oxygen species (ROS) and polyunsaturated fatty acids (PUFA), causing fish mortalities mainly in adults, although its potential impact on early stages of fish and crustaceans is not known. In this study we determined the effect of various strains of Chattonella in the Gulf of California on Paralabrax maculatofasciatus embryos and Litopenaeus vannamei nauplii. Chattonella strains were characterized (cell density, growth rate, size and profile of pigments). We determined the presence of PbTx, ROS and fatty acid profile. Embryos of P. maculatofasciatus on segmentation stage (SS) were placed (1 embryo/well) in polystyrene microdilution plates. We added 1 ml per plate of different cell concentrations (CC) (2 to 10·103 cell·ml-1) of Chattonella subsalsa (CSNAV-1), C. marina var. ovata (CMOPAZ-1), C. marina var. marina (CSPV-3 and CSCV-1), sterile seawater f/2 and the dinoflagellate (nontoxic) Prorocentrum micans as controls, culminating in apterolarva phase. nauplii on stage 2 of L. vannamei were placed (1 nauplii/well). We added 1 ml per plate of different CC (0.5 to 6·103 cell·ml-1) of C. subsalsa, C. marina var. marina (CSPV-3, and CSCV CSJV-2-1), C. marina var. ovata (CMOPAZ-1, -2 and -3), as well as the diatom Chaetoceros calcitrans and the chlorophycean Tetraselmis suecica as controls, culminating in the zoea 3 stage. Embryos and nauplii were incubated in triplicate at 23° C. Chattonella strains showed a size range of 33.7-90 μm and 18.5-41.7 μm of long and wide, respectively, cell density of 3.17-4.59·103 cell·ml-1 and growth rate from 0.21 to 0.35 div·day-1. The pigments are characteristic of raphidophyceans, all strains produce ROS, was not detected the presence of PbTx and presented a characteristic profile of fatty acids. In P. maculatofasciatus, Chattonella strains cause different mortality rates on the early stages of development being the most sensitive on SS with 98% mortality with C. subsalsa. The strain of C. marina var. ovata (CMOPAZ-1) at low concentrations caused mortality in embryos with an LC50 of 1.73·103 cell·ml-1, while C. subsalsa caused high mortalities in short time with a LT50 of 20 h. Strains of C. marina var. ovata followed by C. marina var. marina (CSPV-3) showed the highest mortality, which increased gradually with the cell concentration (2, 4, 6 and 8·103 cell·ml-1. In L. vannamei the effect of the various strains of Chattonella at different concentrations in the nauplii stage is harmless. In all treatment we observed effects in mortality from the beginning of the zoea on phase 1, just at the beginning of exogenous feeding. The highest mortality (100%) of L. vannamei in less time (120 h) was caused by the strains of C. marina var. ovata CMOPAZ-2 and -3 at concentrations of 3·103 cell·ml-1, with a LT50 of 3 day and 19 h. These results show a differential effect between the various strains of Chattonella and their concentrations to be supply to embryos of P. maculatofasciatus and nauplii of L. vannamei, with different effects in each group of organisms.