Stage-dependent toxicity of bisphenol a on Rhinella arenarum (anura, bufonidae) embryos and larvae.

The acute and chronic toxicity of bisphenol A (BPA) was evaluated on the common South American toad Rhinella arenarum embryos and larvae by means of continuous and pulse exposure treatments. Embryos were treated continuously from early blastula (S.4) up to complete operculum (S.25), during early larval stages and by means of 24 h pulse exposures of BPA in concentrations ranging between 1.25 and 40 mg L(-1) , in order to evaluate the susceptibility to this compound in different developmental stages. For lethal effects, S.25 was the most sensitive and gastrula was the most resistant to BPA. The Teratogenic Index for neurula, the most sensitive embryonic stage for sublethal effects was 4.7. The main morphological alterations during early stages were: delayed or arrested development, reduced body size, persistent yolk plug, microcephaly, axial/tail flexures, edemas, blisters, waving fin, underdeveloped gills, mouth malformations, and cellular dissociation. BPA caused a remarkable narcotic effect from gill circulation stage (S.20) onwards in all the organisms exposed after 3 h of treatment with 10 mg L(-1) BPA. After recovering, the embryos exhibited scarce response to stimuli, erratic or circular swimming, and spasmodic contractions from 5 mg L(-1) onwards. Our results highlight the lethal and sublethal effectsof BPA on R. arenarum embryos and larvae, in the last case both at structural and functional levels.

Toxicity of endosulfan on embryo-larval development of the South American toad Rhinella arenarum.

Endosulfan is a widely used pesticide despite its extreme toxicity to a variety of taxa and its worldwide ban. The aim of the present study was to evaluate the acute and chronic toxicity of endosulfan on the embryonic-larval development of the common South American toad Rhinella arenarum. The results showed that lethal and sublethal effects increased with concentration and exposure time. The sensitivity to endosulfan increased during the larval period, the complete operculum stage (S.25) being the most sensitive (504-h median lethal concentration [LC50] = 0.01 mg endosulfan/L; 10% lethal concentration [LC10] = 0.004 mg endosulfan/L). Endosulfan exposure caused morphological abnormalities such as general underdevelopment, edema, gill malformations, and cellular dissociation as well as neurotoxicity. Our results also showed that larvae exposed to concentrations of 0.005 mg endosulfan/L and 0.01 mg endosulfan/L completed metamorphosis earlier than controls, but with underdevelopment. The 240-h teratogenic index was 6.13, implying a high risk for embryos to be malformed in the absence of significant embryonic lethality. Because the hazard quotients for chronic exposure were over 1, the level of concern value and toxicity endpoints obtained in the present study for R. arenarum occurred at concentrations lower than the levels of endosulfan reported in the environment, this pesticide should be considered a potential risk for this species.

Deformación de branquias en salmónidos: análisis macroscópico, histológico, ultraestructural y de elementos / Gill deformation in salmonids: macroscopic, histological, ultrastructural and elements analysis

Las branquias son los órganos destinados al proceso de respiración en los peces, estas están consideradas, entre las estructuras más delicadas del cuerpo de los teleósteos ya que están expuestas a sufrir daños de cualquier agente irritante, los cuales constituyen la causa más frecuente y significativa de sus cambios patológicos. Los objetivos del presente estudio son caracterizar las alteraciones branquiales desde los puntos de vista anatómico, histológico, además, determinar niveles de Ca, P y Zn del tejido óseo de la columna vertebral y cráneo de salmones afectados. Se utilizaron 47 salmones, divididos en dos grupos: control y con deformaciones, a los cuales se les realizaron análisis macroscópico, histológico, ultraestructural y de elementos. Se observaron alteraciones tanto en el contexto anatómico como histológico, así como gran presencia de bacterias y hongos que afectaban principalmente al primer arco, pudiendo concluir que los peces tendrían una susceptibilidad génica a la deformación branquial.

Gills act as the respiratory organ in the respiration process in fish. They are considered among the most delicate body structures of teleost fish as they are subject to damage from any irritant, which are the most frequent and significant causes of their pathological changes. The objective of this study is to characterize gill alterations from the anatomical and histological standpoint, and to determine levels of Ca, P and Zn in bone tissue of the spine and skull of affected salmon. For purposes of this study 47 salmon were used in two groups: control and deformation, subjected to complete histological, ultrastructural and element inspection. Abnormalities were observed in both the anatomical and histological context and extensive presence of bacteria and fungi affecting mainly the first arc were found. Therefore, we can conclude that these fish have a genetic susceptibility to gill deformation.

Toxic effect of the harmful dinoflagellate Cochlodinium polykrikoides on the spotted rose snapper Lutjanus guttatus.

The dinoflagellate Cochlodinium polykrikoides isolated from Bahía de La Paz, Gulf of California, showed an important short-term toxic effect on the spotted rose snapper Lutjanus guttatus. This microalga was able to decrease fish liver catalase activity and lipid peroxidation. Fish exposed to live dinoflagellates developed an abnormal mucus secretion on the gills that was directly related to algal cell concentration. Hepatic catalase inhibition and an increase in mucus secretion on the gills occurred when fish were exposed to 2 x 10(6) cells L(-1) of C. polykrikoides. Lipid peroxidation was significantly different at 4 x 10(6) cells L(-1) and the hepatosomatic index decreased at 3 x 10(6) cells L(-1). Our results suggest that oxidative stress contributes, at least in part, to the ichthyotoxic effect of C. polykrikoides from the Gulf of California.

Zinc protection against delayed development produced by cadmium.

The protective effect of zinc against slight teratogenical action, exerted by low cadmium concentrations, was evaluated in Bufo arenarum embryos treated simultaneously with both cations or preincubated with Zn before Cd treatment. Data on survival, malformations, and delay in development pointed out that Zn could prevent the deleterious effects of Cd in previous and simultaneous treatments with that heavy metal.

Experimental studies on a mutant gene (p) causing premature death of Ambystoma mexicanum embryos.

The premature death (p) mutation is a recessive lethal, which, in the homozygous condition, gives rise to a complex of abnormalities. The mutant embryos develop only to stage 37, at which time disintegration of superficial tissue begins. Many of the abnormalities observed in sections of the stage-37 mutant embryo are related to its failure to establish a functioning circulatory system, or to the resulting edema and/or ascites that distend the abdomen and flanks. There are, however, abnormalities of heart, liver, gill and muscle development which cannot be attributed to lack of circulation and edema. All of these abnormalities can be indirectly related to the endoderm, particularly the anterior and dorsal endoderm. The findings, therefore, suggest that the mutation leads to a fairly general defect of the endoderm.