Efectos letales y subletales de plaguicidas y metales pesados en cangrejos de estuario. Revisión de una década de investigaciones

RODRÍGUEZ, ENRIQUE M.; MONSERRAT, J.M.; MEDESANI, DANIEL A.; BIGI, R.; RODRÍGUEZ MORENO, P.A.; LÓPEZ, L.; STELLA, V.S.; CERVINO, C.O.; ANSALDO, M.

Nueva Serie

MACN

Año: 1998 p. 1 - 17

0325-1845

Lethal and sublethal effects of pesticides (parathion and 2,4-D) and heavy metals (cadmium), have been evaluated during a decade in esturine crabs, mainly in the species Chasmagnathus granulata (Decapoda, Brachyura, Grapsidae). Adult crabs showed to be more resistant than other crustaceans species to the assayed pollutants, being able to accumulate them; therefore, crabs preyed by fish could be involved in biomagnification processes. On the other hand, larvae (zoea  I) of C. granulata showed to be very sensitive to parathion and 2,4-D. Safe concentrations of 0.004 ug/l and 0.003 mg/l are respectively proposed, from the larvae CL50 values and considering an application factor of 0.01.  Methyl-parathion inhibited in vitro the acetylcholinesterase of C. ganulata adults, although at higher doses than those reported for other species. The anti-cholinesterase effect of parathion could be explaining several in vivo sublethal effects of the insecticide, such as higher oocyte size during maturation (under neuroendocrine control) and a relative high incidence of eye malformation in larvae hatched from exposed eggs. Parathion also produced necrosis in gill epithelium and a susequente hypercapnic and lacticidemic response, which would be the cause of the plasmatic acidosis observed. As for 2,4-D, a very much lower, lethal toxicity than parathion has been observed. The typical uncoupler action described for 2,4-D was consistent with the changes caused by the herbicide to the metabolic rate and with the significant reduction noted in the oocyte size during the reproductive period. Besides, 2,4-D showed to exert sublethal effects within a very wide concentration range: this fact probably was related to the high incidence of all the abnormaliites observed in larvae pre-exposed during embryonic development. Cadmium was able to inhibit in vitro the Na+/K+ ATPase in gills and both in vivo and in vitro the carbonic anhydrase in the same tissue. Several imbalances of ions regulation at dilute salinities, as well as the cadmium effect on calcium resorption and deposition during the molting cycle. Concerning reproductive events, cadmium  produced, in a specific manner, hyperpigmentation on pre-exposed larvae. This later result could be useful for a monitoring program about cadmium or heavy metal pollution.