Chronic histopathological effects of parathion and 2,4-D on female gonads of Chasmagnathus granulata (Decapoda, Brachyura).

Female crabs of Chasmagnathus granulata, sampled at the external zone of the Rio de la Plata estuary, were chronically exposed to the pesticides parathion and 2,4-D, both of which have been extensively applied to crops in Argentina for a decade and have been detected several times above permissible levels in the estuary. After 2 months of female exposure to the pesticides during the reproductive season, the crabs' ovaries were dissected and fixed in Bouin's solution, to assess the possible effects of pesticides at the histological level. Parathion caused a significant increase in both previtellogenic and vitellogenic oocyte size, as well as a loss of the normal spherical shape of the oocytes. With 2,4-D, a significant decrease in vitellogenic oocyte size was noted, whereas the number of atretic follicles increased as a result of exposure to this herbicide. Several hypothetical mechanisms of action of these pesticides are discussed in relation to the effects observed. Although assayed concentrations were relatively high with respect to mean values detected in the mentioned estuary and its influents, persistent peaks may occur, especially in sediments. This work suggests a high potential risk from the pesticides studied to the reproductive performance of local aquatic fauna.