Imposex in three marine gastropod species in Chile and potential impact onmuriciculture

A survey of imposer was conducted between the Bay of San Vicente, Concepcio n, Chile (36 degrees 50') and the Bay of Renocavi, Puerto Montt, Chile (41 degrees 35'), to determine if imposer is occurring in an area of collection and cultivation of the gastropod, Chorus giganteus, Imposer was recorded i n three chilean muricids C.giganteus, Xanthochorus us cassidiformis and Nuc ella crassilabrum complex. Percentage of imposer in females sampled ranged from 0% to 100%, The degree of expression of imposer was not so severe as t o elicit sterility in the individuals surveyed. Incidence of imposer was as high as 47% in areas of harvest of C. giganteus for reproductive and culti vation studies for commercial production of this species. A six percent inc idence of imposer was observed in Nucella proximal to the facility for cult ivation of C. giganteus. Gastropods of the genus Nucella are used in other countries to monitor incidence of imposer and have demonstrated sensitivity toward tributyltin (TBT), the associated causal agent. Since sex of indivi duals in muriciculture is determined by the presence or absence of a penis, imposer may lead to erroneous classification of males and females. The inc idence and severity of imposer in C. giganteus and related species may have a negative impact on sustainable cultivation and harvest of gastropods in Chile. (C) 1999 Elsevier Science Ltd. All rights reserved.