Imposex Development Research Articles

Imposex in Stramonita haemastoma: a preliminary comparison between waterborne and dietborne exposure

400 adult individuals of the Stramonita haemastoma were collected from a pristine beach in Ceara State, Brazil. These organisms were transplanted into a marina with intense shipping activities and were fed weekly with oysters obtained from the same beach from which they were collected, being exposed only to the bioavailable organotins in the environment, without accounting for diet (waterborne exposure). 30 individuals were analyzed every 2 weeks after transplantation to investigate the development of imposex. After 15 days, 90% of the females had developed imposex (VDSI I-III, RPLI 3.22), with 100% of the females developing imposex after 30 days; at the end of the experiment, the VDSI levels ranged between I-V. These results were compared with those of a previously published study performed simultaneously in which gastropods obtained in same area were fed in the laboratory with oysters from the same marina in which the gastropods were transplanted (dietborne exposure). Despite the higher levels obtained through exposure via water at the end of 90 days, both exposure routes induced imposex in 100% of the females of the S. haemastoma. However, aqueous exposure induced higher levels, possibly due to the constant contact between the organisms and contaminants.

Neurotoxicity and Oxidative Damage Induced from Exposure of Male Rats to Low doses of the Synthetic Environmental Contaminant Tributyltin

Tributyltin chloride (TBT) is an organotin compound widely used in several high biocides for agro-industrial applications, such as fungicides, and marine antifouling paints leading to endocrine disrupting actions, such as imposex development in mollusks. The current study investigates DNA damage, changes in brain drug-metabolizing enzymes, lipid profile, and oxidative damage of TBT at low doses 10, 100, 250, 500, 1000, and 2000 μg/kg B.W. in male rats. The animals were divided into eight equal groups which treated daily by oral gavage for 45 days. Administration of TBT induced a dose-dependent increase in the DNA damage and TBARS. Also, it decreases the expression of the regulator of the antioxidant response (the levels of glutathione and the activities of GR, GPX, CAT, and SOD). TBT did not show any significant effect of brain drug-metabolizing enzymes (cytochrome b5 and cytochrome p450). TBT at 250, 500, 1000, and 2000 μg/kg B.W. showed significant increase in lipid profile (total cholesterol, triglyceride, and LDL), but HDL showed significant decrease. In conclusion, the obtained results provide evidence that exposure to TBT at low doses causes oxidative stress, DNA damage, and changes in biochemical parameters in a dose dependent manner.

Marine Pollutant Tributyltin Affects DNA Methylation and Fitness of Banded Murex (Hexaplex trunculus) Populations

Banded murex, Hexaplex trunculus, is a marine gastropod whose reproductive fitness can be severely affected by very low concentrations of antifouling compound tributyltin (TBT). TBT has strong xenoandrogen impacts on snails, causing the development of imposex (e.g., the superimposition of male sexual characteristic in females), thereby affecting the fitness of entire populations. TBT is also known as a DNA-demethylating agent and an obesogenic factor. The aim of this study was to unravel the interactions between TBT bioaccumulation, phenotypic responses, and epigenetic and genetic endpoints in native populations of H. trunculus. Seven populations inhabiting environments along the pollution gradient were sampled in the coastal eastern Adriatic. These included sites of intense marine traffic and boat maintenance activity and sites with low anthropogenic impact. Populations inhabiting intermediately and highly polluted sites exhibited higher TBT burdens, higher incidences of imposex, and higher wet masses of snails than populations in lowly polluted sites. Other morphometric traits and cellular biomarker responses did not show clear differentiation among populations in relation to marine traffic/pollution intensity. An analysis of methylation sensitive amplification polymorphism (MSAP) revealed environmentally driven population differentiation and higher epigenetics than genetic within-population diversity. Moreover, decreases in genome-wide DNA methylation coincided with the imposex level and snail mass, suggesting an epigenetic background of the animal phenotypic response.

Evaluation of the effects produced by subacute tributyltin administration on vascular reactivity of male wistar rats

Tributyltin chloride (TBT) is an organotin compound widely used in several high biocides for agroindustrial applications, such as fungicides, and marine antifouling paints leading to endocrine disrupting actions, such as imposex development in mollusks. In female rats, TBT has been shown to promote ovarian dysfunction, reduction of estrogen protective effect in the vascular morphophysiology, at least in part by oxidative stress consequences. Estrogen causes coronary endothelium-dependent and independent vasodilation. However, the TBT effects on cardiovascular system of male rats are not fully understood. The aim of this study was to evaluate the effects of subacute TBT exposure in aorta vascular reactivity from male wistar rats. Rats were randomly divided into three groups: control (C), TBT 500 ng/kg/day and TBT 1000 ng/kg/day. TBT was administered daily for 30 days by oral gavage. We found that TBT exposure enhanced testosterone serum levels and it was also observed obesogenic properties. TBT exposure evoked an increase in endothelium-dependent and independent phenylephrine-induced contraction, associated to an inhibition in eNOS activity. On the other hand, it was observed an enhancement of iNOS and NF-kB protein expression. We also observed an increase in oxidative stress parameters, such as superoxide dismutase (SOD) and catalase expression, and also an increase in malondialdehyde production. Finally, TBT exposure produced aortic intima-media thickness. Taken together, these data suggest a potential cardiovascular toxicological effect after subacute TBT exposure in male rats.

Insights into the Influence of Natural Retinoic Acids on Imposex Induction in Female Marine Gastropods in the Coastal Environment

Conventionally, development of imposex, i.e., superimposition of male sexual characteristics on females, in marine neogastropods has been solely linked to exposure to synthetic organotin compounds, such as triphenyltin (TPT), in the marine environment. Here, our experimental results show that marine cyanobacteria can produce retinoic acids (RAs) and their oxidative metabolites 4-oxo-RAs, and the most commonly distributed RA, i.e., all-trans-RA, can also trigger expression of genes related to imposex in female whelks Reishia clavigera after chronic exposure of 60 days. Both estimated concentrations of TPT and RAs and 4-oxo-RAs in seawater are positively associated with the Vas Deferens Sequence Index (VDSI) in female whelks collected from various sites along the coast of Hong Kong; the concentration of TPT explains 28% of the total variation of VDSI, while the total concentrations of RAs and 4-oxo-RAs contributed to 14% of the variation based on separate regression analyses. Our discoveries have implications on the cause and magnitude of imposex in marine neogastropods, calling for more research in ecotoxicology of natural RAs and 4-oxo-RAs in the marine environment in the future.

RXR Expression in Marine Gastropods with Different Sensitivity to Imposex Development

The superposition of male sexual characteristics in female marine gastropods (imposex) represents one of the clearest ecological examples of organotin-mediated endocrine disruption. Recent evidences suggest that signaling pathways mediated by members of the nuclear receptor superfamily, RXR and PPARγ, are involved in the development of this pseudohermaphroditic condition. Here, we identified significant differences in RXR expression in two caenogastropod species from Nuevo Gulf, Argentina, Buccinanops globulosus and Trophon geversianus, which present clear contrast in imposex incidence. In addition, B. globulosus males from a polluted and an unpolluted area showed differences in RXR expression. Conversely, PPARγ levels were similar between both analyzed species. These findings indicate specie-specific RXR and PPARγ expression, suggesting a major role of RXR in the induction of imposex.

Imposex responses in Thaisella chocolata and Xanthochorus buxeus from Callao harbor, Peru

Imposex responses were comparatively assessed in Thaisella chocolata and Xanthochorus buxeus, in sites previously studied regarding TBT contamination and under the influence of various levels of ship/boat activities in a coastal zone of Peru. In August 2015, at least 60 adult specimens of both T. chocolata and X. buxeus were simultaneously sampled by SCUBA diving in three subtidal sites. A total of 545 adult specimens of T. chocolata and X. buxeus were analyzed in the present study. Imposex incidence (I%) was detected in the two muricid species in the sampled site closest of Callao harbor — P1 (T. chocolata and X. buxeus = 100%) and also in the P2 (T. chocolata = 100% and X. buxeus = 81%). On the other hand, as expected, no sign of imposex was observed in organisms obtained from P3. Thaisella chocolata is likely to be the most sensitive species to imposex development, followed by X. buxeus. Thus, T. chocolata is the most suitable species to be used as a sentinel of TBT contamination due to its high sensitivity and better discrimination of levels among different sites.

Characterization and comparison of transcriptional activities of the retinoid X receptors by various organotin compounds in three prosobranch gastropods; Thais clavigera, Nucella lapillus and Babylonia japonica

Two cDNAs of RXR were isolated, for the first time, from the ivory shell, Babylonia japonica, and the transcriptional activities were tested in vitro to compare with other gastropod (Thais clavigera and Nucella lapillus) RXR isoforms. The transcriptional activities of all of these RXR isoforms were significantly induced by mammalian RXR agonist, 9-cis retinoic acid (9cRA). The transcriptional activity of T. clavigera RXR-1 was also examined by using 9cRA and 16 organotin compounds, and significant ligand-dependent transactivations were observed by 9cRA and 5 organotins (tributyltin (TBT), tetrabutyltin (TeBT), tripropyltin (TPrT), tricyclohexyltin (TcHT) and triphenyltin (TPhT)). These 5 organotins also induced significant transcriptional activities in N. lapillus and B. japonica RXR isoforms. These 4 organotins, except for TeBT, have been reported to promote the development of imposex after a month of a single injection each, using female T. clavigera. To investigate the function of gastropod RXR isoforms, the effects of mammalian specific pan-agonist, PA024, and pan-antagonist, HX531, were examined, and significant induction of transcriptional activity by PA024 was demonstrated in these gastropod RXR isoforms. The additions of HX531 significantly suppressed the transcriptional activities of these gastropod RXR isoforms by 9cRA and 5 organotins. Using the mammalian two retinoic acid response elements, the transcriptional activities by 2 agonists, 9cRA and PA024, were different among the RXR isoforms of each gastropod species. With retinoid X response element (RXRE), transcriptional activities of TcRXR-1, BjRXR-1, and NlRXRa were significantly higher than those of TcRXR-2, BjRXR-2, and NlRXRb. Transcriptional activities of TcRXR-2, BjRXR-2, and NlRXRb, however, were significantly higher than those of TcRXR-1, BjRXR-1, and NlRXRa with thyroid hormone response element, TREpal. Thus, induction of imposex in prosobranch gastropods is strongly suggested to be triggered by 9cRA and certain organotins, such as TBT and TPhT through the activation of RXRs. These gastropod RXRs might control the different gene transcription by forming homo- or heterodimer complex with their own isoforms. These findings will contribute to our understanding of the fundamentals of the endocrine system in molluscs, particularly on RXR signaling pathway.

Imposex status associated with organotin contamination in Reishia clavigera after reciprocal transplantation between clean and polluted sites in Hong Kong

Recent biomonitoring studies have showed that contaminations of triphenyltin (TPT), relative to levels of tributyltin, have become more serious in Hong Kong and other South China coasts. However, there is a lack of field-based evidence to demonstrate the casual relationship between TPT and imposex development in the rock shell Reishia clavigera in this region. This study aimed to investigate the temporal changes of imposex development and tissue concentration of six organotins (OTs) in tissues of R. clavigera after their reciprocal transplantation between relatively clean and polluted sites in Hong Kong for six months. The results revealed a significant increase of tissue concentration of total OTs, in particular TPT, in the rock shells transplanted from a clean site to a polluted site, while a decrease of tissue OT concentrations was observed in those treated conversely. Vas Deferens Sequence Index, one of the imposex indices, only increased slightly for rock shells transplanted from clean to polluted sites, while Relative Penis Size Index elevated remarkably for the same treatments. In general, the rock shells had lower tissue concentrations of OTs in winter than that in summer, though the exact mechanism is still unknown. This study has further confirmed that OT contamination is still prevalent in Hong Kong’s coastal marine waters, which necessitates tightened management controls on this group of chemicals especially on TPT compounds.

De novo transcriptome assembly of the marine gastropod Reishia clavigera for supporting toxic mechanism studies

The intertidal whelk Reishia clavigera is commonly used as a biomonitor of chemical contamination in the marine environment along Western Pacific region, and as a model for mechanistic studies of organotin-mediated imposex development. However, limited genomic resources of R. clavigera have restricted its role for the investigation of molecular mechanisms of such endocrine disruptions. This study, therefore, aimed to establish tissue-specific transcriptomes of the digestive gland, gonad, head ganglia, penis and the remaining body part of the male and female R. clavigera. By combining the results, a global transcriptome was obtained. A total of 578,134,720 high-quality filtered reads were obtained using Illumina sequencing. The R. clavigera transcriptome comprised of 38,466 transcripts and 32,798 unigenes with predicted open reading frames. The average length of transcripts was 1,709bp with N50 of 2,236bp. Based on sequence similarity searches against public databases, 28,657 transcripts and 24,403 unigenes had at least one BLAST hit. There were 17,530 transcripts and 14,897 unigenes annotated with at least one Gene Ontology (GO) term. Moreover, 5,776 transcripts and 5,137 unigenes were associated with 333 Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathways. The numbers of unigenes were similar among the five target tissues and between sexes, but tissue-specific expression profiles were revealed by multivariate analyses. Based on the functional annotation, putative steroid hormone-associated unigenes were identified. In particular, we highlighted the presence of steroid hormone receptor homologues that could be the targets for mechanistic studies of the organotin-mediated imposex development in marine gastropods. This newly generated transcriptome assembly of R. clavigera provides a valuable molecular resource for ecotoxicological and environmental genomic studies.

Triphenyltin induces imposex in Nucella lapillus through an aphallic route

Triphenyltin (TPT) was used until recently as a biocide in antifouling systems and nowadays is still applied as an agriculture pesticide in some countries. This compound is known to cause imposex (the imposition of male characters in females of gastropod molluscs) in a very limited number of species, when compared with tributyltin (TBT), the universally recognized imposex-causing agent. In this study, we tested if TPT could induce imposex in females of the dog-whelk Nucella lapillus. Experimental groups of 40 females were injected with a volume of 2μL/g of soft tissue wet weight (ww) of one of the following treatments, using DMSO as a solvent carrier: DMSO (solvent control); 1μg/g ww of TBT (positive control); 0.2, 1 and 5μg/g ww of TPT and a non-injected group (negative control). Concentrations were confirmed in the organism tissues by means of chemical analyses of a pool of 10 specimens at T0 and then after the imposex analysis at T56days. After 8-week trial, results pointed out statistically significant differences between treatments, with both TPT and TBT positively inducing imposex. However, imposex development in TPT-injected females differed from that of TBT, since females that developed imposex presented an aphallic condition (no penis development) while the TBT-treated females developed standard imposex (with penis formation). These results suggest that TPT and TBT act differently in the sequential process of female masculinization, casting new insights about the hypothetical pathways underlying imposex development.

Imposex in Nassarius nitidus (Jeffreys, 1867) as a possible investigative tool to monitor butyltin contamination according to the Water Framework Directive: A case study in the Venice Lagoon (Italy)

Butyltin (TBT, DBT, and MBT) effects on molluscs, especially endocrine disruption in bivalves and gastropods, have been widely investigated. Imposex, the superimposition of male characters onto female gonochoristic Caenogastropods, is the most studied biological effect of TBT. TBT compounds are among the priority hazardous substances within Directives 2000/60/EC (WFD) and 2008/105/EC. The Environmental Quality Standards (EQSs) set by the WFD for TBT are quite difficult to quantify by means of chemical analysis, without the use of expensive and high performance methods. Assuming that EQSs set for TBT were derived from evidence of imposex development at very low concentrations, this specific biomarker could be used as an indirect measure of assessing levels of bioavailable BTs. Therefore, this study aims to validate the use of imposex development as an investigative tool to monitor the bioavailable fraction of BTs within the WFD, by comparing imposex levels and BT concentrations in Nassarius nitidus from the Venice Lagoon.BT concentrations and imposex levels in N. nitidus, collected in 2013, had decreased when compared to previous studies in the same area. Both VDSI and RPLI correlated positively with BT body burden in females, confirming that imposex is a valid tool to monitor bioavailable BTs. However, TBT is still a matter of concern in the Venice Lagoon, as TBT concentrations were still higher than its degradation products suggesting recent fresh TBT inputs in the studied area. To propose imposex levels as an indicator of the impact of BTs within the WFD, classification class boundaries and Ecological Quality Ratios were introduced.As a preliminary attempt, imposex levels were also compared to the OSPAR Commission EcoQOs which linked imposex levels in Nassarius reticulatus with TBT concentrations in water. Based on this comparison the degree of imposex development in the Venice Lagoon suggested that TBT concentrations in water should be over the EQS-AA concentration and, at one site, also over the EQS-MAC.From all the results obtained in this work, it appears that imposex evaluation in N. reticulatus could give information about the ecological status regarding BT compounds under the WFD and also be used to monitor their effects and support chemical analyses until more sensitive methods become available.

Shell shape as indicator of pollution in marine gastropods affected by imposex

Tributyltin (TBT) and other pollutants are present in Patagonia, and are associated with maritime traffic and human activities. Cause–effect relationship between TBT and imposex development in females of marine gastropods is well documented. We tested whether the imposex incidence associated with TBT pollution is related to detectable shell-shape variations in the edible marine snail (Buccinanops globulosus). We compared shell shape of B. globulosus in six contiguous sites on a gradient of imposex and maritime traffic, by using geometric morphometric analysis. Our results indicated that the registered differences in shell shape are associated to imposex incidence in the harbour zone where previous works have detected TBT pollution. Gastropods from areas of high maritime traffic presented a rounded shell with a shorter spire, and a smaller relative size of the shell aperture, whereas the opposite shape (fusiform shape, elongated-spired shell and bigger relative size of the shell aperture) occurred in gastropod shells from areas of low maritime traffic. Shell variation registered here could be useful to detect TBT pollution in populations of B. globulosus and another neogastropod species.

The effect of size and epibiotic barnacles on imposex in Stramonita haemastoma collected from the northern coast of Tunisia

Imposex was quantified in Stramonita haemastoma from the Bizerta Channel during a one-year study period and the effect of gastropod size and shell fouling by epibiotic barnacles investigated. Butyltin concentrations (tributyltin (TBT) and its derivatives di- and mono-butyltin) were also investigated in the soft tissue of the gastropods to depict temporal trends in pollution. Kelibia Beach was chosen as a reference site (not polluted by organotin) to depict whether barnacle fouling could intervene in imposex development. Imposex incidence in the Bizerta Channel was greater in females fouled by epibiotic barnacles compared to non-fouled females. Considering the size of the gastropods, large females (fouled and non-fouled) always exhibit higher imposex indices than smaller females. The concentrations of organotin compounds were found to be similar in the studied species, independent of sex or fouling condition. For Kelibia Beach, no imposex was recorded in fouled and non-fouled snails, while butyltins were below the limit of detection. Results gathered in the present study confirm the effect of size and epibiotic barnacles as factors affecting imposex quantification in gastropods. The absence of imposex for Kelibia Beach suggests that barnacles do not promote the development of imposex, but could be a secondary factor amplifying the effect of imposex. Furthermore, this investigation showed a significant decrease in imposex and TBT levels in the Bizerta Channel as compared to previous work, reflecting the effectiveness of a TBT ban on a global scale.

Differential organotin sensitivity in two Leucozonia species from a ship traffic area in southeastern Brazil

Tributyltin exposure is the primary cause of imposex development in gastropods, making them excellent bioindicators. The present research represents the first examination of butyltin (BT) contamination in surface sediments associated with imposex in Leucozonia nassa and L. ocellata in a harbour complex area in Espírito Santo, southeastern Brazil. The objectives of this study were to evaluate the organotin pollution in the area and to assess the sensitivity of both species to BT pollution through imposex development. Specimens were collected between 2007 and 2010 and the sediments were sampled in 2007. Imposex intensity was evaluated based on the percentage of imposexed females, the relative penis length index (RPLI) and the average value of the vas deferens sequence index (VDSI). BTs were analysed using gas chromatography equipped with a pulsed flame photometric detector (PFPD). The results demonstrated the occurrence of elevated concentrations of BTs in the sediment ranging from 383.7 to 7172.9 ng Sn g−1, indicating a severe contamination of the area, which was confirmed by the biological monitoring results. Our findings also indicated that L. ocellata is a less sensitive species than L. nassa and that this differential sensitivity plays a key role in the distributions of the populations of both species in the studied area.

Variability of imposex development and reproductive alterations in the Patagonian gastropod Buccinanops globulosus inhabiting a polluted harbour area

El objetivo de este trabajo fue estudiar parametros reproductivos y desarrollo de imposex en el caenogasteropodo Buccinanops globulosus que habita en una zona portuaria de alto trafico maritimo y con presencia de contaminantes. Los resultados mostraron una mayor incidencia de imposex en hembras sin ovicapsulas que en hembras con ovicapsulas. Entre las hembras con imposex, el desarrollo del pene fue significativamente mayor en aquellas sin ovicapsulas (3.4 mm) que en las hembras con ovicapsulas (1.5 mm). En B. globulosus comunmente un solo juvenil eclosiona por cada capsula, sin embargo, en este estudio se registraron capsulas con multiples embriones. Todos estos resultados sugieren una relacion entre el desarrollo de imposex y alteraciones en los parametros reproductivos de las hembras de B. globulosus que habitan en sitios con condiciones ambientales adversas (area contaminada).

Development of reproductive organs in the ivory shell Babylonia japonica: Observations from wild populations and laboratory-reared juveniles

We histologically examined normal differentiation and development of genital tract and gonad in the ivory shell Babylonia japonica (Buccinidae) to determine whether the formation of male-type genitalia in imposex-exhibiting females mimics the normal development of male genitalia in prosobranch gastropods. We used a wild-caught 2-year-old specimen and laboratory-reared juveniles aged 0–24 months. Gonad differentiation was unclear before age 14 months, but progressed after 16 months. Both sexes had complete genital tract and mature gonad at 20 months. However, differentiation and development occurred earlier in females than in males. Development of genital tract preceded gonad differentiation. Vas deferens morphogenesis in males resembled that in imposex-exhibiting females. These findings help to understand the morphogenesis of genital tract and gonad in prosobranch gastropods and will contribute to more in-depth studies of the mode of action of organotin compounds such as TBT and TPhT in imposex development in female prosobranch gastropods.

Imposex development in Hexaplex trunculus (Gastropoda: Caenogastropoda) involves changes in the transcription levels of the retinoid X receptor (RXR)

In order to further demonstrate that TBT-induced imposex through RXR signaling is not species-specific, Hexaplex trunculus was selected as an experimental model species. We first isolated RXR in H. trunculus, and determined gene transcription through quantitative real-time PCR in key tissues (e.g., penis/penis-forming area and central nervous system:- CNS), upon exposure to tributyltin (TBT) (5 and 50ng TBTL−1). Two months of exposure to TBT induced imposex and led to a significant increase in the severity of the phenomenon in females and an increase in male penis lengths. Exposure to TBT altered RXR gene transcription in a tissue and sex-specific manner. In the CNS, there were no significant changes in RXR gene transcription between control and TBT-exposed females. A similar trend was observed in male CNS. On the contrary, in the penis-forming area/penis of females exposed to TBT, a significant increase in RXR gene transcription was observed in the 50ng TBTL−1 group. Furthermore, a positive correlation was observed between overall female penis lengths and RXR gene transcription. In males, although a trend towards an increase in RXR gene transcription in penis was observed, differences did not reach significance. Overall, the results of the present study give further support to a local role of RXR in the penis-forming area during the development of imposex by TBT, thus suggesting a conserved function of RXR in penis formation at least within prosobranch gastropods.

Is aphallic vas deferens development in females related to the distance from organotin sources? A study with Stramonita haemastoma

Imposex, a syndrome characterized by the appearance of a penis and/or vas deferens in female gastropods due the presence of organotins in environment, is still observed in Brazilian gastropod populations, as in other countries, even after the tributyltin (TBT) ban. Nevertheless, the progressive controls on the use of organotins in antifouling systems at national and international levels and the consequent reduction of their environmental concentrations have led to changes in the characteristics of imposex development observed in Stramonita haemastoma. Populations of this species were analyzed on the coast of Rio de Janeiro (Brazil) between 2007 and 2008, and the developmental pathways associated with the syndrome were identified. Compared with previous works, it was noted that imposex expression was reduced in most of Guanabara Bay. Aphallic imposex development, on the other hand, showed a marked increase. The pathways of imposex development were also evaluated in a temporal data series from a fixed sampling station at Vermelha beach, and the incidence of aphallic imposex development was found to show a marked increase from 1998 onward. Furthermore, the observation of either the presence or absence of a penis in imposex-affected females may indicate that penis development is related to the contaminant exposure level and that the decreasing TBT concentrations in the local environment result in the predominance of an aphallic route of imposex development. These findings support the idea that imposex female aphally in this species could be a dose-dependent response, rather than a genetic anomaly.

Transplant bioassay induces different imposex responses in two species of the genus Stramonita

A bioassay to study differential specific responses in imposex development due to marine organotin pollution was done by transplanting specimens of the gastropods Stramonita haemastoma and Stramonita rustica from an imposex-free area to a marina with high marine traffic inside a ship repair yard, a place where local populations of S. haemastoma were known to show high indices of imposex. Three hundred sexually mature, imposex-free specimens of each species were kept in cages for 120 days, and samples of 30 individuals were periodically analysed for imposex development. Shell length, penis length and vas deferens development were recorded and imposex development indices (% imposex, RPLI and VDSI) were calculated. Our results indicated that imposex induction in S. haemastoma is faster and more sensitive than in S. rustica. Imposex incidence in S. haemastoma could be a useful tool for monitoring marine pollution by organotin compounds in harbours along the Brazilian coast.