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The prevalence and intensity of imposex and observations on the seasonal gametogenic cycle are reported for the Asian veined rapa whelk Rapana venosa (Valenciennes, 1846), an invader of the Chesapeake Bay on the North American Atlantic coast. Adult whelks from opportunistic col- lections by commercial fishermen demonstrated inactivity from mid-November through early March, copulation from February through mid-November, and egg-laying activity from late May through August. All imposex females examined did not have a functional vas deferens (below Stage 3 on the vas deferens scale of Gibbs et al. 1987; J Mar Biol Assoc UK 67:507-523) and were expected to func- tion normally in reproduction. Although a preponderance of imposex females over 'normal' females by a ratio exceeding 2:1 was observed in 4 out of 5 regions examined in lower Chesapeake Bay, there was no significant difference in the numbers of functional females (imposex females and normal females) observed in any region. Shell lengths and wet tissue weights (g) of both imposex females and males were approximately the same and sexual dimorphism was not apparent at the population level. However, true female rapa whelks had lower wet tissue weights than either imposex females or males. Individual rapa whelks did not appear to be food-limited in the Chesapeake Bay, and the described reproductive activity suggests continued invasion within Chesapeake Bay habitats.

We investigated the occurrence of imposex in gastropods from the coastal waters of mainland China from November 1999 to July 2004. Imposex was found in 30 species from 8 families, and was recorded in 20 species for the first time. In addition to the already known phenotypes of imposex expression in Cantharus cecillei, we also found aborted egg capsules in specimens with a split ventral channel (stage and type classification: S 6c .) and various extensions of the proximal vas deferens (PVD). The PVD went up to or passed by the vaginal opening, and then it stopped or continued along the capsule gland. In imposex females, the penis shape and the development of the vas deferens were similar to those of the male of the same species. The morphological expressions of imposex showed diverse stages and types. Reproductive failure of females occurred in 13 species. The results suggest that imposex is widespread and severe in the coastal waters of China. Based on our aims of ecological and morphological significance, a typical imposex classification could be further generalized for all 30 species by adding S 6c(*) and 2 subdivisions of the PVD. The generalized scheme was also ascertained to be valid for several morphological variations of imposex in previous work. Sterility at S 6c(*) was proven to be due to the infolding of the capsule gland wall. We thus summed up 4 mechanisms of sterility (a, b, c and *) in females. Furthermore, it was shown that the normal structure of the male genital system also affected the morphological expressions of imposex to some degree, which we referred to as 'effect of male structure'. Finally, we put forward a general classification scheme of imposex with an integrated system of aims, criteria, stages, types (subtypes), pathways and mechanisms of imposex.

International audience; Tributyltin (TBT) pollution has been assessed in NW Brittany since 1992 using the bioindicator imposex in Nucella lapillus. The Bay of Brest is highly polluted by TBT and the outgoing water mass has contaminated the adjacent NW coasts. However environmental conditions have been improving in NW Brittany. The decrease in TBT pollution is most likely due to the reformulated antifouling paints (with slower leaching rates or TBT-free) that are used for civil and military careening activities in the Bay of Brest. An increase in imposex levels in 1998 could have been due to the launching of the aircraft carrier ŒCharles de Gaulle¹. It remains unknown when imposex levels reached their maximum because of the lack of annual surveys in 1996, 1997 and 1999. This underscores the need for annual surveys when using imposex as a monitoring tool. At 3 locations within the Bay of Brest, new populations of N. lapillus have appeared since 1998. At other stations, populations have grown in number of individuals and colonised adjacent rocks. The percentage of less severely affected imposex females (vas deferens sequence stage 3) has increased since 1998. As TBT could soon be banned from antifouling paints, further recovery of favourable environmental conditions for N. lapillus is expected.

Imposex development in female whelks (Prosobranchia: Neogastropoda) has been sug- gested as a bioindicator of tributyltin (TBT) pollution in the marine environment. The occurrence of imposex in the common whelk Buccinum undatum and the red whelk Neptunea antiqua in sublittoral areas of Danish waters was related to organotin levels. In contrast, imposex was absent in reference material of N. antiqua collected in the area before 1938. The concentrations of TBT in whole body tissue of B. undatum ranged from

Stramonita (=Thais) haemastoma (Kool, 1987), a relatively large predatory snail found in rocky littoral ecosystems, can attain densities of hundreds of individuals per m 2 in warm temperate coasts of the western Atlantic. It has also been reported as common along the Israeli Mediterranean coast; however our preliminary observations there suggested low abundances of this species. We measured densities of the whelk and those of its major potential prey by quadrat and belt transect (plots) methods, supported by underwater photography when applicable. Our study demonstrates that indeed densities of S. haemastoma along the Israeli Mediterranean coast are very low (

Growth rate of individually tagged dogwhelks Nucella lapillus (L.) was measured in free-living individuals at 3 sites of differing heavy metal contamination in the Firth of Clyde, west Scotland. Condition index (CI), concentrations of metals (Cd, Cu, Pb and Zn), metallothionein (MT), RNA (the RNA/protein ratio) and glycogen were also measured. In general, the marine environments of Gourock and Largs were contaminated with significantly higher tributyltin, Pb and Zn than Loch Fyne, as indicated by the results of imposex indices, and metal concentrations in transplanted poly- mer-ligands (Chelex® 100) and Mytilus edulis. Further, metal concentrations of native M. edulis (Pb and Zn) and Semibalanus balanoides (Cu) from Gourock were significantly higher than those from Loch Fyne. However, metal accumulation in the dogwhelks displayed a very different pattern. At a standard size (0.5 g wet soft-body weight), N. lapillus from Largs showed higher Cd, Cu and MT in their tissues than individuals from the other 2 populations. Levels of Pb and Zn were similar among the populations despite different concentrations in Chelex and mussels. Gourock dogwhelks showed similar levels of Cu and MT but lower Cd compared to those of Loch Fyne. These differences can be attributed primarily to differences in dogwhelk growth rate between sites. Gourock individuals had a higher CI and RNA/protein ratio in the foot muscle and grew faster (especially at small sizes), result- ing in a tissue-dilution effect on metal and MT concentrations. In contrast, higher levels of Cd, Cu and MT in dogwhelks from Largs can be attributed to their growth rate being relatively slow compared to the rate of metal accumulation. Slow-growing individuals in Loch Fyne had relatively high Cd, Pb Zn and MT, although Loch Fyne has been regarded as a clean reference site. Among populations, dif- ferences in growth rate may be due to differences in prey availability, predation pressure, and/or genotype. The present results demonstrate that inter-site differences in growth rate can confound the use of the dogwhelks as a biomonitor of metals.

The use of tributyltin (TBT)-based antifouling paints is unregulated in Israel, and levels of contamination are high along the Mediterranean coastline there. This is indicated by concentrations of butyltins found in the tissue, and by imposex in the whelks Stramonita haemastoma and Hexaplex trunculus. Both the old (since 1974) and new (since late 1995) marinas we studied are hotspots of pollution. Imposex indices were very high at the old marina (RPSI > 100, VDSI 4 to 5); all female H. trunculus and some S. haemastoma were sterile within a distance of ca 1 km from it. The new marina offered a unique opportunity to witness the rapid and intense response of the whelks to TBT pollution in an open coastline. Despite a marked decrease in levels of contamination at distances of 1 to 2 km from both marinas, there were nevertheless detectable levels of butyltins sufficient to cause imposex in reference sites far from high shipping activity. There is evidence that TBT contamination affects abundance and relative growth rates, of male and female, of the 2 whelks around the marinas. Differences in biological response to TBT were observed between the 2 whelk species: S. haemastoma had higher levels of organotins than H. trunculus in most study sites, which may be related to different sensitivity or accumulation rates. In S. haemastoma a male-biased sex ratio was revealed around the old Tel Aviv marina, which may be derived from either female mortality or from a complete sex change in some females. Further development of marinas at coastal resorts is undesirable, certainly in the absence of regulations limiting the use of TBT-based antifoulants, and the establishment of such regulations is highly recommended.

Males of Nucella lapillus (L.), an intertidal gastropod, can suffer from a curious genetic disorder that causes underdevelopment of the reproductive tract ('Dumpton Syndrome' [DS]). Its extreme form leads to a lack of a penis ('aphally') and an incompletely developed vas deferens (VD). DS-affected females are also recognisable by a lesser degree of masculinisation ('imposex') when exposed to tributyltin (TBT) pollution, i.e. penis development may be lacking (female 'aphally') and VD formation may be weak. Based on the results of an extensive survey (at 56 stations) around Galicia (NW Spain) from 1996 to 1998, it is now known that imposex is widespread and the variations shown in its development indicate that DS also occurs widely. A modified version of the Vas Deferens Sequence (VDS) schemes currently devoted to assess the intensity of masculinization of female N. lapillus is proposed. It attempts to accommodate the variants in imposex development observed in a DS-affected population whilst remaining both simple and comparable with previously applied schemes. The proposed VDS classification solely employs VD development as a ranking criterion so as to attain a consistent scoring of both aphallic and penis-bearing females. Importantly, the evidence indicates aphally need not preclude a female from being sterilized. Both males and females afflicted by DS were scattered throughout the Galician region, although aphallic females were present at many sites at which DS males went unrecorded. Also, female aphally was commonly more frequent than male aphally on a per site basis. DS-affected males were very uncommon, never exceeding ∼20% and more frequently constituted

Several species of the subclass Prosobranchia are considered to be suitable organisms for monitoring long-term effects of triorganotin (TOT) compounds. This study utilized Buccinum undatum and Neptunea antiqua from the North Sea and the Irish Sea. Morphological alterations in the genital system (imposex phenomena), the histological structure of the gut, and the gonads were studied. TOT concentrations in soft body tissue and shells were determined. Females of both species displayed imposex phenomena (pseudohermaphroditism). The percentage of altered females per station ranged from 0 to 90% in B. undatum and from 0 to 29% in N. antiqua. Imposex index values in B. undatum reached 1.09 near Helgoland and 0.86 in N. antiqua sampled at 25 nautical miles from the Scottish northeast coast. Organotin compounds were detected in the soft bodies of snails from all stations. A chi-square analysis revealed a significant correlation between imposex stages and TOT concentrations in B. undatum but not in N. antiqua. Tributyltin (TBT) in B. undatum ranged from 1.0 to 15.9 ng g-1 wet weight (Irish east coast). TBT concentrations in N. antiqua were higher and ranged from 2.2 to 25.7 ng g-1. In both species, organotin compounds in the shells were below detection limits. Despite high TBT concentrations in soft tissues and the occurrence of imposex (offshore and inshore), female gonads were in good shape and no signs of limited reproductive capacity were found. Histological findings indicate that TBT does not contribute considerably to mortality in the common whelk.