Imposex is a disorder in

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the a ...

s caused by the

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a sub ...

effects of certain marine

pollutant A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like o ...

s. These pollutants cause female

s (

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is est ...

s) to develop male

sex organs A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, ...

such as a

penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...

and a

vas deferens The vas deferens or ductus deferens is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube ...

Imposex inducing substances

It was believed that the only inducer of imposex was

tributyltin Tributyltin (TBT) is an umbrella term for a class of organotin compounds which contain the (C4H9)3 Sn group, with a prominent example being tributyltin oxide. For 40 years TBT was used as a biocide in anti-fouling paint, commonly known as bott ...

(TBT), which can be active in extremely low concentrations, but recent studies reported other substances as inducers, such as

triphenyltin Triphenyltin compounds are organotin compounds with the general formula (C6H5)3SnX. They contain the triphenyltin group, (C6H5)3Sn, or Ph3Sn, which consists of an atom of tin bonded to three phenyl groups. Examples of triphenyltins include: * Triph ...

and

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

. Tributyltin is used as an anti-fouling agent for boats which affects females of the species ''

Nucella lapillus The dog whelk, dogwhelk, or Atlantic dogwinkle (''Nucella lapillus'') is a species of predatory sea snail, a carnivorous marine gastropod in the family Muricidae, the rock snails. ''Nucella lapillus'' was originally described by Carl Linnaeu ...

'' ( dog whelk), ''

Voluta ebraea ''Voluta ebraea'', common name the Hebrew volute, is a species of medium-sized sea snail, a marine gastropod mollusk in the family Volutidae, the volutes. The Hebrew volute is endemic to Brazil, where it is collected both for food and for its s ...

'' (the Hebrew volute), '' Olivancillaria vesica'', '' Stramonita haemastoma'' (red-mouthed rock shell) and more than 200 other marine gastropods.

Abnormalities

In the dog whelk, the growth of a penis in imposex females gradually blocks the oviduct, although

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...

production continues. An imposex female dog whelk passes through several stages of penis growth before it becomes unable to maintain a constant production of ovules. Later stages of imposex lead to sterility and the premature death of the females of reproductive age, which can adversely affect the entire

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction usi ...

. In 1993, Scientists from the Plymouth Marine Laboratory found a thriving dog-whelk population in the Dumpton Gap, near Ramsgate in the UK despite high levels of TBT in the water.Gibbs, Journal of the Marine Biological Association, 1993, vol 73, p 667 In the Dumpton Gap population, only 25% of females showed any significant signs of imposex, while 10% of males were characterized by the absence of a penis or an undersized penis, with incomplete development of the vas deferens and prostate. After further experiments, scientists concluded that "Dumpton Syndrome" was a genetic selection caused by high TBT levels. TBT-resistance was improved at the cost of lower reproductive fitness.

Biomonitoring

The imposex stages of female dog whelks and other molluscs (including ''

Nucella lima ''Nucella lima'', common name : the File Dog Winkle, is a species of sea snail, a marine gastropod mollusk in the family Muricidae Muricidae is a large and varied taxonomic family of small to large predatory sea snails, marine gastropo ...

'') are used in the United Kingdom and worldwide to

monitor Monitor or monitor may refer to: Places * Monitor, Alberta * Monitor, Indiana, town in the United States * Monitor, Kentucky * Monitor, Oregon, unincorporated community in the United States * Monitor, Washington * Monitor, Logan County, West ...

levels of tributyltin. The RPSI (Relative Penis Size Index) of females to males, and the VDSI (Vas Deferens Sequence Index) are used to monitor levels of tributyltin in marine environments. A ban on tributyltin was implemented in Canada in 2003, however, in 2006, dog whelks with imposex could still be found on the shores of Halifax Harbour in Nova Scotia.

References

{{reflist, 2 * Gibbs, P.E., Bryan, G.W. (1986). Reproductive failure in populations of the dog-whelk ''Nucella lapillus'', caused by imposex induced by tributyltin from antifouling paints. ''J. Mar. Biol. Assoc. U. K.'' 66: 767–777. *
Occurrence of Imposex.
Natural Resource Management. 2006. * Wirzinger, G., Vogt, C., Bachmann, J., Hasenbank, M., Liers, C., Stark, C., Ziebard, S. & Oehlmann, J. (2007). Imposex of the netted whelk ''Nassarius reticulatus'' (Prosobranchia) in Brittany along a transect from a point source. ''Cah. Biol. Mar''. 48(1): 85–94.

External links

''Tributyltin (TBT) antifoulants: a tale of ships, snails and imposex''
Gastropods Animal diseases Marine biology Intersex and medicine

Imposex inducing substances

Abnormalities

Biomonitoring

See also

References

External links