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 ...
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 subst ...
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 oi ...
s. These pollutants cause female
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 ...
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 esti ...
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, a ...
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 do n ...
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
![Tributyltin hydride](https://upload.wikimedia.org/wikipedia/commons/2/27/Tributyltin_hydride.png)
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 botto ...
(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 (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
.
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 Linnaeus in ...
'' (
dog whelk
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 Linnaeus in ...
), ''
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 sh ...
'' (the Hebrew volute),
''
Olivancillaria vesica'',
''
Stramonita haemastoma
''Stramonita haemastoma'', common name the red-mouthed rock shell or the Florida dog winkle, is a species of predatory sea snail, a marine gastropod mollusc in the family Muricidae, the rock snails.
Subspecies
''Stramonita haemastoma'' conta ...
''
(red-mouthed rock shell) and more than 200 other marine gastropods.
Abnormalities
In the
dog whelk
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 Linnaeus in ...
, the growth of a penis in imposex females gradually blocks the
oviduct
The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...
, 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 fe ...
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 using a ...
.
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 (biology), family Muricidae, the murex snails or rock snails.
Distribution
This species is distributed in the Pacific Ocea ...
'') 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 Vir ...
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 environment
Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea (the term ''marine'' comes from the Latin ''mare'', meaning sea or ocean). A habitat is an ecological or environmental ...
s.
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.
See also
*
Environmental issues with paint
The environmental effects of paint can vary depending on the type of paint used and mitigation measures. Traditional painting materials and processes can have harmful effects on the environment, including those from the use of lead and other addi ...
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