Imposex
Encyclopedia
Imposex is a descriptive term applied to some sea snail
s, marine
gastropod molluscs which, under the toxic effects of pollutant
s, develop sex organs that are in contrast to their actual sex. It is a pathological
condition where male
sex characteristics, such as the development of male sex organs, (for example the penis
and the vas deferens
) form in female
gastropods.
(TBT), which can be active in extremely low concentrations, but recent studies reported other substances as inducers, such as triphenyltin
and ethanol
. Tributyltin is an anti-fouling agent for boats which affects females of the species Nucella lapillus (dog whelk
), Voluta ebraea
(the hebrew volute), Olivancillaria vesica
, Stramonita haemastoma
and more than 200 other marine gastropods.
, although ovule
production continues. An imposex female dog whelk passes through several stages of penis growth, before it is unable to contain its constant production of ovules. Later stages of imposex can lead to the sterility
and premature death of the females, affecting the entire population
.
) are used in the United Kingdom and worldwide to monitor
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.
On September 29, 2007, the Halifax, Nova Scotia
based newspaper The Chronicle Herald featured a story on female dog whelks on the shores of Halifax Harbour and other parts of Nova Scotia, where they live on the beach in the intertidal zone
. The report stated that female dog whelks still grow penises even after a ban on tributyltin.
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s, marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
gastropod molluscs which, under the toxic effects of pollutant
Pollutant
A pollutant is a waste material that pollutes air, water or soil, and is the cause of pollution.Three factors determine the severity of a pollutant: its chemical nature, its concentration and its persistence. Some pollutants are biodegradable and therefore will not persist in the environment in the...
s, develop sex organs that are in contrast to their actual sex. It is a pathological
Pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
condition where male
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
sex characteristics, such as the development of male sex organs, (for example the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
and the vas deferens
Vas deferens
The vas deferens , also called ductus deferens, , is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation....
) form in female
Female
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
gastropods.
Imposex inducing substances
It was believed that the only inducer of imposex was tributyltinTributyltin
Tributyltin compounds are a group of compounds containing the 3Sn moiety, such as tributyltin hydride or tributyltin oxide. They are the main active ingredients in certain biocides used to control a broad spectrum of organisms...
(TBT), which can be active in extremely low concentrations, but recent studies reported other substances as inducers, such as triphenyltin
Triphenyltin
Triphenyltin compounds are organotin compounds with the general formula 3SnX. They contain the triphenyltin group, 3Sn, or Ph3Sn, which consists of an atom of tin bonded to three phenyl groups...
and ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
. Tributyltin is an anti-fouling agent for boats which affects females of the species Nucella lapillus (dog whelk
Dog Whelk
The dog whelk, dogwhelk, or Atlantic dogwinkle, scientific name Nucella lapillus, is a species of predatory sea snail, a carnivorous marine gastropod mollusc in the family Muricidae, the rock snails....
), Voluta ebraea
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 its collected both for food and for its shell, which is highly desired for ornamental purposes...
(the hebrew volute), Olivancillaria vesica
Olivancillaria vesica
Olivancillaria vesica is a species of sea snail, a marine gastropod mollusk in the family Olividae, the olives....
, Stramonita haemastoma
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. -Distribution:...
and more than 200 other marine gastropods.
Abnormalities
The penis growth of imposex female dog whelks blocks the oviductOviduct
In non-mammalian vertebrates, the passageway from the ovaries to the outside of the body is known as the oviduct. The eggs travel along the oviduct. These eggs will either be fertilized by sperm to become a zygote, or will degenerate in the body...
, although ovule
Ovule
Ovule means "small egg". 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 , and the megaspore-derived female gametophyte in its center...
production continues. An imposex female dog whelk passes through several stages of penis growth, before it is unable to contain its constant production of ovules. Later stages of imposex can lead to the sterility
Infertility
Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...
and premature death of the females, affecting the entire population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
.
Biomonitoring
The imposex stages of female dog whelks and other molluscs (including Nucella limaNucella lima
Nucella lima, common name : the File Dog Winkle, is a species of sea snail, a marine gastropod mollusk in the family Muricidae, the murex snails or rock snails.-Description:The shell size varies between 19 mm and 51 mm-Distribution:...
) are used in the United Kingdom and worldwide to monitor
Biomonitoring
Aquatic biomonitoring is the science of inferring the ecological condition of rivers, lakes, streams, and wetlands by examining the organisms that live there...
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.
On September 29, 2007, the Halifax, Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
based newspaper The Chronicle Herald featured a story on female dog whelks on the shores of Halifax Harbour and other parts of Nova Scotia, where they live on the beach in the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
. The report stated that female dog whelks still grow penises even after a ban on tributyltin.