Imposex

Imposex is a descriptive term applied to some sea snails, marine gastropod molluscs which, under the toxic effects of pollutants, 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.

Contents

Imposex inducing substances

It was believed that the only inducer of imposex was tributyltin (TBT),[1] which can be active in extremely low concentrations, but recent studies reported other substances as inducers, such as triphenyltin[2] and ethanol.[3] Tributyltin is an anti-fouling agent for boats which affects females of the species Nucella lapillus (dog whelk), Voluta ebraea (the hebrew volute),[4] Olivancillaria vesica,[5] Stramonita haemastoma[6] and more than 200 other marine gastropods.

Abnormalities

The penis growth of imposex female dog whelks blocks the oviduct, 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.[4]

Biomonitoring

The imposex stages of female dog whelks and other molluscs (including Nucella lima) 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.[7]

See also

References

  1. ^ Ruiz JM, Quintela M, Barreiro R (1998) Tributyltin and imposex. no uncertainty shown. Mar Ecol Prog Ser 170: 293-294
  2. ^ Horiguchi, T.; et al (1995). "Imposex in Japanese gastropods (Neogastropoda and Mesogastropoda): effects of tributyltin and triphenyltin from anti-fouling paints". Marine Pollution Bulletin (Oxford) 31 (4–12): 402–405. doi:10.1016/0025-326X(95)00133-8. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6N-404RMY0-18&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1026249491&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=637bfa79b5ab2d19394e2b32d38a4ef7. 
  3. ^ Davies, I. M.; et al (1997). "Sublethal effects of tributyltin oxide on thedog whelk Nucella lapillus". Marine Ecology Progress Series 158: 191–204. doi:10.3354/meps158191. 
  4. ^ a b Castro, Í. B.; et al. (2008). "Imposex in endemic volutid from Northeast Brazil (Mollusca: Gastropoda)". Brazilian Archives of Biology and Technology (Brazil) 51 (5): 1065–1069. ISSN 1516-8913. http://www.scielo.br/pdf/babt/v51n5/a24v51n5.pdf. 
  5. ^ Caetano, C. H. S.; Absalão, R. S. (2002). "Imposex in Olivancillaria vesica vesica (Gmelin) (Gastropoda, Olividae) trom a Southeastern Brazilian sandy beach". Revista Brasileira de Zoologia (Brazil: Sociedade Brasileira de Zoologia) 19 (2): 215–218. doi:10.1590/S0101-81752002000600022. ISSN 0101-8175. http://www.scielo.br/pdf/rbzool/v19s2/v19supl2a22.pdf. 
  6. ^ Fernandez, M. A.; et al (2002). "Occurrence of imposex in Thais haemastoma: possible evidence of environmental contamination derived from organotin compounds in Rio de Janeiro and Fortaleza, Brazil". Cadernos de Saúde Pública (Rio de Janeiro, Brazil: Fundação Oswaldo Cruz) 18 (2): 463–476. doi:10.1590/S0102-311X2002000200011. ISSN 0102-311X. http://www.scielosp.org/pdf/csp/v18n2/8275.pdf. 
  7. ^ "Tiny Snail, Big Problem" The Chronicle Herald, Halifax, NS, Canada. Sat, September 29th, 2007. http://www.thechronicleherald.ca/Science/914854.html

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