Intersex in the clam
            <i>Scrobicularia plana</i>
            : a sign of endocrine disruption in estuaries?

Chesman, BS; Langston, W.J.

doi:10.1098/rsbl.2006.0482

Cited by 45 publications

(46 citation statements)

References 15 publications

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“…Consequently, the sex ratio between males and females decreased significantly (P \ 0.05). Chesman and Langston (2006) detected a ratio of males (without intersex) to females lower than the unity in the S. plana population from the Avon Estuary (United Kingdom), thus confirming the result obtained in this study. In the studies that reported the existence of 'hermaphrodites' in this species, the sex ratio indicated a slight predominance of females to males, however with no significant differences (Paes-da-Franca 1956; Raleigh and Keegan 2006).…”

Section: Resultssupporting

confidence: 94%

Incidence of intersex in male clams Scrobicularia plana in the Guadiana Estuary (Portugal)

2009

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Endocrine disrupting chemicals (EDCs) known to be present in the marine environment, have great potential to influence reproductive status in aquatic organisms. A widespread incidence of intersex linked with EDCs exposure has been reported in molluscs and fish species. The species Scrobicularia plana is inherently gonochoristic; nonetheless, the feminisation of male clams was described in estuaries from the United Kingdom. Thus, this study reports the presence of oocytes in the testis of male clams of S. plana collected in the Guadiana River (Portugal). Samples were collected between June and September (2007), and gonad tissue analysed by light microscopy. Intersex with several degrees of intensity was detected during the first three months of sampling, in which the percentage of male clams affected varied between 5.9, 58.3 and 71.4%. Little is known about the causes of intersex in S. plana, being the urban, industrial and agricultural discharges possible major sources of induction. In the Guadiana River, the presence of several EDCs may be directly linked to the incidence of the intersex condition detected in Scrobicularia plana.

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Section: Resultssupporting

confidence: 94%

Incidence of intersex in male clams Scrobicularia plana in the Guadiana Estuary (Portugal)

2009

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“…We are currently constructing a ranking system of the condition, adapted from a scoring index used to categorise different degrees of intersex in fish (Bateman et al 2004). The scheme, based on histological examination completed to date, has identified 6 stages in clams (Chesman & Langston 2006) and will be used as an additional parameter in the evaluation of intersex in future comparisons. Based on current evidence, the levels of severity and frequency in S. plana populations appear to be analogous to those in fish.…”

Section: Exposedmentioning

confidence: 99%

Feminisation of male clams Scrobicularia plana from estuaries in Southwest UK and its induction by endocrine-disrupting chemicals

Langston¹,

Burt²,

Chesman³

2007

Mar. Ecol. Prog. Ser.

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The risk of endocrine disruption in the marine environment is unclear and is often overlooked in invertebrates. We show that disruption to the 'normal' gonadal development of male estuarine clams Scrobicularia plana is occurring extensively at sites in Southwest UK, with populations exhibiting varying degrees of intersex (ovotestis). This is one of the few studies to have examined the extent of the condition in mollusc populations. Intersex was present in more than two-thirds of the populations screened from the Avon, Southampton Water, Bristol Channel/Severn, Erme, Plym, Fal, Tamar and Lynher Estuaries; severity varied, with between 0 and 60% of males exhibiting the condition. Prevalence of intersex tended to peak as gonads reached maturity in July, and was highest in clams from the Bristol Channel and Severn Estuary, coinciding with an increase in oocyte size in both the female gonad and in the ovotestis of affected males. Experimental exposures to sediment spiked with mixtures of 17β-oestradiol (E2), 17α-ethinyloestradiol (EE2), octylphenol (OP) and nonylphenol (NP) indicated that (xeno)estrogens could be a contributory factor in the induction of intersex and increased oocyte size. It is plausible, therefore, that the incidence of ovotestis may be linked to urban, industrial and agricultural influences, or a combination thereof, although the relative importance of these sources has yet to be determined. S. plana offers potential as a sentinel species for screening and investigation of endocrine disruption in the estuarine environment, helping to focus remediatory strategy where it would be most beneficial. KEY WORDS: Endocrine disruption · Intersex · Ovotestis · Scrobicularia plana · EstuariesResale or republication not permitted without written consent of the publisher

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“…Similar studies on sewage exposure have detected increased vitellogenin-like proteins in males, feminised sex ratios and low gonadosomic indices. Varying degrees of intersex also reported in over 20 % of individual bivalves ( Scrobicularia plana ) sampled from 17 out of 23 British estuaries (Gomes et al 2009 ;Chesman and Langston 2006 ) Bisphenol A (BPA) was reported to act as an estrogen receptor agonist in ramshorn snails because effects were antagonized by co-exposure to ER-antagonists (Oehlmann et al 2006 ). These results could not be replicated by Forbes et al ( 2008 ) and remain controversial Potent androgen receptor agonists and aromatase inhibitors, as well as marine anti-fouling paint component tributyl tin (TBT), induce "imposex" in female gastropod molluscs at concentrations as low as parts per billion (Horiguchi 2006 ).…”

Section: Endocrine Disruption In Invertebratesmentioning

confidence: 95%

Impacts of Endocrine Disrupting Chemicals on Reproduction in Wildlife

Kumar

Holt

2014

Advances in Experimental Medicine and Biology

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The European Environment Agency (The Weybridge + 15 (1996-2011) report. EEA Technical report, vol 2. Copenhagen, 2012) and the United Nations Environment programme together with the World Health Organisation (State of the science of endocrine disrupting chemicals-2012. Geneva, Switzerland) both recently published major and highly authoritative reviews of endocrine disrupting chemicals in the natural environment and their effects on reproduction and health in both humans and wildlife. One surprising conclusion to emerge from these reviews was that there are relatively few well documented reports of endocrine disruption (ED) in wild mammals, mainly because much of the available evidence is correlative and does not conclusively demonstrate that the chemicals in question cause the physiological and phenotypic problems attributed to them. However, based on strong evidence from studies of wild birds, reptiles, invertebrates, and laboratory animals, it is difficult to imagine that wild mammals would be the exception. This chapter is therefore included to emphasize the point that the role of reproductive science within wildlife conservation is much broader than a narrow focus on artificial breeding technologies.

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Intersex in the clam Scrobicularia plana : a sign of endocrine disruption in estuaries?

Cited by 45 publications

References 15 publications

Incidence of intersex in male clams Scrobicularia plana in the Guadiana Estuary (Portugal)

Incidence of intersex in male clams Scrobicularia plana in the Guadiana Estuary (Portugal)

Feminisation of male clams Scrobicularia plana from estuaries in Southwest UK and its induction by endocrine-disrupting chemicals

Impacts of Endocrine Disrupting Chemicals on Reproduction in Wildlife

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