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

Abstract

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.

Determination of seventeen endocrine disruptor compounds and their spatial and seasonal distribution in Ria Formosa Lagoon (Portugal)

“…Other animals can be affected, including bivalves that are utterly important for the local economy. Not far from the Ria Formosa, feminization phenomena in clams, Scrobicularia plana, were recently reported (Gomes et al 2009). Besides, since it exits a possible linkage between these chemicals and several human endocrine disorders (Safe 2000), the local condition of Ria Formosa is endanger since the assayed areas are considered clean zones, accordingly to the Directive 76/160/CEE and the Portuguese legislation (DR No.…”

Widespread contamination of coastal sediments in the Transmanche Channel with anti-androgenic compounds

“…High incidences of intersexuality has been reported in the estuarine clam Scrobicularia plana in some UK estuaries as well as those in Portugal and Northwest France (Chesman and Langston, 2006;Gomes et al, 2009;Langston et al, 2007;Tankoua et al, 2012). S. plana is normally thought to be gonochoristic but at some UK sites, two-thirds of the clam population was intersex and this condition appeared to arise from a feminization or demasculinization of the male clams.…”

Intersex in the clam Scrobicularia plana (Da Costa): Widespread occurrence in English Channel estuaries and surrounding areas

“…Investigations at thirteen estuaries in NW France (including 3 sites very close to those in the present study) showed intersex in all populations sampled, with maximum incidences of >50% of the male population affected (Tankoua et al, 2012) comparable to the most impacted populations in the present study. Similarly, intersex in male clams from a single site in the Guadiana estuary in Southern Portugal varied between 5.9% and 71% during 2007 (Gomes et al, 2009). Clearly, the occurrence of intersexed male S. plana is a widespread and consistent feature at many locations within the Channel region.…”

“…Further experimental studies revealed that ovotestis in S. plana was indeed a feminization phenomenon and could be induced by exposure to sediments spiked with natural and synthetic oestrogens and alkylphenols (Langston et al, 2007). Since its initial observation in the Avon Estuary, intersex has also been reported in S. plana from Mweeloon Bay, Galway (Raleigh and Keegan, 2006); the Guadiana Estuary, Portugal (Gomes et al, 2009); and 13 estuaries in NW France (Tankoua et al, 2012).…”