|Effects of Tributyltin (TBT) and heavy metals on the intersex, penial gland numbers and shell morphology of the Periwinkle Littorina littorea (Linné, 1758) along the Scheldt estuary|
Collins, H. (2001). Effects of Tributyltin (TBT) and heavy metals on the intersex, penial gland numbers and shell morphology of the Periwinkle Littorina littorea (Linné, 1758) along the Scheldt estuary. MSc Thesis. Vrije Universiteit Brussel: Brussel. VIII, 81 pp.
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Chemical elements > Metals > Heavy metals
Littorina littorea (Linnaeus, 1758) [WoRMS]
Littorina littorea was collected on the 30-10-2000 at ten sampling sites along the polluted Western and relatively clean Eastern Scheldt estuary .Their shell morphology was recorded and a series of heavy metals (i.e. Silver, Aluminium, Arsenic, Calcium, Cadmium, Cobalt, Chromium, Copper, Iron, Manganese, Nickel, Lead and Zinc) were measured in their soft tissues, using inductively coupled plasma atomic emission spectrophotometry (ICP-AES). In addition, sex related abnormalities were recorded in both males, and females and were used as an indicator of TBT pollution. In males the number of penial glands and the percentage of penis shedding were recorded, while in females, the degree of intersex (i.e. ISI; gradual transformation of the female pallial oviduct towards a male reproductive system) and sterility was noted. The morphological variability was not randomly distributed but followed a certain pattern. Within the Western Scheldt, animals collected below the 15-20%0 salinity mark did not attain comparable shell sizes, as did animals that were collected above that salinity mark. Within the Eastern Scheldt, animals remained small, despite the fact that they were living at salinities well above 20%0. The metal gradients, which are known to exist in the Western Scheldt, are reflected in the animals' soft tissues and are significantly higher compared to the tissue metal levels detected in the periwinkles from the Eastern Scheldt. Female intersex and sterility has been found in both estuaries and are in general highest in the direct proximity of the harbour of Antwerp and Vlissingen. Despite the fact that current observed intersex levels were high (i.e. Borssele: ISI 1.3), they are still lower than intersex values reported in L. littorea collected at the some German ports. Male penial glands and penis shedding did not follow the intersex and/ or sterility distribution and are therefore regarded as not being useful field TBT biomonitoring characteristics.: The morphological variability does not correlate with the female sex related abnormalities, nor does it correlate with the metal tissue concentrations or salinity values. Nonetheless, a general trend is found whereby the most polluted and least saline like sites are clustered together with respect to their shell morphology. Obviously factors such as salinity , metal and TBT pollution must be important factors in determining the animals' survival and/or growth rate, despite no correlations with shell morphology could be found. Perhaps other factors that mayor may not interact with the factors that were considered in this study could explain the observed morphological structuring along and between both estuaries.