World Congress of Malacology Antwerp ... - Unitas Malacologica

On the invasion of Biomphalaria (Gastropoda: Planorbidae) in Africa and the evolution of the
human bloodfluke Schistosoma mansoni: the palaeontological evidence
Van Damme, Dirk; Van Bocxlaer, Bert
Research Unit Palaeontology, Department of Geology and Soil Science, Geological Institute, Ghent
University, Krijgslaan 281 (S8), B-9000 Ghent, Belgium,
Email: Dirk.VanDamme@ugent.be; Bert.VanBocxlaer@ugent.be
Modern genetic research indicated Biomphalaria (PRESTON, 1910)to have invaded Africa from South
America during the Late Cenozoic and molecular clock calculations suggest this invasion to have
taken place between 4.5 and 2.3 Ma, or even later, 1.1-1.8 Ma. Molecular biologists claim this to be
in correspondence with fossil evidence of Biomphalaria in Africa, which is incorrect. The
paleontological record of Africa corroborates the genetically based invasion hypothesis, but suggests
the timescale provided by molecular clock data to be unfounded. Fossil-bearing beds all over the
African continent document Biomphalaria to be absent, until it makes an explosive, sudden
appearance around 250-200 ka. This geologically very recent appearance of Biomphalaria in Africa,
coinciding with the onset of an Interglacial, and the latest evidence on the origin of Shistosoma
mansoni, has far reaching ramifications for research concerning zoogeography as well as parasiteintermediate
host evolution and human parasitology, for the presence of Schistosoma mansoni, a
digenetic trematode and parasite of humans, is determined by the occurrence of its intermediate host,
freshwater snails of the genus Biomphalaria. This study indicates the resolution of molecular inferred
age determinations to be often too poor to make accurate claims on the divergence of taxa. The
sudden appearance of Biomphalaria in African molluscan assemblages during Late Pleistocene times
provides a useful biostratigraphic marker.
Effect of metal accumulation and metallothionein induction on the condition of the periwinkle
Littorina littorea along the entire Scheldt estuary
Van den Broeck, Heidi 1 ; De Wolf, Hans 1 ; Backeljau, Thierry 2 ; Blust, Ronny 1
1. University of Antwerp, Laboratory of Ecophysiology, Biochemistry and Toxicology,
Groenenborgerlaan 171, B-2020 Antwerp, Belgium,
Email: Heidi.VandenBroeck@ua.ac.be; Hans.DeWolf@ua.ac.be; Ronny.Blust@ua.ac.be
2. Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium,
Email: Thierry.Backeljau@naturalsciences.be
The Scheldt estuary (the Netherlands) consists of two tributaries of which the western part is heavily
polluted while the eastern is relatively clean. The western Scheldt estuary has been ranked among the
most heavily polluted estuaries in the world with reference to metal concentrations in water and
sediment (i.e. particularly Cd). Furthermore, it has a salinity gradient that opposes the downstream
decreasing metal gradient. Hence, the cadmium bioavailability will be much higher in the upstream
parts of the western Scheldt estuary (i.e. low salinity, high Cd loads) and decreases in a downstream
fashion towards higher salinity and lower ambient cadmium levels. As an important biomarker for
metal pollution, metallothionein (MT) plays an important and unique role in the homeostasis of
essential metals (i.e. Zn and Cu) and the energy demanding detoxification of toxic metals (i.e. Cd) in
invertebrates.
In this study metals (i.e. Ag, As, Ca, Cd, Co, Cu, Mn, Pb, Zn), MT levels and condition indices (i.e.
lipid content and dry weight:wet weight ratio) were measured in the periwinkle Littorina littorea to
determine differences within and between both tributaries. While metal and MT levels followed the
ambient upstream increasing pollution gradient in the western Scheldt estuary, they were opposed by
the condition indices gradients. A canonical discriminant analysis using all parameters indicated that
differences between both tributaries were mainly caused by Cd. Finally, a canonical correlation
analysis was performed which showed that periwinkles with a high metal load (i.e. Cd, Cu and Zn)
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