SEMINAR: MBF 602 Abstract for Friday Seminar 4p

["sidney hartley" <shartley@rsmas.miami.edu>]

Investigation into the Mechanisms of Chronic Lead Toxicity to the Freshwater
Snail, Lymnaea stagnalis

Previous studies have shown that the freshwater pulmonate snail, Lymnaea
stagnalis, is among the most sensitive aquatic organism tested to date in
chronic Pb exposures.  It has been hypothesized that this sensitivity is the
result of Pb directly inhibiting of Ca2+ uptake which is required for shell
growth.  This hypothesis is supported by both direct measurements of
inhibited Ca2+ uptake and a cascade of secondary effects on ionoregulation
and acid base balance, consistent with reduced calcification for shell
formation.  The current study sought to validate this hypothesis and develop
a mechanistic model for predicting long-term growth effects on Pb exposed
snails based on short-term measurements of Ca2+ flux.  However, a detailed
time course study of net Ca2+ flux in Pb exposed snails revealed that growth
inhibition was not directly linked to inhibition of Ca2+ uptake.  Rather it
appears inhibition of Ca2+ uptake is a secondary response.  Qualitative
observations during these experiments suggest feeding was inhibited in
Pb-exposed snails leading to an additional hypothesis that reduced food
consumption was the primary toxic response.  A second set of experiments
demonstrated quantitatively that feeding is inhibited in a dose-dependent
manner in Pb exposed snails and that when food is withheld from snails not
exposed to Pb, there is a rapid (within 24 h) downregulation of Ca2+ uptake,
supporting the hypothesis that feeding inhibition is the primary mechanism
of toxic action in Pb-exposed snails.  However, detailed evaluation of
dose-response data suggests that while feeding inhibition may be the
mechanism of toxic action in snails exposed to ≥20 mg l-1 Pb, it does not
explain observed effects on snail growth at concentrations as low as 4 mg
l-1 Pb.   

 

Kevin Brix

University of North Florida, B.S. Biology 2008

Entered Ph.D. Program Fall 2009

Advisor: Martin Grosell

 

Sidney Hartley

305-421-4176

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