Sentinel Species - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 172

damicornis , and carbonic anhydrase was significantly decreased in A. cervicornis
and M. faveolata . Likewise, significant decreases in skeletal growth were observed
in A. cervicornis and P. damicornis after copper exposure.
• De Pirro and Marshall (2005) compared the physiological and mortality responses
to copper (Cu 2+ ) of limpets from two different gastropod mollusk lineages: the
Prosobranchia (Patellogastropoda: Helcion concolor and Cellana capensis ) and the
Pulmonata ( Siphonaria serrata and Siphonaria capensis ). The Siphonaria limpets were
nearly one order of magnitude more insensitive to copper than the patellogastropod
limpets. Moreover, copper exposure (0.25 ppm Cu 2+ for 2 h) induced heart rate depres-
sion in Siphonaria spp. (to around 50% of the baseline rate), whereas their tissue copper
concentrations remained at relatively high control levels. Copper exposure (0.25 ppm
Cu 2+ for 2 h) had no effect on heart rate of the patellogastropod limpets, but led to a
significant increase in tissue copper. These authors suggest that the better regulation
of internal copper levels by Siphonaria may be related to their exclusive possession of
the Cu-requiring respiratory protein hemocyanin in the blood, and that a dependence
on relatively high aerobic metabolism by the patellogastropod limpets would limit
their capacity for isolation and pollutant avoidance.
• Responses to exposure to dissolved silver were compared between four ilter-
feeding bivalve mollusks, closely related phylogenetically and sharing a common
mode of feeding. Sensitive species (a scallop Chlamys varia and a mussel Mytilus
galloprovincialis ) and more insensitive ones (an oyster Crassostrea gigas and a zebra
mussel Dreissena polymorpha ) were discerned. Toxic impairments were very vari-
able according to the species: respiration in the mussel, byssus secretion in the
scallop, transitory energy impairment in the oyster. Relative sensitivity to silver
exposure was not based on an interspecific difference in physiological patterns of
silver bioaccumulation because the (sensitive) scallop and the (insensitive) oyster
are strong bioaccumulators, whereas both mussels (one is sensitive, the other one
tolerant) are poor bioaccumulators of silver (Berthet et al. 1992).
• In two species of crustaceans, the isopod Platynympha longicaudata and the cari-
dean decapod Palaemon (as Leander) intermedius , exposed in situ to the impact of
a lead smelter discharge, it was shown that this preexposure had generated an
increased tolerance to metals only in the case of the first of these two species dur-
ing later exposures in laboratory (Ross et al. 2002).
• Particular interest has been shown to the tolerance of the nontarget species that
are exposed during the agricultural use of pesticides. Strains of daphnids (fresh-
water crustaceans) can develop a genetic resistance to ethyl-parathion, allowing
them to survive doses 10 times higher than the sensitive strains. However, this
remains very modest compared to insects where the range reaches a factor of 100
(Barata et al. 2001 and quoted literature).
7.2.2.1.2 Vertebrates
• It is often considered that interspeciic variability of sensitivity to contaminants
is connected to the very high variability of the physiological adaptive strategies
of invertebrates. In the vertebrates with more developed homeostatic processes,
a higher homogeneity of responses might therefore be expected. In fact, for four
species of marine teleost fish, interspecific differences in behavior were shown in
response to the same sublethal dose of copper. These differences were attributed