Aquatic Vertebrates

The major routes of uptake of xenobiotics by animals and plants are discussed in Chapter 4, Section 4.1. With animals, there is an important distinction between terrestrial species, on the one hand, and aquatic invertebrates and fish on the other. The latter readily absorb many xenobiotics directly from ambient water or sediment across permeable respiratory surfaces (e.g., gills). Some amphibia (e.g., frogs) readily absorb such compounds across permeable skin. By contrast, many aquatic vertebrates, such as whales and seabirds, absorb little by this route. In lung-breathing organisms, direct absorption from water across exposed respiratory membranes is not an important route of uptake. 

Biomagnification along aquatic food chains may be the consequence of bioconcentration as well as bioaccumulation. Aquatic vertebrates and invertebrates can absorb pollutants from ambient water bottom feeders can take up pollutants from sediments. The bioconcentration factor (BCF) of a chemical absorbed directly from water is defined as... 

PAHs can be bioconcentrated or bioaccumulated by certain aquatic invertebrates low in the food chain that lack the capacity for effective biotransformation (Walker and Livingstone 1992). Mollusks and Daphnia spp. are examples of organisms that readily bioconcentrate PAH. On the other hand, fish and other aquatic vertebrates readily biotransform PAH so, biomagnification does not extend up the food chain as it does in the case of persistent polychlorinated compounds. As noted earlier, P450-based monooxygenases are not well represented in mollusks and many other aquatic invertebrates (see Chapter 4, Section 4.2) so, this observation is not surprising. Oxidation catalyzed by P450 is the principal (perhaps the only) effective mechanism of primary metabolism of PAH. 

Lethality Mammalian systems Aquatic vertebrates and invertebrates Plants Lethal dose5o (LD50) Lethal concentration 50 (LC50) Both LD50/LC50 values greater than a reference compound... 

Acute toxicity In vitro Mammalian systems Aquatic vertebrates and invertebrates Plants IC/EC50 in appropriate test species Use of appropriate indicators of acute toxicity, for example, EPA guidance values, reference doses, and so on... 

Chronic toxicity Mammalian systems Carcinogenicity Neurotoxicity De ve 1 opm e nta l/rep rod u cti ve toxicity Aquatic vertebrates and invertebrates Plants Mutagenicity, increased tumours Reproduction and growth Cancer slope factors Reference doses, and so on IC50, EC50... 

Benzo[a]pyrene effects on selected aquatic vertebrates... 

Table 25.7 Benzo[a]pyrene Effects on Selected Aquatic Vertebrates... 

Previous studies have found that cyanotoxic compounds may accumulate in sym-patric plants as well as in the tissues of herbivorous fish and invertebrates (reviewed in Zurawell et al. 2005). The accumulation of cyanotoxins at these trophic levels provides a direct path to both aquatic and, potentially, terrestrial consumers (Negri and Jones 1995 Kotak et al. 1996 Giovannardi et al. 1999). However, these compounds are rarely encountered in higher trophic levels in freshwater systems (Kotak et al. 1996 Zurawell et al. 2005). Nevertheless, attempts to minimize cyanotoxins in water bodies for recreational use should remain a major focus of environmental and public health managers, especially in light of the evidence that low doses may still have sublethal effects on the larval development of aquatic vertebrates (Oberemm et al. 1999). 

Table 2. Elimination of cyclodienes by aquatic vertebrates following their transfer, after maximum absorption in a static system, to insecticide-free water. 

Figure 3. Rates of elimination of cyclodienes by aquatic vertebrates. Animals were transferred to clean water after maximum absorption in static systems (A), goldfish treated with photo-cis-chlordane (B), Xenopus with cis-chlordane (C), goldfish injected with heptachlor (D), goldfish with cis-chlordane (E), blue gills with photo-cis-chlordane (F), bluegills with photodieldrin and (G), cichlids with...

Ample evidence exists to show that aquatic vertebrates are able to metabolize aromatic hydrocarbons to a variety of conjugated and non-conjugated derivatives. It was shown with fish that the metabolite aromatic hydrocarbon ratio tends to increase after hydrocarbon exposure. Under conditions of depuration (clean water environments) either hydrocarbons or metabolites are discharged through gills, bile, urine, skin, and mucus of marine fish. Further work is necessary with phylogenetically diverse species because the above conclusions are based on only a few studies of selected organisms. 

Mirza, R. S. and Chivers, D. P. (2001). Do chemical alarm signals enhance survival of aquatic vertebrates. An analysis of the current research paradigm. In Chemical Signals in Vertebrates, vol. 9, ed. A. Marchlewska-Koj, J. J. Lepri, and D. Miiller-Schwarze, pp. 19-26. New York Kluwer Academic/Plenum. 

Available data for aquatic invertebrates and boron suggest that the no-observable-effect levels were 13.6 mg B/L for freshwater organisms and 37 mg B/L for marine biota (Table 29.7). Juvenile Pacific oysters Crassostrea gigas) accumulated boron in relation to availability, but showed no prolonged retention following cessation of exposure (Thompson et al. 1976). At industrial discharge levels of about 1.0 mg B/L, no hazard is apparent to oysters and aquatic vertebrates (Thompson et al. 1976). 

Boron may be an essential nutrient in several species of aquatic vertebrates. Insufficient boron (<3 pg B/L 62 pg B/kg ration) interfered with the normal development of the South Afiican clawed frog (Xenopus laevis) during organogenesis, and substantially impaired normal reproductive function in adult frogs (Fort et al. 1998). Impaired growth of rainbow trout (Oncorhynchus mykiss) embryos was documented at <90 pg B/L, and death of zehrafish (Brachydanio rerio) embryos at <2 pg B/L (Rowe et al. 1998). 

Van Ballegooy, C., Wiedemann, C. and Lutz, I. (2009) Endocrine disruption in aquatic vertebrates. Trends Comp. Endocrinol. Neurobiol., 1163, 187—200. 

Ammonotelic animals most aquatic vertebrates, such as bony fishes and the larvae of amphibia... 

Plants, invertebrate animals, aquatic vertebrate animals, and organisms that may be used in multispecies tests need... 

Kudryavtseva, G.V. (1990). Ecologio-physiological features and the role of the pentose-phosphate shunt for carbohydrate metabolism in adaptations of lower aquatic vertebrates (Cyclostomes and Pisces) (In Russian). Uspekhi Sovremennoy Biologii 109,171-182. 

Kirschner, L.B. (1997). Extrarenal mechanisms in hydromineral balance and acid-base regulation in aquatic vertebrates. In Handbook of Physiology, Section 13 Comparative Physiology. Vol. I, pp. 577-622, ed. W. Dantzler. New York Oxford. 

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