309
chapter fourteen
Toxicology and poisons
John R. Harley and Todd M. O’Hara
14.1 Introduction
All marine mammals must deal with many classes of poisons, both natural and anthropogenic, via numerous routes of exposure (Figure 14.1). Both marine-based toxins
(i.e., domoic acid) and terrestrially originated (intentional and unintentional releases)
poisons (i.e., dichlorodiphenyltrichlorethane, DDT) are present in appreciable amounts
in the marine environment. Many of the industrial sourced compounds are biologically
novel (xenobiotic) on millennial or evolutionary time scales. However, there are a number
of marine biotoxins and elements (mercury, cadmium, etc.), including some of the most
potent poisons known (e.g., ciguatoxin, brevitoxin, and tetradotoxin) that are produced as
secondary metabolites by marine organisms and have likely been present throughout the
evolution of marine mammal species (Fowler 1993; Fire and Van Dolah 2012). These poisons have been implicated in a number of acute disease events as well as mass die-offs and
likely contribute significantly to the health and management status of some marine mammal populations. For instance, of the 60 identified marine mammal unusual mortality
events (UMEs) from 1991 to 2013, the largest proportion of etiologically determined events
Contents
14.1 Introduction ........................................................................................................................309
14.2 Physiology and bioaccumulation .................................................................................... 314
14.2.1 Maternal transfer: Early exposure to poisons ................................................... 315
14.2.1.1 Placental mammals ................................................................................. 315
14.2.1.2 Blubber and nursing ............................................................................... 316
14.3 Biotoxins and the evolutionary chemical arms race ..................................................... 316
14.3.1 Cetaceans ................................................................................................................ 318
14.3.2 Pinnipeds ................................................................................................................ 318
14.3.3 Other ........................................................................................................................ 320
14.4 Toxic oxygen: Adaptations to anaerobic diving ............................................................ 320
14.5 Metals and detoxification ................................................................................................. 321
14.5.1 Cetaceans ................................................................................................................ 323
14.5.2 Pinnipeds ................................................................................................................ 324
14.6 Other poisons ..................................................................................................................... 325
14.7 Emerging tools ................................................................................................................... 325
14.8 Lingering questions ........................................................................................................... 326
Glossary ........................................................................................................................................ 327
References ..................................................................................................................................... 328
chapter fourteen
Toxicology and poisons
John R. Harley and Todd M. O’Hara
14.1 Introduction
All marine mammals must deal with many classes of poisons, both natural and anthropogenic, via numerous routes of exposure (Figure 14.1). Both marine-based toxins
(i.e., domoic acid) and terrestrially originated (intentional and unintentional releases)
poisons (i.e., dichlorodiphenyltrichlorethane, DDT) are present in appreciable amounts
in the marine environment. Many of the industrial sourced compounds are biologically
novel (xenobiotic) on millennial or evolutionary time scales. However, there are a number
of marine biotoxins and elements (mercury, cadmium, etc.), including some of the most
potent poisons known (e.g., ciguatoxin, brevitoxin, and tetradotoxin) that are produced as
secondary metabolites by marine organisms and have likely been present throughout the
evolution of marine mammal species (Fowler 1993; Fire and Van Dolah 2012). These poisons have been implicated in a number of acute disease events as well as mass die-offs and
likely contribute significantly to the health and management status of some marine mammal populations. For instance, of the 60 identified marine mammal unusual mortality
events (UMEs) from 1991 to 2013, the largest proportion of etiologically determined events
Contents
14.1 Introduction ........................................................................................................................309
14.2 Physiology and bioaccumulation .................................................................................... 314
14.2.1 Maternal transfer: Early exposure to poisons ................................................... 315
14.2.1.1 Placental mammals ................................................................................. 315
14.2.1.2 Blubber and nursing ............................................................................... 316
14.3 Biotoxins and the evolutionary chemical arms race ..................................................... 316
14.3.1 Cetaceans ................................................................................................................ 318
14.3.2 Pinnipeds ................................................................................................................ 318
14.3.3 Other ........................................................................................................................ 320
14.4 Toxic oxygen: Adaptations to anaerobic diving ............................................................ 320
14.5 Metals and detoxification ................................................................................................. 321
14.5.1 Cetaceans ................................................................................................................ 323
14.5.2 Pinnipeds ................................................................................................................ 324
14.6 Other poisons ..................................................................................................................... 325
14.7 Emerging tools ................................................................................................................... 325
14.8 Lingering questions ........................................................................................................... 326
Glossary ........................................................................................................................................ 327
References ..................................................................................................................................... 328