326
Marine Mammal Physiology: Requisites for Ocean Living
bottlenose dolphin, polar bear, killer whale, Weddell seal, Pacific walrus, and Florida
manatee. The generation of whole genome sequence data has the potential to elucidate a
number of questions associated with marine mammal physiology and adaptation; with
direct relevance to toxicology. Because of the polyphyletic nature of marine mammals,
many of the phenotypic adaptations present in numerous orders provide excellent examples of convergent evolution. Recent work to examine loci that are currently under selective pressure in three orders of marine mammals (represented by walrus, manatee, and
killer whale genomes) found evidence that genes associated with the glutathione metabolism pathway (ANPEP and GCLC) were under positive selection (Foote et al., 2015). It is
likely that the selective pressures acting on these loci are based on hypoxia and diving
physiology; however, given the importance of glutathione in detoxification pathways, it is
certainly intriguing to consider the adaptation of the glutathione system in the context of
toxicology. Many unexplored gene– environment (toxicants) interactions and responses of
marine mammals (e.g., gene expression) to toxicants are now open to investigators with
the courage and imagination to venture into these unknown waters.
High-throughput gene chips, such as cDNA microarrays, capable of measuring the
expression levels of thousands of genes (increase, decrease, or no change in specific
mRNA) have been utilized to examine the gene status of a number of marine mammal
species in response to contaminants and disease (Mancia et al. 2012, 2014). The microarray,
while still being utilized and customized to particular marine mammal species and gene
groups (i.e., immune function genes) may have already peaked in usefulness with the
advancement of high-throughput sequencing technologies such as RNA-seq (Shendure
2008). Incorporating additional omics tools (transcriptomics, metabolomics, proteomics)
have the ability to push marine mammal toxicology research to the forefront of emerging
technologies. High-throughput mass-spectroscopy techniques for identifying proteins
have been utilized to study the effects of MeHg on human lymphocytes at environmentally relevant concentrations (i.e., concentrations found in harbor seals) (Das et al. 2008).
Novel methods for collecting cetacean saliva and blow, including using radiocontrolled unmanned aerial vehicles, can potentially provide insight into the respiratory condition and health status of marine mammals (Acevedo-Whitehouse et al. 2010).
Bacteria species present in blow and respiratory mucosa can be analyzed to investigate
disease status and prevalence (Acevedo-Whitehouse et al. 2010), while other researchers
have examined the utility of blows to measure levels of hormones (Hogg et al. 2009) or the
detection of volatile organics (Cumeras et al. 2014).
In addition to direct sampling of marine mammals, there have been a number of developments in the detection and prediction of HABs including the genomic identification of
toxin-producing bacteria species as well as satellite imaging in order to detect concentrations of algae in seawater (for review see Anderson et al. 2012). There are several challenges
to detecting algal toxins in seawater or biologic tissue, including occasionally very low concentrations. However, the development of liquid chromatography coupled with mass spectroscopy (LC-MS) has provided the ability to simultaneously identify low concentration
toxins as well as novel marine phycotoxins (Hummert et al. 2002; Zhang and Zhang 2015).
14.8 Lingering questions
As described above, the rapid evolution of omics technologies and increasingly sensitive/
high-throughput mass spectroscopy has advanced our capability to examine in ultra-fine
scale both the presence of potentially deleterious compounds as well as their negative
effects. However, connecting the presence of toxins or toxicants to individual health status
Marine Mammal Physiology: Requisites for Ocean Living
bottlenose dolphin, polar bear, killer whale, Weddell seal, Pacific walrus, and Florida
manatee. The generation of whole genome sequence data has the potential to elucidate a
number of questions associated with marine mammal physiology and adaptation; with
direct relevance to toxicology. Because of the polyphyletic nature of marine mammals,
many of the phenotypic adaptations present in numerous orders provide excellent examples of convergent evolution. Recent work to examine loci that are currently under selective pressure in three orders of marine mammals (represented by walrus, manatee, and
killer whale genomes) found evidence that genes associated with the glutathione metabolism pathway (ANPEP and GCLC) were under positive selection (Foote et al., 2015). It is
likely that the selective pressures acting on these loci are based on hypoxia and diving
physiology; however, given the importance of glutathione in detoxification pathways, it is
certainly intriguing to consider the adaptation of the glutathione system in the context of
toxicology. Many unexplored gene– environment (toxicants) interactions and responses of
marine mammals (e.g., gene expression) to toxicants are now open to investigators with
the courage and imagination to venture into these unknown waters.
High-throughput gene chips, such as cDNA microarrays, capable of measuring the
expression levels of thousands of genes (increase, decrease, or no change in specific
mRNA) have been utilized to examine the gene status of a number of marine mammal
species in response to contaminants and disease (Mancia et al. 2012, 2014). The microarray,
while still being utilized and customized to particular marine mammal species and gene
groups (i.e., immune function genes) may have already peaked in usefulness with the
advancement of high-throughput sequencing technologies such as RNA-seq (Shendure
2008). Incorporating additional omics tools (transcriptomics, metabolomics, proteomics)
have the ability to push marine mammal toxicology research to the forefront of emerging
technologies. High-throughput mass-spectroscopy techniques for identifying proteins
have been utilized to study the effects of MeHg on human lymphocytes at environmentally relevant concentrations (i.e., concentrations found in harbor seals) (Das et al. 2008).
Novel methods for collecting cetacean saliva and blow, including using radiocontrolled unmanned aerial vehicles, can potentially provide insight into the respiratory condition and health status of marine mammals (Acevedo-Whitehouse et al. 2010).
Bacteria species present in blow and respiratory mucosa can be analyzed to investigate
disease status and prevalence (Acevedo-Whitehouse et al. 2010), while other researchers
have examined the utility of blows to measure levels of hormones (Hogg et al. 2009) or the
detection of volatile organics (Cumeras et al. 2014).
In addition to direct sampling of marine mammals, there have been a number of developments in the detection and prediction of HABs including the genomic identification of
toxin-producing bacteria species as well as satellite imaging in order to detect concentrations of algae in seawater (for review see Anderson et al. 2012). There are several challenges
to detecting algal toxins in seawater or biologic tissue, including occasionally very low concentrations. However, the development of liquid chromatography coupled with mass spectroscopy (LC-MS) has provided the ability to simultaneously identify low concentration
toxins as well as novel marine phycotoxins (Hummert et al. 2002; Zhang and Zhang 2015).
14.8 Lingering questions
As described above, the rapid evolution of omics technologies and increasingly sensitive/
high-throughput mass spectroscopy has advanced our capability to examine in ultra-fine
scale both the presence of potentially deleterious compounds as well as their negative
effects. However, connecting the presence of toxins or toxicants to individual health status