500
sensitivity within and among species, likely because size dictates metabolic demands
and thereby needs for exchange of gasses and metabolic products as well as surface
area/volume ratios (Bianchini et al. 2002; Grosell et al. 2002). The general relationship of smaller early life stage organisms being more sensitive than older and larger
conspecifics holds true also for oil/PAH exposures as illustrated in the following.
However, it is important to note that impacts to several endpoints, such as sensory
function, aerobic scope, and reproduction, cannot be assessed in early life stages
and that these endpoints in some cases appear highly sensitive (Stieglitz et al. 2016;
Xu et al. 2018; Johansen and Esbaugh 2017) and very well may be of relevance for
population-level impacts. Further, several studies have revealed that early life stage
exposures may lead to effects that are not readily evident until later in life (Xu et al.
2018; Mager et al. 2014; Magnuson et al. 2018) underscoring the importance for
studies also on later life stages.
29.3 Targets of Oil Toxicity
29.3.1 Cardiac Developmental and Functional Effects on ELS
Cardiac development and function in embryo and larval fish from the GoM have
been demonstrated to be sensitive to crude oil exposure. The early life stages (ELS)
of yellowfin tuna (Thunnus albacares) were found to display pericardial edema and
reduced heart rate following 48 hrs of exposure to HEWAFs at EC50 concentrations
of 2.5 and 7.5 μg/L∑50PAH, respectively (Incardona et al. 2014). Similarly sensitive are mahi-mahi (Coryphaena hippurus) embryos and larvae with 48-hr EC50s
ranging from >5.1 to 7.3 μg/L∑50PAH for HEWAFs and 11.3 to 13.0 μg/L∑50PAH
for CEWAFs of slick, source, and weathered oil (Esbaugh et al. 2016). As with yellowfin tuna, mahi-mahi displayed pericardial edema but also presented an altered
atrium-ventricle angle and evidence of reduced cardiac contractility (Edmunds et al.
2015), the later suggesting reduced stroke volume. The coastal red drum is no less
sensitive with a pericardial edema 48-h EC50 of 2.4 μg/L∑50PAH for HEWAF
(Khursigara et al. 2017). For the first time in any oil-exposed fish ELS, red drum
stroke volume was measured to reveal that this parameter is far more sensitive than
heart rate with the two factors both contributing to cardiac output with a 48-h EC50
of 2.2 μg/L∑50PAH for HEWAF (Khursigara et al. 2017). While the aryl hydrocarbon receptor (AhR) plays a role in the pericardial edema phenotype (Incardona
et al. 2006, 2011) observed in ELS fish following oil exposure, AhR-independent
effects have also been reported (Incardona et al. 2005). In mahi-mahi, as well as red
drum, pathway analyses of RNA-seq experiments revealed cardiac Ca
2+
homeostasis as a target for crude oil toxicity (Xu et al. 2016, 2017a, b). Impaired Ca
2+
homeostasis in myocytes may certainly account for observations of reduced cardiac
contractility and stroke volume (Edmunds et al. 2015; Khursigara et al. 2017) and
has also been implicated in cardiac hypertrophy (Xu et al. 2017b).
M. Grosell et al.
sensitivity within and among species, likely because size dictates metabolic demands
and thereby needs for exchange of gasses and metabolic products as well as surface
area/volume ratios (Bianchini et al. 2002; Grosell et al. 2002). The general relationship of smaller early life stage organisms being more sensitive than older and larger
conspecifics holds true also for oil/PAH exposures as illustrated in the following.
However, it is important to note that impacts to several endpoints, such as sensory
function, aerobic scope, and reproduction, cannot be assessed in early life stages
and that these endpoints in some cases appear highly sensitive (Stieglitz et al. 2016;
Xu et al. 2018; Johansen and Esbaugh 2017) and very well may be of relevance for
population-level impacts. Further, several studies have revealed that early life stage
exposures may lead to effects that are not readily evident until later in life (Xu et al.
2018; Mager et al. 2014; Magnuson et al. 2018) underscoring the importance for
studies also on later life stages.
29.3 Targets of Oil Toxicity
29.3.1 Cardiac Developmental and Functional Effects on ELS
Cardiac development and function in embryo and larval fish from the GoM have
been demonstrated to be sensitive to crude oil exposure. The early life stages (ELS)
of yellowfin tuna (Thunnus albacares) were found to display pericardial edema and
reduced heart rate following 48 hrs of exposure to HEWAFs at EC50 concentrations
of 2.5 and 7.5 μg/L∑50PAH, respectively (Incardona et al. 2014). Similarly sensitive are mahi-mahi (Coryphaena hippurus) embryos and larvae with 48-hr EC50s
ranging from >5.1 to 7.3 μg/L∑50PAH for HEWAFs and 11.3 to 13.0 μg/L∑50PAH
for CEWAFs of slick, source, and weathered oil (Esbaugh et al. 2016). As with yellowfin tuna, mahi-mahi displayed pericardial edema but also presented an altered
atrium-ventricle angle and evidence of reduced cardiac contractility (Edmunds et al.
2015), the later suggesting reduced stroke volume. The coastal red drum is no less
sensitive with a pericardial edema 48-h EC50 of 2.4 μg/L∑50PAH for HEWAF
(Khursigara et al. 2017). For the first time in any oil-exposed fish ELS, red drum
stroke volume was measured to reveal that this parameter is far more sensitive than
heart rate with the two factors both contributing to cardiac output with a 48-h EC50
of 2.2 μg/L∑50PAH for HEWAF (Khursigara et al. 2017). While the aryl hydrocarbon receptor (AhR) plays a role in the pericardial edema phenotype (Incardona
et al. 2006, 2011) observed in ELS fish following oil exposure, AhR-independent
effects have also been reported (Incardona et al. 2005). In mahi-mahi, as well as red
drum, pathway analyses of RNA-seq experiments revealed cardiac Ca
2+
homeostasis as a target for crude oil toxicity (Xu et al. 2016, 2017a, b). Impaired Ca
2+
homeostasis in myocytes may certainly account for observations of reduced cardiac
contractility and stroke volume (Edmunds et al. 2015; Khursigara et al. 2017) and
has also been implicated in cardiac hypertrophy (Xu et al. 2017b).
M. Grosell et al.