Only one concentration comprised in the range of tens of μg L
À1 was assayed [19]
to evaluate if the compounds had an effect on a series of selected physiological
endpoints including feeding- and respiratory-related parameters that affect directly
the fitness of exposed organisms such as ingestion rate, osmoregulatory capacity,
and hemolymph osmolality.
At the concentrations tested, neither ingestion rate (exposed to 13.3 and
70.6 μg L
À1 DF and IB, respectively) nor osmoregulatory capacity and hemolymph
osmolality (exposed to 14.6 and 47.24 μg L
À1 DF and IB, respectively) were
statistically affected (Fig. 5). However, specific oxygen consumption showed a
decreasing respiratory independence trend for all treatments (Fig. 5c) within the
range of environmental oxygen concentration tested. The degree of respiratory
independence versus oxygen concentration indicated that a shrimp’s oxyregulation
increased from well-oxygenated water to moderate hypoxia and decreased under
severe hypoxic conditions. Specific oxygen consumption was not affected, but
shrimps exposed to DF showed lower respiration rates under severe hypoxic conditions (1 mg O 2 L
À1 ) allowing the assumption that DF reduces the respiration rate of
A. desmarestii under increasingly anoxic conditions that are more likely to occur
under a global change scenario.
Thus, the selected physiological endpoint ingestion rate, osmoregulatory capacity, and hemolymph osmolality seemed to not significantly affect A. desmarestii
when confronted with the selected exposure concentrations. Other crustaceans such
as the crab Carcinus maenas under similar exposure conditions do have shown
significant changes in osmoregulatory capacity and hemolymph osmolality after
exposure to only 10 ng L
À1 of DF and 17.5 psu of salinity [86]. Namely, DF
produced an increased osmoregulatory capacity, suggesting an ability of these
organisms to compensate for adverse osmotic conditions and an increase in hemolymph osmolality due to the impairment of its osmo- and iono-regulatory ability.
5.2 Case Study: Acute and Sublethal Toxicity of DF
in the Shrimp Palaemon longirostris and Palaemon
serratus
When looking at the joint action of salinity and temperature changes combined with
exposure to environmentally relevant concentrations of DF (40 and 750 μg L
À1 ) on
the selected endpoint survival, development, and growth of exposed larvae of the
shrimps Palaemon longirostris and Palaemon serratus, González-Ortegón et al. [87]
observed no effect on larval survival, development, and growth. However, a slight
but significant interactive effect of salinity and pharmaceutical on intermolt duration
was reported. However, in combination with another pharmaceutical compound,
clofibric acid, a metabolite of the cholesterol-lowering pharmaceutical drug clofibrate as well as a commercially available herbicide, DF, showed to increase duration
of development for 6 days at the higher exposure concentration tested. Thus,
although DF alone did not produce effects on the examined sublethal endpoints,
176
C. Trombini et al.
À1 was assayed [19]
to evaluate if the compounds had an effect on a series of selected physiological
endpoints including feeding- and respiratory-related parameters that affect directly
the fitness of exposed organisms such as ingestion rate, osmoregulatory capacity,
and hemolymph osmolality.
At the concentrations tested, neither ingestion rate (exposed to 13.3 and
70.6 μg L
À1 DF and IB, respectively) nor osmoregulatory capacity and hemolymph
osmolality (exposed to 14.6 and 47.24 μg L
À1 DF and IB, respectively) were
statistically affected (Fig. 5). However, specific oxygen consumption showed a
decreasing respiratory independence trend for all treatments (Fig. 5c) within the
range of environmental oxygen concentration tested. The degree of respiratory
independence versus oxygen concentration indicated that a shrimp’s oxyregulation
increased from well-oxygenated water to moderate hypoxia and decreased under
severe hypoxic conditions. Specific oxygen consumption was not affected, but
shrimps exposed to DF showed lower respiration rates under severe hypoxic conditions (1 mg O 2 L
À1 ) allowing the assumption that DF reduces the respiration rate of
A. desmarestii under increasingly anoxic conditions that are more likely to occur
under a global change scenario.
Thus, the selected physiological endpoint ingestion rate, osmoregulatory capacity, and hemolymph osmolality seemed to not significantly affect A. desmarestii
when confronted with the selected exposure concentrations. Other crustaceans such
as the crab Carcinus maenas under similar exposure conditions do have shown
significant changes in osmoregulatory capacity and hemolymph osmolality after
exposure to only 10 ng L
À1 of DF and 17.5 psu of salinity [86]. Namely, DF
produced an increased osmoregulatory capacity, suggesting an ability of these
organisms to compensate for adverse osmotic conditions and an increase in hemolymph osmolality due to the impairment of its osmo- and iono-regulatory ability.
5.2 Case Study: Acute and Sublethal Toxicity of DF
in the Shrimp Palaemon longirostris and Palaemon
serratus
When looking at the joint action of salinity and temperature changes combined with
exposure to environmentally relevant concentrations of DF (40 and 750 μg L
À1 ) on
the selected endpoint survival, development, and growth of exposed larvae of the
shrimps Palaemon longirostris and Palaemon serratus, González-Ortegón et al. [87]
observed no effect on larval survival, development, and growth. However, a slight
but significant interactive effect of salinity and pharmaceutical on intermolt duration
was reported. However, in combination with another pharmaceutical compound,
clofibric acid, a metabolite of the cholesterol-lowering pharmaceutical drug clofibrate as well as a commercially available herbicide, DF, showed to increase duration
of development for 6 days at the higher exposure concentration tested. Thus,
although DF alone did not produce effects on the examined sublethal endpoints,
176
C. Trombini et al.