Chronic Sublethal Exposure Research Articles

Alterations in the oxygen consumption, condition index and concentration of free amino acids in Corbicula fluminea, (mollusca: Pelecypoda) exposed to sodium dodecyl sulfate

AbstractThe freshwater clam, Corbicula fluminea, was exposed during short‐ and long‐term toxicity tests to the anionic surfactant sodium dodecyl sulfate (SDS). Oxygen consumption, condition index, water content and the concentration of free amino acids (FAA) were measured in the clams after exposure. A significant increase in the total FAA concentration was measured in clams exposed for 96 h to 25 mg/L SDS. Exposure to sublethal concentrations (0.65 and 3.0 mg/L SDS) for 60 d caused both an increase in total FAA concentration and a change in the relative concentrations of individual amino acids. Sublethal chronic exposure also decreased oxygen consumption and condition index and increased water content. Alterations in FAA are a more sensitive indicator of toxicant exposure than more traditional measures such as respiration. The potential use of FAA as an in situ biochemical indicator of toxicant‐induced stress in freshwater invertebrates is discussed.

Low-salinity stress in the American lobster,Homarus americanus, after chronic sublethal exposure to cadmium: Biochemical effects

Lobsters(Homarus americanus) were exposed to cadmium (6µg l−1, 30 days) in flowing seawater, then held for 7 days in aerated “clean ” seawater at either ambient (27 ‰) or low (17 ‰) salinity. Cadmium exposure alone (ambient salinity) induced a general elevation of enzyme activity (heart, antennal gland, and muscle MDH; heart LDH and GPI), despite the probability of some clearance of cadmium from body tissues during the “clean ” seawater holding period. Low-salinity alone (non-exposed lobsters) caused a decrease of enzyme activity (AAT, LDH, GPI, PK) in most tissues examined, except for tail muscle IDH, the activity of which was increased, and MDH, which was significantly elevated above ambient controls in all tissues except heart. Most low-salinity effects were observed in tail muscle, and most cadmium effects, in heart; low-salinity effects outnumbered cadmium stress by nine to four. In heart and tail muscle of cadmium-exposed lobsters held at low salinity, each of the two stresses apparently operated to nullify the other's effects. The most prominent single biochemical response to these sublethal stresses was the elevation of MDH activity. The ratio MDH: LDH gave the clearest indication of overall relative stress.

Tissue uptake of cadmium in brook trout during chronic sublethal exposure.

Brook trout exposed to one ppb Cd; added as cadmium chloride in the holding water, accumulated the metal in the gills, kidneys, and livers with time. The greatest uptake was in the gills and posterior kidneys which showed similar accumulation patterns (r=0.99 and 0.94 respectively) with an exposure time of 93 days. Cd levels in the posterior kidneys were always higher than those in the anterior (head) kidneys in both Cd-exposed and the control fish. The Cd content in the gills and posterior kidneys in both the control and Cd-exposed fish was much higher than in the other tissues, and the levels in the muscle of the exposed fish were generally about three-fold higher than those found in the controls, but they remained low (0.030±0.014 ppm). The Cd content of the whole blood and plasma, heart, spleen, testes, stomach and skin of the Cd-exposed fish after 77 and 93 days were higher than those of the control fish. Brook trout injected with 1 μg Cd/g body weight, intramuscularly (i.m.), once a week for 16 weeks also accumulated the metal, primarily in the posterior kidneys and gills, but there was less accumulation in the gills than in the fish exposed to one ppb Cd in water. Unlike the Cd-water study, a significant uptake of the metal occurred in the red cells, blood plasma, and muscle. No significant uptake occurred in the gonads. The red cells and gills had about the same Cd content (0.500–0.550 ppm), suggesting that much of the Cd in the gills may have come from the blood content, an observation which was not apparent in the fish that were exposed to Cd in the water. The results suggest that the gills and posterior kidneys were sensitive organs for testing the effects of chronic sublethal exposure of brook trout to Cd.

A long-term study of the effects of water-soluble fractions of No. 2 fuel oil on the survival, development rate, and growth of the mud crab Rhithropanopeus harrisii

Mud crabs, Rhithropanopeus harrisii (Gould), were exposed continuously for 6 months after hatching to water-soluble fractions (WSF) of No. 2 fuel oil. Survival, growth and development rate were monitored during this time. The zoeal stages were the most sensitive to fuel oil. A 20% WSF (0.36 ppm total naphthalenes, 1.26 ppm total hydrocarbons) was acutely toxic to these stages. Of the zoeal stages, the first stage appeared to be the most sensitive. The combined duration of the 4 zoeal stages was significantly increased by increasing WSF exposure concentrations. The megalopa and crab stages were not particularly sensitive to continued petroleum hydrocarbon exposure, particularly when compared to zoeal stages. However, mean duration of the megalopa and first crab stages was significantly affected by oil exposure. Individuals which survived the highest exposure concentrations as larvae appeared to grow larger during the crab stages, so that at the end of 6 months comparably staged crabs were equal to or larger than both control crabs and those exposed to low WSF concentrations. Stage distributions at the end of 6 months showed no differences due to WSF exposure. Sex ratios, which could be determined at the end of 6 months, were approximately 1, indicating no sex-related differential sensitivity to WSF exposure, at least as larvae or juveniles. The data indicate that these crabs possess considerable ability to recover from the effects of chronic sublethal exposure to petroleum hydrocarbons. The most deleterious effects of oil pollution on this species may be due to its impact on larval recruitment into the adult population.

Effects of No. 2 fuel oil water-soluble-fractions on growth and reproduction in Neanthes arenaceodentata (Polychaeta: annelida)

Effects of water-soluble-fractions (WSFs) from No. 2 Fuel Oil on growth and reproduction in a laboratory strain of Neanthes arenaceodentata were studied in experiments simulating conditions of acute and chronic sublethal exposure. Effects were defined relative to concentrations of diaromatic hydrocarbons (naphthalenes) and total dissolved hydrocarbons. Hatching of metatrochophore larvae was inversely related to WSF concentration and to the length of time larvae were exposed prior to hatching. Growth of larvae into juveniles was unaffected by low concentrations. Inhibition of larval growth by higher WSF concentrations was reversible upon return of larvae to hydrocarbon-free sea water. Growth of juveniles into adult polychaetes was inversely related to concentration. Rate of development to the feeding juvenile stage was not affected by WSF in three successive generations of continuously exposed polychaetes. Oocyte maturation rates in the four WSF concentrations (2.5, 5, 10, 2507o) increased with each successive generation. All concentrations suppressed fecundity in each generation. Survival to the 32-segment juvenile stage (brood mortality) was inversely related to concentration in first generation animals. Brood mortality in all WSF concentrations decreased with successive generations thereafter. Levels of naphthalenes in worms declined with each generation. Naphthalenes concentrations in third generation animals was very similar to those of exposure media.

Dieldrin. Effects of chronic sublethal exposure on adaptation to thermal stress in fresh water fish

Dieldrin. Effects of chronic sublethal exposure on adaptation to thermal stress in fresh water fish