No abstract

Eggs collected from adult Japanese Medaka were incubated for 16 days in solutions containing 10, 15, 20, and 30 ppb mercury as mercuric chloride. The mean hatchability of control eggs was 46.7 percent. Experimental eggs incubated in 10 ppb and 15 ppb mercury had hatching percentages of 58.3 and 20.8 respectively (Chi Square = 12.8, Pless than.0005). None of the 20 ppb or 30 ppb experimental eggs hatched. Nemorrhaging, blood vessel deterioration and loss of blood cells were observed in 79 percent of the 15 ppb experimental eggs and all the 20 and 30 ppb experimental eggs. Neither the control nor the 10 ppb experimental eggs demonstrated any of these abnormalities. The LC100 for 384 hours was between 20 ppb and 30 ppb. The 10, 15, 20 and 30 ppb experimental eggs concentrated mercury directly from the incubating solution 1,600, 1,900, 2,700, and 1,900 times, respectively. The total concentration of mercury in these eggs after 16 consecutive days was 16,000, 29,000, 54,000, and 56,000 respectively.

No abstract

We found selenium dixoide an effective antagonist to the toxic effects of mercuric chloride in the northern creek chub (Semotilus atromaculatus). Selenium pretreatment increased the whole body accumulation of mercury at lower environmental Hg concentrations. It decreased mercury accumulation in survivors at higher, acutely toxic concentrations.

No abstract

Abstract-Acute toxicity tests were conducted with Hyalella azteca Saussure (an amphipod) exposed in soft and hard waters to three fire retardants (Fire-Trol GTS-R, Fire-Trol LCG-R, and Phos-Chek D75-F) and two foam suppressants (Phos-Chek WD-881 and Silv-Ex). The chemicals were slightly to moderately toxic to amphipods. The most toxic chemical to amphipods in soft and hard water was Phos-Chek WD-881 (96-h mean lethal concentration [LC50] equal to 10 mg/L and 22 mg/L, respectively), and the least toxic chemical to amphipods in soft water was Fire-Trol GTS-R (96-h LC50 equal to 127 mg/L) and in hard water was FireTrol LCG-R (96-h LC50 equal to 535 mg/L). Concentrations of ammonia in tests with the three fire retardants and both water types were greater than reported LC50 values and probably were the major toxic component. Estimated un-ionized ammonia concentrations near the LC50 were frequently less than the reported LC50 ammonia concentrations for amphipods. The three fire retardants were more toxic in soft water than in hard water even though ammonia and un-ionized ammonia concentrations were higher in hard water tests than in soft water tests. The accidental entry of fire-fighting chemicals into aquatic environments could adversely affect aquatic invertebrates, thereby disrupting ecosystem function.

No abstract

Reingestion in caged cottontails occurs as a well—synchronized diel rhythm coinciding with or following sunrise. On a reversed lighting regimen rabbits slowly adjust their rhythmic functions so that reingestion is closely fixed to the light time. When they are exposed to sunlight the relationship between the onset of reingestion and sunrise differs during the seasons. As the days become longer reingestion begins later in the morning. This daily and seasonal relationship appears to follow very closely the condition found in unconfined populations. A gastrocolic reflex appears to govern the rate of hard pellet defecation, but another answer apparently must be found to explain the cyclic production of soft feces. The transition from soft feces to hard pellets occurs previous to and is independent of the evening feeding activity. If rabbits are not allowed to feed in the evening a second period of reingestion occurs, at least in some animals.