O'HARA: TOXICITY OF CADMIUM TO FIDDLER CRABS 



150 



a. 



Q. 100 



Z 



S 50 



a 

 < 



hepolopancreas 



gill 



12 24 36 48 60 



TIME IN HOURS 



Figure 1. — Concentration of cadmium in gill and he- 

 patopancreas of crabs in 5, 15 and 25 ppm Cd^"^ at 30°C, 

 20%.. 



to 15 ppm Cd^^ contained 59 ppm, while such 

 tissue from those exposed to 5 ppm Cd"^"^ con- 

 tained 18 ppm. Each accumulation in gill tissue 

 was about four times the concentration of cad- 

 mium in the surrounding water. 



Gill tissues from crabs in 25 ppm Cd^^ did not 

 increase their cadmium concentration apprecia- 

 bly over 110 ppm in 24 hr and exhibited a de- 

 cline in tissue concentration at 36 hr. The large 

 mortality rate at 48 hr prevented reliable sam- 

 ples from being obtained. Gill tissue from crabs 

 exposed to 15 ppm Cd^^ showed an increase in 

 cadmium content between 24 and 48 hr with a 

 maximum accumulation of 109 ppm. The sig- 

 nificance of the value around 110 ppm is unclear, 

 but may represent a maximum tissue burden in 

 terms of equilibrium with the external medium. 

 The cadmium concentration in gill tissues from 

 crabs sacrificed at 60 hr showed a marked re- 

 duction in cadmium content. Considering the 

 large mortality of crabs in this concentration, 

 the lower cadmium content in the tissues prob- 

 ably represents a reduced binding of the metal 

 due to the destruction of tissue. 



Crabs exposed to 5 ppm Cd^"" continually con- 

 centrated cadmium in their gill tissue with a 

 maximum of 39 ppm after 60 hr. No mortality 

 occurred in this concentration, and only one an- 

 imal died during this period in the acute toxicity 

 tests. Significant mortality occurred only after 

 96 hr. 



Hepatopancreas 



The hepatopancreas from crabs in the diflfer- 

 ent cadmium solutions concentrated cadmium 

 about two times exposure level in 12 hr (25 ppm 

 was concentrated to 50 ppm in tissue, 15 to 

 32 ppm in tissue, and 5 to 11 ppm in tissue). 

 The hepatopancreas tissue in crabs exposed to 

 the highest concentration was almost completely 

 destroyed after 24 hr and precluded samples 

 from these crabs (Figure 1). The hepatopan- 

 creas was changed from a firm glandular tissue 

 to an amorphous and liquified condition. Crabs 

 exposed to 15 ppm Cd""^ showed an increase in 

 cadmium levels to about 116 ppm in 48 hr, fol- 

 lowed by a rapid decline. This decline might be 

 associated with the destruction of the hepato- 

 pancreas tissue. Crabs exposed to water con- 

 taining 5 ppm showed the same general increase 

 in Cd"""^ concentration that was evident in gill 

 tissue with a maximum of 24 ppm after 60 hr. 



Green Gland 



The bioaccumulation was highest in the green 

 gland tissue (Figure 2) with maximum concen- 

 trations of 380 ppm in tissue from crabs exposed 

 to 25 ppm, 171 ppm from crabs in 15 ppm, and 

 118 ppm from crabs in 5 ppm. These values 

 are 12 to 20 times the exposure concentrations. 



s 3 



a. 

 a. 



Z 



2 



i 



a 



< 100 



u 



24 36 



TIME IN HOURS 



Figure 2. — Concentration of cadmium in green gland 

 tissue of crabs in 5, 15 and 25 ppm Cd"'* at 30°C, 20%«.. 



151 



