Life span and fecundity of Aiolopus thalassinus exposed to dietary heavy metals (Hg, Cd, Pb)

Abstract

Aialapus thalassinus (Fabr. 1781) (Orthopteroidea, Caelifera Acrididae)
from Kenya was reared and fed with wheat seedlings grown in water contaminated
by different heavy metal salts. Additionally, the egg-laying substrate was
contaminated.
The effects of dietary heavy metals (Hg, Cd, Pb) on the life span and fecundity
of A. thalassinus were studied. The life span of A. thalassinus kept on Hg, Cd
and Pb contaminated food was shorter than that of control grasshoppers, where
Hg showed the highest effect, followed by Pb and Cd. Females exposed to Hg
and Pb had significantly shorter life spans than those exposed to Cd. Differences
in the life span between the female and male within the same exposure was significant
only during exposure to cadmium. The accumulation to Hg was propotional
to the life span in both sexes, as it increased steadily with the age. The concentration
factors were in the order Hg > Cd > Pb. Cadmium accumulation in both
sexes increased during the maturing phase (first 8-10 days of adult stage), but it
decreased steadily when the individuals became older. Decontamination of Cd
was faster and greater in males than in females. Bioaccumulation of Pb in the
grasshoppers was significantly lower than in food.
Dietary Hg reduced the fecundity, whereas females exposed to Cd laid more eggs
and egg pods than in control. The effect of dietary Pb was not as negative as that
of Hg. The females during Hg exposure required 4.21 days for one oviposition,
on the average, whereas those exposed to Cd and Pb contaminated food oviposited
in shorter intervals, 3.17 and 3.26 days. respectively. A higher number of
egg pods was deposited in substrates containing higher concentrations of metal
salts. Higher number of eggs per female per day and more frequent oviposition
were accompanied by decreasing Cd concentration in the female. The life span
of such individuals were longer than those exposed to Hg and Pb.