Accumulation of lead, copper and zinc ions by tissues of two freshwater fishes of different adaptations : the herbivorous cichlid Tilapia nilotica L. and a scavenger catfish Clarias lazera

Abstract EN

Accumulation of aquatic lead, copper and zinc ions was investigated in the tissues of two freshwater fishes: The herbivorous cichlid Tilapia nilotica L.

and the siluroid Clarias lazera C.

& V.

following exposure of the fish to an elevated metal ion concentration (150g/l for 48h).

Tissues of the hepatopancreas, spleen, heart, liver and kidneys exhibited higher levels of metal accumulation (6-12 folds) particularly for lead ions, and in tissues of C.

lazera than in corresponding tissues of T.

nilotica.

In both species, the highest values recorded for the tissue content of lead were in the heart (Clarias: 71.00 ±5.40 ug /g; Tilapia: 54.1913.85 ug /g) and the hepatopancreas (Clanias : 65.5712.90; Tilapia: 59.5314.78 ug /g).

The findings may be attributed to the relative lymphoid tissue content of the organs and to other adaptations that may affect the accessibilty of the absorptive and accumulative mechanisms to the metal ions.