1. Introduction
Pollution of the marine ecosystem by toxic metals
like nickel, chromium, cadmium, mercury, lead, etc., is
widespread. Metals after entering the water may precip-
itate or adsorb on the surface of solids, remain soluble
or suspended in it or may be taken up by fauna and
ora. Numerous studies have been carried out to assess
freshwater pollution by the discharge of e uents from
industries [1, 2]. The accumulation of heavy metals in
water suggests that sh may serve as a useful indicator
for contaminating metals in aquatic systems. Since shes
are often the last link in the aquatic food chain, the metal
concentration of many sh species has been analyzed in
relation to the metal content of aquatic environment [3].
Bone is formed by the infusion of an organic matrix,
principally of collagen, and with calcium phosphate and
it gives rigidity so that the tissue can ful ll its support-
ive and protective functions and provide movement. Sec-
ondly, bone minerals are in metabolic interrelation with
body uids, serving principally as a reservoir for many
of the ionic constituents of the body mineral [4], storing
or releasing them as need arises. It is known that there
is a close relationship between the low Ca:PO4 ratio and
the corresponding increase in apparent HPO4 content,
the high content of tightly bound water, and the low de-
gree of crystallinity. Diseased/immature bone is thought
to contain more ACP, having low Ca:PO4 ratio and a
low degree of crystallinity than the mature bone. Hence
the determination of the exact chemical composition and
crystallographic structure of the bone mineral play an
important role.
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Bioconcentration of chemicals in aquatic biota is an im-
portant factor in the assessment of the potential hazard
of chemicals to the environment [5]. Many researches are
done on toxicity of heavy metals [6, 7] on bioaccumula-
tion, its eects of protein contents [8] due to these heavy
metals and the in uence of pH and water hardness [9].
But only few researches are done on toxicity of heavy
metals on bone tissues of an edible sh. Hence keeping
in view of this the present study aims at toxicity study
of heavy metals nickel and chromium on bone tissues of
edible sh Cirrhinus mrigala.
