TOXIC EFFECTS OF SUBLETHAL CONCENTRATIONS OF LEAD ON Tilapia nilotica(Linnaeus
TOXIC EFFECTS OF SUBLETHAL CONCENTRATIONS OF LEAD ON Tilapia nilotica(Linnaeus
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Date
1985-10
Authors
RUFUS, OLOGUNMETA TAYO
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Abstract
Toxic effects of sublethal concentrations of lead
was observed on fingerling Tilapia nilotica(L) of size
range 12-14.5cm total length, caught from Maska and
Maigana fish farms, located at kilometer I4.5 and 25 along
Zaria - Funtua and Zaria - Jos roads in Kaduna State
of Nigeria respectively.
Effects of lead on the growth, haemoglobin,
haematocrit, blood serum protein, red cell morphology,
liver and skeletal muscle glycogen and liver histology
were observed in fish exposed to lead concentrations
of O.o76, 0.163 and O.326 mgL-1(76, 163 and 326 ugl-1
respectively) for a period of six weeks in a static assay.
The experiment was replicated once and the pooled values
presented. Residues of lead in test fish were also •
determined with Atomic Absorption Spectrophotometer.
The study indicate that sublethal concentrations
of lead caused a dose-dependent inpairment in the growth
of Tilapia nilotica. The percent weight increase after
six weeks were 27.73, 27.11, 23.38 and 20.00 for control,
0.076, 0.163 and O.326 mgL-1 group respectively. The
growth rates in the lead-exposed groups were not
significantly (p> 0.05) different from that for the
control. Growth impairment is attributed to lead
interference with energy metabolism in cells mitochondria
The values for heamoglobin, haematocrit blood serum
protein and liver glycogen in fish exposed to the various
concentrations of lead dropped considerably slightly below
those for the control. No effect of lead on skeletal
muscle glycogen was however observed.
iv
'Blacktail' and 'blackhead' lesions were observed
in 40% of fish exposed to 0.163 mgL-1 lead after five
and six weeks respectively. This was attributed to
a probable neurological lead effect or biochemical
metabolic inhibition. This observation is in agreement
with the occurence of blacktail in lead concentration
0.12 mgL-1 for rainbow trout Salmo gairdueri as reported
by Davies et al(l976), Hodson et al(l978), (1982), and
Alen et al (1983).
Tilapia nilotica accumulated lead concentration
up to a level of 8.75 ugg-1 tissue after exposure to
0.326 mgL" lead for six weeks.
The livers of test fish exposed to all lead
concentrations used in this study degenerated on
histological observation, due to the preapitation of
the hepatocytes cytoplasm and disintegration of blood
vessels.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL,
AHMADU BELLO UNIVERSITY IN PARTIAL FULFILMENT OF
THE REQUIREMENTS FOR THE DEGREE OF MASTER OF
SCIENCE IN EDUCATIONAL - BIOLOGY.
DEPARTMENT OF BIOLOGICAL SCIENCES,
FACULTY OF SCIENCE
AHMADU BELLO UNIVERSITY
ZARIA
OCTOBER 1985
Keywords
TOXIC EFFECTS,, SUBLETHAL,, CONCENTRATIONS,, LEAD,, Tilapia,, nilotica(Linnaeus)